pituitary

Question 1

what is the posterior pituitary also called

Answer 1

neurohypophysis

Question 2

neurohypophysis origin

Answer 2

downgrowth from neural tissue

Question 3

principle features of posterior pituitary

Answer 3

very long neurones originating in hypothalamus, projecting to posterior, and releasing vasopressin and oxytocin

Question 4

where are neuronal cell bodies located

Answer 4

in supraoptic and paraventricular nuclei

Question 5

supraoptic neurone pathway

Answer 5

leave hypothalamic supraoptic nuclei, pass through median eminence, terminate in neurohypophysis

Question 6

what two types of supraoptic neurone are there

Answer 6

vasopressinergic or oxytocinergic

Question 7

sites of vesicle storage of hormones in supraoptic neurones

Answer 7

Herring bodies

Question 8

magnocellular paraventricular neurone pathway

Answer 8

leave paraventricular nuclei, terminate in neurohypophysis

Question 9

parvocellular neurone pathway

Answer 9

leave paraventricular nuclei, terminate in the median eminence (similar to antrerior pituitary) or other parts of the brain

Question 10

what influences ACTH secretion, and what is the outcome

Answer 10

vasopressin and CRH influence ACTH secretion, which influences cortisol

Question 11

what two types of paraventricular neurone are there

Answer 11

vasopressinergic or oxytocinergic

Question 12

vasopressin and oxytocin: differences and significance

Answer 12

are nonapeptides (derived from 9 amino acids): vasopressin: Phe and Arg; oxytocin: Ile and Leu; as very similar, some overlap in functions

Question 13

purpose of signal peptide

Answer 13

signal peptide allows pre-prohormone from cytoplasm to be recognised by Golgi

Question 14

fate of signal peptide

Answer 14

cleaved off to leave prohormone

Question 15

formation of hormone from prohormone

Answer 15

as vesicles move along neurone axon, enzyme splits prohormone into hormone (vasopressin or oxytocin) and other sections

Question 16

other sections of cleaved prohormone besides vasopressin

Answer 16

neurophysin and glycopeptide

Question 17

other sections of cleaved prohormone besides oxytocin

Answer 17

different form of neurophysin, no glycopeptide

Question 18

neurophysin purpose

Answer 18

carrier protein which protects and carries hormone to posterior pituitary before secreted

Question 19

name the two different vasopressin receptors

Answer 19

V1 and V2

Question 20

V1 vasopressin receptors: intracellular response

Answer 20

intracellular calcium increase to produce cellular response

Question 21

where is V1a present

Answer 21

arterial/arteriolar smooth muscle

Question 22

V1a function

Answer 22

acts as a vasoconstrictor

Question 23

where is V1b present

Answer 23

anterior pituitary in corticotrophs

Question 24

V1b function

Answer 24

ACTH production

Question 25

V2 vasopressin receptors: intracellular response

Answer 25

increase in cAMP to produce cellular response

Question 26

where is V2 present

Answer 26

collecting duct cells

Question 27

V2 function

Answer 27

water reabsoroption as it is anti-diuretic hormone

Question 28

V2 as anti-diuretic hormone: binding to PKA

Answer 28

V2 binds to receptor → activates G protein → increases activity of adenyl cyclase → more cAMP produced → activates PKA

Question 29

V2 as anti-diuretic hormone: PKA to aquaporins

Answer 29

PKA → increase synthesis and movement of AQP2 aquaporin channels towards impermeable apical membrane → insertion → AQP3 and AQP4 on basolateral membrane allow water movement into plasma

Question 30

what mechanism allows water to pass through AQP2

Answer 30

osmotic gradient from lumen to blood

Question 31

physiological action of oxytocin: major therapeutic effects

Answer 31

uterus, mammary gland (myoepithelial cells)

Question 32

physiological action of oxytocin: minor therapeutic effects

Answer 32

cardiovascular system (vasodilation), kidney (anti-diuresis), CNS (maternal behaviour)

Question 33

oxytocin on mammary gland

Answer 33

act on breast during lactation; myeopithelial cells contract to promote milk ejection (similar to prolactin)

Question 34

oxytocin on uterus

Answer 34

act on uterus at parturition; myometrial cells contract to promote delivery of baby; rhythmic contaction to increase local prostanoid production and dilute cervix

Question 35

what is oxytocin suppresed by

Answer 35

progesterone

Question 36

what is oxytocin enhanced by

Answer 36

oestrogen

Question 37

when does the uterus become more sensitive to oxytocin

Answer 37

as weeks of gestation increase (delivery nears)

Question 38

by which mechanism does the uterus become more sensitive to oxytocin

Answer 38

positive feedback

Question 39

oxytocin on "tend and befriend" female behavioural response to stress

Answer 39

tend: protect and care for children; befriend: seek out and receive social support; inhibitory effects on endocrine stress response; more stimulated by oestrogen than testosterone

Question 40

major clinical uses of oxytocin

Answer 40

induction of labour at term, prevention treatment of post-partum haemorrhage, faciliation of milk let-down, social responsiveness e.g. autism

Question 41

control of vasopressin: increased plasma osmolarity

Answer 41

increased plasma osmolarity → osmoreceptors in hypothalamus shrink → stimulates neurones which stimulate vasopressin secretion and feeling of "thirst" → vasopressin moves down to kidney → increases water reabsorption → plasma osmolariy returns to normal range

Question 42

control of vasopressin: blood pressure

Answer 42

low arterial BP (dehydration or hemmorhage) → baroreceptor (which inhibits vasopressin release) firing rate drops → inhibition reduced → vasopressin secretion increases → acts as vasoconstricor so blood pressure restored

Question 43

control of oxytocin: milk ejection

Answer 43

neuroendocrine reflec arc same as prolactin; neural afferent (to brain) neurones; endocrine efferent (to peripheral tissue) secretion

Question 44

oxytocin dysregulation

Answer 44

not essential; parturition and milk ejection effects induced/replaced by other means

Question 45

vasopressin dysregulation: low levels

Answer 45

constant loss of water (drink and urinate a lot) which causes diabetes insipidus

Question 46

where does diabetes insipidus come from: cranial

Answer 46

lack of vasopressin production

Question 47

where does diabetes insipidus come from: nephrogenic

Answer 47

kidneys resistant to vasopressin

Question 48

signs of diabetes insipidus

Answer 48

polydipsia (increased thirst), polyuria (large volumes of urine), hyper-osmolar (very dilute) urine

Question 49

vasopressin dysregulation: excessive levels

Answer 49

caused by certain tumours; too much water reabsorbed (syndrome of inappropriate ADH)