Diagram Of Neuron: Detailed Explanations, Structure & Function

What Is a Neuron?

Neurons are the basic building blocks of the brain and nervous system and serve to receive sensory input, send motor commands to the muscles, and modify and transmit electrical signals throughout the body. Each neuron is specialised to perform transmission of information to other nerve cells, muscle, or gland cells. They conduct all the activities taking place in the nervous system: reflex actions, perceiving, thinking, memorising, and the performance of voluntary movements as well as involuntary movements.

Neurons communicate with each other through synapses by changing electrical impulses into a chemical form to ensure efficient and correct transmission of the signal. The structure and functions of neurons are very important in understanding the activities going on in the brain and in treating neurological disorders.

Labelled Neuron Diagram

Given below is the simple neuron diagram with its parts:

Structure of a Neuron

The neuron structure contains several primary parts that make the cell functional. These parts include:

Cell Body (Soma)

• Contains a nucleus and organelles.

• Processes information and maintains cell health.

Dendrites

• Branch-like structures which receive signals from other neurons.

• Increase surface area for signal reception.

Axon

• Long, slender projection which transmits signals away from the cell body.

• Axons come in different lengths depending on the type of neuron.

Axon Terminals

• These are the endings of the axon that connect to other neurons or muscle cells.

• Release neurotransmitters to communicate with other cells.

Myelin Sheath

• It is the insulating membrane around axons.

• It increases the speed of nerve impulse transmission.

Nodes of Ranvier

• Gaps in the myelin sheath

• Saltatory conduction quickly transmits the signal.

Types of Neurons

Neurons are classified based on the structure and functionality of the neuron. They are classified into:

Sensory Neurons

• It carries sensory information from receptors to the central nervous system.

• Example: Neuron in the skin which detects touch.

Motor Neurons

• Carry commands from the central nervous system to muscles.

• Example: Neuron which causes muscle contraction

Interneurons

• Connect sensory and motor neurons within the central nervous system.

• Example: Neurons in the spinal cord that relay signals between sensory and motor neurons.

How Neurons Work – Signal Transmission

Neurons transmit signals through action potentials and chemical communication at synapses.

Action Potential

• An action potential is an electrical impulse generated by changes in membrane ion permeability.

Synapse Structure

• The synapse consists of the presynaptic terminal, which releases neurotransmitters.

• The synaptic cleft, which acts as the gap between neurons.

• The postsynaptic membrane, which receives and responds to the chemical signal.

Neurotransmitters

• Dopamine: Helps regulate reward, movement, and mood.

• Serotonin: Influences emotions, sleep cycles, and overall well-being.

• Acetylcholine: Enables muscle contraction and is essential for learning and memory.

Neuron-Related Disorders

Several neurological diseases are claimed to be connected to the failure of neurons.

Alzheimer’s Disease

A condition characterised by the death of neurons, and the consequences are memory loss and cognitive declines

Parkinson’s Disease

Involves the loss of dopamine-producing neurons, affecting movement and coordination.

Multiple Sclerosis

An autoimmune disorder that attacks the myelin sheath, disrupting neural communication.

Neurons NEET MCQs (With Answers & Explanations)

Important questions asked in NEET from this topic are:

• Structure of neurons

• Types of neurons

• Disorders related to neurons

Practice Questions for NEET

Q1. The major constituents of neurofilaments are

1. Microtubules

2. Intermediate filaments

3. Actin filaments

4. Protofilaments

Correct answer: 2) Intermediate filaments

Explanation:

The main structural element in the neurons of the brain is neurofilament. They are fibrous proteins having a diameter of 10 nm. The proteins involved as structural elements in the neurons are divided into six types based on protein structure and gene organization. Neurofilaments are classed as Type IV intermediate filaments which are found in the cytoplasm of neurons. Neurofilaments majorly consist of intermediate filaments. They provide the structural support for axons as well as regulate the diameter of the axons. These intermediate filaments are also found in cyton and dendrites and transmit nerve impulses.

Hence, the correct answer is option (2) intermediate filament.

Q2. Myelinated nerve fibres are found in

1. Spinal nerves

2. Cranial nerves

3. Autonomic nervous system

4. Both a and b

Correct answer: 4) Both a and b

Explanation:

There are two types of axons, namely, myelinated and unmyelinated. The myelinated nerve fibers are enveloped with Schwann cells, which form a myelin sheath around the axon. The gaps between two adjacent myelin sheaths are called nodes of Ranvier. Myelinated nerve fibers are found in spinal and cranial nerves. Unmyelinated nerve fiber is enclosed by a Schwann cell that does not form a myelin sheath around the axon and is commonly found in autonomous and somatic neural systems.

Hence, the correct answer is option 4) Both a and b.

Q3. Nerve fibers are surrounded by an insulating fatty layer called

1. Adipose tissue

2. Myelin sheath

3. Hyaline sheath

4. Peritoneum

Correct answer: 2) Myelin Sheath

Explanation:

The myelin sheath is an insulating fatty coating that envelops nerve fibers. By enabling electrical impulses to leap between the Nodes of Ranvier, which are openings in the myelin sheath, the sheath speeds up the transmission of nerve signals. Saltatory conduction is the mechanism that speeds up and improves neuron transmission.

Hence, the correct answer is option 2) Myelin sheath.

Also Read:

• MCQs on Structure of Neuron

• Mechanism of Vision

• Peripheral Nervous System

Recommended Video on ‘Diagram of Neuron’