Reflex actions are automatic, involuntary responses to stimuli, like pulling your hand away from a hot stove. A reflex arc is the pathway of nerve impulses involved in a reflex action.
Examples of Reflex Actions:
1. Withdrawal Reflex:
Touching a hot object causes an immediate pull-back of the hand, without conscious thought.
2. Knee-Jerk Reflex:
Tapping below the kneecap causes the leg to kick out, a simple example of a reflex arc.
Explanation of a Reflex Arc:
A reflex arc is the neural pathway that transmits the signals for a reflex action. It typically involves these components:
Stimulus: A change in the environment that triggers the reflex (e.g., heat, touch).
Receptor: A sensory organ that detects the stimulus (e.g., skin receptors for heat).
Sensory Neuron: A nerve that carries the impulse from the receptor to the spinal cord.
Integration Center: Usually the spinal cord, where the sensory neuron connects to a motor neuron.
Motor Neuron: A nerve that carries the signal from the spinal cord to the effector (the muscle or gland that responds).
Effector: The muscle or gland that produces the reflex action (e.g., muscle contraction in the withdrawal reflex).