Control of Lung Function Flashcards
What part of the brain + spinal chord innervates the lungs?
medulla oblongata ( + pons region )
What are the 4 parts of the brain + spinal chord that innervate the lungs?
- Dorsal respiratory group
- Ventral respiratory group
- Apneustic centre
- Pneumotaxic centre
What does the dorsal respiratory group do?
- Inspiratory centre
- Main ‘controller’ of inspiration
- Set the ‘rate’
What does the ventral respiratory group do?
- Expiratory centre
- Inactive during quiet breathing
- Inhibits apneustic centre
What does the apneustic centre do?
- Stimulates activity in DRG
* Inhibited by pulmonary afferents
What does the pneumotaxic centre do?
- The ‘inspiratory off switch’
* Regulates depth & frequency
How does the dorsal respiratory group affect other centres + groups?
• inactivates the ventral respiratory group
How does the ventral respiratory group affect other centres + groups?
- inactivates the dorsal respiratory group
* inactivates the apneustic centre
How does the apneustic centre affect other centres + groups?
• stimulates activity in dorsal respiratory centre
How does the pneumotaxic centre affect other centres + groups?
• inhibits activity in the dorsal respiratory group
How does the pneumotaxic centre regulate the apneustic one?
when a threshold frequency is hit, the pneumotaxic centre inhibits the apneustic one + causes a period of latency before the the apneustic centre can start again - called quiet breathing
What motor nerves innervate the skeletal muscles of the lungs?
- phrenic nerve from C3 to C5 innervates diaphragm
* intercostal nerves from T1 to T11 innervate intercostal muscles
What are the internal intercostal muscles + accessory respiratory muscles responsible for?
expiration
What are the external intercostal muscles + diaphragm responsible for?
inspiration
What ganglion + nerves are involved in parasympathetic innervation of the lungs?
jugular ganglion + nodose ganglion + vagus nerve (all coming from brainstem medulla)
What ganglion + nerves are involved in sympathetic innervation of the lungs?
superior cervical ganglion + lots of innervation from C1 to T12
What are the junctions between cells like in normal capillaries?
H2O filled gap junctions
What are the junctions between cells like in the BBB (blood brain barrier) capillaries?
continuous capillaries with tight junctions
Why are the tight junctions of the BBB capillaries important?
only lets small molecules (e.g. CO2 pass through) + restricts large + charged molecules (e.g. H+ ions, etc.)
How are levels of O2 detected in the medulla?
- central chemoreceptors on surface of the medulla - looks for changes pH as a result of increased CO2 in CSF
- peripheral chemoreceptors in the arterial blood for O2 + CO2
When do CO2 levels in the blood rise?
during increased metabolic use of O2, e.g. exercise
How is CO2 converted + transported in the bloodstream?
- CO2 → H2CO3 (carbonic acid, enzyme: CARBONIC ANHYDRASE
* H2CO3 → HCO3- (bicarbonate ions) + H+, no enxyme for acid disassociation
How does a build-up of CO2 change pH?
increased CO2 = increased H+ ions = decreased pH
How do respiratory centres react when blood pH falls?
pH sensors in brain stem respond immediately + cause RCs to INCREASE rate + depth of breathing
What are the 3 pulmonary afferents that affect ventilation?
- irritant receptors
- stretch receptors
- J receptors
What are irritant receptors?
- embedded within + beneath airway epithelium
- leads to coughing - forceful expiration against closed glottis w/ sudden glottal opneing + high velocity expulsion of air
What are stretch receptors?
• activated by excessive inflation of lungs
• afferent signals to respiratory centres
inhibit DRG + apneustic centre +
stimulate pneumotaxic + VRG
• inspiration inhibited + expiration
stimulated
What are J receptors?
- sensitive to oedema + pulmonary capillary engorgement
* increases breathing frequency
What is volitional apnoea
cessation of breathing
What is an acid?
molecule with a loosely bound H+ ion
Why does blood acidity need to be regulated?
changes in pH will result in marked changes in 3D structure of proteins
What is a base?
anionic molecule capable of reversibly binding to protons
What is the relationship between acids + bases?
in equilibrium
How was the buffering capacity of blood identified?
Pitts + Swan injected acid into dog expecting pH change BUT there was very little change in pH
What is the buffering capacity of blood?
ability to react to pH imbalances almost immediately + return it to normal
How is proton concentration converted to pH?
pH = -log10[H+]
How is pH converted to proton concentration?
[H+] = -10 to the power of pH
What is alkalaemia?
higher-than-normal pH of blood
What is acidaemia?
lower-than-normal pH of blood
What is alkalosis?
circumstances that will decrease [H+] and increase pH
What is acidosis?
circumstances that will increase [H+] and decrease pH
What is needed to correct alkalosis?
acidosis
What is needed to correct acidosis?
alkalosis
What is the difference between the compensatory responses of the lungs vs. the kidneys?
changes in ventilation = RAPID response
changes in HCO3- + H+ retention + secretion in kidneys = SLOW response
What are peripheral chemoreceptors?
- positioned near carotid baroreceptors
* responds to changes in blood molecule concentrations + helps maintain cardiorespiratory homeostasis
How can emotional change affect ventilation?
higher brain centres (limbic system) + special senses → emotional response → respiratory control centre
How can exercise affect ventilation?
- efferents from primary motor cortex to skeletal musculature partly innervate the medulla otw
- proprioceptive afferents from muscle spindles & golgi tendon organs innervate medulla otw to brain
What is the effect of skin afferents on breathing?
immersion in cold water (< 10 degrees) = changes in ventilation (e.g. inspiratory gasps + hyperventilation)
