Jessie Castro Per. 2 Muscular System

Muscle Coverings

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epimysium: dense irregular CT surrounding entire muscle (outermost)

perimysium: fibrous CT surrounding fascicles

endomysium: fine areolar CT surrounding each muscle fiber (innermost)

Sliding Filament Theory

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action potential generated, which stimulates muscle

Ca2+ released; binds to troponin, shifting the actin filaments, which exposes binding sites

myosin cross bridges attach & detach, pulling actin filaments toward center (requires ATP)

muscle contracts

Ca2+ removed; shifts actin filaments to original position, blocking binding sites

muscle contraction stops

Neurovascular Junction

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AP arrives at axon terminal

voltage-gated calcium channels open, calcium enters motor neuron

ACh neurotransmitter releases into synaptic cleft

ACh diffuses across to ACh receptors on sarcolemma

ACh binding to receptors opens gates, allowing NA+ to enter resulting in

end plate potential

Acetylcholinesterase degrades ACh

Sarcomere

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the smallest contractile unit of muscle fiber

contains A band with half of an I band at each end

align end to end along myofibril

composed of thin actin and thick myosin filaments

3 Types of Muscles and Functions

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Skeletal: attached to bones and allows movement

Cardiac: responsible for the contractility of the heart to pump blood

Smooth: helps with digestion, nutrient collection, excretion of body toxins

Major Functions of Muscular System

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produce movement: responsible for all locomotion/ manipulation

maintain posture/ body position

stabilize joints

generate heat as they contract

Action Potential In Muscle Fiber

DEPOLARIZATION

END PLATE POTENTIAL

REPOLARIZATION

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ACh released from motor neuron binds to ACh receptors on sarcolemma

causes chemically gated ion channels on sarcolemma to open

Na+ diffuses into muscle fiber, some K+ diffuses outward

results in end plate potential (depolarization)

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restoration of resting conditions

Na+ voltage-gated channels close, voltage-gated K+ channels open

refractory period: muscle fiber cannot be stimulated for specific amt. of time until repolarization

completes

Na+ came into cell= pumped back out

K+ flowed out= pumped back into cell

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generation/ propagation of AP

enough change in membrane voltage to reach critical level= volted-gated Na+ channels

large influx of Na+ through channels into cell triggers AP; unstoppable and will lead to muscle contraction

AP spreads across sarcolemma causing depolarization

Disorders

MYOSITIS

CERBAL PALSY

MYASTHENIA GRAVIS

FIBROMYALGIA

MUSCULAR DYSTROPHY

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inflammation of the muscle

causes/risk factors: autoimmune, infection, medication induced

symptoms: muscle weakness, swelling, rash

treatment: medication, antibiotics, reduce inflammation

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spastic paralysis causing muscle weakness

causes/risk factors: brain injury/ abnormality, hypoxia during, premature birth

symptoms: mild to severe, delayed development, muscle tightness

treatment: no cure, medication for symptoms, physical therapy

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muscle pain

causes/risk factors: physical trauma, abnormal pain response, sleep disturbance

symptoms: muscle pain, tender points, joint pain

treatment: physical therapy, exercise regimen, massage

muscle weakness and atrophy

causes/risk factors: genetic, duchenne, becker

symptoms: mental retardation, muscle weakness, eyelid

drooping

treatment: no known cure, physical therapy, medication

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neuromuscular disorder that blocks neurotransmitters

causes/risk factors: autoimmune, age, more common in women

symptoms: muscle weakness, shortness of breath, swallowing/ chewing difficulty

treatment: medication, thymectomy, no known cure

Names Of Skeletal Muscles

HEAD

SHOULDER

NECK

BACK

THORAX

ARM

FOREARM

HIP

PELVIS

THIGH

LEG

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fibularis longus

extensor digitorum longus

tibialis anterior

gastrocnemius

soleus

iliopsoas
pectineus

gluteus Medius
gluteus maximus

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triceps brachii

biceps brachii

brachialis

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pectoralis minor

pectoralis major

serratus anterior

intercostals

rhomboid major
latissimus dorsi

tensor fascia lata

sartorious

adductor longus

gracilis

rectus femoris

vastus lateralis

vastus medialis

adductor mangus

hamstrings: biceps femoris, semitendinosus, semimembranosus

trapezius
deltoid

infraspinatus
teres major

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temporalis

masseter

epicranius, frontal belly (frontalis)

orbicularis oculi

zygomaticus

orbicularis oris

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pronator teres

brachioradioalis

flexor carpi radialis

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extensor carpi radialis longus

flexor/extensor carpi ulnaris

extensor digitorum

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platysma

sternohyoid

sternocleidomastoid

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splenius capitis

splenius cervicis

levator scapulae

rhomboid minor/major