catecholamines

Question 1

where are epinephrine and noreprinephrine produced

Answer 1

in the adrenal medulla

Question 2

describe how epinephrine and noreprinephrine are synthesized

Answer 2

• beings with the amino acid tyrosine
• converted to dihydroxyphenylalanine
• catayzed to tyrosine hydroxylase (rate limiting step)
• converted to dopamine then noreprinephine then eprinephrine

Question 3

is adrenaline a water soluble or lipid soluble hormone.

Answer 3

water soluble - needs to have a short half life and wok quickly (doesnt need transport proteins)

Question 4

where does epinephrine come from

Answer 4

• all of the epinephrine in the blood comes from the adrenal medulla

Question 5

where does noreprinephrine come from

Answer 5

• adrenal medulla
• postganglionic sympathetic neurons

Question 6

explain why continual secretion of adrenaline is important for sympathetic tone

Answer 6

• continuous release of adrenaline from adrenals allows for modification of sympathetic tone. for example, continual secretion of adrenaline keeps the arterioles constricted to a 50% diameter so that in case of increased tone they can constrict more or in decreased tone they can relax more

Question 7

explain the kinetics of catecholamines

Answer 7

• stored in secretory vesicles
• release via exocytosis
• circulate freely in the blood
• metabolised by liver and kidneys
• very short plasma half life (1-3 minutes)
• urinary excretion of unmetabolised epinephrine and norepinephrine

Question 8

explain the relationship between the nervous system and the adrenal medulla

Answer 8

• pre ganglionic sympathetic neurons carry action potential to adrenal medulla
• adrenal acts as sympathetic ganglion and is equivalent to a post ganglionic sympathetic neuron

Question 9

neurons that secrete acetylcholine are

Answer 9

cholinergic
- neruons with cell bodies in the CNS are generally cholinergic

Question 10

neurons that secrete norepinephrine are

Answer 10

adrenergic
- post sympathetic neurons are adrenergic

Question 11

what are th receptors types of adrenergic receptors

Answer 11

alpha 1/2 and beta 1/2
some cells can have both

Question 12

what do alpha 1 receptors do

Answer 12

• vasconstrction
• pupil dilation
• intestinal relaxation
• pilomotor contraction
• bladder spincter contraction

Question 13

what do beta 2 receptors do

Answer 13

• increase HR
• increase heart contractility

Question 14

what do B2 receptors do

Answer 14

• vasodilation
• bronchodilation
• glycogenolysis
• lipolysis

Question 15

what do stimulated alpha 2 receptors do

Answer 15

• sedation and anaesthesi

Question 16

describe typical signal transduction of catecholamines

Answer 16

• bind to receptors
• activate second messengers
• often G protein coupled
• multiple pathways from here: adenyl cyclase, phospholipase C, IP3 and DAG
• Ion channels

Question 17

wht are the metabolic effects of catecholamines

Answer 17

idea is to increase the amount of readily availible energy substrates
- mobilise glucose
- mobilise fatty acids

thus brain functions optimally and muscles can carry animal away from danger
- increase glycogenolysis
- and gluconeogenesis

Question 18

animals that are stress will show what on blood work, why?

Answer 18

• hyperglycemia
• because epinephrine has optimised glucose use and glycolysis/gluconeogenesis in the body

Question 19

what is the importance of medullary epinephrine

Answer 19

• metabolic stimulus (epinephrine has 5-10x greater metabolic effect than noreprinephrine
• epinephrine has greater effect on beta receptors
• epinephrine acts on beta 2 receptos causing vasodilation while noreprinephrine acts on alpha receptrs causing vasoconstriction

Question 20

why are noreprinephrin and epinephrine important but different in function

Answer 20

• noreprinephrine has a more profound effect on blood vessels while epi has more effect on heart
• one raises blood pressure, other raised cardiac output
• important to have different sources for these