Nerve fibers can be classified based on their structure and distribution. There are two main types - myelinated and unmyelinated fibers. Nerve fibers also include somatic and autonomic fibers. Somatic fibers innervate skeletal muscles and the neurotransmitter is acetylcholine, leading to muscle excitation or central inhibition. Autonomic fibers innervate smooth, cardiac muscles and glands to maintain homeostasis, causing excitation or inhibition. Important properties of nerve fibers include excitability, conductivity, unfatigability, refractory periods, all-or-none response, summation, and accommodation.

1. Nerve Fibers
K Krupa Sagar
Dept. of Pharmacology

2. Neuron

5. Nerve Fiber

9. 1.Depending on the Structure

11. Myelin sheath

13. 2.Depending on Distribution

14. Somatic nerve fibers
• These are α type motor nerve fibers.
• The neurotransmitter released at the neuron endings is
acetylcholine(Ach).
• It always leads to muscles excitation . Inhibition takes place
centrally due to participation of interneurons.

15. Autonomic nerve fibers
• They innervate smooth muscles , cardiac muscles
and Glands.
• Their main work is to maintain homeostasis with the
help of autonomic nervous system.
• They can lead to either excitation or inhibition of
Effector organs.

16. Properties of Nerve Fiber

17. Important Properties
• Excitability
• Conductivity
• Unfatigability
• Refractive period
• All or none response
• Summation
• Accommodation

18. Excitability:
• nerve fibres are highly excitable tissue
• respond to various stimuli
• Capable of generating electrical impulse
Conductivity:
• action potential is generated in the nerve fibre,
which is propagated along its entire length to the
axon terminal.

19. Refractive period:
• during action potential the excitability of a nerve
become reduced
• that is a new impulse cannot be generated during a
Action Potential
• Types:
a. Absolute refractory period (ARP)
b. Relative refractory period( RRP)

20. Unfatiguability :
• Nerve fibres can not be fatigued even when they are
stimulated continuously.
All or none response:
• Either all of the action potential is seen or none at all
• If a stimulus of threshold strength is applied action
Potential will be generated
• Further increase in strength of stimulus or duration
has no effect on amplitude of action Potential
• But can affect frequency

21. Summation:
• Application of a sub threshold stimulus does not
evoke an action potential. However if sub threshold
stimuli are applied in rapid succession they are
added and they produce an action potential.
Accommodation:
• Application of continuous stimuli may decrease the
excitability of nerve fibre.