Chapter 18- Gas Exchange

partial pressure gradients

what drives the movement of gases across cell membranes?

alveoli, blood

Oxygen diffuses from ________ to _______

from cells to alveoli

what direction does CO2 diffuse?

partial pressure

Pressure exerted by single gases in a mixture

hypercapnia

high blood CO2 levels

hypoxia

low tissue O2 levels

hypoxic hypoxia

low arterial PO2

histotoxic hypoxia

- failure to use O2
-caused by metabolic poisons (cyanide)

anemic hypoxia

-decreased Hb-O2
- caused by blood loss, CO, others

Ischemic hypoxia

-reduced blood flow
- caused by heart failure, shock, blood clot

altitude

what determines composition of inspired air?

decreased compliance, increased resistance, CNS depression

what can cause hypoventilation?

hypoventilation

occurs when lower volumes are reaching lungs

type I pneumocytes and capillary endothelium

what makes up the respiratory membrane?

how easily gas moves from air to liquid

what determines gas solubility?

CO2

does O2 or CO2 have higher solubility?

when partial pressures are equal causing no net movement

when do gasses reach equilibrium?

2

Oxygen dissolves into blood plasma but only <__% total O2 is in plasma

oxyhemoglobin

hemoglobin bound reversibly to oxygen

how much O2 is bound to hemoglobin

what does hemoglobin saturation measure?

4

how many O2 molecules can bind to each hemoglobin?

HbO2 Saturation

represented by oxyhemoglobin saturation curve

98%

Hb saturation at normal Arterial PO2

75%

Hb saturation at resting cell PO2

35%

Hb saturation at exercising muscle PO2

bohr effect

a shift in saturation that results from change in pH

facilitates unloading of oxygen so more is available to metabolically active tissues

what is the effect of decreased pH on O2 supply in the body?

increased

_________ CO2 levels will result in greater metabolic activity and unloading of oxygen

higher

_________ temperatures also facilitates unloading of O2

2,3 biphosphoglycerate

-glycolysis intermediate due to chronic hypoxia
-Facilitates unloading

bicarbonate

what form is the majority of CO2 being transported through the bloodstream in?

ventilation

process that brings oxygen to lungs

oxygen, CO2

Gas Exchange at alveoli brings _______ in, _________ out

closing of oxygen sensitive K+ channels

what is the initial action by chemoreceptors to control breathing?

positive K+ is blocked from leaving the cell

what causes cell depolarization?

vg-Ca2+ channels open

what happens due to cell depolarization during breathing control?

Ca2+ influx

what causes the exocytosis of neurotransmitters which produces an action potential?

central chemoreceptors

chemoreceptors locaters in the medulla near control centers

CO2 levels

what do central chemoreceptors monitor?

O2 levels

what do peripheral chemoreceptors monitor?

speeds ventilation

how does an increase in CO2 levels affect breathing?

slows ventilation

how does a decrease in CO2 levels affect breathing?

involuntary, rhythmic, voluntary

ventilation is a ___________ , ___________ system that can be modified by _________ control

chemoreceptors

sensors that regulate ventilation

medulla and pons

integrate all sensory and cognitive input and control muscles of inspiration