L8: Dive Reflex Physiology

Question 1

What happens to the heart rate during the dive reflex?

Answer 1

Bradycardia

Question 2

What happens to the blood pressure during the dive reflex and explain why.

Answer 2

Despite increase in heart rate, arterial pressure during diving is usually maintained or even elevated by an increase in total peripheral resistance

Question 3

Where are the carotid bodies located?

Answer 3

Close to the bifurcations of the common carotid arteries

Question 4

What artery supplies the carotid artery?

Answer 4

Occipital artery

Question 5

Where are aortic bodies located?

Answer 5

Scattered between arch of aorta and pulmonary artery

Question 6

Describe type I cells (glomus) of the carotid body

Answer 6

Sensitive to local changes in PO2, PCO2 and pH.
Contains cytoplasmic granules (ACh, DA).
Closely associated with both myelinated and unmyelinated afferent fibres.

Question 7

Describe type II cells (sustentacular) of the carotid body

Answer 7

Type II cells wrap around the glomus (type I cells) and nerve endings. Contains no cytoplasmic granules. And may have a neuromodulatory role (controlling gain)

Question 8

Afferent information from the peripheral chemoreceptors is sent via:

Answer 8

Carotid sinus nerve -> glossopharyngeal nerve (Cranial nerve IX) to the NTS.

Aortic body: Joins the vagus (Cranial nerve IX) to the NTS

Question 9

Stimulation of carotid bodies cause:

Answer 9

Hyperventilation, increased arterial pressure