What is the primary difference between a neuron and a nerve?

A neuron is the fundamental structural and functional unit of the neural system – it's a single nerve cell specialized for transmitting electrical and chemical signals. It has a cell body, dendrites, and an axon. A nerve, on the other hand, is a bundle of many axons (nerve fibers) belonging to multiple neurons, typically wrapped together by connective tissue, much like a cable containing many individual wires. Nerves serve as pathways for transmitting signals between the central nervous system and other parts of the body, while neurons are the individual signal generators and conductors.

How is the resting membrane potential maintained in a neuron?

The resting membrane potential (RMP) is maintained primarily by the differential distribution of ions across the neuron's membrane. The key players are the sodium-potassium pump, which actively transports three $ ext{Na}^+$ ions out for every two $ ext{K}^+$ ions pumped in, and the membrane's differential permeability. The membrane is significantly more permeable to $ ext{K}^+$ ions (due to more leak channels) than to $ ext{Na}^+$ ions, allowing $ ext{K}^+$ to leak out. Additionally, large, negatively charged proteins and organic phosphates trapped inside the cell contribute to the overall negative charge inside relative to the outside, establishing the RMP of about $-70, ext{mV}$.

What is the 'all-or-none' principle in nerve impulse conduction?

The 'all-or-none' principle states that if a stimulus reaches the threshold intensity, an action potential will fire with its full, characteristic amplitude, regardless of the stimulus strength. If the stimulus is below the threshold, no action potential will be generated. It's like flipping a light switch: it's either fully on or fully off; there's no 'half-on' state. The strength of the stimulus is encoded not by the amplitude of the action potential, but by the frequency at which action potentials are generated.

Explain the role of the myelin sheath in nerve impulse transmission.

The myelin sheath is a fatty layer that insulates the axon of many neurons. It's formed by Schwann cells in the PNS and oligodendrocytes in the CNS. Its primary role is to increase the speed of nerve impulse conduction. Instead of the impulse propagating continuously along the entire axon, in myelinated axons, the impulse 'jumps' from one Node of Ranvier (gaps in the myelin sheath) to the next. This process, called saltatory conduction, is significantly faster and more energy-efficient than continuous conduction in unmyelinated axons, allowing for rapid communication over long distances.

What are neurotransmitters and how do they function at a synapse?

Neurotransmitters are chemical messengers that transmit signals across a chemical synapse from one neuron to another target cell (another neuron, muscle cell, or gland cell). When an action potential arrives at the presynaptic terminal, it triggers the release of these neurotransmitters into the synaptic cleft. They then bind to specific receptors on the postsynaptic membrane, causing ion channels to open or close, which in turn generates either an excitatory postsynaptic potential (EPSP) or an inhibitory postsynaptic potential (IPSP) in the postsynaptic neuron. This binding initiates or inhibits a new electrical signal in the target cell.

Distinguish between the sympathetic and parasympathetic nervous systems.

The sympathetic and parasympathetic nervous systems are two divisions of the autonomic nervous system, often having opposing effects to maintain homeostasis. The sympathetic system is responsible for the 'fight or flight' response, preparing the body for stressful situations by increasing heart rate, dilating pupils, inhibiting digestion, and diverting blood to muscles. Conversely, the parasympathetic system promotes 'rest and digest' activities, conserving energy by decreasing heart rate, constricting pupils, stimulating digestion, and promoting relaxation. They work in a balanced manner to regulate involuntary bodily functions.

← ALL TOPICS

Biology

NEXT TOPIC →

Generation and Conduction of Nerve Impulse

Neural System

Biology

NEET UG

Version 1Updated 22 Mar 2026

Explore This Topic

Definition Deep Explanation Core Principles NEET Importance Problem Strategy Practice Problems MCQ Practice Quick Revision

The neural system, often referred to as the nervous system, is an intricate network of specialized cells called neurons and supporting glial cells, responsible for transmitting signals between different parts of the body. It forms the body's primary communication and control system, enabling organisms to perceive, interpret, and respond to both internal and external stimuli. This highly organized …

Quick Summary

The neural system is the body's intricate communication network, composed of specialized cells called neurons and supporting glial cells. Its primary function is to receive, process, and transmit information, enabling perception, thought, and coordinated responses.

It's broadly divided into the Central Neural System (CNS), comprising the brain and spinal cord, which acts as the command center, and the Peripheral Neural System (PNS), a vast network of nerves extending throughout the body.

The PNS further includes the Somatic Neural System for voluntary movements and the Autonomic Neural System for involuntary functions. The Autonomic System has two branches: Sympathetic (fight or flight) and Parasympathetic (rest and digest).

Nerve impulses are electrochemical signals (action potentials) generated by ion movement across the neuron membrane, propagated along axons, and transmitted across synapses via neurotransmitters. This complex system ensures rapid communication and integrated control over all bodily functions.

Vyyuha

Your 6-Month Blueprint, Updated Nightly

AI analyses your progress every night. Wake up to a smarter plan. Every. Single.…

Key Concepts

Resting Membrane Potential (RMP) Maintenance

The RMP is the baseline electrical state of a neuron, crucial for its excitability. It's established by three…

Phases of Action Potential

An action potential is a rapid, transient reversal of the membrane potential. It occurs in distinct phases:…

Chemical Synaptic Transmission

Chemical synapses are the most common type of junction for neuronal communication. The process involves…

Neuron: — Functional unit. Cell body, dendrites (receive), axon (transmit).

Glial Cells: — Support neurons (myelin, nutrients).

Resting Potential (RMP): —

\approx -70,\text{mV}

. Maintained by

\text{Na}^+/\text{K}^+

pump (

3,\text{Na}^+

out,

2,\text{K}^+

in) and

\text{K}^+

leak channels.

Action Potential: — All-or-none.

- Depolarization: $\text{Na}^+$ influx (voltage-gated $\text{Na}^+$ channels open). - Repolarization: $\text{K}^+$ efflux (voltage-gated $\text{K}^+$ channels open, $\text{Na}^+$ channels inactivate). - Hyperpolarization: Brief undershoot (slow $\text{K}^+$ channel closure).

Conduction: — Saltatory (myelinated, faster) vs. Continuous (unmyelinated).

Synapse: — Junction for signal transfer.

- Chemical: Neurotransmitters, synaptic cleft, $\text{Ca}^{2+}$ influx triggers release. - Electrical: Gap junctions, direct ion flow, faster.

Neurotransmitters: — Chemical messengers (e.g., Acetylcholine, GABA, Norepinephrine).

CNS: — Brain + Spinal Cord (processing).

PNS: — Nerves outside CNS (relay).

- Somatic: Voluntary (skeletal muscle). - Autonomic: Involuntary (viscera). - Sympathetic: Fight/Flight ( $\uparrow$ HR, dilate pupils, $\downarrow$ digestion). - Parasympathetic: Rest/Digest ( $\downarrow$ HR, constrict pupils, $\uparrow$ digestion).

Reflex Arc: — Receptor

\rightarrow

Afferent

\rightarrow

Interneuron

\rightarrow

Efferent

\rightarrow

Effector.

To remember the sequence of action potential phases: Don't Really Hate Resting. Depolarization (Na+ in) Repolarization (K+ out) Hyperpolarization (K+ slow close) Resting state (Na+/K+ pump)

← ALL TOPICS

Biology

NEXT TOPIC →

Generation and Conduction of Nerve Impulse