PHYSIOLOGY OF GROWTH

Question 1

outline apoptosis during foetal development?

Answer 1

webs between fingers are removed
organs are hollowed out
happens in tissues with high cell turnover e.g. skin, GI tract

Question 2

what is the extrinsic pathway of apoptosis?

Answer 2

begins outside a cell, when conditions in the extracellular environment determine that a cell must die

Question 3

what is the intrinsic pathway of apoptosis?

Answer 3

begins when an injury occurs within the cell and the resulting stress activates the apoptotic pathway.

Question 4

what are caspases?

Answer 4

a family of cysteine proteases that serve as primary effectors during apoptosis to proteolytically dismantle most cellular structures

Question 5

when does foetal growth have the highest rate?

Answer 5

16-20 weeks as new protein is laid down

Question 6

how does ageing affect homeostasis?

Answer 6

the sensitivity of the hypothalamus to feedback regulators begins to decline. This results in a progressive loss of homeostasis and eventually, disruption of appropriate hormone production and an inability of the hypothalamus to appropriately regulate its target tissues

Question 7

outline how ageing affects the systems in the body?

Answer 7

decline in CVS system due to reduced blood flow and arteriosclerosis

reduced elasticity of lungs and decreased function

decreased muscle tone in urinary system and decreased GFR

loss of elasticity in skin - wrinkles

reduced sensitivity and responsiveness of immune system

impairment of coordination, memory and intellectual function

decreased GI muscle tone = reduced peristalsis

decreased in hormone production and sensitivity

decline in bone deposaition = decreases in motility

reduction in muscle mass and strength

Question 8

what is somatotropin?

Answer 8

growth hormone

Question 9

where is somatotropin produced?

Answer 9

anterior lobe of pituitary

Question 10

how do IGF levels vary in life?

Answer 10

low at birth, tend to increase slowly with age, peak following puberty and during the adolescent growth spurt in height, and then decrease as growth rate slows and adult stature is achieved

Question 11

how does gender affect growth?

Answer 11

boys tend to reach a higher absolute number In height but girl tend to reach their peak in height change at the age of 13 compared to boys at 15

Question 12

when does the reproductive tract fully develop?

Answer 12

at pubtery as it is driven by sex hormones

Question 13

where is growth hormone releasing hormones released from?

Answer 13

hypothalamus

Question 14

how does GHRH stimulate GH release?

Answer 14

GHRH is released by the hypothalamus into the hypophyseal portal system where it travels to the anterior pituitary. GHRH binds to somatotropin cells, stimulating them to release GH

Question 15

what’s the effect of growth hormone?

Answer 15

it stimulates cellular metabolism which leads to tissue growth

Question 16

what is somatomedin C?

Answer 16

insulin-like growth factor 1

Question 17

where is somatomedin C released from?

Answer 17

the liver

Question 18

what does somatomedin C do?

Answer 18

binds to insulin-like growth factor 1 receptors and insulin receptors to promote cellular metabolism, prevent cell death and increase cell division, mostly in muscles and bones

Question 19

what inhibits GHRH release?

Answer 19

high levels of GHRH in the blood

Question 20

what inhibits GH release?

Answer 20

somatomedin signal to anterior pituitary to stop releasing GH

Question 21

what blocks GHRH from acting on somatotrophin cells?

Answer 21

somatostatin (growth hormone inhibiting hormone) - produced from hypothalamus after signalling from GH and somatomedin

Question 22

when does GHRH levels peak?

Answer 22

1 hour after you fall asleep

Question 23

outline glucocorticoids effects on growth?

Answer 23

they inhibit growth by enhancing beta-adrenergic responsiveness in hypothalamic somatostatin neurons.

Question 24

how are T3 and T4 important for growth?

Answer 24

they promote long bone growth and are necessary for normal brain development

Question 25

when does thyroid hormone secretion start?

Answer 25

about week 16

Question 26

what happens to a child if there is a thyroid deficit?

Answer 26

slow bone growth rate and cretinism

Question 27

what is cretinism?

Answer 27

severe physical and mental retardation

Question 28

how are babies checked for hypothyroidism?

Answer 28

with the Guthrie test (heel prick test)

Question 29

what is responsible for limiting long bone growth at the end of puberty?

Answer 29

epiphyseal fusion

Question 30

what is achondroplasia?

Answer 30

a common form of dwarfism in humans (autosomal dominant)

Question 31

what’s the pathophysiology of achondroplasia?

Answer 31

a mutation in the fibroblast growth factor receptor 3 gene results in decreased endochrondrial ossification, inhibited proliferation of chrondrocytes and decreased cellular hypertrophy and decreased cartilage matrix production = overall, epiphyseal plates closer early

Question 32

what’s the average height for m and f who have achondroplasia?

Answer 32

m= 125cm
f= 120cm

Question 33

what is acromegaly?

Answer 33

a rare condition where the body produces too much growth hormone, causing body tissues and bones to grow more quickly.

Question 34

what are the symptoms of acromegaly?

Answer 34

enlargements of lipds/nose/tongue, enlargement of liber, enlargement of hands and feet, skull growth, prognathism, thickened skin, headache, hypertension, increased sweating

Question 35

how do we test for acromegaly?

Answer 35

glucose suppression test -
doctor will measure your blood glucose and GH level
You’ll then drink 75 g of a glucose drink. Doctor will test Gh and glucose levels 30, 60, 90, and 120 minutes after you’ve had the glucose drink.
If your GH level doesn’t drop to <1 ng/mL you have acromegaly. (Your GH level should respond to so much glucose by dropping)

Question 36

what is the cause of pituitary dwarfism?

Answer 36

GH deficiency, under secretion of pituitary hormones (infections, pituitary tumours, head trauma)

Question 37

what’s the cause of Laron dwarfism?

Answer 37

mutations in the GHR gene so it becomes unresponsive to GH and results In retardation of growth

Question 38

how do you treat pituitary dwarfism?

Answer 38

regular injections of synthetic human growth hormone before a child’s growth plates have joined together.

Question 39

how do you treat Laron dwarfism?

Answer 39

subcutaneous injections of insulin-like growth factor 1

Question 40

how can you treat acromegaly?

Answer 40

transsphenoidal surgery; a procedure in which all or part of a pituitary tumor is removed.