Explain three different contractions muscles are able to ach

Explain three different contractions muscles are able to achieve and discuss the limiting factors that control muscle contraction?

Solution

Muscular contraction os mainly classified into two types

i. Isotonic contraction: in this type the tension remains the same and the length of the fibre is altered. as the name suggests - iso = same,tonic = tension

for example: simple flexion of arm, where shortening of muscle fibres occur but tension doesn\'t change.

ii.isometric contraction: in this case length of muscle fibres remains the same and the yension is increased.

example: pulling any heavy object when muscles become stiff and strained with increased tension but the length doesn\'t change.

iii. The third type is simple muscle contraction or Twich or Curve: when stimulus with threshold strength is applied , the muscle contracts and then relaxes. contraction period is always shorter than relaxation period.

FACTORS LIMITING THE FORCE OF CONTRACTION:

1. Effect of strength of stimulus:

with different strength of stimulus, the force of contraction also differs.

there are five types:

a) subminimal stimulus: it is less than minimal strength and doesn\'t produce any response if applied once.

b) threshold stimulus: it is the least strength of stimulus at which minimum force of contraction is produced.

c) sub maximal stimulus: it produces more dorce of contraction than minimal stimulus.

d)Maximal stimulus: it produces almost maximum force of contaction.

e) Supramaximal stimulus: it causes maximum force of contraction,beyond which contraction can not be increased.

2. Effect of Number of stimulus:

contractility of muscle varies depending upon the number of stimuli.

a) single stimulus: muscle contracts once(simple muscle twich)

b) two successive stimuli: causes

i. beneficial effect

ii. superposition or wave stimulation

iii. summetion effect

( detail in textbook)

c. effects of multiple stimuli:

i. fatigue

ii. Tetanus

3. Effect of variations in temperature:

a. Warm temperature: about 40°c

i. excitability of muscle increases

ii. chemical process involved in muscular contraction are accelerated.

iii. Viscosity of muscle decreases.

b. Cold temperature: opposite to warm temp.

c. Heat rigor: above 60° c muscle undergo shortening and stiffening of fibres, due to coagulation of actin and myocin.

d. cold rigor. : it\'s a reversible phenomenon.

4.Effect of load:

load acting on muscl is oof two type.

i. Afterload: its th load , that acts on the muscle after the beginning of muscular contraction. E.g. afterload is lifting any object from the ground. only after beginning of muscular contraction.

ii. free load : it\'s the load , which acts on the muscle freely,even before onset of contraction of the muscle. example: filling water from tap by holding the bucket in hand.

(end)