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Flashcards in Chapter 10 Deck (90):
1

skeletal muscle

muscle that covers bone. striated and voluntary

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cardiac muscle

heart, striated, involuntary

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smooth muscle

hollow visceral organs, non-striated and involuntary

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7 skeletal functions

movement, posture, supports soft tissues, stabilizing joints, guards opening, generate heat, stores nutrients

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muscle fibers

muscle cells thousands of which make up a muscle

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epimysium

dense layer of collagen that surrounds the entire muscle; connects to deep fascia

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perimysium

divides muscles into compartments; within each is a fascicle (a bundle of muscle fibers)

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endomysium

surrounds individual muscle fibers; flexible, elastic connective tissue contains: capillaries, nerve fibers and myosatellite cells

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These three layers fuse at the end of a muscle to create a tendon or aponeurosis that attaches to a bone

tendons, origin, insertion

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tendons

fibrous connective tissue that merges with the periosteum of bones, connects muscles to bones or other muscles

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origin

immobile bone muscle attachment

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insertion

moveable bone muscle attachment, it always moves toward the origin

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Muscle cells are extremely ____ and ____?

large
multinucleate

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Myoblasts

primitive muscle cells that fuse during development contributing to the large size and multinuclea features

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Myosatellite

myoblast cells that have NOT fused and are found in adult muscle tissue. they are stem cells that aid in muscle repair

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Sarcolemma

muscle cell membrane

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Sarcoplasm

the cytoplasm of a muscle cell

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T-Tubules
(transverse tubules

extensions of the sarcolemma that run deep into the muscle cell so that an action potential can effectively depolarize a muscle cell quickly/completly

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Myofibrils

cylindrical structures within a muscle fiber that contain proteins responsible for contraction. 100-1000 in ea. cell, they run the length of the cell and attach at the ends to a tendon

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myofillaments

bundles of protein filaments within myofibrils, they contain; actin, myosin and titin

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Actin

a THIN protein filament
contains myosin binding sites to aid in contraction; also contains troponin and tropomyosin

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Myosin

a THICK protein filament. contains a myosin head which interacts with the thin filament

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High amounts of ____ and ____ are found scattered among the myofibrils for high ____ production

glycongen, mitochondria, energy

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Sarcoplasmic reticulum

a modified form of the ER found in muscle cells
The SR is a reservoir for calcium ions that can be released into sarcoplasm to stimulate contraction

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Terminal Cisternae

expanded chambers that form when sarcoplasmic reticulum fuse

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Triad

a combo of a pair of terminal cistern and a t-tubule

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Sarcomeres***
know figure 10-4 and 10-5!

this is the FUNCTIONAL unit of the muscle, a chain of smaller contractile units within myofibril

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A bands

the DARK bands found at the center of ea. sarcomere

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M line

found in the MIDDLE of the A band; connect nerighboring thick filaments

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H band

a lighter region on either side of the M line; contains thick filaments but no thin filaments

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Zone of overlap (fig. 10-5)

dark region where thin filaments and thick filaments overlap; 3 thick filaments surround ea. thin filament and 6 thin filaments surround ea. thick filament

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I bands

light bands containing thin filaments only and extend from the A band of one sarcomere to the A band of the next

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Z line

protein discs that are the end lines of a sarcomere and interconnect thin filaments of adjacent sarcomeres; actin (thin) attach to the Z line on ea. end of the sarcomere; Z lines give striates muscle its stripes

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Titin

elastic protein strands that anchor myosin to the Z line; inhibits muscles from stretching too far (stretch and recoil)

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Troponin and Tropomyosin

inhibitory proteins that prevent actin from sliding with myosin

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neuromuscular junction

where the motor neuron terminates on the muscle fiber; ea. muscle fiber has its own neruromuscular junction that controls it

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axon terminal

enlarged tip of the motor neuron containing sacs of the neurotransmitter, acetylcholine

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sarcolemma

muscle fiber cell membrane. contains recptor sites for acetylcholine (neurotransmitter) and acetycholinesterase (inacivator)

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T tubules

inward folds of the sarcolemma which carry the action potential to the interior of the muscle cell

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synapse

the small space between the axon terminal and the sarcolemma

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During muscle contraction.... 6 steps:

1. sarcomeres shorten, 2. muscle fibers contract (shorten), 3. H and I bands get smaller, 4. zones of overlap get bigger, 5. Z lines move closer together, 6. A bands remain the same

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Arrival of the action potential, step 1

a nerve impulse arrives at axon terminal, ACH is released into synapse

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...action potential, step 2

sarcolemma receives ACH into its receptor sites and causes Na+ to rush into cell

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...action potential, step 3

sarcolemma is depolarized, T-tubules bring action potential to the interior of muscle cell

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...action potential, step 4

ACHE inactivates ACH

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...action potential, step 5

calcium ions are released from cisternae of sarcoplasmic reticulum into the sarcoplasm in response to depolarization; the Ca+ binds to the troponin-tropomyosin complex to free up the myosin receptor sites on the actin filament

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...action potential, step 6

myosin splits ATP to release energy, myosin heads attach to actions myosin binding site and pulls actin filaments towards the center of the sarcomere

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...action potential, step 7

all the sarcomeres shorten, muscle fiber contracts

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Resting sarcomere

myosin heads are charged, pointing away from the M line

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Contracted sarcomere

ATP splits and continues to 're-cock' the myosin heads as long as there is sufficient calcium

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How long a contraction lasts depends on what three things?

1. period of stimulation at the neuromuscular junction 2. presence of calcium in the sarcoplasm 3. amount of ATP available

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muscle tone

always on enables fast reaction, muscles are always in a slight state of contraction except in certain stages of sleep

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Functions of muscle tone

maintains posture, helps prevent sudden changes in body movement, allows for shock absorption

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Good muscle tone improves

coordination, because when muscles are slightly contracted they can react more quickly and with greater exertion

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good muscle tone increases a ____ ___which can aid in ____ and ___ ____

resting metabolism, exercise and weight loss

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Alternate muscle fibers ____ so the muscle does not

contract, tire out

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Isotonic contraction

tension rises and a muscles length changes bringing about movement

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concentric contraction

muscle tension exceeds load and muscle shortens

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eccentric contraction

tension is less than the load, the muscle elongates due to the contraction of another cuscle or pull of gravity

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isometric contraction

the muscle does not change load because the tension produced never exceeds the load; contraction without movement

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Returning a muscle to resting length

a muscle can actively shorten but they cannot actively lengthen

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elastic force

recoil to original length

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opposing muscle contraction

the contraction of opposing muscles can return a muscle to its resting length

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Gravity

muscles relax and gravity pulls a limb down and stretches the muscle to resting length

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ATP

there is not enough stored in muscles and it is depleted quickly so it has to be generated quickly

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creatine phosphate

ATP that is not being used by a resting muscle is transferred to creatine to be stored for later

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Creatine Kinase

when high amounts are found in the blood concentration it indicates sever muscle damage

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Glycogen

most abundant energy source, broken down to glucose then broken down to pyruvate to form ATP though the krebs cycle; glcogen is important for sustained contraction

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Anaerobic metabolism

provides a small amount of ATP within a muscle cell
provides 95% of ATP production in a resting cell by the breakdown of fatty acids; when a cell becomes active, it breaks down pyruvate allowing for energy production

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Anaerobic metab/glycolysis step 1.

1. glycolysis occurs in the sarcoplasm, glucose is broken down into two pyruvate molecules without oxygen, this makes glycolysis anaerobic
glycolysis makes small amounts of ATP (2 molecules) which can be used by the cell when energy demands are at a maximum and O2 is limited

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Aerobic metab. step 2 and 3

2. mitochondria absorbs pyruvate
3. a CO2 molecule is removed from ea. pyruvate molecule in the mitochondria

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Aerobic metab. step 4

the remainder of pyruvate enters the citric acid/krebs cycle which breaks down the pyruvate into CO2 and H+

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Aerobic metab. step 5 and 6

5. H+ are transferred to oxygen atoms to form water
6. all of these steps ultimately support the conversion of ADP to ATP

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Every molecule of pyruvate fed into the citric acid cycle produces ____

17 ATP molecules

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Muscle fatigue

when the muscle can no longer perform

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normal muscle function requires (1-4)

1. energy reserves, 2. circulatory supply, 3. normal blood oxygen levels, 2. normal blood PH

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Muscle can fatigue due to (1-4)

1. depletion of energy reserves, 2. damage to sarcolemma or SR, 3. decrease in PH which affects proper calcium binding, 4. decreased desire to continue activity due to pain and low blood PH

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Lactic acid build up

at peak levels of muscle activity, pyruvate builds up in the cell faster than mitochondria can utilize it; it converts at this point to lactic acid which releases hydrogen molecules and lowers the ph of the sarcoplasm=fatigue

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Lactic acid removal and recycling

muscles can continue to contract in the absence of oxygen due to glycolysis but at the expense of producing lactic acid and lowering tissue fluid ph

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Lactic acid removal/recycling, 3 facts

1. during recovery oxygen levels become abundant again
2. lactic acid can be converted back to pyruvate in the presence of oxygen
3. pyruvate is then used to boost glycogen reserves or to generate more ATP for normal cell function

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Oxygen debt

the amount of oxygen needed to restore pre-exertion conditions...
during exertion oxygen has been depleted, recovering oxygen demands are elevated, we owe the body oxygen for restoring ATP, CP and glycogen to their former concentrations

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Recovery oxygen uptake

increase heart rate respiratory and heart rate remain high for a period of time after exercise to repay O2 debt

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Types of skeletal muscle fibers

fast, slow and intermediate

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Fast Fibers

*most common
*lrg in diameter
*densely packed myofibrils
*lrg glycogen reserves
*few mitochondria
*produce powerful contractions because of high numbers of myofibrils
*fatigue quickly cuz they use lots of ATP and there is not enough mitochondria to make more
*prolonged activity supported by anaerobic metabolism

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Slow Fibers

*half the diameter of fast fibers
*more resistant to fatigue
*numerous mitochondria
*higher oxygen due to more capillaries
*contain myoglobin (red pigment carries O2, makes it dark red)

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Intermediate Fibers

*appearance is closer to fast fibers (little myoglobin and appear pale)
*function is between fast and slow fibers

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white muscles

dominated by fast fibers, pale, used for power

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red muscles

dominated by slow fibers, blood vessels and myoglobin, give it a red color

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Hypertrophy

muscle fibers increase in diameter due to increased number of myofibrils from repeated/intense stimulation

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atrophy

reduction in muscle size (loses tone and mass) due to lack of stimulation, reversible at first but if fibers die they cannot be replaced