Say what happens to the heart rate and the cardiac output in each case, and which signal is the…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Say what happens to the heart rate and the cardiac output in each case, and which signal is the cause.
- A student sprints for a bus.
- A student sleeps deeply.
- A student has a great fright, and the adrenal medulla releases hormones.
- Which part of the brain controls the heart through the nerves?
Need a reminder? The key ideaShow
The P wave is the depolarisation of the atria. The QRS complex is the depolarisation of the ventricles, and their contraction starts soon after Q. The T wave is the repolarisation of the ventricles, and its end marks the end of the systole. Sympathetic signals and the hormones of the adrenal medulla raise the heart rate and the output. Parasympathetic signals lower them.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) The rate and the output rise. Sympathetic signals increase the rate and the strength of the contraction.
Step 2. (b) The rate and the output fall. Parasympathetic signals decrease the rate and the speed of conduction.
Step 3. (c) The rate and the output rise. The hormones of the adrenal medulla increase the cardiac output.
Step 4. (d) The cardiac centre in the medulla oblongata, through the autonomic nervous system.
Answer: (a) up, sympathetic; (b) down, parasympathetic; (c) up, hormones; (d) the medulla oblongata.
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