Process of Neural Communication – Class 11 Biology Notes

Process of Neural Communication

Neural communication is the mechanism. By this mechanism the nervous system transmits information from one part of the body to another part. It lets the organisms sense stimuli, process information and also to respond appropriately. This process is responsible for sensations, thoughts, emotions, learning, memory and also voluntary as well as involuntary actions. Neural communication involves both electrical signals within neurons and also the chemical signals between neurons. This makes it very fast, precise and also well-coordinated.

Neuron: Structural and Functional Unit of Nervous System

A neuron is a specialized cell. It is designed to transmit nerve impulses. Each neuron is structured uniquely for receiving, integrating and passing on information.

Main parts of a neuron:

Dendrites: it receive signals from other neurons
Cell body (Cyton): it contains nucleus and integrates signals
Axon: it transmits impulses away from the cell body

Neurons are supported by neuroglial cells. This gives nourishment, protection and also insulation.

Resting Membrane Potential

When a neuron is not conducting an impulse then it tends to remain in a resting state known as the resting membrane potential. During this state the inside of the neuron is negatively charged relative to the outside. It is about –70 mV. This electrical difference is present as there is unequal distribution of ions across the membrane.

Key reasons for resting potential:

Higher concentration of Na⁺ outside the neuron
Higher concentration of K⁺ inside the neuron
Selective permeability of the membrane
Action of sodium–potassium pump

Generation of Action Potential

Neural communication begins when a stimulus of sufficient strength is applied to the neuron. If the stimulus reaches the threshold level then an action potential is generated. This is a rapid change in membrane potential.

Steps involved:

Opening of voltage-gated Na⁺ channels
Influx of Na⁺ ions
Depolarization of membrane
The inside of the neuron temporarily becomes positively charged.

Repolarization and Hyperpolarization

After depolarization Na⁺ channels close and K⁺ channels open. Potassium ions move out of the neuron and it restores the negative charge inside the cell.

Repolarization: It return to negative potential value as potassium ions move out of the cell
Hyperpolarization: Excess loss of K⁺ makes membrane potential more negative
Restoration: The sodium–potassium pump restores the normal resting potential

Propagation of Nerve Impulse

The action potential travels along the axon as a nerve impulse. This movement is because of successive depolarization and repolarization of adjacent membrane regions.

In myelinated neurons the impulse jumps from one node of Ranvier to another. This process is called saltatory conduction. This increases the speed of transmission and conserves energy.

All-or-None Principle

Neural communication follows the all-or-none law. According to this principle:

A neuron fires completely if threshold is reached
No impulse is generated if stimulus is below threshold
The intensity of a stimulus is represented by the frequency of impulses and not by their strength.

Synapse: Junction of Neural Communication

A synapse is the functional junction between two neurons or between a neuron and an effector organ.

Types of synapses:

Electrical synapse: it allows the direct flow of ions between adjacent cells
Chemical synapse: it transmits the signal through the release of neurotransmitters

Chemical synapses are more common in the nervous system.

Chemical Transmission at Synapse

The axon terminal of the presynaptic neuron and the postsynaptic neuron are separated by a small space at a chemical synapse. The synaptic cleft is the name that is given to the small opening. Neurotransmitters are released when an action potential reaches the axon terminal.

Steps of synaptic transmission:

Arrival of nerve impulse at axon terminal
Release of neurotransmitter into the synaptic cleft
Binding of neurotransmitter to specific receptors on the postsynaptic membrane
Generation of response in the postsynaptic neuron

Neurotransmitters

Neurotransmitters are chemical messengers. It transmits signals across synapses.

Examples:

Acetylcholine – it is involved in muscle contraction and memory
Dopamine – it regulates movement and reward
Serotonin – controls mood regulation
GABA – it acts as an inhibitory neurotransmitter

Excitatory and Inhibitory Synapses

Neurotransmitters may either stimulate or it may inhibit the postsynaptic neuron.

Excitatory synapse: Increases chances of action potential
Inhibitory synapse: Decreases chances of action potential

The final response completely depends on the balance between excitatory and inhibitory signals.

Termination of Neural Signal

Neural signals must stop at the right time in order to prevent continuous stimulation.

Methods of termination:

Enzymatic breakdown: neurotransmitters are broken down by enzymes in the synaptic cleft
Reuptake: neurotransmitters are reabsorbed into the presynaptic neuron
Diffusion: neurotransmitters diffuse away from the synaptic cleft

Integration of Neural Signals

Integration of Neural Signals refers to the process through which a neuron receives impulses from multiple neurons. Later it combines them at the axon hillock. These incoming signals may arrive repeatedly over time. This is known as temporal summation or simultaneously from different neurons called spatial summation. An action potential is generated only when the combined effect of these signals reaches the threshold level.

Neural Communication at Neuromuscular Junction

At the neuromuscular junction neural signals are transmitted from motor neurons to muscle fibers. Acetylcholine is released and this leads to muscle contraction. This process converts electrical signals into mechanical action.

Importance of Neural Communication

Neural communication is essential for survival and normal functioning.

Major roles:

Sensory perception: it helps in receiving and interpreting sensory information
Muscle movement: it enables coordination and control of voluntary and involuntary movements
Learning and memory: it plays a key role in storing and processing information
Emotional responses: it regulates emotions and behavioral responses
Regulation of body functions: it maintains a vital functions such as heartbeat, breathing and digestion

Disorders Related to Neural Communication

Any disruption in neural communication can cause disorders like Parkinson's disease, Alzheimer's disease, epilepsy, depression and anxiety. Many drugs act by modifying neurotransmitter activity.

Neural vs Hormonal Communication

Comparison of Neural Communication and Hormonal Communication
Neural Communication	Hormonal Communication
Very fast in action	Slow in action
Highly specific	Widespread in effect
Effects are short lasting	Effects are long lasting
Uses nerve impulses	Uses hormones
Transmitted through neurons	Transported through blood

Summary

The process of neural communication involves the transmission of electrical impulses with the neurons and chemical transmission across synapses by the use of neurotransmitters. It begins with the resting membrane potential. Then it is followed by action potential generation, propagation of nerve impulse and synaptic transmission. This highly organized system allows rapid coordination of body activities, response to stimuli and maintenance of internal balance. Neural communication forms the foundation of sensation, movement, cognition and behavior in living organisms.