Gas regulation

Question 1

Stimuli for regulation of breathing

Answer 1

Increased carbon dioxide, Decreased pH and increased bicarbonate ions, Decreased oxygen

Question 2

Changes in carbon dioxide

Answer 2

Increased CO2 concentration results in an increase in H+ concentration (decreased pH) and an increase in bicarbonate ions, When metabolic rates increases to supply more energy to cells the amount of carbon dioxide produced increases, Carbonic acid breaks down into hydrogen and bicarbonate ions (H20 + CO2 (in blood) <—> H2CO3 (carbonic acid-toxic) <—> H+ + HCO3-), Medullary chemoreceptors in the respiratory centre detect changes to CO2 concentration

Question 3

Changes in hydrogen ion concentration

Answer 3

As hydrogen ion concentration increases, pH decreases whilst there is an increase in bicarbonate ions, Low pH and increased bicarbonate ions are detected by the aortic and carotid chemoreceptors in the aortic body and carotid body

Question 4

Detecting changes in oxygen levels

Answer 4

Both the aortic and carotid chemoreceptors and medullary chemoreceptors detect a very low level of oxygen

Question 5

Increased carbon dioxide feedback loop

Answer 5

Stimulus- Increased carbon dioxide, Receptor- Medulla chemoreceptors in the respiratory centre, Modulator- Medulla, Medulla serves a nerve impulse via the phrenic and intercostal nerves to the effector, Effector- Diaphragm and intercostal muscles, Diaphragm and intercostal muscles contract causing the response, Response- Increased breathing rate and depth, Feedback- Decreased carbon dioxide as more is breathed out

Question 6

Increased H+ and bicarbonate ions and decreased pH feedback loop

Answer 6

Stimulus- Increased H+ and bicarbonate ions and decreased pH, Receptor- Aortic and carotid chemoreceptors, Modulator- Medulla, Medulla serves a nerve impulse via the phrenic and intercostal nerves to the effector, Effector- Diaphragm and intercostal muscles, Diaphragm and intercostal muscles contract causing the response, Response- Increased breathing rate and depth, Feedback- decreased H+ ions and bicarbonate ions and increased pH as the reaction reverses into CO2 to be breathed out

Question 7

Decreased oxygen feedback loop

Answer 7

Stimulus- Decreased oxygen levels, Receptor- Medulla chemoreceptors and aortic and carotid chemoreceptors, Modulator- Medulla, Medulla serves a nerve impulse via the phrenic and intercostal nerves to the effector, Effector- Diaphragm and intercostal muscles, Diaphragm and intercostal muscles contract causing the response, Response- Increased breathing rate and depth, Feedback- More oxygen produced

Question 8

Stretch receptors

Answer 8

Neurons located in the lungs that are stimulated by the stretching (inflation) of lungs, Initiate an impulse to the medulla when the lungs are inflated to inhibit inspiration and allows expiration to occur preventing the over-inflation of lungs

Question 9

Conscious control over breathing

Answer 9

Motor tract in the cerebral cortex of the brain controls voluntary breathing which can be overridden by the respiratory centre in the medulla if a stimuli demands it

Question 10

Diving

Answer 10

Holding your breath underwater causes oxygen levels to fall (as cells utilise oxygen in cellular respiration) and carbon dioxide levels to rise which triggers an urgent need to breathe causing the diver to start to move to the top of the water to breathe

Question 11

Hyperventilation

Answer 11

Reduces carbon dioxide levels which triggers the urge to breathe meaning although a divers oxygens levels will drop their carbon dioxide levels will not rise fast enough to trigger the urgent need to breathe meaning the diver runs out of oxygen before feeling the need to breathe causing them to pass out