PSL301: Respiratory 4 Flashcards
What is responsible for feedback regulation of breathing?
Chemoreceptors sense pCO2 and pO2 levels
-> chemoreflex
In response to chemoreflex, what changes?
ventilation
Graph of arteriole pCO2 and ventilation rate is in what shape? What is it called?
hyperbola downards
metabolic hyperbola
What does the shape of the metabolic hyperbola depend on?
rate of production of CO2 by metabolism
How is CO2 and O2 monitored?
chemoreceptors
2 types of chemoreceptors
- central
2. peripheral
Central chemoreceptors are located…
in medulla oblongata & other brain tissue
Central chemoreceptors detect…
[H+] in cerebrospinal fluid
caused by increased pCO2 in cerebral capillaries
peripheral chemoreceptors are located in…
carotid (mainly) & aortic arteries
peripheral chemoreceptors detect…
[H+] in blood
low plasma O2
caused by increased plasma CO2 & decreased plasma O2
what increases sensitivity of peripheral chemoreceptors?
decreased pO2
The sensitivity of __ is dependent on pO2 levels
peripheral chemoreceptors
After medulla receives info from chemoreceptors, how does it respond?
via somatic motor neurons that go to intercostals and diaphragm
How long does it take for central chemoreceptors to respond?
5 min
How do central chemoreceptors send signal?
H+ blocks K+ channels, and causes depolarization in the chemoreceptor
an increase in H+ is associated with…
increased plasma pCO2
Relationship between pCO2 and ventilation
linear; proportional
__ chemoreflex provides most of our drive to breathe
central
when is central chemoreflex not used?
during emergencies
why is hyperventilating before diving dangerous?
- increase pO2
- this decreases sensitivity of peripheral chemoreceptors to high pCO2
- will not easily send signal to respiratory control centers
How is peripheral chemoreceptor activity modulated by low O2?
- O2 enters the glomus cell in carotid
- low pO2 causes K+ channels to close
- cell depolarization
- Ca++ gates open and enter cell
- Ca++ cause exocytosis of dopamine
- bind to dopamine receptor on sensory neuron
- sends AP to medulla
- increase ventilation
What NT does O2 need to send signals to medulla?
dopamine
what cell must O2 enter to send signals to medulla?
glomus cell
Where does the conversion to bicarb take place in the brain?
cerebrospinal fluid
Relationship between H+, HCO2-, pCO2 is called…
Henderson-Hasselbalch equation
Henderson-Hasselbalch equation
24 pCO2 / [HCO3-]
Normal value for [H+]
40 nmol/L
Normal value for pCO2
40 mmHg
Normal value for [bicarb]
24 mmol/L
How much acid is removed by respiratory system per day? What is removed?
10 000 mmol carbonic acid
How much acid is removed by renal system per day? What is removed?
100 mmol of fixed acids
Things that may cause respiratory acidosis
- lung disease
- overdose of sedatives
things that may cause metabolic acidosis
- methanol poisoning
- ketoacidosis
- diarrhea
things that may cause respiratory alkalosis
- hyperventilation
- aspirin poisoning
things that may cause metabolic alkalosis
- vomitting
Compensation for acidosis
- increased respiratory rate
- kidney secretes H+ as NH4+ / combined with buffers
- kidney generate bicarb
- buffer systems absorb H+
Compensation for alkalosis
- decreased respiratory rate
- kidney get rid of bicarb
- buffer systems release H+
