DCAP Ch 10-11 (Exam 5)

acetylcholine (ACh)

neurotransmitter that binds at a motor end-plate to trigger depolarization

actin

protein that makes up most of the thin myofilaments in a sarcomere muscle fiber

action potential

change in voltage of a cell membrane in response to a stimulus that results in transmission of an electrical signal; unique to neurons and muscle fibers

aerobic respiration

production of ATP in the presence of oxygen

angiogenesis

formation of blood capillary networks

aponeurosis

broad, tendon-like sheet of connective tissue that attaches a skeletal muscle to another skeletal muscle or to a bone

ATPase

enzyme that hydrolyzes ATP to ADP

atrophy

loss of structural proteins from muscle fibers

autorhythmicity

heart's ability to control its own contractions

calmodulin

regulatory protein that facilitates contraction in smooth muscles

cardiac muscle

striated muscle found in the heart; joined to one another at intercalated discs and under the regulation of pacemaker cells, which contract as one unit to pump blood through the circulatory system. Cardiac muscle is under involuntary control.

concentric contraction

muscle contraction that shortens the muscle to move a load

contractility

ability to shorten (contract) forcibly

contraction phase

twitch contraction phase when tension increases

creatine phosphate

phosphagen used to store energy from ATP and transfer it to muscle

dense body

sarcoplasmic structure that attaches to the sarcolemma and shortens the muscle as thin filaments slide past thick filaments

depolarize

to reduce the voltage difference between the inside and outside of a cell's plasma membrane (the sarcolemma for a muscle fiber), making the inside less negative than at rest

desmosome

cell structure that anchors the ends of cardiac muscle fibers to allow contraction to occur

eccentric contraction

muscle contraction that lengthens the muscle as the tension is diminished

elasticity

ability to stretch and rebound

endomysium

loose, and well-hydrated connective tissue covering each muscle fiber in a skeletal muscle

epimysium

outer layer of connective tissue around a skeletal muscle

excitability

ability to undergo neural stimulation

excitation-contraction coupling

sequence of events from motor neuron signaling to a skeletal muscle fiber to contraction of the fiber's sarcomeres

extensibility

ability to lengthen (extend)

fascicle

bundle of muscle fibers within a skeletal muscle

fast glycolytic (FG)

muscle fiber that primarily uses anaerobic glycolysis

fast oxidative (FO)

intermediate muscle fiber that is between slow oxidative and fast glycolytic fibers

fibrosis

replacement of muscle fibers by scar tissue

glycolysis

anaerobic breakdown of glucose to ATP

graded muscle response

modification of contraction strength

hyperplasia

process in which one cell splits to produce new cells

hypertonia

abnormally high muscle tone

hypertrophy

addition of structural proteins to muscle fibers

hypotonia

abnormally low muscle tone caused by the absence of low-level contractions

intercalated disc

part of the sarcolemma that connects cardiac tissue, and contains gap junctions and desmosomes

isometric contraction

muscle contraction that occurs with no change in muscle length

isotonic contraction

muscle contraction that involves changes in muscle length

lactic acid

product of anaerobic glycolysis

latch-bridges

subset of a cross-bridge in which actin and myosin remain locked together

latent period

the time when a twitch does not produce contraction

motor end-plate

sarcolemma of muscle fiber at the neuromuscular junction, with receptors for the neurotransmitter acetylcholine

motor unit

motor neuron and the group of muscle fibers it innervates

muscle tension

force generated by the contraction of the muscle; tension generated during isotonic contractions and isometric contractions

muscle tone

low levels of muscle contraction that occur when a muscle is not producing movement

myoblast

muscle-forming stem cell

myofibril

long, cylindrical organelle that runs parallel within the muscle fiber and contains the sarcomeres

myogram

instrument used to measure twitch tension

myosin

protein that makes up most of the thick cylindrical myofilament within a sarcomere muscle fiber

myotube

fusion of many myoblast cells

neuromuscular junction (NMJ)

synapse between the axon terminal of a motor neuron and the section of the membrane of a muscle fiber with receptors for the acetylcholine released by the terminal

neurotransmitter

signaling chemical released by nerve terminals that bind to and activate receptors on target cells

oxygen debt

amount of oxygen needed to compensate for ATP produced without oxygen during muscle contraction

pacesetter cell

cell that triggers action potentials in smooth muscle

pericyte

stem cell that regenerates smooth muscle cells

perimysium

connective tissue that bundles skeletal muscle fibers into fascicles within a skeletal muscle

power stroke

action of myosin pulling actin inward (toward the M line)

pyruvic acid

product of glycolysis that can be used in aerobic respiration or converted to lactic acid

recruitment

increase in the number of motor units involved in contraction

relaxation phase

period after twitch contraction when tension decreases

sarcolemma

plasma membrane of a skeletal muscle fiber

sarcomere

longitudinally, repeating functional unit of skeletal muscle, with all of the contractile and associated proteins involved in contraction

sarcopenia

age-related muscle atrophy

sarcoplasm

cytoplasm of a muscle cell

sarcoplasmic reticulum (SR)

specialized smooth endoplasmic reticulum, which stores, releases, and retrieves Ca++

satellite cell

stem cell that helps to repair muscle cells

skeletal muscle

striated, multinucleated muscle that requires signaling from the nervous system to trigger contraction; most skeletal muscles are referred to as voluntary muscles that move bones and produce movement

slow oxidative (SO)

muscle fiber that primarily uses aerobic respiration

smooth muscle

nonstriated, mononucleated muscle in the skin that is associated with hair follicles; assists in moving materials in the walls of internal organs, blood vessels, and internal passageways

somites

blocks of paraxial mesoderm cells

stress-relaxation response

relaxation of smooth muscle tissue after being stretched

synaptic cleft

space between a nerve (axon) terminal and a motor end-plate

T-tubule

projection of the sarcolemma into the interior of the cell

tetanus

a continuous fused contraction

thick filament

the thick myosin strands and their multiple heads projecting from the center of the sarcomere toward, but not all to way to, the Z-discs

thin filament

thin strands of actin and its troponin-tropomyosin complex projecting from the Z-discs toward the center of the sarcomere

treppe

stepwise increase in contraction tension

triad

the grouping of one T-tubule and two terminal cisternae

tropomyosin

regulatory protein that covers myosin-binding sites to prevent actin from binding to myosin

troponin

regulatory protein that binds to actin, tropomyosin, and calcium

twitch

single contraction produced by one action potential

varicosity

enlargement of neurons that release neurotransmitters into synaptic clefts

visceral muscle

smooth muscle found in the walls of visceral organs

voltage-gated sodium channels

membrane proteins that open sodium channels in response to a sufficient voltage change, and initiate and transmit the action potential as Na+ enters through the channel

wave summation

addition of successive neural stimuli to produce greater contraction

first step of muscle contraction

nerve impulse travels from dendrite to axon end terminal (synaptic bulb)

second step of muscle contraction

ion channels open to receive calcium into synaptic end

third step of muscle contraction

synaptic vesicles release acetylcholine into the synapse

fourth step of muscle contraction

acetylcholine binds to receptors in the sarcolemma, which open to allow sodium ions to enter muscle (depolarization or action potential)

fifth step of muscle contraction

action potential is propagated along the sarcolemma and into T tubules to open calcium channels in sarcoplasmic reticulum

sixth step of muscle contraction

sarcoplasmic reticulum diffuses out of the terminal cisternae into the sarcoplasm

seventh step of muscle contraction

calcium binds to troponin, which moves the troponin-tropomyosin complex to expose myosin binding site on actin

first step of crossbridge cycling

myosin head attaches to exposed binding site on actin, forming a crossbridge

second step of crossbridge cycling

myosin head pivots and pulls the thin filament toward the center of the sarcomere; ADP and Pi are released from the myosin head

third step of cross bridge cycling

ATP binds to myosin head causing it to detach from actin

last step of crossbridge cycling

ATP splits into ADP and Pi; myosin head returns to the cocked position

origin

the fixed attachment point for a muscle

insertion

the moveable attachment point for a muscle

agonist

muscle that provides the major force for producing movement during a particular action

antagonist

muscles that oppose or reverse a movement, working in opposition to the agonist.