Reflex Action (Leaving Cert Biology): Revision Notes
📚 Revision Notes
Reflex Action
infoNote
Reflex action: an automatic, involuntary, unthinking response to a stimulus e.g. knee jerk, sneezing.
- Most reflex arcs are made up of a sensory neuron, an interneuron and a motor neuron.
- Common reflex action: pulling a hand away from a hot object.
- Reflex arcs allow fast responses to protect the body from damage.
Steps in the Reflex Action
- Receptors in the fingers are stimulated by a hot object.
- An impulse is carried to the spinal cord by a sensory neuron.
- An interneuron carries the impulse across the spinal cord to a motor neuron. (At the same time, another neuron sends the message to the brain.)
- Motor neurons carries the impulse straight out of the spine to the effector, causing the hand to pull back from the heat source.
- As the hand withdraws, the impulse reaches the brain, making the person aware of what happened.
