How do parasympathetic neural signals affect the working of the heart?
Correct answer: A. Reduce both heart rate and cardiac output
- A. Reduce both heart rate and cardiac output
- B. Heart rate is increased without affecting the cardiac output
- C. Both heart rate and cardiac output increase
- D. Heart rate decreases but cardiac output increases
Explanation
Parasympathetic neural signals, mediated by the vagus nerve (cranial nerve X), exert an inhibitory influence on the heart. During parasympathetic stimulation, the heart rate decreases (bradycardia) as the sinoatrial (SA) node's firing rate is reduced. This leads to fewer contractions per minute and consequently lowers cardiac output, which is determined by heart rate and stroke volume. Therefore, the correct answer is that both heart rate and cardiac output are reduced. The other options are incorrect as they do not accurately describe the effects of parasympathetic stimulation on the heart.
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Coordination depends on receptors, neurons, synapses and nerve impulses, with reflex actions traced through the reflex arc and the roles of major brain regions. Chemical coordination covers endocrine glands and hormones, including how hormones regulate growth, metabolism, reproduction and internal balance, unlike rapid nervous control.
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