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Human Biology (Year 12) - Nervous Transmission

Ben Whitten

What is a reflex?

A reflex is an automatic response to changes in the external and/or internal environment. Some reflexes involve the unconscious part of the brain, however most are coordinated by the spinal cord. A spinal reflex does not involve the brain; the brain may become aware of what is happening, but it does not become aware until after the response has been initiated. Reflexes have four common properties:

  • A stimulus is required to trigger a reflex; it is not spontaneous

  • A reflex is involuntary; it occurs without any conscious thought

  • A reflex response is rapid; only a small number of neurons are involved

  • A reflex is stereotyped; it occurs in the same way each time it happens

What is a reflex arc?

A reflex arc is the pathway which a nerve impulse follows in travelling from a receptor to an effector. The basic elements of a reflex arc includes (in the following order);

  • Receptor

  • Sensory neuron

  • Connector neuron

  • Motor neuron

  • Effector

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