Respiratory Physiology 5

Question 1

What does VENTILATORY CONTROL require?

Answer 1

Stimulation of the (skeletal) muscles of inspiration

Question 2

How does VENTILATORY CONTROL occur?

Answer 2

Via the phrenic (to diaphrgam) and intercostal nerves (to external intercostal muscles).

Question 3

Is VENTILATORY CONTROL subconscious or conscious?

Answer 3

SUBCONSCIOUS
HOWEVER can be subject to voluntary modulation

Question 4

What is the VENTILATORY CONTROL entirely dependent on?

Answer 4

signalling from the brain (sever spinal cord above origin of phrenic nerve (C3-5) breathing ceases)

Question 5

Respiratory centres have their rhythm modulated by…

Answer 5

1. Emotion (via limbic system in the brain)
2. Voluntary over-ride (via higher centres in the brain)
3. Mechano-sensory input from the thorax (e.g. stretch reflex).
4. Chemical composition of the blood (PCO2, PO2 and pH) – detected by chemoreceptors.

Question 6

What are the two classes of chemoreceptors?

Answer 6

CENTRAL
- medulla
- detects changes in H+ in CSF around brian
- Cause reflex stimulation of ventilation following rise in [H+] (driven by raised PCO2 = Hypercapnea)

PERIPHERAL
- carotid and aortic bodies
- respond primarily to PO2 and plasma H+ (less so to PCO2)
- secondary ventilatory drive

Question 7

ESSENTIAL EQUATION IN CENTRAL CHEMORECEPTORS

Answer 7

CO2 + H20 <—> H2CO3 <—> H+ + HCO3-

Question 8

What is ventilation reflexly inhibited by?

Answer 8

A decrease in arterial PCO2 (reduces CSF[H+]) (HYPERVENTILATION)
- DO NOT respond to direct changes in plasma [H+]

Question 9

What happens when ARTERIAL PCO2 increases?

Answer 9

CO2 crosses the blood-brain barrier NOT H+

Question 10

What do central chemoreceptors monitor?

Answer 10

The PCO2 indirectly in the cerebrospinal fluid

Question 11

NOT ALL LEARNING OUTCOMES

DO RESIT FLASHCARDS TOO!!!!