Chapter 17: The Respiratory System: Gas Exchange and Regulation of Breathing

gas exchange

the process of obtaining oxygen from the environment and releasing carbon dioxide

Dalton's Law

at constant volume and temperature, the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of the component gases

partial pressure

the contribution each gas in a mixture makes to the total pressure

PO2

partial pressure of oxygen

PCO2

partial pressure of carbon dioxide

Henry's Law

At a given temperature the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid

alveoli

tiny sacs of lung tissue specialized for the movement of gases between air and blood

respiratory membrane

where gas exchange occurs between the air on the alveolar side and the blood on the capillary side; the alveolar and capillary walls form the respiratory membrane

pulmonary arteries

the vessels that carry deoxygenated blood from the right ventricle of the heart to the lungs

pulmonary veins

carry the oxygenated blood from the lungs into the left atrium of the heart

alveolar ventilation

the amount of air that reaches the alveoli

hyperpnea

excessive breathing

dyspnea

difficult or labored breathing

apnea

temporary cessation of breathing

tachypnea

rapid breathing

hyperventilation

the condition of taking abnormally fast, deep breaths

hypoventilation

ventilation of the lungs that does not fulfill the body's gas exchange needs

hypoxia

deficiency in the amount of oxygen reaching the tissues

hypoexmia

deficient amount of oxygen in the blood

hypercapnia

excessive carbon dioxide in the blood

hypocapnia

condition of deficient carbon dioxide (in the blood)

deoxyhemoglobin

hemoglobin without oxygen

oxyhemoglobin

hemoglobin bound to oxygen

law of mass action

The rate of a chemical reaction is proportional to the product of the concentrations of the reactants

hemoglobin saturation

percentage of heme units containing bound oxygen

hemoglobin-oxygen dissociation curve

a curve that plots the proportion of hemoglobin in its saturated (oxygen-laden) form on the vertical axis against the prevailing oxygen tension on the horizontal axis

right shift

A shift of the curve to the right indicates decreased affinity of the hemoglobin for oxygen and hence an increased tendency to give up oxygen to the tissues

left shift

A shift to the left indicates increased affinity and so an increased tendency for hemoglobin to take up and retain oxygen.

Bohr effect

describes hemoglobin's lower affinity for oxygen secondary to increases in the partial pressure of carbon dioxide and/or decreased blood pH. This lower affinity, in turn, enhances the unloading of oxygen into tissues to meet the oxygen demand of the tissue

carbaminohemoglobin

the compound formed by the union of carbon dioxide with hemoglobin

carbamino effect

Describes a change in the confirmation of hemoglobin that is induced by an increase in CO2

BPG (biphosphoglycerate)

also known as 2,3-Disphosphoglycerate (2,3-DPG), promotes hemoglobin transition from a high-oxygen-affinity state to a low-oxygen-affinity state

carbon monoxide

a colorless, odorless toxic flammable gas formed by incomplete combustion of carbon.

carbonic anhydrase

enzyme that catalyzes the reaction between carbon dioxide and water to form carbonic acid

bicarbonate ions

enzyme that changes carbon dioxide into water so it is not poisonous to the body

chloride shift

the movement of chloride ions into the red blood cells as hydrogen ions move out

to maintain the electrochemical equilibrium.

Haldane effect

Oxygenation of blood in the lungs displaces carbon dioxide from hemoglobin which increases the removal of carbon dioxide.

respiratory centers

autonomic centers located in the medulla oblongata and the pons that establish breathing rate and depth

brainstem

the oldest part and central core of the brain, beginning where the spinal cord swells as it enters the skull; the brainstem is responsible for automatic survival functions

inspiratory neurons

depolarize during inspiration

somatic motor neurons

nerve cells whose cell bodies are in the brainstem and spinal cord that serve skeletal muscles

phrenic nerve

Carries impulses to the diaphragm from the brain.

diaphragm

Large, flat muscle at the bottom of the chest cavity that helps with breathing

external intercostal nerve

originating in thoracic segments of the spinal cord

external intercostal muscles

A muscle that raises the rib cage, decreasing pressure inside the chest cavity

expiratory neurons

fire during forced expiration

medulla oblongata

Part of the brainstem that controls vital life-sustaining functions such as heartbeat, breathing, blood pressure, and digestion.

pons

A brain structure that relays information from the cerebellum to the rest of the brain

central chemoreceptors

brainstem neurons that respond to changes in pH of cerebrospinal fluid

peripheral chemoreceptors

sensory receptor cells located in the aortic arch and carotid arteries that are sensitive to changes in blood oxygen level

CSF

cerebrospinal fluid

carotid bodies

chemoreceptors located in the internal carotid artery; respond to changes in arterial PO2, PCO2, and pH

ventilation-perfusion coupling

matching of alveolar ventilation with pulmonary blood perfusion

ventilation

movement of air in and out of the lungs

perfusion

The supply of oxygen to and removal of wastes from the cells and tissues of the body as a result of the flow of blood through the capillaries.

Alveolar PO2

partial pressure of oxygen in the alveoli (usually around 100 mmHg)

bronchoconstriction

Constriction, or blockage, of the bronchi that lead from the trachea to the lungs.

bronchodilation

expansion of the bronchial air passages

Blood pH

7.35-7.45

acidosis

excessive acidity of body fluids

alkalosis

The buildup of excess base (lack of acids) in the body fluids.

buffers

weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes in pH

respiratory acidosis

A drop in blood pH due to hypoventilation (too little breathing) and a resulting accumulation of Co2.

respiratory alkalosis

Arise in blood pH due to hyperventilation (excessive breathing) and a resulting decrease in CO2.

metabolic acidosis

decreased pH in blood and body tissues as a result of an upset in metabolism

metabolic alkalosis

elevation of HCO3- usually caused by an excessive loss of metabolic acids

arterial blood gas

a diagnostic test examining arterial blood; used to determine the pressure exerted by oxygen and carbon dioxide in the blood

pulse oximeter

an external monitor placed on the patient's finger or earlobe to measure the oxygen saturation level in the blood

capnograph

A device that measures expired CO2 levels