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What chemical helps to regenerate ATP?
Creatine phosphate
What is the function of skeletal muscles?
To move bones
What are muscle fibers made of?
Individual fibers called myofibrils
What is the connective tissue that surrounds fascicles?
Perimysium
What happens when poisons like botulism prevent the release of acetylcholine?
Muscles stay relaxed
What are the three types of muscles?
Skeletal, cardiac, and smooth muscles
What neurotransmitter is associated with muscles?
Acetylcholine
What cell organelle provides ATP for muscle activity?
Mitochondria
What is the gap between the nerve and the muscle called?
Synaptic cleft
What is hypertrophy?
Increase in muscle size
What is atrophy?
Decrease in muscle size
What symptoms would a person with a disease inhibiting cholinesterase production have?
Muscle that stays contracted
What is the function of cholinesterase?
To break down acetylcholine
During muscle contraction, cross-bridges form between which two structures?
Actin and myosin
What are the I band and A band made of in a sarcomere?
I band: Actin, A band: Myosin
What gives muscle cells a striated appearance?
The arrangement of dark and light fibers
What is the energy source for muscle contraction?
ATP
What substance is stored in vesicles in the motor neuron?
Acetylcholine
What happens to the number of motor units being activated during recruitment?
Increases
What is the sustained contraction of individual fibers, even when the muscle is at rest, called?
Muscle tone
What is the immovable end of a muscle called?
Origin
What is the movable end of a muscle called?
Insertion
What is muscle fatigue likely due to?
Buildup of lactic acid
What is a sarcomere?
The region between two Z-lines
What is the condition called when a body becomes stiff after death?
Rigor mortis
What does ATP become when it has been used?
ADP and phosphate
What is a motor unit?
Motor neuron and muscle fiber cell
What are myofibrils composed of?
Actin and myosin (myofilaments)
What is the specialized part of the muscle fiber membrane at the neuromuscular junction called?
Motor end plate
What type of connective tissue surrounds fascicles (bundles)?
Perimysium
What type of tissue surrounds the entire muscle?
Epimysium
What is the substance that crosses the gap between a neuron and a muscle fiber called?
Neurotransmitter
What do tendons connect?
Muscles to bones
What are bundles of muscle fibers called?
Fascicles
What is the minimum amount of stimulus required for a muscle contraction to occur called?
Threshold stimulus
What model explains how muscles contract?
Sliding filament theory
Place the following in the correct order: 1. Acetylcholine crosses the gap at the neuromuscular junction, 2. Calcium is released into the sarcoplasm, 3. Actin and myosin form links, 4. Myosin cross-bridges pull actin filaments inward.
1-4-2-3
What are the A bands and I bands in muscle fibers?
A bands are dark, I bands are light
What is the muscle fiber membrane called?
Sarcolemma
What is the transport network of the muscle called?
Sarcoplasmic Reticulum
What factor determines how forcefully a muscle contracts?
Number of cells stimulated
Describe muscle fatigue and its cause.
Caused by oxygen debt during prolonged muscle activity, muscle becomes unable to contract even when stimulated, depends on blood supply
Fill in the blanks in these sentences about the action potential and muscle cell contraction.
An action potential is an electrical current generated by the change in charge across the muscle cell membrane or sarcolemma. The result of this electrical impulse traveling from one end of the cell to the other is contraction of the muscle cell.
What is the function of acetylcholinesterase?
To break down ACh and prevent continued muscle contraction.
What is the role of the sodium-potassium pump?
To help the cell return to its resting state.
How do myofibrils attach to thin filaments?
By binding to binding sites on the thin filaments.
What provides energy for crossbridge attachment and detachment?
ATP.
What happens simultaneously in sarcomeres during muscle contraction?
The entire muscle cell shortens.
What is the role of calcium in the attachment of myosin crossbridges to actin?
It is required for the attachment.
What happens to calcium ions when the action potential ends?
They are reabsorbed into the sarcoplasmic reticulum.
What is the sarcolemma?
The plasma membrane of a muscle cell.
What is the function of the sarcoplasmic reticulum?
To transmit electrical impulses and store calcium ions.
What are myofibrils?
Long, filamentous organelles within muscle cells.
What are myofilaments?
Filaments of myofibrils made of proteins, primarily myosin or actin.
What are sarcomeres?
Contracting subunits of skeletal muscle.
What is myosin?
A fibrous protein that forms contractile filaments in muscle cells.
What is actin?
A protein that forms contractile filaments in muscle cells.