Physiology 6 - Control of Respiration Flashcards
how is ventilation controlled?
by respiratory centres in the brain stem
where is the major rhythm generator?
the MEDULLA
what section of the medulla allows normal ventilation to be retained?
section ABOVE the medulla
what section of the medulla ceases ventilation?
section BELOW the medulla
What name is given to the network of neurones that generate the breathing rhythm?
Pre-Botzinge complex
where is the pre-botzinge complex located?
located near the upper end fo the medullary respiratory centre
what does the pre-botzinge complex excite?
they excite dorsal respiratory group neurones
what does the excitement of dorsal respiratory group neurones result in?
fire in bursts
what does firing lead to?
contraction of inspiratory muscles which leads to inspiration.
when firing stops - passive expiration
what second group is excited when there is increased firing dorsal neutrons?
ventral respiratory group neurones
what do ventral respiratory group neurones excite?
excites internal intercostal abdominals
what does excitement of internal intercostal muscles lead to?
leads to forceful expiration
the rhythm generated in the medulla can be modified by neurones in the pons called?
the PNEUMOTAXIC CENTRE (PC)
what does stimulation of pneumotaxic centre terminate?
terminates inspiration
what happens to breathing WITHOUT PC?
breathing is prolonged, inspiratory gasps with brief expiration
= APNEUSIS
what does the apneustic centre do?
- impulses from these neurones excite inspiratory area of the medulla, prolonging inspiration
give 5 examples of how the respiratory centre is influenced by stimuli?
1) higher brain centres
2) stretch receptors in walls of bronchi & bronchioles
3) juxapulmonary receptors
4) joint receptors
5) barareceptors
what are the 3 main factors that control respiration?
1) pH
2) PaCO2
3) PaO2
how are these 3 chemical factors monitored?
they are monitored by chemo-receptors that prove input to respiratory centres
what do the respiratory centres do?
they send nerve impulse to effectors in respiratory muscles that control their frequency & force of contraction, thus change the rate & depth of breathing
what are the 2 different types of chemoreceptors?
1) central chemoreceptors
2) peripheral chemoreceptors
5 factors that may increase ventilation during exercise?
1) adrenaline release
2) impulses from cerebral cortex
3) increase in body temperature
4) accumulation of CO2 + H+ generated by active muscles
5) reflexes originating from body movement
why is the cough reflex present?
vital part of body defence mechanisms
what does the cough reflex do?
helps clear airways of dust, dirt or excessive secretions
when is the cough reflex activated?
by irritation of airways or high airways (e.g. asthma)
where is the activation centre for the cough reflex?
the medulla
when do central and peripheral chemoreceptors modify breathing rhythm?
when theres changes in;
1) PaO2
2) PaCO2
3) pH
what do peripheral chemoreceptors sense?
they sense TENSIONS OF O2 & CO2 & [H+] in the blood
how do the peripheral chemoreceptors respond?
they response by sending more impulses to respiratory centres to increase the rate & depth of breathing & improve excretion of CO2
where are central chemoreceptors situated?
they are situated near the surface of the medulla of the brainstem
what do central chemoreceptors respond to?
they respond to [H+] of the cerebrospinal fluid (CSF)
how is the CSF separated from the blood brain barrier?
it is separated from the bbb by blood.
what is hypercapnia?
elevated levels of CO2 in blood.
what is hypoxia?
deficiency of amount of O2 reaching the tissues
is the hypoxic drive effect done via peripheral of central chemoreceptors?
all done via the peripheral chemoreceptors
when is the hypoxic drive stimulated?
when PO2 levels fall below 8.0kPa
how is hypoxia at high altitudes caused?
caused by a decreased partial pressure of inspired oxygen (PiO2)
what is the acute response to hypoxia at high altitudes?
hyperventilation & increased cardiac output
what are some symptoms of acute mountain sickness
- headache
- fatigue
- nausea
- dizziness
- sleep disturbances
- exhaustion
- shortness of breath
- unconsciousness
- tachycardia
what re 5 chronic adaptations to high altitude hypoxia
1) increased RBC production (polycythaemia)
- O2 carrying capacity of blood increases
2) increased 2,3-biphosphoglycerate with RBC
- O2 offloaded to tissues more easily
3) increased number of capillaries
- blood diffuses more easily
4) increased number of mitochondria
- O2 can be used more efficiently
5) kidneys conserve acid
- arterial pH decreases
