Hypothalamus

Development

The hypothalamus is a collection of various nuclei within the center of the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification that develops early during embryologic life.

Neural tube Neural tube A tube of ectodermal tissue in an embryo that will give rise to the central nervous system, including the spinal cord and the brain. Lumen within the neural tube is called neural canal which gives rise to the central canal of the spinal cord and the ventricles of the brain. Gastrulation and Neurulation

The 1st step is development of the neural tube Neural tube A tube of ectodermal tissue in an embryo that will give rise to the central nervous system, including the spinal cord and the brain. Lumen within the neural tube is called neural canal which gives rise to the central canal of the spinal cord and the ventricles of the brain. Gastrulation and Neurulation.

• Develops from ectoderm Ectoderm The outer of the three germ layers of an embryo. Gastrulation and Neurulation 
• Trilaminar embryo Embryo The entity of a developing mammal, generally from the cleavage of a zygote to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the fetus. Fertilization and First Week invaginates to form the neural fold → neural tube Neural tube A tube of ectodermal tissue in an embryo that will give rise to the central nervous system, including the spinal cord and the brain. Lumen within the neural tube is called neural canal which gives rise to the central canal of the spinal cord and the ventricles of the brain. Gastrulation and Neurulation (closed by 6 weeks)
• Neural tube Neural tube A tube of ectodermal tissue in an embryo that will give rise to the central nervous system, including the spinal cord and the brain. Lumen within the neural tube is called neural canal which gives rise to the central canal of the spinal cord and the ventricles of the brain. Gastrulation and Neurulation becomes the CNS.

Primary and secondary neural vesicles Vesicles Female Genitourinary Examination

The neural tube Neural tube A tube of ectodermal tissue in an embryo that will give rise to the central nervous system, including the spinal cord and the brain. Lumen within the neural tube is called neural canal which gives rise to the central canal of the spinal cord and the ventricles of the brain. Gastrulation and Neurulation develops 3 “bulges” known as the primary vesicles Vesicles Female Genitourinary Examination:

• Prosencephalon Prosencephalon The anterior of the three primitive cerebral vesicles of the embryonic brain arising from the neural tube. It subdivides to form diencephalon and telencephalon. Development of the Nervous System and Face ( forebrain forebrain The anterior of the three primitive cerebral vesicles of the embryonic brain arising from the neural tube. It subdivides to form diencephalon and telencephalon. Development of the Nervous System and Face) → splits into 2 secondary vesicles Vesicles Female Genitourinary Examination:
  • Telencephalon Telencephalon The anterior subdivision of the embryonic prosencephalon or the corresponding part of the adult prosencephalon that includes the cerebrum and associated structures. Development of the Nervous System and Face → cerebrum
  • Diencephalon Diencephalon The paired caudal parts of the prosencephalon from which the thalamus; hypothalamus; epithalamus; and subthalamus are derived. Development of the Nervous System and Face goes on to form:
    • Thalamus Thalamus The thalamus is a large, ovoid structure in the dorsal part of the diencephalon that is located between the cerebral cortex and midbrain. It consists of several interconnected nuclei of grey matter separated by the laminae of white matter. The thalamus is the main conductor of information that passes between the cerebral cortex and the periphery, spinal cord, or brain stem. Thalamus: Anatomy
    • Hypothalamus
    • Epithalamus (includes the pineal gland Pineal gland A light-sensitive neuroendocrine organ attached to the roof of the third ventricle of the brain. The pineal gland secretes melatonin, other biogenic amines and neuropeptides. Hormones: Overview and Types)
    • Subthalamus
• Mesencephalon Mesencephalon Development of the Nervous System and Face ( midbrain Midbrain The middle of the three primitive cerebral vesicles of the embryonic brain. Without further subdivision, midbrain develops into a short, constricted portion connecting the pons and the diencephalon. Midbrain contains two major parts, the dorsal tectum mesencephali and the ventral tegmentum mesencephali, housing components of auditory, visual, and other sensorimotor systems. Brain Stem: Anatomy, no secondary vesicles Vesicles Female Genitourinary Examination) → midbrain Midbrain The middle of the three primitive cerebral vesicles of the embryonic brain. Without further subdivision, midbrain develops into a short, constricted portion connecting the pons and the diencephalon. Midbrain contains two major parts, the dorsal tectum mesencephali and the ventral tegmentum mesencephali, housing components of auditory, visual, and other sensorimotor systems. Brain Stem: Anatomy
• Rhombencephalon Rhombencephalon The posterior of the three primitive cerebral vesicles of an embryonic brain. It consists of myelencephalon, metencephalon, and isthmus rhombencephalon from which develop the major brain stem components, such as medulla oblongata from the myelencephalon, cerebellum and pons from the metencephalon, with the expanded cavity forming the fourth ventricle. Development of the Nervous System and Face (hindbrain) → splits into 2 secondary vesicles Vesicles Female Genitourinary Examination:
  • Metencephalon Metencephalon The anterior portion of the developing hindbrain. It gives rise to the cerebellum and the pons. Development of the Nervous System and Face:
    • Pons Pons The front part of the hindbrain (rhombencephalon) that lies between the medulla and the midbrain (mesencephalon) ventral to the cerebellum. It is composed of two parts, the dorsal and the ventral. The pons serves as a relay station for neural pathways between the cerebellum to the cerebrum. Brain Stem: Anatomy
    • Cerebellum Cerebellum The cerebellum, Latin for “little brain,” is located in the posterior cranial fossa, dorsal to the pons and midbrain, and its principal role is in the coordination of movements. The cerebellum consists of 3 lobes on either side of its 2 hemispheres and is connected in the middle by the vermis. Cerebellum: Anatomy
  • Myelencephalon Myelencephalon The most posterior portion of the hindbrain from which medulla oblongata is derived. Development of the Nervous System and Face → medulla oblongata Medulla Oblongata The lower portion of the brain stem. It is inferior to the pons and anterior to the cerebellum. Medulla oblongata serves as a relay station between the brain and the spinal cord, and contains centers for regulating respiratory, vasomotor, cardiac, and reflex activities. Brain Stem: Anatomy

Gross Anatomy

Location

• Located in the center of the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification
• Just superior to the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification stem
• Forms part of the walls and floor of the 3rd ventricle
• Symmetrical Symmetrical Dermatologic Examination; has right and left halves

Boundaries

Parasagittal zones

Each ½ of the hypothalamus contain 3 primary zones or areas (from lateral to medial):

• Lateral hypothalamic area: diffuse fiber systems
• Medial hypothalamic area: contains the defined nuclei
• Periventricular gray zone: immediately adjacent to the 3rd ventricle

Rostrocaudal levels

The hypothalamus can also be divided into 4 primary levels, moving from anterior (rostral) to posterior (caudal). These levels describe the locations of different functional nuclei within the hypothalamus (all of which are in the medial hypothalamic area). The levels include:

1. Preoptic: found between the optic chiasm Optic Chiasm The x-shaped structure formed by the meeting of the two optic nerves. At the optic chiasm the fibers from the medial part of each retina cross to project to the other side of the brain while the lateral retinal fibers continue on the same side. As a result each half of the brain receives information about the contralateral visual field from both eyes. The Visual Pathway and Related Disorders and the anterior commissure:
   • Lateral preoptic area
   • Medial preoptic area
2. Supraoptic: anteriormost level behind the preoptic area:
   • Paraventricular nucleus Paraventricular nucleus Nucleus in the anterior part of the hypothalamus. Adrenal Hormones
   • Anterior nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles
   • Supraoptic nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles
   • Suprachiasmatic nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles
3. Tuberal: between the supraoptic and mammillary levels:
   • Lateral hypothalamus
   • Dorsomedial nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles
   • Ventromedial nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles
   • Arcuate nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles
4. Mammillary: posterior most (caudal) level:
   • Posterior nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles
   • Mammillary bodies Mammillary bodies A pair of nuclei and associated gray matter in the interpeduncular space rostral to the posterior perforated substance in the posterior hypothalamus. Limbic System: Anatomy

Neurovasculature

The hypothalamus is a major coordinating center within the body. It receives information and can exert its effects via nerves, blood, and CSF.

Afferent Afferent Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology nerve connections of the hypothalamus

The hypothalamus gets afferent Afferent Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology input from:

• Somatic nerves
• Visceral nerves 
• Visual/optic nerves 
• Olfactory nerves
• Cerebral cortex Cerebral cortex The cerebral cortex is the largest and most developed part of the human brain and CNS. Occupying the upper part of the cranial cavity, the cerebral cortex has 4 lobes and is divided into 2 hemispheres that are joined centrally by the corpus callosum. Cerebral Cortex: Anatomy
• Hippocampus (via the fornix Fornix Vagina, Vulva, and Pelvic Floor: Anatomy)
• Amygdala Amygdala Almond-shaped group of basal nuclei anterior to the inferior horn of the lateral ventricle of the temporal lobe. The amygdala is part of the limbic system. Limbic System: Anatomy (via the stria terminalis)
• Thalamus Thalamus The thalamus is a large, ovoid structure in the dorsal part of the diencephalon that is located between the cerebral cortex and midbrain. It consists of several interconnected nuclei of grey matter separated by the laminae of white matter. The thalamus is the main conductor of information that passes between the cerebral cortex and the periphery, spinal cord, or brain stem. Thalamus: Anatomy
• Other nuclei within the hypothalamus

Efferent Efferent Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology nerve connections of the hypothalamus

The hypothalamus sends efferent Efferent Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology signals to:

• Descending fibers in the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification stem and spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord: Anatomy → affect peripheral autonomic nervous system Autonomic nervous system The ANS is a component of the peripheral nervous system that uses both afferent (sensory) and efferent (effector) neurons, which control the functioning of the internal organs and involuntary processes via connections with the CNS. The ANS consists of the sympathetic and parasympathetic nervous systems. Autonomic Nervous System: Anatomy:
  • Vagus nerve Vagus nerve The 10th cranial nerve. The vagus is a mixed nerve which contains somatic afferents (from skin in back of the ear and the external auditory meatus), visceral afferents (from the pharynx, larynx, thorax, and abdomen), parasympathetic efferents (to the thorax and abdomen), and efferents to striated muscle (of the larynx and pharynx). Pharynx: Anatomy
  • Sympathetic preganglionic neurons Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the nervous system. Nervous System: Histology
• Mammillothalamic tract: mammillary body → thalamus Thalamus The thalamus is a large, ovoid structure in the dorsal part of the diencephalon that is located between the cerebral cortex and midbrain. It consists of several interconnected nuclei of grey matter separated by the laminae of white matter. The thalamus is the main conductor of information that passes between the cerebral cortex and the periphery, spinal cord, or brain stem. Thalamus: Anatomy
• Mammillotegmental tract: mammillary body → tegmentum of the midbrain Midbrain The middle of the three primitive cerebral vesicles of the embryonic brain. Without further subdivision, midbrain develops into a short, constricted portion connecting the pons and the diencephalon. Midbrain contains two major parts, the dorsal tectum mesencephali and the ventral tegmentum mesencephali, housing components of auditory, visual, and other sensorimotor systems. Brain Stem: Anatomy ( brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification stem)
• Limbic system Limbic system The limbic system is a neuronal network that mediates emotion and motivation, while also playing a role in learning and memory. The extended neural network is vital to numerous basic psychological functions and plays an invaluable role in processing and responding to environmental stimuli. Limbic System: Anatomy

Connections with the pituitary Pituitary A small, unpaired gland situated in the sella turcica. It is connected to the hypothalamus by a short stalk which is called the infundibulum. Hormones: Overview and Types gland

The hypothalamus is the primary regulator of the pituitary Pituitary A small, unpaired gland situated in the sella turcica. It is connected to the hypothalamus by a short stalk which is called the infundibulum. Hormones: Overview and Types. The hypothalamus is therefore key in converting and integrating nerve signals with endocrine signals. The hypothalamus is connected to the pituitary Pituitary A small, unpaired gland situated in the sella turcica. It is connected to the hypothalamus by a short stalk which is called the infundibulum. Hormones: Overview and Types in 2 ways: via nerve fibers Nerve Fibers Slender processes of neurons, including the axons and their glial envelopes (myelin sheath). Nerve fibers conduct nerve impulses to and from the central nervous system. Nervous System: Histology and via the circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment.

Nerve fiber connections: the hypothalamohypophyseal tract

• Neurons Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the nervous system. Nervous System: Histology in the paraventricular and supraoptic nuclei have direct projections that end in the posterior pituitary Pituitary A small, unpaired gland situated in the sella turcica. It is connected to the hypothalamus by a short stalk which is called the infundibulum. Hormones: Overview and Types.
• Secretions include:
  • Paraventricular nuclei: primarily produce oxytocin (stimulate uterine contractions in labor and milk release during lactation Lactation The processes of milk secretion by the maternal mammary glands after parturition. The proliferation of the mammary glandular tissue, milk synthesis, and milk expulsion or let down are regulated by the interactions of several hormones including estradiol; progesterone; prolactin; and oxytocin. Breastfeeding)
  • Supraoptic nuclei: primarily produce antidiuretic hormone Antidiuretic hormone Antidiuretic hormones released by the neurohypophysis of all vertebrates (structure varies with species) to regulate water balance and osmolarity. In general, vasopressin is a nonapeptide consisting of a six-amino-acid ring with a cysteine 1 to cysteine 6 disulfide bridge or an octapeptide containing a cystine. All mammals have arginine vasopressin except the pig with a lysine at position 8. Vasopressin, a vasoconstrictor, acts on the kidney collecting ducts to increase water reabsorption, increase blood volume and blood pressure. Hypernatremia (ADH; a vasoconstrictor that stimulates ↑ absorption Absorption Absorption involves the uptake of nutrient molecules and their transfer from the lumen of the GI tract across the enterocytes and into the interstitial space, where they can be taken up in the venous or lymphatic circulation. Digestion and Absorption of water from the renal tubules)

Bloodstream connections: the hypothalamohypophyseal portal system

• Formed from branches off the internal carotid arteries Carotid Arteries Either of the two principal arteries on both sides of the neck that supply blood to the head and neck; each divides into two branches, the internal carotid artery and the external carotid artery. Carotid Arterial System: Anatomy
• Arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology travel through the median eminence (the pituitary Pituitary A small, unpaired gland situated in the sella turcica. It is connected to the hypothalamus by a short stalk which is called the infundibulum. Hormones: Overview and Types “stalk”) → capillaries Capillaries Capillaries are the primary structures in the circulatory system that allow the exchange of gas, nutrients, and other materials between the blood and the extracellular fluid (ECF). Capillaries are the smallest of the blood vessels. Because a capillary diameter is so small, only 1 RBC may pass through at a time. Capillaries: Histology
• Capillaries Capillaries Capillaries are the primary structures in the circulatory system that allow the exchange of gas, nutrients, and other materials between the blood and the extracellular fluid (ECF). Capillaries are the smallest of the blood vessels. Because a capillary diameter is so small, only 1 RBC may pass through at a time. Capillaries: Histology surround cells within the anterior lobe Anterior lobe Cerebellum: Anatomy of the pituitary Pituitary A small, unpaired gland situated in the sella turcica. It is connected to the hypothalamus by a short stalk which is called the infundibulum. Hormones: Overview and Types.
• Neurosecretory cells in the medial zone of the hypothalamus have projections to the median eminence and secrete hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types into the portal system:
  • Releasing hormones Releasing hormones Peptides, natural or synthetic, that stimulate the release of pituitary hormones. They were first isolated from the extracts of the hypothalamus; median eminence; pituitary stalk; and neurohypophysis. In addition, some hypophysiotropic hormones control pituitary cell differentiation, cell proliferation, and hormone synthesis. Some can act on more than one pituitary hormone. Hypothalamic and Pituitary Hormones:
    • Corticotropin-releasing hormone Corticotropin-releasing hormone A peptide of about 41 amino acids that stimulates the release of adrenocorticotropic hormone. Crh is synthesized by neurons in the paraventricular nucleus of the hypothalamus. After being released into the pituitary portal circulation, crh stimulates the release of acth from the pituitary gland. Crh can also be synthesized in other tissues, such as placenta; adrenal medulla; and testis. Hypothalamic and Pituitary Hormones (CRH)
    • Thyrotropin-releasing hormone Thyrotropin-releasing hormone A tripeptide that stimulates the release of thyrotropin and prolactin. It is synthesized by the neurons in the paraventricular nucleus of the hypothalamus. After being released into the pituitary portal circulation, TRH stimulates the release of TSH and PRL from the anterior pituitary gland. Hypothalamic and Pituitary Hormones (TRH)
    • Gonadotropin-releasing hormone Gonadotropin-releasing hormone A decapeptide that stimulates the synthesis and secretion of both pituitary gonadotropins, luteinizing hormone and follicle stimulating hormone. Gnrh is produced by neurons in the septum preoptic area of the hypothalamus and released into the pituitary portal blood, leading to stimulation of gonadotrophs in the anterior pituitary gland. Puberty (GnRH)
    • Growth hormone–releasing hormone ( GHRH GHRH A peptide of 44 amino acids in most species that stimulates the release and synthesis of growth hormone. GHRF (or GRF) is synthesized by neurons in the arcuate nucleus of the hypothalamus. After being released into the pituitary portal circulation, GHRF stimulates gh release by the somatotrophs in the pituitary gland. Hypothalamic and Pituitary Hormones)
  • Release-inhibiting hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types:
    • Somatostatin Somatostatin A 14-amino acid peptide named for its ability to inhibit pituitary growth hormone release, also called somatotropin release-inhibiting factor. It is expressed in the central and peripheral nervous systems, the gut, and other organs. SRIF can also inhibit the release of thyroid-stimulating hormone; prolactin; insulin; and glucagon besides acting as a neurotransmitter and neuromodulator. In a number of species including humans, there is an additional form of somatostatin, srif-28 with a 14-amino acid extension at the n-terminal. Gastrointestinal Secretions
    • Dopamine Dopamine One of the catecholamine neurotransmitters in the brain. It is derived from tyrosine and is the precursor to norepinephrine and epinephrine. Dopamine is a major transmitter in the extrapyramidal system of the brain, and important in regulating movement. Receptors and Neurotransmitters of the CNS

Vasculature

Arterial supply:

The hypothalamus is supplied by the circle of Willis Circle of Willis A polygonal anastomosis at the base of the brain formed by the internal carotid, proximal parts of the anterior, middle, and posterior cerebral arteries, the anterior communicating artery and the posterior communicating arteries. Subarachnoid Hemorrhage:

• Anterior cerebral artery Anterior cerebral artery Artery formed by the bifurcation of the internal carotid artery. Branches of the anterior cerebral artery supply the caudate nucleus; internal capsule; putamen; septal nuclei; gyrus cinguli; and surfaces of the frontal lobe and parietal lobe. Cerebrovascular System: Anatomy → anteromedial branches
• Posterior communicating artery → posteromedial branches
• Posterior cerebral artery Posterior cerebral artery Artery formed by the bifurcation of the basilar artery. Branches of the posterior cerebral artery supply portions of the occipital lobe; parietal lobe; inferior temporal gyrus, brainstem, and choroid plexus. Cerebrovascular System: Anatomy → thalamoperforating branches

Venous drainage:

• Circle of intercavernous sinuses
• Hypothalamohypophyseal portal system

Functions

Overview

The hypothalamus is a sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology and motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology integration center and is a primary regulator of the endocrine and autonomic nervous systems. The hypothalamus plays a major role in:

• Hormone regulation and secretion Secretion Coagulation Studies
• Autonomic effects (e.g., HR, blood pressure, GI secretions and motility Motility The motor activity of the gastrointestinal tract. Gastrointestinal Motility, etc ETC The electron transport chain (ETC) sends electrons through a series of proteins, which generate an electrochemical proton gradient that produces energy in the form of adenosine triphosphate (ATP). Electron Transport Chain (ETC).)
• Thermoregulation Thermoregulation Body temperature can be divided into external temperature, which involves the skin, and core temperature, which involves the CNS and viscera. While external temperature can be variable, the core temperature is maintained within a narrow range of 36.5-37.5ºC (97.7-99.5ºF). Body Temperature Regulation
• Food and water intake
• Sleep Sleep A readily reversible suspension of sensorimotor interaction with the environment, usually associated with recumbency and immobility. Physiology of Sleep and circadian rhythms
• Memory Memory Complex mental function having four distinct phases: (1) memorizing or learning, (2) retention, (3) recall, and (4) recognition. Clinically, it is usually subdivided into immediate, recent, and remote memory. Psychiatric Assessment
• Emotional behavior

Preoptic level

The preoptic area contains:

• Lateral preoptic area: a continuation of the lateral hypothalamic nuclei
• Medial preoptic area:
  • Associated with sexual arousal and sexual dimorphism
  • Produces/secretes GnRH → released into the hypothalamohypophyseal portal system
  • Involved in thermoregulation Thermoregulation Body temperature can be divided into external temperature, which involves the skin, and core temperature, which involves the CNS and viscera. While external temperature can be variable, the core temperature is maintained within a narrow range of 36.5-37.5ºC (97.7-99.5ºF). Body Temperature Regulation
  • Lesions in this region are associated with:
    • Loss of control of sexual behavior
    • Amenorrhea Amenorrhea Absence of menstruation. Congenital Malformations of the Female Reproductive System
    • Impotence

Supraoptic level

The supraoptic level contains several important nuclei including (from superior to inferior):

• Paraventricular nucleus Paraventricular nucleus Nucleus in the anterior part of the hypothalamus. Adrenal Hormones:
  • Medial division: synthesizes and secretes a number of hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types that regulate the pituitary Pituitary A small, unpaired gland situated in the sella turcica. It is connected to the hypothalamus by a short stalk which is called the infundibulum. Hormones: Overview and Types gland
    • CRH 
    • TRH
    • GHRH GHRH A peptide of 44 amino acids in most species that stimulates the release and synthesis of growth hormone. GHRF (or GRF) is synthesized by neurons in the arcuate nucleus of the hypothalamus. After being released into the pituitary portal circulation, GHRF stimulates gh release by the somatotrophs in the pituitary gland. Hypothalamic and Pituitary Hormones
    • Somatostatin Somatostatin A 14-amino acid peptide named for its ability to inhibit pituitary growth hormone release, also called somatotropin release-inhibiting factor. It is expressed in the central and peripheral nervous systems, the gut, and other organs. SRIF can also inhibit the release of thyroid-stimulating hormone; prolactin; insulin; and glucagon besides acting as a neurotransmitter and neuromodulator. In a number of species including humans, there is an additional form of somatostatin, srif-28 with a 14-amino acid extension at the n-terminal. Gastrointestinal Secretions (inhibits growth hormone and thyroid-stimulating hormone Thyroid-stimulating hormone A glycoprotein hormone secreted by the adenohypophysis. Thyrotropin stimulates thyroid gland by increasing the iodide transport, synthesis and release of thyroid hormones (thyroxine and triiodothyronine). Thyroid Hormones (TSH) release)
    • Dopamine Dopamine One of the catecholamine neurotransmitters in the brain. It is derived from tyrosine and is the precursor to norepinephrine and epinephrine. Dopamine is a major transmitter in the extrapyramidal system of the brain, and important in regulating movement. Receptors and Neurotransmitters of the CNS (inhibits prolactin Prolactin A lactogenic hormone secreted by the adenohypophysis. It is a polypeptide of approximately 23 kd. Besides its major action on lactation, in some species prolactin exerts effects on reproduction, maternal behavior, fat metabolism, immunomodulation and osmoregulation. Breasts: Anatomy secretion Secretion Coagulation Studies)
  • Intermediate division: synthesizes hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types that are released from the posterior pituitary Pituitary A small, unpaired gland situated in the sella turcica. It is connected to the hypothalamus by a short stalk which is called the infundibulum. Hormones: Overview and Types gland
    • Oxytocin (primary secretion Secretion Coagulation Studies)
    • ADH produced in small amounts
  • Lateral division: has some direct projections into the vagus nerve Vagus nerve The 10th cranial nerve. The vagus is a mixed nerve which contains somatic afferents (from skin in back of the ear and the external auditory meatus), visceral afferents (from the pharynx, larynx, thorax, and abdomen), parasympathetic efferents (to the thorax and abdomen), and efferents to striated muscle (of the larynx and pharynx). Pharynx: Anatomy
• Anterior nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles:
  • A caudal continuation of the medial preoptic area
  • Involved in thermoregulation Thermoregulation Body temperature can be divided into external temperature, which involves the skin, and core temperature, which involves the CNS and viscera. While external temperature can be variable, the core temperature is maintained within a narrow range of 36.5-37.5ºC (97.7-99.5ºF). Body Temperature Regulation (cooling) and sleep Sleep A readily reversible suspension of sensorimotor interaction with the environment, usually associated with recumbency and immobility. Physiology of Sleep
  • Lesions in this region may lead to hyperthermia.
• Supraoptic nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles:
  • Has direct projections to the posterior pituitary Pituitary A small, unpaired gland situated in the sella turcica. It is connected to the hypothalamus by a short stalk which is called the infundibulum. Hormones: Overview and Types
  • Produces:
    • ADH (primarily)
    • Oxytocin (smaller amounts)
• Suprachiasmatic nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles: 
  • Located just above the optic chiasm Optic Chiasm The x-shaped structure formed by the meeting of the two optic nerves. At the optic chiasm the fibers from the medial part of each retina cross to project to the other side of the brain while the lateral retinal fibers continue on the same side. As a result each half of the brain receives information about the contralateral visual field from both eyes. The Visual Pathway and Related Disorders
  • Gets direct input from the retina Retina The ten-layered nervous tissue membrane of the eye. It is continuous with the optic nerve and receives images of external objects and transmits visual impulses to the brain. Its outer surface is in contact with the choroid and the inner surface with the vitreous body. The outermost layer is pigmented, whereas the inner nine layers are transparent. Eye: Anatomy
  • A “master biologic clock”

Tuberal level

The tuberal level contains:

• Lateral hypothalamic nuclei:
  • Involved in:
    • Regulating appetite and satiety
    • Digestive function
    • Sleep Sleep A readily reversible suspension of sensorimotor interaction with the environment, usually associated with recumbency and immobility. Physiology of Sleep
    • Pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways perception Perception The process by which the nature and meaning of sensory stimuli are recognized and interpreted. Psychiatric Assessment
    • Blood pressure
  • Lesions here may lead to:
    • Narcolepsy Narcolepsy Narcolepsy is a neurological sleep disorder marked by daytime sleepiness and associated with cataplexy, hypnagogic hallucinations, and sleep paralysis. There are 2 types of narcolepsy: type 1 is associated with cataplexy and type 2 has no association with cataplexy. Narcolepsy
    • Motility Motility The motor activity of the gastrointestinal tract. Gastrointestinal Motility or functional GI disorders
    • Eating disorders (due to ↓↓ desire to eat)
• Dorsomedial nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles:
  • Involved in:
    • Physiologic circadian rhythms (e.g., eating and drinking, energy consumption)
    • Ingestive behavior
    • Cardiovascular response to stress
  • Lesions here may lead to: overeating (hyperphagia), obesity Obesity Obesity is a condition associated with excess body weight, specifically with the deposition of excessive adipose tissue. Obesity is considered a global epidemic. Major influences come from the western diet and sedentary lifestyles, but the exact mechanisms likely include a mixture of genetic and environmental factors. Obesity
• Ventromedial nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles:
  • Involved in:
    • Appetite, satiety, and energy regulation
    • Fear response via afferent Afferent Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology input from the amygdala Amygdala Almond-shaped group of basal nuclei anterior to the inferior horn of the lateral ventricle of the temporal lobe. The amygdala is part of the limbic system. Limbic System: Anatomy
  • Lesions here may lead to: hyperphagia, obesity Obesity Obesity is a condition associated with excess body weight, specifically with the deposition of excessive adipose tissue. Obesity is considered a global epidemic. Major influences come from the western diet and sedentary lifestyles, but the exact mechanisms likely include a mixture of genetic and environmental factors. Obesity
• Arcuate nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles:
  • A primary regulator of the anterior pituitary Pituitary A small, unpaired gland situated in the sella turcica. It is connected to the hypothalamus by a short stalk which is called the infundibulum. Hormones: Overview and Types gland via the hypothalamohypophyseal portal system
  • Secretes:
    • GnRH
    • Dopamine Dopamine One of the catecholamine neurotransmitters in the brain. It is derived from tyrosine and is the precursor to norepinephrine and epinephrine. Dopamine is a major transmitter in the extrapyramidal system of the brain, and important in regulating movement. Receptors and Neurotransmitters of the CNS → regulates prolactin Prolactin A lactogenic hormone secreted by the adenohypophysis. It is a polypeptide of approximately 23 kd. Besides its major action on lactation, in some species prolactin exerts effects on reproduction, maternal behavior, fat metabolism, immunomodulation and osmoregulation. Breasts: Anatomy secretion Secretion Coagulation Studies
    • Neuropeptide Y → regulates appetite and body weight
  • Lesions here may lead to: galactorrhea Galactorrhea Excessive or inappropriate lactation in females or males, and not necessarily related to pregnancy. Galactorrhea can occur either unilaterally or bilaterally, and be profuse or sparse. Its most common cause is hyperprolactinemia. Hyperprolactinemia, hyperphagia

Mammillary level

The mammillary level includes:

• Posterior nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles:
  • Involved in thermoregulation Thermoregulation Body temperature can be divided into external temperature, which involves the skin, and core temperature, which involves the CNS and viscera. While external temperature can be variable, the core temperature is maintained within a narrow range of 36.5-37.5ºC (97.7-99.5ºF). Body Temperature Regulation (heating the body)
  • Lesion here may lead to: hypothermia Hypothermia Hypothermia can be defined as a drop in the core body temperature below 35°C (95°F) and is classified into mild, moderate, severe, and profound forms based on the degree of temperature decrease. Hypothermia
• Mammillary bodies Mammillary bodies A pair of nuclei and associated gray matter in the interpeduncular space rostral to the posterior perforated substance in the posterior hypothalamus. Limbic System: Anatomy:
  • Involved in regulating emotions and recollective memory Memory Complex mental function having four distinct phases: (1) memorizing or learning, (2) retention, (3) recall, and (4) recognition. Clinically, it is usually subdivided into immediate, recent, and remote memory. Psychiatric Assessment
  • Lesion here may lead to:
    • Memory Memory Complex mental function having four distinct phases: (1) memorizing or learning, (2) retention, (3) recall, and (4) recognition. Clinically, it is usually subdivided into immediate, recent, and remote memory. Psychiatric Assessment deficits
    • Pathogenesis of Wernicke encephalopathy Encephalopathy Hyper-IgM Syndrome

Clinical Relevance

• Central diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus insipidus ( DI DI Diabetes insipidus (DI) is a condition in which the kidneys are unable to concentrate urine. There are 2 subforms of di: central di (CDI) and nephrogenic di (NDI). Both conditions result in the kidneys being unable to concentrate urine, leading to polyuria, nocturia, and polydipsia. Diabetes Insipidus): condition in which the kidneys Kidneys The kidneys are a pair of bean-shaped organs located retroperitoneally against the posterior wall of the abdomen on either side of the spine. As part of the urinary tract, the kidneys are responsible for blood filtration and excretion of water-soluble waste in the urine. Kidneys: Anatomy are unable to concentrate urine because of a lack of circulating ADH. These low levels of ADH are due to either decreased production within the hypothalamus or decreased release from the posterior pituitary Pituitary A small, unpaired gland situated in the sella turcica. It is connected to the hypothalamus by a short stalk which is called the infundibulum. Hormones: Overview and Types gland. Presentation is with polyuria Polyuria Urination of a large volume of urine with an increase in urinary frequency, commonly seen in diabetes. Renal Potassium Regulation, nocturia Nocturia Frequent urination at night that interrupts sleep. It is often associated with outflow obstruction, diabetes mellitus, or bladder inflammation (cystitis). Diabetes Insipidus, and polydipsia Polydipsia Excessive thirst manifested by excessive fluid intake. It is characteristic of many diseases such as diabetes mellitus; diabetes insipidus; and nephrogenic diabetes insipidus. The condition may be psychogenic in origin. Diabetes Insipidus. Central and nephrogenic DI DI Diabetes insipidus (DI) is a condition in which the kidneys are unable to concentrate urine. There are 2 subforms of di: central di (CDI) and nephrogenic di (NDI). Both conditions result in the kidneys being unable to concentrate urine, leading to polyuria, nocturia, and polydipsia. Diabetes Insipidus are differentiated based on measured ADH levels and response to the water deprivation test Water Deprivation Test Diabetes Insipidus. Central DI DI Diabetes insipidus (DI) is a condition in which the kidneys are unable to concentrate urine. There are 2 subforms of di: central di (CDI) and nephrogenic di (NDI). Both conditions result in the kidneys being unable to concentrate urine, leading to polyuria, nocturia, and polydipsia. Diabetes Insipidus is treated with desmopressin Desmopressin Hemophilia.
• Functional hypothalamic amenorrhea Functional Hypothalamic Amenorrhea Secondary Amenorrhea: primary cause of secondary amenorrhea Amenorrhea Absence of menstruation. Congenital Malformations of the Female Reproductive System (cessation of menses Menses The periodic shedding of the endometrium and associated menstrual bleeding in the menstrual cycle of humans and primates. Menstruation is due to the decline in circulating progesterone, and occurs at the late luteal phase when luteolysis of the corpus luteum takes place. Menstrual Cycle). Functional hypothalamic amenorrhea Functional Hypothalamic Amenorrhea Secondary Amenorrhea results from the decreased pulsation of GnRH from the hypothalamus that occurs during times of severe physical or psychologic stress. The condition is most commonly seen in association with eating disorders or overexercise (common in female athletes). Management usually requires nutritional support and counseling.
• Hyperthermia: may occur if there is a lesion (stroke or CNS damage) in the anterior nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles of the hypothalamus, which is involved in thermoregulation Thermoregulation Body temperature can be divided into external temperature, which involves the skin, and core temperature, which involves the CNS and viscera. While external temperature can be variable, the core temperature is maintained within a narrow range of 36.5-37.5ºC (97.7-99.5ºF). Body Temperature Regulation, specifically, cooling the body down. Damage to this region prevents the body from being able to cool itself. 
• Narcolepsy Narcolepsy Narcolepsy is a neurological sleep disorder marked by daytime sleepiness and associated with cataplexy, hypnagogic hallucinations, and sleep paralysis. There are 2 types of narcolepsy: type 1 is associated with cataplexy and type 2 has no association with cataplexy. Narcolepsy: occurs when the lateral hypothalamus is unable to secrete orexin, a substance that promotes wakefulness in many areas of the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification, allowing inappropriate sudden transitions to sleep Sleep A readily reversible suspension of sensorimotor interaction with the environment, usually associated with recumbency and immobility. Physiology of Sleep, cataplexy Cataplexy A condition characterized by transient weakness or paralysis of somatic musculature triggered by an emotional stimulus or physical exertion. Cataplexy is frequently associated with narcolepsy. During a cataplectic attack, there is a marked reduction in muscle tone similar to the normal physiologic hypotonia that accompanies rapid eye movement sleep (sleep, rem). Narcolepsy, sleep paralysis Sleep paralysis A common condition characterized by transient partial or total paralysis of skeletal muscles and areflexia that occurs upon awakening from sleep or less often while falling asleep. Stimuli such as touch or sound may terminate the episode, which usually has a duration of seconds to minutes. This condition may occur in normal subjects or be associated with narcolepsy; cataplexy; and hypnagogic hallucinations. The pathophysiology of this condition is closely related to the normal hypotonia that occur during rem sleep. Narcolepsy, and hypnagogic hallucinations Hypnagogic hallucinations Narcolepsy.
• Hyperprolactinemia Hyperprolactinemia Hyperprolactinemia is defined as a condition of elevated levels of prolactin (PRL) hormone in the blood. The PRL hormone is secreted by the anterior pituitary gland and is responsible for breast development and lactation. The most common cause is PRL-secreting pituitary adenomas (prolactinomas). Hyperprolactinemia: elevated levels of prolactin Prolactin A lactogenic hormone secreted by the adenohypophysis. It is a polypeptide of approximately 23 kd. Besides its major action on lactation, in some species prolactin exerts effects on reproduction, maternal behavior, fat metabolism, immunomodulation and osmoregulation. Breasts: Anatomy in the blood. Although the most common cause of hyperprolactinemia Hyperprolactinemia Hyperprolactinemia is defined as a condition of elevated levels of prolactin (PRL) hormone in the blood. The PRL hormone is secreted by the anterior pituitary gland and is responsible for breast development and lactation. The most common cause is PRL-secreting pituitary adenomas (prolactinomas). Hyperprolactinemia is a prolactin-secreting pituitary Pituitary A small, unpaired gland situated in the sella turcica. It is connected to the hypothalamus by a short stalk which is called the infundibulum. Hormones: Overview and Types adenoma, loss of inhibitory dopamine Dopamine One of the catecholamine neurotransmitters in the brain. It is derived from tyrosine and is the precursor to norepinephrine and epinephrine. Dopamine is a major transmitter in the extrapyramidal system of the brain, and important in regulating movement. Receptors and Neurotransmitters of the CNS secretion Secretion Coagulation Studies by the hypothalamus can also be a cause. This condition can occur when dopaminergic neurons Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the nervous system. Nervous System: Histology from the hypothalamus are damaged or if the infundibulum Infundibulum Uterus, Cervix, and Fallopian Tubes: Anatomy is transected during suprasellar surgery. Presentations can include galactorrhea Galactorrhea Excessive or inappropriate lactation in females or males, and not necessarily related to pregnancy. Galactorrhea can occur either unilaterally or bilaterally, and be profuse or sparse. Its most common cause is hyperprolactinemia. Hyperprolactinemia (milky discharge), oligomenorrhea Oligomenorrhea Polycystic Ovarian Syndrome, and erectile dysfunction Erectile Dysfunction Erectile dysfunction (ED) is defined as the inability to achieve or maintain a penile erection, resulting in difficulty to perform penetrative sexual intercourse. Local penile factors and systemic diseases, including diabetes, cardiac disease, and neurological disorders, can cause ED. Erectile Dysfunction.