Muscular System Flashcards
muscle tissue types
skeletal
cardiac
smooth
muscles = organs → have all four basic tissue types: muscle, nerve, connective, vasculature)
excitability
ability to respond to stimulation from NS
contractility
ability to shorten and pull (bone)
extensibility
ability to contract over different lengths
contraction at rest or while stretched
elasticity
ability to regain original length
characteristics of skeletal muscle
somatic structures = under voluntary control (sympathetic innervation)
innervated by spinal nerves + cranial nerves
contractile organs - attach directly or indirectly onto bones
contraction produces motion of the body
functions of skeletal muscle
produce movement at joints via tendons or muscle fibres
maintain posture + body position
support soft tissues
regulate orifices (sphincters)
maintain body temperature
structure of skeletal muscle
organ → fascicle → fibre → myofibril → sarcomere
(organ → fibre are covered with connective tissue sheath)
muscle covered by epimysium
fascicle covered by perimysium
fibre covered by endomysium
structure of muscle fibre
muscle cell
contains myofibrils, nuclei, mitochondria, sarcoplasm (cytoplasm)
membrane = sarcolemma
myofibrils
surrounded by sarcoplasmic reticulum + t-tubules
contain sarcomeres
sarcomere
basic contractile unit of muscle
intedigitation of thick and thin filaments
boundaries = Z lines (pair)
centre = M line
H band
middle of sarcomere
contains only thick filaments (myosin)
I bands
margin of sarcomere (near Z lines)
contains only thin filaments (actin)
A band
zone of overlap
contains both thin and thick filaments
muscle contraction
depolarization of sarcolemma → spreads through t-tubules
release of Ca2+ from SR = cross-bridging between thick and thin filaments → pivoting of myosin heads towards M line
width of I band + H band decreases
width of A band remains constant
nerve stimulation
each muscle fibre is innervated by a motor neuron
neuron fires → signals fibre to contract
contraction is all or none = fibre either contracts or doesn’t
motor unit
motor neuron + fibres it innervates
(all muscle cells controlled by single motor neuron)
amount of muscle tension depends on number of motor units stimulated
slow twitch fibres
red - lots of mitochondria + myoglobin
narrow diameter
resistant to fatigue = sustained contraction (less powerful)
aerobic metabolism produces ATP
ex. calf: soleus muscle has higher proportion of slow fibres = enlarged in marathon runner
fast twitch fibres
white - less myoglobin
large diameter
rapid contraction → powerful
fatigue easily
anaerobic glycolysis produces ATP
ex. calf: gastrocnemius muscle has higher proportion of fast fibres = enlarged in sprinter
parallel muscles
fascicles run parallel to long axis of muscle
most common muscle type
large force exerted because all fascicles pull in same direction = only one action
ex. rectus abdominus (flat band), biceps brachii (spindle-shaped)
spindle shaped muscle
parallel muscle with tendon at either end
central portion = belly
during contraction → belly widens and muscle shortens
convergent muscles
fan-shaped
fascicles originate over wide area but converge at common attachment site
direction of pull can change by varying which fascicles contract
less force exerted because not all fascicles pull in same direction
ex. pectoralis major, trapezius
circular muscles
fibers are arranged concentrically around opening → form sphincters
contraction reduces diameter of opening
ex. orbicularis oculi (eye) + oris (mouth)
pennate muscles
tendons run through body of muscle
fascicles form oblique angle relative to tendon
contain more muscle fibres than parallel muscle of same size = generate more force
unipennate
muscle fibers are on one side of tendon
single plane pennation
ex. extensor digitorum (forearm)
bipennate
muscle fibres are on both sides of tendon
ex. rectus femoris (thigh)
multipennate
tendon branches with muscle
ex. deltoid
naming: structure/shape of muscle
deltoideus = triangular
maximus = large
brevis = short
naming: specific region
carpi = wrist
abdominis = abdomen
naming: attachment sites
sternocleidomastoideus = sternum, clavicle, mastoid process
naming: in relation to other muscles
profundus = deep
superficialis = superficial
naming: action
flexor = flexion movement
production of movement
muscles:
- attach on individual bones or soft tissue
- usually cross at least one joint
- pull a bone toward another so movement is produced at joint
- stabilize a joint so others can produce movement
agonist
prime mover → major muscle to cause action
contraction produces particular movement
ex. biceps femoris flexes leg at knee joint
synergist
assists prime mover in performing action
ex. semitendinosus (hamstring) also flexes leg at knee joint
antagonist
opposes movement of agonist
ex. quadriceps femoris extends leg at knee joint
lever
rigid structure
moves on fixed point (fulcrum = Fc)
requires force to move a weight
force generated by muscle contraction
first class lever
W - Fc - F
increases range and speed of movement but requires larger force
ex. head: Fc = atlanto occipital joint
(not many examples)
second class lever
Fc - W - F
increases force at expense of range and speed of movement
ex. raising ankles: Fc = foot; F = soleus muscle + achilles tendon
(not many examples)
third class lever
Fc - F - W
increase range and speed of movement at expense of force
ex. flexion of forearm: Fc = elbow; F = biceps brachii (attached to radius)
most common in body
action vs function
ex. gluteus medius and minimus
action = abduction of thigh at hip joint
function = keep pelvis straight during walking
axial musculature
associated with axial skeleton: skull, vertebral column, ribs
innervated by cranial or spinal nerves
attachments on axial skeleton, associated organs, or soft tissue
functions of axial musculature
vision, mastication, facial expression, swallowing
upright posture + movement of back
support of abdominal + pelvic viscera
respiration
urination, defecation, parturition
groups of axial musculature
head + neck
back
thorax + abdominopelvic cavities
pelvis + perineum
extraocular muscles
innervated by oculomotor, trochlear, and abducens nerves (CNs III, IV, VI)
levator palpebrae superioris
superior rectus
medial rectus
inferior rectus
inferior oblique
lateral rectus
superior oblique
CN VI palsy
paralysis of right side lateral rectus = right eye can’t move to the right
muscles of mastication
innervated by trigeminal nerve (CN V) - mandibular division (3)
temporalis
masseter
medial pterygoid
lateral pterygoid
biomechanics of mastication
lateral pterygoid = depressor of mandible to open mouth
- pulls condyle of mandible anteriorly = move down + forward
temporalis (pull up + back), masseter, medial pterygoid (pull up + forward) = elevation of mandible when closing mouth
muscles of facial expression
innervated by facial nerve (CN VII)
orbicularis oculi
orbicularis oris
platysma
occipitofrontalis
buccinator
Bell’s palsy
damage to facial nerve (CN VII)
lesions typically at or beyond stylomastoid foramen = affect all ipsilateral motor branches
ipsilateral upper and lower facial asymmetry = facial paralysis
pharyngeal muscles
innervated by vagus nerve (CN X)
tensor + levator veli palatini
superior constrictor
middle constrictor
inferior constrictor
tongue muscles
innervated by hypoglossal nerve (CN XII)
control position of tongue
palatoglossus
styloglossus
hyoglossus
genioglossus
neck muscles
innervated by cranial or cervical nerves
mylohyoid
digastric (2 bellies)
infrahyoids
sternocleidomastoid
longus capitis
longus colli
scalene muscles
biometrics of swallowing
- contraction of mylohyoid and tongue muscles = floor of mouth tenses + elevation of hyoid bone
- contraction of tensor and levator veli palatini muscles = tense + elevate soft palate to close gap between nose + mouth
- elevation of larynx by many muscles = close airway
- sequential contraction from top of constrictor muscles = push bolus into esophagus
back muscles
transversospinal group
- delicate adjustments at zygapophyseal joints of vertebrae
extensors: (maintain upright posture)
longissimus
spinalis
iliocostalis
erector spinae
trunk muscles
intercostal muscles (3 layers)
abdominal muscles: → can increase intra-abdominal pressure
- rectus abdominis
- external + internal obliques
- transversus abdominis
respiration
contraction of intercostal muscles produces elevation of ribs
increases volume of thoracic cavity
synovial joint in front and back = allows movement of ribs
contraction of diaphragm during inhalation → brings central tendon down to increase vol
diaphragm
separates thoracic + abdominal cavities
chief muscle of respiration
holes for inferior vena cava, esophagus, and aorta
central tendon, muscle fibers, crura
pelvic muscles
coccygeus
levator ani
form the pelvic diaphragm
provide support to pelvic viscera
perineal muscles
innervated by pudendal nerve
external urethral sphincter
external anal sphincter
ischiocavernous
bulbospongiosus
appendicular musculature
associated with appendicular skeleton (limb bones, shoulder + pelvic girdles)
attachment on axial + appendicular skeleton
appendicular musculature - innervation
spinal nerves - form plexuses → branches of nerves leave plexus to innervate muscle compartments
limb muscles are organized into compartments - each is innervated by specific nerve branch of a plexus
upper limb musculature
innervated by branches of brachial plexus (levels C5 to T1)
(exception: trapezius - CN XI)
major muscle groups: shoulder (pectoral girdle), arm, forearm, hand
joints are designed for mobility rather than stability
- positioning pectoral girdle
- moving arm, forearm + hand, hand + digits
muscles moving pectoral girdle
trapezius
levator scapulae
rhomboids
serratus anterior
force couple
muscles work together to complete a task not possible individually
ex. scapular rotation requires trapezius (pulling up near acromion + pulling down near vertebral border) and serratus anterior (protraction)
muscles moving arm at shoulder joint
pectoralis major
deltoideus
latissimus dorsi
rotator cuff muscles:
- subscapularis
- supraspinatus
- infraspinatus
- teres minor
teres major
muscles moving forearm at elbow joint
biceps brachii
brachialis
brachioradialis
triceps brachii
muscles moving hand at wrist joint
flexor carpi radialis
plamaris longus
flexor carpi ulnaris
flexor retinaculum
extensor carpi radialis longus + brevis
extensor carpi ulnaris
muscles moving digits
flexor digitorum superficialis
flexor pollicis longus
flexor digitorum profundus
extensor digitorum + extensor digiti minimi
extensors + abductor for thumb
3 palmar interossei
4 lumbricals
4 dorsal interossei
thenar muscles:
adductor pollicis
flexor pollicis brevis
opponens pollicis
abductor pollicis brevis
Carpal Tunnel Syndrome
carpal tunnel = 9 flexor muscle tendons, surrounded by carpal bones and flexor retinaculum + median nerve
repetitive motion of flexor tendons can irritate their sheath coverings, leading to swelling and compression of median nerve in carpal tunnel
power vs precision grip
power grip = active contraction of digital flexor muscles in forearm ex. flexor digitorum profundus
more force
precision grip = active contraction of some short muscles found in hand ex. thenar muscles
less force
lower limb musculature
innervated by branches of lumbosacral plexus (levels L2-S3)
major muscle groups: hip (pelvic girdle), thigh, leg, foot
joints are designed for stability (various degrees of mobility)
locomotion, posture, balance
- moving thigh, leg, foot + toes
muscles moving thigh at hip joint
gluteus maximus
lesser gluteals: (stabilization of pelvis)
- gluteus medius
- gluteus minimus
iliopsoas
adductor muscle group
muscles moving leg at knee joint
quadriceps femoris:
- 3 vasti
- rectus femoris
sartorius
hamstring:
- semitendinosus
- semimebranosus
- biceps femoris (long + short heads)
muscles moving foot at ankle joint
gatrocnemius
soleus
calcaneal tendon (Achilles)
2 peroneus (fibularis) muscles
tibialis anterior
muscles moving toes
extensor digitorum longus
extensor hallucis longus
flexor digitorum longus
flexor hallucis longus
flexor digitorum brevis
