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Biology - The Nervous System

Grade 10ICSE

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

🔑Concepts

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The Neuron: The structural and functional unit of the nervous system, consisting of the cyton (cell body), dendrites (receive impulses), and axon (conducts impulses away).

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Synapse: The junction between the axon terminal of one neuron and the dendrites of the next, where signals are transmitted via neurotransmitters like Acetylcholine (C7H16NO2+C_7H_{16}NO_2^{+}).

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Nerve Impulse: An electrochemical charge that travels along a neuron. It involves the movement of Sodium ions (Na+Na^{+}) and Potassium ions (K+K^{+}) across the axon membrane.

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Central Nervous System (CNS): Comprises the Brain (Cerebrum for memory/intelligence, Cerebellum for balance, Medulla Oblongata for involuntary actions) and the Spinal Cord.

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Reflex Action: An immediate, involuntary response to a stimulus. The pathway followed is the Reflex Arc: Stimulus→Receptor→Sensory Neuron→Spinal Cord→Motor Neuron→Effector→ResponseStimulus \rightarrow Receptor \rightarrow Sensory\ Neuron \rightarrow Spinal\ Cord \rightarrow Motor\ Neuron \rightarrow Effector \rightarrow Response.

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Peripheral Nervous System (PNS): Divided into Somatic (voluntary) and Autonomic (involuntary) systems. The Autonomic system is further split into Sympathetic (stress/fight-or-flight) and Parasympathetic (rest/digest).

📐Formulae

Vresting≈−70 mVV_{resting} \approx -70\text{ mV}

Vaction≈+30 to +40 mVV_{action} \approx +30\text{ to } +40\text{ mV}

Speed of Impulse≈100 m/s (in myelinated fibers)\text{Speed of Impulse} \approx 100\text{ m/s (in myelinated fibers)}

💡Examples

Problem 1:

Explain the movement of ions during the 'Depolarization' phase of a nerve impulse.

Solution:

During depolarization, the membrane becomes highly permeable to Na+Na^{+} ions. Na+Na^{+} channels open, and Na+Na^{+} rushes into the axon.

Explanation:

This influx of positive charge changes the membrane potential from the resting state of −70 mV-70\text{ mV} to a positive state of approximately +30 mV+30\text{ mV}.

Problem 2:

Differentiate between the functions of the Cerebrum and the Cerebellum.

Solution:

Cerebrum = Seat of intelligence and conscious will; Cerebellum = Maintenance of posture and equilibrium.

Explanation:

The Cerebrum controls voluntary actions and interprets sensations, while the Cerebellum coordinates muscular activity for balance, especially during walking or cycling.

The Nervous System - Revision Notes & Key Formulas | ICSE Class 10 Science