|Search for Hypothalamus in Gray's.|
The hypothalamus is the key organ regulating body homeostasis and is a region of cerebral nuclei with diverse and multiple neuroendocrine function anterior to the brain stem.
It includes the subthalamic tegmental region and the structures related to most of the floor of the third ventricle such as the mammillary bodies and infundibulum superior to the pituitary and optic chiasma.
- Projections map to the:
- Arcuate nucleus and ventromedial hypothalamus
- Regulates weight
- Proopiomelanocortin neurons (PRMC) release alpha melanocyte-stimulating hormone(α-MSH) that promotes weight loss while its agouti-related peptide neurons release agouti-related peptide (AgRP) and two inhibitory neurotransmitters neuropeptide Y (NPY) and gamma-aminobutyric acid (GABA) that promote weight gain.
- Contain glucose-sensitive neurons that help regulate appetite
- The arcuate nucleus also produces gonadotropin-releasing hormone and follicle stimulating hormone releasing factor
- Anterior hypothalamic nucleus
- Involved in thermoregulation, panting, sweating and thyrotropin inhibition
- Dorsomedial hypothalamic nucleus
- Involved in gastrointestinal stimulation
- Lateral nucleus
- Medial preoptic nucleus
- Urinary bladder contraction, heart rate and blood pressure modulation
- Neurohypophysis and the median eminence
- Role in neurosecretion
- Paraventricular nucleus
- Subfornical organ(SFO) and the organum vasculosum of the lamina terminalis (OVLT) - the circumventricular organs
- Regulate body water and solute balance.
- Neurons project to the supraoptic nucleus, paraventricular nucleus, and the preoptic hypothalamic areas
- Suprachiasmatic nucleus
- Supraoptic nucleus
- Ventromedial nucleus
- Involved in satiety
- Involved in male vocalizations and scent marking behaviors and sexual behaviours (in females)
The hypothalamus controls body temperature, hunger, thirst, emotional and reproductive responses and circadian cycles. Parts of the hypothalmus such as the neurohypophysis, the median eminence, subfornical organ and the OVLT do not have a blood brain barrier to enable such regulation. There appears to be active uptake of other hormones such as prolactin and leptin in the choroid plexus from blood into CSF to also aid regulation. There is wide neuron input from:
- Nucleus of the solitary tract
- Locus coeruleus
- Ventrolateral medulla.
- Vagus nerve relays
- Olfactory lobes
- Optic nerves
These functions include (some can only be postulated from mammals which have say different reproductive physiology from humans):
- Pheromonal cues
- Neuron reaction to circulating peptide hormones
- Modulation of hypothalamic neurons by steroids and glucocorticoids
- Oxytocin secretion modulation by neuron stimulation nipples and genitals
- Vasopressin secretion modulation by chemoreceptors in the carotid sinus and aortic arch, and from low-pressure atrial volume receptors*
- Prolactin secretion modulated by projections from genitals and nipples.
- Vagal modulation of cardiovascular and visceral stimuli
- Paraventricular nucleus contains:
- Medial preoptic nucleus neuroendocrine neurons secrete gonadotropin-releasing hormone
- Arcuate nucleus neuroendocrine neurons secrete:
- Anterior hypothalamic nuclei contain parvocellular neuroendocrine neurons that secrete thyrotropin-releasing hormone