The Muscular System

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The Muscular System

• Chapter 7

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Muscle

• One of the 4 basic tissues of body
• Epithelial, connective, muscle, nervous
• Made up of cells that can shorten or contract
• Three different types of muscle that are all
  controlled or influenced by the nervous system.
• ________________ muscle
• Controlled by conscious mind and moves bones of
  skeleton.
• _________________ muscle
• Found only in heart
• _________________ muscle
• Found throughout body (intestines, lungs, blood
  vessels, etc..) but controlled by unconscious mind

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Basic Terminology

• ________- generally refers to muscle
• Myology, myositis
• ________- refers to muscles at the cellular level
• Sarcoplasm, sarcolemma

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Skeletal Muscle

• Moves the bones of the skeleton
• __________- can be controlled be conscious mind
• __________- microscopically visible striped
  pattern of alternating light and dark bands that
  run the length of a muscle cell. Cells can have
  multiple nuclei.

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Skeletal Muscle Gross Anatomy

• The thick central portion is called the
  ___________.
• Muscles have two attachment sites
• _______________________- the end that is
  generally more stable than the other. Does not
  move when muscle contracts.
• _______________________- site that undergoes most
  of the movement during contraction.
• Most muscles attach to bone via __________.
• Bands of ________ _______connective tissue made
  of collagen fibers

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APONEUROSIS LINEA ALBA

• Some muscles are unique because they attach to
  bone or other muscles by broad sheets of fibrous
  tissue called______________________.
• The most prominent aponeurosis is the ________
  _________
• runs along an animals ventral midline from
  sternum to pubis.
• Connects abdominal muscles from right and left
  sides
• Common site for abdominal surgical incisions

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Muscle Actions

• Skeletal muscles contract when stimulated to do
  so by a nerve impulse.
• Muscles usually work in groups
• An _____________ or prime mover describes a
  muscle or muscle group that directly produces a
  desired movement.
• __________________- a muscle that contracts at
  the same time as a prime mover and assists it in
  carrying out action.
• An _______________ is a muscle or muscle group
  that directly opposes the action of a prime
  mover.
• _____________- stabilizes joints to allow other
  movements to take place.

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Muscle Naming Conventions

• Muscles are generally named by physical
  characteristics
• Action
• Example deep digital flexor
• Shape
• Example deltoid muscle
• Location
• Example biceps brachii
• Direction of Fibers
• Rectus abdominis- rectus means straight
• Number of heads or Divisions
• Example triceps brachii
• Attachment sites
• Sternocephalicus- originates on sternum, inserts
  on head

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Connective Tissue Terminology

• _________________- each individual skeletal
  muscle fiber is surrounded by this delicate
  connective tissue layer.
• Reticular fibers
• _________________- groups of skeletal muscle
  fibers
• _________________- connective tissue that binds
  together fascicles.
• Collagen and reticular fibers
• _________________- fibrous connective tissue that
  surrounds groups of fascicles.
• Collagen fibers

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Microscopic Anatomy of Skeletal Muscle

• Muscle cells (also called fibers)
• Are very large in size
• Have a threadlike or fiberlike shape.
• Usually are multi-nucleated
• Made up of smaller myofibrils composed of
  _______________ (thin) and _____________ (thick)
  filaments
• Contractile proteins
• Network of sarcoplasmic reticulum (similar to
  ER)
• Stores ____________ for muscle contraction

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• ___ band- large dark band made up of myosin
  filaments
• ___ Band- large light band made up of actin
  filamaments
• ____ line- dark band in center of I band, disk
  that is viewed as a line and is attachment site
  for actin filaments.
• ____________- area from one z line to the next z
  line. Basic contracting unit of skeletal muscle.
  When all sarcomeres contract, leads to overall
  muscle fiber shortening.

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Neuromuscular Junction

• Skeletal muscle is under voluntary control
• If nerve supply is interrupted for long period of
  time, muscle will ______________ (shrink down)
• Neuromuscular junctions- sites where the ends of
  motor nerve fibers connect to muscle fibers.
• The nerve is not actually touching the muscle,
  there is a space called the synaptic space or
  cleft between the nerve the muscle

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Neuromuscular Junction

• ____________ ___________- sacs at end of a nerve
  fiber contain neurotransmitter (e.g.,
  acetylcholine)
• _______________- neurotransmitter chemical that
  travels across synapse to activate muscle fiber
• Attaches to receptor on sarcolemma
• __________________- enzyme in the synaptic space
  that removes acetylcholine
• If muscle is to contract again, another impulse
  must be sent

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• Initiation of Muscle Contraction and Relaxation
• Nerve impulse comes down motor nerve fiber,
  reaches neuromuscular junction and acetylcholine
  is released into synaptic space.
• Acetylcholine binds to receptors on surface of
  sarcolemma (cell membrane) of the muscle fiber.
• This starts impulse that travels along sarcolemma
  and through the T tubules to the interior of the
  cell.

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• contd.
• Once impulse reaches sarcoplasmic reticulum it
  causes release of stored calcium ions (Ca) into
  the sarcoplasm (cytoplasm).
• As Calcium diffuses into myofibrils, initiates
  contraction process which is powered by ATP.
• As contraction occurs, Calcium is pumped back out
  of myofibrils which shuts down contraction
  process.
• Both relaxation and contraction requires energy

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Mechanics of Muscle Contraction

• When a muscle fiber is relaxed, actin and myosin
  overlap a little.
• When stimulated _______ ________ (levers on the
  myosin filaments) ratchet back and forth and pull
  the actin filaments on both sides toward center
  of the myosin filaments.
• Sliding of filaments shortens sarcomere, thereby
  causing contraction.

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Motor Unit

• One nerve fiber and all muscle fibers it
  innervates
• Muscles that make small, delicate movements have
  only a few muscle fibers per nerve fiber in each
  motor unit
• Large, powerful muscles may have a hundred or
  more muscle fibers per motor unit

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Characteristics of Muscle Contraction

• _____-____-_____________ principle
• An individual muscle fiber either contracts
  completely when it receives an impulse or not at
  all.
• Movements can vary in strength due to number of
  muscle fibers stimulated.
• small movements only require a few fibers to
  contract, whereas larger, powerful movements
  require more fibers
• Nervous system sends out impulse based on muscle
  _______ - or idea of how many fibers need to be
  stimulated for that particular activity.
• ex shooting a basketball vs. knitting a sweater

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Phases of twitch contraction (contraction of a
single muscle fiber)

• 1. _______________ phase
• Brief pause between nerve stimulus and beginning
  of actual contraction (lasts about 0.01 seconds)
• 2. ________________ phase
• Actual contraction is taking place (lasts about
  0.04 seconds)
• 3. ________________ phase
• When cells go back to a relaxed state (lasts
  about 0.05 seconds)
• Some fibers are relaxing while others contract,
  so smooth muscle contractions can occur

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Chemistry of Muscle Contraction

• _______ is the energy source for actin and myosin
  to contract.
• Produced by the many _____________.
• ATP that has become ADP can recharge back to ATP
  when creatine phosphate (CP) splits and donates
  a phosphate.
• Glucose and oxygen are also needed for
  contraction.
• Stored in form of glycogen and myoglobin for
  aerobic metabolism.
• Anaerobic metabolism produces __________ acid

Heat Production

• Muscular activity is one of the major
  heat-generating mechanisms that the body uses to
  maintain its temperature.
• Shivering (small spasms of contraction) helps to
  prevent hypothermia

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Cardiac Muscle

• Also known as ______________ due to lack of
  conscious control ________________ and
  _______________ due to microscopic appearance
• Contain myofibrils
• Only found within the heart (walls)
• Much smaller than skeletal muscles cells and only
  contain one nuclei per cell
• Are longer than wide and have multiple branches
  forming a network of cells.
• Contain _________ _________- gap junctions where
  cells attach one to another.
• Transmit impulses from cell to cell.
• This allows entire groups of cells to contract
  together at the same time.
• Dark, transverse

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Physiology of Cardiac Muscle

• No external nerve stimulation required to
  contract.
• Rate and rhythm of contraction is due to (SA
  node) _______ ______ (pacemaker) of heart located
  in the wall of the right atrium.
• Impulse follows a controlled path through the
  conduction system of the heart.
• Groups of cardiac muscle cells that touch adopt
  the contraction rate of the most rapid cell.
• Cardiac cells contract in rapid, wavelike fashion
  down a controlled path.
• This helps to squeeze blood out of chambers of
  the heart

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Nerve Supply of Heart

• Heart rate is modified by Autonomic Nervous
  System
• Sympathetic and Parasympathetic Nervous Systems
• _____________ fibers stimulate heart to beat
  harder and faster as part of "fight or flight
  response
• _____________ fibers inhibit cardiac function,
  causing heart to beat more slowly and with less
  force, part of feed or breed response.

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Smooth Muscle

• Also known as ______________ due to lack of
  conscious control and _______________ due to
  lack of striations.
• Found in two forms
• _________________ smooth muscle
• Large sheets of cells in the walls of some hollow
  organs
• _________________ smooth muscle
• Small, discrete groups of cells make delicate
  movements.

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Smooth microscopic muscle anatomy

• Small with single nucleus.
• Actin and myosin are present, but are not
  arranged in parallel.
• criss-cross cell and are attached to __________
  bodies that are similar to Z lines of skeletal
  muscle.
• Cell balls up as it contracts

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Visceral Smooth Muscle

• Found in walls of many soft internal organs that
  are known as viscera.
• Uterus, bladder, intestines, stomach
• Instead of fine movements, work in waves of
  motion.
• Does not need external stimulation.
• If stretched, will contract more strongly.
• __________ nervous system decreases activity,
  __________ nervous system increases activity

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Multiunit Smooth Muscle

• Individual cells or small groups of cells that
  produce fine and delicate movements
• Ex blood vessel walls, within the eye, small
  airways
• Also under influence of the autonomic nervous
  system

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• CUTANEOUS MUSCLES
• Muscle in the connective tissue beneath the skin
• Little or no attachment to bone
• Thin, broad, and superficial
• Serves to twitch the skin
• Cutaneous trunci

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• HEAD control facial expressions, enable chewing,
  move sensory structures
• Masseter
• NECK support head, allow neck to flex, extend,
  and move head laterally
• Splenius
• Trapezius
• Brachiocephalicus (we will call this muscle the
  Clavotrapezius and Clavodeltoid/Clavobrachialis
  in dissection
• Sternocephalicus (Sternomastoid and Sternohyoid)

HEAD AND NECK MUSCLES
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• ABDOMINAL MUSCLES
• Support the abdominal organs
• Flex/arch the back
• Allow straining for defecation, urination,
  parturition, vomiting, regurgitation
• Assist in respiration
• Arranged in layers from superficial to deep
• External abdominal oblique
• Internal abdominal oblique
• Rectus abdominis
• Transversus abdominis
• Each side of 4 muscles comes together at linea
  alba

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• THORACIC LIMB MUSCLES
• Function in locomotion
• Shoulder region
• Latissimus dorsi
• Pectorals
• Deltoid
• Arm
• Brachialis
• Biceps brachii
• Triceps brachii

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• PELVIC LIMB MUSCLES
• Function in locomotion
• Thigh region
• Gluteals
• Hamstrings
• Biceps femoris
• Semimembranosus
• Semitendinosus
• Quadriceps femoris
• Rectus femoris
• Vastus lateralis
• Vastus medialis
• Vastus intermedius
• Leg
• Gastrocnemius

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• MUSCLE OF RESPIRATION
• Increase and decrease the size of the thoracic
  cavity to bring air into and out of the lungs
• Inspiratory muscles
• Diaphragm
• External intercostals
• Expiratory muscles
• Internal intercostals