Lec 18-19

Question 1

What are the 3 respiratory centre areas? (Neural Control)

Answer 1

1. Rhythmicity Area
2. Apneustic Area
3. Pneumotaxic Area

Question 2

Where is the Rhythmicity Area located?

Answer 2

The medulla oblongata of the brain stem

Question 3

What do the inspiratory cells of the rhymicity area stimulate? (what nerves)

Answer 3

Phrenic and intercostal nerves

Question 4

What do the expiratory cells of the Rhymicity Area stimulate? (what nerves)

Answer 4

Intercostal and lower spinal nerves

Question 5

Where is the Apneustic Area located?

Answer 5

In the lower and mid pons of brain stem

Question 6

What is the Apneustic Area responsible for?

Answer 6

The stimulation of the inspiratory cells of the rhythmicity area and thereby promotes inspiration

Question 7

Where is the Pneumotaxic Area located?

Answer 7

In the upper region of the pons of brain stem

Question 8

What effects does the Pneumotaxic Area have?

Answer 8

• An inhibitory effect on the apneustic area -> indirectly inhibits inspiration
• During exercise: it stimulates the expiratory cells of the rhythmicity area and promotes expiration

Question 9

What are the 2 types of proprioceptors?

Answer 9

1. Joint Proprioceptors

2. Stretch receptors in lungs

Question 10

How are joint proprioceptors stimulated?

Answer 10

By the movement of the limbs

Question 11

What effects do joint proprioceptors have?

Answer 11

Cause excitation of the respiratory centre of the brain

=> increase in the rate and depth of breathing

Question 12

How are stretch receptors stimulated?

Answer 12

• Mechanoreceptors

- Sensitive to stretch/ tension located in the walls of bronchi and bronchioles

Question 13

What effects do stretch receptors have?

Answer 13

Transmit impulses to the apneustic centre via the vagus nerve
=> inhibition of inspiration known as the Hering Breur Inflation Reflex

Question 14

Voluntary controls of ventilation?

Answer 14

1. Occurs in the cerebral cortex
2. Limited control - over-ridden by chemicals
3. Can increase or decrease both rate and tidal volume
4. Useful for talking, singing, laughing, exercise

Question 15

What are the 2 types of chemoreceptors in the body to sense arterial levels of oxygen, carbon dioxide and pH?

Answer 15

Central and peripheral chemoreceptors

Question 16

Where are central chemoreceptors located?

Answer 16

In the medulla oblongata of the brain stem

Question 17

How are the central chemoreceptors activated?

Answer 17

By the changes in the chemical composition of the cerebrospinal fluid

Question 18

What happens when there is a rise in acidity sensed by the central chemoreceptors?

Answer 18

1. Directly stimulate receptors to send signals to the rhythmicity centre in the medulla oblongata
2. It stimulates the phrenic nerve (diaphragm) and external intercoastal nerves (intercostal muscles)
3. Result: Ventilation increases by up to 100%
   => reduces CO2 levels and this mechanism is switched off

Question 19

Where are the peripheral chemoreceptors located?

Answer 19

• Various places in the body
• Aortic bodies in the aortic arch
• Carotid bodies at the junction of the internal and external carotid arteries deep in the neck

Question 20

How do the peripheral chemoreceptors act?

Answer 20

They are indirect
- aortic bodies act via the vagus nerve
- carotid bodies act via the glosspharyngeal nerve
=> signal the respiratory centre (medulla oblongata), thus stimulates phrenic and external intercoastal nerves)
- Result: increase resp rate and tidal volume by up to 50% -> more O2 exchanged
=> mechanism switched off

Question 21

How are the peripheral chemoreceptors activated?

Answer 21

Changes in concentrations of CO2 (**), O2, and H+ in arterial blood