Anatomy and physiology ch. 7 The muscular system Flashcards Preview

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skeletal muscle

also known as striated muscle,
it has 4 major characteristics: contractility, excitability, extensibility, and elasticity

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epimysium

connective tissue sheath that contains the muscle groups

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muscle fasciculi

various muscle bundles inside of the epimysium

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perimysium

connective tissue that binds muscle fibers together to make a muscle fasciculi

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muscle fibers

muscle cells

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endomysium

surrounds individual muscle fibers inside of the muscle fasciculi

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sarcolemma

the cell membrane of the muscle fiber

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transverse tubules

also known as T tubules, these go from the surface of the muscle cell and past the sarcolemma (cell membrane)

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sarcoplasmic reticulum

the T tubules go into this, and this is the place where there is a high concentration of CA2+, which is needed for muscle contraction.

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sarcoplasm

the cytoplasm of the muscle cell

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myofibrils

threadlike structures that extend from one end of the fiber to the other. composed of 2 parts, the actin myofilaments, and myosin. these function together to make the muscle contract.

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sarcomeres

one unit of contracting cells, located between z disks. the smallest unit that can contract by itself.

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actin myofilaments

also known as thin filaments, these are made up of 3 parts. Actin, Troponin, and Tropomyosin

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actin

the part that the myosin heads connect to

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troponin

these have binding sites for CA2+

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tropomyosin

these block the myosin myofilaments (thick filaments) from joining to the actin molecules. they are moved by CA2+ (found in troponin)

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myosin myofilaments

also known as thick filaments, they look like gold clubs, and the head of these attach to the actin when the tropomyosin is moved out of the way.

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z disk

the ends of a sarcomere, these are protein fibers that separate sarcomeres by providing an attachment for the actin.

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I band

consists of only actin myofilaments, has a z disk usually in the middle of it

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A band

the area between I disks that looks dark that contains both actin myofilaments and myosin myofilaments. the center of this is the H zone and the M line, which are light

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H zone

the center of the A band which only contains myosin myofilaments (this is the part that gives so the muscle can contract)

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M line

where the myosin myofilaments are anchored to. this is the center of the sarcomere

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resting membrane potential

the charge difference across a cell membrane

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motor neuron

nerve cells that stimulate muscles to contract. they generate action potentials that travel to skeletal muscle fibers

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neuromuscular junction

the synapse between a motor neuron and the muscle cell it is stimulating

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motor unit

refers to the neuron and the skeletal muscle fiber that it controls as a whole

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presynaptic terminal

an enlarged axon terminal

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synaptic cleft

the space between the presynaptic terminal and the postsynaptic membrane

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postsynaptic membrane

the muscle fiber membrane that receives the signal

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synaptic vesicles

vesicles that contain acetylcholine which move from the presynaptic terminal to the postsynaptic membrane

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resting membrane potential

when the inside of the cell membrane has a more negative charge than the outside of the cell

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depolarization

when the NA+ moves inside of the cell making the inside of the cell positive compared to the outside of the cell

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repolarization

going from the positive back to the resting membrane potential

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hyperpolarization

makes a cell membrane more negative than it was at the resting membrane potential

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sliding filament model

1. action potential goes to open CA2+ channels in presynaptic terminals
2. CA2+ causes release of ACh into synaptic cleft
3. Ach binds to receptor sites on postsynaptic membrane, and open NA+ channels, and NA+ rushes in
4. NA+ causes the T tubules and the sarcolemma to release their stored CA2+
5.CA2+ goes to troponin
6. the attachment causes tropomyosin to move out the way of the actin
7. myosin attaches to actin (cross-bridge)
8. P is released and the myosin heads bend
9. the bending make actin slide over the myosin (power stroke)
10.acetylcholinesterase breaks down ACh, NA+ channels close, causing the muscle to stop contracting.

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threshhold

weakest stimulus needed to produce a response

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twitch

rapid contraction and relaxation of a muscle

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tetanus

when the frequency of stimulation is so fast that no relaxation occurs

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Isometric

the amount of tension in the muscle increases (weight increases)

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isotonic

the amount of repititions increase

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tone

constant amount of tension of a long period of time

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slow twitch fibers

contract slowly
uses aerobic respiration
dark meat

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fast twitch fibers

contract quickly
uses energy from glycogen
white meat

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origin

non movable end of a muscle

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insertion

movable end of a muscle

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belly

the middle of a muscle

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prime mover

the muscle that is responsible for the majority of the movement i.e the bicep for flexion of the arm

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synergist

muscles that work together

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antagonist

muscle that opposes another muscle i.e. the tricep to the bicep

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naming skeletal muscle

1. location
2. origin/ insertion
3. size
4. shape
5. function

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lag phase (of muscle contraction)

the lag between the stimulus and actual contraction

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contraction phase (of muscle contraction)

time during which the muscle contracts

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relaxation phase (of muscle contraction)

time during which the muscle relaxes.

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summation

increasing the force of the contraction by rapidly stimulating the muscle. this is caused by dumping more calcium in the myofibrils than is actively transported out to the Sarcoplasmic reticulum

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recruitment

more contraction can occur because more motor units are stimulated to contract.

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aerobic respiration

uses O2 and breaks down glucose to make ATP, CO2, and H2O. this occurs in the mitochondria.

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anaerobic respiration

does not use O2, instead it uses glucose to make ATP and Lactic acid. this process uses only glucose.

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creatine phosphate

the muscle cells stored energy that can be used fast to make atp

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muscular fatigue

occurs when the muscle uses ATP faster than it produces it, and lactic acid builds up faster than it is removed

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physiological contracture

when a muscle cannot contract or relax because there is too little ATP to bind to myosin myofilaments

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psychological fatigue

involves the central nervous system. the muscles can still contract, but the person thinks they cannot keep going.