Relationship between rate of respiration and oxygen and carbon dioxide contents

• During vigorous exercise (eg:running)– Muscle cells need more oxygen and glucose to

release energy– Rate of respiration increase– O2 content decrease– CO2 content increase

• To supply more O2 and discharge more CO2;– Breathing rate increase– Heart beat increase– More O2 supplied – More CO2 removed

Human respiratory response and rate of respiration in different situations

• Resting point (normal rate):– Breathing rate range of 16 to 18 breaths per

minute– Heartbeat rate range 60 to 70 per minute.

• Vigorous activities (swimming, running etc):– Breathing rate increases up to 30 breaths per

minute (increase in ventilation rate)– Heartbeat rate increases to 120 beats per minute

• In fear:– Breathing and heartbeat rates increase to supply

O2 to meet demand of higher respiration rate in cells.

– Hormone adrenaline secreted by adrenal glands to increase heartbeat and breathing rate.

– More glucose and oxygen supplied to the muscles.

Regulatory mechanism of oxygen and carbon dioxide contents in the body• Breathing is an involuntary process which

is controlled by the respiratory center (located in the medulla oblongata of the brain)

Vigorous exercise• During vigorous exercise, partial pressure

of CO2 increases• Higher level of CO2 results in pH value

drop in blood and cerebrospinal fluid.• Drop in pH is detected by central

chemoreceptors (in medulla oblongata)

Central chemoreceptors send nerve impulses respiratory centre diaphragm and intercostal muscles respiratory muscles contract and relax faster increase breathing and ventilation rate.

Excess CO2 eliminated from the body Concentration of CO2 and pH value in

blood return to normal level.

Very high altitudes (O2 severely low)

• Peripheral chemoreceptors (aortic bodies and carotid bodies) also sensitive to CO2 content and pH of blood.

• Peripheral chemoreceptors are stimulated send nerve impulses respiratory centre respiratory muscles stimulated to contract and relax faster breathing and ventilation rates increase

• More O2 inhaled• O2 concentration returns to normal level