A&P Ch. 9
slow-twitch (high oxidative) fibers
"dark meat" -contract more slowly, smaller fibers, good blood supply, high number of mitochondria -more fatigue resistant -aerobic respiration predominant -contain higher myoglobin; myoglobin~ Hb, stores/reservoir for O2 -myglobin increases ability of muscle to do aerobic respiration
eccentric contraction
(type of isotonic contraction) muscle lengthens and does work
myofibril
- 80% of cellular volume - contain sarcomeres
Generation of end plate potential
- ACh binding to its receptors opens ligand gated ion channels allowing Na+ and K+ to pass - more Na+ diffuses in than K+ diffuses out - sarcolemma becomes less negative --> depolarization
Repolarization: Restoring sarcolemma to its initial polarized state
- Na+ channels close and voltage-gated K+ channels open - K+ diffuses rapidly out of muscle cell bc K+ concentration was higher inside the cell - restores negatively charged conditions inside the cell - restores ELECTRICAL CONDITIONS of resting state - need ATP because active transport through sodium-potassium pump
Endomysium
- connective tissue that surrounds each muscle cell/fiber - areolar
Perimysium
- connective tissue that surrounds fascicles - fibrous
Epimysium
- connective tissue that surrounds whole muscle - dense irregular
period of relaxation
- contractile force is declining - muscle tension decreases to 0 - any shortened muscles return to initial length
Excess postexercise oxygen consumption (EPOC)
- extra amount of oxygen body must take in for restorative processes - represents difference between amount of oxygen needed for aerobic muscle activity and amount actually used
fast glycolytic fibers
- fast contraction - fast myosin ATPase activity - anaerobic glycolysis - low myoglobin content - high glycogen stores - third recruitment order - fast rate of fatigue - best suited for short-term intense or powerful movements like hitting a baseball
T Tubules
- increase muscle fiber's muscle area
Muscle Functions (5)
- movement - maintaining posture - stabilizing joints - generating heat - protect internal organs
indirect attachments
- muscle's connective tissue wrappings extend as a tendon or as aponeurosis - more common because durability and small size
Direct/Fleshy attachments
- muscle's epimysium is fused to periosteum of bone or perichondrium of cartilage
somatic motor neurons
- nerve cells that activate skeletal muscle fibers - reside in brain or spinal cord - have axons that travel to muscle cells they serve
resistance exercise
- occur in anaerobic conditions - strength is important!! - promote significant increases in muscle strength and size - can convert fast oxidative fibers to fast glycolytic fibers -
Intracellular Tubules that help regulate muscle contraction
- sarcoplasmic reticulum - T tubules
DMD- Duchenne muscular dystrophy
- sex-linked recessive disease - normal appearing children become clumsy and fall frequently as skeletal muscles weaken - caused by defective gene for dystrophin - fragile sarcolemma tears during contraction and allows entry of excess calcium
Skeletal Muscle
- striated - voluntary - longest muscle cells - overall body mobility
maximal stimulus
- strongest stimulus that increases in contractile force - all motor units are recruited
contraction
- the activation of myosin's cross bridges - ends when cross bridges become inactive
Excitation-Contraction Coupling
- transmission of action potential along sarcolemma causes myofilaments to slide
rigor mortis
- when muscles stiffen 3 to 4 hours after death - occurs because ATP is no longer present in a dead body to detach cross bridges
muscle cells/muscle fibers are _______ cm long
1-40 (14 inches)
Steps for Contraction
1. Acetylcholine released and diffuses across gap at neuromuscular junction 2. Sarcolemma is stimulated, muscle impulse travels deep into fiber through t-tubules to sarcoplasmic reticulum 3. Ca ions from Saco ret are released into sarcoplasm and bind to troponin molecules 4. tropomyosin molecules move and expose binding (active) sites on actin 5. Linkages form between actin and myosin... actin filaments slide inward along myosin filaments...muscle fiber shortens-contraction
For muscle to return to its resting state these must occur (4)
1. Its oxygen reserves in myoglobin must be replenished 2. Accumulated lactic acid must be reconverted to pyruvic acid 3. Glycogen stores must be replaced 4. ATP and creatine phosphate must be resynthesized
Three distinct phases of every twitch myogram
1. Latent period 2. Period of contraction 3. Period of relaxation
Men's skeletal muscles make up approx.. __% of body mass
42%
Which of the following is not a role of ionic calcium in muscle contraction? A) triggers neurotransmitter secretion B) promotes breakdown of glycogen and ATP synthesis C) removes contraction inhibitor D) activates epinephrine released from adrenal gland
D) activates epinephrine released from adrenal gland
What is the most distinguishing characteristic of muscle tissue? A) the design of the fibers B) the sarcoplasmic reticulum C) the diversity of activity of muscle tissue D) the ability to transform chemical energy into mechanical energy
D) the ability to transform chemical energy into mechanical energy
organ
Each skeletal muscle is a discrete ___________________, made up of several kinds of tissues.
Terminal cisternae
Enlarged portions of the sarcoplasmic reticulum; where calcium ions are stored
1st Step Cross Bridge Cycle
FORMATION - energized myosin head attaches to actin myofilament --> cross bridge
Muscle contraction will always promote movement of body parts regardless of how they are attached. True / False
False
During isotonic contraction, the heavier the load, the faster the velocity of contraction. True / False
False Isotonic - muscle lengh changes and moves the load. iso = same ton = tension
__ movements precede __ ones
Gross, fine
Multiple motor unit summation
How a smooth increase in muscle force is produced
smallest fibers to largest fibers
How are different size muscle fibers used during graded response?
Many myosin ____ make up a myosin ______
Molecules, filament
Myosin (from notes)
Most abundant muscle protein (2/3's); one molecule is made of 2 twisted protein strands with globular corssbridges (heads) that project outward
Stimulation of what causes contraction?
Motor nerve fibers
Ca2+ signal and adequate ATP are present
Muscle contraction continues as long as the
False
Muscle contraction will always promote movement of body parts regardless of how they are attached.
isometric contraction
Muscle contracts but there is no movement, muscle stays the same length (lifting a building)
True
Single-unit smooth muscle is found in the intestines.
fibrosis
damages muscle tissue is replaced by CT
A bands
dark bands
Z disc
darker area of I band interrupting its midline
The sliding filament model of contraction involves ___. a) actin and myosin sliding past each other and partially overlapping b) the shortening of thick filaments so that thin filaments slide past c) actin and myosin shortening but not sliding past each other d) the Z discs sliding over the myofilaments
a) actin and myosin sliding past each other and partially overlapping
In an isotonic contraction, the muscle ___. a) changes in length and moves the "load" b) does not change in length but increases tension c) never converts pyruvate to lactate d) rapidly resynthesizes creatine phosphate and ATP
a) changes in length and moves the "load"
Elasticity
ability of muscle cell to recoil and resume its resting length after stretching
Extensibility
ability to extend or stretch
What are the two types of myofilaments?
actin myosin
Sliding Filament Theory
actin and myosin don't change length during contraction
M line muscle
bisects H zone made up of myomesin- line of protein that holds adjacent thick filaments together
How does the nervous system achieve greater muscular force?
by increasing firing rate of motor neurons
Which of the following is "not" a way muscle contractions can be graded? a) changing the frequency of stimulation b) changing the strength of the stimulas c) changing the type of muscle fibers involved in the contraction d) changing the type of neurotransmitter released by the motor neuron
c) changing the type of muscle fibers involved in the contraction
terminal cisterns
dilated end sacs of the sarcoplasmic reticulum
Each actin strands coil to form a ____________
double helix
aerobic respiration
duration of energy provided is hours
fast-twitch fibers display more ________ with training
edurance
ATP
energy source required by muscle cells
ATPase
enzyme in myosin that breaks the ATP into DP and P so energy is released
Muscles "can" or "cannot" have both?
can
This tissue makes up the bulk of the heart.
cardiac
elastic filament
composed of the giant protein titin
muscle tone
constant tension produced by muscles over long periods of time. -keeps back/legs straight, head upright, abdoment flat -depends on small number of motor units contracting out of phase with each other
actin
contain active sites for myosin heads
There must be a high concentration of Cs ions for ____
contraction
actin and myosin filaments
contraction Results from a movement within the myofibrils, in which______slide past one another, shortening the sarcomere.
More motor units responding increases _______ and ______
contraction force, tension
muscle twitch
contraction of muscle in response to a stimulus that causes an AP in one or more fibers
myofibers (muscle cells) and sarcomere
contractions of a muscle resuts from a contraction of ____
sarcomere
Smallest contractile unit of muscle fiber; region of a myofibrils between two Z disks
there are more thick filaments than thin filaments
Smooth muscle is characterized by all of the following except ________.
Smooth muscle contracts in a twisting way.
Smooth muscle is significantly different from striated muscle in several ways. Which of the following is true?
The myosin filaments are located in the ___. a) Z discs b) I band c) Myosin d) A band
d) A band Myosin filaments are bipolar and extend throughout the A-band. They are crosslinked at the centre by the M-band.
Whic of the following is not a role of ionic calcium in muscle contraction? a) triggers neurotransmitter secretion b) promotes contraction inhibitor c) removes contraction inhibitor d) activates epinephrine released from adrenal gland
d) activates epinephrine released from adrenal gland
The main effect of the warm-up period of athletes, as the muscle contractions increase in strenth, is to ___. a) increase the myoglobin content b) convert glycogen to glucose c) tone the muscles and stabilize the joints for the workout d) enhance the availability of calcium and the efficiency of enzyme systems
d) enhance the availability of calcium and the efficiency of enzyme systems
Which of the following would be crecuited later in muscle stimulation when contractile strength increases? a) motor units with the longest muscle fibers b) many small motor units with the ability to stimulate other motor units c) large motor units with small, highly excitable neurons d) motor units with larger, less excitable neurons
d) motor units with larger, less excitable neurons
The contractile units of skeletal muscles are ___. a) microtubules b) mitochondria c) T tubules d) myofibrils
d) myofibrils
Babies' movements are ____ and ____
Uncoordinated and reflexive
insertion
When a muscle contracts, the movable bone, the muscle's __________________________, moves toward the immovable or less movable bone (the muscle's origin)
Actin (Newville)
thin filaments, where myosin heads attach during contraction; two stands twisted together
general area
varicosities release neurotransmitters into the ________________ of multiple smooth muscle cells
wave/temporal summation
when second contraction is stronger than the first and occurs before the muscle is completely relaxed - contractions are basically added together
isotonic contraction
when the developed muscle tension overcomes load and muscle shortening occurs (amount of muscle shortening is measured)
threshold stimulus
minimal level of stimulation required to activate a motor unit
muscles which generate more powerful movements have motor units with ______ number of muscle fibers, which results in more power/strength
more
cross bridge
myosin head + active site of actin
What happens when a muscle fiber stretches so much that filaments don't overlap?
myosin heads have nothing to attach to and cannot generate tension
motor neurons
nerve cells that propagate action potentials (APs) to skeletal muscle
Muscles are sometimes analyze as a result of damage to the ____ that are associated with them.
nerves
axons of motor units combine to form _______
nerves
diffuse junctions
neurotransmitter signals diffuse to adjacent smooth muscle cells via ____________________________; creates ripples of stimulus
oxygen debt
oxygen required after intense activity to reestablish normal concentration of creatine phosphate, ATP and to convert lactic acid---> pyruvate (within liver) -pyruvate-->glucose-->glycogen conversion restores [glycogen] in liver and muscle
cramps
painful, spastic contractions; caused by increased [lactic acid] and fibrositis
synaptic cleft
physical gap between synaptic knob and sarcolemma
sarcoplasma
plasma in sarcolema
sarcolemma
plasma membrane of muscle fiber
anaerobic threshold
point at which muscle metabolism converts to anaerobic glycolysis
neuromuscular junction
point of contact between a motor neuron and a skeletal muscle cell
maintaining body position, stabilizing joints, heat generation
secondary functions of muscle tissue
_____ muscle tissue is found into the walls of hollow internal organs
smooth
hormones
smooth muscle doesn't have to have a nervous signal, it can be signaled by ____________________
muscle fatigue
state of physiological inability to contract even though the muscle still may be receiving stimuli
direct (or fleshy) attachments
the epimysium of the muscle is fused to the periosteum of a bone or perichondrium of a cartilage.
cross bridges (Newville)
thick and thin filaments link during contractions; act as motors to create the tension developed by a contracting muscle cell ->***link that forms between actin and myosin****
Muscular dystrophy
Inherited muscle-destroying diseases that appear in childhood; initially enlarge (due to fat) but then atrophy
______ ____ are found between the cells of cardiac muscle tissue.
Intercalated disks
What may cause muscle fatigue?
Ionic imbalances - accumulation of Pi that may interfere with calcium release from SR or release of Pi from myosin and hamper power strokes - lactic acid --> raises concentration of H+ and alters contractile proteins and also counteracts high K+ levels
What happens when CA ions bind to troponin?
It changes the position of the tropomyosin and they move so that the active sites of actin are exposed and then linkages can form between actin and myosin filaments
entire, isn't activated
It is important that all connective tissue in a muscle work as a single piece so that the ___________________ muscle an contract even if every muscle fiber ______________ isn't activated.
One of the important functions of skeletal muscle contraction is a production of heat. True / False
True Muscles perform at least four functions: movement, maintains posture, stabilize joints and generates heat.
Peristalsis is characteristic of smooth muscle. True / False
True Peristalsis - the wavelike muscular contraction of the intestine or other tubular structure that propel the contents onward by alternate contraction and relaxation.
Single-unit smooth muscle is found in the intestines. True / False
True Single-unit smooth muscle, commonly called visceral muscle because it is in the walls of all hollow organs except the heart.
Although there are "no" sacromeres, smooth muscle still possesses thick and thin filaments. True / False
True sacromere = muscle segment The smallest contractile unit of a muscle fiber.
Endomysium
Whisky fine areolar connective tissue sheath around each individual muscle fiery; sheaths are continuous with each other; when muscle fibers contract, pull on sheath, pull on bone to be moved
allows for refined movement and more control
Why do muscles associated with finer movements contain more motor units (fewer fibers per unit)?
signals need a place to die
Why is it necessary to avoid direct connection between neuron and muscle fiber?
diffusion rate of calcium from the sarcoplasmic reticulum to sarcomere
Why is muscle contraction not an immediate process?
muscle fibers degenerate and atrophy
With muscular dystrophy ________.
glucose, fats and/or proteins
You have enough _____________________ to power your muscles for 30 - 50 minutes, after that you start processing _____________________
Red
________ (color) fibers are slow (oxidative) fibers.
ionic calcium
____________________ signals the release of acetylcholine (neurotransmitter) into the synaptic cleft
Most skeletal muscle contain ___. a) muscle fibers of the same type b) a mixture of fiber types c) a predominance of slow oxidative fibers d) a prejdominance of fast oxidative fibers
b) a mixture of fiber types
During muscle contraction, myosin across bridges attach to which active sites? a) myosin filaments b) actin filaments c) Z discs d) thick filaments
b) actin filaments
What is the functional role fo theT tubules? a) stabilize the G and F actin b) enhance cellular communication during muscle contraction c) hold cross bridges in place in a resting muscle d) synthesize ATP to provide energy for muscle contraction
b) enhance cellular communication during muscle contraction
Cardiac muscle
branched fibers, striated ~mononucleate, intercalated disks, autorhythmic, depolarization involves Na+/Ca2+ movement
atrophy
break down muscle
fast glycolytic fibers
fast contraction, anaerobic glycolysis, low myoglobin, white, few mitochondria, best suited for short-term intense or powerful movements
fascia
fiberous connective tissue outside of epimysium
slow-twitch fibers generate more _______ with training
force
active tension
force applied to object to be lifted when muscle contrats -as length of muscle increases, its active tension also increases -provides optimal overlap of actin/myosin filamentsl; x-bridge formation causes maximal contraction
muscle tension
force exerted by contracting muscle on an object
terminal cisterns
form larger, perpendicular cross channels at the a band -i band junction and always occur in pairs- expanded ends
multiunit smooth muscle
found as sheets (blood vessel walls), in small bundles (arrector pili) or as single cells (spleen) -contractions only when stimulated, few gap junctions
visceral/unitary smooth muscle
found in GI, reproductive and urinary tracts -occurs in "sheets", equipped with gap junctions (functional synctium) -some is autorhythmic (GI tract), some must be stimulated (bladder)
smooth muscle tissue
found in the walls of hollow visceral organs, its role is to force fluids and other substances through internal body channels, consists of elongated cells, has no striations, involuntary
excitability, contractibility, extensibility, elasticity
four characteristics associated with all muscle tissue
sacromere
functional unit of muscle
sarcomere
functional unit of muscle contraction
Glucose is stored into the form of___
glycogen
whole muscles respond in a ______ rather than all-or-none fashion
graded
glycosome
granules of stored glycogen in the sarcoplasm that provide glucose during muscle cell activity
Fascicle
grouped muscle fibers
excitation contraction coupling
mechanism by which AP results in muscle contraction
poliomyelitis
motor unit destruction, causes loss of muscle function in fibers innervated by destroyed nerves
muscle twitch
motor unit's response to single action potential of its motor neuron
power stroke
movement of myosin head while x-bridge is in place
muscle tension
muscle contraction leads to the generation of force or
skeletal muscle tissue
muscle fibers that are the longest muscle cells, and have obvious striations, often activated by reflexes, but mostly subject to conscious control
cardiac
muscle tissue type with branched cells
ATP is stored within the ______ head
myosin
Each G-actin monomer has a binding site for _______
myosin
subthreshold stimulus
no action potential produced, no resultant contraction
cardiac muscle tissue
occurs only in the heart, striated, involuntary (contracts without being stimulated by the nervous system)
motor unit
one motor neuron + muscle fibers it innervates - motor neuron fires --> all associated muscle fibers contract
load
opposing force exerted on muscle by weight of the object to be moved
perimysium
surrounds a bundle (fascicle) of muscle fibers
unfused/ incomplete tetanus
sustained but quivering contraction after degree of wave summation becomes greater and greater
isometric muscle contraction
tension increases during contraction but length of muscles does not. -contractions exhibited by postural muscles
elasticity
the ability of a muscle cell to recoil and resume its resting length after stretching
____ is a byproduct of cellular respiration
heat
True
The effect of a neurotransmitter on the muscle cell membrane is to modify its ion permeability properties temporarily.
muscle relaxation
Ca2+ reabsorbed into sarcoplasm reticulum
Why are muscles not infected easily?
Rich blood supply
Gap junction is aka ____
Synaptic clefts
I band
The ________ contains only the actin filaments.
creatine phosphate
stores energy, used to replenish ATP supply
voltage increases
what triggers additional motor unit recruitment?
Step 4 causes generation of an action potential in the muscle cell
which leads to release of Ca2+ ions from SR into sarcoplasm and eventually muscle contraction.
_______ muscles are composed of many motor units
whole
receive nervous system stimulation differently
why is smooth muscle incapable of strong contractions?
Excitability/Responsiveness
- ability to receive and respond to stimulus - stimulus=usually a chemical with muscles
refractory period
-during repolarization -cell cannot be stimulated again until repolarization is complete - repolarization restores ELECTRICAL CONDITIONS of resting state Na+-K+ pumps restores IONIC CONDITIONS of resting state
Which of the following is true about smooth muscle contraction? A) Certain smooth muscle cells can actually divide to increase their numbers. B) Smooth muscle, in contrast to skeletal muscle, cannot synthesize or secrete any connective tissue elements. C) Smooth muscle cannot stretch as much as skeletal muscle. D) Smooth muscle has well-developed T tubules at the site of invagination.
A) Certain smooth muscle cells can actually divide to increase their numbers.
Of the following muscle types, which has only one nucleus, no sarcomeres, and rare gap junctions? A) visceral smooth muscle B) multiunit smooth muscle C) cardiac muscle D) skeletal muscle
B) multiunit smooth muscle
The muscle cell membrane is called the ________. A) endomysium B) sarcolemma C) perimysium D) epimysium
B) sarcolemma
presence or absence of sarcomers
Banding is caused by ___________________
Which of the following statements is true? A) Cardiac muscle cells have many nuclei. B) Smooth muscle cells have T tubules. C) Striated muscle cells are long and cylindrical with many nuclei. D) Cardiac muscle cells are found in the heart and large blood vessels.
C) Striated muscle cells are long and cylindrical with many nuclei.
Which of the following describes the cells of single-unit visceral muscle? A) They contract all at once. B) They are chemically coupled to one another by gap junctions. C) They exhibit spontaneous action potentials. D) They consist of muscle fibers that are structurally independent of each other.
C) They exhibit spontaneous action potentials.
Muscle tone is ________. A) the ability of a muscle to efficiently cause skeletal movements B) the feeling of well-being following exercise C) a state of sustained partial contraction D) the condition of athletes after intensive training
C) a state of sustained partial contraction
The oxygen-binding protein found in muscle cells is ________. A) hemoglobin B) ATP C) myoglobin D) immunoglobin
C) myoglobin
cross bridges (from notes)
In the presence of Ca (calcium) ions react with actin filaments and shorten the myofibrils - contraction; contain ATP binding sites
What are the three types of muscle tissue?
Skeletal, cardiac, smooth
refractory period
When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods?
contraction
active process, ATP required
An enaerobic metabolic pathway that results in the productionof two net ATPs per glucose plus tow pyruvic acid molecules is ___. a) the citric acid cycle b) glycolysis c) hydrolysis d) the electron transport chain
b) glycolysis
The oxygen-binding protein found in muscle cells is ___. a) hemoglobin b) ATP c) myoglobin d) immunoglonin
c) myoglobin
triad
grouping of 2 terminal cisternae with T tubule in between
troponin
has 3 binding sites: 1 for actin, 1 for tropomyosin, 1 for Ca2+
I bands
light bands
H zone
lighter region in midsection of A band
dystrophin
links thin filaments to proteins of sarcolemma
endomysium
loose connective tissue surrounding muscle fibers (outside external lamina)
subthreshold stimuli
no observable contractions
myo, mys, sarco
prefixes that reference muscle
myogram
recording of contractile activity
energy economy
smooth muscle has improved ___________________ over skeletal muscles; they don't provide as strong of contractions, but they don't need as much energy
reduce energy need
smooth muscle myofilaments can connect to each other during prolonged contractions to ______________________
cardiac and smooth
uninucleate muscle tissue types
aerobic/endurance exercise (swimming, jogging, fast walking, biking)
- # of capillaries surrounding muscle fibers increases - number of mitochondria within muscle fibers increases - fibers synthesize more myoglobin - most dramatic in slow oxidative fibers - changes = greater endurance, strength, and resistance to fatigue
As muscle shortens:
- I bands shorten - distance between Z discs shortens - H zones disappear - contiguous A bands move closer (length doesn't change)
Depolarization: Generation and propagation of an action potential
- Na+ enters - action potential is generated if threshold is reached - action potential propagates and spreads to adjacent areas of sarcolemma - opens voltage-gated Na channels - Na+ diffuses into cell following electrochemical gradient (more Na+ going in than K+ going out)
elastic filament
- composed of titin - holds thick filaments in place = maintains organization of A band - helps muscle recoil
fused/complete tetanus
- contractions fuse into smooth, sustained contraction plateau after frequency continues to increase then muscle tension increases and reaches maximal tension - does not happen often like on the rare occasions someone shows superhuman strength
recruitment aka multiple motor unit summation
- controls force of contraction more precisely - achieves more smooth, continuous muscle contractions
period of contraction
- cross bridges are active - if tension becomes great enough to overcome resistance of load, muscle shortens
sliding filament model of contraction
- during stimulation: myosin heads latch onto actin and sliding begins - cross bridge attachments form and break several times to propel thin filaments towards center of sarcomere
fast oxidative fibers
- fast contraction - fast myosin ATPase activity - mostly aerobic pathway for ATP synthesis - high myoglobin content - intermediate glycogen stores - 2nd recruitment order - intermediate rate of fatigue - best suited for sprinting or walking
For a muscle cell to contract (4)
- fiber must be stimulated by nerve ending so that membrane potential changes - must generate an action potential in sarcolemma - action potential propagates along sarcolemma - intracellular Ca ions must rise briefly --> final trigger for contraction
muscular dystrophy
- group of inherited muscle-destroying diseases - affected muscles enlarge due to deposits of fat and connective tissue but muscle fibers atrophy and degenerate
creatine phosphate
- high energy molecule tapped to regenerate ATP - CP + ADP --> creatine + ATP
Smooth Muscle
- in walls of hollow organs (stomach, bladder, respiratory passages) - force substances through internal body channels - no striations - involuntary - slow and sustained contractions - only has endomysium
thick filaments
- mainly composed of myosin molecules - head has actin and ATP binding sites
How motor neuron stimulates a skeletal muscle fiber
- nerve impulse reaches end of axon - axon terminal releases ACh into synaptic cleft - ACh diffuses across cleft - ACh attaches to ACh receptors on sarcolemma of muscle fiber - ACh binding --> electrical events --> action potential
Cardiac Muscle
- only in the heart - striated - involuntary - can and usually contracts without nervous system stimulation
slow oxidative fibers
- slow contraction - slow myosin ATPase activity - aerobic pathway for ATP synthesis - high myoglobin content - low glycogen stores - first recruitment order - slow rate of fatigue (fatigue-resistant) - best suited for endurance type activities
sarcomeres
- smallest contractile elements of skeletal muscle cells - contain myofilaments - contains A band flanked by half an I band at each end - region of myofibril between 2 successive Z discs
Sarcoplasmic reticulum
- smooth ER of muscle fibers - regulates intracellular levels of ionic calcium - stores calcium and releases it on demand when muscle fiber is stimulated
graded muscle responses
- variations in healthy muscle contractions - grades muscle contraction by changing frequency of stimulation and changing strength of simulation
muscle tone
- when relaxed muscles are almost always slightly contracted - due to spinal reflexes that activate first one group of motor units then another in response to activated stretch receptors - does not produce active movements - keeps muscles firm, healthy, and ready to respond - skeletal tone helps stabilize joints and maintain posture
Things that happen in excitation contraction coupling
-AP reached T-tubules (carries depolarization to interior of muscle fibers) -Ca2+ diffuses into sarcoplasm surrounding myofibrils -Ca2+ binds to troponin -troponin-tropomyosin complex "moves" deeper into groove between 2 F-actin molecules -active site on actin is exposed -actin-myosin x-bridge form
Things that happen in muscle relaxation
-Ca2+ leaves troponin -troponin/tropomyosin move back into resting position -actin active site in covered up
Special Characteristics of Muscle Tissue (4)
-Excitability -Contractility -Extensibility -Elasticity
anaerobic pathway
3rd energy reserve course - about 1 minute; required no oxygen; useful for short, high-tensity load; wasteful; lasts about a minute max (text says 30 - 40 seconds)
FOURTH channel involved in initiating muscle contraction
4. AP transmission along T tubules --> changes conformation of voltage-sensitive proteins in them --> stimulates SR calcium release channels to release Ca 2+ into cytosol
aerobic pathway
4th energy reserve course; - responsible for all long-term muscle energy needs; requires oxygen, very productive, but slow to make.
Muscle strength has usually decreased by ___% at 80 y/o
50%
There are ___ actin molecules of every 1 myosin molecule.
6
Which of the following statements is most accurate? A) Muscle tension remains relatively constant during isotonic contraction. B) T tubules may be sliding during isotonic contraction. C) The I band lengthens during isotonic contraction. D) Myofilaments slide during isometric contractions.
A) Muscle tension remains relatively constant during isotonic contraction.
What is the functional unit of a skeletal muscle called? A) a sarcomere B) a myofilament C) a myofibril D) the sarcoplasmic reticulum
A) a sarcomere
The sliding filament model of contraction involves ________. A) actin and myosin sliding past each other and partially overlapping B) the shortening of thick filaments so that thin filaments slide past C) actin and myosin shortening but not sliding past each other D) the Z discs sliding over the myofilaments
A) actin and myosin sliding past each other and partially overlapping
In an isotonic contraction, the muscle ________. A) changes in length and moves the "load" B) does not change in length but increases tension C) never converts pyruvate to lactate D) rapidly resynthesizes creatine phosphate and ATP
A) changes in length and moves the "load"
What part of the sarcolemma contains acetylcholine receptors? A) motor end plate B) end of the muscle fiber C) part adjacent to another muscle cell D) any part of the sarcolemma
A) motor end plate
Which of the following is the correct sequence of events for muscle contractions? A) motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke, sliding of myofilaments B) neurotransmitter release, muscle cell action potential, motor neuron action potential, release of calcium ions from SR, sliding of myofilaments, ATP-driven power stroke C) muscle cell action potential, neurotransmitter release, ATP-driven power stroke, calcium ion release from SR, sliding of myofilaments D) neurotransmitter release, motor neuron action potential, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke
A) motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke, sliding of myofilaments
What structure in skeletal muscle cells functions in calcium storage? A) sarcoplasmic reticulum B) mitochondria C) intermediate filament network D) myofibrillar network
A) sarcoplasmic reticulum
Muscle tissue has all of the following properties except ________. A) secretion B) contractility C) extensibility D) excitability
A) secretion
Equation for formation of ATP
ATP <=> ADP + P + energy
ATPase breaks down ______
ATP---> ADP+Pi
Elasticity
Ability of a muscle cell to recoil and resume resting length after being streched
Extensibility
Ability to be stretched or extended 1. Cell shorten when contracting 2. But can be stretched when relaxing
Excitability/Responsiveness/irritability
Ability to receive and respond to a stimulus (usually a chemical); the response is "conductivity"
Contractility
Ability to shorten forcibly when stimulated; sets muscles abort from others (muscles are only tissue with this ability)
flaccid paralysis
Ach can't bind to receptor at NM junction therefore muscle doesn't contract -e.g., curare, binds to Ach receptors at NM junction
spastic paralysis
Ach is not degraded and accumulates at synapse -muscle contracts/can't relax -e.g., organophosphate pesticides
What is the role of tropomyosin in skeletal muscles? A) Tropomyosin is the name of a contracting unit. B) Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules. C) Tropomyosin serves as a contraction inhibitor by blocking the actin binding sites on the myosin molecules. D) Tropomyosin is the receptor for the motor neuron neurotransmitter.
B) Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules.
The term aponeurosis refers to ________. A) the bands of myofibrils B) a sheetlike indirect attachment to a skeletal element C) the rough endoplasmic reticulum D) the tropomyosin-troponin complex
B) a sheetlike indirect attachment to a skeletal element
During muscle contraction, myosin cross bridges attach to which active sites? A) myosin filaments B) actin filaments C) Z discs D) thick filaments
B) actin filaments
Which of the following surrounds the individual muscle cell? A) perimysium B) endomysium C) epimysium D) fascicle
B) endomysium
What is the functional role of the T tubules? A) stabilize the G and F actin B) enhance cellular communication during muscle contraction C) hold cross bridges in place in a resting muscle D) synthesize ATP to provide energy for muscle contraction
B) enhance cellular communication during muscle contraction
An anaerobic metabolic pathway that results in the production of two net ATPs per glucose plus two pyruvic acid molecules is ________. A) the citric acid cycle B) glycolysis C) hydrolysis D) the electron transport chain
B) glycolysis
What controls the force of muscle contraction? A) wave summation B) multimotor unit summation C) treppe D) concentric contractions
B) multimotor unit summation
Smooth muscles that act like skeletal muscles but are controlled by autonomic nerves and hormones are ________. A) single-unit muscles B) multiunit muscles C) red muscles D) white muscles
B) multiunit muscles
Hypothetically, if a muscle were stretched to the point where thick and thin filaments no longer overlapped, ________. A) cross bridge attachment would be optimum because of all the free binding sites on actin B) no muscle tension could be generated C) maximum force production would result because the muscle has a maximum range of travel D) ATP consumption would increase because the sarcomere is "trying" to contract
B) no muscle tension could be generated
When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods? A) relaxation period B) refractory period C) latent period D) fatigue period
B) refractory period
What produces the striations of a skeletal muscle cell? A) a difference in the thickness of the sarcolemma B) the arrangement of myofilaments C) the sarcoplasmic reticulum D) the T tubules
B) the arrangement of myofilaments
What does oxygen deficit represent? A) amount of energy needed for exertion B) the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used C) the amount of oxygen taken into the body prior to the exertion D) the amount of oxygen taken into the body immediately after the exertion
B) the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used
M lines
Bisect H zones vertically; myosin linked by accessory proteins
Which of the following statements is false or incorrect? A) Cardiac muscle contracts when stimulated by its own autorhythmic muscle cells. B) Under normal resting conditions, cardiac muscle tissue contracts and relaxes about 75 times per minute. C) Cardiac muscle fibers depend mostly on anaerobic cellular respiration to generate ATP. D) Cardiac muscle fibers can use lactic acid to make ATP.
C) Cardiac muscle fibers depend mostly on anaerobic cellular respiration to generate ATP.
After nervous stimulation stops, what prevents ACh in the synaptic cleft from continuing to stimulate contraction? A) calcium ions returning to the terminal cisternae B) the tropomyosin blocking the myosin once full contraction is achieved C) acetylcholinesterase destroying the ACh D) the action potential stops going down the overloaded T tubules
C) acetylcholinesterase destroying the ACh
What is the role of calcium ions in muscle contraction? A) form hydroxyapatite crystals B) reestablish glycogen stores C) bind to regulatory sites on troponin to remove contraction inhibition D) increase levels of myoglobin
C) bind to regulatory sites on troponin to remove contraction inhibition
Which of the following is not a way muscle contractions can be graded? A) changing the frequency of stimulation B) changing the strength of the stimulus C) changing the type of muscle fibers involved in the contraction D) changing the type of neurotransmitter released by the motor neuron
C) changing the type of muscle fibers involved in the contraction
Which of the following is not a usual result of resistance exercise? A) increase in the efficiency of the respiratory system B) increase in the efficiency of the circulatory system C) increase in the number of muscle cells D) increase in the number of myofibrils within the muscle cells
C) increase in the number of muscle cells
Which of the choices below does not describe how recovery oxygen uptake (oxygen deficit) restores metabolic conditions? A) converts lactic acid back into glycogen stores in the liver B) resynthesizes creatine phosphate and ATP in muscle fibers C) increases the level of lactic acid in the muscle D) replaces the oxygen removed from myoglobin
C) increases the level of lactic acid in the muscle
The strongest muscle contractions are normally achieved by ________. A) increasing stimulus above the threshold B) increasing stimulus above the treppe stimulus C) increasing the stimulation up to the maximal stimulus D) recruiting small and medium muscle fibers
C) increasing the stimulation up to the maximal stimulus
Which of the following is a factor that affects the velocity and duration of muscle contraction? A) number of muscle fibers stimulated B) size of the muscle fibers stimulated C) load on the fiber D) muscle length
C) load on the fiber
Which muscle cells have the greatest ability to regenerate? A) skeletal B) cardiac C) smooth D) no muscle can regenerate
C) smooth
Myoglobin ________. A) breaks down glycogen B) is a protein involved in the direct phosphorylation of ADP C) stores oxygen in muscle cells D) produces the end plate potential
C) stores oxygen in muscle cells
The warm-up period required of athletes in order to bring their muscles to peak performance is called ________. A) twitch B) wave summation C) treppe D) incomplete tetanus
C) treppe
4th Step Cross Bridge Cycle
COCKING OF MYOSIN HEAD - ATP hydrolyzed --> ADP + Pi - myosin returns to cocked position (high energy)
troponin
Calcium ions bind to the ________ molecule in skeletal muscle cells.
The main effect of the warm-up period of athletes, as the muscle contractions increase in strength, is to ________. A) increase the myoglobin content B) convert glycogen to glucose C) tone the muscles and stabilize the joints for the workout D) enhance the availability of calcium and the efficiency of enzyme systems
D) enhance the availability of calcium and the efficiency of enzyme systems
During vigorous exercise, there may be insufficient oxygen available to completely break down pyruvic acid for energy. As a result, the pyruvic acid is converted to ________. A) a strong base B) stearic acid C) hydrochloric acid D) lactic acid
D) lactic acid
Which of the following would be recruited later in muscle stimulation when contractile strength increases? A) motor units with the longest muscle fibers B) many small motor units with the ability to stimulate other motor units C) large motor units with small, highly excitable neurons D) motor units with larger, less excitable neurons
D) motor units with larger, less excitable neurons
The contractile units of skeletal muscles are ________. A) microtubules B) mitochondria C) T tubules D) myofibrils
D) myofibrils
The major function of the sarcoplasmic reticulum in muscle contraction is to ________. A) make and store phosphocreatine B) synthesize actin and myosin myofilaments C) provide a source of myosin for the contraction process D) regulate intracellular calcium concentration
D) regulate intracellular calcium concentration
Creatine phosphate functions in the muscle cell by ________. A) forming a temporary chemical compound with myosin B) forming a chemical compound with actin C) inducing a conformational change in the myofilaments D) storing energy that will be transferred to ADP to resynthesize ATP
D) storing energy that will be transferred to ADP to resynthesize ATP
Z line/disc
Darker midline bisecting in I bands; actin form one sarcomere connects to actin of next
atrophy
Decrease in size/muscle mass
Fatigue occurs when ATP production fails to keep pace with ATP use even though the muscle still receives stimuli.
Define physiologic muscle fatigue.
Acetylcholinesterase
Destroys ACh.
acetylcholinesterase
In the synaptic cleft of a neuromuscular junction, an enzyme called ________ is always present.
Smooth Muscle
In walls of visceral organs: hollow organs Involuntary No striations Slow, sustained rate of contraction (turtle)
As we age, our amount of connective tissue _____and number of muscle fibers ___
Increases, decreases
durability and small size
Indirect attachments are much more common because of their ________________________________________.
a state of sustained partial contraction
Muscle tone is ________.
The effect of a neurotransmitter on the muscle cell membrane is to modify its ion permeability properties temporarily T/F
True
The force of muscle contraction is controlled by multiple motor unit summation or recruitment. True / False
True
The thin filaments (actin) contain a polypeptide subunit G actin that bears active sites for myosin attachment. True / False
True
When a muscle fiber contracts, the I bands diminish in size, the H zones disappear, and the A bands move closer together but do not diminish in length. True / False
True
Excitation-contraction coupling requires which of the following substances? a) Ca2+ and ATP b) Ca2+ only c) ATP only d) ATP and glucose
a) Ca2+ and ATP
Which of the following is true about smooth muscle contraction? a) Certain smooth muscle cells can actually divide to increase their numbers. b) Smooth muscle, in contrast to skeletal muscle, cannot synthesize or secrete any connective tissue elements. c) Smooth muscle cannot stretch as much as skeletal muscle. d) Smooth muslce has well-developed T tubules a the site of invagination.
a) Certain smooth muscle cells can actually divide to increase their numbers.
Which of the following statements is most accurate? a) Muscle tension remains relatively constant during isotonic contraction. b) T tubules may be sliding during isotonic contraction. c) The I band lengthens during isotonic contraction. d) Myofilaments slide during isometric contractions.
a) Muscle tension remains relatively constant during isotonic contraction.
Which of the following is the correct sequence of events for muscle contractions? a) motor neuron action potential, meurotransmitter release, muscle cell action potential, release of calcium ions from SR, AtP-driven power stroke, sliding of myofilaments b) neurotransmitter release, muscle cell action potential, motor reuron action potential, release of calcium ions from SR, sliding of myofilaments, ATP-driven power stroke c) muslce cell action potential, neurotransmitter release, atp-driven power stroke, calcium ion release from SR, sliding of myofilaments d) neurotransmitter rlease, motor neuron cation potential, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke
a) motor neuron action potential, meurotransmitter release, muscle cell action potential, release of calcium ions from SR, AtP-driven power stroke, sliding of myofilaments
What structure in skeletal muscle cells functions in calcium storage? a) sacroplasmic reticulum b) mitochondria c) intermediate filament network d) myofibrillar network
a) sacroplasmic reticulum SR is an elaborate smooth endoplasmic reticulum. Its interconnecting tubules surrounds each myofibril the way a sleeve surrounds your arm.
Muscle tissue has all of the following properties except ___. a) secretion b) contractility c) extensibility d) excitability
a) secretion
Which of the following are composed of myosin? a) thick filaments b) thin filaments c) all myofilaments d) Z discs
a) thick filaments Thick filaments containing myosin (red). Thin filaments containing actin (blue).
above-threshold stimulus
action potential is produces, muscle contraction of the same magnitude as that produced by threshold stimulus results
striations
alternate dark and light bands found on skeletal and cardiac muscle; made of dark A bands and light I bands
passive tension
applied to the load when a muscle is stretched but not stimulated -due to the elasticity of muscle and its connective tissue
Three discrete types of muscle fibers are identified on the basis of their size, speed, and endurance. Which of the following athletic endeavors best represents the use of red fibers? a) a sprint by an Olympic runner b) a long, relaxing swim c) plaoying baseball or basketball d) mountain climbing
b) a long, relaxing swim
Which of the following surrounds the individual muscle cells? a) perimysium b) endomysium c) epimysium d) fascicle
b) endomysium Endomysium = within the muscle. Is a whispy sheath of connective tissue that surrounds each individual muscle fiber.
Fatigued muscle cells that recover rapidly are the products of ___. a) intense exercise of long duration b) intense exercise of short duration c) slow exercise of long duration d) slow exercise of short duration
b) intense exercise of short duration
Of the following muscle types, which has only one nucleus, no sacromeres, and rare gap junctions? a) visceral smooth muscle b) multiunit smooth muscle c) cardiac muscle d) skeletal muscle
b) multiunit smooth muscle
When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods? a) relaxation period b) refractory period c) latent period d) fatigue period
b) refractory period During repolarization, a muscle fiber is in the refractory period, because the cell cannot be stimulated again until repolarization is complete. Repolarization - the sarcolemma is restored to its initial polarized state. sarcolemma = plasma membrane
What does oxygen deficit reporesent? a) amount of energy needed for exertion b) the differnce between the amount of oxygen needed for totally aerobic muscle activity and the amound actually used. c) the amount of oxygen taken into the body prior to exertion d) the amount of oxygen taken into the body immediatly after the exertion
b) the differnce between the amount of oxygen needed for totally aerobic muscle activity and the amound actually used.
Smooth muscle is charaterized by all of the following except ___. a) it appears to lack troponin b) there are more thick filaments than thin filaments c) there are no sarcomeres d) there are noncontractile intermediate filaments taht attach to dense bodies within the cell
b) there are more thick filaments than thin filaments
tropomyosin
block myosin binding sites of actin
Which of the following statements is false or incorrect? a) Cardiac muscle contracts when stimulated by its own autorhythmic muscle cells. b) Under normal resting conditions, cardiac muscle tissue contracts and relaxes about 75 times per minute. c) Cardiac muscle fibers depend mostly on anaerobic cellular respiration to generate ATP. d) Cardiac muscle fibers can use lactic acid to make ATP
c) Cardiac muscle fibers depend mostly on anaerobic cellular respiration to generate ATP.
Which of the following statements is true? a) Cardiac muscle cells have many nuclei. b) Smooth muscle cells have T tubules. c) Striated muscle cells are long and cylindrical with many nuclei. d) Cardiac muscle cells are found in the heart and large blood vessels.
c) Striated muscle cells are long and cylindrical with many nuclei.
Muslce tone is ___. a) the ability of a muscle to efficiently cause skeletal movements b) the feeling of well-being following exercise c) a state of susteained partial contraction d) the condition of athletes after intensive training
c) a state of susteained partial contraction
Which of the following is "not" a result of resistance exercise? a) increase in the efficiency of the respiratory system b) increase in the efficiency of the circulatory system c) increase in the number of muscle cells d) increase in thenumber of myofibrils within the muscle cells
c) increase in the number of muscle cells
Which of the choices below does "not" describe how recovery oxygen uptake (oxygen deficit) restores metabolic conditions? a) converts lactic acid back into glycogen stores in the liver b) resynthesizes creatine phosphate and ATP in muscle fibers c) increases the level of lactic acid in the muscle d) replaces the oxygen removed from myoglobin
c) increases the level of lactic acid in the muscle
The strongest muscle contractions are normally achieved by ___. a) increasing stimulus above the threshold b) increasing stimulus above the treppe stimulus c) increasing the stimulation up to the maximal stimulus d) recruiting small and medium muscle fibers
c) increasing the stimulation up to the maximal stimulus
Immediately following the arival of the stimulus at a skeletal muscle cell there is a short period called the ___ period during which the events of excitation-contraction coupling occur. a) contraction b) relaxation c) latent d) refractory
c) latent Latent period - the first few millaseconds following stimulation when excitation-contraction coupling is occuring.
Which of the following is a factor that affects the velocity and duration of muscle contraction? a) number of muscle fibers stimulated b) size of the muscle fibers stimulated c) load on the fiber d) muscle length
c) load on the fiber
Rigor mortis occurs because ___. a) the cells are dead b) sodium oions leak out of the muscle c) no ATP is available to release attached actin and myosin molecules d) proteins are beginning to break down, thus preventing a flow of calcium ions
c) no ATP is available to release attached actin and myosin molecules
Myoglobin ___. a) breaks down glycogen b) is a protein involved in the direct phosphorylation of ADP c) stores oxygen in muscle cells d) produces the end plate protential
c) stores oxygen in muscle cells
The mechanism of contraction in smooth muscle is different from skeletal muscle in that ___. a) actin and myosin interact by the sliding filament mechanism b) the trigger for contraction is a rise in intracellular calcium c) the site of calcium regulation differs d) ATP energizes the sliding process
c) the site of calcium regulation differs
Which of the following describes the cells of single-unit visceral muscle? a) they contract all at once. b) They are chemically coupled to one another by gap junctions. c) they exhibit spontaneous action potentials. d) They consist of muscle fibers that are structurally independent of each other.
c) they exhibit spontaneous action potentials.
motor unit
combination of each axon and all associated muscle fibers; contract in unison
thin filaments
composed of actin, extend across the I band and partway into the A band
thin filaments
composed of actin, tropomyosin, and troponin
thick filaments
composed of myosin; extend the entire length of the A band
latent period
cross bridges begin to cycle but muscle tension is not yet measurable
Ach
crosses synaptic cleft and binds to Ach receptors on the motor end plate
sarcoplasm
cytoplasm of a muscle cell; contains unusually large amounts of glycosomes and myoglobin
sarcoplasm
cytoplasm of muscle cell
Creatine phosphate functions in themuscle cell by ___. a) forming a temporary chemical compound with myosin b) forming a chemical compound with actin c) inducing a conformational change in the myofilaments d) storing energy that will be transferred to ADP to resynthesize ATP
d) storing energy that will be transferred to ADP to resynthesize ATP
fatigue
decreased capacity to do work -muscle experiences reduced efficiency -usually follows period of activity
atrophy
decreases size of muscle with disuse
synaptic fatigue
depletion of synaptic vesicles & neurotransmitters Ach (rare)
muscular dystrophy
destroyed skeletal muscle replaced with CT -Duchenne: sex-linked inheritance, primarily affects males -Facioscapulohumoral: less sever form, both males/females affected equally
action potential
electrical signals from motor neurons
AP is a ___________ event
electrochemical
"Cocking" of the myosin head—
energy from hydrolysis (breakdown) of ATP cocks the myosin head into the high-energy state
Cholinesterase
enzyme that decomposes acetylcholine, located at neuromuscular junction in the membranes of the motor end plate
Anything that ends in ase =
enzymes
Direct/fleshy attachments
epimysium of muscle fuses to periosteum of bone/pericardium of cartilage
physiological contracture
extreme muscle fatigue, incapable of contracting/relaxing, due to low ATP
fast oxidative fibers
fast contraction, aerobic (some anaerobic glycolysis), high myoglobin, red to pink, many mitochondria; best suited for combination activities like alternating sprinting and walking
elasticity
has both stretch and recoil capabilities
troponin
has polypeptides - TnI binds to actin - TnT binds to tropomyosin that helps position it on actin - TnC binds calcium ions
intense exercise (anaerobic)
increase muscle strength/mass; has greater effect on fast-twitch fibers
hypertrophy
increase size/muscle mass; working out, exercising
anabolic steroids
increase size/strength of muscles; side-effects include: sterility, cardiovascular problems, liver dysfunction, irritability
multiple-wave summation
increased tension caused by increase in stimulus frequency
hypertrophy
increases cell size not cell number
aerobic exercise
increases number of mitochondria, increases blood supply, increases endurance of both slow/fast twitch fibers -primarily increases the size of slow-twitch fibers
What does prolonged tetanus lead to?
inevitable muscle fatigue
fibrositis
inflammation of fibrous CT --> stiffness, pain, soreness
At rest tropomyosin and troponin _____ active sites on actin so linkages between actin and myosin ____ be formed
inhibit; CANNOT
psychological fatigue
involves CNS, "perceive" additional work is not possible so you consciously shutdown activity (muscle can still function) -additional burst of activity in athletes due to "crowd" ----> psychological fatigue can be overcome
hypertrophy
involves increase in muscle fiber size (more protein) rather than in number
ach receptor
ion channel that opens and allows for influx/entry of Na+ ions into the muscle cell
What kind of motor units do large, weight-bearing muscles, whose movements are less precise have?
large motor units
perimysium
layer of fibrous connective tissue that surrounds each fascicle
Ca2+ ions enter the axon terminal
leading to the release of Ach into synaptic cleft
aerobic endurance
length of time a muscle can continue to contract using aerobic pathways
muscles with delicate/precise movement have motor units with ______ number of muscle fibers, which results in more control.
less
What happens if sarcomeres are so compressed and cramped that Z discs abut the thick myofilaments and thin filaments touch and interfere with one another?
little or no further shortening can occur
H band
made of only thick filaments
epimysium
many fasicles grouped together
regular endurance exercise
may convert fast glycolytic fibers into fast oxidative fibers
contraction is a __________ event
mechanical
hypertrophy
muscle growth together with an increase in the size of muscle cells from strength or resistance training
skeletal and smooth
muscle tissue types that have tightly packed cells
myofilaments
myofibrils arises from orderly arrangement of even smaller structures within sarcomeres
relaxation
passive process, x-bridge release, no ATP required, but uses ATP pump
movement
primary function of muscle
agonist
prime mover; performs a specific movement
myasthenia gravis
produce Ab to Ach receptors therefore reduces number of functional receptors -causes flaccid paralysis -treated by neostigmine, blocks Achase activity allowing Ach to accumulate in the NM junction and bind to remaining receptors
myoblasts
produce muscle fibers
anaerobic respiration
produces 2 ATP per glucose
aerobic respiration
produces 32 ATP for every glucose
exercise
produces hypertrophy of existent muscle fibers
anaerobic respiration
produces lactic acid that has to be recycled by the liver
4 important functions of muscle tissues in the body
producing movement, maintaining posture and body position, stabilizing joints, and generating heat
as stimulus strength is increased from subthreshold to threshold to submaximal to maximal strengths, additional motor units are __________
recruited; recruitment
triads
regions where the SR terminal cisterns border a T tubule on each side
troponin
regulatory protein that binds to actin, tropomyosin, and calcium
tropomyosin
regulatory protein that covers myosin-binding sites to prevent actin from binding to myosin
tropomyosin
regulatory protein, "covers" 7 G-actin binding sites
aerobic respiration
requires mitochondria
excitability
responds to stimulus by nerves/hormones
myofilaments
responsible for muscle contraction Bundles of parallel protein microfilaments that make up a myofibril.
muscular fatigue
results form ATP depletion
external lamina
reticular fiber layer surrounding muscle fibers
recovery stroke
return of myosin head to its origonal position after x-bridge is broken
myosin
rod-shaped molecule with 2 heads (contain ATPase)
specific movements
roles of antagonist and agonists are really better applied to a _______________ than to the muscle itself because they play alternative roles
fasicle
root or bundle
synaptic vesicles
sac like structure in a synaptic know that contains Ach
stretch
smooth muscles can _______________ and still maintain contractility
The cross marking on skeletal muscles are called _____.
striations
maximal stimulus
strongest stimulus that increases contractile force; all motor units of a muscle are activated
Anything that ends in ose =
sugar
varicosities
swellings in nerve fibers, like axon terminals of motor neurons; release NT into wide synaptic cleft
isotonic muscle contraction
tension is constant during contraction and length of muscle changes. -contraction associated with joint movements
extensibility
the ability to extend or stretch
excitability or responsiveness
the ability to receive and respond to a stimulus
contractility
the ability to shorten forcibly when adequately stimulated (this ability sets muscle apart from all other tissue types)
contraction
the activation of myosin's cross bridges, which are the force-generating sites.
sarcolemma
the plasma membrane of a muscle fiber
sliding filament model of contraction
the thick and thin filaments past each other, shortening the sarcomere.
myosin
thick filaments
T-tubules
tubelike invaginations of sarcolema
T tubules
tubular infoldings of the sarcolemma which penetrate through the cell and emerge on the other side
1. number of motor units recruited, 2. size of muscle fibers, 3. frequency of stimulation, 4. degree of stretching
what are the factors that influence how much force a muscle produces
length-tension relationship
when muscle is slightly stretched and thin and thick filaments overlap optimally, permitting sliding along nearly entire length of thin filaments
isometric contraction
when muscle tension develops but load is not moved (increasing muscle tension is measured) muscle is not shortening nor lengthening
all-or-none-law
with an appropriate stimulus received, muscle fibers produce contractions of equal force
aerobic respiration
with oxygen present, glucose broken down to CO2+H2O with the production of large quantities of ATP -supports edurance activites
fascicles
within each skeletal muscle the muscle fibers are grouped into bundles called ___________________; these resemble bundles of sticks
anaerobic respiration
without oxygen present, lactic acid accumulates -can be used for short bursts of energy but not for endurance activity
synergist muscles
work in conjunction with agonist and antagonist to provide extra strength, prevent damaging movement, or immobilize larger muscles.
antagonist
work in direct opposition to agonist; usually limit agonist range of motion to avoid overextension
secretion
Muscle tissue has all of the following properties except ________.
Indirect attachments
Muscle's connective tissue extents as tendon (or aponeurosis) anchors to the bone/cartilage/other-muscle-fascia; more common; smaller, durable
work best
Muscles _______________ when not completely extended or contracted
Muscle tone is the small amount of tautness or tension in the muscle due to weak, involuntary contractions of its motor units. True / False
True
Steps for Relaxation
1. cholinesterase decomposes acetylcholine so sarcolemma is o longer stimulated 2. CA ions are actively transported back into the Saco ret 3. Linkages between actin and myosin are broken 4. Troponin and tropomysocin molecules inhibit the binding (active) sites of actin 5. Actin and myosin filaments slide apart...muscle fiber lengthens-relaxation
how is ATP regenerated after being hydrolyzed to ADP and Pi
1. direct phosphorylation of ADP by creatine phosphate 2. anaerobic respiration (glycolysis and lactic acid formation) which converts glucose to lactic acid 3. aerobic respiration
recruitment process
1. motor units with smallest muscle fibers activated first 2. motor units with larger and large muscle fibers get excited --> contractile strength increases 3. largest motor units with large muscle fibers controlled by largest neurons are activated when most powerful contraction is necessary
4 Factors that affect force of muscle contraction
1. number of muscle fibers stimulated 2. relative size of fibers 3. frequency of stimulation 4. degree of muscle stretch
Smooth muscles relax when intercellular Ca2+ (calcium ion) levels drop but may not cease contractions. True / False
True
If stimulus strength is held constant and muscle is stimulated at increasingly faster rate
1. relaxation time between twitches get shorter and shorter 2. concentration of calcium in cytosol rises higher and higher 3. degree of wave summation becomes greater and greater
Actin (from notes)
1/4 total protein in skeletal muscle; globular structure with myosin binding sites attached to surface
ATP reserves in muscle
1st energy reserve source - only 4 - 6 seconds worth of energy
Citric Acid Cycle
2 ATP; waste: carbon dioxide
Each actin myofilament contains _______________
2 fiberous actin (F-actin) + tropomyosin + troponin
smooth muscle facts:
-spindle-shaped fibers, mononucleate, involuntary -NOT organized into sacromeres, not striated -slower contraction speed but sustain tension longer -decreased number of actin/myosin filaments present -contain intermediate filaments and dense bodies -actin attaches to intermediate filaments (~equivalent to Z lines) -Ca2+ binds to calmodulin and activates myosin kinase -myosin kinase adds Pi from ATP to myosin -myosin phosphatase removes Pi from myosin (release of x-bridge)
neromuscular junction
-synaptic vesicles contain NT (neurotransmitter) acetyelcholine (Ach) -acton potentials at prsynaptic terminal causes Ca2+ channel to open which causes vesicles to migrate -NT released into synapse -Ach binds to protein receptor on postsynaptic side -ligand-sensitve Na+ channels open -AP is propagated along sarcolema
_____ molecule of ATP is required for x-bridge formation/movement/release cycle
1
motor units
1 motor neuron and all the muscle fibers it innervates
3 steps involved in generating action potential
1. Generation of end plate potential 2. Depolarization 3. Repolarization
Two steps of cellular respiration
1. Glycolysis (2 ATP) 2. Aerobic respiration (34 ATP) - Citric Acid Cycle (Krebs's) (2 ATP) - Electron Transport Chain (32 ATP)
FIRST Channel Involved in Initiating Muscle Contraction
1. Nerve impulse reaches axon terminal and opens voltage-gated Ca channels in axonal membrane --> influx of Ca triggers release of ACh into synaptic cleft
Slow twitch/red muscle
"dark meat" lots of myoglobin and lots of mitochondria so does lots of cellular respiration to get ATP; does NOT fatigue easily; ex: back muscles (for posture) and thigh muscles
sarcoplasmic reticulum
"endoplasmic reticulum" of a muscle fiber; membranous channels that run parallel to and surround each myofibril
Transverse tubules
"t-tubules"; membranous channels that go from the sarcolemma all the way through the muscle fiber; open to the outside of the muscle fiber; invaginations of the sarcolemma; contain extracellular fluid
fast-twitch (low-oxidative) fibers
"white meat" -respond quickly, less-developed blood supply, low number of mitochondria -fatigue quickly -high deposits of glycogen -adapted for anaerobic respiration
concentric contraction
(type of isotonic contraction) muscle shortens and does work
Rich blood supply because (2)
1. Uses huge mounts of energy 2. Removes numerous amounts of metabolic wastes
What is the role of calcium ions in muslce contraction? a) form hydoxyapatite cyrstals b) reestablish glycogen stores c) bind to regulatory sites on troponin to remove contraction inhibition d) increase levels of myoglobin
) bind to regulatory sites on troponin to remove contraction inhibition
Contractility
-ability to shorten forcibly when adequately stimulated
What happens during contraction:
-actin and myosin slide past eachother -x-bridges form between actin/myosin----> x-bridges form, move, release, reform -action results in inward movement of actin filaments towards H zone -Z lines are brought closer together
acetylcholinesterase
-breaks down unused Ach within synaptic cleft -prevents constant stimulation of the junction; 1 presynaptic AP--> 1 postsynaptic AP
smooth muscle RMP
-doesn't respond in an all-or-none fashion -slow wave of depolarization due to Na+ and Ca2+ movement -epinephrine stimulates muscle contraction by activating G-proteins -oxytocin stimulates muscle of uterus -smooth muscle contracts when stretched and exhibits constant tension -innervated by ANS (involuntary)
SECOND Channel Involved in Initiating Muscle Contraction
2. ACh binds to receptors on sarcolemma and opens ligand-gated Na+-K+ channels --> influx of Na+ causes voltage change (depolarization)
__-__% of energy available from cellular respiration and ___% is lost as heat
20-25%; 75%
Each F-actin polymer is about equal to _________ globular actin (G-actin) monomers
200
direct phosphorylation of ADP by creatine phosphate
2nd energy reserve source - required NO oxygen, 1 to 1 production rate; about 20 - 30 seconds (text says 15)
THIRD channel involved in initiating muscle contraction
3. Depolarization opens voltage-gated sodium channels in neighboring region of sarcolemma allowing more Na+ to enter --> more depolarization in sarcolemma --> generates and propagates an action potential
Electron Transport Chain
32 ATP; waste: water
Glucose molecule gives enough energy for __ ATP
36
Women's skeletal muscles make up approx. __% of body mass
36%
myoblasts
A cell that builds muscles
True
A contraction in which the muscle does not shorten but its tension increases is called isometric.
Aerobic respiration
A metabolic pathway that provides for a large amount of ATP per glucose because oxygen is used. Products are water and carbon dioxide and ATP.
False
A motor neuron and all the muscle cells that it stimulates are referred to as a motor end plate.
Motor unit
A motor neuron and the muscle fiber it controls; page 286-7
isotonic contraction
A muscle contraction that pulls on the bones and produces movement of body parts. (picking up a box)
Acetylcholine
A neurotransmitter released at motor end plates by the axon terminals.
Slow (oxidative), fatigue-resistant fibers
A relatively high percentage are found in successful marathon runners.
True
A resting potential is caused by a difference in the concentration of certain ions inside and outside the cell.
the area between two Z discs
A sarcomere is ________.
Z discs
A sarcomere is the distance between two ________.
local depolarization (end plate Potential)
ACh binding opens chemically (ligand) gated ion channels Simultaneous diffusion of Na+ (inward) and K+ (outward) More Na+ diffuses, so the interior of the sarcolemma becomes less negative Local depolarization - end plate potential
Energy for contractions comes from what?
ATP
______ is energy source for muscle contraction
ATP
Aerobic respiration
Aerobic; sequence of chemical reactions in which the bonds of fuel molecules are broken and the energy releases is used to make ATP (34 ATP); includes Citric Acid Cycle and Electron Transport Chain
level in the cytoplasm drops
After nervous stimulation of the muscle cell has ceased, the calcium ________.
True
Although there are no sarcomeres, smooth muscle still possesses thick and thin filaments.
glycolysis
An anaerobic metabolic pathway that results in the production of two net ATPs per glucose plus two pyruvic acid molecules is ________.
no contraction at all by nervous mechanisms, but contraction if stimulated by an external electrode
An individual has just ingested a chemical that binds irreversibly to the ACh receptors in the sarcolemma. By itself it does not alter membrane potential, yet prevents normal neurotransmitter binding. Ignoring the effects on any other system, the consequence to skeletal muscle would be ________.
myoglobin
An oxygen-storing, red pigmented protein in muscle cells.
Glycolysis
Anaerobic; first phase of cellular respiration that breaks glucose down into tow pyruvic acid molecules and tow ATP; occurs in cytoplasm (2 ATP)
Perimysium
Around each fascicles, is a layer of fibrous connective tissue
Three discrete types of muscle fibers are identified on the basis of their size, speed, and endurance. Which of the following athletic endeavors best represents the use of red fibers? A) a sprint by an Olympic runner B) a long, relaxing swim C) playing baseball or basketball D) mountain climbing
B) a long, relaxing swim
limping
Claudication might more simply be called ________.
Red muscles tend to have a slow (oxidative) rate and fatigue resistance, whereas white muscle cells have a fast (oxidative) rate and fatigue easily.
Compare red and white muscles relative to their speed of action and endurance.
biochemistry
Constant temperature is necessary because our _______________________ has adapted to that temperature and will only function correctly there.
Tetanus
Continued sustained smooth contraction due to rapid stimulation.
True
Contractures are a result of a total lack of ATP.
Equation for creating phosphate
Creatine phosphate + ADP => creatine + ATP
storing energy that will be transferred to ADP to resynthesize ATP
Creatine phosphate functions in the muscle cell by ________.
sarcoplasm
Cytoplasm of muscle cell; has large amounts of glycosomes
Actin molecules arranged in a ____ ___ to form an actin filament
Double helix
False
During isometric contraction, the energy used appears as movement
False
During isotonic contraction, the heavier the load, the faster the velocity of contraction
actin filaments
During muscle contraction, myosin cross bridges attach to which active sites?
Generation and propagation of an action potential:
End plate potential spreads to adjacent membrane areas Voltage-gated Na+ channels open Na+ influx decreases the membrane voltage toward a critical threshold If threshold is reached, an action potential is generated
4 Characteristics of muscle tissue
Excitability/Responsiveness/Irritability Contractility Extensibility Elasticity
During isometric contraction, the energy used appears as movement. True / False
False Muscles act to hold joints in stationary positions while movement occurs at other joints.
A motor neuron and all the muscle cells that it stimulates are referred to as a motor end plate. True / False
False; Motor unit not motor end plate.
Once a motor neuron has fired, all the muscle fibers in a muscle contract T/F
False; all the muscle fibers in innervates contract
Fast twitch/white muscles
Few mitochondria and less myoglobin; gets most of its ATP through creating phosphate and Glycolysis and; DOES fatigue easily; found in muscles used in rapid movement
The ____ muscle fibers in a motor unit, the ___ movements of the muscle (example:__)
Fewer; finer; eye muscles
Cellular respiration formula
Glucose + oxygen => carbon dioxide + water + ATP C6H12O6 + 6O2 => 6CO2 + 6H2O + Energy/ATP
conserves energy
Graded response of muscle fibers; not activating more muscle fibers than we need ___________________
sarcopenia
Gradual loss of muscle mass
Fast (oxidative or glycolytic), fatigable fibers
Have very fast-acting myosin ATPases and depend upon anaerobic metabolism during contraction.
Creatine phosphate
High energy molecule stored in muscles; tapped to regulate ATP while metabolic pathways are adjusting to higher demands for ATP; short-lived
1 ATP
How much energy is necessary for each myosin head to bind with actin?
changes in length and moves the "load"
In an isotonic contraction, the muscle ________.
one nerve, one artery, and one or more veins
In general, _________________________________________ serve each muscle. These structures all enter or exit near the central part of the muscle and branch profusely through its connective tissue sheaths.
remove the blocking action of tropomyosin
In skeletal muscle contraction, calcium apparently acts to ________.
Cardiac Muscle
In the heart Involuntary Striated Steady and constant rate of contraction
proximal
In the muscles of the limbs, the origin typically lies ___________________________ to the insertion.
I bands
Lighter bands between each A band; contains actin
H zones
Lighter region in middle of A band; myosin
How can old people get muscle strength back/maintain it?
Lightly working out
Intermittent claudication
Limping condition that restricts blood delivery to the legs and has excruciating pains in the leg muscles while walking
fascicle
Muscle fibers grouped together; wrapped in perimysium
What is a myofilament?
Long strands of muscle
myofibrils
Microscopic protein filaments that make up muscle cells.
When is the natural peak of motor control?
Mid adolescence
Another name for muscle cells
Muscle fibers
ATP, mechanical energy
Muscles transform chemical energy of _____________ into _______________________ for movement.
run the length
Myofibrils ______________________ of the cells (their orientation).
stores oxygen in muscle cells
Myoglobin ________.
Repolarization:
Na+ channels close and voltage-gated K+ channels open K+ efflux rapidly restores the resting polarity Fiber cannot be stimulated and is in a refractory period until repolarization is complete Ionic conditions of the resting state are restored by the Na+-K+ pump
Each muscle is served by one ___, ____, and more than one ____
Nerve, artery...vein
Calcium ions
Normally stored in the terminal cisternae of the sarcoplasmic reticulum
Lactic Acid formation
Occurs when not enough oxygen is available to send pyruvic acid into aerobic respiration; due to extreme exercise; ex: muscles working hard due to running so can't get enough oxygen into body (lung capacity) so blood can't get to lungs to pick up more oxygen so causes oxygen deficit/debt
multiunit smooth muscle
Of the following muscle types, which has only one nucleus, no sarcomeres, and rare gap junctions?
False
Once a motor neuron has fired, all the muscle fibers in a muscle contract
a sarcomere
One functional unit of a skeletal muscle is ________.
True
One of the important functions of skeletal muscle contraction is production of heat.
___ motor nerve fiber is connected to ____ muscle fibers so ___ muscle fibers connected to the same nerve fiber contract ______
One; many; all; simultaneously
skeletal
Only ________ muscle cells are always multinucleated.
cardiac
Only ________ muscle cells commonly branch.
Skeletal muscle
Organs that attach to/cover bony skeleton Rapid contraction, but tires easily (bunny) Striations voluntary
False
Oxygen debt refers to the oxygen required to make creatine phosphate.
2nd Step Cross Bridge Cycle
POWER STROKE - ADP and Pi are released - myosin head pivots & bends --> low-energy state - pulls actin filament toward M line
True
Peristalsis is characteristic of smooth muscle
sarcolemma
Plasma membrane around muscle fiber
Cellular respiration
Process that releases energy by breaking down glucose and other food molecules in the presence of oxygen; eating and breathing to get energy
Muscle functions
Producing body movement (locomotion, manipulation) Maintaining postures and body positions Stabilizing joints Generating heat (40% of body mass; most responsible for heat)
False
Recruitment is an option in a single-unit smooth muscle cell
myoglobin
Red pigment that stores oxygen, transports it
Conductivity
Response; generation of electrical impulse that passes along plasma membrane of muscle cell and causes cell to contract
A contraction in which the muscle does not shorten but its tension increases is called isometric. True / False
True Isometric - tension may build to the muscle's peak, tension producing capacity, but the muscle neither shortens or lengthens. iso = same metric = measure
triad
Sarcoplasmic reticulum Transverse tubules Terminal cisternae
Calcium ions
Serves as the actual "trigger" for muscle contraction by removing the inhibition of the troponin molecules.
Duchesne muscular dystrophy
Sex-linked recessive disease; females carry and transmit; almost always males have it; 2-7 years old; healthy people become clumsy and fall as skeletal muscles fail; usually die in 20s
Neuromuscular junction
Site where motor nerve fibers and muscle fires meet; also called myoneural junction
The fibers of ____ and ____ are striated.
Skeletal and cardiac
muscle fibers
Skeletal and smooth muscle cells are elongated, and for this reason, they are called ________________________.
40%
Skeletal muscle accounts for at least ______________________ of body mass.
*Other functions of muscle*
Skeletal muscles protect inner organs Smooth muscle forms valves for passage (sphincters) Dilate pupils of eyes
Motor end plate
Specialized part of sarcolemma/muscle at the neuromuscular junction; sarcolemma is extensible folded; area has many nuclei and mitochondria
Development in a kid begins in ___ and radiates ___
Starts in head, radiates outward
contractures
State of continuous contractions; ex: writer's cramp
Muscle fatigue
State of physiological inability to contract even though the muscle still may be receiving stimuli; results from a relative deficit of ATP; not its total absence
steroids
Synthetic male hormones
exhibit spontaneous action potentials
The cells of single-unit visceral muscle ________.
myofibrils
The contractile units of skeletal muscles are ________.
Eccentric contractions are more forceful than concentric contractions. True / False
True Eccentric contractions - muscle generates force as it lengthens in your calf muscles as you walk up a hill. Concentric contractions - muscle shortens and does work, such as picking up a book or kicking a ball.
insertion
The end of the muscle that typically moves when a muscle contracts is called the ________.
True
The force of muscle contraction is controlled by multiple motor unit summation or recruitment.
enhance cellular communication during muscle contraction
The functional role of the T tubules is to ________.
enhance the availability of calcium and the efficiency of enzyme systems
The main effect of the warm-up period of athletes, as the muscle contractions increase in strength, is to ________.
regulate intracellular calcium concentration
The major function of the sarcoplasmic reticulum in muscle contraction is to ________.
the site of calcium regulation differs
The mechanism of contraction in smooth muscle is different from skeletal muscle in that ________.
False
The more slowly a skeletal muscle is stimulated, the greater its exerted force becomes
the ability to transform chemical energy into mechanical energy
The most distinguishing characteristic of muscle tissue is ________.
voltage (electrical)-gated Na+ and K+ channels
The muscle AP propagates over the surface of the muscle cell membrane (sarcolemma) via
sarcolemma
The muscle cell membrane is called the ________.
A band
The myosin filaments are located in the ________.
myoglobin
The oxygen-binding protein found in muscle cells is ________.
Treppe
The phenomenon in which the contraction strength of a muscle increases, due to increased Ca2+ availability and enzyme efficiency during the warm-up.
bind to regulatory sites on troponin, changing the configuration
The role of calcium ions in muscle contraction is to ________.
calmodulin
The site of calcium regulation in the smooth muscle cell is ________.
Wave summation
The situation in which contractions become stronger due to stimulation before complete relaxation occurs
actin and myosin sliding past each other and partially overlap
The sliding filament model of contraction involves ________.
Maximal stimulus
The stimulus above which no stronger contraction can be elicited, because all motor units are firing in the muscle
the arrangement of myofilaments
The striations of a skeletal muscle cell are produced, for the most part, by ________.
increasing the stimulation up to the maximal stimulus
The strongest muscle contractions are normally achieved by ________.
Myosin
The thicker filaments are the ________ filaments.
contraction
The time in which cross bridges are active is called the period of ________.
An increase in the calcium ion level in the sarcoplasm starts the sliding of the thin filaments. When the level of calcium ions declines, sliding stops. True / False
True
Contractures are a result of a total "lack" of ATP. True / False
True
Muscle fibers don't have to completely relax before being stimulated by a second action potential. True/False?
True
treppe
The warm-up period required of athletes in order to bring their muscles to peak performance is called ________.
Smooth and cardiac do not do what?
They don't fuse
Myosin (Newville)
Thick filaments; solid with projections coming off; rod-like tail with two heads; 6 strands
a long, relaxing swim
Three discrete types of muscle fibers are identified on the basis of their size, speed, and endurance. Which of the following athletic endeavors best represents the use of red fibers?
both the sarcoplasmic reticulum and transverse tumbles function to___________________________
To activate the muscle contraction mechanism
tendons
Tough collagen fibers that withstand touch bony protections; small size-conserve space
Creatine phosphate
Used to convert ADP to ATP by transfer of a high-energy phosphate group. A reserve high-energy compound.
Heart is pumping blood by what week?
Week 3
Skeletal muscle fibers are contracting by what week?
Week 7
Oxygen Deficit/Debt
When have less than amount of oxygen a body must take in for restorative process; causes arctic acid buildup; occurs when you don have enough oxygen in you body to send all the pyruvic acid into the aerobic part of cell respiration
Muscle's origin
When muscle contracts: immovable
Muscle's insertion
When muscle contracts: moveable
False
Whereas skeletal muscle cells are electrically coupled, smooth muscle cells appear to be chemically coupled by gap junctions.
thick filaments
Which of the following are composed of myosin?
a change of temperature
Which of the following does not act as a stimulus to initiate a muscle contraction?
Muscle tension remains relatively constant during isotonic contraction.
Which of the following is most accurate?
increase in the number of muscle cells
Which of the following is not a usual result of resistance exercise?
Certain smooth muscle cells can actually divide to increase their numbers.
Which of the following is true about smooth muscle contraction?
There is no biological basis for the difference in strength between women and men.
Which of the following statements is not true concerning developmental aspects of muscle?
Striated muscle cells are long and cylindrical with many nuclei.
Which of the following statements is true?
motor units with larger, less excitable neurons
Which of the following would be recruited later in muscle stimulation when contractile strength increases?
treppe
a "staircase"-like graded response -a "warming-up" phenomenon in rested muscle -first few action potentials result in contraction of increasing strength/tension -all further contractions show same tension
synaptic cleft
a gap into which neurotransmitters are released from the axon terminal
The giant protein titin maintains the orgainzation of the ___ assisting in muscle stretching. a) A band b) I band c) Z disc d) M line
a) A band
threshold stimulus
action potential produced, muscle contraction results
total tension
active+passive tension
Nerve endings controls ____
activity
maximal stimulus
all motor units of a muscle are activated
Why is the size principle important?
allows increases in force during weak contractions to occur in small steps
epimysium
an "overcoat" of dense irregular connective tissue that surrounds the whole muscle
troponin
calcium binds with ________________ which pulls the tropomyosin out of the way of the actin binding sites and allow myosin to bind with actin
extensibility
can be stretched beyond their resting length to some degree
sarcolemma
cellular membrane of muscle fiber (plasma membrane)
involuntary
chemical control of smooth muscle is identical to skeletal muscle, but they are completely __________________
fibromyalgia
chronic muscle pain syndrome
additive
sequential stimulations are ______________ if they are close together
head production
shivering -muscle contractions generate heat, increase body temperature
cross bridges
shortening of fiber occurs when tension generated by _____ on the thin filaments exceeds forces opposing shortening
contractility
shortens when stimulated
Cells of ____ muscle tissue have many nuclei.
skeletal
What kind of motor units do muscles that exert fine control have?
small motor units
threshold stimulus
stimulus when first observable contraction occurs
skeletal & cardiac
striated muscle types
myfibrils
threadlike structures composed of 2 myofilaments
lag phase
time between stimulus at motor neuron & beginning of contraction
contraction phase
time of contraction (muscle shortening)
relaxation phase
time of relaxation (recovery)
directly proportional
trength of muscle contraction is _______________ to the number of motor units activated (allows for a smooth and continuous variation of tension)
Actin filament has two other proteins associated with it
tropomyosin; troponin
