endocrinology

Question 1

what is the difference between exocrine glands and endocrine glands?

Answer 1

exocrine glands maintain connecting cells between the surface epithelium and gland cell, in endocrine glands, these connecting cells are lost

Question 2

what is the main similarity between endocrine and neuronal cells?

Answer 2

both can be depolarised

Question 3

give an example of how cells in the endocrine system respond to depolarisation

Answer 3

the adrenal medulla responds to depolarisation to release noradrenaline/adrenaline

Question 4

explain the mechanisms of cell signalling over short distances

Answer 4

autocrine: hormonal signal acts back on the cell of origin/adjacent cell of same type
paracrine: hormonal signal carried to adjacent cell over a short distance via interstitial fluid

Question 5

explain the mechanisms of hormonal cell signalling over long distances

Answer 5

endocrine: carried to distant target cell via bloodstream
neurocrine: hormonal signal originates in a neurone and after axonal transport to bloodstream, is carried to distant cell

Question 6

what type of hormones are water soluble?

Answer 6

catecholamines, peptides/protein hormones

Question 7

explain the mechanism of action for water soluble hormones

Answer 7

1) hormone binds to receptor, activating G-protein + stimulates adenylyl cyclase
2) adenylyl cyclase converts ATP into cAMP
3) cAMP acts as a second messenger to activate protein kinases
4) activated protein kinases phosphorylate cellular proteins
5) phosphorylated proteins trigger cellular response

Question 8

what types of hormones are often lipid soluble?

Answer 8

steroid and thyroid hormones

Question 9

explain the mechanism of action of lipid soluble hormones

Answer 9

1) hormone diffuses into cell
2) activated receptor-hormone complex alters gene expression
3) newly formed mRNA directs synthesis of specific proteins on ribosomes

Question 10

what 3 factors are hormone levels determined by?

Answer 10

rate of production
rate of delivery
rate of degradation

Question 11

give the cellular roles of Ca2+

Answer 11

• neuromuscular excitability
• coagulation
• synaptic transmission
• second messengers
• regulation of gene transcription
• coordination of metabolic activity
• bone formation

Question 12

what are the cellular roles of phosphate?

Answer 12

• structure of membrane phospholipids
• energy metabolism
• protein phosphorylation
• genetic information
• bone formation

Question 13

where is parathyroid hormone made and what is its role?

Answer 13

made in the principle/chief cells

increases plasma Ca2+ and decreases plasma phosphate

Question 14

what are the three main target organs of parathyroid hormone?

Answer 14

bone, kidney, intestine

Question 15

what are the main effects of parathyroid hormone on its target organs?

Answer 15

• causes increased osteoclast activity in the bone
• causes increased calcium reabsorption and phosphate loss in the kidney
• increases calcitriol levels in the intestine

Question 16

what is the role of calcitriol? what is required for calcitriol formation?

Answer 16

promotes intestinal absorption of Ca2+ and PO43-. requires vitamin D as a precursor

Question 17

what are canaliculi?

Answer 17

small structures within osteons where calcium reabsorption occurs. a labile pool of calcium

Question 18

outline fast exchange of Ca2+ between bone and plasma

Answer 18

Ca2+ is moved from the labile pool in the canaliculi into the plasma by PTH activated Ca2+ pumps located in the osteocytic-osteoblastic bone membrane

Question 19

outline slow exchange of Ca2+ between bone and plasma

Answer 19

Ca2+ moved from stable fluid in mineralised bone into the plasma by PTH induced dissolution of bone

Question 20

what is calcitonin and where is it produced?

Answer 20

a peptide hormone produced by the parafollicular cells of the thyroid gland. it is secreted in response to high levels of Ca2+ and gastrin and causes decrease in plasma calcium and phosphate

Question 21

what do the hypothalamus and pituitary control as a functional unit?

Answer 21

• body growth
• reproduction
• milk secretion
• metabolism
• adrenal gland function
• thyroid gland function
• water metabolism
• puberty

Question 22

explain how the hypothalamic-pituitary axis is responsible for water homeostasis

Answer 22

ADH produced in hypothalamus -> transported down neurones to posterior pituitary -> ADH released into circulation

Question 23

what is the role of the anterior pituitary?

Answer 23

produce the 7 trophic hormones; which stimulate the release of other hormones

Question 24

where and how is growth hormone produced/inhibited?

Answer 24

anterior pituitary

stimulated by hypothalamic GHRH and inhibited by hypothalamic somatostatin

Question 25

how does growth hormone exert its effects?

Answer 25

exerted indirectly via insulin-like growth factors, secreted by liver and skeletal muscle