Internal Structure of Skeletal Muscle Cell

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29 terms

skeletal muscle fiber

A contractile cell with multiple peripheral nuclei and visible striations. These cells are under voluntary control. Because they are elongated, these cells are often referred to as these

skeletal muscle fiber nucleus

the cellular structure that contains the genetic material of the cell

sarcolemma

the plasma membrane of the muscle cell

sarcoplasmic reticulum (SR)

The endoplasmic reticulum of the muscle cell. Its interconnecting tubules surround each myofibril like the sleeve of a loosely knit sweater

terminal cisternae

The sac-like regions of the sarcoplasmic reticulum lying adjacent to the T-tubules; serve as specialized reservoirs of calcium ions

T-tubules

an invagination of the sarcolemma that projects deep into the muscle cell's interior

triad

a three-unit group consisting of one T-tubule lying between two adjacent terminal cistern

cytosol

the intracellular fluid in which the organelles are suspended and molecules and ions are dissolved

mitochondrion

the cytoplasmic organelle that is the site of ATP synthesis; referred to as the "powerhouse" of the cell

myofibril

a cylindrical bundle of contractile filaments within the skeletal muscle cell

what are the two types of myofilaments

a thin one composed mainly of the protein actin and the thick one which is made mostly of protein myosin

organelle

means "little organs", a little organ within a cell the performs specialized functions; they are membrane-bound compartments of structures of a cell

endomysium

the connective tissue wrapping that surrounds individual muscle cells (fibers)

endomysium

skeletal muscle cells are electrically insulated from each other by this

motor neuron

a single nerve cell that extends from the brain or spinal cord to a muscle or gland

in order for a skeletal muscle cell to contract, what must happen

each cell must be stimulated by a process of a motor neuron

neuromuscular junction

the place where a motor neuron stimulates a muscle cell; the muscle cell and motor neuron do not actually touch, but are separated by the synaptic cleft

synaptic vesicles

membranous organelles containing neurotransmitter substances; found within the axon terminals of neurons

motor neuron axon

the elongated process of a nerve cell that carries impulses away from the nerve cell body

axon terminal

the swollen, distal end of an axon; contains a neurotransmitter substance within synaptic vesicle

what do synaptic vesicles contain

acetylcholine

synaptic cleft

the space between the axon terminal and the membrane of the target cell, synaptic gap or synaptic space; tiny gap between the terminal of one neuron and the dendrites of another neuron (almost never touch); location of the transfer of an impulse from one neuron to the next

motor end plate

the folded portion of the sarcolemma in close contact with the synaptic ending of the axon terminal

acetylcholine

the neurotransmitter released by a motor neuron at the neuromuscular junction; one of the principal neurotransmitters of the peripheral nervous system

sarcomere

the contractile unit, the basic contractile unit of striated muscle; the segment of a myofibril between two adjacent z-lines; it includes the entire A-band and half of the I-band (to the Z-line) on each side of the A-band

the plus and minus signs indicate a polarized condition called the

resting membrane potential

polarized

a condition in which a difference in electrical charge exists across a cell membrane

resting membrane potential

the voltage that exists across a cell's plasma membrane when the cell is at rest (not conducting an impulse); cell interior is relatively more negative than the cell exterior; the resting membrane potential is measured in millivolts

action potential

an electrical signal consisting of the depolarization and subsequent re-polarization of a nerve or muscle cell membrane; travels along the membrane and functions as a signal to initiate an activity i.e., muscle contraction

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