Sarcomere and such

sarcomere

contractile unit of a muscle fiber

sarcolemma

plasma membrane of a muscle cell/fiber

sarcoplasmic reticulum

specialized endoplasmic reticulum of muscle cells that stores calcium

Muscle fiber is also a muscle cell, true or false

true

myoglobin

stores and carries oxygen in muscle cells, releases oxygen when muscle needs it

myofibril

long, thread like structure inside a muscle cell (fiber) thats made up of many sarcomeres

epimysium

surrounds entire muscle

perimysium

surrounds fascicles (which are bundles of muscle fibers)

endomysium

Surrounds individual muscle fibers

myofilaments

The contractile proteins, actin and myosin, of muscle cells

skeletal muscle

voluntary striated and multinucleated

cardiac muscle

involuntary striated with intercalated discs

smooth muscle

involuntary non striated

actin

thin filament

myosin

thick filament

z discs

separate one sarcomere from the next, move closer together during contraction

A band

contains thick filaments and some thin filaments, will not change its size during contraction

H band

middle of A band; thick filaments only, gets smaller or disappears when muscle contracts

I band

thin filaments only, getting smaller during muscle contraction

M line

middle of sarcomere

titin

myosin is anchored to the z disc and m line by elastic filament that is called titin

troponin and tropomyosin

Troponin moves tropomyosin when calcium shows up which allows myosin to bind to actin

excitability

ability of a muscle cell to respond to a stimulus, usually a nerve signal

contractility

ability to shorten forcibly when stimulated

extensibility

ability to be stretched

elasticity

return to original length after stretching or contracting

function of skeletal muscle

1. maintain body temperature 2. regulate and entering of material 3. supporting soft tissue 4. help maintain posture and position

do you go from large to small or small to large in a muscle fiber

large to small, you've got the muscle surrounded by epimysium, the fascicles by perimysium and when we cut within the fascicle we have the endomysium around each muscle cell

muscle contraction

1. you've got to have calcium 2. the calcium will come from the terminal cisternae and will bind to troponin tropomyosin and cause that switch 3. troponin itself changes shape but really the troponin tropomyosin complex is changing so that you get the myosin binding heads or active sites exposed to myosin binding heads

end of muscle contraction

1. you've got to recapture the calcium ions 2. then troponin tropomyosin will recover those myosin binding sites on the actin molecule and then the contraction will end

cholinergic receptors

receptors that respond to the neurotransmitter acetylcholine (ACh)

nerve agents

are cholinesterase inhibitors they will cause the acetylcholine to remain in the cleft

Acetylcholine

essential for muscle contraction, nerve sends a signal which releases ACh then it binds to the muscle and opens channels then the muscle lets in the calcium and the contraction happens and then ACh is broken down and the muscle relaxes