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psl201: physiology > 3 week 15 > Flashcards

3 week 15 Flashcards

1
Q

what is air composed of? what pressure does it exert?

A
  • Air = Nitrogen (79%) + Oxygen (21%) + Carbon dioxide (0.03%)
  • 760 mm Hg at sea level
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2
Q

how do you calculate the partial pressure of a single gas? what is PO2 and PCO2?

A
  • Pgas = %gas x Ptotal
  • Ptotal = 760 unless otherwise stated
  • PO2 = 160mmHg
  • PCO2 = 0.23mmHg
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3
Q

T or F: atmospheric pressure increases as you move to higher altitudes

A

false – decreases *

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4
Q

how would you calculate the PO2 of air that has just entered the lungs?

A
  • PO2 = (760mmHg - 47mmHg) x 0.21 = 149mmHg
  • pressure decreased bc air is humidified
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5
Q

what are the partial pressures of O2 and CO2 in the alveoli? why are they diff than what they are in the atmosphere?

A
  • PO2 = 100mmHg (lower bc not ALL air exchanged w every breath)
  • PCO2 = 40mmHg (higher bc body constantly makes CO2 which also enters alveoli)
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6
Q

in gas mixtures, gases diffuse ___ their partial pressure gradient. eventually reaches an equilibrium where partial pressure of ___ and ___ gases are equal.

A
  • down (high to low pressure)
  • vaporized, dissolved
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7
Q

is CO2 more soluble in water or air?

A

water

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8
Q

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

a) PO2 = 100mmHg, PCO2 = 40mmHg
b) PO2 = 100mmHg, PCO2 = 40mmHg
c) PO2 = 40mmHg, PCO2 = 46mmHg
d) PO2 = 40mmHg, PCO2 = 46mmHg

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9
Q

how is oxygen transported in the blood?

A
  • 98.5% via hemoglobin
  • 1.5% dissolved in plasma
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10
Q

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

a) 98.5
b) 75

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11
Q

the hemoglobin-oxygen dissociation curve demonstrates that small changes in pressure have ___ effects on unloading of oxygen

A

big!

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12
Q

what does a shift in either direction do for affinity? what factors cause shifts to the right? to the left?

A
  • 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
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13
Q

what is the relationship bw H+ and pH? what is the effect of pH on affinity called?

A
  • more H+ = lower pH
  • Bohr effect
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14
Q

what is 2,3 BPG?

A
  • produced in RBC under low oxygen (eg anemia, high altitude)
  • decreases affinity of hemoglobin for oxygen enhancing oxygen unloading
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15
Q

how is carbon dioxide transported in the blood?

A
  • 5-6% dissolved in plasma
  • 5-8% bound to hemoglobin to form carbaminohemoglobin
  • 86-90% converted to bicarbonate in RBC, then transported in plasma
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16
Q

how is carbon dioxide converted to bicarbonate?

A
  • 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.
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17
Q

what happens at the tissues regarding this equation?

A
  • shifts to right
  • carbonic acid moves out of RBC in exchange for chloride (= chloride shift)
18
Q

what happens at the lungs regarding this equation?

A
  • shifts to left
  • carbonic acid moves into RBC in exchange for chloride (= reverse chloride shift)
19
Q

what is the haldane effect?

A
  • as PO2 increases, the total amount of CO2 in the blood decreases
  • promotes CO2 being released into alveoli
20
Q

which nerves regulate the external intercostal muscles? the diaphragm?

A

intercostal nerves, phrenic nerves

21
Q

action potentials occur in the ___ during inspiration of QUIET BREATHING

A
  • phrenic nerves (diaphragm contracts)
  • external intercostal nerves (external intercostal muscles contract)
22
Q

action potentials cease in the ___ during expiration of QUIET BREATHING

A
  • phrenic nerves (diaphragm relaxes)
  • external intercostal nerves (external intercostal muscles relax)
23
Q

action potentials occur in the ___ during inspiration of ACTIVE VENTILATION

A
  • phrenic nerves (diaphragm contracts)
  • external intercostal nerves (external intercostal muscles contract)
24
Q

action potentials occur in the ___ during expiration of ACTIVE VENTILATION

A
  • internal intercostal nerves (internal intercostal muscles contract)
  • abdominal nerves and muscles
25
Q

what do the respiratory control centers of medulla contain? (3)

A
  • contain inspiratory + expiratory neurons
  • contains a central pattern generator
  • contains pre-motor neurons that influence activity of motor neurons of phrenic and intercostal nerves
26
Q

what do the respiratory control centers of pons contain (1) and do (1)?

A
  • contain inspiratory, expiratory, and mixed neurons (active during both)
  • may regulate transitions between inspiration + expiration
27
Q

what are the respiratory centers of the pons and medulla called?

A
  • pons: pontine respiratory group
  • medulla: VRG (contains expiratory + inspiratory neurons) and DRG (contains mainly inspiratory neurons)
28
Q

what does the central pattern generator do? where is it located?

A
  • drives the activity of other respiratory neurons
  • pre-Botzinger complex in VRG
29
Q

what are the 2 hypotheses for how rhythm is generated?

A

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

30
Q

whats the diff bw central chemoreceptors and peripheral chemoreceptors?

A

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

31
Q

which chemoreceptor takes about 5 mins to respond fully to changes in arterial PCO2?

A

central (as CO2 increases, so does the amount of H+, lowering pH. central chemoreceptors respond to pH changes caused by PCO2)

32
Q

what will happen to the breathing rate and depth if arterial PCO2 increases?

A

breathing increases (body wants to eliminate excess CO2 and restore normal pH levels)

33
Q

T or F: central chemoreflexes kick in during emergencies e.g. drowning, choking

A

false not fast enough – peripherals used during emergencies

34
Q

sensitivity of peripheral chemoreceptors for H+ increases when PO2 < ___ mmHg

A

60 (sensitivity increases when PO2 decreases)

35
Q

how do chemoreflexes regulate acidosis and alkalosis?

A

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

36
Q

how is air and blood flow regulated within the lungs?

A
  • ventilation and perfusion are matched
  • want Va / Q = 1
  • Va = air flow, Q = blood flow
37
Q

what if ventilation-perfusion is less than 1? greater than 1?

A
  • less: blood not fully oxygenated (obstruction of airway)
  • greater: waste of respiratory effort (obstruction of blood vessel)
38
Q

what does increased PCO2 do to the…
a) bronchioles
b) pulmonary arterioles

what about decreased PCO2?

A

INCREASED PCO2:
a) bronchioles = dilation
b) pulmonary arterioles = weak constriction

DECREASED PCO2:
a) bronchioles = constriction
b) pulmonary arterioles = weak dilation

39
Q

what does increased PO2 do to the…
a) bronchioles
b) pulmonary arterioles

what about decreased PO2?

A

INCREASED PO2:
a) bronchioles = weak constriction
b) pulmonary arterioles = dilation

DECREASED PO2:
a) bronchioles = weak dilation
b) pulmonary arterioles = constriction

40
Q

define…
a) hyperpnea
b) dyspnea
c) apnea
d) tachypnea

A

a) hyperpnea: +ventilation to meet metabolic needs
b) dyspnea: laboured breathing
c) apnea: temporary cessation of breathing
d) tachypnea: rapid, shallow breathing

41
Q

define…
a) hyperventilation
b) hypoventilation

A

a) hyperventilation: ventilation exceeds metabolic needs
b) hypoventilation: ventilation does not meet metabolic needs

42
Q

define…
a) hypoxia
b) hypoxemia
c) hypercapnia
d) hypocapnia

A

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

psl201: physiology (21 decks)

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