Chapter 6 The Muscle Anatomy

The Muscular SystemThe Muscular System

Functions Movement Maintain posture Stabilize joints Generate heat

Three basic muscle types Skeletal muscle* Cardiac muscle Smooth muscle

Muscles and Body MovementsMuscles and Body Movements

-Movement is attained due to a muscle moving an attached bone

-Muscles are attached to at least two points Origin – attachment to

an immoveable bone Insertion – attachment

to a movable bone

Types of MusclesTypes of Muscles Prime mover – muscle with the major responsibility for a

certain movement Antagonist – muscle that opposes or reverses a prime

mover Synergist – muscle that aids a prime mover in a

movement and helps prevent rotation Fixator – stabilizes the origin of a prime mover

HamstringQuadsCalf & Glutes

Flexion Extension Rotation Abduction Adduction Circumduction

Ordinary Body Movements - Skeletal

Special Movements - SkeletalSpecial Movements - Skeletal

Dorsifelxion Plantar flexion Inversion Eversion Supination Pronation Opposition

Naming of Skeletal MusclesNaming of Skeletal Muscles

1. Direction. Ex: rectus (straight)

2. Size. Ex: maximus (largest)

3. Location. Ex: many named for bones (temporalis)

4. Number of origins. Ex: triceps (three heads)

5. Origin & insertion. Ex: sterno (on the sternum)

6. Shape. Ex: deltoid (triangular)

7. Action. Ex: flexor & extensor (flexes or extends bone)

Characteristics of MusclesCharacteristics of Muscles

Muscle cells are elongated (muscle cell = muscle fiber)

Contraction of muscles is due to the movement of microfilaments

All muscles share some terminology Prefix myo refers to muscle Prefix mys refers to muscle Prefix sarco refers to flesh

Skeletal Muscle CharacteristicsSkeletal Muscle Characteristics Most attached to bones by

tendons Multinucleate Striated – visible banding Voluntary – conscious

control Cells surrounded &

bundled by connective tissue

Connective Tissue WrappingsConnective Tissue Wrappings

Endomysium – around single muscle fiber

Perimysium – around a fascicle (bundle) of fibers

Epimysium – covers the entire skeletal muscle

Fascia – on the outside of the epimysium

Skeletal Muscle AttachmentsSkeletal Muscle Attachments Epimysium blends into a

connective tissue attachment- Tendon – cord-like structure- Aponeuroses – sheet-like

structure Sites of muscle attachment

- Bones- Cartilages- Connective tissue coverings

Smooth Muscle CharacteristicsSmooth Muscle Characteristics

No striations Spindle-shaped

cells Single nucleus Involuntary – no

conscious control Found mainly in

the walls of hollow organs

Cardiac Muscle CharacteristicsCardiac Muscle Characteristics

Has striations Single nucleus Joined to another

muscle cell at an intercalated disc

Involuntary Found only in the

heart

Microscopic Anatomy of Skeletal MuscleMicroscopic Anatomy of Skeletal Muscle

Nuclei are just beneath the sarcolemma

Sarcolemma – specialized plasma membrane

Sarcoplasmic reticulum – specialized smooth endoplasmic reticulum

Microscopic Anatomy of Skeletal MuscleMicroscopic Anatomy of Skeletal Muscle

Myofibrils - Bundles of myofilaments

- aligned to give distrinct bands I band = light band A band = dark band

Sarcomere - Contractile unit of a muscle fiber

Organization of the Sarcomere Thick filaments = myosin filaments

- protein myosin- ATPase enzymes

Thin filaments = actin filaments- protein actin

Microscopic AnatomyMicroscopic Anatomy Myosin filaments have heads (extensions or

cross bridges) Myosin and actin overlap somewhat At rest, there is a bare zone that lacks actin

filaments Sarcoplasmic

reticulum (SR) – for storage of calcium

Properties of Skeletal MuscleProperties of Skeletal Muscle Irritability – ability to

receive and respond to a stimulus

Contractility – ability to shorten when an adequate stimulus is received

Nerve Stimulus to MusclesNerve Stimulus to Muscles

Skeletal muscles must be stimulated by a nerve to contract

Motor unit- One neuron- Muscle cells

stimulated by that neuron

Nerve Stimulus to MusclesNerve Stimulus to Muscles Neuromuscular junctions – association

site of nerve and muscle