3 week 15 Flashcards
what is air composed of? what pressure does it exert?
- Air = Nitrogen (79%) + Oxygen (21%) + Carbon dioxide (0.03%)
- 760 mm Hg at sea level
how do you calculate the partial pressure of a single gas? what is PO2 and PCO2?
- Pgas = %gas x Ptotal
- Ptotal = 760 unless otherwise stated
- PO2 = 160mmHg
- PCO2 = 0.23mmHg
T or F: atmospheric pressure increases as you move to higher altitudes
false – decreases *
how would you calculate the PO2 of air that has just entered the lungs?
- PO2 = (760mmHg - 47mmHg) x 0.21 = 149mmHg
- pressure decreased bc air is humidified
what are the partial pressures of O2 and CO2 in the alveoli? why are they diff than what they are in the atmosphere?
- PO2 = 100mmHg (lower bc not ALL air exchanged w every breath)
- PCO2 = 40mmHg (higher bc body constantly makes CO2 which also enters alveoli)
in gas mixtures, gases diffuse ___ their partial pressure gradient. eventually reaches an equilibrium where partial pressure of ___ and ___ gases are equal.
- down (high to low pressure)
- vaporized, dissolved
is CO2 more soluble in water or air?
water
what is PO2 and PCO2 in…
a) alveolar air
b) arterial blood (exiting lungs/entering tissues)
c) venous blood (entering lungs/exiting tissues)
d) tissues
a) PO2 = 100mmHg, PCO2 = 40mmHg
b) PO2 = 100mmHg, PCO2 = 40mmHg
c) PO2 = 40mmHg, PCO2 = 46mmHg
d) PO2 = 40mmHg, PCO2 = 46mmHg
how is oxygen transported in the blood?
- 98.5% via hemoglobin
- 1.5% dissolved in plasma
a) in arterial blood (exiting lungs/entering tissues), hemoglobin is ___% saturated with oxygen
b) in venous blood (entering lungs/exiting tissues) hemoglobin is ___% saturated with oxygen
a) 98.5
b) 75
the hemoglobin-oxygen dissociation curve demonstrates that small changes in pressure have ___ effects on unloading of oxygen
big!
what does a shift in either direction do for affinity? what factors cause shifts to the right? to the left?
- shift to the right = decreased affinity/more oxygen unloading at tissues
- caused by +temp, -pH, +PCO2, and +2,3 BPG
- shift to the left = increased affinity/less oxygen unloading at tissues
- caused by -temp, +pH, -PCO2, and -2,3 BPG
what is the relationship bw H+ and pH? what is the effect of pH on affinity called?
- more H+ = lower pH
- Bohr effect
what is 2,3 BPG?
- produced in RBC under low oxygen (eg anemia, high altitude)
- decreases affinity of hemoglobin for oxygen enhancing oxygen unloading
how is carbon dioxide transported in the blood?
- 5-6% dissolved in plasma
- 5-8% bound to hemoglobin to form carbaminohemoglobin
- 86-90% converted to bicarbonate in RBC, then transported in plasma
how is carbon dioxide converted to bicarbonate?
- carbon dioxide and water combine to form carbonic acid. then, carbonic acid dissociates into protons and bicarbonate.
- note: reaction is reversible and carbonic anhydrase in RBC catalyzes first part of reaction.
what happens at the tissues regarding this equation?
- shifts to right
- carbonic acid moves out of RBC in exchange for chloride (= chloride shift)
what happens at the lungs regarding this equation?
- shifts to left
- carbonic acid moves into RBC in exchange for chloride (= reverse chloride shift)
what is the haldane effect?
- as PO2 increases, the total amount of CO2 in the blood decreases
- promotes CO2 being released into alveoli
which nerves regulate the external intercostal muscles? the diaphragm?
intercostal nerves, phrenic nerves
action potentials occur in the ___ during inspiration of QUIET BREATHING
- phrenic nerves (diaphragm contracts)
- external intercostal nerves (external intercostal muscles contract)
action potentials cease in the ___ during expiration of QUIET BREATHING
- phrenic nerves (diaphragm relaxes)
- external intercostal nerves (external intercostal muscles relax)
action potentials occur in the ___ during inspiration of ACTIVE VENTILATION
- phrenic nerves (diaphragm contracts)
- external intercostal nerves (external intercostal muscles contract)
action potentials occur in the ___ during expiration of ACTIVE VENTILATION
- internal intercostal nerves (internal intercostal muscles contract)
- abdominal nerves and muscles
what do the respiratory control centers of medulla contain? (3)
- contain inspiratory + expiratory neurons
- contains a central pattern generator
- contains pre-motor neurons that influence activity of motor neurons of phrenic and intercostal nerves
what do the respiratory control centers of pons contain (1) and do (1)?
- contain inspiratory, expiratory, and mixed neurons (active during both)
- may regulate transitions between inspiration + expiration
what are the respiratory centers of the pons and medulla called?
- pons: pontine respiratory group
- medulla: VRG (contains expiratory + inspiratory neurons) and DRG (contains mainly inspiratory neurons)
what does the central pattern generator do? where is it located?
- drives the activity of other respiratory neurons
- pre-Botzinger complex in VRG
what are the 2 hypotheses for how rhythm is generated?
1) pacemaker
- neurons have intrinsic pacemaker activity
- spontaneously depolarize generating APs in a cyclical manner
2) neural network
- complex interactions between network of neurons generate rhythm
whats the diff bw central chemoreceptors and peripheral chemoreceptors?
CENTRAL:
- located in medulla oblongata and scattered in other brain tissue
- detect [H+] in cerebrospinal fluid
- NOT responsive to changes in PO2
PERIPHERAL:
- located in carotid (mainly) and aortic bodies
- detect [H+] in blood
- sensitivity is increased when PO2 falls
- afferent neurons project to medullary respiratory control areas
- direct contact with arterial blood
which chemoreceptor takes about 5 mins to respond fully to changes in arterial PCO2?
central (as CO2 increases, so does the amount of H+, lowering pH. central chemoreceptors respond to pH changes caused by PCO2)
what will happen to the breathing rate and depth if arterial PCO2 increases?
breathing increases (body wants to eliminate excess CO2 and restore normal pH levels)
T or F: central chemoreflexes kick in during emergencies e.g. drowning, choking
false not fast enough – peripherals used during emergencies
sensitivity of peripheral chemoreceptors for H+ increases when PO2 < ___ mmHg
60 (sensitivity increases when PO2 decreases)
how do chemoreflexes regulate acidosis and alkalosis?
ACIDOSIS (pH too low):
- chemoreceptors stimulated
- increased ventilation
- decrease of protons
- increase pH
ALKALOSIS (pH too high):
- less chemoreceptor stimulation
- decreased ventilation
- increase of protons
- decrease pH
how is air and blood flow regulated within the lungs?
- ventilation and perfusion are matched
- want Va / Q = 1
- Va = air flow, Q = blood flow
what if ventilation-perfusion is less than 1? greater than 1?
- less: blood not fully oxygenated (obstruction of airway)
- greater: waste of respiratory effort (obstruction of blood vessel)
what does increased PCO2 do to the…
a) bronchioles
b) pulmonary arterioles
what about decreased PCO2?
INCREASED PCO2:
a) bronchioles = dilation
b) pulmonary arterioles = weak constriction
DECREASED PCO2:
a) bronchioles = constriction
b) pulmonary arterioles = weak dilation
what does increased PO2 do to the…
a) bronchioles
b) pulmonary arterioles
what about decreased PO2?
INCREASED PO2:
a) bronchioles = weak constriction
b) pulmonary arterioles = dilation
DECREASED PO2:
a) bronchioles = weak dilation
b) pulmonary arterioles = constriction
define…
a) hyperpnea
b) dyspnea
c) apnea
d) tachypnea
a) hyperpnea: +ventilation to meet metabolic needs
b) dyspnea: laboured breathing
c) apnea: temporary cessation of breathing
d) tachypnea: rapid, shallow breathing
define…
a) hyperventilation
b) hypoventilation
a) hyperventilation: ventilation exceeds metabolic needs
b) hypoventilation: ventilation does not meet metabolic needs
define…
a) hypoxia
b) hypoxemia
c) hypercapnia
d) hypocapnia
a) hypoxia: deficiency of oxygen in tissues
b) hypoxemia: deficiency of oxygen in blood
c) hypercapnia: excess carbon dioxide in blood
d) hypocapnia: not enough carbon dioxide in blood
