Question

Describe the structure of neuron.


@Starboy <(￣︶￣)>​

Answer 1

AnsWer :

Neuron is the structural and functional unit of nervous system.

It is covered by neurilemma and is made of two distinct regions as cyton and cytoplasmic extensions.

Cyton:

• Cyton or cell body is called perikaryon or soma. It has granular cytoplasm with large number of network of neurofibrils, various cell organelles like mitochondria, Golgi complex, RER and centrally placed nucleus. The granules present in cytoplasm are conical, rich in RNA and are involved in protein synthesis. These are called Nissl's granules.

Cytoplasmic extensions:

• Two types of cytoplasmic extensions are found arising from the cyton, namely dendrons or dendrites and axon

a. Dendrites:

• Dendrites thin, small cytoplasmic extensions seen in the periphery of the cyton or cell body of neuron.

• These are many in number and break into numerous fine branches which help to carry impulses towards the cell body and are provided with few of the neurofibrils.

b. Axon:

• Axon is the long cytoplasmic process useful in conduction of impulse away from the cell body.

• It is lined by axonal membrane and encloses cytoplasm called axoplasm.

• The axoplasm is in continuation with the cytoplasm of cyton.

• It contains large number of mitochondria, RER and neurofibrils, but lacks Nissl's granules and golgi complex.

• The axon, throughout the length is wrapped by Schwann cell which forms insulating myelin sheath.

• Neuron with myelin sheath are called myelinated neurons.

• In certain animals , neuron lacks the myelin sheath and thus, have non-myelinated neurons.

• The terminal end of the axon in both myelinated and non-myelinated neurons shows presence of many swollen knob like structures called telodendrons.

• They are filled with neurosecretory (acetylcholine and adrenaline) material which act as neurotransmitter.

Answer 2

$\Large{\underline{\boxed{\mathbb \pink{STRUCTURE \: OF \: NEURON:-}}}}$

$\dashrightarrow$ Neuron is a structural and functional unit of the nervous system.In other words, we can say that " Neurons are highly specialised unit cells of the Nervous tissue".They have the ability to receive stimuli from within or outside the body and to conduct (send) impulses (signals) different parts of the body.The impulse travel from one neuron to other neuron.

$\dashrightarrow$ The cell body of a neurone is like a typical animal cell which contains cytoplasm and a nucleus.A number of thin and long fibres are stretching out from the cell body of a neuron which are called Nerve fibres.

$\dashrightarrow$ Each Neuron has the following three parts :

• Cyton - The cyton or cell body is the part which contains a central nucleus and cytoplasm with characteristic deeply stained particles called Nissl's granules.
• Dendrites - The dendrites are the shorter fibres on body.The dendrites pick up the nerve impulses or messages from the sceptre they passed the impulses to the cell body and then along the axon.Medullary sheath absent in them but they contains Nissl's granules and neurofibrils.
• Axon - The axon is a single, long cylindrical process of uniform diameter.It forms fine branches terminally.Each such twig like branch of axon ends in a swollen structure,called Synaptic knob or bouton. It is covered with a medullary sheath. Nissl's granules are absent in them.

$\dashrightarrow$ Types of Neurons :-

• Sensory neurons - These neurons transmit impulses from the sensory cells or receptors towards the central nervous system.
• Motor neurons - These neurons transmit impulses from the centre nervous system towards the muscle cells.
• Relay neurons - These neurons are present in the central nervous system where they serve as a link between other neurons.