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The Human Body: Nervous System - The Spinal Cord

Grade 5ICSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The Spinal Cord is a thick, cylindrical bundle of nerves that extends from the lower part of the brain, the Medulla OblongataMedulla \ Oblongata, down through the hollow center of the backbone.

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It is protected by the bony vertebral column (backbone), which consists of 3333 individual bones called vertebrae.

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The primary function of the spinal cord is to act as a 'highway' for messages traveling between the brain and the rest of the body.

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It is responsible for Reflex ActionsReflex \ Actions, which are automatic and instantaneous responses to a stimulus that do not involve the conscious part of the brain.

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The spinal cord contains 3131 pairs of spinal nerves that branch out to different parts of the body.

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The Reflex ArcReflex \ Arc is the specific pathway followed by a nerve impulse during a reflex action: Stimulus→Receptor→Sensory Neuron→Spinal Cord→Motor Neuron→EffectorStimulus \rightarrow Receptor \rightarrow Sensory \ Neuron \rightarrow Spinal \ Cord \rightarrow Motor \ Neuron \rightarrow Effector.

📐Formulae

Reflex Arc:Stimulus→Sensory Nerve→Spinal Cord→Motor Nerve→Muscle ResponseReflex \ Arc: Stimulus \rightarrow Sensory \ Nerve \rightarrow Spinal \ Cord \rightarrow Motor \ Nerve \rightarrow Muscle \ Response

Total Spinal Nerve Pairs=31Total \ Spinal \ Nerve \ Pairs = 31

Total Vertebrae in Backbone=33Total \ Vertebrae \ in \ Backbone = 33

💡Examples

Problem 1:

What happens when you accidentally touch a very hot plate?

Solution:

A reflex action occurs.

Explanation:

When the hand touches a hot plate (StimulusStimulus), the heat is detected by the skin (ReceptorReceptor). A signal travels via the sensory nerve to the Spinal CordSpinal \ Cord. The spinal cord immediately sends a command back via the motor nerve to the arm muscles (EffectorEffector), causing the hand to pull away before the brain even feels the pain.

Problem 2:

Calculate the total number of nerves originating directly from the spinal cord.

Solution:

31×2=6231 \times 2 = 62 individual nerves.

Explanation:

The spinal cord has 3131 pairs of spinal nerves. Since a pair consists of 22 nerves, the total count is 31×2=6231 \times 2 = 62 nerves.

Problem 3:

Why is the spinal cord compared to a 'telephone cable'?

Solution:

Because it transmits signals.

Explanation:

Just as a telephone cable carries electrical signals between two distant points, the spinal cord carries nerve impulses between the brain and the various organs and muscles of the body.