Neuroscience 10 - Autonomic reflexes

Question 1

Which part of the ANS has control on the heart rate at rest?

Answer 1

• The parasympathetic nervous system - as the intrinsic heart rate is 100-110bpm
• There is inhibition in the CNS of the sympathetic nerve

Question 2

What is the difference between the parasympathetic control of blood pressure and the sympathetic control?

Answer 2

• Parasympathetic control involves heart rate decrease

- Sympathetic control includes heart rate increase and dilation of vessels

Question 3

What is postural hypertension?

Answer 3

• There is pooling of blood in the lower limbs when we stand
• The reflex to raise blood pressure when it falls, involving the baroreceptor response is ineffective, so patients loose oxygen supply to the brain and faint.

Question 4

Summarise the pathway that occurs in the pupillary light reflex.

Answer 4

• Light is detected by the optic nerve
• Impulse goes to the pretectal nucleus, and then to the Edinger-Westphal nucleus.
• Ocularmotor nerve (3rd cranial nerve) takes the impulse to the ciliary ganglion (parasympathetic)
• The sphincter pupillae causes the pupil to constrict
• This is consensual, both eyes will react

Question 5

What neurotransmitter is used in pupillary constriction?

Answer 5

• Parasympathetic, so acetylcholine is used

Question 6

What drugs affect pupil diameter?

Answer 6

• Pilocarpine causes constriction (parasympathetic)

- Tropicamide causes dilation (sympathetic)

Question 7

What process should happen in the body following blood pressure drop when standing?

Answer 7

• Decreased baroreceptor firing
• Activation of SNS
• Increases noradrenaline production and also adrenaline production from the adrenal medulla.