6.2 Regulation of Gas Concentrations

Cellular Respiration

Occurs in cells to provide energy for its functions

Cellular Respiration Word Equation

Oxygen + Glucose → Carbon Dioxide + Water + Energy

Cellular Respiration Molecular Equation

6O2 + C6H12O6 → 6CO2 + 6H2O + Energy

Muscles that cause air to move in and out of the lungs are

The diaphragm (separates the thorax from the abdomen), The intercostal muscles, the muscles between the ribs.

Diaphragm and IM are…

skeletal muscles and require stimulation from nerve impulses to initiate contraction.

Which nerve is connected to the diaphragm…

Phrenic Nerve

Which nerve is connected to the Intercostal Muscles?

Intercostal Nerves

Breathing Nerves→ Phrenic Nerve + IM Nerves

Origin at the spinal cord in the neck and thorax level. Nerve impulses controlled by a respiratory centre located in the medulla oblongata of the brain.

Respiratory Centre

Two regions within the respiratory centre, expiration control and inspiration control to coordinate messages are sent back and forth between these regions.

Peripheral Chemoreceptors→ Aortic and Carotid bodies

groups of cells within walls of the aorta and carotid arteries that are sensitive to changes in the concentration of oxygen, carbon dioxide and hydrogen ions

Central Chemoreceptors

Located in the medulla oblongata, sensitive to changes in the concentration of carbon dioxide in the blood and Hydrogen ion in the cerebrospinal fluid.

When chemoreceptors are stimulated…

They send nerve impulses to the urea of the respiratory centre that regulates breathing.

Oxygen Concentration

oxygen is consumed by cells, its concentration in the blood begins to fall. If concentration of oxygen begins to fall below normal while other factors are held constant, the breathing rate increases. However, within normal range of blood oxygen concentration the effect on breathing rate is only slight.

Low Oxygen Concentration

Large decrease in oxygen concentration stimulates the peripheral chemoreceptors and nerve impulses are transmitted to the respiratory centre. Nerve impulses stimulate the transmission of message to the diaphragm and intercostal muscles and so the breathing rate and depth increases.

Carbon dioxide concentration

Carbon dioxide is a major factor in regulating breathing rate. A relatively small increase in the concentration of Carbon dioxide is enough to cause a marked increase in the rate and depth of breathing.

Increase in Carbon dioxide and Hydrogen ions concentration…

stimulates the central and peripheral chemoreceptors, these in turn transmit nerve impulse to the respiratory centre resulting in an increase in breathing rate and depth.

Hydrogen Ion concentration

Hydrogen ion concentration increases, meaning that pH decreases, directly stimulating chemoreceptors in the aortic and carotid bodies which then transmit impulses to the respiratory centre, resulting in an increase in the breathing rate and depth.