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Neuronal communication

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Question 2

In a physiological study on a small mammal, researchers investigated the autonomic nervous regulation of heart rate. Under baseline (normal) conditions, the animal's resting heart rate was measured to be 130 bpm130\text{ bpm}130 bpm. The following experimental observations were recorded:

  • When the parasympathetic cardiac (vagus) nerve was surgically severed, the resting heart rate increased to 210 bpm210\text{ bpm}210 bpm.
  • When the sympathetic cardiac nerves were surgically severed, the resting heart rate decreased to 110 bpm110\text{ bpm}110 bpm.
a.

Suggest two conclusions about the nervous control of resting heart rate in this mammal that can be drawn from these observations. Use quantitative evidence from the data to support your conclusions.

[4]
b.

Identify:

  1. The specific structure in the heart wall (the pacemaker) where these autonomic nerves terminate to modulate heart rate.
  2. The neurotransmitter released by the postganglionic parasympathetic nerve terminals at this site.
[2]
Markscheme

Neuronal communication Questions

  1. A Level
  2. /Biology
  3. /Neuronal communication

22 exam-style questions on OCR A A Level Biology Neuronal communication. Each one has a worked solution and a mark scheme showing where the marks go.

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