Autonomic CVS Control

Question 1

Describe the sympathetic effect and identify the associated receptor of;

1. Eye pupil
2. Airways
   3 Heart
3. Sweat glands

Answer 1

1. Dilation- A1
2. Relax- B2
3. Increased rate and force of contraction- B1
4. Localised secretion- A1, Generalised secretion- M3

Question 2

Describe the parasympathetic effect and identify the associated receptor of;

1. Eye pupil
2. Airways
   3 Heart
3. Sweat glands

Answer 2

1. Contracts- M3
2. Contract- M3
3. Lower heart rate- M2
4. No effect

Question 3

What happens to heart rate if you denervate the heart, why?

Which nerve carries sympathetic impulses to heart from Ganglion

Answer 3

Beats faster, as it generates its own beat and is normally inhibited by Vagus nerve of PNS

Cardiac accelerator nerve

Question 4

Regarding Parasympathetic input to heart;

1. Where do postganglionic cells synapse
2. What trainsmitter do they release
3. What receptors are acted on
4. Name 1 effect on heart

Answer 4

1. On epicardial surface OR at SA/ AV node
2. Release ACh
3. M2 receptor
4. Decreased Chronotropy

Question 5

Regarding Sympathetic input to heart;

1. What does it innervate
2. What transmitter is released
3. What receptor is acted on? What other receptors are also present
4. Name 2 effects on heart

Answer 5

1. SA, AV node and Myocardium
2. Noradrenaline
3. B1 mainly, B2 and B3 also present
4. Positive Chronotropy and Inotropy

Question 6

How does Parasympathetic activity affect the Pacemaker Potential

Answer 6

1. Via M2 receptors, which are Gi coupled, so decreased amount of cAMP made
2. Less HCN channels activated, so slower pacemaker potential

Question 7

How does Sympathetic activity affect the Pacemaker Potential

Answer 7

1. Via B1 receptors, which are Gs coupled, so more cAMP made

2. More HCN channels activated, so faster pacemaker potential

Question 8

How does Noradrenaline increase Contraction Force

Answer 8

1. NA acts on B1 receptors in Myocardium, more cAMP, more PKA activity
2. Phosphorylation of Ca channels= More Ca influx during Plateau of AP-> Increased Ca uptake in SR
3. Positive Inotropy

Question 9

How are most vessels innervated, sympathetically or parasympathetically?

Give one example of an exception

Answer 9

Sympathetically, except specialised tissue such as erectile tissue

Question 10

What are the main receptors on vascular smooth muscle cells?

What other receptors are present? name 3 tissues where they’re found

Answer 10

Main are A1. B2 are also present

B2 can be found in blood vessels in Liver/ Myocardium/ Skeletal muscle

Question 11

Compare the amounts of Noradrenaline released when the vessels Dilate/ Constrict from their normal state? What is this state called

Answer 11

Normal= Vasomotor Tone

Tone-> Dilate= Les Noradrenaline released
Tone-> Constrict= More Noradrenaline released

Question 12

Circulating adrenaline has a higher affinity for which vascular receptor, compared to which one?

Compare the binding of Adrenaline to Vascular receptors at Physiological and Higher concentrations, and state the effect of on the vessels.

Answer 12

Higher affinity for B2, rather than A1

Physiological conc.-> Adrenaline prefers to bind to B2-> Dilation

Higher conc.-> Adrenaline also binds to A1->Constriction

Question 13

Explain the cellular mechanism of how B2 activation causes Vasodilation

Answer 13

More cAMP made-> more PKA activity-> Opens K+ channels and inhibits MLCK-> Smooth muscle relaxes

Question 14

Explain the cellular mechanism of how A1 activation causes Vasoconstriction

Answer 14

More IP3 made-> Increase in Intracellular Ca-> Smooth muscle contraction

Question 15

• What does active tissue produce
• What is the effect of these substances
• How do they compare to B2 activation for perfusion of skeletal and coronary muscle

Answer 15

• Metabolites (H+, K+, Increased pCO2)
• Vasodilator effect
• More important for perfusion of skeletal and coronary muscle than B2-receptor activation

Question 16

What are 2 types of receptors that communicate changes in CVS system to the brain?

What do they measure

Answer 16

Baroreceptors- Pressure

Atrial receptors- Volume

Question 17

Where are Baroreceptors found, what are they sensitive to

Answer 17

Aortic arch and Carotid Sinus

Sensitive to stretch

Question 18

What are Sympathomimetics, give 3 examples and when each can be used

Answer 18

Drugs that mimic the SNS (Alpha and Beta Agonists)

Adrenaline- Anaphylaxis/ Cardiac arrest
Dobutamine- Cardiogenic shock
Salbutamol- Bronchorelaxtion after asthma

Question 19

Give an example of an Alpha antagonist and its function

Answer 19

A1 antagonist to treat hypertension, as it causes vasodilation (Inhbits A1 receptors)

Question 20

Give 2 examples of Beta Antagonists used to treat Hypertension

Which one is non selective between B1 and B2, how does it reduce BP, what is 1 side effect causes by it?

Why is the other one less likely to cause this same side effect

Answer 20

Propranolol- Slows heart rate and reduces force of contraction, but can also cause Bronchoconstriction

Atenolol is cardio-selective