Reflex action

Question 1 What is a reflex action? Give example?

Question 2 Why reflex actions are generally known as spinal reflexes?

Question 3 What are receptors?

Question 4 What are Effectors?

Question 5 What are connectors?

Reflex Action

A reflex action is a spontaneous, automatic and mechanical response to stimulus or sudden action in response to something in the environment.

For Example : Blinking of eyes, movement of diaphragm, withdrawal of hand or foot every time when a needle or hot object is touched, sneezing, hunger etc.

(1) Sensory (receptors)

(a) It occur in sense organs.
(b) It receive stimuli by dendrites.
(c) It transmit impulse towards brain and spinal cord through axons.

(2) Motor (Effectors)

(a) Dendrites of these neurons synapse with axon of sensory nerves.
(b) They transmit impulse from brain and spinal cord to effectors (muscle or glands)

(3) Relaying (connectors)

(a) They occur in brain and spinal cord.
(b) They link sensory and motor neurons for distant transmission of nerve impulse.

In reflex action

Fine tips (dendrites) of receptors ——–> message(electric impulse) ——-> sensory nerve ——-> spinal cord —–> motor nerves——> effectors(muscles or glands)

The path taken by nerve impulses in a reflex action is called reflex arc.

When our hand touches a hot object, the heat is sensed by thermo receptors present in skin of hand. The receptors trigger nerve impulse in sensory neuron. It transmits message to spinal cord, which is then passed to relay neuron which in turn passes it to motor neuron. The motor neuron trasmit instruction to muscle in our arm. The arm muscle contract and pulls our hand away from object.

Reflexes which involve spinal cord are termed as spinal reflex.

Those reflexes which involve brain are called as cerebral reflexes.

For Example : Contraction of pupil of human eye in the presence of bright light.