Skeletal Muscle Anatomy and Function: Key Concepts for Students

Skeletal muscle

What type of muscle tissue is under voluntary control?

Two (origin and insertion)

How many attachment sites does a typical muscle have?

Muscle tissue and connective tissue

What are the 2 major types of tissue found within skeletal muscle?

Connective tissue

What tissue provides the structural framework for skeletal muscle?

Connects muscle to bone and transmits contraction force

What is the primary function of a tendon?

Muscle fiber

What is the major structural and functional component of skeletal muscle tissue?

Muscle fiber

What is the alternate name for a skeletal muscle cell?

2.5 cm to over 30 cm (1 inch to 1+ foot)

What is the length range of an individual skeletal muscle fiber?

Fascicle

What is the term for a bundle of skeletal muscle fibers?

Dense fibrous connective tissue (collagen)

What is the major component of muscular fascia?

The structure it surrounds

What dictates how muscular fascia is named?

Endomysium

What is the fibrous fascia surrounding an individual muscle fiber?

Perimysium

What is the fibrous fascia surrounding a bundle of fibers (fascicle)?

Epimysium

What is the fibrous fascia surrounding an entire skeletal muscle?

Aponeurosis

What is the term for a broad, flat muscular fascia?

Sarcoplasm

What is the cytoplasm of a skeletal muscle fiber called?

Sarcoplasmic reticulum

What is the endoplasmic reticulum of a skeletal muscle fiber called?

Sarcolemma

What is the cell membrane of a skeletal muscle fiber called?

Very long, multinucleated, striated, voluntary contraction

List 4 ways skeletal muscle fibers are unusual/unique.

Define myofibril.

Cylindrical organelle in muscle fiber made of sarcomeres

Define sarcomere.

Functional unit of contraction within a myofibril

Myofilaments

Actin and myosin are classified as what type of filaments?

Alternating actin and myosin bands in sarcomeres

What creates the striated appearance of skeletal muscle tissue?

Sliding filament mechanism

What is the name of the mechanism by which a sarcomere shortens?

Nervous system

What system of the body communicates contraction to skeletal muscle fibers?

Calcium (Ca²⁺)

What ion is released by the sarcoplasmic reticulum into the sarcoplasm?

Actin (troponin)

Calcium ions attach to what filaments to expose binding sites?

Myosin

The heads of what filaments attach to actin binding sites?

Cross-bridges (myosin heads)

What structure creates a pulling force to bring actin toward the sarcomere center?

Tendon

What anatomical structure attaches a muscle to a bone?

Muscle shortens as it contracts

Define a concentric contraction.

Agonist (prime mover)

What do we call a muscle that is concentrically contracting?

Contractility

What must a muscle possess in order to shorten?

Mobile = insertion, Fixed = origin

Difference between mobile vs. fixed attachment site of a muscle?

Joint action (movement)

What is created when a muscle contracts and one attachment moves?

When the origin moves toward the insertion

What is a reverse action?

Relative stabilization of attachment sites

What determines which attachment site moves?

Name, Location, Joints crossed, Attachments, Actions

What is the 5-step approach to learning about a muscle?

Its action(s)

What does the line of pull determine for a muscle?

One

How many actions will a muscle have if it has one line of pull in a cardinal plane?

Flexion and adduction

The coracobrachialis oblique plane motion combines what 2 cardinal plane actions?

Three

How many lines of pull does the gluteus medius muscle possess?

Muscle that crosses and acts on one joint

Define a one-joint muscle.

Muscle that crosses and acts on more than one joint

Define a multijoint muscle.