Respiratory: Control of Respiration Flashcards
Where is the major rhythm generatory for resp
Medulla
What network of neurones generate the breathing rhythm?
Pre-botzinger complex
Where is this complex located
the upper end of the medulla
What gives rise to inspiration
Dorsal respiratory group of neurones fire.
Leads to contraction of inspiratory muscle= INSPIRATION
When firing stops= passive expiration
What gives rise to active expiration
Increased firing of dorsal neurones excites a second group of ventral neurones which excite internal intercostal muscles and illicit forceful expiration
How can the rhythm be modified?
By neurones in the pons
Explain the mechanism of modifying rhythm in the pons pneumotaxic centre
The pneumotaxic centre is stimulated when dorsal respiratory neurones fire.
Stimulation terminates inspiration.
What would happen without the pneumotaxic centre
breathing would be prolonged inspiratory gasps with brief expiration known as APEUNSIS
Explain the rhtym modifyin by the apneustic centre
impulses from theses neurones excite inspiratory area of medulla and prolong inspiration
Name examples of involuntary modifications of breathing
Pulmonary stretch receptors refelx
Joint receptors reflex
Stimulation of resp centre by temp, adrenalin or impulses from cerebral cortex
cough reflex
Explain pulmonary stretch receptors
Activated during inspiration- inhibits inspiration
Only fire at large tidal volumes
Describe the joint receptor reflex
Impulses from moving limbs reflexly increased breathing
What factors may increase ventilation during exercise
Body movement Adrenaline Impulses from cerebral cortex Increased body temp Accumulation fo COs and H plus ions
Explain the cough reflex
Activated by irritation of the airways or tight airways eg asthma
Afferent discharge stimulates short intake of breath followed by closure of the larynx, the contraction of abdominal muscles and opening of the larynx and there is an expulsion of air at high speed
Where is the cough reflex controlled
the medulla
What senses the values of gas tensions
chemoreceptros
what do your peripheral chemoreceptors sense
tension of oxygen and carbon dioxide, and the pH of the blood
Where are central chemoreceptors located
surface of medulla
What do central chemoreceptors respond to
hydrogen ions of cerebrospinal fluid
Why is CSF less buffered than blood?
Less protein
What happens to ventilation as you become hypercapnic
Ventilate more
What happens in mild to moderate hypoxia
Increased ventilation (peripheral chemoreceptors0
What happens in sever hypoxia
Neurons are depressed- decreased ventilation
What mediates the hypoxic drive
peripheral chemoreceptors
Explain hypoxic drive
Stimulates when PO2 falls below 8- it is important in patients with COPD and at high altitudes
What causes hypoxia at high altitudes
decrease partial pressur of oxygen
How does you body respond to this
hyperventilation and increase cardiac output
Give the chronic adaptations to high altitude
Increaced RBC production Increased 2,3 BPG Increase capillaries Increased mitochondria Kidneys conserve acid - decrease in arterial pH
What is the hydrogen ion drive or respiration
Via peripheral chemoreceptors- stimulated in response to H plus causes hyperventilation to try to eliminate more carbon dioxide from the body
