The Control of Breathing SBI3U(G) PDF
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This document covers the control of breathing, including the roles of the brain and chemical receptors in regulating breathing rate. It also examines factors affecting breathing rate, such as strenuous activity, poor ventilation, illness, and high altitude.
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The Control of Breathing SBI3U(G) Breathing Rate ⚪ How quickly/slowly you inhale/exhale. ⚪ The average number of breaths per minute is 12 - 20 for a healthy adult. ⚪ The breathing rate must change to respond to changes in oxygen demand or availability. Role of th...
The Control of Breathing SBI3U(G) Breathing Rate ⚪ How quickly/slowly you inhale/exhale. ⚪ The average number of breaths per minute is 12 - 20 for a healthy adult. ⚪ The breathing rate must change to respond to changes in oxygen demand or availability. Role of the Brain ⚪ Breathing is involuntary The medulla oblongata in the brain stem controls the breathing rate. ⚪ Impulses from higher brain centres that are under voluntary control can override these signals temporarily Role of the Brain ⚪ Brain stem sends nerve impulses via the spinal column to the nerves supplying the muscles of the diaphragm and rib cage causing: Diaphragm and external intercostal muscles to contract Stretch receptors from intercostals sends signal back to the brain that inhalation has taken place Brain stops signalling inhalation, relaxation triggers exhalation. What determines breathing rate? 1. Level of CO2 in the blood ⚪ Primary mechanism ⚪ Chemical receptors in the brain, a major artery of the neck (carotid), and heart (aorta) are sensitive to the concentration of CO2 in the blood they detect a decrease in the pH of the plasma due to excess carbonic acid ⚪ Brain signals an increase in breathing rate and volume of inhalation CO2 + H2O 🡪 H2CO3 🡪 HCO3- + H+ carbonic acid bicarbonate ion What determines breathing rate? 2. Level of O2 ⚪ Secondary mechanism ⚪ Receptors in arteries monitor level of O2 in the blood leaving the heart and going to the brain ⚪ Will only trigger an increase when O2 levels fall very far below normal (CO2 levels will trigger change first) Factors Affecting Breathing Rate? ⚪ Strenuous activity increases B.R. (need more oxygen) ⚪ Poorly ventilated room increases B.R. (no fresh air, increased [CO2] causes B.R. to increase) ⚪ Sickness – colds and emphysema decrease efficiency. B.R. ↑ ⚪ High altitude – less oxygen and reduced air pressure. B.R. ↑
