Nerve fibers

Anatomy & Physiology

1. Nerve Fibers K Krupa Sagar Dept. of Pharmacology

2. Neuron

3. Nerve Fiber

4. 1.Depending on the Structure

5. Myelin sheath

6. 2.Depending on Distribution

7. 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 .

8. 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.

9. Properties of Nerve Fiber

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

11. 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.

12. 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: Absolute refractory period (ARP ) Relative refractory period( RRP)

13. 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 a ction Potential will be generated Further increase in strength of stimulus or duration has no effect on amplitude of action Potential But can affect frequency

14. 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 .