control of heart rate

Question 1

sympathetic pathway

Answer 1

accelerator nerve
releases noradrenaline
increases heart rate

Question 2

parasympathetic pathway

Answer 2

vagus nerve
releases acetylcholine
decreases heart rate

Question 3

what are chemorecpetors and where are they found

Answer 3

receptors sensitive to changes in pH and co2 conc
found in the carotid body and aortic arch

Question 4

what are baroreceptors and where are they found

Answer 4

receptors sensitive to changes in blood pressure
found in the carotid body and aortic arch

Question 5

where are impulses sent along (by baroreceptors and chemoreceptors)

Answer 5

the medulla

Question 6

heartbeat

Answer 6

• sino-atrial node sends impulses across atria, causing muscles to contract
• non-conducting tissue between atria and ventricles prevents them from contracting at same time
• impulse delayed at the AVN, which allows atria to fully empty of blood before ventricles contract
• impulse passes down bundle of His
• travels along purkyne fibres from apex
• pushes blood up and out the heart

Question 7

increasing heart rate

Answer 7

• chemoreceptors detect low pH by high co2 OR baroreceptors detect low BP
• more impulses sent to medulla
• more frequent impulses sent along accelerator nerve, releasing noradrenaline to SA node
• SA node increases rate in which they send impulses, increases HR
• increased blood flow removes co2 and pH returns to normal OR increased blood flow increases BP

Question 8

decreasing heart rate

Answer 8

• chemoreceptors detect high pH by low co2 OR baroreceptors detect high BP
• impulses sent along medulla
  -more impulses sent along vagus nerve, releasing acetylcholine to SA node
• SA node decreases rate at which they send impulses, decreases HR
• decreased blood flow increases co2 and pH returns to normal OR decreased blood flow decreases BP