Muscle Structure: Electrical + Mechanical components of muscle fiber & Myofliaments

3 electrical components of muscle fiber

Component	Description
Sarcolemma	The cell membrane of a muscle fiber.
T-tubules	Inward folds of the sarcolemma that extend into the muscle fiber.
Sarcoplasmic reticulum	Smooth ER of skeletal muscle; stores and releases calcium ions (Ca²⁺).

Sarcolemma

cell membrane of muscle fiber

T-tubules

Inward folds of the sarcolemma that extend into the muscle fiber.

Sarcoplasmic Reticulum

Smooth ER of skeletal muscle; stores and releases calcium ions (Ca²⁺).

3 components of mechanical muscle fiber

• Myofibril

• Myofliament

• Sacromere

Myofibril

thread-like proteins chains that are inside muscle fibers & contains myofilaments

Myofilaments-

proteins that make up myofibrils & contain actin + myosin

Sarcomere

• The basic structural unit of striated muscle and its contractile unit.

• join end-to-end to create myofibrils.

actin

• thin myofilament

• resemble 2 strands of pearls

• contains troponin & Tropomyosin

Actin — Troponin

Binding cite for Ca2+

Actin— Tropomyosin

• rope wraps

• blocks myosin binding site

myosin

• thick myofilament

• resemble gold clubs

• Rod & heads

• Bind Actin

• Bind ATP

• Joins at M line

sarcomere

is the basic structural unit of striated muscle and the contractile unit. It contains actin and myosin arranged to allow muscle contraction.

• Join end-to-end to create myofibrils.

• Are separated by Z-discs.

• Have repeating light and dark bands that create the striated appearance of muscle.

Z-disc (Z-disk)
M-line
H-zone
I-band
A-band

Protein fibers that form the attachment site for actin. Contains no myosin.

Where myosin is anchored.

Center of the sarcomere; contains only myosin.

Light band; contains only actin.

Dark band; extends the length of the myosin filaments and includes the area where actin and myosin overlap.

arrangement/drawing