Chapter 10 Flashcards
skeletal muscle
muscle that covers bone. striated and voluntary
cardiac muscle
heart, striated, involuntary
smooth muscle
hollow visceral organs, non-striated and involuntary
7 skeletal functions
movement, posture, supports soft tissues, stabilizing joints, guards opening, generate heat, stores nutrients
muscle fibers
muscle cells thousands of which make up a muscle
epimysium
dense layer of collagen that surrounds the entire muscle; connects to deep fascia
perimysium
divides muscles into compartments; within each is a fascicle (a bundle of muscle fibers)
endomysium
surrounds individual muscle fibers; flexible, elastic connective tissue contains: capillaries, nerve fibers and myosatellite cells
These three layers fuse at the end of a muscle to create a tendon or aponeurosis that attaches to a bone
tendons, origin, insertion
tendons
fibrous connective tissue that merges with the periosteum of bones, connects muscles to bones or other muscles
origin
immobile bone muscle attachment
insertion
moveable bone muscle attachment, it always moves toward the origin
Muscle cells are extremely ____ and ____?
large
multinucleate
Myoblasts
primitive muscle cells that fuse during development contributing to the large size and multinuclea features
Myosatellite
myoblast cells that have NOT fused and are found in adult muscle tissue. they are stem cells that aid in muscle repair
Sarcolemma
muscle cell membrane
Sarcoplasm
the cytoplasm of a muscle cell
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
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
myofillaments
bundles of protein filaments within myofibrils, they contain; actin, myosin and titin
Actin
a THIN protein filament
contains myosin binding sites to aid in contraction; also contains troponin and tropomyosin
Myosin
a THICK protein filament. contains a myosin head which interacts with the thin filament
High amounts of ____ and ____ are found scattered among the myofibrils for high ____ production
glycongen, mitochondria, energy
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
Terminal Cisternae
expanded chambers that form when sarcoplasmic reticulum fuse
Triad
a combo of a pair of terminal cistern and a t-tubule
Sarcomeres***
know figure 10-4 and 10-5!
this is the FUNCTIONAL unit of the muscle, a chain of smaller contractile units within myofibril
A bands
the DARK bands found at the center of ea. sarcomere
M line
found in the MIDDLE of the A band; connect nerighboring thick filaments
H band
a lighter region on either side of the M line; contains thick filaments but no thin filaments
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
I bands
light bands containing thin filaments only and extend from the A band of one sarcomere to the A band of the next
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
Titin
elastic protein strands that anchor myosin to the Z line; inhibits muscles from stretching too far (stretch and recoil)
Troponin and Tropomyosin
inhibitory proteins that prevent actin from sliding with myosin
neuromuscular junction
where the motor neuron terminates on the muscle fiber; ea. muscle fiber has its own neruromuscular junction that controls it
axon terminal
enlarged tip of the motor neuron containing sacs of the neurotransmitter, acetylcholine
sarcolemma
muscle fiber cell membrane. contains recptor sites for acetylcholine (neurotransmitter) and acetycholinesterase (inacivator)
T tubules
inward folds of the sarcolemma which carry the action potential to the interior of the muscle cell
synapse
the small space between the axon terminal and the sarcolemma
During muscle contraction…. 6 steps:
- 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
Arrival of the action potential, step 1
a nerve impulse arrives at axon terminal, ACH is released into synapse
…action potential, step 2
sarcolemma receives ACH into its receptor sites and causes Na+ to rush into cell
…action potential, step 3
sarcolemma is depolarized, T-tubules bring action potential to the interior of muscle cell
…action potential, step 4
ACHE inactivates ACH
…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
…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
…action potential, step 7
all the sarcomeres shorten, muscle fiber contracts
Resting sarcomere
myosin heads are charged, pointing away from the M line
Contracted sarcomere
ATP splits and continues to ‘re-cock’ the myosin heads as long as there is sufficient calcium
How long a contraction lasts depends on what three things?
- period of stimulation at the neuromuscular junction 2. presence of calcium in the sarcoplasm 3. amount of ATP available
muscle tone
always on enables fast reaction, muscles are always in a slight state of contraction except in certain stages of sleep
Functions of muscle tone
maintains posture, helps prevent sudden changes in body movement, allows for shock absorption
Good muscle tone improves
coordination, because when muscles are slightly contracted they can react more quickly and with greater exertion
good muscle tone increases a ____ ___which can aid in ____ and ___ ____
resting metabolism, exercise and weight loss
Alternate muscle fibers ____ so the muscle does not
contract, tire out
Isotonic contraction
tension rises and a muscles length changes bringing about movement
concentric contraction
muscle tension exceeds load and muscle shortens
eccentric contraction
tension is less than the load, the muscle elongates due to the contraction of another cuscle or pull of gravity
isometric contraction
the muscle does not change load because the tension produced never exceeds the load; contraction without movement
Returning a muscle to resting length
a muscle can actively shorten but they cannot actively lengthen
elastic force
recoil to original length
opposing muscle contraction
the contraction of opposing muscles can return a muscle to its resting length
Gravity
muscles relax and gravity pulls a limb down and stretches the muscle to resting length
ATP
there is not enough stored in muscles and it is depleted quickly so it has to be generated quickly
creatine phosphate
ATP that is not being used by a resting muscle is transferred to creatine to be stored for later
Creatine Kinase
when high amounts are found in the blood concentration it indicates sever muscle damage
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
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
Anaerobic metab/glycolysis step 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
Aerobic metab. step 2 and 3
- mitochondria absorbs pyruvate
3. a CO2 molecule is removed from ea. pyruvate molecule in the mitochondria
Aerobic metab. step 4
the remainder of pyruvate enters the citric acid/krebs cycle which breaks down the pyruvate into CO2 and H+
Aerobic metab. step 5 and 6
- H+ are transferred to oxygen atoms to form water
6. all of these steps ultimately support the conversion of ADP to ATP
Every molecule of pyruvate fed into the citric acid cycle produces ____
17 ATP molecules
Muscle fatigue
when the muscle can no longer perform
normal muscle function requires (1-4)
- energy reserves, 2. circulatory supply, 3. normal blood oxygen levels, 2. normal blood PH
Muscle can fatigue due to (1-4)
- 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
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
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
Lactic acid removal/recycling, 3 facts
- during recovery oxygen levels become abundant again
- lactic acid can be converted back to pyruvate in the presence of oxygen
- pyruvate is then used to boost glycogen reserves or to generate more ATP for normal cell function
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
Recovery oxygen uptake
increase heart rate respiratory and heart rate remain high for a period of time after exercise to repay O2 debt
Types of skeletal muscle fibers
fast, slow and intermediate
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
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)
Intermediate Fibers
- appearance is closer to fast fibers (little myoglobin and appear pale)
- function is between fast and slow fibers
white muscles
dominated by fast fibers, pale, used for power
red muscles
dominated by slow fibers, blood vessels and myoglobin, give it a red color
Hypertrophy
muscle fibers increase in diameter due to increased number of myofibrils from repeated/intense stimulation
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
