L4 - Control of Respiration Flashcards
How is breathing regulated?
Automatic, rhythmical process
Basic rhythm is generated by centres in the medulla
Inputs from various regions act to modify the respiratory patterns
How can breathing be altered consciously?
Hyperventilation and breath holding
However, these are temporary and can be overridden
How is the inspiration period generated?
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
What 3 types of pattern output can the Pre-Botzinger complex generate?
Eupneic – standard normal breathing
Sigh – increased intensity and magnitude
Gasp – short, decreased magnitude and intensity (when a lack of oxygen)
What are the cell types of the Pre-Botzinger complex?
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
What is NALCN and where is it found?
Sodium leak channel found in the Pre-Botzinger complex
It contributes to the depolarisation phase
What is the role of potassium in the Pre-Botzinger complex?
Background potassium conductance determines starting membrane potential
3mmol/l to 8mmol/l potassium outside the cell will lead to cell depolarisation
What are the two different types of pacemaker cells?
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
The transition to bursting activity depends on?
Two types of inward current
- Persistent sodium current (INaP)
- CAN cation current (ICAN+)
What are the effects of hypoxia on the Pre-Botzinger complex?
- Normal eupneic breaths (autonomous spiking neurones and CS pacemakers)
- Deeper breaths, sighs, to bring more oxygen in (CS pacemakers)
- Period of inactivity followed by gasping phases
What are the two medullary centres?
Dorsal and ventral respiratory group
What does the dorsal respiratory group control?
Controls inspiration by sending signals to the inspiratory muscle
Spontaneously active – period of activity – shuts off – period of activity
What does the ventral respiratory group control
Controls inspiration and expiration
Inactive during quiet respiration
Helps control forceful inspiration and expiration
What does the pons control?
The pons send stimuli to the medulla to regulate rate and depth of breathing
What are the 2 centres of the pons?
Penumotaxic and apneustic centre
What does the pneumotaxic centre control?
Increases the rate by shortening inspiration
Inhibits inspiratory centre
What does the apenustic centre control?
Increases the depth and reduces the rate by prolonging inspirations
Stimulates inspiratory centre
What are the two main respiratory feedback mechanisms?
Stretch receptors
Chemoreceptors
What is the Hering Breuer reflex?
Stretch receptors in the lung send signals back to the medulla to limit inspiration
Prevents over inflation of the lungs
Hering Breuer reflex method
- Signal from the inspiratory centre goes to the phrenic nerve
- Diaphragm contracts
- Stretch receptors in the lung send signal via the vagus nerve
- This inhibitory signal stops the inspiratory centre signalling further stopping the inspiration phase
Where are central chemoreceptors found?
Cerbo-spinal fluid
What do central chemoreceptors do?
Sense carbon dioxide and pH
Indirect response to increased carbon dioxide
- Leads to an increase in ventilation
Where are peripheral chemoreceptors found?
Carotid body and aortic arch
WHat do peripheral chemoreceptors do?
Sense carbon dioxide, oxygen and pH
Respond to increased carbon dioxide, decreased pH and decreased oxygen
- Stimulation leads to an increase in ventilation
