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Chapter 6-Muscles

Anatomy/Physiology

QuestionAnswer
What is contractility? The ability of skeletal muscle to shorten with force.
What is excitability? The capacity of skeletal muscle to respond to a stimulus.
what is extensibility? The ability to be stretched.
What is elasticity? The ability to recoil to their original resting length after they have been stretched.
What is the epimysium? The sheath that surrounds eacch connective tissue.
What is the perimysium? Loose coonective tissue that surrounds visible muscle fibers.
what is the fascia? Another connective tissue that located outside the epimysium.
What are fibers? Single muscle cells that composite fasciculi.
What are myofibrils? A threadlike structure that extends from one end of the fiber to the other end of the fiber.
What are actin myofilaments? Thin myofilament s that resemble 2 minute strands of pearls twisted together.
What are myosin filaments? Thick myofilaments that resemble bundles of minute golf clubs.
What are sacromeres? Actin and myosin myofilaments form highly ordered units.
What is resting membrane potential? The charge difference across the membrane.
What is action potential? The brief reversal back of the charge.
What are motor neurons? Are nerve cells that carry action potentials to skeletal muscle fibers.
What is a neuoromuscular junction, or a synapse? Axons enter the muscles and branch. Each branch that connects to the muscle.
What is a motor unit? A single motor neuron and all the skeletal muscle fibers it innervates.
What is a presynaptic terminal? The enlarged terminal.
What is the synaptic cleft? The space between the presynaptic terminal and the muscle cell.
What is the postsynaptic terminal? The muscle fiber.
Where are synaptic vesicles located? In the presynaptic terminal.
What is acetylcholine? A neurotransmitter that is secreted by synaptic vessels.
What is acetycholinesterase? When the acetylcholine is released into the synaptic cleft between the neuron and muscle cell is broken down by enzymes.
What is a sliding filament mechanism? The sliding of actin myofilaments past myosin myofilaments during contraction.
What is a muscle twitch? A contraction of an entire muscle in respone to a stimulus that causes the action potential in one or more muscle fibers,
What is the treshold? A level that is reached required to stimulate a muscle fiber.
What is the all or none response? Whether or not a muscle fiber has been stimulated enough to operate fully or not at all.
What is the lag phase? The time between application of a stimulus to a motor neuron and the beginning of a contraction.
What is the contraction phase? The time of contraction.
What is the relaxation phase? The time during which the muscle relaxes.
What is tetany? Where the muscle remains contracted without relaxing.
What is recruitment? The increase in the number of motor units being activated.
What is creatine phosphate? A high-energy molecule.
What is anaerobic respiration? Being without oxygen.
What is aerobic respiration? Being with oxygen (more efficient).
What is oxygen debt? The amount of oxygen needed in chemical reactions to convert lactic acid to glucose and to replinish the depleted stores of creatine phosphate stores in muscle cells.
What is muscle fatigue? Results when ATP is used during muscle contraction faster than it can be produced in the muscle cells.
What is the meaning of isometric? When the length of the muscle does not change, but the amount of tension increases during the contraction process.
What is the meaning of isotonic? The amount of tension produced by the muscle is constant during contraction, but the length if the muscle changes.
What is muscle tone? Refers to constant tension produced by muscles of the body for long periods of time. Keeps heads up and backs straight.
What are fast-twitch fibers? They contract quickly and fatigue quickly. Well adapted to performanaerobic metabolism.
What are slow-twitch fibers? They contract more slowly and are more resistant to fatige. They are better suited for aerobic metabolism.
What is the origin? The most stationary end of the muscle.
What is insertion? The end of the muscle undergoing the greatest movement.
What is the belly? The portion of the muscle between the origin and the insertion.
What are synergists? Muscles that work together to accomplish specific movements.
What are antagonists? Muscles that work in opposition to one another.
What is the prime mover? The one muscle that plays a major role among a group of synergists.
Muscles help produce what that is essential for maintenance of normal body temperature? Heat.
What does the fascia do? It surrounds and seperates muscles.
What is a single cylindrical cell containing several nuclei? A muscle fiber.
What is the cytoplasm of each fiber filled with? Myofibrils.
Myofibrils consist of how mmany kinds of major proteins? Two.
Sacromeres are joined end to end to form what? The myofibril.
The sacromere is the basic structural and functional unity of what? Muscle.
Each sacromere extens from one Z line to what other line? A Z line.
Each Z line is an attachment site for what? Actin.
The arrangement of actin and myosin give what kind of appearance? Banded.
On each sid of the Z line there is a band that consists of actin called what? An I band.
The A band extends the length of what? The myosin.
What is darker than the central region in each sacromere? The A band.
In the center of each sacromere is another light area which consists of only myosin called what? The H zone.
The myosin myofilaments are anchored in the center of the sacromere at a dark staining band called what? The M line.
The outside of most cell membranes is positively charged compared to the outside of the cell membrane which has what kind of a charge? A negative charge.
When what is stimulated causes the membrane characteristics to briefly change? The muscle cell.
Axons enter what? The muscles and branch.
Many motor units form what? A single muscle.
A neuromuscular junction if formed by what? An enlarged nerve terminal restin in an indentation of the muscle membrane.
What diffuses across the synaptic cleft and binds to the postsynaptic terminal causing a change in the postsynaptic cell? Acetylcholine.
When an action potential reaches the nerve terminal, what happens? It causes the synaptic vessels to release acetylcholine into the synaptic cleft by exocytosis.
What diffuses across the synaptic cleft and binds to receptor molecules in the muscle membrane? The acetylcholine.
What is the muscle cell membrane called? Sarcolemma.
The combination of acetylcholine with its receptor causes an influx of what? Sodium ions into the muscle fiber.
What causes the muscle to contract? An influx of sodium ions which initiates the action potential.
What enzymatic breakdown ensures that one action potential in the neoron yields only one action potential in the skeletal muscle, and only one contraction of the muscle cell? Acetycholinesterase.
Muscle contraction occurs when what happens? When the actin and myofilaments slide past one another causing the sacromeres to shorten.
When the sacromeres shorten what else do they cause to shorten? Muscle.
In muscle contraction, when the H and I bands shorten, which band does not change in length? The A band.
If successive stimuli is given you get excessive what that occurs so frequently because the muscle doesn't have time to fully relax? Twitches.
What is needed for energy for muscle contraction? ATP
What does ATP stand for? Adenosine Triphosphate.
Where is ATP produced? In the mitochondria.
What is short-lived and unstable that eventually degenerates to more stable ADP plus phosphates? ATP
What does ADP stand for? Adenosine Diphosphate.
Constant ATP production isn't neccessary for the movement of what? Muscles.
What high-energy molecule cannot be stockpiled while at rest? ATP
During periods of inactivity as excess ATP is produced in the muscle cell, the energy contained in ATP is used to synthesize what? Creatine Phosphate.
During perios of activity, the energy stored in creatine phosphate can be accessed quickly and used to produce ATP, which can then be used in what? Muscle Contraction.
After intense exercise, what remains elevated for a period of time even though the muscles are no longer actively contracting? Respiration Rate.
What provides the oxygen to payback the oxygen debt? Increased respiration.
How many types of muscle contractions are there? Two.
What are the two types of muscle contracitons called? Isometric, and isotonic.
The points of attachment of each muscle are where? It's origin and insertion.
At points of attachment muscle is connected to the bone by what? Tendons.
What has multiple origins or heads? Some muscles.
Most what have names that are descriptive? Muscles.
What are muscles named according to? Location, size, orientation of fibers, shape, origin, insertion, function, etc.
How many major functional characteristics are there to skeletal muscle? Four.
What are the four major functional characteristics to skeletal muscle? Conractility, Excitability, Extensibility, Elasticity.
Where is the I band located? Between the Z band and the A band.
A sacromere consists of what? One Z line to the left, and one to the right, while there is one I band accompanying each on the introverted side of each Z line, with an M line in btween the pair of A bands.
Where is the H zone located? Around the perimeter of the M line.
Created by: davidpauley11