cbio2200 exam 4

myology

study of muscular system

endomysium

around each myofiber

perimysium

bundles myofibers into fascicles

epimysium

surrounds entire muscle (organ)

sarcolemma

plasma membrane

sarcoplasm

cytoplasm/internal space

muscle fiber

muscle cell; multinucleated; many mitochondria

myofibrils

unit in muscle fiber

terminal cisterns

sarcoplasmic reticulum running around myofiber

t tubules

infoldings of sarcolemma

triad

2 terminal cisterns + t-tubule; regulates Ca2+ levels

myofibrils

bundles of parallel myofilaments

thick filaments

myosin protein bundles

thin filament

actin protein bundles

elastic filament

titin protein bundles

myosin tail

part of thick filament that binds the molecules together

myosin head

part of thick filament that binds to ATP & actin

thin myofilament

two intertwined strands of actin

actin monomer

G actin

actin polymer

F actin

tropomyosin

blocks active sites (where myosin will bind)

troponin

calcium-binding protein on tropomyosin

sarcomere

contractile unit of muscle fibers

dystrophin

protein that anchors outer proteins of sarcolemma; helps transfer force from sarcomere → endomysium → tendon

sarcomere

region between two z discs

z disc

anchors thin & elastic filaments

m line

bisects H band; links thick filaments to each other

H band

only thick filaments; disappears when muscle contracts

A band

length of thick filaments; overlapped by thin filaments

I band

distance between two a bands; no thick filaments

A band

dark band in striations

I band

light band in striations

motor unit

one nerve fiber + all the muscle fibers innervated by it

neuromuscular junction

when neuron meets muscle fibers

ACh

neurotransmitter that initiates muscle movement

junctional folds

folds in sarcolemma that increase surface area of neuromuscular junction

botox

neurotoxin that blocks release of ACh

-90mV

muscle fiber resting membrane potential

-65mV

muscle fiber threshold

excitation

nerve action potentials lead to muscle action potentials

excitation-contraction coupling

action potentials cause activation of myofilaments, preparing them to contract.

contraction

muscle fiber develops tension & shortens (myosin + actin binding)

relaxation

stimulation ends, muscle fibers relaxes

cross-bridge formation

myosin head binds to active site on thin filament (actin)

power stroke

myosin head moves from unbent, high energy → bent, low energy

detachment

myosin head unbinds & re-binds further down the thin filament

unbent

recovery stroke; myosin head has ATP hydrolyzed (ADP + Pi)

bent

power stroke; myosin releases ADP & pulls actin filament along with it

relaxation

Ca2+ released from SR stops & reabsorbed by SERCA pumps

relaxation

atp is used to break cross bridges

rigor mortis

requirement of ATP & remaining Ca2+ in SR causes this after death