Reflect Arc

  1. Search in the internet a video showing an example of a reflex action.

2. Explain the term reflex action.

Reflex action is defined as the automatic or involuntary response to a sensory stimulus which is not under conscious control. Some reflex actions do not need to be learnt, as we inherit them when we are born. These are possible thanks to the reflex arcs, which act on an electrical impulse before the impulses reach the brain.

3. State the structures involved in a reflex arc.

The structures involved in the reflex arc are the sensory neurons, the motor neurones and the relay neurons. When the receptor detects a stimulus, the sensory neuron sends an electrical impulse to the relay neuron which is found in the spinal cord and connect the sensory neuron to the motor neuron. The motor neuron sends electrical impulses to an effector that then produces a response.

4. Explain how the reflex action in your video takes place.

In our video, it was explain how the reflex action takes place if a person accidentally touches a hot object, in this specific case a candle. If a person does this, a pain sensitive receptor cell in this fingertip detects the heat stimulus and triggers off the nerve impulse from here. The impulse travels along a sensory neuron to the spinal cord. The message is processed and the response is generated in the spinal cord itself and then this response travels down through a motor nerve to the muscles of the arm. This receives the response, and the arm muscles of the person contracts (the bicep) and lifting the person’s finger away from the hot object.  


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