UNIT 5

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UNIT 5 MUSCULAR SYSTEM
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MUSCLE TYPES

• Cardiac muscle found only in the heart,
  striated, involuntary, arranged in figure-8
  shaped bundles (for contraction), intercalated
  disks
• Smooth muscle visceral (hollow organs),
  non-striated, involuntary, arranged in sheets or
  layers (contract change shape of organ)
• Skeletal muscle where muscle connects to bone
  for movement, striated, voluntary

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SKELETAL MUSCLE ANATOMY

• Endomysium delicate connective tissue sheeth
  that encloses each muscle fiber
• Fasciculus bundle of muscle fibers covered by
  perimysium (coarser fibrous membrane)
• Epimysium covers bundle of fasciculi (entire
  muscle) blends into either
• Tendon cord of dense, fibrous tissue attaching
  a muscle to a bone
• Aponeurosis fibrous or membranous sheet
  connecting a muscle and the part is moves
  (usually found on torso)

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MUSCLE FUNCTIONS

• Produce movement
• Maintains posture
• Stabilizes joints
• Generates heat

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MICROSCOPIC ANATOMY OF SKELETAL MUSCLE

• Sarcolemma plasma membrane of muscle fiber
  (cell) under the endomysium
• Peripheral nuclei nuclei are pushed aside by
  long ribbon-like organelles called myofibrils
  contain trains of tiny contractile units called
  sarcomeres
• 2 types of myofilaments in the sarcomeres
• 1. myosin filaments thick
• 2. actin filaments thin
• Their arrangement produces a banding pattern, or
  striations

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SKELETAL MUSCLE ACTIVITY

• Stimulation and contraction of single skeletal
  muscle cells
• Irritability the ability to receive and respond
  to a stimulus
• Contractility the ability to shorten (forcibly)
  when an adequate stimulus is received
• Nerve stimulus and action potential one motor
  neuron may stimulate a few muscle cells or
  hundreds of them, depending on the particular
  muscle and the work it does (gross motor vs. fine
  motor)
• Motor unit one neuron and all the skeletal
  muscle cells it stimulates
• Neuromuscular junction where the axon terminals
  for junctions with the sarcolemma
• When the nerve impulse reaches the axon
  terminals, a neurotransmitter is released, which
  travels across the synaptic cleft (gap between
  nerve muscle) acetylcholine (Ach)
  neurotransmitter that stimulates skeletal muscle
• Ach attaches to receptors which makes the
  membrane more permeable to Na
• Na diffuses in and K rushes out, generating an
  action potential (electrical impulse), which
  travels over the entire surface of the sarcolemma
• Muscle cell contracts
• ACH is removed by acetylcholinesterase to stop
  contraction

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SKELETAL MUSCLE ACTIVITY

• steps of the action potential
• Mechanism of muscle contraction Sliding Filament
  Theory
• AP travels down T-tubules, which causes Ca2 to
  be released from the lateral sacs of the
  sarcoplasmic reticulum
• Ca2 binds to tropinin, causing tropomyosin to
  move out of the way exposing the active site on
  the actin filament
• Myosin heads swing back and attach to the active
  site on actin, forming cross-bridges
• Myosin heads perform a power stroke move toward
  the center of the sarcomere
• Pulling actin filaments towards the center of the
  sarcomere
• ATP is broken down to provide energy for the
  myosin heads to release the active site leftover
  energy is stored for the next power stroke
• Myosin heads grab further further back each
  time
• Whole muscle shortens
• Whole series of events takes few thousands of a
  second

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SKELETAL MUSCLE ACTIVITY

• muscle contraction video
• Contraction of skeletal muscle as a whole
• Graded responses
• All-or-none law a muscle cell will contract to
  its fullest extent when it is stimulated
  adequately it never partially contracts is true
  of muscle cells only (not whole muscle)
• Muscle cells react to stimuli with graded
  responses or different degrees of shortening
• Can be produced 2 ways
• 1. By changing frequency of muscle stimulation
• A single, brief, jerky contraction muscle
  twitch
• Nerve impulses are delivered to the muscle at a
  very rapid rate, so rapid that muscle does not
  get a chance to relax completely between stimuli
  as a result, the effects of the successive
  contractions are summed (added) together and
  contraction gets stronger and smoother, with no
  evidence to relaxation seen muscle is in fused,
  or complete, tetanus, or tetanic contractions
  (tetanus is normal and desirable, not to be
  confused with tetanus/lockjaw, which is caused by
  bacterium)

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SKELETAL MUSCLE ACTIVITY (CONT.)

• 2. by changing number of muscle cells being
  stimulated
• How forcefully a muscle contracts depends largely
  on the number of muscle cells stimulated when
  only a few cells are stimulated, contractions
  will be slight when all cells are stimulated,
  contraction is strong
• Providing energy for muscle contraction as
  muscle contracts, ATP is broken down for energy
  muscles stre a limited supply (4-6 seconds
  worth), so it must be regenerated continuously.
  Working muscles use 3 pathways for ATP
  regeneration
• 1. Direct phosphorylation of ADP by creatine
  phosphate a phosphate group transfers from CP to
  ADP, regenerating more ATP CP supplies exhaust
  in about 20 seconds
• 2. Aerobic respiration provides 95 of ATP at
  rest and during light exercise occurs in
  mitochondria involves a series of metabolic
  pathways that use oxygen called oxidative
  phosphorylation glucose is broken down into CO2
  H2O some released energy is captured in ATP
  bonds (get 36ATP/1 glucose)
• 3. Anaerobic glycolysis and lactic acid
  formation initial steps of glucose breakdown
  occur via glycolysis which is anaerobic.
• Glucose ? pyruvic acid with energy captured in
  ATP bonds (2ATP/ 1 glucose)

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SKELETAL MUSCLE ACTIVITY (CONT.)

• If enough oxygen is present, pyruvic acid enters
  aerobic pathways that occur within mitochondria
• If there is not enough oxygen present (i.e.
  intense muscle activity), or if oxygen or glucose
  delivery is inadequate, pyruvic acid is converted
  to lactic acid in a process called anaerobic
  glycolysis
• Lactic acid - causes muscle soreness and fatigue
  (muscle fatigue occurs when the muscle can no
  longer contract despite still being stimulated).
  It results from oxygen debt which must be paid
  back (taking deep breaths)
• Isotonic vs. isometric contraction
• Isotonic contractions when myofilaments are
  successful in sliding movements so muscle
  shortens during contraction most familiar type
  (i.e. smiling, bending at knee)
• Isometric contractions when muscles do not
  shorten b/c muscles are pitted against some more
  or less immovable object, but tension keeps
  building (i.e. lifting a dresser, pushing arms
  against a wall)
• Muscle tone state of continuous partial
  contraction

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SKELETAL MUSCLE ACTIVITY (CONT.)

• Effect of Exercise on Muscles
• Aerobic or endurance exercise
• Examples biking, jogging, swimming laps
• Results in stronger more flexible muscles with
  greater resistance to fatigue
• blood supply increases
• individual muscle cells form more mitochondria
  and store more oxygen (makes overall body
  metabolism more efficient
• Improves digestion and elimination of wastes
• Enhances neuromuscular coordination
• Makes the skeleton stronger
• Heart enlarges
• Fat deposits are cleared from blood vessel walls
• Lungs become more efficient at gas exchange
• Does NOT cause muscles to increase in size

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SKELETAL MUSCLE ACTIVITY (CONT.)

• Effects of Exercise on Muscles
• Resistance or isometric exercise
• Examples weightlifting, theraband or medicine
  ball training, bodyweight exercises like push-ups
  or pull-ups, plyometrics
• Key is that muscles are being forced to contract
  with as much force as possible or as quickly as
  possible
• Muscles increase in size and strength
• Due to enlargement of individual muscle cells
  (more contractile filaments), not because more
  muscle fibers are made
• Size of reinforcing connective tissue also
  increases to support increased muscle size

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SKELETAL MUSCLE ACTIVITY (CONT.)

• Attached Parts of a Muscle
• Origin part of the muscle attached to the
  immovable or less movable bone
• Insertion part attached to the movable bone
  insertion moves toward the origin
• Types of Muscle Movement
• Flexion decrease angle of a joint (hinge joints
  knee elbow)
• Extension increases angle of a joint
  (straighten knee or elbow)
• Rotation movement of a bone around its
  longitudinal axis (ball socket joints shaking
  your head no)

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SKELETAL MUSCLE ACTIVITY (CONT.)

• Abduction moving a limb away from the midline
  (raising arm or leg out to the side)
• Adduction moving a limb toward the midline
  (lowering arm or leg from the side back down to
  the body)
• Circumduction proximal end of a limb is
  stationary, distal end moves in a circle,
  combination of flexion, extension, abduction,
  adduction)
• Dorsiflexion lifting the foot so that its
  superior surface approaches the shin
• Plantar flexion depressing the toes (point the
  foot)

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SKELETAL MUSCLE ACTIVITY (CONT.)

• Inversion turn the sole medially (most common
  type of ankle sprain)
• Eversion turn the sole laterally
• Supination forearm rotates laterally so palm
  faces anteriorly radius ulna are parallel
• Pronation forearm rotates medially so palm
  faces posteriorly radius ulna form an X
• Opposition movement of thumb when touching tips
  of other fingers on same hand

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INTERACTIONS OF SKELETAL MUSCLES IN THE BODY

• Prime mover muscle that has the major
  responsibility for causing a particular movement
• Antagonist muscles that oppose or reverse a
  movement
• Synergists help prime movers by producing same
  movements
• Fixators hold a bone still or stabilize the
  origin of a prime mover so all the tension can be
  used to move the insertion bone (i.e. postural
  muscles that stabilize the vertebrae)

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NAMING SKELETAL MUSCLES

• Direction of the muscle fibers usually a
  reference to a midline or long axis of a limb
  (i.e. rectus straight oblique at a slant
  to)
• Relative size of the muscle maximus, minimus,
  longus
• Location of the muscle named for bone
  associated with the muscle (i.e. temporalis,
  tibialis)
• Number of origins biceps brachii, triceps
  brachii
• Location of muscles origin insertion
  sternocleidomastoid (originates on sternum
  clavicle, inserts on mastoid process of temporal
  bone)
• Shape of the muscle deltoid means triangular
• Action of the muscle flexor, extensor,
  adductor, etc.
• website tutorial

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ARRANGEMENT OF FASCICLES

• Circular concentric circles around outside body
  opening (sphincters eye mouth)
• Convergent fascicles converge to single tendon
  (pectoralis major)
• Parallel length of fascicle runs parallel to
  long axis of muscle
• Fusiform spindle-shaped muscle with expanded
  belly (biceps brachii)
• Pinnate short fascicles attach obliquely to
  central tendon (uni-, bi-, or mulit-)

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GROSS ANATOMY OF SKELETAL MUSCLES

• Practical 1 head neck
• Facial Muscles
• Frontalis
• Orbicularis oculi
• Orbicularis oris
• Buccinator
• Zygomaticus
• Chewing Muscles
• Masseter
• Temporalis
• Neck Muscles
• Platysma
• Sternocleidomastoid

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GROSS ANATOMY OF SKELETAL MUSCLES

• Practical 2 trunk muscles
• Anterior
• Pectoralis major
• Intercostals (internal external)
• Muscles of the abdominal girdle
• Rectus abdominus
• External oblique
• Internal oblique
• Transversus abdominus

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GROSS ANATOMY OF SKELETAL MUSCLES

• Practical 2 trunk muscles
• Posterior
• Trapezius
• Latissimus dorsi
• Erector spinae
• Deltoid

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GROSS ANATOMY OF SKELETAL MUSCLES
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GROSS ANATOMY OF SKELETAL MUSCLES
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GROSS ANATOMY OF SKELETAL MUSCLES
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GROSS ANATOMY OF SKELETAL MUSCLES
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GROSS ANATOMY OF SKELETAL MUSCLES
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GROSS ANATOMY OF SKELETAL MUSCLES
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GROSS ANATOMY OF SKELETAL MUSCLES