Dr. S. Mak LAB 9: MICROSCOPIC ANATOMY OF SKELETAL MUSCLES

Flashcards covering the microscopic anatomy of skeletal muscles, muscle fiber models, and the neuromuscular junction (NMJ) based on Dr. S. Mak's Lab 9.

Muscle fiber

A single muscle cell which is organized into microscopic levels of structure.

Myosin

The protein that makes up thick filaments within a muscle fiber.

Actin

The protein that makes up thin filaments within a muscle fiber.

Myofibril

Long, thread-like structures found inside the muscle fiber that contain myofilaments.

Endomysium

The connective tissue layer that surrounds an individual muscle fiber.

Myofilament

The even smaller structures (actin and myosin) that make up a myofibril.

Neuromuscular junction (NMJ)

The site where a motor neuron meets a muscle fiber to communicate.

Sarcolemma

The plasma membrane of a muscle fiber.

T-tubules

Transverse tubules that carry electrical signals into the muscle cell.

Sarcoplasmic reticulum

A specialized endoplasmic reticulum in muscle cells that stores calcium.

Terminal cisternae

Enlarged areas of the sarcoplasmic reticulum found on either side of a T-tubule.

Nucleus

Organelle found in skeletal, cardiac, and smooth muscles; skeletal muscle typically has multiple nuclei per fiber.

Mitochondria

Energy-producing organelles found within the muscle fiber.

Sarcomere

The functional unit of a muscle fiber, spanning from one Z disc to the next.

A band

The dark band observed in striated muscle, containing thick filaments.

I band

The light band observed in striated muscle, containing only thin filaments.

Z disc

The boundary line of a sarcomere where actin filaments are anchored.

M line

The dark line in the middle of the H zone.

H zone

The region in the center of the A band that contains only thick filaments.

Skeletal Muscle

A type of muscle characterized by striations and multiple nuclei.

Cardiac muscle

A type of muscle found in the heart that features striations, nuclei, and intercalated discs.

Smooth Muscle

A type of muscle that lacks striations and contains nuclei.

Intercalated discs

Specialized junctions between cardiac muscle cells.

Striations

The visible stripes seen in skeletal and cardiac muscle tissues.

Motor neuron

The nerve cell that transmits impulses from the central nervous system to a muscle.

Axon terminal

The end of the motor neuron axon that contains synaptic vesicles.

Motor end plate

The specialized region of the sarcolemma at the neuromuscular junction.

Myelin sheath (Schwann cells)

The insulating layer covering the axon of a motor neuron.

Synaptic vesicles

Sac-like structures in the axon terminal that contain chemical messengers.

Synaptic cleft

The narrow fluid-filled gap between the axon terminal and the motor end plate.