Endocrinology

Question 1

endocrine glands

Answer 1

cells that synthesise and secrete hormones into blood

Question 2

hormone

Answer 2

chemical secreted into blood, acts on specific target cells to regulate cellular function

Question 3

3 chemical classifications of hormones

Answer 3

peptides/ proteins 
- from DNA transcription and mRNA translation on RER
- exocytosis (hydrophilic)
steroids 
- from cholesterol 
- diffusion (lipophilic) 
biogenic amines 
- from tyrosine (aa) 
- diffusion (lipophilic), exocytosis (hydrophilic)

Question 4

mechanism of action of hydrophobic hormones

Answer 4

e.g. steroid, biogenic amines (thyroid) hormones
bind to intracellular receptors
alters transcription, more/ less protein produced

Question 5

mechanism of action of hydrophilic hormones

Answer 5

e.g. peptides, biogenic amines
binds and activates cell surface receptors
stimulates secondary messenger

Question 6

two types of endocrine control

Answer 6

homeostatic response - homeostatic function e.g. ADH, PTH

adaptive response - adapt to specific stimulus e.g. insulin

Question 7

regulating simple hormone response

Answer 7

involves one endocrine gland
regulated by circular response
e.g. ⬆ blood glucose, ⬆ pancreas insulin, glucose taken up by target cell, ⬇ blood glucose, pancreas stops releasing insulin

Question 8

regulating complex hormone response

Answer 8

involves action of two or more endocrine glands
regulated by
- long, indirect feedback loop - final hormone affects first endocrine secretion
- long, direct feedback loop - final hormone affects second endocrine secretion
- short feedback loop - second hormone affects first endocrine secretion
- negative feedback - hormone output reverses stimulus
- positive feedback - hormone output encourages stimulus

Question 9

anterior lobe of pituitary connection with hypothalamus

Answer 9

portal vessels transport hormones down pituitary stalk from hypothalamus to stimulate synthesis and secretion of hormones from anterior lobe

Question 10

anterior pituitary hormones

Answer 10

synthesised in anterior lobe
tropic hormones - target cell is another endocrine cell
- gonadotrophs e.g. FSH (gametogenesis), LH (steroidogenesis)
- thyrotrophs e.g. TSH (thyroid secretion)
- corticotrophs e.g. ACTH (adrenal cortex secretes cortisol and aldosterone)
non-tropic hormones - directly affect target cell
- somatotrophs e.g. GH (increase glucagon and insulin)
- lactotrophs e.g. PRL (mammary glands, Na+ kidney reabsorption)
all are trophic hormones - induce cell growth in target cell

Question 11

regulation of hormones from hypothalamus to anterior pituitary

Answer 11

controlled by tropic neurohormones of hypothalamus

Question 12

posterior lobe of pituitary connection with hypothalamus

Answer 12

neurosecretory neurons connect posterior lobe of pituitary to hypothalamus

Question 13

posterior pituitary hormones

Answer 13

synthesised in hypothalamus, stored and secreted in posterior lobe
magnocellular neurones synthesise
- ADH (water reabsorptionin kidney)
- oxytocin (uterine contractions)

Question 14

three ways of hormone excess

Answer 14

primary hypersecretion from final endocrine gland
secondary hypersecretion from middle endocrine gland
secondary hypersecretion from first endocrine gland

Question 15

functions of calcium (6)

Answer 15

calcium salt (calcium hyroxyapatite) in bone and enamel
trigger neurotransmitter release (exocytosis)
trigger hormonal secretion (exocytosis)
blood coagulation (cofactor)
enzymatic regulation (cofactor)
muscle contraction

Question 16

calcium homeostasis in intestine (absorption and secretion)

Answer 16

paracellular pathway - Ca2+ passively between epithelial cells of ileum
transcellular pathway - taken up into epithelual cell and actively released into blood in dueodenum and jejunum

Question 17

calcium homeostasis in kidney (filtration and reabsorption)

Answer 17

60% actively transported out of proximal tubule
30% diffuse out of loop of henle
9% actively transported out of distal tubule (PTH)
1% urine

Question 18

calcium homeostasis in bone (formation and resorption)

Answer 18

remodelling - bone is always formed and resorbed in trabecullar bone to ECF
osteoclast secrete enzymes to resorb bone, Ca2+ into blood regulated by PTH (activate) and calcitonin (inhibit)

Question 19

three primary cell types of trabecullar part of bone

Answer 19

osteoblast - form cells, secrete organic bone matrix (collagen, caclium hydroxyapatite)
osteocyte - mature bone cells
oestoclast - release hydrolytic enzymes to resorb bone, release Ca2+ into blood

Question 20

preprohormone

Answer 20

preprohormone -> prohormone -> peptide hormone

Question 21

PTH function (3 ways it does its function)

Answer 21

increase plasma [Ca2+] (stimulated by low [Ca2+])

stimulates Ca2+ reabsorption in kidney distal tubule
stimulates Ca2+ resorption in bone
stimulates 1-α-hydroxylase which catalyses 1,25 DHCC formation increases Ca2+ reabsorption in small intestine

Question 22

1,25 DHCC formation

Answer 22

metabolite of vitamin D3 formed in skin by UV radiation or from diet
PTH triggers 1-α-hydroxylase to form 1,25 DHCC

Question 23

1,25 DHCC function (3 ways it does its function)

Answer 23

increase plasma [Ca2+] (stimulated by low [Ca2+])

stimulates Ca2+ reasborption in kidney
stimulates PTH to bone resorb (but inhibits PTH gene expression so not out of control positive feedback)
stimulate Ca2+ absorption in intestine (stimulated by PTH)

Question 24

calcitonin formation

Answer 24

in thyroid glands

Question 25

calcitonin function (2 ways it does its function)

Answer 25

decrease plasma [Ca2+] (stimulated by high [Ca2+]) inhibits Ca2+ in bone resorption decreases Ca2+ reasborption in kidney

Question 26

osteoperosis

Answer 26

reduced bone density by bone resorption exceeding bone formation

Question 27

osteomalacia/ rickets

Answer 27

inadequate mineralisation of bone by vitamin D activity deficiency

Question 28

hypocalcaemia

Answer 28

insufficient Ca2+ by deficiency/ resistance to PTH

Question 29

pancreas endocrine/ exocrine

Answer 29

exocrine 98% - synthesise and secrete digestive hormones into central duct endocrine 2% - 3 cell types - α-cell secrete glucagon - β-cell secrete insulin - D-cell secrete somatostatin (aka GIH inhibit glucagon and insulin secretion)

Question 30

glucose taken into target cells when in fed state

Answer 30

muscle - glycogen liver - glycogen, triglyceride adipose cells - triglyceride every cell in body is target to insulin except liver and brain (able to take up glucose without insulin)

Question 31

insulin dependent diabetes mellitus (type 1)

Answer 31

insulin deficiency due to β-cell destruction

Question 32

insulin independent diabetes mellitus (type 2)

Answer 32

abnormal target cell response to insulin

Question 33

Cushing's syndrome

Answer 33

hypercortisolism (excess cortisol produced in zona fasciculata in adrenal glands) ``` excess lipolysis (fat redistribution to face) excess protein breakdown/ tissue wasting (weak, thin arms and legs) excess gluconeogenesis (diabetes) surpressed immune response ```

Question 34

Grave's disease

Answer 34

hyperthyroidism (excess thyroxine) primary hypersecretion edema causes exophthalmos (wide staring gaze, bulging eyes)