CVS 8: Sympathetic nervous and Renin-Angiotensin systems

Question 1

Which region do parasympathetic and sympathetic nerves come from?

Answer 1

Parasympathetic: Craniosacral
Sympathetic: Thoracolumbar

Question 2

What are baroreceptors and what effect do they have?

Answer 2

• pressure receptors
• increased baroreceptor firing leads to a decrease in sympathetic activity
• reduces hr and blood pressure

Question 3

Where are baroreceptors found?

Answer 3

Aortic arch

Carotid arteries

Question 4

Which neurotransmitter do parasympathetic nerves release?

Answer 4

Acetylcholine

Question 5

Where is ACh released and where might other neurotransmitter substances be released?

Answer 5

SYMPATHETIC:

1. Paravertebral sympathetic chain ganglion= ACh
2. Effector end= noradrenaline

PARASYMPATHETIC:

1. Paravertebral sympathetic chain ganglion= ACh
2. Effector end= ACh

Question 6

What are noradrenaline and adrenaline?

Answer 6

Catecholamines

Question 7

Where is noradrenaline synthesised?

Answer 7

Terminal varicosities (small nodules at the end of the sympathetic nerve)

Question 8

How is NA synthesised?

Answer 8

Tyrosine (enters cell) => L- DOPA => Dopamine (enters vesicle) => NA

Question 9

What are the exceptions to Sympathetic neurones releasing noradrenaline?

Answer 9

The adrenal medulla releases mostly adrenaline instead of Na.
Sweat glands release ACh

Question 10

How is NA released?

Answer 10

• granular vesicle fuses with varicosity membrane
• exocytic channel opens
• vesicle contents are expressed by exocytosis (requires ATP)
• reuptake of neurotransmitter
• biosynthesis to replenish neurotransmitter

Question 11

What are the two ways that NA can be removed from the cleft?

Answer 11

• go back to the neurone hat released it

- taken up by extra neuronal cells

Question 12

Name two enzymes responsible for the breakdown of the transmitter?

Answer 12

COMT (catechol-o-methyl transferase)

MAO (Monoamine oxidase)

Question 13

What are the two groups of effects of adrenoreceptors? Which receptor do they use?

Answer 13

1. Excitatory effect on smooth muscle- alpha adrenoreceptor mediated
2. Relaxant effect on smooth muscle + stimulatory effects on heart - Beta adrenoreceptor mediated

Question 14

Where are the three types of Beta receptors found?

Answer 14

1. Beta 1
   
   • cardiomyocytes
   • smooth muscle of the GI tract
2. Beta 2
   
   • Vasculature
   • Bronchi
   • Uterine smooth muscle
3. Beta 3
   
   • Fat cells (brown fat)
   • Possibly smooth muscle of GI tract
     THERMOGENESIS

Question 15

Where are the three types of Alpha receptors found?

Answer 15

1. Alpha 1 receptors- found post-synaptically (mostly on effector cells)
   
   • involved in mediating constriction of resistance vessels in response to sympathomimetic amines
2. Alpha 2 receptors- found on presynaptic nerve membrane
   
   • Activation by release transmitter causes -ve feedback INHIBITION of further transmitter release
   • some post synaptic on VSMCs=> vasoconstriction

Question 16

Explain how alpha 1 adrenoreceptors work

Answer 16

Gq-protein linked receptor

• when receptor is activated, Phospholipase C converts PIP2 to IP3
• IP3 causes IC stores of Ca2+ to be released
• Increase in IC Ca2+ causes muscle contraction

Question 17

Explain how Beta adrenoreceptors work

Answer 17

Gs- protein linked receptor

• activates adenylate cyclase
• increases IC levels of cAMP

Question 18

What are the two different effects Beta adrenoreceptors have dependent on the the of cell the receptor is found on?

Answer 18

SMOOTH MUSCLE and PLATELETS= cAMP is an inhibitor so it prevents activation, makes smooth muscle relax and prevents platelet activation
CARDIOMYOCYTES= cAMP activates the cells

Question 19

Explain how A2 receptors work***??????

Answer 19

Gi- protein linked receptor

• inhibit adnenylate cyclase
• reduce IC cAMP
• oppose the effects of Ca2+ because it isn’t released from IC stores

Question 20

What happens during anaphylaxis? And what can be administered to counteract this?

Answer 20

• Anaphylaxis= extreme allergic reaction, vasodilators released and bronchoconstriction
• Adrenaline administered

Question 21

Which receptors does adrenaline bind to?

Answer 21

a1, a2, B1, B2

Question 22

What is dopamine and which receptors does it bind to?

Answer 22

• precursor for catecholamines
• has some effect on a1 and B1 receptors
• has its own receptors in vasculature and the kidneys

Question 23

Name a synthetic catecholamine which is used to treat asthma. Which receptors does it bind to?

Answer 23

Isoprenaline- B1 and B2

Question 24

Name another synthetic catecholamine and state the receptor that it binds to

Answer 24

Phenylephrine

a1