Biologically speaking, the nervous system is a highly complex network of specialised cells known as neurons. The nervous system is a vital part of an animal as it coordinates and regulates the action and sensory information by the transmission of signals, through special chemicals known as neurotransmitters, to and from the different parts of the body. Thus neural communication is a process of transfer of information between specialised cells along with a network for carrying out the most basic to the most complex function in the day-to-day life of an animal. A nervous system is the given highly specialised and complex network for neural communication and transmission from the brain or spinal cord to different parts of the body. It serves as the principal system for the regulation of homeostasis and survival in animals.
Along with the endocrine system, it jointly coordinates and integrates all the activities of the organs, regulates the physiological processes for proper and synchronised functioning of the animal body. The nervous system provides an organised network of point-to-point connections between the neurons for neural transmission and neural communication. Specific chemicals known as neurotransmitters are responsible for the conduction of the information between the neurons.
Human Nervous System
The human nervous system is complex, like any other vertebrate, and it can be broadly divided into two essential categories: Central nervous system (CNS) and Peripheral nervous system (PNS).
As the name suggests, it is the system that actively receives information, processes it and integrates it for the response by the effectors. The main sites of the central nervous system are The Brain and The Spinal Cord. The spinal cord maintains the erect structure and the brain is the main control system of our body.
This system comprises the nerve cells which are associated with the central nervous system. The two nerves of the peripheral nervous system associated with the central nervous system are:
Afferent Nerve Fibres:
They transmit nerve impulse from organs or tissues to CNS.
Efferent Nerve Fibres:
They transmit nerve impulse from the CNS to organs or tissues.
The peripheral nervous system is further divided into two types depending on the organs the neural transmission takes place to. They are:
Somatic Nervous System:
Neural communication from the CNS to skeletal muscles. The somatic nervous system regulates voluntary functions such as closing of eyes.
Autonomic Nervous System:
Neural transmission from the CNS to smooth muscles and other involuntary organs of the body. Autonomic nervous system regulates involuntary functions such as heart rate.
Neurons and Main Parts of a Neuron:
Neurons are the cells that form the network of the nervous system and are its most basic unit. The transmission of the signals is in the form of electrical signals between the neurons. These electrical signals are also called nerve impulses or action potential. The action potential travels from one electrical neuron to another by passing through the space between the two known as the synapse.
The main parts of a neuron are the cell body, dendrite, axon, and myelin sheath. The following diagram shows the structure of the neuron.
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The cell body is composed of the nucleus, cell organelles and Nissi’s granules. It is the point of the integration of the incoming and outgoing signals. Right around the cell body are the short and highly branched fibrous projections known as the dendrites specialised to receive stimuli and signals.
Extending from the cell body is the single long fibre of the axon which is branched at the terminals. Axon carries the nerve impulses away from the cell body to another neuron, muscle or gland. The axons are covered with a series of cells called Schwann cells the plasma membranes of which are made up of myelin. This myelin sheath acts as a protection and an insulating covering on the axon. The action potential from the signals which electrically excite the neurons are passed through the synaptic knob containing synaptic vesicles that release neurotransmitters. The neurotransmitters are chemical messengers that pass the electrical signals from one neuron to another. An example of one of the neurotransmitters in acetylcholine, the gamma-aminobutyric acid (GABA). Thus, the neurotransmitters are the molecules that pass the electrical signals through the synapse. Depending on the type of signal passing through the synapse, it can be divided into two types: the chemical synapse and the electrical synapse.
The process of neural transmission or neural communication is further explained below.
Process of Neural Communication and Neural Transmission
There are thousands of signals that are generated due to external stimuli. The survival of an animal depends on the identification and following response to these stimuli. The signals thus generated are transmitted to the CNS, integrated and transmitted back to the muscle or glands for carrying out a response. The entire process of neural communication can be divided into four steps: the reception of the signal by the sense organs, neural transmission to and fro from a neuron to another neuron or muscles or glands, integration of the information from the signal and the action or response to the generated stimulus.
The conduction of the action potential through the axon happens because of the depolarization of the neural membrane. The transfer of the potassium (K+) and sodium ions (Na+) across the neural membrane leads to changing membrane potential as the usual negative charge inside the membrane gets altered because of a concentration gradient.
The electrical signals then are transmitted to another neuron by the neurotransmitter through a cleft between two neurons known as the synaptic cleft. Depending on the type of signal that passes through the synapses are classified as either electrical synapse or chemical synapse.
The two are explained as follows:
In this case, the electrical activity in the presynaptic neuron is converted into the release of a chemical called a neurotransmitter which then goes and binds to the plasma membrane of the postsynaptic neuron. The neurotransmitter in a chemical synapse initiates a cascade of secondary pathways in the postsynaptic neuron in order to pass the electrical signal. The rate of the flow of the electrical signal in a chemical synapse is slow but it is the best mechanism when the signal is to be passed over a longer route.
In an electrical synapse, the special channels called the gap junctions are present which are capable of passing the electric current by the induction of voltage changes in the postsynaptic neuron from the presynaptic ones. Even though the electrical synapse is best for rapid neural communication, it can only be useful for short-range communication.
It is quite evident from the above article that neural communication is a complex network of neurons. And it is divided into the central nervous system and peripheral nervous system for receiving, transmitting, integration and responding of information via neural transmission because of the neurotransmitters passing through the chemical synapse or electric current passing through the electrical synapse.