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24 Terms
1
Motor Unit
A motor unit consists of one motor neuron and all the skeletal muscle fibers it controls.
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2
Neuromuscular Junction
The synapse between the axon terminal of a motor neuron and a skeletal muscle cell.
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3
Excitation
The first phase of muscle contraction, where an action potential triggers the release of acetylcholine at the neuromuscular junction.
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4
Excitation-Contraction Coupling
The process that links the electrical signals from the nerve to the mechanical contraction of muscle.
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5
Contraction Cycle
The sequence of events that occur during muscle contraction, which includes crossbridge formation, power stroke, crossbridge detachment, and recovery stroke.
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6
Sliding Filament Theory
The theory that explains muscle contraction as the sliding of actin over myosin filaments without changing their lengths.
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7
Acetylcholine (ACh)
The neurotransmitter that is released at the neuromuscular junction to stimulate muscle contraction.
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8
Calcium Ions (Ca²⁺)
Essential for muscle contraction; they bind to troponin, causing tropomyosin to move and expose active sites on actin.
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9
Troponin
A protein on the actin filament that binds calcium and triggers muscle contraction when calcium is present.
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10
Tropomyosin
A protein that blocks the active sites on actin filaments; it moves away when calcium binds to troponin.
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11
Crossbridge
The formation between myosin heads and active sites on actin filaments during muscle contraction.
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12
Power Stroke
The action that occurs when myosin heads pivot and pull actin filaments toward the M line of the sarcomere.
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13
ATP (Adenosine Triphosphate)
The energy source required for muscle contraction; it binds to myosin heads for crossbridge detachment.
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14
Spastic Paralysis
A condition where muscles contract uncontrollably due to issues with neurotransmitter regulation, like in the case of organophosphate poisoning.
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15
Flaccid Paralysis
Loss of muscle tone leading to limp muscles due to failure of the acetylcholine release or receptor blockage.
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16
Myofibril
The long, thread-like structures within muscle cells composed of overlapping actin and myosin filaments.
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17
End Plate Potential
The graded potential that occurs at the motor end plate, resulting from the binding of acetylcholine.
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18
Action Potential
A rapid change in membrane potential that is propagated along the muscle cell membrane, initiating contraction.
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19
Z Line
The boundary of a sarcomere where actin filaments are anchored.
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20
H Zone
The area within a sarcomere where only myosin filaments are present; it narrows during contraction.
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21
Somatic Nervous System
The division of the nervous system responsible for controlling voluntary movements of skeletal muscles.
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22
Acetylcholinesterase
An enzyme that breaks down acetylcholine in the synaptic cleft, stopping muscle stimulation.
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23
Gated Sodium Channels
Ionic channels that open in response to membrane depolarization, allowing sodium to enter the muscle cell and initiate action potentials.
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24
Gastric Nemesis
Referring to the gastrocnemius muscle, which has large motor units and is capable of generating significant force.
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