L4 - Control of Respiration

Question 1

How is breathing regulated?

Answer 1

Automatic, rhythmical process
Basic rhythm is generated by centres in the medulla
Inputs from various regions act to modify the respiratory patterns

Question 2

How can breathing be altered consciously?

Answer 2

Hyperventilation and breath holding

However, these are temporary and can be overridden

Question 3

How is the inspiration period generated?

Answer 3

Activity in hypoglossal nerve matches Pre-Botzinger complex output
Every few seconds a period of high activity in the neurones
This pattern is mimicked in the 12th cranial nerve

Question 4

What 3 types of pattern output can the Pre-Botzinger complex generate?

Answer 4

Eupneic – standard normal breathing
Sigh – increased intensity and magnitude
Gasp – short, decreased magnitude and intensity (when a lack of oxygen)

Question 5

What are the cell types of the Pre-Botzinger complex?

Answer 5

Two classes of neurones, pacemaker cells and non-pacemaker cells
Pacemaker cells can demonstrate spiking and bursting forms of activity
- Spiking – slow depolarisation up to threshold, activation of Na leak current
- Bursting – activation of persistent Na current
Each neuron goes through a cycle of spiking then bursting

Question 6

What is NALCN and where is it found?

Answer 6

Sodium leak channel found in the Pre-Botzinger complex

It contributes to the depolarisation phase

Question 7

What is the role of potassium in the Pre-Botzinger complex?

Answer 7

Background potassium conductance determines starting membrane potential
3mmol/l to 8mmol/l potassium outside the cell will lead to cell depolarisation

Question 8

What are the two different types of pacemaker cells?

Answer 8

Split depending on bursting activity sensitivity to cadmium
Neurones relying on ICAN for bursting are cadmium sensitive
Neurones relying on INaP for bursting are cadmium insensitive

Question 9

The transition to bursting activity depends on?

Answer 9

Two types of inward current

• Persistent sodium current (INaP)
• CAN cation current (ICAN+)

Question 10

What are the effects of hypoxia on the Pre-Botzinger complex?

Answer 10

1. Normal eupneic breaths (autonomous spiking neurones and CS pacemakers)
2. Deeper breaths, sighs, to bring more oxygen in (CS pacemakers)
3. Period of inactivity followed by gasping phases

Question 11

What are the two medullary centres?

Answer 11

Dorsal and ventral respiratory group

Question 12

What does the dorsal respiratory group control?

Answer 12

Controls inspiration by sending signals to the inspiratory muscle
Spontaneously active – period of activity – shuts off – period of activity

Question 13

What does the ventral respiratory group control

Answer 13

Controls inspiration and expiration
Inactive during quiet respiration
Helps control forceful inspiration and expiration

Question 14

What does the pons control?

Answer 14

The pons send stimuli to the medulla to regulate rate and depth of breathing

Question 15

What are the 2 centres of the pons?

Answer 15

Penumotaxic and apneustic centre

Question 16

What does the pneumotaxic centre control?

Answer 16

Increases the rate by shortening inspiration

Inhibits inspiratory centre

Question 17

What does the apenustic centre control?

Answer 17

Increases the depth and reduces the rate by prolonging inspirations
Stimulates inspiratory centre

Question 18

What are the two main respiratory feedback mechanisms?

Answer 18

Stretch receptors

Chemoreceptors

Question 19

What is the Hering Breuer reflex?

Answer 19

Stretch receptors in the lung send signals back to the medulla to limit inspiration
Prevents over inflation of the lungs

Question 20

Hering Breuer reflex method

Answer 20

1. Signal from the inspiratory centre goes to the phrenic nerve
2. Diaphragm contracts
3. Stretch receptors in the lung send signal via the vagus nerve
4. This inhibitory signal stops the inspiratory centre signalling further stopping the inspiration phase

Question 21

Where are central chemoreceptors found?

Answer 21

Cerbo-spinal fluid

Question 22

What do central chemoreceptors do?

Answer 22

Sense carbon dioxide and pH
Indirect response to increased carbon dioxide
- Leads to an increase in ventilation

Question 23

Where are peripheral chemoreceptors found?

Answer 23

Carotid body and aortic arch

Question 24

WHat do peripheral chemoreceptors do?

Answer 24

Sense carbon dioxide, oxygen and pH
Respond to increased carbon dioxide, decreased pH and decreased oxygen
- Stimulation leads to an increase in ventilation