ACUTE RESPONSES OF THE RESPIRATORY SYSTEM

Question 1

RESPIRATORY RESPONSES

Answer 1

cute responses of the respiratory system to exercise are designed to facilitate an increase in the availability of oxygen and the removal of carbon dioxide.

Question 2

Types of responses

Answer 2

• increased respiratory rate (breathing rate)
• increased tidal volume
• increased ventilation
• Increased pulmonary diffusion.

Question 3

INCREASED RESPIRATORY RATE (BREATHING RATE)

Answer 3

Respiratory rate refers to the number of breaths taken per minute. At rest, the average respiratory rate is around 12 breaths per minute. When exercise begins, breathing rates rise sharply and can increase to as high as 35–50 breaths per minute.
- This increase in respiratory rate is triggered by the increase in carbon dioxide concentrations in the blood, which stimulates the respiratory control centre in the brain.

Question 4

INCREASED TIDAL VOLUME

Answer 4

—> The depth of breathing (tidal volume (TV)) increases from around 0.5 litres per breath at rest to as high as 3–5 litres per breath at maximal workloads.

Question 5

INCREASED VENTILATION

Answer 5

Ventilationis the amount of air inspired or expired per minute by the lungs. It is the product of respiratory rate multiplied by tidal volume.
ventilation(V)=respiratoryrate×tidalvolume(L/min)(breaths/min)(L/breath)

At rest, ventilation is around 5–6 litres per minute. During maximal exercise, it may increase beyond 180 litres per minute for males, and 130 litres per minute for females. This is 25 to 35 times greater than resting values. It should be noted that both tidal volume and ventilation are generally higher for males because of their larger average lung volume.

Question 6

Mechanisms responsible for increased ventilation:

Answer 6

With its rapid onset, the initial adjustment of ventilation to the increased oxygen demands of exercise is neural in nature, controlled by the respiratory control centres in the brain, with additional neural input from receptors within the exercising muscles. As exercise progresses, further adjustments in ventilation are controlled primarily by changes in the chemical status of arterial blood.
- Increased muscle metabolism due to exercise results in the production of greater levels of carbon dioxide and hydrogen ions, which are sensed within the blood by chemoreceptors located in the brain and lungs.

Question 7

INCREASED PULMONARY DIFFUSION

Answer 7

—> Pulmonary diffusionis the process of gaseous exchange that takes place within the lungs. Pulmonary diffusion has two major functions:
- to replenish oxygen supply through diffusion from alveolar to pulmonary capillaries
- to remove carbon dioxide from returning venous blood.
At rest, oxygen diffusion capacity is about 21 millilitres of oxygen per minute. During maximal exercise, the oxygen diffusion capacity may increase by up to three times the resting rate.