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MUSCULAR SYSTEM
CHAPTER 6
MUSCLE CELL TYPES
•Skeletal (striated)
•Cardiac
•Smooth (non-striated)
SIMILARITIES AMONG MUSCLE
CELLS
• All elongated
• All called muscle fibers
• All have myofilaments ( muscle’s ability
to contract)
• Prefixes- myo, mys, sarco ( all refer to
muscle)
SKELETAL MUSCLE
SKELETAL MUSCLE
• Attach to the body’s skeleton
• Help form smooth contours of the
body
• Cigar-shaped
• Multinucleated (many nuclei)
• Largest of all muscle fibers
SKELETAL MUSCLE
• Also known as striated muscle
(appear to be striped)
• OR
• Voluntary muscle: only muscle
type to conscious control.
SKELETAL MUSCLE
• Soft and fragile
• But, can exert tremendous power
• Fibers are bound together by
connective tissue.
SKELETAL MUSCLE
• Endomysium- connective tissue sheath
that encloses muscle fibers.
• Perimysium- coarse fibrous membrane
that encloses several sheathed fibers.
• Fascicle- bundle of fibers.
SKELETAL MUSCLE
• Epimysium- tough overcoat of
connective tissue around many fascicles.
• Cover entire muscle
• Tendons(cord-like)- attach muscles
directly to bones.
• Aponeuroses(sheet-like-) attach muscles
directly to bones.
TENDONS
• Attach muscle to bones.
• Provide durability
• Conserve space
• Made of tough collagenic fibers
SMOOTH MUSCLE
SMOOTH MUSCLE
• Contains no striations.
• Involuntary muscle – we cannot
consciously control it.
• Found mainly in the walls of hollow visceral
organs.
• Stomach, bladder, respiratory passages
SMOOTH MUSCLE
• Propels substances along a definite track or
pathway.
• Using terms like visceral, nonstraited, involuntary
• Spindle shaped
• Single nuclei
• Arranged in sheets or layers
SMOOTH MUSCLE
• Two layers- one running circularly and the
other longitudionally
• As the layers relax and contract they change
the shape and size of the organ.
CARDIAC MUSCLE
CARDIAC MUSCLE
• Only found in the heart.
• Striated, but involuntary
• Cushioned by small amounts of soft connective
tissue
• Arranged in spiral/figure 8 bundles
• Branching cells joined by junctions called
intercalated discs
MUSCLE FUNCTIONS
•1. produce movement
•2. maintains posture
•3. stabilizes joints
•4. generates heat
MUSCLE FUNCTIONS- PRODUCING
MOVEMENT
• Skeletal- mobility of the body
• Cardiac- pump in heart to circulate blood
• Smooth- push fluid and substances along
their designated path.
MUSCLE FUNCTIONS- MAINTAINS
POSTURE
• Function continuously so we can
maintain an erect or seated
posture.
MUSCLE FUNCTIONS- GENERATING
HEAT
• Body heat is a by-product of
muscle activity.
• Heat is vital in maintaining normal
body temperature.
MUSCLE FUNCTIONS- STABILIZING
JOINTS
• As they pull on bones to cause movement they
stabilize joints.
• Tendons important in shoulder joint.
MICROSCOPIC ANATOMY OF
SKELETAL MUSCLE
ANATOMY
• Sarcolemma – plasma membrane
• Myofibrils- long ribbon-like organelles that push
nuclei to sides and nearly fill the whole
cytoplasm.
• Chains of tiny contractile units called sarcomeres
• Sarcomeres-aligned like boxcars in a train
• Striped appearance comes from light (I) and
dark (A) bands along the muscle.
• Sarcoplasmic reticulum- specialized smooth ER
• Stores calcium and releases it on demand
2 TYPES OF MYOFILAMENTS
• Thick filaments (made of protein myosin)
• Cross bridges- link thick and thin filaments
together during contraction.
• Thin filaments (made of protein actin)
ANATOMY OF SKELETAL MUSCLE
SKELETAL MUSCLE ACTIVITY
ACTIVITY
• Irritability- ability to receive and respond
to stimulus
• Contractibility- ability to shorten (forcibly)
when adequate stimulus is received.
MUSCLE RESPONSE TO INCREASINGLY
RAPID STIMULATION
• Muscle twitching- single, brief, jerky
contractions.
• Not the way our muscles normally
operate
• Most types of muscular activity- nerve
impulses are delivered to the muscle so
rapidly that the cells do not get a
chance to relax completely.
MUSCLE RESPONSE TO STRONGER
STIMULI
• Only a few cells stimulated- contraction
of muscle is slight.
• All muscle cells stimulated- contraction
of muscle is as strong as it can get.
PROVIDING ENERGY FOR MUSCLE
CONTRACTION
• As muscle contracts, the bonds of ATP
molecules are broken.
• Muscles store limited amount of ATP
(only enough to get you going)
• ATP must be regenerated continuously
MUSCLE FATIGUE AND OXYGEN DEBT
• Muscle fatigue: occurs if we exercise our muscles
strenuously for a long time.
• Unable to contract even if it is being stimulated.
• Believed to be a result from oxygen debt
• Oxygen debt occurs during prolonged muscle
activity.
• When muscles lack oxygen- lactic acid builds up
in muscles
TYPES OF MUSCLE CONTRACTIONSISOTONIC
Myofiliments successful in their sliding
movements
Muscle shortens
Movement occurs
Bending the knee
Rotating arms
Smiling
TYPES OF MUSCLE CONTRACTIONSISOMETRIC
• Myosin filaments are “skidding their
wheels”
• Tension of the muscle keeps increasing
• Trying to slide but cannot
• Like when you try to pick up a 400 pound
object
MUSCLE TONE
• Even when muscle is voluntarily relaxed- some
fibers are contracting
• Muscle remains firm, healthy , and constantly
ready for action.
• Muscle tone- state of continuous partial
contraction
EFFECT OF EXERCISE ON MUSCLES
• If you don’t use muscle, you lose it.
• Regular exercise increases muscle size, strength,
and endurance.
• Aerobic- (endurance)- jogging, biking, aerobics
class
• Result in stronger, more flexible muscle
• Makes overall body metabolism more efficient
• Improves digestion
• Enhances neuromuscular coordination
• Makes skeleton stronger
TYPES OF BODY MOVEMENTS
• 600 skeletal muscles- attached to a bone or
other connective tissue structure.
• Origin- attached to the immovable or less
movable bone.
• Insertion- attached to the movable bone
• When the muscle contracts the insertion
moves toward the origin.
TYPES OF BODY MOVEMENTS
• Flexion- saggital plane- decreased anglebrings two bones together.
• Bending knee
• Bending elbow
• Bending forward at the hip
TYPES OF BODY MOVEMENTS
• Extension- opposite of flexion- increases the
angle or distance between two bones.
• straightening knee/ straightening elbow
• If angle is over 180 degrees- hyperextension
• Tip head posteriorly so chin points to ceiling.
TYPES OF BODY MOVEMENTS
• Rotation- movement of a bone over its
longitudinal axis.
• Common in ball-and-socket joints
• Shaking your head no
TYPES OF BODY MOVEMENTS
• Abduction- moving a limb away from the
midline of the body.
TYPES OF BODY MOVEMENTS
• Adduction- opposite of abduction- movement
of limb toward the body midline.
TYPES OF BODY MOVEMENTS
• Circumduction- combination of flexion,
extension, abduction, and adduction
• Commonly ball-and-socket joint (shoulder)
• Proximal end is stationary and distal end moves in a
circle
TYPES OF BODY MOVEMENTS
• Dorsiflexion and plantar flexion- up and down
movements of the foot and ankle.
TYPES OF BODY MOVEMENTS
• Inversion and eversion- pertaining to the foot
• Inversion- turn sole medially
• Eversion- turn sole laterally
TYPES OF BODY MOVEMENTS
• Supination(turning backward) and
pronation(turning forward)
• Refer to movements of the radius around the ulna
TYPES OF BODY MOVEMENTS
• Opposition- saddle joint between metacarpal
1 and carpals allows opposition of the thumb.
TYPES OF MUSCLES
TYPES OF MUSCLES
• Prime mover- muscle that has major
responsibility for causing a particular
movement.
• Antagonists- muscles that oppose or reverse a
movement
• When prime mover is active- antagonist is stretched
and relaxed.
• Antagonists can be prime movers
• Biceps of the arm (prime mover of elbow flexion) is
antagonized by the triceps (a prime mover of elbow
extension)
TYPES OF MUSCLES
• Synergists- help prime movers by:
• Producing the same movement
• Reducing undesirable movements
• Muscle crossing two or more joints- contraction
will cause movement in all joints it touches
unless synergists stabilize them.
• Can make a fist without bending your wrist
TYPES OF MUSCLES
• Fixators- specialized synergists
• Hold bone still
• Stabilize origin of a prime mover so all
tension can be used to move the insertion
bone.
• Postural muscles that stabilize vertebral
column
NAMING SKELETAL MUSCLE
DIRECTION OF MUSCLE FIBERS
• Imaginary line – midline of the body/ long
axis of limb bone
• Rectus (straight)- parallel to that imaginary
line
• Oblique ( slanted) – slanted to imaginary
line
RELATIVE SIZE OF THE MUSCLE
• Maximus- largest
• Minimus- smallest
• Longus- long
LOCATION OF THE MUSCLE
• Some are named for the bone they are
associated with.
• Temporalis and frontalis- lie over temporal
and frontal bones of the skull.
NUMBER OF ORIGINS
• Biceps, triceps, quadriceps- two/ three/ or
four origins.
LOCATION OF THE MUSCLE’S ORIGIN
AND INSERTION
• Sometimes they are named for their
attachment sites.
• sternocleidomastoid muscle: origins on
• Sternum (sterno)
• Clavicle (cleido)
• Mastoid process ( of temporal bone)
SHAPE OF THE MUSCLE
• Named for their shape
• Deltoid muscle – triangular
ACTION OF THE MUSCLE
• When muscles are named for their
actions- the following words may
appear
• Flexor, extensor, adductor
• Adductor muscles of the thigh/
extensor muscles of the wrist.
GROSS ANATOMY OF
SKELETAL MUSCLES
HEAD AND NECK MUSCLES
Facial Muscles
•
•
•
•
•
Frontalis
Oribicularis Oculi
Oribicularis Oris
Buccinator
Zygomaticus
Chewing Muscles
• Masseter
• Temporalis
Neck Muscles
Trapezius
Cranial aperneurosis
occipitalis
• Platysma
• Sternocleidomastoid
FACIAL MUSCLES
• Frontalis- covers frontal bone
• Allows you to raise your eyebrows
• Allows you to wrinkle your forehead
• Orbicularis Oculi- circles around the eyes
• Allows you to close your eyes, squint, blink, and wink
• Orbicularis Oris- circular muscle of lips
• Kissing muscle
• Closes the mouth and protrudes the lips
FACIAL MUSCLES
• Buccinator: runs across the cheek and inserts into
the orbicularis oris.
• Flatten cheek in whistling or blowing
• Also used as a chewing muscle
• Zygomaticus: extends from corner of mouth to
cheekbone.
• Smiling muscle- because it raises corners of the mouth
upwards.
CHEWING MUSCLES
• Masseter- covers lower jaw as it runs from the
zygomatic process of the temporal bone to the
mandible.
• Closes the jaw by elevating the mandible
• Temporalis- fan-shaped / covers temporal bone
• Inserts into the mandible
• Acts as a synergist of the masseter in closing the jaw
NECK MUSCLES
• Platysma- single sheet-like muscle that covers the
anterolateral neck
• Acts to pull the corners of the mouth inferiorly
• Produces a downward sag of the mouth
• Sternocleidomastoid- paired muscles- one on each
side of the neck.
TRUNK MUSCLES
Anterior Muscles
• Pectoralis Major
• Intercostal Muscles
• Mucles of the Abdominal Girdle
• Rectus Abdominus
• External Oblique
Posterior
Muscles
• Internal Oblique
• Trapezius
• Transverse Abdominus
• Latissimus Dorsi
• Erector Spinae
• Deltoid
ANTERIOR MUSCLES
• Pectoralis Major- large fan-shaped muscle covering
the upper part of the chest.
• Origin from the shoulder girdle and the first 6 ribs
• Acts to adduct and flex the arm
• Intercostal Muscles- deep muscles found between
the ribs
• Important in breathing because they help raise the rib cage
for breathing air in.
• Internal intercostals – depress the rib cage to move air out
• When you exhale forcibly
ANTERIOR MUSCLES
• Muscles of the Abdominal Girdle- anterior
abdominal muscles
• Includes: rectus abdominus, external and internal obliques,
and transversus abdominus
• Reinforces the body trunk
• Form a thick wall
• Rectus abdominus- run from pubis to rib cage/ main
function is to flex the vertebral column
• External oblique- make up lateral walls of abdomen/ run
from last 4 pairs of ribs to illium/ flex the vertebral column
and rotate the trunk.
• Internal oblique- from iliac crest and insert into the last
three ribs
• Transversus abdominus- deepest muscle of the
abdomen wall/ compresses the abdominal contents.
POSTERIOR MUSCLES
• Trapezius- runs from occipital bone down vertebral
column to the end of the thoracic vertebrae.
• Then they flare laterally and insert into the scapular spine
and calvicle.
• Extend the head
• Elevate,depress, adduct, and stabilize the scapula.
• Latissimus Dorsi- large, flat muscle pair- covers lower
back
• Lower spine and illium to proximal end of humerus
• Extends and adducts the humerus
• Important when swimming or striking a blow
POSTERIOR MUSCLES
• Erector spinae- prime mover of back extension
• Deep muscles of the back
• Back erectors
• Provide resistance that helps control the action of bending over
at the waist.
• Common source of lower back pain.
• Deltoid- fleshy, triangular shaped, form rounded shape of
your shoulders.
• Spine of scapula to clavicle
• Inserts into proximal end of humerus
• Prime movers of arm abduction
UPPER LIMB MUSCLES
• Biceps Brachii
• Brachialis
• Brachioradialis
• Triceps Brachii
UPPER LIMB MUSCLES
• Biceps Brachii- most familiar muscle of the arm
• Bulges when elbow is flexed
• Originates from shoulder girdle and inserts to radial
tuberosity.
• Brachialis- lies deep in biceps brachii
• Important in elbow flexion
• Brachioradialis- flairy, weak, arises in humerusinserts into forearm
• Resides mainly in forearm
• Triceps Brachii- only muscle fleshing out posterior
humerus
• Inserts into olecranon process of ulna
LOWER LIMB MUSCLES
• Cause movement at hip, knee, and foot joints
• Largest, strongest muscles
• Specialized for walking and balancing the body
• Pelvic girdle- heavy fused bones- no special
group of muscles for it
• Different from shoulder girdle
LOWER LIMB MUSCLES
• Span two joints
• Can cause movement at both joints
• Thigh- massive muscles that hold body upright.
• Thigh muscles cross knee and cause its flexion
and extension
HIP JOINT MUSCLE
• Gluteus maximus
• Gluteus medius
• Iliopsoas
• Adductor muscles
HIP JOINT MUSCLE
• Gluteus maximus- forms most of the flesh of the
buttock
• Powerful hip extensor
• Brings thigh in a straight line with pelvis
• Most important when climbing stairs and when
jumping
• Originates from sacrum and iliac bones and runs to
insert on the gluteal tuberosity of femur
HIP JOINT MUSCLE
• Gluteus medius- runs from ilium to femur
• Beneath gluteus maximus
• Hip abductor
• Important site for giving intramuscular injections
• Iliopsoas- fused muscle composed of two muscles
(iliacus and psoas major)
• Prime mover of hip flexion
• Runs from iliac bone and lower vertebrae deep
inside pelvis to insert on lesser tronchanter
• Keeps upper body from falling backward when we
are standing up
HIP JOINT MUSCLE
• Adductor muscles-form muscle mass at medial
side of each thigh.
• Press thighs together
• Tend to become flabby very easily
• Origin on pelvis and insert on proximal aspect of
femur
MUSCLES CAUSING MOVEMENT AT
THE KNEE JOINT
• Hamstring group
• Biceps femoris
• Semimembranosus
• semitendinosus
• Sartorius
• Quadriceps Group
• Rectus femoris
• Vastus muscles
HAMSTRING GROUP
• Muscles forming the muscle mass of the
posterior thigh.
• Three muscles: biceps femoris,
semimembranosus, and semitendinosus
• All originate on the ischial tuberosity and run
down the thigh to insert of both sides of
proximal tibia.
SARTORIUS
• Thin and strap-like
• Most superficial muscle of the thigh
• Runs obliquely across the thigh from anterior iliac
crest to the medial side of the tibia
• Weak thigh flexor
QUADRICEPS GROUP
• Rectus femoris and three vastus muscles
• Flesh out anterior thigh
• Vastus muscles originate from the femur
• Rectus femoris originates from pelvis
• All four insert into the tibial tuberosity via the patellar
ligament
• Acts to extend knee powerfully
• Flex hip
MUSCLES CAUSING MOVEMENT AT
THE ANKLE AND FOOT
• Tibialis anterior
• Extensor digitorum longus
• Fibularis muscles
• Gastrocnemius
• Soleus
MUSCLES CAUSING MOVEMENT AT
THE ANKLE AND FOOT
• Tibilais anterior- arises from upper tibia and then
parallels the anterior crest as it runs to tarsal
bones
• Acts to dorsiflex and invert the foot
• Extensor digitorium longus- lateral to tibilais anterior
• Prime mover of toe extension
• Dorsiflexor of foot
MUSCLES CAUSING MOVEMENT AT
THE ANKLE AND FOOT
• Fibularis muscles: three – longus, brevis, tertius
• Found in lateral part of the leg
• Plantar flexes and everts the foot
• Gastrocnemius- forms curved calf of posterior leg
• Prime mover of plantar flexion of the foot
• Soleus- deep into gastrocnemius
• Strong plantar flexion of the foot