CBSE - X - Biology - Control and Coordination
control and coordination
The Autonomic Nervous system is organized into two parts; the sympathetic and parasympathetic, which bring about opposite effects on the same organ.
Thjis can be understood by the following example: The sympathetic quickens the heartbeat while the parasympathetic slows it. The sympathetic increases the strength of the heart contraction, while parasympathetic decreases the heart contraction. The sympathetic constricts the blood vessels, while the parasympathetic dilates it.
The normal average heart beat in a resting person is 70-80 beats per minute, During sleep it goes down to 50-60 beats per minute, and it accelerates to above 100 with emotional excitement.
Increased heart rate is produced by increased sympathetic activity and decreased parasympathetic activity.
During sleep the parasympathetic is in control and the sympathetic is suppressed so the heart rate becomes low. During fear the sympathetic takes command and the parasympathetic is suppressed so the heart rate will be faster.
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