Hypothalamus And Hypophysis

Front 1

Important point about BBB

Back 1

portions of hypothalamus are NOT protected by BBB. this allows for establishment of hormonal feedback loops

Front 2

hypothalamus communicates with pituitary in two ways:

Back 2

1. anterior pituitary through portal vasculature

2. posterior pituitary via nerve axons from supraoptic and paraventricular nuclei

Front 3

hormones secreted from anterior pituitary are:

Back 3

trophic hormones: regulate activity of other endocrine glands

HGH is main secretion

thyrotropin (TSH)

gonadotropin (FSH and LH)

adrenocorticotropin (ACTH)

prolactin

Front 4

HGH

Back 4

increases growth and maintains tissues once appropriate size achieved

release is stimulated by sleep, stress, hypoglycemia, exercise

release is inhibited by somatostatin, beta adrenergics, hyperglycemia, FFA

Front 5

HGH direct actions

Back 5

tells progenitor/stem cells to make precursor cells

stimulates synthesis and release of IGF1 and IGF2 (aka somatomedins)

Effects:

increased protein anabolism and lipolysis,

chondrogenesis in bone

Front 6

HGH indirect actions

Back 6

acts on organs and tissues, mainly through IGF1

Front 7

control of HGH secretion

Back 7

excess levels in plasma inhibit production

excess levels stimulates production of somatostatin, which further inhibits HGH

excess IGF1 and IGF2 inhibit HGH release and also stimulate production of somatostatin

Front 8

HGH effect on protein

Back 8

anabolic on muscle:

increases RNA synthesis

increases amino acid incorporation into protein

creates positive nitrogen balance (sets BUN)

Front 9

HGH effect on fat

Back 9

catabolizes fat and releases triglycerides

results in synthesis of glycerol and increased FFA in plasma

Front 10

HGH effect on carbs

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increases glucose in plasma:

inhibits glucose use by muscle and fat

increases glucose production by liver

renders muscle and fat insensitive to insulin

diabetogenic effect (anti-insulin):

causes hyperglycemia, excessively stimulates insulin producing beta cells in pancreas

Front 11

HGH pathologies

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excess:

during growth cycle: gigantism

during adulthood: acromegaly

too little:

during growth cycle: dwarfism

during adulthood: decreased organ size/function

Front 12

melanocyte stimulating hormone (MSH)

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released by intermediate lobe of pituitary

pheomelanin (light) and eumelanin (dark) determine skin color

MSH1 causes tanning when exposed to UV

tanning action of MSH1 is opposed by T4

Front 13

posterior pituitary

Back 13

stores hormones produced by nerves from hypothalamus:

oxytocin from paraventricular nuclei

vasopressin (ADH) from supraoptic nuclei

both are transported through axon by neurophysin

Front 14

ADH

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osmoreceptors stimulate its release

increases collecting duct H2O permeability to restore plasma osmolarity back to normal

pathologies:

diabetes insipidus (DI) - polyuria due to lack of ADH release (no glucose in urine though)

syndrome of inappropriate ADH - ADH secreting tumor inappropriately concentrates urine

Front 15

oxytocin

Back 15

release is stimulated by suckling and dilation of cervix during parturition

functions:

induces strong uterine contractions, does NOT induce labor

forces milk into storage cisterns, then out through nips ("milk letdown" hormone)

release of adequate amounts also initiates strong feelings of trust and love through the amygdala

Front 16

melatonin

Back 16

secreted by pineal gland

darkness stimulus is converted to APs by specialized cones, travels from retina >>> suprachiasmatic nucleus >>> nucleus interomediolateralis >>> superior cervical ganglion >>> pineal gland >>> release of melatonin

IMPORTANT: only suprachiasmatic nucleus can influence circadian rhythms of other hormones