Term
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Definition
skeletal (voluntary)
cardiac muscle (involuntary)
smooth muscle (involuntary |
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Term
| Each cell in skeletal muscle tissue is ______. |
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Definition
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Term
| 6 functions of skeletal muscles |
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Definition
1. Produce skeletal movement.
2. Maintain posture and body position
3. Support soft tissue
4. Guard body entrances and exits
5. Maintain body temperature
6. Store nutrients |
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Term
| Each muscle has 3 layers of connective tissue |
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Definition
1. epimysiuim
2. perimysium
3. endomysium |
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Term
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Definition
A dense layer of collagen fibers that surround the entire muscle.
-separates the muscle from nearby tissues and organs
-connected to the deep fascia, a dense connective tissue layer |
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Term
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Definition
-surrounds a bunch of muscle fibers
-divides into a series of compartments
-each compartment contains a fascicle
-contains collagen, elastic fibers, and blood vessels and nerves
-blood vessels and nerves supply the muscle fibers within the fascicles |
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Term
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Definition
-surrounds the individual muscle cells called muscle fibers
-a delicate network
-flexible, elastic connective tissue layer |
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Term
| The endomysium contains ____________. |
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Definition
1. capillary networks that supply blood to the muscle fibers
2. myosatellite cells, stem cells that help repair damaged muscle tissue
3. nerve fibers that control the muscle |
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Term
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Definition
| At each end of the muscle, the collagen fibers of the epimysium, perimysium, and endomysium come together. Attaches muscle to bone |
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Term
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Definition
| broad, tendinous sheets that may serve as the origin or insertion of a skeletal muscle |
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Term
| Characteristics of skeletal muscle fibers |
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Definition
1. size (enormous)
2. multinucleate (hundreds)
3. striated (banded)
thin filaments: actin thick filaments: myosin |
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Term
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Definition
Embryonic cells
Groups of myoblasts fuse, forming individual multinucleate skeletal muscle fibers |
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Term
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Definition
Plasma membrane of a muscle fiber, surrounds the sarcoplasm
Has a transmembrane potential |
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Term
| Transverse Tubules or T tubules |
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Definition
| narrow tubes, surfaces are continuous with the sarcolemma, conduct the signal to contract, extend deep into the sarcoplasm, can conduct an electrical impulse. Branches of the T-tubules encircle each myofibril. |
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Term
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Definition
| Electrical impulses that trigger muscle fiber contraction |
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Term
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Definition
cylindrical structures consisting of bundles of protein filaments called myofilaments.
-anchored to the inner surface of the sarcolemma at each end of a skeletal muscle fiber |
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Term
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Definition
Membranous structure surrounding each myofibril
A membrane complex which forms a tubular network around each individual myofibril |
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Term
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Definition
| stem cells that help repair damaged muscle tissue |
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Term
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Definition
| cytoplasm of the muscle fiber |
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Term
| Myofibrils consist of bundles of ______. |
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Definition
protein filaments called myofilaments
1.thin; made of actin
2. thick; made of myosin
3. titin; elastic myofilaments associated with the thick filaments |
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Term
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Definition
| The tubules of the SR enlarge, fuse, and form expanded chambers |
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Term
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Definition
| The combination of a pair of terminal cisternae and a T-tubule |
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Term
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Definition
| A protein which reversibly binds Ca+ inside terminal cisternae |
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Term
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Definition
the smallest functional unit of a muscle fiber
Contractile units of muscle
1 myofibril contains ~10,000 sarcomeres end to end |
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Term
| What are the boundaries of a sarcomere? |
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Definition
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Term
| When does a contraction begin? |
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Definition
| When stored calcium ions are released into the cytosol. Then they diffuse into the sarcomeres. |
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Term
| What 4 proteins are in a thin filament? |
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Definition
| F-actin, nebulin, tropomyosin, and troponin |
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Term
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Definition
| A bundle of muscle fibers |
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Term
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Definition
center of the A band at midline of sarcomere
Help stabilize the positions of the thick filaments |
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Term
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Definition
lighter region on either side of M Line
Contains only thick filaments |
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Term
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Definition
| thin filaments situated between thick filaments |
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Term
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Definition
| only contains light filaments, extends from A band of 1 sarcomere to the A band of the next sarcomere |
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Term
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Definition
strands of elastic protein extend from the tips of thick filaments to attachment sites at Z line
-helps keep thick & thin filaments in proper alignment
-helps muscle fiber resist extreme stretching |
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Term
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Definition
Ca2+ binds to receptor on troponin molecule
Troponin–tropomyosin complex changes shape
Exposes active site of F-actin |
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Term
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Definition
| myosin heads interact with actin filaments, forming cross-bridges |
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Term
| The area of the A band in the sarcomere consists of ____, _____, _________. |
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Definition
| M line, H band, zone of overlap |
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Term
| Excitation-Contraction coupling overview |
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Definition
1. Release of Ca2+ from cisternae of sarcoplasmic reticulum (SR)
2. Ca2+ trigger interactions between thick & thin filaments
3. fibers contract, consume ATP
4. Produces active tension |
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Term
| Neuromuscular junction (NMJ) |
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Definition
| Each skeletal muscle fiber controlled by neuron at single NMJ midway along the fiber |
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Term
| Step 1 in neural stimulation of muscle |
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Definition
(Arrival of an action potential at the synaptic terminal)
Action potential generated
Action potential- change in transmembrane potential that travels along the axon |
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Term
| Step 2 in neural stimulation of muscle |
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Definition
(Release of acetylcholine)
Action potential reaches synaptic terminal, permeability changes in membrane trigger exocytosis of ACh into synaptic cleft |
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Term
| Step 3 in neural stimulation of muscle |
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Definition
(ACh binding at the motor end plate)
ACh molecules diffuse across the synaptic cleft & bind to ACh receptors on surface of sarcolemma at the motor end plate
ACh binding change permeability of motor end plate to Na+
(low [Na+] inside cell)
Na+ rushes into sarcoplasm |
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Term
| Step 4 in neural stimulation of muscle |
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Definition
(Appearance of an action potential)
Sudden rush of Na+ generates action potential in the sarcolemma
Originates at the edge of motor end plate, sweeps across entire membrane surface, traveling inward along each T tubule
Acetylcholinesterase removes ACh from cleft |
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Term
| Step 5 in neural stimulation of the muscle |
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Definition
(Return to initial state)
Acetylcholinesterase has removed all ACh from cleft, ready to receive next action potential |
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Term
| 1st step of contraction cycle |
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Definition
Exposure of active sites
Ca2+ binds to troponin
-Troponin changes position
-Tropomyosin rolls away
from active sites |
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Term
| 2nd step of contraction cycle |
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Definition
Formation of cross-bridges
Active sites on actin
exposed
-Myosin heads binds
-Forms cross bridges |
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Term
| 3rd step of contraction cycle |
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Definition
Pivoting of myosin heads
Myosin head cocked up
-Requires energy, ATP
-After cross-bridge is formed, stored energy is released as myosin head pivots toward M line
-Power Stroke – releases ADP & P |
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Term
| 4th step of contraction cycle |
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Definition
Detachment of cross-bridges
Another ATP binds to myosin head, link is broken between myosin & actin
-Active site is exposed & able to form another cross-bridge |
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Term
| 5th step of the contraction cycle |
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Definition
Reactivation of myosin
ree myosin head splits ATP into ADP & P, energy released is used to release the myosin head
-Entire cycle can be repeated, several times a second |
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Term
| A neuromuscular junction consists of: |
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Definition
an axon terminal of a neuron
motor end plate
synaptic cleft |
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Term
| Steps that end a contraction |
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Definition
1.Ach is broken down
2.Sarcoplasmic reticulum reabsorbs Ca2+
3. Active sites are covered, and cross-bridge formation ends
4. Contraction ends
5. Muscle relaxation occurs |
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Term
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Definition
A single stimulus-contraction-relaxation sequence in a muscle fiber
Lasts about 7–100 msec. |
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Term
| 3 phases of a single twitch |
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Definition
Latent period before contraction
--Action potential moves through sarcolemma Causing Ca2+ release
Contraction phase
--Calcium ions bind
--Tension builds to peak
Relaxation phase
--Ca2+ levels fall
--Active sites are covered
--Tension falls to resting levels |
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Term
| When Ca2+ bind to troponin, it produces a change by: |
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Definition
| Exposing the active site on the thin filaments |
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Term
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Definition
| an increase in peak tension with each successive stimulus delivered shortly after the completion of the relaxation phase of the preceding twitch |
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Term
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Definition
| when successive stimuli arrive before the relaxation phase has been completed |
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Term
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Definition
Tension production rises to a peak, periods of relaxation are very brief
muscle never relaxes completely |
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Term
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Definition
| relaxation phase is eliminated, tension plateaus at maximum levels. |
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Term
| Tension produced by whole skeletal muscles depends on ________. |
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Definition
Depends on:
Internal tension produced by muscle fibers
External tension exerted by muscle fibers on elastic extracellular fibers
Total number of muscle fibers stimulated |
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Term
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Definition
| all the muscle fibers controlled by a single motor neuron |
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Term
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Definition
resting tension in a skeletal muscle
Muscle units actively maintain body position, without motion
Increasing muscle tone increases metabolic energy used, even at rest
Adds stability, shock absorption |
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Term
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Definition
tension remains constant; muscle length increases
Concentric contraction- muscle tension > load muscle shortens (flexing)
Eccentric contraction- muscle tension < load muscle lengthens (extending) |
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Term
| motor units-precise control |
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Definition
| (eye) 1 motor neuron for 4-6 fibers |
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Term
| motor units-less precise (leg) |
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Definition
| 1 motor neuron for 1,000-2,000 fibers |
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Term
| Recruitment (multiple motor unit summation) |
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Definition
| Smooth, steady increase in muscle tension produced by increasing active number of motor units |
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Term
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Definition
Skeletal muscle develops tension, does NOT change length
Tension never exceed load
Muscle as a whole does not contract, some individual fibers do- bulge |
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Term
| A muscle producing peak tension during rapid cycles of contraction & relaxation is said to be in |
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Definition
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Term
| Adenosine triphosphate (ATP) - used for energy transfer from 1 location to another |
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Definition
At rest muscle fiber produces more ATP than it needs
ATP will transfer energy to creatine
Creatine- small molecule assembled from amino acids
Creatine phosphate (CP)- storage molecule for excess ATP energy in resting muscle |
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Term
| Aerobic metabolism of fatty acids in mitochondria |
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Definition
Glycolysis- cytoplasm
Citric acid cycle- mitochondria
Electron transport chain/oxidative
About 34 ATP |
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Term
| Anaerobic glycolysis- cytoplasm |
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Definition
Does not use oxygen
Breaks down glycogen
Energy demands high, oxygen supplies limited
about 2 ATP |
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Term
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Definition
when muscles can no longer perform a required activity
-Depletion of metabolic reserves
-Damage to sarcolemma and sarcoplasmic reticulum
-Low pH (lactic acid), decreases calcium binding to troponin
-Muscle exhaustion and pain |
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Term
Recovery period
Time required after exertion for muscles to return to normal |
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Definition
Cori Cycle- removal & recycling of lactic acid by the liver
lactic acid to pyruvic acid to glucose to glycogen
Oxygen Debt- amount of oxygen needed after exercise or other exertion to return to normal resting levels
Heat Production and Loss- active muscles produce heat, up to 70% of muscle energy can be lost as heat, raising body temperature |
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Term
| 3 types of skeletal muscle fibers |
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Definition
Fast fibers
Have large diameter, large glycogen reserves, few mitochondria
Have strong, quick contractions, fatigue quickly
Slow fibers
Slow to contract, slow to fatigue
Have small diameter, more mitochondria
Have high oxygen supply- more capillaries
Contain myoglobin (red pigment, binds oxygen)
-Intermediate fibers
Mid-sized
Have low myoglobin
Have more capillaries than fast fibers, slower to fatigue |
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Term
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Definition
| the anaerobic breakdown of glucose to pyruvate in the cytoplasm of a cell. |
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Term
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Definition
| an enlargement of the stimulated muscle |
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Term
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Definition
White muscle (sprinters)
Mostly fast fibers
Pale (chicken breast- white meat)
Red muscle (endurance runners)
Mostly slow fibers
Dark (chicken legs- dark meat)
Most human muscles
Mixed fibers
Pink |
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Term
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Definition
| a reduction in muscle tone, size, and power |
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Term
| Characteristics of cardiac muscle cells (cardiocytes) |
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Definition
Smaller with single nucleus
Short, wide T tubules- no triads
SR with no terminal cisternae
Aerobic (high in myoglobin, mitochondria)
Intercalated discs |
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Term
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Definition
Specialized contact points between cardiocytes
Join cell membranes of adjacent cardiocytes (gap junctions, desmosomes) |
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Term
| Functions of intercalated discs |
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Definition
Maintain structure
Enhance molecular and electrical connections
Conduct action potentials
Link heart cells mechanically, chemically, & electrically
Heart functions like a single, fused mass of cells |
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Term
| 4 functional characteristics of cardiac muscle |
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Definition
-Automaticity-contract without neural stimulation.Pacemaker cells determine the timing of contractions
-Nervous system can alter the pace and adjust the amount of tension produced during a contraction
-contractions last about 10 times as long, longer refracctory periods, do not readily fatigue
-twitches cannot undergo wave summation; cardiac muscle tissue cannot produce tetanic contractions |
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Term
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Definition
-Forms around other tissues
In blood vessels
-Regulates blood pressure and flow
In reproductive and glandular systems
-Produces movements
In digestive and urinary systems
-Forms sphincters, produces contractions
In integumentary system
-Arrector pili muscles cause “goose bumps” |
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Term
| Structure of smooth muscle |
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Definition
Nonstriated tissue
Different internal organization of actin & myosin
Different functional characteristics |
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Term
| 8 characteristics of smooth muscle cells |
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Definition
1.Long, slender, and spindle shaped
2.Have a single, central nucleus
3.Have no T tubules, myofibrils, or sarcomeres
4.Have no tendons or aponeuroses
5.Have scattered myosin fibers
6.Myosin fibers have more heads per thick filament
7.Have thin filaments attached to dense bodies
8.Dense bodies transmit contractions from cell to cell |
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Term
| Functional characteristics of smooth muscle |
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Definition
Excitation–contraction coupling
-Free Ca2+ in cytoplasm triggers contraction
-Ca2+ binds with calmodulin in the sarcoplasm
-Activates enzyme myosin light–chain kinase
-Enzyme breaks down ATP, initiates contraction
Length–tension relationships
-Thick and thin filaments are scattered- --no sarcomeres
-Resting length not related to tension development
-Functions over a wide range of lengths (plasticity) |
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