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 muscle2. Cardiac muscle3. Smooth muscle

Skeletal muscle

1. Most are attached by tendons to bones2. Cells are multinucleate3. Striated – have visible banding4. Voluntary – subject to conscious control5. Cells are surrounded and bundled by

connective tissue6. Sites of muscle attachment

– Bones– Cartilages– Connective tissue coverings

Smooth muscle

1. Has no striations

2. Spindle-shaped cells

3. Single nucleus

4. Involuntary – no conscious control

5. Found mainly in the walls of hollow organs

Cardiac Muscle

1. Has striations

2. Usually has a single nucleus

3. Joined to another muscle cell at an intercalated disc

4. Involuntary

5. 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

1. 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

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Gross Anatomy of the Muscular SystemGross 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 site of nerve and muscle

2. Synaptic cleft – gap between nerve and muscle

3. Nerve and muscle do not make contact4. Area between nerve and muscle is filled

with interstitial fluid5. Sodium rushing into the cell generates an

action potential6. Once started, muscle contraction cannot

be stopped

Contraction of a skeletal muscleContraction of a skeletal muscle

1.1. Muscle fiber contraction is “all or none”Muscle fiber contraction is “all or none”2.2. Within a skeletal muscle, not all fibers may Within a skeletal muscle, not all fibers may

be stimulated during the same intervalbe stimulated during the same interval3.3. Different combinations of muscle fiber Different combinations of muscle fiber

contractions may give differing responsescontractions may give differing responses4.4. Graded responses – different degrees of Graded responses – different degrees of

skeletal muscle shorteningskeletal muscle shortening

TwitchSingle, 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 stateThe effects are added

Muscle response to strong stimuliMuscle response to strong stimuli

1.1. Muscle force depends upon the number Muscle force depends upon the number of fibers stimulatedof fibers stimulated

2.2. More fibers contracting results in greater More fibers contracting results in greater muscle tensionmuscle tension

3.3. Muscle can continue to contract unless Muscle can continue to contract unless they run out of energythey run out of energy

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Manual Muscle Testing ActivityManual Muscle Testing Activity

Energy for muscle contractionEnergy for muscle contraction

1.1. Initially, muscles used stored ATP for Initially, muscles used stored ATP for energyenergy

2.2. Bonds of ATP are broken to release Bonds of ATP are broken to release energyenergy

3.3. Only 4-6 seconds worth of ATP is stored Only 4-6 seconds worth of ATP is stored by musclesby muscles

4.4. After this initial time, other pathways After this initial time, other pathways must be utilized to produce ATPmust be utilized to produce ATP

Aerobic Respiration1. 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

1.1. Reaction that breaks down Reaction that breaks down glucose without oxygenglucose without oxygen

2.2. Glucose is broken down to Glucose is broken down to pyruvic acid to produce some pyruvic acid to produce some ATPATP

3.3. Pyruvic acid is converted to Pyruvic acid is converted to lactic acidlactic acid

4.4. This reaction is not as efficient, This reaction is not as efficient, but is fastbut is fast

5.5. Huge amounts of glucose are Huge amounts of glucose are neededneeded

6.6. Lactic acid produces muscle Lactic acid produces muscle fatiguefatigue

Anaerobic Respiration

Muscle fatigue and oxygen debtMuscle fatigue and oxygen debt

1.1. When a muscle is fatigued, it is unable to When a muscle is fatigued, it is unable to contractcontract

2.2. The common reason for muscle fatigue is The common reason for muscle fatigue is oxygen debtoxygen debt

Oxygen must be “repaid” to tissue to Oxygen must be “repaid” to tissue to remove oxygen debtremove oxygen debt

Oxygen is required to get rid of Oxygen is required to get rid of accumulated lactic acidaccumulated lactic acid

3.3. Increasing acidity (from lactic acid) and lack of Increasing acidity (from lactic acid) and lack of ATP causes the muscle to contract lessATP causes the muscle to contract less

Types of muscle contractionsTypes of muscle contractions

1.1. Isotonic contractionsIsotonic contractions

Myofilaments are able to slide past Myofilaments are able to slide past each other during contractionseach other during contractions

The muscle shortensThe muscle shortens

2.2. Isometric contractionsIsometric contractions

Tension in the muscles increasesTension in the muscles increases

The muscle is unable to shortenThe muscle is unable to shorten

Muscle toneMuscle tone

1.1. Some fibers are contracted even in a Some fibers are contracted even in a relaxed musclerelaxed muscle

2.2. Different fibers contract at different times Different fibers contract at different times to provide muscle toneto provide muscle tone

3.3. The process of stimulating various fibers The process of stimulating various fibers is under involuntary controlis under involuntary control

Abnormal Muscle ToneAbnormal Muscle Tone

CRAMPSCRAMPS

SPASMSSPASMS

SPASTICITYSPASTICITY

FLACCIDITYFLACCIDITY

PARALYSISPARALYSIS

Abnormal Muscle ToneAbnormal Muscle Tone

Cramps and spasmsCramps and spasms are conditions of are conditions of the musclesthe muscles

Spasticity, flaccidity and paralysisSpasticity, flaccidity and paralysis are are conditions of the muscles usually conditions of the muscles usually caused caused by an underlying neurological injury or by an underlying neurological injury or disease.disease.

CRAMPSCRAMPS

Cramps - Cramps - A cramp is an involuntary and A cramp is an involuntary and forcibly contracted muscle that does forcibly contracted muscle that does not relax.not relax. Cramps can affect any muscle under your Cramps can affect any muscle under your voluntary control (skeletal muscle). voluntary control (skeletal muscle). Muscles that span two joints are most Muscles that span two joints are most prone to cramping. prone to cramping. Cramps can involve part or all of a muscle, Cramps can involve part or all of a muscle, or several muscles in a group. or several muscles in a group.

CRAMPSCRAMPS

The most commonly affected muscle groups are: The most commonly affected muscle groups are: – Back of lower leg/calf (gastrocnemius). Back of lower leg/calf (gastrocnemius). – Back of thigh (hamstrings). Back of thigh (hamstrings). – Front of thigh (quadriceps). Front of thigh (quadriceps).

The exact cause of muscle cramps is unknown The exact cause of muscle cramps is unknown (idiopathic)(idiopathic)

Factors may be exercising or working in Factors may be exercising or working in intense heat, dehydration and depletion of intense heat, dehydration and depletion of salt and minerals (electrolytes).salt and minerals (electrolytes).

CRAMPSCRAMPSTreatment and preventionTreatment and prevention Cramps Cramps usually go away on their own without usually go away on their own without seeing a doctor. Self-care: seeing a doctor. Self-care:

Stop doing whatever activity triggered the Stop doing whatever activity triggered the cramp. cramp.

Gently stretch and massage the cramping Gently stretch and massage the cramping muscle, holding it in stretched position muscle, holding it in stretched position until the cramp stops. until the cramp stops.

Apply heat to tense/tight muscles, or cold Apply heat to tense/tight muscles, or cold to sore/tender muscles.to sore/tender muscles.

SPASMSSPASMS

A charley horse is the common name for a A charley horse is the common name for a muscle spasm, particularly in the leg. muscle spasm, particularly in the leg. Muscle spasms can occur in any muscle Muscle spasms can occur in any muscle in the body. When a muscle is in spasm, it in the body. When a muscle is in spasm, it contracts involuntarily and does not relax. contracts involuntarily and does not relax.

Muscle spasms commonly occur when Muscle spasms commonly occur when a muscle is over-used or injured.a muscle is over-used or injured. The The muscle may keep firing small contractions. muscle may keep firing small contractions. It may be that nerves working with the It may be that nerves working with the muscle become irritated.muscle become irritated.

SPASMSSPASMS

At the first sign of a muscle spasm, stop At the first sign of a muscle spasm, stop your activity and try stretching and your activity and try stretching and massaging the affected muscle. Heat will massaging the affected muscle. Heat will relax the muscle at first, although ice may relax the muscle at first, although ice may be helpful after the initial spasm and pain be helpful after the initial spasm and pain has improved. has improved.

SPASTICITYSPASTICITY

Spasticity:Spasticity: A state of increased tone of A state of increased tone of a musclea muscle (and an increase in the deep (and an increase in the deep tendon reflexes). For example, with tendon reflexes). For example, with spasticity of the legs (spastic paraplegia) spasticity of the legs (spastic paraplegia) there is an increase in tone of the leg there is an increase in tone of the leg muscles so they feel tight and rigid and the muscles so they feel tight and rigid and the knee jerk reflex is exaggerated. It may knee jerk reflex is exaggerated. It may interfere with gait, movement and speech. interfere with gait, movement and speech. Spasticity is caused by neurological Spasticity is caused by neurological injuries and diseases.injuries and diseases.

FLACCIDITYFLACCIDITY

Muscle Flaccidity:Muscle Flaccidity: Weak and soft Weak and soft muscles with decreased resistance to muscles with decreased resistance to movement, increased mobility and movement, increased mobility and greater than normal range of greater than normal range of movements.movements. Flaccidity is caused by Flaccidity is caused by neurological injuries and diseases.neurological injuries and diseases.

PARALYSISPARALYSIS

ParalysisParalysis is the complete loss of is the complete loss of muscle function for one or more muscle function for one or more muscle groups. Paralysis often muscle groups. Paralysis often includes loss of feeling in the affected includes loss of feeling in the affected area. Paralysis is caused by area. Paralysis is caused by neurological injuries and diseases.neurological injuries and diseases.

Muscular InjuriesMuscular Injuries

SPRAINSSPRAINS

STRAINSSTRAINS

RUPTURED TENDONSRUPTURED TENDONS

SPRAINSSPRAINS

A sprain is an injury to a ligamentA sprain is an injury to a ligament

The ligaments can be injured by being The ligaments can be injured by being stretched too far from their normal stretched too far from their normal position. position.

The most common symptoms of a sprain The most common symptoms of a sprain are: pain, swelling, and bruising of the are: pain, swelling, and bruising of the affected joint. Symptoms will vary with the affected joint. Symptoms will vary with the intensity of the sprain or strain. intensity of the sprain or strain.

STRAINSSTRAINS

A strain is an injury to a muscle or A strain is an injury to a muscle or tendon.tendon.

Strains are caused by pulling too far on a Strains are caused by pulling too far on a muscle, or by pulling a muscle in one muscle, or by pulling a muscle in one direction while it is contracting in the other. direction while it is contracting in the other.

Strains can also be caused by chronic Strains can also be caused by chronic activities that develop an overstretching of activities that develop an overstretching of the muscle fibers. the muscle fibers.

SPRAINSSPRAINS

SPRAINSSPRAINS

STRAINSSTRAINS

STRAINSSTRAINS

Can Strains and Sprains be Can Strains and Sprains be prevented?prevented?

Unfortunately, not all sprains and strain can Unfortunately, not all sprains and strain can be prevented. Some helpful hints on how be prevented. Some helpful hints on how to avoid strains and sprains are listed to avoid strains and sprains are listed below. below.

Stretch before you before you exercise or workout. or workout.

Wear proper shoes for the activity. Wear proper shoes for the activity.

Warm up properly before activities. Warm up properly before activities.

Do not run on icy or uneven surfaces. Do not run on icy or uneven surfaces.

RUPTURED TENDONSRUPTURED TENDONS

A tendon is the fibrous tissue that attaches A tendon is the fibrous tissue that attaches muscle to bone in the human body. muscle to bone in the human body. The forces applied to a tendon may be The forces applied to a tendon may be more than 5 times your body weight. more than 5 times your body weight. In some rare instances, tendons can snap In some rare instances, tendons can snap or rupture. or rupture. Ruptured tendons can be treated either Ruptured tendons can be treated either surgically or medically depending on the surgically or medically depending on the severity of the rupture. severity of the rupture.

RUPTURED TENDONSRUPTURED TENDONS

The 4 most common areas of tendon rupture The 4 most common areas of tendon rupture are as follows: are as follows:

Quadriceps Quadriceps

Achilles Achilles

Rotator cuff Rotator cuff

Biceps Biceps

Ruptured Tendon SymptomsRuptured 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 TendonRuptured Achilles Tendon

WARNING!WARNING!

THE NEXT SLIDE CONTAINS THE NEXT SLIDE CONTAINS A PHOTO OF A SURGICAL A PHOTO OF A SURGICAL

REPAIRREPAIR

Repair of the Ruptured Achilles Repair of the Ruptured Achilles TendonTendon

Ruptured Extensor TendonRuptured Extensor Tendon

Ruptured Quadriceps TendonRuptured Quadriceps Tendon

RUPTURED PATELLA TENDONRUPTURED PATELLA TENDON

PatellarTendon DisordersPatellarTendon DisordersPatellar Tendonitis (jumper’s knee)Patellar Tendonitis (jumper’s knee)– Inflammation of the patellar tendonInflammation of the patellar tendon

Patella-Femoral SyndromePatella-Femoral Syndrome– Irritation on the underside of the patellaIrritation on the underside of the patella– Can lead to softening or loss of the underside Can lead to softening or loss of the underside

cartilage liningcartilage lining

Osgood-Schlatter DiseaseOsgood-Schlatter Disease– Irritation where the patella tendon inserts on Irritation where the patella tendon inserts on

the tibiathe tibia– Mostly occurs in boys during a growth spurtMostly occurs in boys during a growth spurt

Muscles and body Muscles and body movementmovement

Movement is attained due Movement is attained due to a muscle moving an to a muscle moving an attached boneattached boneMuscles are attached to at Muscles are attached to at least two pointsleast two points– Origin:Origin: attachment to an attachment to an

immoveable boneimmoveable bone– Insertion:Insertion: attachment to attachment to

a movable bonea movable bone

How to describe how muscles are How to describe how muscles are used in motionused in motion

1.1. Prime mover:Prime mover: muscle with the major muscle with the major responsibility for a certain movementresponsibility for a certain movement

2.2. Antagonist:Antagonist: muscle that opposes or muscle that opposes or reverses a prime moverreverses a prime mover

3.3. Synergist:Synergist: muscle that aids a prime muscle that aids a prime mover in a movement and helps prevent mover in a movement and helps prevent rotationrotation

4.4. Fixator:Fixator: stabilizes the origin of a prime stabilizes the origin of a prime movermover