HPA Axis

Question 1

what does HPA stand for? and what does it do

Answer 1

hypothalamic pituitary axis -form a complex functional unit that serves to link between the endocrine and nervous system

Question 2

where is the location of the hypo. and pit and how does the hypo. communicate with them

Answer 2

• sella turcica (socket of bone) - A; synthesises tropic hormones wc sit in the median eminence, until they are released into the hypophyseal portal system to act on the target endocrine cells by stimulating or inhibiting them -P; hormones synthesised by the neurosecretory cells the paraventricular and supraoptic nuclei of the hypo, where they are then released into the posterior pit, via axons in the infundibulum towards the posterior pit, and then from then on released into the blood to act on distal targets

Question 3

origin of the ant and post pit? and number of hormones they both release

Answer 3

-A; (Rathke’s pouch) evagination of the oral ectoderm (primitive gut tissue) (6 hormones) -P ; (primitive brain tissue) originates from the neurectoderm (2 hormones)

Question 4

what is the posterior gland made of?

Answer 4

• axons and pituicytes

Question 5

what does the PP synthesis and by who? and whats their functions

Answer 5

• oxytocin and antidiuretic hormones - neurosecretory cells of the supraoptic and paraventricular nuclei - oxytocin ; upon suckling of milk stimulus , a let-down reflex is transmitted from the breast to the hypo. resulting in oxytocin to be released from the PP (via signals through the infundibulum) to the mammroy glands , where it binds to oxytocin receptors on the my-epithelial cells surrounding the mammy alveoli c it to contract to release milk into the duct. it is also involved in cervical contractions during childbirth bu activating oxytocin receptors on the uterine smooth muscle cells. -ADH ; binds to receptors at the distal tubular epithelium of the collecting ducts in kidney and the activated they c translocation of aquaporin water channels so more water is reabsorbed into the blood. it also induces vasoconstriction of bv wc increases peripheral vascular resistance - important in restoring bp in hypovolemic shock during haemorrhage

Question 6

what do we give pregnant women during birth

Answer 6

• Pitocin wc is oxytocin , it increases uterine tone and controls bleeding after birth

Question 7

ADH and alcohol

Answer 7

• alcohol inhibits ADH release from the PP so less water is reabsorbed and so explains why they need to pee more often, and they feel thirsty because osmoreceptors in the hypothalamus detect changes in osmolality in the blood and so increased feeling of thirst

Question 8

what tropic hormone and what do they act on?

Answer 8

• TRH = TSH (secretion of thyroid hormone from thyroid gland) -CRH = ACTH (stimulates glucocorticoid secretion from adrenal cortex) -PRH = Prolactin ( milk production in mammary and development of the gland) -GnRH = FSH, LH , testosterone ( progesterone and oestrogen production in women swell as initiates ovulation and egg production and tester. c sperm maturation -GHRH = act on liver + other tissue (growth of target cells and release of IGF from liver as well as metabolism) -GHIH = act on liver + other tissues *-PIH ( dopamine ) = prolactin

Question 9

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Answer 9

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Question 10

how are hypothalamic and pit pathways regulated

Answer 10

-negative feedback

Question 11

give example of negative feedback

Answer 11

-stress c hypothalamus. to release CRH ( median eminence then release into AP) wc synthesises ACT d CRH , this then is released into the blood and acts on the adrenal cortex c release og glucocorticoids (CORTISOL) wc has effect on tissues, then build up of it acts on the pit to stop secreting ACTH and hyp to stop secreting CRH

Question 12

what are the types of negative feedback loops use ACTH as example

Answer 12

• ultra short loop ; CRH inhibits hypothalamus - short loop ; ACTH inhibits hypothalamus - direct long loop; cortisol inhibits ACTH -indirect long loop; cortisol inhibits hypo CRH

Question 13

what is growth influenced by?

Answer 13

• environment -genetics -nutrion -hormones

Question 14

cells can undergo what imaeg

Answer 14

-necrosis / apoptosis - aplasia (v size/number) / hypertrophy (^ number) / hyperplasia (^ size)

Question 15

GH info

Answer 15

• made by AP - 191aa long peptide hormone, wc is cleaved before folding - in response to GH, cells in the liver produce IGF (insulin like growth factor) wc are important in bone and cartilage growth as well as metabolism - essential for growth especially in kids, stimulates long bone growth prior to the epiphyseal plate closure

Question 16

GH/IGF in adults an dkids

Answer 16

• kids; GH ;growth of long bone and widens it -adults; helps maintains muscle and bone mass and promotes healing and tissue repair as well as modulating metabolism and body composition

Question 17

why GH secreted?

Answer 17

• many factors including bgl and free fatty acids conc; increase in bgl and free fattyacids = v GH -v bgl + free fatty acids = ^GH - during onset of DEEP sleepGH released so don’t interrupt babies sleep and kids -rapid eye movement REM sleep, light sleep, inhibits GH secretion -stress (surgery fever, trauma) increase GH secretion - exercise ^ GH release -Ghrelin also increases the production of the growth hormone

Question 18

obesity and starving is GH released or not?

Answer 18

• obesity = decreased -starving = increased

Question 19

how is GH regulated in terms of negative feedback mechanisms? and which hormones mediate it and how

Answer 19

• long loop both indirect and direct (IGF inhibits release of GHRH + stimulates somatostatin from hypothalamus + inhibits the action GHRH in the anterior pituitary ) - short loop just GH and c inhibition of itself and stimulation of somatostatin

Question 20

how does GH exert effect on cells?

Answer 20

• binds to GH receptor and can bind to IGF-1 receptor wc is linked to a JANUS KINASE, a member of the cytokine receptor family and c phosphorylation of target proteins and alter their function) - in adipose tissue c ^ rate of lipolysis (catabolic effect) - in other tissue c ^ rate of protein synthesis (anabolic effect) - can also bind to receptors in the signalling pathways that activate transcription factors to increase product of IGFs

Question 21

what are the types of IGF

Answer 21

• IGF1 = major growth in adults -IGF 2 =growth in foetus

Question 22

IGF

Answer 22

• insulin like growth factor -work on IGF receptors and modulate ; hypertrophy, hyperplasia, increase rate of protein synthesis And rate of lipolysis -fucntions are paracrine, endocrine and autocrine

Question 23

what receptors can IGF bindsand insulin to

Answer 23

• INSULIN; insulin receptor generating a metabolic effects / But can bind to hybrid receptor and c metabolic and mitogenic pathway / also IGF1 receptor c mitogenic effects -IFG1 ; bind to IGF1 receptor c mitogenic effects and hybrid receptor cmitoenic effects -IGF2; binds to IGF2 receptor wc has no kinase activity

Question 24

other hormones that influence growth

Answer 24

-Insulin = enhance somatic growth, interact with IGF receptors -Thyroid hormones = promote CNS development and enhance GH secretion -Androgens = accelerate pubertal growth and increase muscle mass and promote closure of epiphyseal growth plates -oestrogen = decreases somatic growth,promotes closure of epiphyseal plates -glucocorticoids = inhibit somatic growth