Chapter 15 Types of Muscles
While many muscles contract under conscious control, some operate involuntarily without the need
for conscious thought.
These muscles are categorised into three types:
1. Skeletal muscle - This muscle forms the majority of the body's muscles and is attached to
bones to move parts of the body like the arms or legs.
2. Cardiac muscle - This muscle is unique to the heart, and functions to circulate blood.
3. Smooth muscle - This muscle is located in the walls of hollow organs like blood vessels and
the intestines, and typically functions to move substances through these organs.
Key differences between skeletal, cardiac, and smooth muscles
Each of the three muscle types has distinct structural and functional characteristics.
Feature Skeletal muscle Cardiac muscle Smooth muscle
Spindle-shaped, non-
Fibre structure Tubular, striated Branched, striated
striated
Nuclei per fibre Multiple Single Single
Regular, parallel Branching network of Unorganised, no
Arrangement
bundles of myofibrils myofibrils myofibrils
Control Voluntary Involuntary Involuntary
Type of Neurogenic - contracts Myogenic - contracts Neurogenic, and can
stimulation when stimulated by automatically without also stretch in
required motor neuron impulses nervous input response to pressure
Contraction Fast Intermediate Slow
, Feature Skeletal muscle Cardiac muscle Smooth muscle
speed
Contraction
Short Intermediate Long-lasting
duration
Skeletal muscle fibres and cardiac muscle fibres show regular striations or stripes due to the
arrangement of contractile proteins within myofibrils.
Smooth muscle fibres show no striations or stripes under the microscope.
While many muscles contract under conscious control, some operate involuntarily without the need
for conscious thought.
These muscles are categorised into three types:
1. Skeletal muscle - This muscle forms the majority of the body's muscles and is attached to
bones to move parts of the body like the arms or legs.
2. Cardiac muscle - This muscle is unique to the heart, and functions to circulate blood.
3. Smooth muscle - This muscle is located in the walls of hollow organs like blood vessels and
the intestines, and typically functions to move substances through these organs.
Key differences between skeletal, cardiac, and smooth muscles
Each of the three muscle types has distinct structural and functional characteristics.
Feature Skeletal muscle Cardiac muscle Smooth muscle
Spindle-shaped, non-
Fibre structure Tubular, striated Branched, striated
striated
Nuclei per fibre Multiple Single Single
Regular, parallel Branching network of Unorganised, no
Arrangement
bundles of myofibrils myofibrils myofibrils
Control Voluntary Involuntary Involuntary
Type of Neurogenic - contracts Myogenic - contracts Neurogenic, and can
stimulation when stimulated by automatically without also stretch in
required motor neuron impulses nervous input response to pressure
Contraction Fast Intermediate Slow
, Feature Skeletal muscle Cardiac muscle Smooth muscle
speed
Contraction
Short Intermediate Long-lasting
duration
Skeletal muscle fibres and cardiac muscle fibres show regular striations or stripes due to the
arrangement of contractile proteins within myofibrils.
Smooth muscle fibres show no striations or stripes under the microscope.
