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The Muscular System
Chapter 8
• One of the 4 basic tissues:
Muscle
• Epithelial, connective, muscle, nervous
• Made up of cells that can shorten by
contracting/flexing
• All muscles are all controlled or
influenced by the _____________
system.
• Skeletal, Cardiac, Smooth
muscle
• See chart for similarities and
differences
Skeletal
Muscle
• ____________- 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 have multiple nuclei.
Skeletal Muscle
Gross Anatomy
• The thick central portion is called the
belly.
• Muscles have two attachment sites:
• _______________________- the end
that is generally more stable
attachment. Does not move when
muscle contracts.
• _______________________- site that
undergoes significant movement during
contraction.
• Most muscles attach to bone via
__________.
• Bands of __________ ___________
connective tissue.
APONEUROSIS
•Some muscles are unique because they
attach to bone or other muscles by a
broad sheet of fibrous tissue called an
APONEUROSIS
•The most prominent aponeurosis is
the __________ __________
•Runs along an animal’s ventral midline
from sternum to pubis.
•Connects abdominal muscles from right
and left sides
•Common site for abdominal surgical
incisions
• 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.
• _____________- stabilize joints to allow other
movements to take place.
Muscle Actions
Muscle Naming Conventions
• Muscles are generally named by physical characteristics:
• Action
• Example: deep digital flexor
• Shape
• Example: trapezius
• 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
CUTANEOUS MUSCLE
• Beneath the skin
• Thin, broad, and superficial
• Serves to twitch the skin
• Cutaneous trunci
HEAD AND NECK MUSCLES
• HEAD: enables chewing
• Masseter
• NECK: support and move head and neck
• Trapezius
• Brachiocephalicus
• Sternocephalicus
ABDOMINAL MUSCLES
• Support the abdominal organs
• Flex/arch the back
• Allow straining for defecation, urination,
parturition, vomiting, regurgitation
• Assist in exhalation
• Arranged in layers from superficial to
deep:
•
•
•
•
External abdominal oblique
Internal abdominal oblique
Rectus abdominis
Transversus abdominis
• The four muscles on each side come
together at the linea alba
THORACIC LIMB MUSCLES
• Function in locomotion
• Shoulder region:
• Latissimus dorsi
• Deltoids
• Pectorals
• Arm:
• Brachialis
• Biceps brachii
• Triceps brachii
PELVIC LIMB MUSCLES
• Function in locomotion
• Thigh region:
• Gluteals
• Hamstrings:
• Biceps femoris
• Semimembranosus
• Semitendinosus
• Quadriceps femoris:
•
•
•
•
Rectus femoris
Vastus lateralis
Vastus medialis
Vastus intermedius
• Lower leg:
• Gastrocnemius
MUSCLES 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
• Abdominal muscles
Fascia
• _________________- each
individual muscle fiber is
surrounded by this delicate
connective tissue layer.
• _________________- groups of
muscle fibers
• _________________- connective
tissue that binds together
individual fibers into fascicles.
• _________________- fibrous
connective tissue that surrounds
groups of fascicles.
Microscopic Anatomy
of Skeletal Muscle
• Skeletal muscle cells (aka fibers)
• Are very large in size
• Have a threadlike shape
• Are multi-nucleated
• Made up of smaller myofibrils which
is where the contractile protein
myofilaments ___________ and
___________ are found
• Have a sarcoplasmic reticulum
(similar to ER)
• Stores ____________ for
muscle contraction
___ band- dark band made up of actin and myosin filaments
___ band- light band made up of only actin filaments
___ line- in center of I band, disk that is attachment site for actin
___ line- in center of A band where all myosin filaments are attached
___ zone- area that only contains myosin filaments
______________- area from one z line to the next z line. Basic contracting
unit of skeletal muscle. When a muscle cell/fiber contracts, all sarcomeres
shorten.
• Initiation of Muscle
Contraction and Relaxation
1. Nerve impulse travels down
neuron (nerve cell), and
acetylcholine (chemical
messenger) is released.
2. Acetylcholine binds to
receptors on surface of
sarcolemma (cell membrane)
of the muscle cell/fiber.
3. Impulse travels along the
sarcolemma and through the
T tubules to the interior of the
cell.
4. Once impulse reaches
sarcoplasmic reticulum, it
causes release of stored Ca2+
ions into the sarcoplasm
(cytoplasm).
5. As calcium diffuses into
myofibrils, it initiates contraction
process which is powered by ATP.
6. After contraction occurs,
calcium is pumped out of
myofibrils (back into S.R.), which
shuts down contraction process.
This also requires ATP.
• Both relaxation and contraction
requires energy
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
(causing more overlap).
• Sliding of filaments shortens
sarcomere, thereby causing
contraction.
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 within an entire muscle.
• 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.
Phases of twitch contraction
(contraction of a single muscle fiber)
• 1. _______________ phase
• Brief pause between nerve stimulus and beginning of
actual contraction
• 2. ________________ phase
• Actual contraction is taking place
• 3. ________________ phase
• Cell is returning to a relaxed state
• Some fibers are relaxing while others contract, so contractions
within an entire muscle are smooth and not jerky.
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 donates its 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
Smooth Muscle
•
______________ & _______________
• Found in two forms:
• _________________ smooth muscle
• Large sheets of cells in the walls of
hollow organs
• _________________ smooth muscle
• Small, discrete groups of cells that
make delicate movements.
Smooth microscopic muscle anatomy
• Small with single nucleus.
• Actin and myosin are present,
but are not arranged in parallel.
• They criss-cross the cell and
are attached to __________
bodies that are similar to Z
lines of skeletal muscle.
• Cell balls up as it contracts
• Found in walls of many internal organs
• Uterus, bladder, intestines, stomach
Visceral
Smooth
Muscle
• Work in waves of motion.
• If stretched, will contract.
• __________________ nervous system
decreases activity
• __________________ nervous system
increases activity
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
Cardiac
Muscle
• _______________ & ________________
• Only found within the heart
• Smaller than skeletal muscles cells and
only contain one nuclei per cell
• Branched
• Contain ________________
_________- gap junctions where cells
attach one to another.
• Transmit impulses from cell to cell.
• This allows entire groups of cells to
contract in a coordinated manner.
• Dark, transverse lines
Physiology of
Cardiac
Muscle
• No external nerve stimulation required to
contract.
• Rate and rhythm of contraction is due to
_____________ ________ (pacemaker).
• Impulse follows a path through the
conduction system of the heart, making
cells contract in rapid, wavelike fashion
down the path.
• This helps to squeeze blood out of
chambers of the heart
• Fight or Flight mode- heart rate and force
of contraction increase
• Feed and Breed mode - heart rate slows
and contracts with less force