Fasciculation , Fibrillation , clonus and Tetanic contractions

IOM, TU , NEPAL

1. SY “es

TETANUS

Fibrillation, Fasiculation,
Clonus and Tetanic culation, DN

noe

2. Objectives :

To Explain the physiological basis of :
1. Fibrillation and Fasiculation

2.Clonus and tetanic contraction

3. Motor Unit:

A motor unit consists of :

1. Single motor neuron

2. It’s axonal branches

3.All the muscle fibers supplied by them

4. ‘Axon terminals at
neuromuscular
Junctions

Spinal cord

Motor Motor
unit? unit2

‘Axon of motor neurons extend from the spinal cord to the muscle.
There each axon divides into a number of axon terminals that form neromuscular
junctions with muscle fibers scattered throughout the muscle.

Image Source :https://github.com/iandanforth/pymuscle

5. Electromyography(EMG)

Record of electrical activity of muscles & motor

neurons.

Via Cathode Ray Oscilloscope(CRO) ~~?
Electrodes :

Metal disc - Skin/Superficial muscles à

Hypodermic needle - Muscles

6. Normal EMG:

1.At rest : All most no activity

2.With increase in Force of contraction :
a. Recruitment of more motor units
b. increase in frequency of stimulation

(Amplitude - no of motor units involved)

7. Fibrillation

e Involuntary contraction of individual muscle fibres

+ Can't be seen through skin

¢ Follows denervation due to increased sensitivity to Ach

e Is seen both in neuropathy and myopathy

8. FIBRILLATION EMG

Characteristics:
+ 10-100 micro volt in Amplitude
« 1-2 millisecond in duration

e frequency of about 10Hz

9. Fasiculation
+ Coarse contraction(involuntary) of individual
motor units

« visible through skin

© more often occurs in :(Neuropathy)

+ Anterior motor neuron Animated image showing involuntary twitching

. . ue in the upper eyelid of a young adult male
diseases(Poliomyelitis) E

e Peripheral motor nerve injury
« -occasionally seen normally(Physiological

Fasiculation)
(Image source :
https://en.wikipedia.org/wiki/Fasciculation)

10. Fasiculation EMG

+ Characteristics :
+ 50-500 micro volt in amplitude
e 2-4 millisecond in duration

¢ frequency of about 2- 20 Hz

11. EMG Comaparision

ny L

50 ms
Fibrilation

7, 100 uv L

50 ms . .
Fasciculation

12. Properties of Skeletal muscle Contraction :

+ TWITCH SUMMATION INCOMPLETE COMPLETE
TETANUS TETANUS

Tension

stimulus Time (ms)

Image Source : https://shorturl.at/ioN16

13. Clonus Contraction

¢ Also known as Unfused / Incomplete tetanus(tetanic
contraction)
* periods of incomplete relaxation between the

maintained contractions

14. Tetanic contraction

-Also called Complete / Fused contraction

- Muscle stimulated repeatedly at a very high frequency,
continuous activation of contractile mechanism occurs without
any relaxation, resulting in a sustained contraction known as

tetanus / tetanic contraction

15. Pathogenesis of Tetanus

16. Exotoxin - Tetanospasmin taken up by cholinergic neurons --->
Retrograde axonal transport ---->

Reach inhibitory GABAnergic and Glycenergic neurons in Spinal
cord->>

No synaptic release of Inhibitory Neurotransmittors-->
Continuous high frequency stimulation --> Tetanic contraction i.e.

Spastic Paralysis

17. Conclusion:

1. Fibrillation :

Contraction of individual fibres , invisible by naked eye, seen in myopathy
Fasiculation :

Contraction of entire motor unit, can be seen by naked eye, seen in both

neuropathy and myopathy

2. Clonus contraction - has incomplete relaxation

Tetanic contraction - no relaxation - sustained contraction

18. Bibliography

e Gyutun and Hall Textbook of Medical Physiology,14th
Edition, Elsevier

+ Understanding Medical Physiology(A text book for medical
students)-R.L. Bijlani - JAYPEE publication

e Essentials of Medical Physiology-6th Edition, K.Sembulingum

19. Thank You