In this blog, we learn about classification of nerve fibers. Nervous system is very important and intresting topic.
Neuron is structural and functional basic unit of nervous system. It contains Soma(body), dendrites and axon as you can see in image. Axon also known as nerve fiber, here we learn Classification of nerve fiber.
Nerve fibers are classified by six different methods mention as below. The basis of classification is different in each method.
CLASSIFICATION OF NERVE FIBERS
- Depending upon Structure
- Depending upon Diameter & conduction of impulse
1. Depending on Structure
According to structure, nerve fibers are classified into two types.Just look at image, you not need to mug up all things.
- Non-myelinated Nerve Fibers
It is not covered by myelin sheath.
- Myelinated Nerve Fibers
It is covered by myelin sheath
2. Depends on Origin
On the basis of origin, there are two types of nerve fiber.
- Cranial Nerve Fibers
Nerve fibers arising from brain are called cranial nerve fibers.
- Spinal Nerve Fibers
Nerve fibers arising from spinal cord are called spinal nerve fibers.
3. Depending upon Function
As per nerve fiber function, it is classified into two types as below.
- Sensory Nerve Fibers
Sensory impulse from different parts of the body to the central nervous system is carried by sensory nerve fiber. It simply means this nerve fiber send sensation of body to brain. It is also known afferent nerve fibers.
Eg. If you touch hot water, the sensory fiber send the message of this event from your hand to brain.
- Motor Nerve Fibers
This nerve fibers carry motor impulses from central nervous system to different parts of the body. It simply means when brain sends message to body than it passes from motor nerve fibers.
Eg. When brain interprete that hand touches the hot surface. It immediately sends message to hand to withdraw through this motor nerve fibers.
4. Depends on Distribution
According to distribution, nerve fiber classified into 2 types :
- Somatic nerve fibers
Which supply to skeleton muscles of the body.
- Autonomic nerve fibers
Which supply the various internal organs of the body.
5. Depending upon Secretion
- Adrenergic Nerve Fibers
Adrenergic nerve fibers secrete noradrenaline.
- Cholinergic Nerve Fibers
Cholinergic nerve fibers secrete acetylcholine.
6. Depending upon Diameter & Conduction of impulse
Erlanger and Gasser classified the nerve fibers into three types, on the basis of diameter and velocity of conduction of impulses.
l. Type A nerve fibers
ll. Type B nerve fibers
lll. Type C nerve fibers
Type A nerve fibers are sub-divided into four types :
Velocity of impulse
It is most important and interesting point.See chart, velocity of impulse through nerve fiber is directly proportional to the thickness of the fiber.
Thickness of nerve fiber : Type A > Type B > Type C
So, Velocity of nerve fiber : A > B > C
Type C fiber have velocity of impulse is 0.5 to 2 meter per second. While Type A alpha fiber have velocity of impulse is 70 to 120 meter per second.This is really unbelievable, our body can send impulse from toe to brain 60 times per second.
If someone prick your sole within millisecond brain recieves message & inform you.This is really miracle.
Hope you like the article, kindly message or mail me if you have any kind of query.