Lecture 8

Question 1

What is raised PCO2 called?

Answer 1

Hypercapnea

Question 2

What happens when there is an increase of carbon dioxide in the CSF?

Answer 2

There is a subsequent increase in hydrogen ions which causes an increase in ventilation to be stimulated to blow off the excess carbon dioxide and therefore reduce the hydrogen concentration

Question 3

When arterial PCO2 increases what crosses the brain-blood barrier?

Answer 3

Carbon dioxide, not hydrogen ions

Question 4

When is ventilation inhibited?

Answer 4

When there is an increase in arterial PO2 or a decrease in arterial PCO2/[H+] such as in hyperventilation. Also during swallowing to avoid aspiration of food or fluid.

Question 5

Where are the respiratory centres in the brain?

Answer 5

In the pons and the medulla

Question 6

Where do the nerves that supply the diaphragm originate?

Answer 6

C3-5

Question 7

What happens if the spinal cord is severed above C3?

Answer 7

A person will no be able to breath

Question 8

What happens if there is a loss of nerve enervation to the intercostal muscles?

Answer 8

A persons ability to breath will be reduced slightly but they will still be able to breath

Question 9

What is the DRG?

Answer 9

The dorsal respiratory group and it sends signals to the inspiratory muscles

Question 10

What is the VRG?

Answer 10

The ventral respiratory group and it sends signals to the expiratory muscles, the larynx, the pharynx and the tongue. Even though expiration is mostly passive the muscles of expiration, the larynx, the pharynx and the tongue have to have some tone in them to keep the airways open and to allow expiration to be smooth

Question 11

What are the respiratory centres controlled by?

Answer 11

Emotion via the lambic system in the brain
Voluntary over-ride via higher centre in the brain
Mechano-sensory input from the thorax such as the stretch reflex
Chemical composition of the blood detected by chemoreceptors

Question 12

Which is the most significant input to the respiratory centres?

Answer 12

The chemoreceptor input

Question 13

What are the two types of chemoreceptor?

Answer 13

Central chemoreceptors

Peripheral chemoreceptors

Question 14

Describe the central chemoreceptors

Answer 14

They are in the medulla and respond directly to changes in concentration of hydrogen ions in the CSF. They are the primary ventilatory drive in the body.

Question 15

Describe the peripheral chemoreceptors

Answer 15

These are carotid and aortic bodies that respond primarily to the concentration of hydrogen in the plasma and to PO2. They are the secondary ventilatory drive

Question 16

What is hyperventilation?

Answer 16

Increased ventilation, so taking long deep breaths

Question 17

In a healthy individual when do peripheral chemoreceptors work?

Answer 17

When there is a very significant fall in arterial PO2 or a very significant rise in hydrogen ion concentration

Question 18

What happens to ventilation during acidosis and alkalosis?

Answer 18

Acidosis - ventilation increases to blow of more CO2 to reduce hydrogen ion concentration
Alkalosis - ventilation decreases to increase the level of CO2 to increase the hydrogen concentration

Question 19

What are some common drugs that effect the respiratory centres?

Answer 19

Barbiturates and opioids depress respiratory centres and nitrous oxide blunts the peripheral chemoreceptors response to fallen arterial PO2.