Nerve Fiber – Classification

NERVE FIBER – CLASSIFICATION

Q. 1 Which of the following types of nerve fibres carry fast pain:
 A A alpha
 B A beta
 C A gamma
 D A delta
Q. 1 Which of the following types of nerve fibres carry fast pain:
 A A alpha
 B A beta
 C A gamma
 D A delta
Ans. D

Explanation:

A delta


Q. 2

Activation of which of the following fiber result in first pain which help to localize the site and intensity of the noxious stimulus:

 A

A beta fiber

 B

A delta fiber

 C

B fiber

 D

C fiber

Q. 2

Activation of which of the following fiber result in first pain which help to localize the site and intensity of the noxious stimulus:

 A

A beta fiber

 B

A delta fiber

 C

B fiber

 D

C fiber

Ans. B

Explanation:

Activation of A delta  fiber releases glutamate, and is responsible for first pain (also called fast pain or epicritic pain) which is a rapid response and mediates the discriminative aspect of pain or the ability to localize the site and intensity of the noxious stimulus. Adelta fibers are thinly myelinated, 2-5 microns in diameter and conduct at rates of 12–35 m/s.
 
Activation of C fibers releases a combination of glutamate and substance P, and is responsible for the delayed second pain (also called slow pain or protopathic pain) which is the dull, intense, diffuse, and unpleasant feeling associated with a noxious stimulus. Unmyelinated C fibers are 0.4 –1.2 m in diameter and they conduct at low rates of 0.5–2 m/s.
 
Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 8. Somatosensory Neurotransmission: Touch, Pain, and Temperature. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong’s Review of Medical Physiology, 24e. 

Q. 3

A person is able to sense pain and temperature normally. Which of the following type of nerve fiber is involved in carrying pain and temperature?

 A

A alpha

 B

A beta

 C

A gamma

 D

A delta

Q. 3

A person is able to sense pain and temperature normally. Which of the following type of nerve fiber is involved in carrying pain and temperature?

 A

A alpha

 B

A beta

 C

A gamma

 D

A delta

Ans. D

Explanation:

A delta nerve fiber is involved in transmitting pain and temperature in the body. It’s conduction velocity is 12-30 m/s. 
 
A alpha fiber is involved in carrying proprioception and somato motor sensation. It’s conduction velocity is 70-120 m/s. 
A beta fiber is involved in carrying touch and pressure sensation. It’s conduction velocity is 30- 70m/s. 
A gamma acts as motor to the muscle spindle. It’s conduction velocity is 15 – 30m/s. 
 
Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 4. Excitable Tissue: Nerve. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong’s Review of Medical Physiology, 24e

 


Q. 4

Which of the following sensation is carried by A alpha nerve fiber?

 A

Touch

 B

Temperature

 C

Pressure

 D

Proprioception

Q. 4

Which of the following sensation is carried by A alpha nerve fiber?

 A

Touch

 B

Temperature

 C

Pressure

 D

Proprioception

Ans. D

Explanation:

A alpha fibers carry proprioception and somatomotor sensation. It’s conduction velocity is 70-120 m/s. 
  • A delta nerve fiber is involved in transmitting pain and temperature in the body. It’s conduction velocity is 12-30 m/s. 
  • A beta fiber is involved in carrying touch and pressure sensation. It’s conduction velocity is 30- 70m/s. 
  • A gamma acts as motor to the muscle spindle. It’s conduction velocity is 15 – 30m/s. 
Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 4. Excitable Tissue: Nerve. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong’s Review of Medical Physiology, 24e.


Q. 5

Among the following nerve fibres the one with lower conduction velocity is:

 A

A alpha

 B

A beta

 C

A gamma

 D

C

Q. 5

Among the following nerve fibres the one with lower conduction velocity is:

 A

A alpha

 B

A beta

 C

A gamma

 D

C

Ans. D

Explanation:

Velocity of conduction in a nerve is affected by myelination, diameter, capacitance and resistance. Velocity is directly proportional to degree of myelination, diameter and capacitance and inversely proportional to resistance. C fibres are unmyelinated hence it will have the lower conduction velocity compared to myelinated A and B nerve fibres.

Ref: Ganongs, review of medical physiology, 21st Edition, Page 60


Q. 6

Kinesthetic sensation is:

 A

Transmitted by the (3-type of sensory nerve)

 B

Located in Merkl’s disc

 C

Transmitted by Meissner’s corpuscles

 D

Means abnormal perception of sensation

Q. 6

Kinesthetic sensation is:

 A

Transmitted by the (3-type of sensory nerve)

 B

Located in Merkl’s disc

 C

Transmitted by Meissner’s corpuscles

 D

Means abnormal perception of sensation

Ans. A

Explanation:

A i.e. Transmitted by the 13- type of sensory nerve

Kinesthetic sensation is ability to perceive the extent, direction or rate of movements. i.e. perception of touch and pressure and is therefore transmitted by Afl type of fibersQ.



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