Download Muscular System

Muscular System
Key Word Parts
 My/o-, mys-, and sarco- refer to
muscle
 Spas- (draw, pull), tens(stretch), -plegia (paralysis),
therap- (treatment), therm(heat), dynam- (power)
Functions
The human body has more than 600 muscles
The functions of the muscular system
Movement
Maintain Posture
Stabilization of joints
Generation of heat
Protection of some internal organs
Structures
Muscle Fibers -(mean thread like) are long,
slender cells
Fascia - Tough, sheet or band of fibrous
connective tissue that covers, supports and
separates muscle
Tendons - Narrow, band of non-elastic,
dense, fibrous connective tissue that
attaches a muscle to a bone
Aponeurosis- broad, flat sheet of fibrous
connective tissue that is similar to a
tendon; however an aponeurosis attaches a
muscle to bone OR to other tissues
Types of Muscles
Cardiac
Visceral/Smooth
Skeletal
Cardiac
Form walls of heart
Contract to circulate blood
Striated (banded)
Involuntary
Efferent nerves control rate of
contraction
Afferent nerves concerned with
sensations
Contract at steady rate except for
brief bursts of rapid rate,
automaticity
Visceral/smooth
Found in the internal organs of the
body
Walls of hollow, visceral organs
No striations = smooth
Involuntary
Efferent (motor) neurons less
important
Afferent nerves concerned with
sensations of pain, spasm, and
stretch
Steady constant contractions,
automaticity
Skeletal
Attaches to and covers bony skeleton
Longest fibers of all muscle cells
Striated
Voluntary (central and peripheral nervous
system control)
Efferent nerve fibers from brain and
spinal cord send impulses for contraction
Afferent nerve fibers from muscle send
message to CNS to inform brain of the
degree of contraction
Properties
Excitability: ability to
receive & respond to
stimulus
Contractility: ability to
shorten forcibly
Extensibility: ability to
be stretched
Elasticity: ability to
resume resting length
(of muscle fiber) after
being stretched
Automaticity: ability
Contractility
 When muscle
fibers are
stimulated by
nerves they
contract (become
short and thick)
which causes
movement
 Contraction
depends on
myofilaments:
actin and myosin
Muscle Contraction
Isotonic contraction is muscle shortening that
produces movement
Muscle tone or tonus is a state of partial
contraction that maintains a person’s posture
Isometric contraction does not cause muscle
shortening or movement
A twitch is a quick, jerky contraction of a whole
muscle from one stimulus
Muscle Contraction (continued)
Tetanic contraction is more sustained than a
twitch and is caused by many stimuli in rapid
succession
Fibrillation is uncoordinated contraction of
muscle fibers
Convulsions are contractions of groups of
muscles in an abnormal manner
Spasms are involuntary, sudden, and prolonged
contractions
All or None Response
Once the muscle fiber has been stimulated to contract, the
muscle fiber will contract to its fullest extent
Each muscle is served by at least one motor nerve, which
contains hundreds of neuromuscular junctions with each
single muscle fiber
Motor neuron and all the muscle fibers that it supplies is
called a motor unit
When a motor neuron fires, all the muscle fibers that it
innervates respond by contracting
Average 150 muscle fibers per motor unit
Average 4 to several hundred muscle fibers per motor unit
for fine motor control i.e. controlling fingers and eye
movements
Loss of muscle tone
When muscles are not used for a long
period of time: atrophy, waste away
(degeneration and loss of mass)
Complete immobilization - strength
decreases 5% per day; paralysis =
atrophy to ¼ initial size; eventually
muscle tissue replaced by fibrous
connective tissue
Lack of use can result in contracture
Severe tightening of a flexor muscle
Results in bending of a joint
Muscle fatigue
– Muscle unable to contract
– Tension drops to zero
– Inability to generate enough
ATP to power the contractile
process
– Relative deficit of ATP NOT
total absence
– Excessive accumulation of
lactic acid and ionic
imbalances
Other Conditions
Spasm: sudden involuntary
contraction of muscle
Clonic: alternating spasm with
relaxation
Tonic: sustained
Tetanus: smooth sustained
contraction
Tetany: result of low calcium;
increases excitability of neurons; loss
of sensation, muscles twitching,
convulsions; untreated - spasms of
larynx, respiratory paralysis, death
Interactions of Skeletal Muscles
–
–
–
–
Prime Mover/Agonist
Provides major force for producing a specific
movement
Initiates movement
Example: biceps brachii - elbow flexion
Antagonist
Oppose or reverse a particular movement
Example: triceps brachii - elbow extension
Synergist
Aid agonists by promotion of same movement or by
reducing undesirable/unnecessary movements
Example: muscles which help make fist without
bending wrist
Fixator
Synergists which immobilize a bone or a muscle origin
Example: muscles to stabilize scapula
Actions or Movements of Skeletal
Muscles
– Goniometry: measurement of joint movement
– Adduction: moving a body part toward the
midline
– Abduction: moving a body part away from the
midline
– Flexion: decreasing the angle at a joint
– Extension: increasing the angle at a joint
– Hyperextension: increases the angle beyond
the anatomical position
– Circumduction: the distal end of an extremity
inscribes a circle while the shaft inscribes a
cone
Actions or Movements of Skeletal
Muscles
– Rotation: revolving a part about the longitudinal axis
Internal: move toward the midline or medially
External: move away from the midline or laterally
– Supination: turn the palm upward; “what’s up?”
– Pronation: turn the palm downward
– Inversion: turn the plantar surface away from the
midline
– Plantar flexion (extension): move the sole of the foot
downward as in standing on the toes
– Dorsiflexion: move the sole of the foot upward
– Range of Motion – change in joint position produced by
the muscles
Figure 14-5 Basic Types of
Muscle Movement
Muscle Nomenclature
Location i.e. vastus
lateral and vastus
medialis; external
and internal oblique,
pectoralis
Origin and
insertion i.e.
brachioradialis,
occipitofrontal
Function/Action i.e.
ulnar flexor (flexes
wrist), extensor capri
muscles (extension
motions of the wrists)
Muscle Nomenclature
Number of heads/divisions
forming them i.e. biceps, triceps
Size i.e. gluteus maximus
Shape i.e.deltoid
Fiber direction i.e. rectus
abdominus (straight muscle of
abdomen), orbicularis oris (circular
around mouth)
Adjectives to describe muscles
bi-, tri-, quadri: 2, 3, 4
Externus:
exterior
Gracilis: slender
Latissimus:
wide
Longissimus:
long
Longus: long
Medius:
intermediate
Adjectives to describe muscles
Orbicularis: around
Quadratus: square
Rectus: straight
Rhomboideus: diamond shaped
Scalenes: irregular triangle
Teres: round
Transverse: crosswise
Vastus: great
Medical Specialties
Orthopedic Surgeon
Rheumatologist
Neurologist
Sports Medicine
Physical Therapist
Assessment Techniques
Reflex tests
Joint motion
Blood tests
Electromyography tests
Muscle biopsy
Treatment Procedures of the
Muscular System
Medications –
– Anti-inflammatory
– antispasmodics (anticholinergics)
– Muscle relaxants
Physical Therapy
– ROM
– ADLs
Treatment Procedures of the
Muscular System
Fascia (sheet or band of connective
fibrous connective tissue that covers,
supports, and seperates muscles)
– Fasciotomy
– Facioplasty
Muscles
– Myectomy
– Mypoplasty
– Myorrhaphy
Treatment Procedures of the
Muscular System
Tendon
– Carpal tunnel release
– Tenectomy
– Tenodesis
– Tenolysis
– Tenonectomy
– Tenotomy
– Tenoplasty
– Tenorrhaphy
Proud of your Muscles?