Lecture 27 - Basic Mechanisms Of The Respiratory Rhythm Generator

Question 1

What is a respiratory rhythm generator (RRG)

Answer 1

A network of interneurones that produce a predictable and repetitive motor pattern

Question 2

What are the properties of a RRG

Answer 2

They are always active even in the absence of conscious input, they transmit an orderly sequence to respiratory muscles and they respond to inputs from other parts of the brain as well as sensory afferents

Question 3

What area of the brain is responsible for emotions

Answer 3

The lambic system

Question 4

What are examples of sensory afferents

Answer 4

Pulmonary stretch receptors and peripheral chemoreceptors

Question 5

What are the three phases of the breathing cycle

Answer 5

Inspiration, post inspiration and late-expiration

Question 6

How many types of neuronal discharge are involved in the breathing cycle

Answer 6

Six

Question 7

What are the different neuronal discharges

Answer 7

Pre-I, early-I, I, late-I, early-E and E

Question 8

What happens in Pre-I

Answer 8

The pre-I neurones inhibit exploratory neural circuits and the exploratory muscles relax

Question 9

What happens in early-I

Answer 9

The early-I neurones inhibit output from the entire RRG

Question 10

What is early-I also known as and why

Answer 10

The refractory period as there is no breathing movements

Question 11

What happens during I

Answer 11

The I neurones increase firing

Question 12

What does the firing of I neurones cause

Answer 12

As the frequency of firing of I neurones increases more I neurones contribute, they activate the motor neurone circuit and inhibit E and pre-I neuronal circuits

Question 13

As the intensity of I firing increases what happens to the muscles of respiration

Answer 13

The inspiratory muscles contract and the exploratory muscles relax

Question 14

What happens during late-I

Answer 14

The late-I neurones feedback to suppress I neuronal firing when they are at peak intensity

Question 15

What may be involved in late-I

Answer 15

The stretch receptor input from the vagus

Question 16

What occurs with the inspiratory muscle and lungs during late-I

Answer 16

The inspiratory muscles start to relax and the lungs begin to deflate

Question 17

What happens during early-E

Answer 17

The early-E neurones repress all I and E neuronal firing

Question 18

What is caused during early-E

Answer 18

A refractory period at peak inhalation

Question 19

What happens during E

Answer 19

The E neurones increase their firing rate

Question 20

What effect does an increase in firing of E neurones have

Answer 20

They activate the motor neurone circuit to the expiratory muscles

Question 21

During exercise, where is a point of major conscious effort in the neural discharge

Answer 21

E

Question 22

What is happening to the respiratory muscles during E

Answer 22

Inspiratory - relax

Expiratory - contract

Question 23

Breathing patterns are changed by signals sent from

Answer 23

Central chemoreceptors and peripheral chemoreceptors

Question 24

Where are central chemoreceptors found

Answer 24

On the medulla surface

Question 25

Where are peripheral chemoreceptors found

Answer 25

In the carotid body, aortic body and neuroepithelial bodies

Question 26

What do central and peripheral chemoreceptors do and what does it effect

Answer 26

They relay information to the medulla respiratory centre which affects the dorsal respiratory group so the input modulates the rhythm generated by the RRG

Question 27

What is the breathing pattern changed by

Answer 27

The ventral respiratory group particularly the pre-Botzinger complex

Question 28

In normal breathing what does the burst firing of the phrenic nerve cause

Answer 28

The diaphragm to contract and inhalation to occur

Question 29

What needs to happen for an increase in tidal volume

Answer 29

Increased action potentials per burst gives a stronger diaphragmatic contraction and deeper breathing

Question 30

For an increase in total ventilation volume what must occur

Answer 30

There must be an increase in action potentials per burst per minute which gives an increased breathing frequency