muscular system

4 functions of our muscles

movement, maintain support, joint stability, and generates heat

3 types of muscle tissue

skeletal, cardiac, and smooth

skeletal muscle location

attached to bones by tendons

skeletal muscle shape

long, cylindrical, multinucleated, striations

skeletal muscle regulation of contraction

voluntary

skeletal muscle speed of contraction

slow to fast

smooth muscle location

walls of hollow organs

smooth muscle shape

no striations, spindle-shaped cells, single nucleus

smooth muscle regulation of contraction

involuntary

smooth muscle speed of contraction

very slow

smooth muscle rhythm

in some

skeletal muscle rhythm

none

cardiac muscle location

only in the heart

cardiac muscle shape

striations, single nucleus, intercalated disc, branched shape

cardiac muscle regulation of contraction

involuntary

cardiac muscle speed of contraction

slow

cardiac muscle rhythm

always present

wrapping of the muscle fiber

endomysium

wrapping of the muscle fascicle

perimysium

wrapping of multiple fassicles

epimysium

sarcoplasmic reticulum (SR) storage

claim

i band

light band

a band

dark bands

sarcomere

contractile unit of a muscle fiber

thick filaments

myosin filaments

thin filaments

actin filaments

myosin filament heads

cross bridges

the structure the actin filaments are anchored to at their endpoints

z-disc

region from one endpoint to another endpoint in the actin and myosin filaments

sarcomere

myofibril

chains of sarcomere

bare zone

has no actin filaments

properties of skeletal muscle activity

irritability and contractility

irritability

ability to receive and respond to stimuli

contractility

ability to shorten when an adequate stimuli is received

extensibility

ability to stretch

elasticity

ability to recoil

motor unit

a neuron and all the muscle fibers it stimulates

neuromuscular junction

site where nerve and muscle fibers meet

axonal terminal

the end of the motor neuron that meets in the neuromuscular junction

synaptic cleft

small gap between the muscle and nerve that is filled with interstitial fluid

nuerotransmitter in skeletal muscle

acetylcholine (ACh)

sliding filament theory

cross bridges on the myosin will attach to binding sites on actin filaments to move the filaments together (creating a contraction)

message sent (step 1 of sliding filament theory)

a message comes from the brain and travels through the spinal cord into a neuron which reaches the neuromuscular junction

neurotransmitter (step 2 of sliding filament theory)

acetylcholine is released into the synaptic cleft which then binds to the sarcolemma. this opens the sodium - potassium channels

depolarization (step 3 of sliding filament theory)

Na+ and K+ begin to move but more Na+ moves out than K+ moves in, creating an imbalance of charges which creates a electric current (action potential)

sarcoplasmic reticulum and calcium (step 4 of sliding filament theory)

the action potential moves across the sarcolemma and down the t-tubicles, which causes the SR to release calcium (Ca+). Ca+ binds with the troponin, changing the shape of the troponin and tropomyosin, revealing the actin binding sites.

myosin and actin (step 5 of sliding filament theory)

myosin releases inorganic phosphate and ADP which creates ATP. myosin can then change shape to bind to the actin binding sites. myosin and actin slide towards each other to create the contraction.

relaxation (step 6 of sliding filament theory)

ATP binds back to the myosin to detach and reposition the myosin from the actin. troponin covers back up the actin binding sites. Ca+ moves back into the SR and the sarcolemma is repolarized.

initial source of energy for muscle contraction

stored ATP

energy