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Anatomy and Physiology. The Muscular System Chapter 9 Community Education Mr. Kestner. Introduction. Muscles are throughout body Skeletal muscles In eyes to read Turn pages in book Smooth muscles Pushing blood through vessels Digesting food Transporting urine Cardiac muscle

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Anatomy and physiology

Anatomy and Physiology

The Muscular System

Chapter 9

Community Education

Mr. Kestner


  • Muscles are throughout body

    • Skeletal muscles

      • In eyes to read

      • Turn pages in book

    • Smooth muscles

      • Pushing blood through vessels

      • Digesting food

      • Transporting urine

    • Cardiac muscle

      • Pumping heart


  • Muscles make up about 40% to 50% of body weight

  • Contraction causes movement

  • 3 types of muscle

    • Skeletal

    • Smooth

    • Cardiac

Anatomy and physiology


Cardiac Muscle


Skeletal muscle
Skeletal Muscle

  • When viewed under microscope, appears to have alternating dark and light bands

    • Dark bands (A bands) are made of thick filaments of the protein myosin: thick, therefore appear dark

    • Light bands (I bands) are made of the thin filaments of the protein actin: thin, therefore appear light

    • Z line – a dark staining band found in the central region of the I bands

    • H zone – a darker section in the middle of the A band, where myosin filaments are thickest

    • Sarcomere – area between two adjacent z lines – actual contraction occurs via chemical reaction

Muscle anatomy
Muscle Anatomy

  • Skeletal Muscle

    • Muscle cells wrapped together in a fibrous network

    • Many muscle fibers together make a muscle – akin to strings into a cord, cord into a rope

    • All of the muscle cells or fibers innervated by one motor neuron – called motor unit

    • Excited together, contract together (all or none law)

  • Smooth and Cardiac Muscle

    • Under control of autonomic nervous system

Muscle cell properties
Muscle Cell Properties

  • Excitability

    • Fibers excited by stimulus

      • In body – nerve cell

      • In lab – electrical charge

  • Conductivity

    • Allows response to travel throughout the cell

  • Contractility

    • Response to stimulus

  • Elasticity

    • Allowing muscle cells to return to original shape

Neuroelectric factors
Neuroelectric Factors

  • Greater number of K+ ions inside cell

  • Greater number of Na+ ions outside cell

  • Unequal distribution allows inside cell to be negatively charged

  • Known as resting potential

  • Neurotransmitters release acetylcholine causing Na+ ions to enter cell

  • Causes action potential (cell contraction) and K+ to exit cell

  • Causes Ca++ ions to be released bringing about contraction process of myofilaments (muscle contraction)

Neuroelectric factors2
Neuroelectric Factors

  • Sodium-potassium pump restores resting potential

  • Sodium pumped back outside cell

  • Potassium pumped back inside cell

  • Calcium ions reabsorbed

  • Contraction ceases

  • Actin filaments released from myosin filaments

  • Z lines return further apart

  • During and after contraction

    • If oxygen is present, more ATP molecules created

    • If no oxygen present, lactic acid is built up in muscle cells until oxygen becomes available (causes muscle pain)

Muscle tonicity
Muscle Tonicity

  • Muscle tone

    • A property of muscle in which a steady or constant state of partial contraction is maintained in a muscle

  • Isotonic contraction

    • When lifting weight, muscles become shorter and thicker; tension remains the same

  • Isometric activity

    • Pushing against wall, muscles remain constant length; tension increases

Naming muscles
Naming Muscles

  • According to action

    • Adductor, flexor, extensor

  • According to shape

    • Quadratus, trapezius

  • According to origin and insertion

    • Sternocleidomastoid

  • According to location

    • Frontalis, tibialis, radialis

  • According to their number of divisions

    • Biceps, triceps, quadriceps

  • According to the direction their fibers run

    • Transverse, oblique

Muscle terms
Muscle Terms

  • Origin

    • Fixed attachment of a muscle that serves as a basis for the action

    • Proximal

  • Insertion

    • Moveable attachment, where the effects of contraction are seen

    • Distal

  • Tendon

    • Attaches muscle to bone

  • Aponeurosis

    • Wide, flat tendon (head, foot)

Muscle layers
Muscle Layers

  • Superficial

    • Closest to skin

  • Middle

    • In between two other muscles

  • Deep

    • Closest to center of body (toward the bone)

Muscle movements
Muscle Movements

  • Adduction – moving a body part toward the midline

  • Abduction – moving a body part away from the midline

  • Flexion – decreasing the angle between two bones, or bending a body part

  • Extension – increasing the angle between two bones, or straightening a body part

Anatomy and physiology








Muscles to know 203 217
Muscles to Know (203 – 217)

  • Sternocleidomastoid (SCM) – 208

  • Trapezius – 208

  • Pectoralis Major (Pecs) – 210

  • Deltoid – 210

  • Latissimus Dorsi (Lats) – 210

  • Triceps Brachii (Triceps) – 210

  • Biceps Brachii (Biceps) – 210

  • External Oblique (Obliques) – 213

  • Rectus Abdominus (6-pack) – 213

  • Diaphragm (Breathing Muscle) – 213

  • Gluteus Maximus (Glutes) – 214

  • Biceps Femoris (Hamstrings - part of) – 214

  • Quadriceps Femoris (Quads) – 214

  • Gastrocnemius (Calf) – 217

Muscular disorders
Muscular Disorders

  • Contracture

    • A condition in which a muscle shortens its length in the resting state

    • Commonly occur in individuals who are bedridden for long periods of time and muscles are not properly exercised

    • Can be prevented by keeping the body in proper alignment, shifting positions, and periodically exercising muscles

    • Treated by slow and painful procedure of relengthening and exercising the muscle

Anatomy and physiology


Foot Drop

Muscular disorders1
Muscular Disorders

  • Muscle spasms – or cramps

    • sudden, painful, involuntary muscle contractions

    • Usually occur in legs and feet and may result from overexertion, low electrolyte levels, or poor circulation

    • Gentle pressure and stretching of the muscle are used to relieve the spasm

Muscular disorders2
Muscular Disorders

  • Atrophy

    • Decrease in muscle bulk due to lack of exercise, as when a limb in in a cast for a prolonged period

    • Stimulation of nerves with a mild electric current can keep muscular tissue viable until full muscular activity can return

    • In severe cases, muscle fibers are actually lost and replaced with connective tissue

Muscular disorders3
Muscular Disorders

  • Muscular Dystrophy – a group of inherited diseases that lead to chronic, progressive muscle atrophy

    • Usually appears in early childhood

    • Occurs most often in males

    • Most types result in total disability and early death

    • Although no cure, physical therapy is used to slow progress of disease

Muscular disorders4
Muscular Disorders

  • Myasthenia Gravis – a chronic condition where nerve impulses are not properly transmitted to the muscles

    • Leads to progressive muscular weakness and paralysis

    • Usually begins in facial muscles; if it affects respiratory muscles, can be fatal

    • Caused by abnormal destruction of acetylcholine receptors

    • No cure, treatment is supportive

Muscular disorders5
Muscular Disorders

  • Amyotrophic Lateral Sclerosis (ALS)

    • Also known as Lou Gehrig’s disease

    • Progressive degenerative disease of the motor neurons of the body

    • Affects people in middle age

    • Around 10% is genetically inherited (chromosome 21)

    • begins with muscular weakness & atrophy

    • 1st involves legs, forearm and hands, then spreads to face and other muscles of body

    • Within 2-5 years, loss of control and death

    • No known cure, sometimes known as wasting palsy