THE MUSCULAR SYSTEM
Characteristics of muscles
1.
Muscle cells are elongated
(muscle cell = muscle fiber)
2.
Contraction of muscles is due to the movement of
microfilaments
3.
All muscles share some terminology
1. Prefix myo refers to muscle
2. Prefix mys refers to muscle
3. Prefix sarco refers to flesh
The Muscular system
Muscles are responsible for all types of
body movement
Three basic muscle types are found in the
body
1. Skeletal muscle
2. Cardiac muscle
3. Smooth muscle
Skeletal muscle
Most are attached by tendons to bones
Cells are multinucleate
Striated – have visible banding
Voluntary – subject to conscious control
Cells are surrounded and bundled by
connective tissue
6. Sites of muscle attachment
– Bones
– Cartilages
– Connective tissue coverings
1.
2.
3.
4.
5.
1.
2.
3.
4.
5.
Smooth muscle
Has no striations
Spindle-shaped cells
Single nucleus
Involuntary – no conscious
control
Found mainly in the walls
of hollow organs
Cardiac Muscle
1.
2.
3.
4.
5.
Has striations
Usually has a single
nucleus
Joined to another
muscle cell at an
intercalated disc
Involuntary
Found only in the
heart
Functions of muscles
1. Produce movement
2. Maintain posture
3. Stabilize joints
4. Generate heat
Properties of skeletal muscle activity
Irritability – ability to receive and respond to a
stimulus
2. Contractility – ability to shorten when an
adequate stimulus is received
3. Skeletal muscles must be stimulated by a
nerve to contract
1.
STOP
Gross Anatomy of the Muscular System
Nerve stimulus to muscles
Motor unit
– One neuron
– Muscle cells stimulated by that neuron
Nerve stimulus to muscles
1. Neuromuscular junctions – association
2.
3.
4.
5.
6.
site of nerve and muscle
Synaptic cleft – gap between nerve and
muscle
Nerve and muscle do not make contact
Area between nerve and muscle is filled
with interstitial fluid
Sodium rushing into the cell generates an
action potential
Once started, muscle contraction cannot
be stopped
Contraction of a skeletal muscle
1. Muscle fiber contraction is “all or none”
2. Within a skeletal muscle, not all fibers
may be stimulated during the same
interval
3. Different combinations of muscle fiber
contractions may give differing
responses
4. Graded responses – different degrees of
skeletal muscle shortening
Twitch
Single, brief contraction
Not a normal muscle function
Tetanus (summing of contractions)
One contraction is immediately followed by another
The muscle does not completely return to a resting state
The effects are added
Muscle response to strong stimuli
1. Muscle force depends upon the number
of fibers stimulated
2. More fibers contracting results in greater
muscle tension
3. Muscle can continue to contract unless
they run out of energy
STOP
Manual Muscle Testing Activity
Energy for muscle contraction
1. Initially, muscles used stored ATP for
energy
2. Bonds of ATP are broken to release
energy
3. Only 4-6 seconds worth of ATP is stored
by muscles
4. After this initial time, other pathways
must be utilized to produce ATP
Aerobic Respiration
1. Series of metabolic
pathways that occur
in the mitochondria
2. Glucose is broken
down to carbon
dioxide and water,
releasing energy
3. This is a slower
reaction that
requires continuous
oxygen
Anaerobic Respiration
1.
2.
3.
4.
5.
6.
Reaction that breaks down
glucose without oxygen
Glucose is broken down to
pyruvic acid to produce some
ATP
Pyruvic acid is converted to
lactic acid
This reaction is not as efficient,
but is fast
Huge amounts of glucose are
needed
Lactic acid produces muscle
fatigue
Muscle fatigue and oxygen debt
1. When a muscle is fatigued, it is unable to
contract
2. The common reason for muscle fatigue is
oxygen debt
Oxygen must be “repaid” to tissue to
remove oxygen debt
Oxygen is required to get rid of
accumulated lactic acid
3. Increasing acidity (from lactic acid) and lack of
ATP causes the muscle to contract less
Types of muscle contractions
1. Isotonic contractions
Myofilaments are able to slide past
each other during contractions
The muscle shortens
2. Isometric contractions
Tension in the muscles increases
The muscle is unable to shorten
Muscle tone
1. Some fibers are contracted even in a
relaxed muscle
2. Different fibers contract at different times
to provide muscle tone
3. The process of stimulating various fibers
is under involuntary control
Abnormal Muscle Tone
CRAMPS
SPASMS
SPASTICITY
FLACCIDITY
PARALYSIS
Abnormal Muscle Tone
Cramps and spasms are conditions of
the muscles
Spasticity, flaccidity and paralysis are
conditions of the muscles usually caused
by an underlying neurological injury or
disease.
CRAMPS
Cramps - A cramp is an involuntary and
forcibly contracted muscle that does
not relax.
Cramps can affect any muscle under your
voluntary control (skeletal muscle).
Muscles that span two joints are most
prone to cramping.
Cramps can involve part or all of a muscle,
or several muscles in a group.
CRAMPS
The most commonly affected muscle groups are:
– Back of lower leg/calf (gastrocnemius).
– Back of thigh (hamstrings).
– Front of thigh (quadriceps).
The exact cause of muscle cramps is unknown
(idiopathic)
Factors may be exercising or working in
intense heat, dehydration and depletion of
salt and minerals (electrolytes).
CRAMPS
Treatment and prevention Cramps
usually go away on their own without
seeing a doctor. Self-care:
Stop doing whatever activity triggered the
cramp.
Gently stretch and massage the cramping
muscle, holding it in stretched position
until the cramp stops.
Apply heat to tense/tight muscles, or cold
to sore/tender muscles.
SPASMS
A charley horse is the common name for a
muscle spasm, particularly in the leg.
Muscle spasms can occur in any muscle in
the body. When a muscle is in spasm, it
contracts involuntarily and does not relax.
Muscle spasms commonly occur when
a muscle is over-used or injured. The
muscle may keep firing small contractions.
It may be that nerves working with the
muscle become irritated.
SPASMS
At the first sign of a muscle spasm, stop
your activity and try stretching and
massaging the affected muscle. Heat will
relax the muscle at first, although ice may
be helpful after the initial spasm and pain
has improved.
SPASTICITY
Spasticity: A state of increased tone of
a muscle (and an increase in the deep
tendon reflexes). For example, with
spasticity of the legs (spastic paraplegia)
there is an increase in tone of the leg
muscles so they feel tight and rigid and the
knee jerk reflex is exaggerated. It may
interfere with gait, movement and speech.
Spasticity is caused by neurological
injuries and diseases.
FLACCIDITY
Muscle Flaccidity: Weak and soft
muscles with decreased resistance to
movement, increased mobility and
greater than normal range of
movements. Flaccidity is caused by
neurological injuries and diseases.
PARALYSIS
Paralysis is the complete loss of
muscle function for one or more
muscle groups. Paralysis often
includes loss of feeling in the affected
area. Paralysis is caused by
neurological injuries and diseases.
Muscular Injuries
SPRAINS
STRAINS
RUPTURED TENDONS
SPRAINS
A sprain is an injury to a ligament
The ligaments can be injured by being
stretched too far from their normal
position.
The most common symptoms of a sprain
are: pain, swelling, and bruising of the
affected joint. Symptoms will vary with the
intensity of the sprain or strain.
STRAINS
A strain is an injury to a muscle or
tendon.
Strains are caused by pulling too far on a
muscle, or by pulling a muscle in one
direction while it is contracting in the other.
Strains can also be caused by chronic
activities that develop an overstretching of
the muscle fibers.
SPRAINS
SPRAINS
STRAINS
STRAINS
Can Strains and Sprains be
prevented?
Unfortunately, not all sprains and strain can
be prevented. Some helpful hints on how
to avoid strains and sprains are listed
below.
Stretch before you exercise or workout.
Wear proper shoes for the activity.
Warm up properly before activities.
Do not run on icy or uneven surfaces.
RUPTURED TENDONS
A tendon is the fibrous tissue that attaches
muscle to bone in the human body.
The forces applied to a tendon may be
more than 5 times your body weight.
In some rare instances, tendons can snap
or rupture.
Ruptured tendons can be treated either
surgically or medically depending on the
severity of the rupture.
RUPTURED TENDONS
The 4 most common areas of tendon rupture
are as follows:
Quadriceps
Achilles
Rotator cuff
Biceps
Ruptured Tendon Symptoms
A snap or pop you hear or feel
Severe pain
Rapid or immediate bruising
Marked weakness
Inability to use the affected arm or leg
Inability to move the area involved
Inability to bear weight
Deformity of the area
Ruptured Achilles Tendon
WARNING!
THE NEXT SLIDE CONTAINS
A PHOTO OF A SURGICAL
REPAIR
Repair of the Ruptured Achilles
Tendon
Ruptured Extensor Tendon
Ruptured Quadriceps Tendon
RUPTURED PATELLA TENDON
PatellarTendon Disorders
Patellar Tendonitis (jumper’s knee)
– Inflammation of the patellar tendon
Patella-Femoral Syndrome
– Irritation on the underside of the patella
– Can lead to softening or loss of the underside
cartilage lining
Osgood-Schlatter Disease
– Irritation where the patella tendon inserts on
the tibia
– Mostly occurs in boys during a growth spurt
Muscles and body
movement
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
How to describe how muscles are
used in motion
1. Prime mover: muscle with the major
responsibility for a certain movement
2. Antagonist: muscle that opposes or
reverses a prime mover
3. Synergist: muscle that aids a prime
mover in a movement and helps prevent
rotation
4. Fixator: stabilizes the origin of a prime
mover