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Communication and homeostasis

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Question 40

A physiological study investigated the autonomic regulation of cardiac function in a miniature pig model. Under basal resting conditions, the mean heart rate was recorded as 85 bpm85\text{ bpm}85 bpm. The researchers then performed the following experimental interventions:

  • Following bilateral vagotomy (severing the parasympathetic vagus nerves), the resting heart rate increased to 135 bpm135\text{ bpm}135 bpm.
  • Following surgical cardiac sympathectomy (severing the sympathetic nerves), the resting heart rate decreased to 75 bpm75\text{ bpm}75 bpm.
a.

Suggest two conclusions about the autonomic control of resting heart rate in this model that can be drawn from these data. Support your conclusions with quantitative evidence.

[4]
b.

Identify:

  1. The specialised region of cardiac muscle tissue in the right atrium that acts as the primary pacemaker where these autonomic pathways synapse.
  2. The neurotransmitter released by postganglionic parasympathetic neurones at this location.
[2]

Communication and homeostasis Questions

  1. A Level
  2. /Biology
  3. /Communication and homeostasis