Physiology - Control of Respiration

Question 1

What 3 parts make up the neural control of respiration?

Answer 1

Pneumotaxic, apneustic and medullary rhythmicity area. Slide 5

Question 2

What is the main rhythm generator?

Answer 2

The medulla. Slide 5

Question 3

What is the Pre-Botzinger Complex?

Answer 3

A network of neurons and displays pacemaker activity. Slide 6

Question 4

What gives rise to inspiration when the rhythm is generated by the Pre-Botzinger Complex?

Answer 4

The Dorsal respiratory group of neurons are excited and create action potentials in bursts which lead to contraction of the inspiratory muscles. Slide 7

Question 5

What happens during active expiration during hyperventilation?

Answer 5

There is increased firing of dorsal neurones which excite the ventral respiratory group which does not happen in quiet breathing. This excites internal intercostals and abdominals. Slide 9

Question 6

How can the rhythm generated in the medulla be modified?

Answer 6

By the pneumotaxic centre when stimulated it terminates inspiration. Slide 10

Question 7

What happens if the pneumotaxic centre wasn’t stimulated?

Answer 7

Apneusis - Prolonged inspiration which brief expiration. Slide 10

Question 8

What are examples of Involuntary modifications of breathing?

Answer 8

Pulmonary stretch receptors (Herin-Breuer Reflex)
Joint receptors in exercise
Stimulation of Respiratory centre from the cerebral cortex
Cough reflex. Slide 13

Question 9

What are the factors that may increase ventilation during exercise?

Answer 9

Reflexes originating from body movement
Adrenaline release
Impulses from cerebral cortex
Increase in body temp.
Accumulation of CO2 generated from active muscles. Slide 16

Question 10

What receptors sense the values of gas tensions in the blood?

Answer 10

Chemoreceptors. Slide 20

Question 11

Where are the peripheral chemoreceptors and what do they sense?

Answer 11

They’re on the carotid bodies and aortic bodies.

They sense tension of O2, CO2 and H+ ions. Slide 21

Question 12

Where are the central chemoreceptors and what do they sense?

Answer 12

They are situated near the surface of the medulla and respond to the H+ conc. of the cerebrospinal fluid. Slide 22

Question 13

What substance is permeable to the blood brain barrier and why?

Answer 13

CO2, H+ ions are impermeable. Slide 22

Question 14

How does the central chemoreceptors detect H+ ion conc?

Answer 14

Since H+ ions cannot cross directly through the blood brain barrier, the CO2 that can reacts with water and ends up producing H+ ions. Slide 22

Question 15

What happens when the chemoreceptors sense an increase in the PCO2?

Answer 15

Increased ventilation. Slide 23

Question 16

What is important about patients with chronic CO2 retention in the hypoxic drive of respiration?

Answer 16

They must retain a partial hypoxic drive due to the CO2 retention and must not be treated the same with normal spO2 stats. Slide 25

Question 17

How is hypoxia caused in high altitudes?

Answer 17

Decreased partial pressure of inspired O2. Slide 27

Question 18

What are the acute responses and chronic adaptations to high altitudes hypoxia?

Answer 18

Acute: Increased cardiac output and hyperventilation
Chronic: Increased RBC production, increased number of capillaries and mitochondria. Slide 27+28

Question 19

What happens when the peripheral chemoreceptors sense an increase in H+ ion conc.?

Answer 19

They stimulate hyperventilation and that increases elimination of CO2 from the body which stops the generation of H+ ions in the body. Slide 29

Question 20

What is H+ ion drive of respiration important for?

Answer 20

The acid-base balance. Slide 29