Endocrine

Question 1

magnocellular neurons vs parvicallular neurons
size and location
hormones released from where?

Answer 1

magnocellular: larger, located within supraoptic paraventricular nuclei. hormones released from posterior pituitary

parvicellular: smaller, located within multiple different nuclei in hypothalamus
hormones released from median eminence (portal vein near ant. pituitary), brainstem, SC

Question 2

which neurohormones are produced from magnocellular neurons

Answer 2

oxytocin
vasopressin/ADH

Question 3

which neurohormones are produced from parvicellular neurons

Answer 3

CRH
TRH
GHRH
GHIH
DA
GnRH/LHRH
PRH

Question 4

oxytocin function

Answer 4

stimulate uterine contractions

Question 5

vasopressin/ADH function

Answer 5

promote water reabsorption
stimulate thirst

Question 6

CRH function

Answer 6

stimulates ACTH release from anterior pituitary

Question 7

TRH function

Answer 7

stimulates TSH release

Question 8

GHRH/LHRH function from anterior pituitary

Answer 8

stimulate FSH and LH release from anterior pituitary

Question 9

what does PRIH/DA do?

Answer 9

PRIH - prolactin inhibiting hormone
DA - domapine

function: inhibits prolactin release

Question 10

where is the inferior hypophyseal artery

Answer 10

posterior pituitary, where the magnocellular neurons release their hormones into systemic circulation

Question 11

describe the circulation of blood and hormones through the anterior pituitary

Answer 11

• some cells can make their own hormones (lactotrophs, somatotrophs)
• hypothalamic parvicellular neurons release hormones into primary capillary plexus within the median eminence -> superior hypophyseal artery -> primary capillary tract -> portal vein -> secondary capillary tract -> anterior pituitary
• releases hormones into hypophyseal veins and on to systemic circulation via internal jugular vein

Question 12

what types of specialized neurons are present in the hypothalamus

Answer 12

glucose-sensing neurons
osmoreceptors

Question 13

what type of cells produce growth hormone? where are they located?

Answer 13

somatotrophs
located in anterior pituitary

Question 14

under what conditions is growth hormone released?

Answer 14

in pulsatile bursts, major bursts at night
during slow wave sleep

Question 15

what is the function of growth hormone binding protein?

Answer 15

transports GH
serves as a reservoir and prolongs half life to prevent degradation, otherwise free GH is broken down within 20 mins

Question 16

major functions of GH:

Answer 16

stimulates IGF-1 release from liver
stimulates postnatal longitudinal growth (anabolic and mitogenic effects)

Question 17

patterns of GH production/secretion across life

Answer 17

decreases after first 1-2 years of life
peaks in puberty
declines in adulthood and as we continue aging

Question 18

conditions that stimulate GH secretion

Answer 18

GHRH is triggered by: hypoglycemia, arginine, catecholamines, dopamine
Ghrelin (stomach, pancreas, kidney, liver, hypothalamus)

Question 19

factors and conditions that inhibit GH secretion

Answer 19

• somatostatin/GHIH: hyperglycemia, increased non-esterified fatty acids
• IGF-1: inhibits GHRH release and stim GHIH

Question 20

functions of somatostatin
where is it synthesized

Answer 20

• synthesized by many parts of the brain and other organs (pancreas, stomach)
• binds to G-alpha-i-somatostatin receptor and promotes tyrosine phosphatase activity (deactivates things)
• binds to K+ channels which hyperpolarizes cells and stops release of GH

Question 21

what should you know about GH receptor

Answer 21

• belongs to class 1 cytokine receptor family
• located on: liver, bone, kidney, adipose tissue, muscle, brain, eye, heart, immune cells
• 2 binding sites allow GH receptors to dimerize when GH binds and dimerization increases JAK activity which leads to phosphorylation of tyrosine residues -> release of activators of transcription proteins/expression of GH-regulated genes

Question 22

what is the other name for IGF-1?

Answer 22

somatomedin

Question 23

functions of IGF-1
what is it regulated by

Answer 23

regulated by GH, PTH and reproductive hormones in bone
function: stimulates bone formation and turn over, protein synthesis, glucose uptake into muscles, mitogenic

Question 24

how IGF-1 levels vary across lifespan

Answer 24

low levels at birth
increases during childhood/puberty
begins declining in 3rd decade

Question 25

what is the most common cause of acromegaly?

Answer 25

due to somatotrope adenoma, resutling in an over secretion of GH

Question 26

in acromegaly, what are the effects on peripheral tissues?

Answer 26

bone: acral bone overgrowth, increased hand/foot size, mandibular enlargement with prognathism, wide space between incisor teeth soft tissue: increased heel pad thickness, coarse facial features, large fleshy nose

Question 27

what is the impact of acromegaly on the CV system?

Answer 27

- cardiomyopathy with arrhythmias (LV hypertrophy, decreased diastolic function, hypertension) - upper airway obstruction with sleep apnea (central sleep dysfunction, soft tissue laryngeal airway obstruction) - diabetes - hyperglycemia puts stress on insulin function

Question 28

under what conditions might gigantism occur?

Answer 28

if increased GH secretion occurs before epiphyseal long bone closure in children or adolescents

Question 29

what type of cells are responsible for secreting prolactin? where are these cells located?

Answer 29

lactotrophs in the anterior pituitary

Question 30

what is a condition where the amount of lactotrophs would increase?

Answer 30

pregnancy in response to estrogen

Question 31

functions of prolactin

Answer 31

development of mammary glands and milk production maintain milk synthesis inhibit GnRH

Question 32

when are prolacin levels elevated and reduced?

Answer 32

increases during sleep and reduces during waking hours

Question 33

what stimulates release of prolactin

Answer 33

increased estrogen sucking - results in dopamine release from hypothalamus, causing prolactin to be released GnRH (regulates FSH and LH) serotoninergic and opioidergic pathways prolactin releasing factors: TRH, oxytocin, vasoactive intestinal peptide

Question 34

why is prolactin not constantly being released?

Answer 34

it is under tonic inhibition from the dopamine binding to D2 receptors on the lactotrophs dopamine released from hypothalamus will all the time inhibit prolactin stomatostatin and GABA also exert inhibitory effect, just to a lesser extent than dopamine

Question 35

when someone is lactating, why is there sometimes a delay in menstrual cycle?

Answer 35

because prolactin inhibits GnRH which would stimulate FSH and LH that normally regulate the menstrual cycle

Question 36

where are prolactin receptors located?

Answer 36

mammary gland ovary brain