Spinal cord and Reflex actions

Subject: Science

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Overview

Spinal cord is the ling cylindrical part of CNS. It is present in neural canal of vertebral column. Spinal cord acts as the main center for reflex actions. Spinal cord acts as a link between spinal nerves and brain. Thus it participates in conscious actions. This note explains the anatomy and functions of the spinal cord.
Spinal cord and Reflex actions

Spinal cord:

It is the long cylindrical part of CNS. It is present in the neural canal of the vertebral column. It is the center of all reflex actions. Grey matter, which has a pinkish-grey color in the living brain, contains the cell bodies, dendrites and axon terminals of neurons, so it is where all synapses are. White matter is made of axons connecting different parts of grey matter to each other. In spinal cord grey matter is inside and white matter is outside. Major functions of spinal cord are:

  1. It acts as the main center for reflex actions.
  2. It acts as a link between spinal nerves and brain. Thus it participates in conscious actions.

Reflex actions:

It is defined as an involuntary action performed by muscles under the direction of the spinal cord in response to the stimulus. The best example of the reflex action is pulling of hand when we touch hot or very cold objects and contraction of the pupil when the light is shown in the eye.

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Reflex arc:

The path which is followed by impulses during the reflex action is called the reflex arc. It consists of an afferent (or sensory) nerve, usually one or more interneurons within the central nervous system, and an efferent (motor, secretory, or secretomotor) nerve.

Things to remember
  • Spinal cord is the long cylindrical part of Central Nervous System.
  • Spinal cord acts as the main center for reflex actions.
  • Spinal cord acts as a link between spinal nerves and brain. Thus it participates in conscious actions.
  • Reflex actions is defined as an involuntary action performed by muscles under the direction of spinal cord in response to the stimulus.
  • It includes every relationship which established among the people.
  • There can be more than one community in a society. Community smaller than society.
  • It is a network of social relationships which cannot see or touched.
  • common interests and common objectives are not necessary for society.
Videos for Spinal cord and Reflex actions
Reflex arc
Spinal Cord - External Anatomy - 3D Anatomy Tutorial
Questions and Answers
The immediate and automated response shown to a stimulus without the involvement of brain is called reflex action. When we touch something very hot, we jerk our hand away. This is an example of reflex action.
The path followed by nerve impulses during the process of reflex action is called reflex arc.

When a pin is suddenly pricked in foot, the stimulus is transferred by the following ways:
i. Receptor: tip of nerve of skin of foot.
ii. Sensory nerve: to carry the message from receptor to spinal cord.
iii. Intermediate nerve: to send the stimulus from top to bottom of the spinal cord.
iv. Motor nerve: to carry the stimulus from spinal cord to muscle.
v. Effector: to receive the stimulus in the muscle. Thus the pin is suddenly pricked in the foot, the stimulus transfers to the spinal cord through the nerves of skin. After that the spinal cord sends message to muscle of leg to withdraw the leg immediately.

Reflex action involves sensory neuron, spinal cord and motor neuron only. So, when we touch something hot, the impulse passes from the hand to spinal cord and back to muscles. As brain is not involved during the action, impulses each the brain and we feel pain after sometime.

A man jumped with fear because of reflex action when his bare foot touched the cold object on the ground. During this, the nerves in the skin transmitted the information to spinal cord through sensory nerve, from when an instruction is sent to the muscle through motor nerve.

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