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Human Physiology Gas Exchange Notes

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HUMAN PHYSIOLOGY Gas Exchange

6.4.1 Distinguish between ventilation, gas exchange and cell respiration.(2)

1. Ventilation:

The flow of air in and out of the lungs

Two stages: inspiration (or inhalation) and expiration (or exhalation).

Lungs are not muscular and cannot ventilate themselves - movement controlled by intercostal muscles and diaphragm.

2. Gas Exchange:

This is the diffusion of gases (oxygen and carbon dioxide) to and form the blood at the alveoli and respiring tissues

Alveoli: Oxygen diffuses into the blood from the alveoli and carbon dioxide diffuses from the blood into the alveoli

Tissues: Oxygen diffuses from blood into the cells and carbon dioxide diffuses from cells to the blood

3. Cell Respiration

Production of ATP at the cellular level

Aerobic respiration (mitochondria) = oxygen and produces carbon dioxide

Anaerobic respiration = no oxygen and still produces carbon dioxide

6.4.2 Explain the need for a ventilation system (3)

Large organisms - oxygen and waste products cannot diffuse into and out of cells to and from the directly

Ventilation system ensures blood can be medium to deliver nutrients and remove waste

To maintain a large concentration gradient between alveoli and blood If alveoli is not ventilated, equilibrium would be reached - gas could not be exchanged

Air flow (breathing out) : CO2 concetration in alveoli kept low so it diffuses out of the blood

Airflow (breathing in) : Keeps O2 concetration in alveoli high

Blood flow : blood with high CO2 concentrartion and low O2

This means oxygen can always diffuse down its concentration gradient from the air to the blood, while at the same time carbon dioxide can diffuse down its concentration gradient from the blood to the air.

Humans = Land born

Gases need moist surfaced (membraines) in order to diffuse

Lungs = moist membrane allowing O2 and CO2 to diffuse in and out of blood

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