Reflex Action

Reflex Action
Definition
The automatic involuntary responses which occur either due to internal or external stimuli are called Reflex Action.
OR
An immediate response to a specific stimulus without conscious control is called a Reflex Action.
Parts of Reflex Action
Reflex action consists of
i. Receptor: (Skin) receive stimuli.
ii. Sensory Neuron: It carries message from receptor to the Central Nervous System (CNS).
iii. Motor Neuron: It carries message from Central Nervous System (CNS) to the effector.
iv. Effector: (Muscle of gland) which perform action.
Reflex Arc
Definition
The pathway of passage in impulse during a reflex action is called Reflex Arc.
Reflexes may be monosynaptic or polysynaptic.
Monosynaptic
The reflex action in which only one synapse is involved is called Monosynaptic.
Example: Knee Jerk
Polysynaptic
The reflex action in which many synapses are involve due to presence of inter neurons between sensory and motor neurons is called Polysynaptic.
Example: Hand withdrawal on the painful stimuli.
Examples of Reflex Actions

• If our hand touch any hot object, it is quickly withdrawn.
• Secretion of juices from the gland.
• Blinking of eyes.
• Contraction and expansion of lungs.
• If a strong light is flashed across the eye, the eyelids are at once closed or start blinking.

Nerve Impulse
Definition
The electrochemical signals developed by a neuron for communication is called Nerve Impulse.
Method of Development of Nerve Impulse
The neurons develop impulse in the following way.
1. Resting Membrane Potential (RMP)
2. Action Potential
3. Propagation of Impulse
4. Synapse