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24 September 2014
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Nervous system - Reflexes

Reflexes: Involuntary and rapid actions

Control: Your spinal cord usually controls your reflexes

Autonomic reflexes: Body functions such as digestion or blood pressure

Involuntary response

Pulling your hand away from a hot object, blinking because it's very bright or kicking when someone taps the tendon below your kneecap - these are all innate reflex actions. They happen rapidly, you don't control them and the result is always the same.

Reflex arc

Most reflexes don't have to travel up to your brain to be processed, which is why they take place so quickly. A reflex action often involves a very simple nervous pathway called a reflex arc.

A reflex arc starts off with receptors being excited. They then send signals along a sensory neuron to your spinal cord, where the signals are passed on to a motor neuron. As a result, one of your muscles or glands is stimulated.

Knee-jerk reflex

The knee-jerk reflex involves a sudden kicking movement of your lower leg after the tendon just below your kneecap has been tapped. Doctors often trigger this reflex to test the function of your nervous system. If the reaction is exaggerated or absent, it may indicate a damage to the central nervous system.

Autonomic reflexes

Most reflexes go completely unnoticed because they don't involve a visible and sudden movement. Body functions such as digestion or blood pressure, for example, are all regulated by reflexes. These reflexes are known as autonomic reflexes.

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