Hypothalamus Flashcards
three points of this lecture: - neuroanatomy (structure/function) - hypothalamic-Pituitary regulation (key hypothalamic structures, key functions of hypothalamic regions, diff between control of anterior and posterior pituitary secretion) - sex and sexual dimorphism
functions of hypothalamus?
- internal homeostasis
- endocrine control through pituitary
- autonomic nervous system control
- regulation of food and water intake
- emotion and behavior
- circadian rhythms
function of nucleus: PVN, AH, medial preoptic, SON, SCN, VMH and mammillary body
paraventricular nucleus: water balance; stress; social bonding; secretes ADH (AVP) + oxytocin
medial preoptic: blood pressure; male sex; maternal care
anterior hypothalamic area (AH): body temperature; aggression
supra-optic nucleus: water balance; secretes oxytocin + ADH
suprechiasmatic: biological clock
ventromedial nucleus: satiety; female sex
mammillary body: feeding
functional zones of hypothalamus
- Periventricular-Borders the third ventricle. Important for regulation of anterior pituitary function
- Middle Zone
produces oxytocin and vasopressin.
Regulates release of peptides from posterior pituitary
Modulate autonomic nervous system. - Lateral Zone
Integrates information from other limbic structures. Involved in regulation emotion and behavior.
functional anatomy of medial preoptic area
Medial preoptic area- lateral zone
Regulates Reproductive Endocrinology;
Regulates Sexual and Maternal Behaviors;
Sexually Dimorphic Areas;
functional anatomy of paraventricular nucleus (PVN)
- Parvocellular neurons project to the capillaries of the median eminence (external zone) where they release vasopressin and CRF into the portal vein.
- Autonomic division projects to the brain stem and spinal cord via the medial forebrain bundle to regulate preganglionic autonomic neurons.
functional anatomy of SCN, VMN, and Arcuate
1. Suprachiasmatic nucleus- Circadian Rhythms. 2. Ventromedial nucleus (VMN or VMH)- Feeding Sexual Behavior. 3. Arcuate nucleus (periventricular) neurosecretory cells regulating anterior pituitary hormone secretion; Project to median eminence and terminate on portal capillary bed.
the study shows that SCN regulates circadian period
Hamster Experiment
Even without light, normal hamster maintains 24 hour cycle while Tau mutant 20 hours cycle
mutation of Tau: 20 hours cycle instead of 24;
lesion of SCN makes running cycle random;
brain transplant of Tau into WT makes it run after 20 hours cycle, while transplant of WT into Tau makes it run 24 hours cycle
anterior and posterior pituitary
Anterior=adenohypophysis - Non-neuronal ectoderm - Epithelial Cells (no neurons) - Derived from Rathke’s Pouch (back part of mouth)/ closed system Posterior=neurohypophysis - Neuronal ectoderm - neurons - open system
function of posterior pituitary and function of oxytocin/vasopression
neurons from PVN and SON project directly to the posterior pituitary and secrete oxytocin and vasopressin into the blood stream
Note: oxytocin regulates uterine contraction and milk ejection;
vasopression regulates vascular tone and water re-absorption in the kidney
regulation of oxytocin secretion during birth
positive feedback: uterine contraction/cervical stimulation etc > NTS > oxytocin neurons > induce contraction
- hypothalamus bursts
- oxytocin released to bloodstream
- oxytocin causes uterine contraction
- uterine contraction causes the release of more oxytocin
regulation of vasopressin secretion
- baroreceptors: sensing blood pressure > send signal to pituitary through nucleus of the solitary tract
- osmolarity
functional anatomy of paraventricular and supraoptic nuclei
- Magnocellular (middle zone) neurons project directly to posterior pituitary and regulate oxytocin and vasopressin release.
- Parvocellular
- Autonomic division
AVP regulates water reabsorption in the kidney
NaCl increases AVP while alcohol decreases it
AVP opens aquaporins
anterior pituitary (periventricular zone)
neurosecretory cells (most in hypothalamus) release hormones in portal vein and secondary plexus and diffuse to endocrine cells (parvocellular (small))
describe the short and long feedback loop in hypothalamus that modulate endocrine function
long loop: testes and testosterone
short loop: GnRH, LH, FSH
LH and FSH stimulates the secretion of testes
short loop
- hypothalamus release of releasing factors (GnRH) to anterior pituitary
- anterior pituitary releases tropic hormone (LH, FSH)
- tropic hormones act in the testes
- tropic hormones feed back to hypothalamus to inhibit GnRH production
long loop
1 ~ 3 are the same
4. testes release hormone (testosterone) which inhibits GnRH production in hypothalamus