1. PROPERTIES OF SKELETAL MUSCLE

2. EXCITABILITY CONTRACTILITY CONDUCTIVITY TONICITY REFRACTORY PERIOD

3. I.EXCITABILITY
Definition: It is the change in potential and the consequent responses inherent to the tissues, in response to a stimulus. Stimulus: It is the change in the external environment bringing about excitation in an excitable tissue.

4. TYPES OF STIMULUS Electrical- commonly used in labs Mechanical Thermal
Chemical

5. QUALITY OF STIMULUS
Strength of stimulus
Duration of stimulus

6. STRENGTH-DURATION CURVE
Strength (mv)
STRENGTH-DURATION CURVE C 2R
RHEOBASE
U.T
DURATION IN ms

7. Rheobase: the minimum strength of the current acting on the muscle for a variable period that can bring about a response.
Utilization time: the minimum duration for which a current of rheobase strength is applied to excite an excitable tissue
Chronaxie: is defined as the shortest duration of stimulus required to excite a tissue by a current strength equal to twice of rheobase voltage.
Chronaxie of a tissue is a definite measure of its excitability.

8. II.CONTRACTILITY
Def: internal events of the muscle which are manifested by shortening or development of tension or both.
Types of contraction:
1) isotonic contraction
2) isometric contraction

9. Muscle-twitch (simple muscle curve): The contraction and relaxation of skeletal muscle in response to a single adequate stimulus
All or None response
An individual muscle fiber exhibits contraction of an uniform intensity once their particular threshold has been reached

10. FACTORS AFFECTING CONTRACTION
Effect of multiple stimuli: 1)effect of 2 successive stimuli: i) beneficial effect ii) superposition iii) summation 2) more than two stimuli: i) clonus ii) tetanus iii) treppe iv) fatigue

11. Increase in the temperature
Decrease in the viscosity
Availability of more Ca++
Ca ++ from the first contraction is not completely pumped into the saroplasmic reticulum
Second stimulus releases Ca ++ and adds to the remaining Ca ++ from the first contraction

14. FATIGUE
Definition: it is a decrease in the performance due to continuous and prolonged activity
Nerve is indefatigable

15. Effect of load on muscle contraction
1. Free-load
2. After-load
Effect of temperature on muscle contraction
1. Heat rigor
2. Calcium rigor
3. Rigor mortis

16. III. CONDUCTIVITY
Velocity of action potential conduction across skeletal muscle is 5m/sec
In nerves it is up to 120m/sec
Conduction is along the Sarcolemma and moves along the T-tubules

17. V. REFRACTORY PERIOD
a) Absolute refractory period b) Relative refractory period Whole of latent period is refractory Absolute refractory period (0.05 sec) Relative refractory period (0.05 sec) Totally it is 0.1 sec

18. Features of red and white muscle
RED (Slow) MUSCLE
WHITE (Fast) MUSCLE
Myoglobin content is more
Myoglobin content is less
Sarcoplasmic reticulum is less extensive
Sarcoplasmic reticulum is more extensive
Mitochondria are more in number
Mitochondria are less in number
Response is slow with long latent period
Response is rapid with short latent period
Contraction is less powerful
Contraction is more powerful
Fatigue occurs slowly
Fatigue occurs quickly
Depends upon cellular respiration for ATP production
Depends upon glycolysis for ATP production