Physiology - Control of Respiration Flashcards
Arrangement of brainstem (superior to inferior).
Pons
Medulla oblongata
Spinal cord.
Ventilation above and below medulla?
Above - Normal.
Below - Ceases.
What is the medulla?
Major rhythm generator.
What generates the breathing rhythm?
A network of neurons called pre-botzinger complex.
Where is the pre-botzinger complex located?
Upper end of medullary respiratory centre.
In what two ways can respiration be controlled?
Neural
Chemical.
How does inspiration arise?
Rhythm generated by pre-botzinger complex which excites dorsal respiratory group neurones that fire in bursts. The firing leads to contraction of inspiratory muscles causing inspiration.
What happens when firing of dorsal respiratory neurons stops?
Passive expiration.
What about active expiration during hyperventilation?
Increased firing from dorsal neurones activate a second group - Ventral neurons. Which excite internal intercostals and abdominals causing forceful expiration.
What can rhythm be modified by?
Neurones in the pons.
What is the PC in the pons?
Pneumotaxic centre. Stimulation terminates inspiration.
When is PC stimulated?
When dorsal neurones fire.
What would happen without PC?
Prolonged breathing, gasps with brief expiration. - Apneusis.
What are the two centres in the pons?
Pneumotaxic and Apneustic.
What does the apneustic centre do?
Impulses from apneustic neurones excites inspiratory area of medulla and prolong inspiration.
What are the respiratory centres influenced by?
Stimuli from: Higher brain centres, Joint Receptors, Baroreceptors, Stretch receptors In bronchioles, Juxtapulmonary receptors.
What is the inflation Hering-Breur reflex?
When do they act?
Pulmonary stretch receptors in the bronchioles that prevent hyperinflation by Inhibiting inspiration.
Only at large tidal volumes.
Involuntary modifications of breathing.
Hering-Breuer Reflex
Joint receptors in exercise,
Cough reflex,
Stimulations of resp centre by temp, adrenaline or
impulses from the cerebral cortex
What occurs after a period of exercise that will increase ventilation?
Accumulation of CO2 and CO2 generated by active muscles.
Describe the process of the cough reflex?
Afferent discharge stimulates a short intake of breath followed by closure of the larynx, then contraction of abdominals which increases intra-alveolar pressure and finally opening of larynx and expulsion of air at high speed.
What does the cough reflex protect against?
When is it activated?
Vital part of body’s defense system as it helps clear airways of dust, dirt or excessive secretions.
Activated by irritation/ tight airways (asthma)
What type of control system is chemical control of respiration?
Negative Feedback.
What are the chemically controlled variables of respiration?
What senses the values of these variables?
Blood gas tensions (especially CO2).
Chemoreceptors.
What are the 2 types of chemoreceptors?
Peripheral and central.
