Download THE MUSCULOSKELETAL SYSTEM

THE MUSCULOSKELETAL
SYSTEM
STRUCTURE
AND
FUNCTION
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MUSCLE TISSUE
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Three types of Muscle tissue
 Skeletal muscle
 Cardiac muscle
 Smooth muscle
Muscle fibers are threadlike, cylindrical cells
appearing in bundles with many crosswise
stripes and multiple nuclei
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MICROSCOPIC MUSCLE
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CHARACTERISTICS OF MUSCLE
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Excitability: irritability, the ability to
respond to stimulus such as nerve impulse
Contractibility: fibers stimulated by nerves
contract or shorten
Extensibility: the ability to be stretched or
elongate
Elasticity: allows the muscle to return to its’
original shape
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SKELETAL MUSCLE
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Composed of striated muscle cells and
connective tissue
Attaches to two bones that have a
movable joint, under voluntary control
One of the bones is usually stationary,
called the “origin”
The other bone is usually mobile,called
the muscle’s “Insertion”
Tendons anchor muscles firmly to bones
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TENDONS
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Made of dense, fibrous connective tissue in
the shape of heavy cords
Have great strength
They do not tear or pull away from the bone
easily
Bursae lie between some tendons and the
bones underneath
Bursae makes it easier for a tendon to slide
over a bone
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TENDONS AT WORK
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FUNCTIONS OF SKELETAL MUSCLE
PROVIDE VOLUNTARY MOVEMENT
 MAINTAIN POSTURE OR MUSCLE
TONE
 HEAT AND ENERGY PRODUCTION
 PROTECT INTERNAL ORGANS
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SKELETAL MUSCLE MOVEMENT
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Muscles move bones by pulling on them
The insertion portion of the muscle moves
toward the origin
Muscle contraction is responsible for body
movements
Skeletal muscles contract and become
shorter, while others relax
Muscles Work in coordinated teams, not
singly
This coordinated action makes movement
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smooth and graceful
MUSCLES OF ARM FLEXION
SEE PAGE 186
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MEDICAL TERMS:
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PRIME MOVER: the MUSCLE that is
mainly responsible for producing the
movement
SYNERGISTS: muscles that assist the
prime mover
ANTAGONISTS: muscles that have the
opposing actions
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POSTURE
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Poor posture makes a person tire more
quickly by putting pull on ligaments,joint,
and bones
Poor posture crowds the heart making it
harder to contract
Poor posture crowds the lungs decreasing
breathing capacity
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Muscle Tone
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Muscles are partially contracted at all
times
Muscle tone: state of readiness to act
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FATIGUE
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IF MUSCLE CELLS ARE STIMULATED
REPEATEDLY WITHOUT ADEQUATE REST,
STRENGTH OF MUSCLE CONTRACTION
DECREASES, RESULTING IN FATIGUE
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MUSCLE MOVEMENTS
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FLEXION
EXTENSION
ABDUCTION
ADDUCTION
ROTATION/CIRCUMDUCTION
SUPRINATION/PRONATION
DORSIFLEXION/PLANTAR FLEXION
SEE PAGE 187
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HEAT PRODUCTION
Normal body temperature: 98.6 F
(37 C)
 Muscle Contractions produce most heat
required to maintain temperature
 Hypothermia: failure to maintain normal
body temperature in cold environment
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BODY SYSTEMS AFFECTING
MOVEMENT
Skeletal
Muscular
Respiratory
Circulatory
Nervous
Remember the body is one
large interactive system each
part depending on normal
function of other parts
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TYPES OF SKELETAL MUSCLE
CONTRACTION
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Twitch ..quick, jerky response to stimulus
Tetanic..sustained and steady response
Isontonic ..muscle shortens and produces
movement of joints
Isometric..type contraction where the
muscle does not shorten
see page 176
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TONIC CONTRACTION
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A special type of skeletal muscle
contraction used to maintain posture
Skeletal muscle tone maintains
posture by counteracting the pull of
gravity
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MUSCLE MOVEMENT
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Before skeletal muscle contracts, it must
be stimulated by nerve impulses
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Motor neuron..nerve fiber that stimulates a
muscle fiber
Neuromuscular junction..point of contact
between nerve and muscle
Motor unit..single neuron and the muscle cells
it innervates
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MUSCLE STIMULUS
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Threshold stimulus..minimal level of
stimulation required to cause a fiber to
contract
All or none…subjected to a threshold
stimulus, muscle contracts completely
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SKELETAL MUSCLE GROUPS
Muscles of the Head & Neck
Upper extremity muscles
Muscles of the Trunk
Muscles of the lower extremity
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MUSCLES OF THE HEAD &
NECK
Muscles of facial expression around
eyes, mouth,nose
 Large mastication muscles
 Neck muscles connect skull to trunk,
rotate head and bend neck
 See page 181
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HEAD & NECK MUSCLES
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Facial Expression:
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Frontal raises eyebrows, furrow forehead skin
Orbicularis oculi closes eyes
Orbicularis oris puckers lips to kiss
Zygomaticus elevates corners of mouth & lips
(smiling muscles)
Mastication:
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Masseter elevates mandible
Temporal closes jaw see page 181
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HEAD & NECK MUSCLES
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Neck:
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Sternocleidomastoids flexes ,tilts ,rotates
head
Trapezius elevates shoulders, extends head
backwards
See pages 181
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UPPER EXTREMITY MUSCLES
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Pectoralis major flexes upper arm
Latissinus dorsi extends upper arm
Deltoid abducts upper arm
Biceps brachii primary flexor of forearm
Triceps brachii extensor of elbow (boxer’s
muscle) see page 178-179
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MUSCLES OF THE TRUNK
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ANTERIOLATERAL ABDOMINALS
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External oblique
Internal oblique
Transversus abdominis
Rectus abdominis
RESPIRATORY MUSCLES
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Intercostals
Diaphragm
See page 182
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MUSCLES OF LOWER
EXTREMITIES
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Iliopsoas flexes the thigh or trunk
Gluteus maximus supports torso in
erect position, forms the buttocks,extends
thigh
Adductor muscles adduct or press the
thighs together
Hamstrings flexors of the lower leg
Quadriceps femoris extend lower leg
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MUSCLES OF LOWER
EXTREMITIES
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Tibialis anterior dorsiflexes foot
Gastrocnemius plantar flexes foot
Soleus Plantar flexes the foot
Peroneus group plantar flexes foot
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MUSCLE DISORDERS
MYALGIA… general muscle pain
 MYOSITIS..muscle inflammation
 SPASMS..Sudden, painful involuntary
contraction, cramps due to fluid and
electrolyte imbalance
 STRAIN..Overstretching injury of
muscle or tendon
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MUSCLE DISORDERS
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MUSCULAR DYSTROPHY ..chronic,
progressive muscle atrophy resulting in
disability & early death
POLIOMYELITIS.. A viral infection of the
nerves that control skeletal muscle
RIGOR MORTIS… derived from the Latin,
it means “stiffness of Death
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MUSCLE DISORDERS
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MYASTENIA GRAVIS..chronic condition
where nerve impulses are not properly
transmitted to the muscles.
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Affects respiratory system
Can be fatal
Thought to be autoimmune disease
Progressive muscle weakness, paralysis
No cure, supportive treatment only
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THE END
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