9.2.7 - Heart rate control Flashcards
(6 cards)
Where are baroreceptors found?
Carotid arteries in neck and aorta
How is blood pressure controlled by baroreceptors during exercise?
Blood vessels dilate in response to adrenaline causing blood pressure to fall.
This reduces the stretch on baroreceptors.
Cardiac control centre sends signals along the sympathetic nerve to stimulate heart rate and increase blood pressure by vasoconstriction.
How is blood pH controlled by chemoreceptors?
When the blood has a higher carbon dioxide concentration than normal, the pH is lowered (more acidic).
Chemoreceptors detect this and increase the frequency of impulses to medulla oblongata.
This increases frequency of impulses via the sympathetic nervous system to the SAN – so HR increases.
Increased blood flow means more CO2 is removed from the lungs.
How does adrenaline cause heart rate to increase in fight or flight situations?
sympathetic nerve stimulates the adrenal medulla to release adrenaline.
It binds to receptors on target organs including the SAN.
It increases the frequency of excitation and so increasing heart rate.
More oxygen and glucose are supplied to muscle, allowing for greater ‘fight or flight’.
Explain how the pH of blood plasma affects heart rate.
Low pH detected by chemoreceptors.
Affects cardiac centre.
Sympathetic nerve is stimulated.
Noradrenaline at SAN.
Therefore more waves of excitation which increases heart rate.
Explain why a student’s heart rate increases during a maths test.
Stress causes adrenal glands to release adrenaline into blood stream.
Due to impulses along sympathetic nerve.
Caused by cardiac centre in the brain.
Noradrenaline will be released in SAN.
This increases the waves of depolarisation in the heart which increases heart rate.
