Question

Structural and functional unit of nervous system is
A. Nephron
B. Cyton
C. Neuron
D. Axon

Answer 1

Hint: The units that make up the structure of an organ and also perform its functions are the structural and functional units. Without them the organs won’t exist. Different organs have their own unique unit that builds them.

Complete answer:
Human body is full of different cells that make tissues which further make organs specialised to perform different functions of our body. Nervous system is the centre of control and coordination of our body. It is the one which is responsible for voluntary and involuntary functions of our body. It is divided into Central and Peripheral nervous systems. Central nervous system is the centre for control and information processing and it comprises the brain and spinal cord. Peripheral nervous system consists of all the nerves that arise from the brain and spinal cord. Nervous system is made up of unique cells called neurons which are highly specialised to receive, detect and transmit signals or stimuli.

Neuron is made up of three parts: the cell body, dendrites and axon.
Cell body, also known as cyton is made up of cell organelles, is rich in cytoplasm and granules known as Nissl’s granules. It receives signals from the nearby neurons with the help of dendrites. Along with that it also takes care of the growth and maintenance of the neuron. Dendrites are short fibres branching out of the cell body and also contain Nissl’s granules. They receive the nerve impulses and transmit them to the cell body. Axon is the longest part of the neuron and is like a fibre with a branched distal end. Each branch on the distal end is in the shape of a bulb and is known as a synaptic knob and consists of neurotransmitters in its synaptic vesicles. They function in sending the nerve impulse away from the cell body to a neuro-muscular junction.

Function of neurons include – Functions are divided into motor and sensory.
-Motor functions include the transmission of impulse from the central nervous system to other parts of the body.
-Sensory functions involve the reception of signals from other parts of the body and sending them to the central nervous system.
Nephron on the other hand is the structural and functional unit of the kidney which filters blood and maintains the concentration of salts and other substances needed in the body.

Hence, the correct answer is option (C).

Additional information:
-Neurons are divided into unipolar (one axon, no dendrites), bipolar (one axon and one dendrite) and multipolar (one axon and more than 2 dendrites) based on the number of dendrites and axons.
-Unipolar neurons are found in the embryonic stages, bipolar neurons are in the retina and the multipolar are found in the cerebral cortex of the central nervous system.
-Axons can have an envelope of Schwann cells that forms a myelin sheath around them and such axons are known as myelinated axons. These axons are found in the nerves of the spinal cord and cranium.
-Axons enveloped with Schwann cells that do not form a myelin sheath are unmyelinated axons and are found in the somatic and autonomic nervous system.

Note: Neurons are such cells which don’t undergo cell division throughout the life of an organism. Human beings have around 100 billion neurons at the time of their birth and they are not replaced even if they die.