Peripheral Receptors Flashcards
What is a chemoreceptor
Receptor that responds to change in chemical composition of blood or fluid surrounding it
What are the 2 most important inputs to medullary inspiratory neurons?
Peripheral and central chemoreceptors
Where are peripheral chemoreceptors?
Carotid and aortic bodies, paraganglia
What do carotid bodies monitir?
Oxygen supply to brain
What are the 2 types of cells in carotid bodies?
Type 1 glomus cells - high dopamine content, close to endings of afferent carotid sinus nerve
Type 2 glomus cells - 20%
What does the carotid body mainly respond to?
Arterial PO2
What are type 1 glomus cells sensitive to?
Decrease in arterial PO2
Increase in H+ and PCO2 and K+
What cell type is initial site of sensory transduction?
Type 1
What do type 1 cells release in response to hypoxia?
Transmitters -> depolarises afferent nerve endings -> increase in sesnory discharge
What are 5 main candidate neuromodulators for hypoxic chemotransduction?
Dopamine
ACh
ATP
ROS
Cytokines
What is hypoxic hypoxia?
Insufficient O2 to lungs eg COPD
What is stagnant hypoxia?
Failure to transport sufficient O2 due to inadequate blood flow
What is anaemic hypoxic?
Reduced oxygen carrying capacity of blood due to reduced Hb
What is histotoxic hypoxia?
Impaired oxygen use by tissues
What can low PO2 be due to?
Altitude
Hypoventilation
What can lead to hypoventilation?
central
spinal injury
neuromuscular disorders
lung disease
obesity
airway obstruction
What are 4 physiological responses to hypoxia?
Hyper ventilation
Increased CO
Systemic vasodilation
Increase in transcription factors eg HIF 1 -> increases EPO
For PACs when does sensitivity to oxygen changes begin at?
500mmHg but response starts when it drops below 100mmHg
What are used as indicators for arterial gas mixture levels?
End tidal PO2 and PCO2 levels
In hypoxia what happens to PO2 if PCO2 is kept within a normal range?
PO2 reduced close to 50mmHg before increased ventilation begins
What does increasing PCO2 cause?
Increases ventilation for a given PO2
When is the ventilatory response more robust?
With hypercapnia and hypoxic