Structure of Nerve Cell

• Human nervous system is made up of 12 billion nerve cells. These cells differ from each other in shape, size, chemical composition and function. Despite these differences, the following three main components are found in all nerve cells. These are Soma, Dendrites, and Axon.

Soma:

• Soma is the main part of nerve cell. It contains nucleus and other structures. The genetic material of a nerve cell is being stored in nucleus which enables reproduction and protein synthesis in a cell. Somais responsible formaintaining life of a nerve cell and keeps it healthy and alive. Ifsoma is damaged then the nerve cell stops functioning. Another function of soma is to receive the nerve impulse through dendrite and transmit it further.

Dendrites:

• Dendrites are branches that originate from soma. These are the receiving ends of a neuron. Its function is to receive neural signals from the nearby nerve cells or directly from the sense organs. Dendrites contain special receptors that gets activated when they receive any electrochemical or biochemical signals.

Axon:

• An elongated structure which is attached to soma is called axon. It receives information from soma and sends it to other nerve cells and muscles. Axon carries information through its entire length. Its length varies from many feet in spinal cord to less than one millimeter in brain. The axon, in the end is divided into many small branches which are called terminal buttons. These buttons send information from one neuron to another neuron, gland or muscles. Usually, a neuron conducts information in one direction only that is from dendrite to soma to axon and lastly to terminal buttons. It means that information is received in a neuron from the dendrite end only.
• The axon is covered in most neurons by a covering called myelin sheath. This sheath is not found through the axon in continuity but is separated by small ridges type spaces. These spaces are called Nodes of Ranvier. Both myelin sheath and nodes of Ranvier help in increasing the speed of information flow.

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Important Points of Human Behavior :- 

1. “Inthis chapter, the relation of human behavior and biology is described.”
2. The cell is the basic unit of human body. Many cells form tissue, many tissue to organ, many organs to organ systems are formed. These organ systems perform specific functions of our body. Nerve cell is the basic and smallest unit of nervous system. It is also called neuron.
3. Nerve cells are of three types on the basis of functions: Sensory, motor and association neurons.
4. Nerve cells perform the function of transmitting information in our body.
5. Nervous system is of two types: Central Nervous System and Peripheral Nervous System.
6. Central Nervous system consists of brain and spinal cord.
7. Peripheral nervous system is divided in two parts somatic nervous system and autonomic nervous system.

Human Behavior Questions and Answers

1. Which part of nerve cell contains nucleus?
A Axon
B. Soma
C. Myelin Sheath
D. Nodes of Ranvier

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2. Which part of nerve cell increases the speed of nerve conduction?
A Myelin Sheath
B. Dendrites
C. Thalamus
D. Pons

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“3. Which part of brain controls activities like eating, drinking, sleeping, temperature regulation and sexual arousal?”
A Pons
B. Cerebellum
C. Hypothalamus
D. Thalamus

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4. How many pairs of cranial nerves are there in human brain?
A. 6
B. 10
C. 12
D. 31

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