Intro to Endocrine

Question 1

what is an endocrine hormone

Answer 1

a hormone that travels through the blood to a target far away

Question 2

what is a paracrine hormone

Answer 2

one which acts locally to site of synthesis e.g. histamine

Question 3

what is an autocrine hormone

Answer 3

a hormone which acts on the same cell it was synthesised in e.g. cytokines

Question 4

what is an exocrine hormone

Answer 4

a hormone which is released through ducts to the external environment. e.g. saliva and bile

Question 5

how does a neuron release to trigger target cell

Answer 5

a neurotransmitter

Question 6

where does a neuroendocrine nerve release its neurotransmitter

Answer 6

into the bloodstream

Question 7

how can the same hormone have different response in different tissues

Answer 7

different receptors for the same hormone

Question 8

what are the 3 classifications of endocrine hormones

Answer 8

peptide, amine and steroid

Question 9

what amino acids are the majority of amine hormones derived from

Answer 9

tyrosine

Question 10

what is the only amine hormone to not be derived from tyrosine, what is it derived from

Answer 10

melatonin, from tryptophan

Question 11

what are steroid hormones derived from

Answer 11

cholesterol

Question 12

2 precursors of peptide hormone

Answer 12

preprohormone and prohormone

Question 13

how is preprohormone turned into prohormone

Answer 13

signal sequence on prepro causes it to be transported into ER lumen where the signal sequence is cleaved to leave a prohormone

Question 14

how is the prohormone turned into hormone

Answer 14

after passing through the Golgi apparatus, enzymes in the vesicles cleave off the fragment to leave a hormone

Question 15

what is the clinical significance of the prohormone –> hormone fragment

Answer 15

it is exocytosed with the hormone and so levels of it can be detected in the blood. for example, in diabetes measuring levels of serum insulin would not be effective as some of that insulin would be from medication, whereas C-peptide tells you how much have been produced

Question 16

what is the fragment of insulin called

Answer 16

C-peptide

Question 17

how is a peptide hormone store in the cell until required

Answer 17

in vesicles as hormone + fragments

Question 18

where is the preprohormone produced

Answer 18

by the ribosomes (protein)

Question 19

what is co-secretion

Answer 19

when the hormone and its fragments are exocytosed together

Question 20

why would levels of C-peptide be higher than the insulin level

Answer 20

because insulin is metabolised faster than C-peptide so doesn’t remain in bloodstream as long

Question 21

how much higher is the C-peptide level than insulin

Answer 21

about 5 times

Question 22

what are the water soluble hormone types

Answer 22

peptide and amine

Question 23

what mechanism do peptide hormones use to act on target cells

Answer 23

binding to surface recptors, usually either GPCR or tyrosine kinase linked

Question 24

how do GPCR stimulate action in cell

Answer 24

opening/closing ion channels or activating a second messenger to phosporylate proteins or alter gene expression

Question 25

why is water solubility a benefit for a hormone

Answer 25

easily dissolves in blood and makes transport easy

Question 26

how do tyrosine kinase receptors stimulate action in the cell

Answer 26

through altering gene expression

Question 27

which receptor response is faster

Answer 27

GPCR

Question 28

two subtypes of tyrosine derived amine hormones

Answer 28

catecholamines and thyroid hormones

Question 29

dopamine, NoraE and E are what type of hormones

Answer 29

amine --> tyrosine --> catecholamine

Question 30

what distinguishes catecholamines and thyroid hormones

Answer 30

solubility: catecholamines are water soluble

Question 31

solubility of steroid hormones

Answer 31

lipid soluble (cos made from cholesterol)

Question 32

why can't steroid hormones be stored in cells

Answer 32

because they are lipophilic and so can't be retained by a lipid membrane

Question 33

how are steroid hormones transported in blood

Answer 33

bound to albumin

Question 34

what is the benefit of steroid hormones being bound to carrier proteins in the blood

Answer 34

solubises them in blood and protects them from enzymatic degradation --> increases half life above other hormone types

Question 35

examples of steroid hormones

Answer 35

aldosterone, cortisol, estrogen and vit D3

Question 36

where are steroid hormone target cell receptors

Answer 36

inside the cell cytoplasm or nucleus, because they are lipid soluble

Question 37

how does a steroid hormone trigger a cellular response

Answer 37

through cytoplasm/nucleus/secondary messengers activating or repressing gene function to effect protein synthesis

Question 38

does the biological effect of steroid hormones follow quickly or slowly after hormone release

Answer 38

slowly, hours to days

Question 39

what other hormones require carrier proteins in blood

Answer 39

amine --> tyrosine --> thyroid

Question 40

in what state are lipophilic hormones transported across membranes

Answer 40

unbound

Question 41

what law tells us that as free hormone leaves the plasma more hormone is released from carriers

Answer 41

Law of Mass Action

Question 42

why do peptide and catecholamine hormones have short half lives

Answer 42

because they are unbound in blood and so are vulnerable to enzymatic degradation

Question 43

receptor response to prolonged low hormone level

Answer 43

increased sensitivty to hormone

Question 44

receptor response to prolong high hormone level

Answer 44

decreased sensitivity to hormone

Question 45

what is a permissive effect

Answer 45

when the presence of one hormone enhances the effect of another

Question 46

what hormone enhances the lypolysis of epinephrine

Answer 46

thyroid hormone

Question 47

how does thyroid hormone have its permissive effect

Answer 47

by increasing epinephrine receptor synthesis

Question 48

what is an anatgonistic effect

Answer 48

when the presence of one hormone reduces the effect of another

Question 49

what hormone reduced insulin response

Answer 49

growth hormone

Question 50

how does growth hormone reduce insulin response

Answer 50

by reducing the number of insulin receptors

Question 51

why is hormone monitoring done in 24hours

Answer 51

because hormone levels vary alot through the day, so a single snapshot, as from a blood test, may not give an accurate picture