Control of Ventilation Flashcards
Why is oxygen required?
To generate ATP through oxidative phosphorylation
If you eat lots of fats, how does this affect O2 intake?
Need to take in more O2
If you eat lots of carbohydrates, how does this affect O2 intake?
Need to take in less O2
What is the equation of minute ventilation?
Minute ventilation = breathing frequency x tidal volume 5L = 10 breaths per min x 500ml per breath (normal)
How much of breath is lost in dead space?
150ml of lung volume is dead space. Not all breath gets to lungs as last 150ml is lost (350ml gets to lungs)
How much can O2 consumption increase by during exercise?
10x
What can happen as a result of not getting rid of CO2 quick enough?
Acidosis
How can altitude affect breathing?
Less O2 in the air so need to work harder to maintain O2 supply
How is altitude sickness caused?
Hypoxic (due to lack of O2 in air) which generates reflex to respire more and breathe out more CO2. This causes CO2 levels to drop, causing you to stop breathing. (Alkalosis followed by acidosis)
How is altitude sickness treated?
Inhibit loss of bicarbonate ions in renal function which causes acidosis (so when you breathe harder to make up for hypoxia, you don’t generate alkalosis as a result)
How can sleep apnoea affect breathing?
Periodic cessation during sleep. Hypoxic effect in blood stimulates ventilation again and wakes patient up.
What are the 2 types of chemoreceptors?
Peripheral and central
Where are peripheral chemoreceptors?
Located in carotid body and aortic arch.
What are peripheral chemoreceptors sensitive to? What do they do?
Sensitive to hypoxia (low O2), hypercapnia (high CO2) and acidosis (high H+)
Detect large changes in pO2 as the arterial blood leaves the heart. Relatively insensitive but effects are almost instant.
What happens if peripheral chemoreceptors detect abnormally low pO2?
Afferent impulses travel to the respiratory centres in the brainstem and a number of response are coordinated which aim to increase pO2 again. 1. Increase respiratory rate and tidal volume –> allows more O2 to enter the lungs 2. Directing blood flow towards kidneys and brain (organs most sensitive to hypoxia) 3. Increasing cardiac output to maintain blood flow and O2 supply to body’s tissues
Where are central chemoreceptors?
Located in the medulla oblongata of the brainstem. Close to the medulla respiratory centres but also close to a rich blood supply
What do the central chemoreceptors do?
Sensitive to CO2 and H+
Receptors are more sensitive and detect smaller changes in arterial pO2. Constantly initiate negative feedback loops which act to control our respiratory system.
What happens if central chemoreceptors detect an increase in pCO2?
Leads to increase in ventilation, resulting in more CO2 being blown out so pCO2 returns to normal
What happens if central chemoreceptors detect a decrease in pO2?
Leads to a decrease in ventilation, resulting in more CO2 being retained in our lungs so pCO2 returns to normal.
Where is the respiratory centre? What does it control?
In the brain. Controls automatic breathing.
What receptors are in the lungs?
- Pulmonary stretch receptors (give reflex to stop lungs over expanding) 2. J receptors (C afferent fibres and sensitive to diseases that cause hypoxia) 3. Cough or lung irritant receptors
What are examples of input receptors?
Chemoreceptors, lung receptors, nasal and upper airway receptors, muscle stretch receptors, joint proprioceptors, arterial baroreceptors
What can override respiratory centre control?
Cortical control of voluntary breathing
What are the effector muscles of respiration?
- Diaphragm 2. Intercostal muscles 3. Abdominal muscles 4. Accessory muscles
What is medulla?
Core centre of respiratory control –> inspiratory and expiratory areas
What is the pons?
The largest part of the brainstem, located above the medulla and below the midbrain.
Has inputs which can influence respiratory centre (regulates medulla) Apneustic and pneumotaxic areas
What group must still function in the medulla for you to keep breathing?
Dorsal respiratory group in medulla. Responsible for inspiration.
What is ventral respiratory group (VRG) responsible for?
Mainly responsible for expiration