9. Sympathetic and parasympathetic nerves regulate heart rate - Scottish Highers Human Biology - Question 9 - 2017
Question 9
9. Sympathetic and parasympathetic nerves regulate heart rate.
(a) Name the part of the brain that regulates the heart rate.
__________________
(b) The sympatheti... show full transcript
Worked Solution & Example Answer:9. Sympathetic and parasympathetic nerves regulate heart rate - Scottish Highers Human Biology - Question 9 - 2017
Step 1
Name the part of the brain that regulates the heart rate.
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Answer
Medulla.
Step 2
The sympathetic and parasympathetic nerves work antagonistically.
Explain what this statement means.
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Answer
They cause opposite effects/work against each other.
The sympathetic speeds up the heart rate and the parasympathetic slows down heart rate.
Step 3
State the heart rate when only the sympathetic nerve is blocked.
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58 beats per minute
Step 4
Calculate the increase in the heart rate which then occurs when the parasympathetic nerve is also blocked.
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32 beats per minute
Step 5
Explain why the heart continues to contract when both nerves are blocked.
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The SAN (sinoatrial node) controls the heart rate/beats/acts as a pacemaker/still sends impulses to the AVN (atrioventricular node) to remain rhythmic.
Step 6
Use information from the graph to justify this statement.
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There is a greater change from the resting rate when the parasympathetic nerve is blocked (compared to when the sympathetic is blocked).
Blockage of the parasympathetic nerve raises heart rate by 18 beats/minute while blockage of the sympathetic nerve lowers it by 14 beats.
Step 7
State one other effect the sympathetic nervous system has on the body.
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It increases breathing rate.
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