Classification of muscle

Physiology › Muscles › Classification of Muscles
Physiology • Muscles

CLASSIFICATION OF MUSCLES

Classification of muscles based on striations, control and situation, with comparison of skeletal, cardiac and smooth muscles.

1. MUSCLES IN HUMAN BODY

  • Human body has more than 600 muscles.
  • Functions performed by the muscles are responsible for our day-to-day activities.
  • Based on different factors, muscles are classified by three different methods:
  1. Classification depending upon striations.
  2. Classification depending upon control.
  3. Classification depending upon situation.

2. CLASSIFICATION DEPENDING UPON STRIATIONS

Depending upon presence or absence of cross striations, muscles are divided into two types:

1. STRIATED MUSCLE

  • Striated muscle has a large number of cross striations (transverse lines).
  • Skeletal muscle and cardiac muscle belong to this category.

2. NON-STRIATED MUSCLE

  • Non-striated muscle does not have cross striations.
  • It is also called:
    • Plain muscle
    • Smooth muscle
  • It is found in the wall of the visceral organs.

3. CLASSIFICATION DEPENDING UPON CONTROL

Depending upon control, muscles are classified into two types:

1. VOLUNTARY MUSCLE

  • Voluntary muscle → muscle controlled by will.
  • It is innervated by somatic nerve.
  • Skeletal muscles are voluntary muscles.

2. INVOLUNTARY MUSCLE

  • Involuntary muscle → muscle that cannot be controlled by will.
  • It is innervated by autonomic nerves.
  • Cardiac muscle and smooth muscle are involuntary muscles.

4. CLASSIFICATION DEPENDING UPON SITUATION

Depending upon situation, muscles are classified into three types:

1. Skeletal Muscle

2. Cardiac Muscle

3. Smooth Muscle

5. SKELETAL MUSCLE

  • Skeletal muscle is in association with bones forming the skeletal system.
  • Skeletal muscle forms 40 to 50% of body mass.
  • It is:
    • Voluntary
    • Striated
  • This muscle is supplied by somatic nerves.
  • Fibers of skeletal muscles are arranged parallel to each other.
  • In most skeletal muscles, muscle fibers are attached to tendons on either end.
  • Skeletal muscles are anchored to the bones by the tendons.

6. CARDIAC MUSCLE

  • Cardiac muscle forms the musculature of heart.
  • It is:
    • Striated
    • Involuntary
  • It is supplied by autonomic nerve fibers.

7. SMOOTH MUSCLE

  • Smooth muscle or visceral muscle is situated in association with viscera.
  • It is different from skeletal and cardiac muscle because of absence of cross-striations.
  • Hence, it is called smooth muscle.
  • Smooth muscles are supplied by autonomic nerve fibers.
  • Smooth muscles form the contractile units of the wall of various visceral organs.

8. FEATURES OF SKELETAL, CARDIAC AND SMOOTH MUSCLE

Feature Skeletal Muscle Cardiac Muscle Smooth Muscle
Location In association with bones In the heart In the visceral organs
Shape Cylindrical and unbranched Branched Spindle shaped, unbranched
Length 1 to 4 cm 80 to 100 μ 50 to 200 μ
Diameter 10 to 100 μ 15 to 20 μ 2 to 5 μ
Number of nucleus >1 1 1
Cross-striations Present Present Absent
Myofibrils Present Present Absent
Sarcomere Present Present Absent
Troponin Present Present Absent
Sarcotubular system Well developed Well developed Poorly developed
T-tubules Long and thin Short and broad Absent
Depolarization Upon stimulation Spontaneous Spontaneous
Fatigue Possible Not possible Not possible
Summation Possible Not possible Possible
Tetanus Possible Not possible Possible
Resting membrane potential Stable Stable Unstable
For trigger of contraction, calcium binds with Troponin Troponin Calmodulin
Source of calcium Sarcoplasmic reticulum Sarcoplasmic reticulum Extracellular fluid
Speed of contraction Quick Intermediate Slow
Neuromuscular junction Well defined Ill-defined Ill-defined
Action Voluntary action Involuntary action Involuntary action
Control of action Neurogenic Myogenic Neurogenic and myogenic
Nerve supply Somatic nerves Autonomic nerves Autonomic nerves

9. NEUROMUSCULAR SYSTEM

  • Central nervous system, somatic nervous system and skeletal muscle, which work together to perform various movements of the body, are collectively called the neuromuscular system.
CLASSIFICATION OF MUSCLES
Physiology • Muscles