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Human Body - Nervous System (Brain, Spinal Cord, Neurons)

Grade 7ICSE

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

🔑Concepts

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The Nervous System is the complex network of nerves and cells that carry messages to and from the brain and spinal cord to various parts of the body. It is divided into the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).

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A Neuron is the structural and functional unit of the nervous system. It consists of three main parts: the Cell Body (CytonCyton), Dendrites (short fibers that receive impulses), and the Axon (a long fiber that carries impulses away from the cell body).

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The Brain is the main control center, protected by the skull (CraniumCranium). It has three major parts: the CerebrumCerebrum (seat of intelligence and memory), the CerebellumCerebellum (coordinates muscular activity and balance), and the Medulla OblongataMedulla \ Oblongata (controls involuntary actions like heartbeat and breathing).

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The Spinal Cord is a tube-like structure extending from the Medulla down the vertebral column. It is responsible for conducting impulses to and from the brain and controlling Reflex ActionsReflex \ Actions.

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Nerves are bundles of AxonsAxons enclosed in a tubular sheath. They are categorized into: Sensory Nerves (carry impulses from sense organs to CNS), Motor Nerves (carry impulses from CNS to muscles/glands), and Mixed Nerves (perform both functions).

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A Synapse is the microscopic gap between the axon terminal of one neuron and the dendrites of the next neuron, where chemical signals called neurotransmitters facilitate the transfer of impulses.

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Reflex Action is a sudden, involuntary response to a stimulus. The pathway followed by a nerve impulse during a reflex action is called a Reflex ArcReflex \ Arc.

📐Formulae

Reflex Arc:Receptor→Sensory Neuron→Spinal Cord→Motor Neuron→Effector\text{Reflex Arc}: \text{Receptor} \rightarrow \text{Sensory Neuron} \rightarrow \text{Spinal Cord} \rightarrow \text{Motor Neuron} \rightarrow \text{Effector}

Total Brain Mass≈2% of total body weight\text{Total Brain Mass} \approx 2\% \text{ of total body weight}

Nerve Impulse Speed≈100 to 120 m/s\text{Nerve Impulse Speed} \approx 100 \text{ to } 120 \text{ m/s}

💡Examples

Problem 1:

Identify the part of the brain that would be most active while a person is attempting to balance on a tightrope.

Solution:

CerebellumCerebellum

Explanation:

The CerebellumCerebellum is responsible for maintaining the body's posture, equilibrium, and coordinating voluntary muscular movements.

Problem 2:

What is the direction of a nerve impulse through a single neuron?

Solution:

Dendrite→Cyton→Axon→Axon TerminalDendrite \rightarrow Cyton \rightarrow Axon \rightarrow Axon \ Terminal

Explanation:

Dendrites receive the impulse from the previous neuron or receptor, pass it through the cell body (CytonCyton), and the AxonAxon carries it away toward the next synapse.

Problem 3:

Explain why the Medulla Oblongata is considered the most vital part of the brain.

Solution:

Control of Involuntary Vital FunctionsInvoluntary \ Vital \ Functions

Explanation:

The Medulla OblongataMedulla \ Oblongata controls essential life processes such as breathing, heart rate, and blood pressure. Damage to this area can result in immediate death because these involuntaryinvoluntary systems would fail.