Lecture: Neuroendocrine regulation & pituitary Flashcards
where is the hypothalamus located
The hypothalamus is located at the base of the brain (“stimulus”)
Relatively small structure receiving many inputs from many other areas of brain.
Secretes multiple hormones to control widespread homeostatic functions
Uses the pituitary gland as an output organ (initiates “response”) – aka hypophysis
posterior hypothalamic nucleus regulates
blood pressure, pupillary dilation
temperature control
dorsomedial nucleus controlls what
GI control
perifornical nucleus
hunger, blood pressure,
rage
ventromedial nucleus
neuroendocrine, feeding
posterior preoptic and anterior
hypothalamus
panting, sweating
medial preoptic area
bladder and cardiovascular
control
supraoptic nucleus
vasopressin/ release
Neurosecretory cells
responsible for release of regulatory hormones to control pituitary gland
Cells in periventricular zone- Connections of the hypothalamus
Suprachiasmatic neurones - receive retinal innervation and synchronize circadian rhythms in the light-dark cycle
Send output to sympathetic and parasympathetic output neurones in spinal cord to control activity of ANS
Endocrine functions of the hypothalamus
2 ways
1. HYPOTHALAMUS
-Indirect via release of
regulatory hormones-ANTERIOR PITUITARY Release of regulatory hormones Release of primary hormones- Target endocrine glands
- HYPOTHALAMUS
Primary hormones:Oxytocin (supraoptic nucleus), ADH (paraventricular nucleus)- POSTERIOR PITUITARY
Hypothalamic regulatory hormones
Releasing factors
CRF - corticotropin releasing factor
TRH - thyrotropin releasing hormone
GHRH - growth hormone releasing hormone
GnRH - gonadotropin releasing hormone
PRF - prolactin releasing factor
Inhibiting factors
GHIH - Growth hormone inhibiting hormone
PIH - prolactin inhibiting hormone
MSH-IH - melanocyte stimulating hormone inhibiting hormone
Anterior pituitary hormones
Four trophic hormones
Thyroid Stimulating Hormone
AdrenoCorticoTrophic Hormone
Follicle Stimulating Hormone
Luteinizing Hormone
Two primary hormones
Growth Hormone
PRoLactin
Effects of growth hormone (aka somatotrophin, somatotropin)
Increase cell size, number and differentiation
Stimulate protein synthesis
Stimulate fat utilization
Alter carbohydrate metabolism
Somatomedins/IGFs
Somatomedins are
small proteins produced by the liver in response to GH (insulin-like growth factors)
at least 4 produced - somatomedin C is most important
long half life (20 hrs) compared to GH (<20 mins)
Somatomedins/IGFs also act via a receptor tyrosine kinase
Effects of GH/somatomedins on protein synthesis
increase uptake, translation and transcription all cause increased protein synthesis
growth hormones direct effect
Metabolic effects
Increases fat breakdown
Increases blood glucose (anti-insulin)
Growth hormone (GH) secretion
Released in response to growth hormone-releasing hormone (GHRH)
Release decreased by growth hormone-inhibiting hormone (GHIH or somatostatin)
Both released from ventromedial hypothalamus
GH is regulated by a short feedback loop
Controlled by many factors: sleep, exercise, stress
Growth hormone is a polypeptide hormone that acts at a receptor tyrosine kinase
growthy hormones indirect effect
somatomedins- Growth Effects
Increase cell size, number,
differentiation
Increase protein synthesis
Increase bone growth
Why is growth hormone important in the healthy body?
Deficit
Dwarfism - may be
general anterior pituitary dysfunction -
specific GH deficit
normal GH but heriditary somatomedin deficit
Accelerated aging - loss of growth hormone after adolescence
decreased protein synthesis
Excess GH
Gigantism – early life pituitary tumour
Acromegaly- pituitary tumour after adolescence
Hypothalamic-pituitary axis- GnRH in hypothalamus causes
pituitary causes LH,FH - which causes the end organ testis and ovary to produce this
Hypothalamic-pituitary axis- TRH in hypothalamus causes
pituitary causes TSH- which causes the end thyroid to produce this
Hypothalamic-pituitary axis- CRF in hypothalamus causes
pituitary causes ACTH - which causes the end organ adrenal to produce this
Hypothalamic-pituitary axis- GHRH and SRIF in hypothalamus causes
pituitary causes GH/somatotropin - which causes the end organ multiple tissues to produce this
Hypothalamic-pituitary axis- PRF and PIH in hypothalamus causes
pituitary causes Prolactin - which causes the end organ breast to produce this
feedback control of pituitary axis
hypothalamus to releasing hormone to anterior pituitary to pituitary hormone to endocrine gland to hormone
