Describe the 4 major features of the sarcomere

1. arranged into highly ordered repeating units of actin & mysoin filaments
2. basic structural & functional unit of skeletal muscle
3. smallest portion of skeletal muscle capable of contracting
4. extends from Z disk to Z disk

Describe what happens to the following parts during contraction

A band: remains the same

I band: shortens 

H zone: disappears

Z disc: comes closer to other Z disk

be able to label A band, I band, Actin, H zone

Functions of the muscular system

1. producing movement
2. forcing substances thru body channels
3. circulate blood & maintain blood pressure
4. maintaining posture
5. stabilizing joints
6. generating heat

acetylcholine (Ach)

• neurotransmitter that stimulates skeletal muscle
• diffuses across synaptic cleft & attaches to receptors that are part of sarcolemma

acetylcholinesterase

• what Ach is broken down into during an action potential

antagonist & synergist

antagonist

• opposes & reverses a movement

adenosine triphosphate

(ATP)

• energy for cell
• muscles store limited supply of ATP & is only energy source that can be used directly to power muscle activity

calcium

(Ca²⁺)

• released from SR during contraction & binds to troponin allowing the rest of the process to occur

cross bridge

• myosin heads when they link thick & thin filaments together during contraction

I band

(light)

• tight band
• actin only
• space between two myosin molecules

lactic acid

• product of anaerobic respiration metabolism especially in the muscle
• cause muscle cramps

motor unit

• one neuron & all the skeletal muscles it stimulates

myasthenia gravis

• shortage of Ach receptors at neuromuscular junction
• may be autoimmune disease

origin & insertion

synaptic cleft

• gap in synapse filled with tissue fluid

tendon

• cord of dense fibrous tissue attaching a muscle to a bone

thick filament

• mostly bundled molecules of protein myosin
• also contains ATpase enzymes which split ATP to generate power for muscle contraction

thin filament

• contractile protein called actin & some regulatory proteins that allow myosin head-binding to actin
• anchored to Z disc

two myofibrils

• long ribbonlike organelles which nearly fill cytoplasm

name the 7 criteria used for naming muscle

1. direction of muscle fibers
2. size of muscle
3. location of muscle
4. number of origins
5. location of muscle's origin and insertion
6. shape of muscle
7. action of muscle

name the four characterisitics of skeletal muscle

1. excitibility
2. contractility
3. extensibility
4. elasticity

buccinators

location:

• primary cheek muscle

Diaphragm

location:

• in b/w abdominal and thoracic cavities

frontalis

location: 

• covers dome of the skull

Gastrocnemius

location:

• back of calf

intercostals

function:

• in b/w ribs

tibialis anterior

location:

• superficial, anterior of the leg

triceps brachii

location:

• posterior humerus

skeletal muscle

• long cylinder
• striated
• many nuclei per cell

cardiac muscle

• short cylinder
• one nuclei per cell
• striated
• intercalated disks

smooth muscle

• long tapered spindle
• one nuclei per cell
• no striations

sliding filament theory

1. action potential is sent to stimulate muscle
2. release of calcium (Ca²⁺) from sarcoplasmic reticulum
3. Ca²⁺ binds to troponin
4. tropomyosin moves off of the binding site
5. mysoin heads form cross bridges w/ actin
6. ATP->ADP+P+energy: Energy is used to bend myosin head toward the center of the sarcomere
7. ATP attaches to mysoin head to release crossbridges allowing the sarcomer to go back to normal