Lecture 27 - Basic Mechanisms Of The Respiratory Rhythm Generator Flashcards
What is a respiratory rhythm generator (RRG)
A network of interneurones that produce a predictable and repetitive motor pattern
What are the properties of a RRG
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
What area of the brain is responsible for emotions
The lambic system
What are examples of sensory afferents
Pulmonary stretch receptors and peripheral chemoreceptors
What are the three phases of the breathing cycle
Inspiration, post inspiration and late-expiration
How many types of neuronal discharge are involved in the breathing cycle
Six
What are the different neuronal discharges
Pre-I, early-I, I, late-I, early-E and E
What happens in Pre-I
The pre-I neurones inhibit exploratory neural circuits and the exploratory muscles relax
What happens in early-I
The early-I neurones inhibit output from the entire RRG
What is early-I also known as and why
The refractory period as there is no breathing movements
What happens during I
The I neurones increase firing
What does the firing of I neurones cause
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
As the intensity of I firing increases what happens to the muscles of respiration
The inspiratory muscles contract and the exploratory muscles relax
What happens during late-I
The late-I neurones feedback to suppress I neuronal firing when they are at peak intensity
What may be involved in late-I
The stretch receptor input from the vagus
What occurs with the inspiratory muscle and lungs during late-I
The inspiratory muscles start to relax and the lungs begin to deflate
What happens during early-E
The early-E neurones repress all I and E neuronal firing
What is caused during early-E
A refractory period at peak inhalation
What happens during E
The E neurones increase their firing rate
What effect does an increase in firing of E neurones have
They activate the motor neurone circuit to the expiratory muscles
During exercise, where is a point of major conscious effort in the neural discharge
E
What is happening to the respiratory muscles during E
Inspiratory - relax
Expiratory - contract
Breathing patterns are changed by signals sent from
Central chemoreceptors and peripheral chemoreceptors
Where are central chemoreceptors found
On the medulla surface
Where are peripheral chemoreceptors found
In the carotid body, aortic body and neuroepithelial bodies
What do central and peripheral chemoreceptors do and what does it effect
They relay information to the medulla respiratory centre which affects the dorsal respiratory group so the input modulates the rhythm generated by the RRG
What is the breathing pattern changed by
The ventral respiratory group particularly the pre-Botzinger complex
In normal breathing what does the burst firing of the phrenic nerve cause
The diaphragm to contract and inhalation to occur
What needs to happen for an increase in tidal volume
Increased action potentials per burst gives a stronger diaphragmatic contraction and deeper breathing
For an increase in total ventilation volume what must occur
There must be an increase in action potentials per burst per minute which gives an increased breathing frequency
