Lecture 5 Flashcards
Where are the 2 classes of chemoreceptors found and what stimuli activates them?
Central and Peripheral.
Central is in medulla, responds directly to H+ (directly reflecting PCO2), primary ventilatory drive.
Peripheral is in carotid and aortic bodies, responding primarily to PO2 (less than PCO2) and plasma[H+]. Secondary ventilatory drive.
What factors are involved in changing “resp. drive” (rate and depth of breathing)
Main factor is Chemical composition of plasma, (esp PaCO2)
PaO2 and plasma pH are secondary roles,
How do central chemoreceptors serve to regulate arterial PCO2 by monitoring the pH of CSF
Increasse in arterial PCO2. CO2 crosses into CSF CO2 +H20 - H2CO3 - H+ + HC3- Central Chemoreceptors respond to H+ Feedback via resp centers in the medulla to increase ventilation
How do peripheral chemoreceptors become important during hypoxia?
Detect changes in arterial PO2 (PaO2) and [H+]. Located in Carotid and aortic bodies.
Reflex stimulation of ventilation following significant fall in arterial PO2 (<60mmHg) (not O2 content)
Does this by low PO in blood vessel means no O2 combining with O2 sensor (KO2 channel) on cells. Therefore decrease in K+ permeability depolarising cell, causing exocytosis of dopamine cont. vesicles - attatch to dopamine receptor in sensory neuron which signals to medullary center to increase ventilation.
How are respiratory motor movements affected by CNS?
Which nerves are innervated to which muscles?
think CNS rep think interview nerve breaths - CV ME. Chemical comp of blood(Chemoreceptor input - most important), Vountary override, Mechano-sensorary, Emotion.
Resp centers (Pons and Medulla) have rhythm moulated by:
Emotion (via brains limbic system)
Voluntary over-ride (hgher centers in the brain)
Mechano-sensory input from the thorax (stretch reflex)
Chemical composition of the blood (PCO2, PO2 and pH), detected by chemoreceptors.
Inspiration : Phrenic nerve (diaphragm), intercostal nerves (external intercostal muscles).
From Pons and Medulla (resp. centers)
What are the 2 groups of neuros coming from the pons and medulla?
DRG - Dorsal Resp Group (goes to inspiratory muscles)
VRG - Ventral Respiratory Group pf Neurons (goes to Tounge, pharynx, larynx and expiratory muscles.
What are the 2 groups of neuros coming from the pons and medulla?
DRG - Dorsal Resp Group (goes to inspiratory muscles)
VRG - Ventral Respiratory Group pf Neurons (goes to Tounge, pharynx, larynx and expiratory muscles.
What is Hypercapnea?
raised CO2
What is Hypercapnea?
raised CO2
What do people with Chronic lung disease become reliant on to stimulate ventilation?
Changes in PaO2 (and therefore peripheral chemoreceptors) as PaCO2 can become chronically elevated and therefore desensitised to PCO2 changes.
What affect do most anasthetic agenst have on RR, TV and AV?
Increase RR, decrease TV and therefore decrease AV
What affect do most anasthetic agenst have on RR, TV and AV?
Increase RR, decrease TV and therefore decrease AV
How do Barbiturates and OPiods affect respiratory centers?
They depress respiratory centers, decreasing sensitivity to pH and therefore responce to PCO2. Also decreases peripheral chemoreceptor response to low PO2.
How do Barbiturates and OPiods affect respiratory centers?
They depress respiratory centers, decreasing sensitivity to pH and therefore responce to PCO2. Also decreases peripheral chemoreceptor response to low PO2.
What is Nitrous oxide used for? How does it work? When would it be problematic?
Common sedative/light anasthetic agent. Blunts peripheral chemoreceptors response to falling PaO2..
Ploblematic in Chronic Lung Disease as they are often reliant on “hypoxic drive” (peripheral chemoreceptors to kick in due to chronic high levels of PCO2). Administering O2 aggrevates situation.
Additionally to a change in PO2 what else do the peripheral Chemoreceptors detect?
Also respond to increasing plasma [H+]
[H+] often comes form CO2 :
CO2 +H20 = H2CO3 = HCO3- + H+