book vocab chapter 9

endomysium

layer of connective tissue surrounding each skeletal muscle fiber

fascicle

small bundle of muscle fibers

perimysium

sheath of connective tissue that encloses a bundle of skeletal muscle fibers or a fascicle

epimysium

outer layer of connective tissue surrounding a skeletal muscle

tendon

cordlike or bandlike mass of dense connective tissue that connects a muscle to a bone

aponeurosis

sheet of connective tissue that attaches muscles to bone, skin, and other muscles

fascia

the most superficial layer and is continuous with the epimysium and serves to separate individuals muscles

compartment

the space that contains a particular group of muscles, blood vessels, and nerves all tightly enclosed by fascia

deep fascia

the portion of the network that surrounds the muscles

subcutaneous fascia

lies just beneath the skin, forming the subcutaneous layer

myofibril

any of the thread-like bundles of filaments in striated muscle cells

sarcolemma

a tubular sheath that encase and defines each muscle fiber, forming a barrier between extracellular and intracellular compartments

sarcoplasmic reticulum

membranous network of channels and tubules in a muscle fiber, corresponding to the smooth endoplasmic reticulum of other cells.

thin and thick filaments

structures containing the contractile proteins actin and myosin

location is intercellular

myosin

protein that, with actin, forms the filament that interact to contract muscle fibers

actin

protein in a muscle fiber that forms the thin filaments that slide between filaments of the protein myosin, shortening the muscle fibers

sarcomere

structural and functional unit of a myofibril

titin

protein that attaches myosin filaments to z lines in muscle

troponin

protein that regulates muscle contraction by altering the position of tropomyosin

tropomyosin

protein that blocks muscle contraction until its position is modified by troponin when calcium ions are present

transverse tubules

membranous channel that extends deep into the cell from a muscle fiber membrane. extensions of the sarcolemma into the sarcoplasm and contain extracellular fluid

I band

(the light bands) composed of thin actin filaments held by direct attachments to structures

Z bands

appear in the center of the I bands

A bands

(the dark bands) composed of thick myosin filaments overlapping thin actin filaments. Also a slightly lighter central region

M line

consists of proteins that help hold the thick filaments in place

striation

the visible alternating light and dark bands or stripes that characterize skeletal and cardiac muscle tissue, resulting from the organized arrangement of contractile proteins within the muscle fibers

troponin-tropomyosin complex

a regulatory protein system on the thin filaments (actin) of muscle cells, crucial for calcium-dependent regulation of muscle contraction

sarcoplasm

the cytoplasm containing nuclei, mitochondria, and myofibrils

cisterna

enlarged portion of the sarcoplasmic reticulum near the actin and myosin filaments of a muscle fiber

synapse

functional connection between the axon of one neuron and the dendrite or cell body of another neuron or the membrane of another cell type

neurotransmitter

chemical that an axon secretes, into a synapse, that stimulates or inhibits an effector or other neuron

motor neuron

neuron that conducts impulses from the central nervous system to an effector

synaptic cleft

a narrow extracellular space between the cells at a synapse

acetylcholine

type of neurotransmitter, which is a biochemical secreted into the synaptic clefts at the axon ends of neurons. diffuses across synaptic cleft

sliding filament model

muscles shorten when the thin(actin) and thick (myosin) filaments slide past each other, pulling on the muscle ends

action potential

sequence of electrical changes in part of a nerve cell or muscle cell exposed to a stimulus that exceeds threshold

myoglobin

oxygen-storing pigment in muscle tissue

creatine phosphate

molecule in muscle that stores energy

acetylcholinesterase

enzyme that catalyzes breakdown of acetylcholine

lactic acid threshold

when skeletal muscles are used more strenuously, these systems may not be able to supply enough oxygen to sustain the aerobic reactions of cellular respiration. Under these conditions muscles maybe limited to the anaerobic reactions to produce ATP, this shift in metabolism is referred to as

NMJ (neuro-muscular junction)

is a chemical synapse between a motor neuron and a muscle fiber