Session 4

Question 1

What are the basic features of the parasympathetic nervous system?

Answer 1

• Long pre-ganglionic neurone and short post-ganglionic neurone
• Pre-ganglionic neurone is cholinergic
• Post-ganglion if neurone is cholinergic

Question 2

What is the effect of the SNS on the heart and which receptors are acted on?

Answer 2

• Increased heart rate and force of contraction

- Acts on beta1 receptors

Question 3

What effect does the PNS have on the heart and which receptor does it act on?

Answer 3

• Decreased heart rate

- Acts on M2 receptors

Question 4

What effects does the SNS have on airways and which receptors are acted on?

Answer 4

• Relaxes airways

- Acts on beta2 receptors

Question 5

What effects does the PNS have on the airways?

Answer 5

• Contracts the airway

- Acts on M3 receptors

Question 6

What effects does the SNS have on the pupils and which receptors are acted on?

Answer 6

• Dilates pupils

- Acts on alpha1 receptors

Question 7

What effects does the SNS have on sweat glands and which receptors are acted on?

Answer 7

• Localised secretion when alpha1 receptors are acted on

- General secretion when M3 receptors are acted on

Question 8

What effects does the PNS have on the pupils and which receptors are acted on?

Answer 8

• Constricts pupils

- Acts on M3 receptors

Question 9

What effects does the PNS have on sweat glands and what receptors are acted on?

Answer 9

No effects

Question 10

What effects does the SNS have on smooth muscle in the walls of arteries, arterioles and veins (excluding specialised vessels) and which receptors are used?

Answer 10

• Constriction of the smooth muscle causing vasoconstriction

- Via alpha1 adrenoceptors

Question 11

How is sympathetic outflow to blood vessels controlled?

Answer 11

Controlled from the brain stem via the vasomotor centres in the medulla oblongata using information from baroreceptors in the aortic arch and carotid sinuses

Question 12

What is the intrinsic heart rate (I.e. If all autonomic inputs are blocked)?

Answer 12

100bpm

Question 13

What causes the normal resting heart rate of ~60bpm?

Answer 13

Intrinsic rate is reduced because parasympathetic input dominates over sympathetic input at rest

Question 14

How is force of contraction of the heart controlled?

Answer 14

Sympathetic nerve fibres innervate ventricular cardiac myocytes to control force of contraction

Question 15

What are the basic features of the sympathetic nervous system?

Answer 15

• Thoracodorsal-lumbar outflow (T1-L2)
• Short pre-ganglionic neurone and long post-ganglionic neurone
• Pre-ganglionic neurone is cholinergic
• Post-ganglionic neurone is noradrenergic
• Synapse at the same level or a different level as the origin but not in the paravertebral chain