Question
Which of the following causes increase in conduction velocity of impulse through heart ‑
| A. |
Vagal stimulation
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| B. |
Parasympathetic stimulation
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| C. |
Sympathetic stimulation
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| D. |
All of the above
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Show Answer
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Correct Answer � C
Explanation
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|
Ans. is ‘c’ i.e., Sympathetic stimulation
Effects of sympathetic stimulation are :
Heart :- positive chronotropic (1‘ heart rate), ii) Positive inotropic (1‘ contractility), iii) Positive dromotropic (1‘ conduction velocity), iv) Positive bathmotropic (increased automaticity), v) Decreased refractory period in all cardiac cells.
Vasoconstriction :- T total peripheral resistance (due to arteriolar constriction), venous capacitance (due to venoconstriction)
Increased stroke volume, cardiac output and BP.
Effects of parasympathetic stimulation are :‑
- Negative chronotropic (decreased heart rate) : – Vagal stimulation cause decrease in slope (flattening) of prepotential (pacemaker potential) and therefore the time taken to reach the threshold level is increased –> Heart rate is decreased.
- Negative dromotropic (decreased conduction).
- Increased refractory period of all type of cardiac cells.
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