Communication and receptors

Question 1

steroid secretion

Answer 1

ovaries, testes , adrenal glands

Question 2

peptide secretion

Answer 2

hypothalamus
thyroid gland
pancreas

Question 3

amine hormone secretion

Answer 3

thyroid gland
adrenals

Question 4

hwo does communication between glands and other tissues occur

Answer 4

by the secretion of a hormonne into the bloodstream and a bulk transport to a target site

Question 5

how is specificy of signalling achieved

Answer 5

by chemically distinct hormones
specific receptors for each hormone and distint distribution of receptors across target cells

Question 6

examples of chemical signalling

Answer 6

autocrine
paracrine
endocrine

Question 7

autocrine

Answer 7

cell signals to itself

Question 8

paracrin e

Answer 8

cell signals to nearby neighbours

Question 9

endocrine

Answer 9

cell signals via molecules transported by the blood to taregt distant cells

Question 10

are amines hydrophilic or hydrophoic

Answer 10

hydrophilic

Question 11

how are amines transported

Answer 11

mainly free in plasma

Question 12

amines storage and reease

Answer 12

stored in vesicles, released in response to stimuli by ca2+ dependant exocytosis

Question 13

are peptides hydrophilic or phobic

Answer 13

philic

Question 14

how are peptides transported

Answer 14

mianly free in plasma

Question 15

peptides storafe and release

Answer 15

stored in vesicles
released in response to stimuli by ca2+ dependant exoctosis

Question 16

are steroids philic or phobic

Answer 16

phobic

Question 17

how are steroids transported

Answer 17

mainly bound to plasma proteins

Question 18

how are steroids synthesised and secreted

Answer 18

upon demand

Question 19

solubility in plasma of steroids, thyroxine and triiodothyronine

Answer 19

relatively insoluble

Question 20

effect of carrier proteins

Answer 20

increase amount transported in blood
provide a reservoir of hormone
extend half-life of the hormone in the circulation (contributing to a long duration of action)

Question 21

important general carrier proteins

Answer 21

albumin – binds many steroids and thyroxine
transthyretin – binds thyroxine and some steroids

Question 22

proteins and peptides solubility in plasma

Answer 22

soluble
do not require carrier proteins

Question 23

important specific carrier proteins

Answer 23

cortisol-binding globulin (CBG) – binds cortisol in a selective manner (also some aldosterone)

thyroxine-binding globulin (TBG) – binds thyroxine (T4) selectively [also some triiodothyronine (T3)]

sex steroid-binding globulin (SSBG) – binds mainly testosterone and oestradiol

Question 24

rate of elimination

Answer 24

amines e.g. adrenaline - t½ ~ seconds
proteins and peptides - t½ ~ minutes
steroids and thyroid hormones - t½ ~ hours to days due to extensive protein binding that suppresses elimination

Question 25

what are gpcrs activated by

Answer 25

amines and some proteins/peptides

Question 26

what are receptor kinases activated by

Answer 26

some proteins / peptides

Question 27

nuclear receptor activation

Answer 27

subdivided into class 1, class 2 and a hybrid class

class 1 - activated by many steroid hormones – in the absence of activating ligand these are mainly located in the cytoplasm bound to inhibitory heat shock proteins HSP) – move to the nucleus when activated

class 2 - activated mostly by lipids – constitutively present in the nucleus

hybrid class – activated by thyroid hormone (T3) and other substances – similar in function to class 1