Download Ch 6 Muscle Anatomy

Chapter 6
The Muscle Anatomy
The Muscular System
Functions
 Movement
 Maintain posture
 Stabilize joints
 Generate heat
Three basic muscle types
 Skeletal muscle*
 Cardiac muscle
 Smooth muscle
Muscles 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 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
Hamstring
Quads
Calf & Glutes
Ordinary Body Movements - Skeletal
 Flexion
 Extension
 Rotation
 Abduction
 Adduction
 Circumduction
Special Movements - Skeletal
 Dorsifelxion
 Plantar flexion
 Inversion
 Eversion
 Supination
 Pronation
 Opposition
Naming 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 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 Characteristics
 Most attached to bones by
tendons
 Multinucleate
 Striated – visible banding
 Voluntary – conscious
control
 Cells surrounded &
bundled by connective
tissue
Connective 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 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 Characteristics
 No striations
 Spindle-shaped
cells
 Single nucleus
 Involuntary – no
conscious control
 Found mainly in
the walls of hollow
organs
Cardiac 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 Muscle
 Sarcolemma – specialized plasma
membrane
 Sarcoplasmic reticulum – specialized
smooth endoplasmic reticulum
 Nuclei are just beneath the sarcolemma
Microscopic 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 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 Muscle
 Irritability – ability to
receive and respond to
a stimulus
 Contractility – ability to
shorten when an
adequate stimulus is
received
Nerve 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 Muscles
 Neuromuscular junctions – association
site of nerve and muscle