Physiology (Nerve potential and properties of nerve) 1st year

Bismillahirahmanirrahim

Good morning any of my friend in Malaysia =)

Ok, this morning I've read about Nerve potential and properties of nerve :) In shaa Allah I'll share what I read and what information that still stick in my head ;P

Ok.. first of all, in this topic, we must consider those few basic things :

1. What is mixed nerve?

2. What is Compound Nerve Action Potential (CNAP)?

3. Classification of nerve fibre according to Erlanger-Gasser

4. How impulse was send in myelinated and unmyelinated nerve fibre.

5. What factors influence conduction of nerve impulse?

Ok..

1. What is mixed nerve?

Mixed nerve is family of nerve fibre that have various speed of conduction.

2. Compund Nerve Action Potential (CNAP) is when action potential shows multiple peak.

Subthreshold stimulus : no response

Threshold stimulus : low response

Maximal threshold : propotional until it strong enough to excite all axon

Suprathreshold: no more increase of action potential.

3. Classifiction of nerve fibre according to Erlanger-Gasser.

There 3 types of nerve fibre.. (A, B, C)

#A#

Divided further into 

Alpha : For motor of somatic neuron. 

The biggest one with diameter 12-20 micron and velocity 70-120 m/s.

Beta: (TPM)- Touch, Pressure, Motor. 

Diameter: 4-12 micron and velocity : 30-70 m/s.

Gamma: Motor for muscle spindle.

Diameter 3-6 micron. Velocity: 15-30 m/s

Delta: (PuCaT)-Pain, Cold, Touch

Diameter: 2-5 micron. Velocity: 12-30 m/s

#B#

Function in preganglionic autonomic nerve

Diameter : < 3 micron

Velovity:3-15 m/s

#C#

Divided into:

1. Dorsal root

For pain and temperature

Diameter : 0.04 - 1.2 micron, velocity: 0.5 - 2.7 m/s

2. Sympathetic fibre

For post ganglionic sympathetic

Diameter : 0.3-1.3 micron

Velocity : 0.7-2.3 m/s

4. Impulse in myelinated nerve fibre:

- faster conduction 

-soltatory - leap from one myelin sheath to another myelin sheath

- Energy-efficient mode of conduction. Because it only open one channel at 'a node' rather than many channel in each adjacent segment of membrane.

-maintain: low intracellular Na+, low extracellular K+. Thus only small region of membrane repolarized and depolarized. Less ATP used for sodium-potassium pump.

In unmyelinated nerve fibre:

Conduction is slow. 

-no soltatory.

5. Factors that influence conduction of nerve impulse.

(6 factors)

1. Myelination
2.Diameter of nerve fiber. (Greater diameter, greater velocity)

3.Temperature (High temperature, high conduction)

4. Pressure (Pressure block blood supply to nerve, thus, nerve temporarily stop sending impulse ; numbness occur)

5. Local anaesthetics (loss sensation at particular part)

6.Hypoxia