Nearly half our weight comes from muscle tissue.There are 650 different muscles in the human body.Muscles give us form and shape.Muscles produce most of our body heat.

MUSCULAR SYSTEM OVERVEIW

“the power system”

TYPES OF MUSCLES

SKELETAL

SMOOTH

CARDIAC

MUSCLE TYPES

Skeletal Muscle• Attached to bone• Striated (striped) appearance• VOLUNTARY• Multinucleated muscle cell bundles

(muscle cells = muscle fibers)• SARCOLEMMA = cell membrane• Contract quickly, fatigue easily, can’t

maintain contraction for long period of time

Smooth Muscle

• Visceral (organ) muscle

• Found in walls of digestive system, uterus and blood vessels

• Cells small and spindle-shaped

• INVOLUNTARY

• Controlled by autonomic nervous system

• Act slowly, do not tire easily, can remain contracted for long time

Cardiac Muscle

• Found only in the heart

• Striated and branched

• Involuntary

• Cells are fused – when one contracts, they all contract

• Involuntary

MAIN FUNCTIONS

Four important roles in body:

1. Responsible for all body movement.

2. Responsible for body form and shape (posture)

3. Stabilize joints

4. Responsible for body heat and maintaining body temperature.

SKELETAL MUSCLE ACTIVITYStimulation and Contraction of Skeletal Muscle

Cells• EXCITEABILITY (IRRITABILITY) – the ability to

respond to certain stimuli by producing impulses.• CONTRACTIBILITY – the ability of a muscle to

reduce the distance between the parts of its contents or the space it surrounds.

SKELETAL MUSCLE ACTIVITY

• MOTOR UNIT – a motor neuron plus all the muscle fibers it stimulates.

• NEUROMUSCULAR JUNCTION – the junction between the motor neuron’s fiber which transmits the impulse – and the muscle cell membrane.

• ACETYLCHOLINE – chemical neurotransmitter, diffuses across the synaptic cleft (carries impulse across synaptic cleft)

• MUSCLE FATIGUE – caused by the accumulation of lactic acid in the muscles.

• OXYGEN DEBT – after exercise, the amount of oxygen needed by the muscle to change lactic acid back to glucose.

• MUSCLE TONE - When muscles are slightly contracted and ready to pull.

• DIAPHRAGM – Dome-shaped muscle that separates the abdominal and thoracic cavities, aids in breathing

Muscle ToneIn order to function, muscles should always be slightly contracted and ready to pull.

Muscle contractions may be isotonic or isometric.

ISOTONIC CONTRACTIONWhen muscles contract and shorten. (Walk, talk, etc.)

ISOMETRIC CONTRACTIONWhen the tension in a muscle increases

but the muscle does not shorten. (exercises such as tensing the abdominal muscles.)

MUSCLE CONTRACTIONS

MUSCULAR SYSTEM

“the power system”

MUSCLE MOVEMENT

1. Muscles move bones by pulling on them.

As a muscle contracts, it pulls the insertion bone closer to the origin bone. Movement occurs at the joint between the origin and the insertion.

2. Groups of muscles usually contract to produce a single movement.

3. When the antagonist muscles contract, they produce a movement opposite to that of the prime movers.

Gross Anatomy of Skeletal MusclesAnterior Surface of Body

FrontalisOrbicularis orisSternocleidomastoidsDeltoidPectoralis majorBiceps brachiiIntercostals musclesRectus abdominusExternal obliqueSartoriusQuadriceps group

Gross Anatomy of Skeletal MusclesPosterior Surface of Body

Occipitallis TrapeziusDeltoidtriceps brachiiLatissimus dorsiGluteus mediusGluteus maximusHamstringsGastrocnemiusSoleus Achilles tendon

Disorders and Related Terminology

• ATROPHY – wasting away of muscle due to lack of use.

• HYPERTROPHY – an increase in the size of the muscle cell.

• STRAIN – tear in the muscle resulting from excessive use. Bleeding inside the muscle can result in pain and swelling. Ice packs will help stop bleeding and reduce swelling.

• MUSCLE SPASM (cramp) – sustained contraction of the muscle, usually because of overuse.

• MYALGIA – muscle pain• TENDONITIS – inflammation of a tendon