ADAM Unit 2 Flashcards
t tubule
invaginations of the sarcolemma penetrating deep into the interior of the muscle cell
synaptic cleft
the space between the axon terminal and the motor end plate
sarcolemma
the muscle cell membrane
synaptic vesicles
structures within the axon terminal that contain the neurotransmitter acetylcholine
sacromere
the contractile unit of the muscle cell that extends from z line to the next
terminal cisternae
structures within skeletal muscle cells that serve as a reservoir of calcium ions
motor end plate
a folded region of the sarcolemma at the neuromuscular junction
motor neuron axon
the elongated process of a nerve cell that carries impulses away from the nerve cell body to the muscle
what happens when a muscle cell contracts
thin filament slide past thick filaments and the sarcomere shortens
myosin
the protein that composes the major portion of the thick filament and includes two heads and a tail region
actin
the protein that composes the major portion of the thin filament
tropomyosin
a protein molecule that entwines around actin and blocks the myosin binding sites; prevents cross bridge cycling until it moves aside
troponin
a three polypeptide complex that binds calcium ions and drags tropomyosin off the myosin binding sites on actin
ATP
adenosine triphosphate, an organic molecule that stores and releases chemical energy within the cell
calcium ions
found in the extracellular fluid and terminal cisternae and can enter the cytosol where they play an important role in many processes such as muscle contraction and release of neurotransmitters
3 roles played by ATP in muscle contraction
energizing the power stroke of the myosin cross bridge
disconnecting the myosin head from the binding site on actin at the conclusion of the power stroke
actively transporting calcium ions into the sarcoplasmic reticulum
neuromuscular junction
the place where a motor neuron stimulates a muscle cell
resting membrane potential
the voltage that exists across a cell’s plasma membrane when the cell is at rest; cell interior is relatively more negative than the cell exterior
action potential
an electrical signal consisting of the depolarization and subsequent repolarization of a nerve or muscle cell membrane and functions as a signal to initiate an activity such as a muscle contraction
depolarization
a decrease in the negative resting membrane potential (the voltage that exists across the plasma membrane)
motor neuron
a single cell that extends from the brain or spinal cord to a muscle or gland
when the action potential arrives at the axon terminal, voltage-gated calcium channels open and then
calcium ions enter the axon terminal
presence of calcium ions in the axon terminal cause
synaptic vesicles fuse with the membrane
acetylcholine binds to the receptors sites on the motor end plate
calcium ions are pumped out of the axon terminal
acetylcholine diffuses away from its receptor site, the ion channel closes
acetylcholine is then broken down by acytelcholinesterase
an action potential is generated which does
propagates along the sarcolemma in all directions and down the t- tubules
an action potential causes
the release of calcium ions from the terminal cisternae into the cytosol
the presence of calcium ions in the cytosol triggers
contraction of the muscle cell
what does action attach to
myosin and troponin
what does myosin attach to
actin and ATP
what does troponin attach to
actin, tropomyosin, calcium ions
