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 sympathetic and parasympatheti... 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
The part of the brain that regulates the heart rate is the Medulla.
Step 2
The sympathetic and parasympathetic nerves work antagonistically. Explain what this statement means.
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Answer
The sympathetic and parasympathetic nerves cause opposite effects on the heart. The sympathetic nerve speeds up the heart rate, while the parasympathetic nerve slows it down.
Step 3
State the heart rate when only the sympathetic nerve is blocked.
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The heart rate is 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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The increase in heart rate when the parasympathetic nerve is blocked is 32 beats per minute.
Step 5
Explain why the heart continues to contract when both nerves are blocked.
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The heart continues to contract even when both the sympathetic and parasympathetic nerves are blocked because the sinoatrial node (SAN) acts as a pacemaker, generating electrical impulses independently and keeping the heart rhythmic.
Step 6
Use information from the graph to justify this statement.
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From the graph, it can be observed that the heart rate changes more significantly when the parasympathetic nerve is blocked as it raises the heart rate by 18 beats per minute, whereas blocking only 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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The sympathetic nervous system increases breathing rate.
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