Physiology of the Respiratory System - Week 3

Pulmonary ventilation

Inhalation and exhalation of air.

External respiration

Exchange of gases between alveoli and pulmonary capillaries.

Internal respiration

Exchange of gases between systemic capillaries and tissue cells.

Boyle's Law

The pressure of a gas inside a container is inversely proportional to volume.

Surface tension of alveolar fluid

Reduced by surfactant in alveolar fluid to affect ventilation.

Compliance of lungs

Dependent on surface tension and lung elasticity.

Airway resistance

Related to the dilation or constriction of bronchioles.

Tidal volume

Air moved in and out of the lungs during normal breathing.

Inspiratory reserve volume

Air moved into the lungs beyond normal inspiration.

Expiratory reserve volume

Air moved out of the lungs beyond normal expiration.

Residual volume

Air remaining in the lungs after a maximal exhalation.

Inspiratory capacity

Air breathed in after a normal expiration (TV + IRV).

Vital capacity

All the air expelled after a maximal inhalation (IRV + TV + ERV).

Total lung capacity

Maximum volume of air held in the lungs (IRV + TV + ERV + RV).

Functional residual capacity

Air remaining in lungs after a normal expiration (ERV + RV).

Forced Vital Capacity (FVC)

Total volume of air forcibly exhaled after a maximal inhalation.

Forced Expiratory Volume in 1 Second (FEV1)

Volume of air exhaled during the first second of an FVC test.

Dalton's Law

Each gas in a mixture exerts its own pressure as if no other gas present.

Henry's Law

Gas dissolved in a liquid is proportional to partial pressure and solubility.

Oxygen transport in blood

1.5% dissolved in plasma and 98.5% bound to haemoglobin.

Carbon dioxide transport in blood

7% dissolved in plasma, 23% bound to haemoglobin, 70% as bicarbonate.

Dorsal Respiratory Group (DRG)

Innervates diaphragm and external intercostals during inhalation.

Ventral Respiratory Group (VRG)

Innervates accessory respiratory muscles during forceful breathing.

Pontine Respiratory Group

Modifies rhythm of breathing during exercise, speaking, and sleeping.

Central chemoreceptors

Monitor [H+] and PCO2 in cerebrospinal fluid.

Peripheral chemoreceptors

Monitor [H+], PCO2, and PO2 in blood.

Cortical influences on breathing

Allows voluntary control (e.g., breath holding) and involuntary modification from emotions.

Partial pressure

The pressure of a specific gas in a mixture of gases.

Total pressure equation

P Total = P gas 1 + P gas 2 + P gas 3

FEV1/FVC

percentage of air exhaled during the first second of a forced vital capacity test, relative to the total volume

Inhalation - Step 1

Inspiratory muscles contract

Inhalation - Step 2

Thoracic cavity volume increases

Inhalation - Step 3

Lungs are stretched and intrapulmonary volume increases

Inhalation - Step 4

Intrapulmonary pressure drops

Inhalation - Step 5

Air flows into the lungs

Exhalation - Step 1

Inspiratory muscles relax

Exhalation - Step 2

Thoracic cavity volume decreases

Exhalation - Step 3

Lungs recoil and intrapulmonary volume decreases

Exhalation - Step 4

Intrapulmonary pressure rises

Exhalation - Step 5

Air flows out of the lungs