Flashcards in Respiratory Physiology Deck (126)
What is meant by cortical and hypothalamic higher brain center influences on respiration?
Cortical - voluntary hyperventilation or breath holding
Hypothalamic - Emotions - anger/anxiety (hyperventilation) and sensory reflexes such as gasping in response to pain or cold
What happens to the firing of neurones in the medullar obongata in response to stretch receptors in the lungs as inspiration progresses?
As stretch receptors get more stretched
Get an increase firing of expiratory neurones in the ventral respiratory group
Decreased firing of inspiratory neurones in the dorsal respiratory group
What role do muscle spindles have in controlling respiration, where do they tend to be located?
Rich in intercostals, few in diaphragm
Activated in intercostals, associated with contraction in inspiration
How can baroceptors affect respiration?
They sense blood pressure but can also influence respiration
When they sense higher blood pressure you get decreased ventilation
What are J receptors and how can they affect respiration?
Next to capillaries around alveolar walls
Activated by traumas such as pulmonary oedema, inflammatory agents and thus increase ventilation
Where are peripheral chemoreceptors which control respiration located and what are the sensitive to?
Located in the carotid and aortic bodies
Sensitive to hypoxia, hypercapnia and acidosis
What kind of cells in peripheral chemoreceptors are sensitive to hypoxia?
What is the prominent driver for respiration?
Changes in H+ and CO2 levels
Where are central chemoreceptors located?
Close to the medulla respiratory centers
What are central chemoreceptors sensitive to?
CO2 and H+ in cerebrospinal fluid
H+ cannot pass the blood brain barrier, how are central chemoreceptors informed of H+ levels?
CO2 can pass the BBB
In cerebrospinal fluid CO2 dissolves to form H+ which informs of H+ levels
What is the most important driver of respiration in chronic respiratory conditions?
Hypoxic drive - get used to a high level of CO2
What is the oxygen cascade?
The drop on PO2 as you pass from dry air to mitochondria
What is PO2 in arteries?
What did the Krogh model show?
Tissue is like a cylinder with a capillary moving through it
PO2 gradient decreases as you move along the cylinder and out towards the edges of the cylinder - you end up with a lethal corner - furthest point along the cylinder at the edge
What is the definition of oxygen delivery?
Amount of O2 leaving the heart in one minute (DO2)
Calculated as the product of cardiac output and the amount of O2 carried in the blood
What is the definition of O2 consumption?
Amount of O2 used by the body in 1 minute
What 3 factors affect VO2?
1) Age - peak at 0-2 years then rate falls for the rest of your life
2) Temperature - metabolic rate doubles with every 10 degree increase in temp
What are the 4 physiological responses to anaemia?
1) Increased 2,3 DPG - shifts the curve to the right
2) Reduced blood flow to non essential organs
3) Increased O2 extraction from the blood
4) Increased cardiac output
What is the physiological response to high altitude?
O2 saturation decreases with altitude and the amount of Hb increases
What is the respiratory exchange ratio?
The ratio of CO2 production (VCO2) to O2 consumption (VO2)
What is a persons respiratory quotient?
RER at rest - normal value = 1
What 3 things affect the respiratory quotient?
1) Acid Base balance
3) Metabolic fuel
In cardio pulmonary exercise testing at what point is the anaerobic threshold reached in terms of VO2 and VCO2?
The point when VO2 is still increasing but VCO2 has stopped increasing at the same rate
What are the 3 circles in Barcroft classification of cellular hypoxia?
1) Anoxic - lack of O2 in blood
2) Stagnant - lack of blood supply
3) Anaemic - lack of Hb
Why is cardiopulmonary testing sometimes carried out on patients before they have surgery?
To make sure the have sufficient VO2 as demand during and after surgery for O2 is high so have to make sure you have sufficient VO2 max
What happens to FiO2 and PiO2 at altitude?
FiO2 stays the same but overall air pressure decreases and therefore PiO2 decreases
What is the physiological response to high altitude? 4
1) Hyperventilation and respiratory alkalosis - get rid of CO2 to make room for O2
2) Increased 2,3DPG - shift curve to the right
3) Polycythaemia - slow to develop
4) Bicarbonate excretion from kidneys
What are the symptoms of mountain sickness? 6
3) Loss of apetite
4) Difficulty sleeping/exercising