PHYSIOLOGY 244
A1 CONTENT
1
,MUSCLE PHYSIOLOGY
WEEK 1
Types of Muscle Tissue
There are three types of muscle tissue:
Muscle type Striated? Voluntary?
Skeletal muscle Yes Yes
Cardiac muscle Yes No
Smooth muscle No No
For this section, we are mainly concerned with skeletal muscle.
Skeletal Muscle
Skeletal muscle is also called:
• Striated muscle because it has a striped appearance under the microscope.
• Voluntary muscle because its contraction can be consciously controlled.
Skeletal muscle makes up approximately 30–40% of body weight.
Skeletal Muscle Fibres
The individual cells that make up skeletal muscle are called muscle fibres.
A muscle fibre is one skeletal muscle cell
2
,Skeletal muscle fibres:
• are attached to bones and therefore facilitate movement;
• are long cells;
• contain multiple nuclei within a single muscle fibre.
A whole skeletal muscle therefore contains many individual muscle fibres.
Organisation of Skeletal Muscle
whole muscle → muscle fascicle → muscle fibre → myofibril → thick and thin filaments
The diagram shows this hierarchy clearly: a whole skeletal muscle contains bundles
called fascicles, which contain muscle fibres, and the muscle fibres contain myofibrils.
Myofibrils
Inside each muscle fibre are many structures called myofibrils.
3
, Myofibrils are the specialised contractile elements of skeletal muscle: the structures
inside a muscle fibre that actually allow the muscle to contract.
They contain highly organised microfilaments, which are divided into:
1. Thick filaments
2. Thin filaments
The main proteins associated with these filaments are:
1. Myosin
2. Actin
The Sarcomere The Functional Unit of Skeletal Muscle.
A myofibril is not just one long continuous structure. It is divided into repeating units
called sarcomeres.
A sarcomere extends from one Z line to the next Z line
4
A1 CONTENT
1
,MUSCLE PHYSIOLOGY
WEEK 1
Types of Muscle Tissue
There are three types of muscle tissue:
Muscle type Striated? Voluntary?
Skeletal muscle Yes Yes
Cardiac muscle Yes No
Smooth muscle No No
For this section, we are mainly concerned with skeletal muscle.
Skeletal Muscle
Skeletal muscle is also called:
• Striated muscle because it has a striped appearance under the microscope.
• Voluntary muscle because its contraction can be consciously controlled.
Skeletal muscle makes up approximately 30–40% of body weight.
Skeletal Muscle Fibres
The individual cells that make up skeletal muscle are called muscle fibres.
A muscle fibre is one skeletal muscle cell
2
,Skeletal muscle fibres:
• are attached to bones and therefore facilitate movement;
• are long cells;
• contain multiple nuclei within a single muscle fibre.
A whole skeletal muscle therefore contains many individual muscle fibres.
Organisation of Skeletal Muscle
whole muscle → muscle fascicle → muscle fibre → myofibril → thick and thin filaments
The diagram shows this hierarchy clearly: a whole skeletal muscle contains bundles
called fascicles, which contain muscle fibres, and the muscle fibres contain myofibrils.
Myofibrils
Inside each muscle fibre are many structures called myofibrils.
3
, Myofibrils are the specialised contractile elements of skeletal muscle: the structures
inside a muscle fibre that actually allow the muscle to contract.
They contain highly organised microfilaments, which are divided into:
1. Thick filaments
2. Thin filaments
The main proteins associated with these filaments are:
1. Myosin
2. Actin
The Sarcomere The Functional Unit of Skeletal Muscle.
A myofibril is not just one long continuous structure. It is divided into repeating units
called sarcomeres.
A sarcomere extends from one Z line to the next Z line
4
