Muscle Tissue and Structure (Exam #3)

Vocabulary and structural hierarchy of muscle tissue including connective tissue layers, cellular properties, and development.

Electrical excitability

The ability to respond to a stimulus, causing a local voltage change in the resting membrane by initiating movement of ions across the plasma membrane of the excitable cell.

Contractility

The ability of muscle cells to slide past one another to cause body movement and perform other muscle functions.

Extensibility

The ability for lengthening to occur because contractile proteins slide past one another to decrease their degree of overlap.

Elasticity

A property of a cell dependent on the release of tension in the spring-like connectin protein associated with contractile proteins.

Myoblasts

Groups of embryonic muscle cells ($100\,\mu m$ to $30\text{ centimeters}$) that fuse to form single skeletal muscle fibers during development.

Epimysium

A layer of dense irregular connective tissue that surrounds whole skeletal muscles.

Perimyrium

Tough, fibrous connective tissue sleeves around each fascicle that protect and support the tissue.

Endomysium

Areolar connective tissue that makes up a delicate covering to electrically insulate muscle fibers.

Tendon

A thick, cord-like structure composed of dense regular connective tissue.

Apneurosis

A thin, flattened sheet of dense regular connective tissue.

T-tubules (transverse)

Invaginations of the sarcolemma physically connected to the sarcoplasmic reticulum that contain voltage-gated $Na^+$ channels and $K^+$ channels.

Myofilaments

Intracellular protein filaments that are bundled and enclosed by the sarcoplasmic reticulum.

Myofibrils

Bundled myofilaments located within the muscle fiber that are enclosed by the sarcoplasmic reticulum.

Muscle Fiber

The muscle cell unit that is enclosed by the sarcolemma and contains myofibrils.

Three key functions of muscle tissue

1. Produce movement, 2. Maintain posture and body composition, 3. Maintain body temperature.

Muscle structure hierarchy (smallest to largest)

Myofilaments, Myofibrils, Muscle Fiber.

Contractile proteins

Generate force

Contractile Proteins

Generate force