Part VIII Flashcards
Where are peripheral chemoreceptors located?
aortic and carotid bodies
How much CO2 induces increase in ventilation?
20-30%
Are peripheral chemoreceptors responsive to CO2 or O2?
decreased O2 (hypoxia)
The response to hypoxia is blunted if what falls as oxygen levels fall?
CO2
Are peripheral chemoreceptors responsive to CO2?
a little, but not the same as a decrease in oxygen
Peripheral chemoreceptors are altered by what?
CNS
When the SNS decreases flow to the peripheral chemoreceptors, what happens?
There is an increase in sensitivity to hypoxia
What do we use the oxygen consumed after exercise?
to replenish oxygen stores and remove lactic acid
How much oxygen is stored in the body on a regular basis?
2L
Where is the extra oxygen stored?
.2L in lungs, 1L with hemoglobin, .3L muscle myoglobin
How fast is the oxygen store used during exercise?
2 minutes
How much oxygen debt can the body reach?
11.5L
After exercise, ventilation and oxygen uptake remain high until what?
oxygen is replaced
What is alactacid oxygen debt?
oxygen debt the first couple minutes post exercise to recondition the phosphagen system
What is lactic acid oxygen debt?
oxygen debt that occurs over 40 minutes post exercise to remove the lactic acid
What causes extreme fatigue?
lactic acid
What decreases as you ascend?
barometric pressure
What is normal PO2?
.21
At how many feet will blood “boil”?
47mmHg
What doesn’t change with altitude?
the concentration of oxygen
What do u acclimatized people suffer from?
Deterioration of nervous system function
What are the effects of hypoxia?
Sleepiness, false sense of well being, impaired judgement, clumsiness, blunted pain perception, decreased visual acuity, tremors, twitching, seizuers
What can occur during acute mountain sickness?
Cerebral edema, pulmonary edema
What is cerebral edema?
hypoxia + local vasodilation (systemic dilation)
What is pulmonary edema?
hypoxia + local vasoconstriction (lungs constrict to get air to better areas)
When exposed to low PO2 at high altitude, when does hypoxic stimulation of arterial peripheral chemorecetors?
immediately
Are central chemoreceptors affected by hypoxia?
no, only increase in CO2
What happens when you enter the hypoxic situation?
increased ventilation decreases CO2, which limits increase in ventilation as pH increases (respiratory alkalosis)
What happens when increased ventilation decreases CO2?
it limits the increase in ventilation as pH increases (respiratory alkalosis)
What happens when there is an increase in body pH?
inhibits ventilaiton and opposes the stimulatory effects of hypoxia on peripheral chemoreceptors
What happens after being hypoxic because of high altitudes after a couple days?
ventilation increases 5x as inhibition fades because excretion of HCO3 by kidneys
What happens when kidneys excrete HCO3?
it offsets decrease in CO2 to push pH back to normal. Now the hypoxic stimulation of chemoreceptors is no longer opposed by alkalosis and ventilation can increase 5 fold
What happens during chronic mountain sickness?
increase in red cell mass, increase pulmonary arterial blood pressure, enlarged right ventricle, decreased TPR, congestive heart failure, death if person is not removed to lower altitude
Why is an increase in red blood cell mass bad?
thicker blood, less O2 available, increased carrying capacity to better get O2 to tissues
What happens when people are acclimatized?
great increase in pulmonary ventlation increase in RBCs increase diffusing capacity of lungs increase tissue vascularity increase ability of tissues to use O2 increased synthesis of 2,3DPG
What does increase synthesis of 2,3 DPG do?
shifts oxy-hemoglobin dissociation curve to right, which is an advantage to the tissues, but not to the lungs
Where is there an incrase ability of tissues to use oxygen?
slight increase cell mitochondria
slight increase in cellular oxidative systems
What is different about people who have natural acclimization?
high rate of ventilatory capacity compared to body mass
increase size of right ventricle
shift in oxy-hemoglobin dissociation curve
What is hyperbarism?
when pulmonary capillary blood is exposed to extremely high alveolar gas pressures
Can the high pressures under the sea be lethal?
yes
