Catecholamines

Question 1

How is dopamine made?

Answer 1

1. Begins with the amino acid tyrosine
2. Converted to dihydroxyphenylalanine
   Catalyzed by tyrosine hydroxylase (this is the rate limiting step)

Question 2

How is epinephrine made?

Answer 2

Dopamine is converted to norepinephrine and this is converted to epinephrine

Question 3

Where does epinephrine come from?

Answer 3

All of the epinephrine in the blood comes from the adrenal medulla (80% of all AM secretions)

Question 4

Where does norepinephrine come from?

Answer 4

Norepinephrine comes from two sources:
Adrenal medulla
Postganglionic sympathetic neurons

Question 5

How are catecholamines stored?

Answer 5

Catecholamines are stored in secretory vesicles released via exocytosis

Question 6

How are catecholamines transported in the blood?

Answer 6

Circulate freely in the blood

Question 7

How are catecholamines metabolised?

Answer 7

Metabolized by liver and kidneys

Question 8

What is the half life of catecholamines?

Answer 8

Very short plasma half-life: 1 to 3 minutes

Question 9

Does Epinephrine and norepinephrine from adrenal medulla have the same effects as direct stimulation via sympathetic nerves.

Answer 9

Yes However, effects last 5 to 10 times longer (must be cleared from blood but thats still only 1-3 min)

Question 10

Neurones are adrenergic if they secrete …………….. such as:

Answer 10

norepinephrine

Postganglionic sympathetic neurons are adrenergic
Types of adrenergic receptor:
Alpha (α) adrenergic receptors 
Beta (β) adrenergic receptors
Sub-groups: α1, α2, β1, and β2

Question 11

Cardiac cells only have what type of neurone?

Answer 11

beta (adrenergic)

Question 12

Stimulation of alpha adrenergic neurones leads to…

Answer 12

Vasoconstriction 
Pupil dilation
Intestinal relaxation 
Pilomotor contraction 
Bladder sphincter contraction

Question 13

Stimulation of Beta one adrenergic neurones leads to…

Answer 13

Increase HR

Increase contractility

Question 14

Stimulation of Beta two adrenergic neurones leads to…

Answer 14

Vasodilation
Bronchodilation
Glycogenolysis
Lipolysis

Question 15

What kind of cell receptor do catecholamines bind to?

Answer 15

G-protein coupled

Question 16

What kind of pathways do catecholamines activate?

Answer 16

Adenyl cyclase
Phospholipase C, IP3, and DAG
Ion channels

Question 17

How does cAMP alter gene expression?

Answer 17

Catalytic subunit of protein kinase A enters nucleus
Binds to cAMP-response element binding protein (CREB) and phosphorylates
CREB-P binds to CRE and changes gene expression.

Question 18

What is the effect of SNS activation on arterioles of the intestine and muscle?

Answer 18

Intestine: αR stimulate smooth myocytes of bv = vasoconstriction
Muscles: β2R inhibit smooth myocytes of bv = vasodilation

Question 19

Why does the release of catecholamines mobilise fatty acids?

Answer 19

Thus brain functions optimally and muscles can carry animal away from danger

Question 20

What hormone is stimulated by catecholamines?

Answer 20

Hormone sensitive lipase

Question 21

What has more of a metabolic effect, epinephrine or norepinephrine?

Answer 21

Epinephrine has a 5–10 times greater metabolic effect than norepinephrine

Question 22

What has more of a cardiac effect, epinephrine or norepinephrine?

Answer 22

Epinephrine has a greater effect on beta receptors (cardiac stimulation)

Question 23

What has more of an effect on blood vessels, epinephrine or norepinephrine?

Answer 23

Norepinephrine has a more profound effect on blood vessels
Increases total peripheral resistance
Raises blood pressure