Lab Practical EX. 12

striations

dark A band

light I band

muscle fiber/cell (singular cynlinder)

multiple nuclei

muscle fiber/cell (whole thing)

nucleus

dark A band (in whole muscle fiber)

light I band

striations

sarcolemma (plasma membrane)

mitochondrion (makes ATP)

myofibril (organelle)

myofibril (whole thing)

sarcomere

z discs

H zone

I band (light on myofibril)

A band (dark on myofibril)

M line

myofilaments

thin (actin) filaments

elastic (titan) filament (recoil)

thick (myosin) filament

sarcomere (in group of myofibrils)- between one I band to the middle of the next)

triad

transvere (T) tubule

2 terminal cisterns of the SR

dense fibrous irregular CT sheath that covers entire skeletal muscle

epimysium

dense irregular CT, wraps fasicles (bundles of muscle fibers/cells)

perimysium

delicate areolar CT, wraps individual muscle fibers/cells

endomysium

bundle of skeletal muscle fibers

fasicle (wrapped by perimysium)

all sheaths converege to form a broad flat sheet of dense fibrous CT to attach muscle to bone, cartilage, or other muscles

aponeuroses

sheaths come together to from cord-like bands of dense regular CT to attach muscles to bones

tendons

a muscle’s more movable attachment

insertion

fixed (immovable) muscle attachment

origin

each axon of the neuron divides into many branches

terminal branches (this is a singular axon terminal)

each terminal branch ends with

axon terminal (where branch meets a muscle fiber/cell, forms neuromuscular junction)

a neuron and all the muscle fibers it stimulates make up a

motor unit

fluid filled gap between axon terminal and muscle fiber

synaptic cleft

within the mitochondria and vesicles in the axon terminal, a neurotransmitter

acetylcholine (Ach)

process of Ach

• when action potential reaches the axon terminal, voltage gated Ca2+ channels open

• Ca2+ enters the axon terminal and causes Ach to be released by exocytosis

• Ach rapidly diffuses across the synaptic cleft and combines with receptors of the sarcolemma

• when receptors bind Ach, a change in the permeability of the sarcolemma occurs

• ion channels open briefly, depolarizing the sarcolemma, contracting the muscle

when action potential reaches the axon terminal, voltage gated Ca2+ channels open, Ca2+ enters the axon terminal and causes Ach to be released by _____

exocytosis

after Ach is released by exocytosis, it rapidly diffuses across the synaptic cleft and combines with

sarcolemma receptors

• when receptors bind Ach, a change in the permeability of the sarcolemma occurs

• ion channels open briefly, depolarizing the sarcolemma, contracting the muscle

ends contraction; eats Ach

AchE

blocks the release of Ach from the axon terminal, so muscles cannot contract

botulism

binds to AchE (stop contractor) and inhibits it, so muscle remain contracted

sarin nerve gas