Muscle Physiology_4 Flashcards

Terms Definitions
seratus magnus
I-band has
only actin
Intracellular fluid inbetween myofibrils.
property of muscle tissue
Outer layer surrounding muscle fascicles.
nonstriated, smooth muscles (ex: bladder)
Prime Mover
Muscle responsible for most movement
The force of muscle contraction increases if you stimulate again before the end of relaxation is called_____________.
Ryanodine Receptor
Voltage sensitive receptor that monitors the DHPR receptor. Causes sarcoplasmic reticulum to dump calcium upon excitation.
Smaller structures within sarcomeres. Thin = Actin, Thick = Myosin
smooth muscle is regulated by __________ neurons.
When muscle is oxygen-depleted, the energy for muscle contraction is derived from an anaerobic process called
The increasing number of twitches occurring with continued muscle
1. contractile proteins2. regulatory proteins (turn contraction on and off)3. structural proteins
contractile proteins
Know skeletal muscle microscopic structures. Be able to recognize structures and know major functions of each:
has active sites
Remodeling of muscle to match function
-Muscle hypertrophy
-Muscle atrophy
-Adjustment of muscle length
-Hyperplasia of muscle fibers
the scarring is associated with severe trauma to skeletal muscle and with heart attacks in cardiac muscle
T tubule
Continuations of the sarcolemma that encircle each sarcomere and ensure that every myofibril in the muscle fiber contracts at the same time.
Muscle atrophy=
muscles not used and become 'flabby'
Much of the lactic acid produced during strenuous muscle activity is carried from the muscle cells for metabolism by the
Muscle contracts after its threshold has been reached, and the response is called the
all-or-nothing response
lots of mitochondria (larger than skeletal, thus req more O2)longer contractions than skeletal
cardiac muscle
48. What happens to the tension generated during multiple motor unit summation?
tension increases
What does tropinin do
controls movement of tropomyosin.  Tropomyosin determines whether the thin filaments are covered or not.  Covered in relaxed muscle
----- fibers are common in sprinters where large amounts of myoglobin, many mitochondria, and many blood capillaries are advantages for high velocity activity of short duration.
Fast twitch
internal tension
The force generated by cross bridges (myofibrils).
Satellite cells
embryonic cells that did not become muscle cells but can become muscle cells to repair damage
contraction depends on what 2 proteins?
actin and myosin
All-or-nothing response
Fiber contracts only after an impulse exceeds a certain threshold and spreads through the cell.
essential for maintaining head posture; important in maintaining BP*-tone of smooth muscles in walls of blood vessels
how muscle contraction begins
6. What does acetylcholine bind to on the motor end plate?
acetylcholine receptors
What is an incomplete/unfused tetanus?
sustained muscle contraction that permits partial relaxation between stimuli
What is happening during the Latent Phase?
The Excitation-Contraction Coupling 
second-class levers
FULCRUM - LOAD - EFFORT. Example: standing on tip-toes & wheel-barrow.
When a muscle is at rest, myosin heads are prevented from binding to actin by a protein called
Single unit smooth muscle
visceral muscle whose fibers contract together as a rhythmic unit, and are coupled by one another by gap junctions
-no sarcomeres-sliding of thick & thin generates tension-transferred to intermediate filaments & dense bodies attached to sarcolemma-contracts: twists into a helix as it shortens, relaxes by untwisting-intermediate filaments and dense bodies; generate ten
multiunit smooth muscle
78. What is an example of an autoimmune destruction of pre-synaptic calcium channels?
Lambert-Eaton myasthenia syndrome
101. What two things are lacking in smooth muscle?
troponin and t-tubules
Where must the calcium be pumped to in order for skeletal muscle to relax?
sarcoplasmic reticulum
what force production is changed during #1
Number of motor units activated
Increase motor units activated
Increase force
Which bands get smaller and which ones don't in the Sliding Filament Theory?
I-Band= Smaller
H-Zone= Smaller
Sarcomere itself = Smaller
A-Band = stays the same
maximum tetanic tension
when the muscle is generating all the force it can
skeletal muscle starts to be replaced by fat beginning @ 30-body goes into conservation mode-slowing of reflexes & dec in maximal strength-change in fiber type to slow oxidative fibers may be due to lack of use or may be result of aging
aging & muscle tissue
54. If I am pushing against a wall, what type of muscle contraction is occuring?
an isometric contraction
What does the Sarcoplasmic Reticulum (SR) do?
System of tubule sacs
Stores Calcium when relaxed
Release of Calcium triggers contraction
What is a Muscle Twitch?
A muscle contraction, followed by a muscle relaxation.
Compare the characteristics of regulatory systems for skeletal muscle (actin-linked) and smooth muscle (myosin-linked).
In smooth muscle, the actin filaments lack troponin and tropomyosin, which keeps skeletal muscle in a state of inhibited readiness. Instead, myosin must be phosphorylated by myosin light chain kinase which is activated by the binding of calcium to calmodulin.
visceral (single-unit) smooth muscle
in the walls of hollow viscera and small BV
20. What happens to the acetylcholine left in the synapse of the neuromuscular junction?
it is broken down by acetylcholinesterase into acetic acid + choline
What are the primary functions of skeletal muscle?
- moves the skeleton- produces heat
What is a Polysynaptic Reflex?
A reflex that involves 2 or more neurons.

SN synapse w/ Interneuron in S.C
Interneuron synapses w/ MN in S.C. (or brain stem)
MN innervates muscle
Describe the different contraction and relaxation phases of a single isotonic twitch.
1) Rise of isometric force, until sufficient force has developed to lift the weight.
2) Isotonic shortening and 3) isotonic relaxation as the force is constant.
4) Isometric relaxation because the muscle is no longer lifting the weight.
106. In smooth muscle, are contraction slow or fast, and why?
slow because the enzymes involved in cross-bridging are slow
For the successful completion of a muscle contraction, the sarcoplasmic reticulum
ATP,l which breaks down and releases energy
12. What are the active sites on actin for?
where myocin heads bind to actin
What is the role of myosin light chain phosphatase in smooth muscle?
It dephosphorylates the myosin, making it inactive. As a result, the cross-bridge cycle stops and the muscle relaxes.
What is the primary function of cardiac muscle?
- pumps blood (Do you really need a flashcard for this question, dumbass?)
for a motor unit to be recruited into activity the motor nerve impulse must meet or exceed the threshold
if the threshold is not met no fibers in that unit act
rectus femoris
Overlap Zone
myosin/actin overlap
threshold stimulus
First observable contraction.
myasthenia gravis
chronic; muscles easily fatigued
Muscle SHORTENS and does work.
Skeletal muscle - present
Smooth muscle - absent
Cardiac muscle - present
17. During a contraction, do sarcomeres shorten or lengthen?
protein found in muscle fibers
muscle rich in myoglobin is called red muscle
slow twitch muscle fibers
combines with oxygen to form oxymyoglobin
stores oxygen
found abundently in cardic muscle
Ionotrophic Agents
Enhance cardiac muscle contractility to increase cardiac output by increasing cytosolic calcium.
maximal stimulus
Strongest stimulus representing point in which all of the muscle's motor units are recruited.
myosin kinase
This binding triggers a conformational change that enables the calcium-calmodulin complex to bind to and activates an enzyme called ________ ________.
epimysium and fascia
enclose the entire muscle
loss of ability to move body part
Define or Explain:
Stimuli between threshold and maximal
Smooth muscle contraction is a result of an ______________ in intracellular ______.
Muscle Fiber
Surrounded by the endomysium. Contain thousands of myofibrils along with nuclei and mitochondria.
diffuse junctions
Wide synaptic cleft encompassing many smooth muscle cells.
The difference btwn fast and slow twitch fibers is based not on their size or shape, but instead on the type of _______ present in their thick filaments.
The thick filaments in the central portion of the sarcomere are composed of the protein
creatine phosphate
source of ATP production in muscle
67. What process is a direct phosphorylation of ATP to yield 10 to 15 seconds of energy?
phosphogen system
100. In smooth muscle, what anchors actin to the sarcoplasm?
dense bodies
What are the components of a connective tissue?
Skeletal Muscle
Contraction Phase
1. cross bridges between actin and myosine molecules form, move, realese over and over causeing sarocmere to shorten
2. energy from head of myosine molecule
3. ATP binds to myosine head and then is broken down by ADP
4. cross bridge is released and moces bak to resting position ready to form another cross bridge
5. some energy is released as heat
neuromuscular junction
Area where axon endings meet with individual muscle fibers.
Smooth Muscle Tissue
*Most all organs*Spindle shape with single nucleus*Not striated*Myosin scatted throughout cell*Actin attached to dense bodies*Contraction causes muscle to 'twist'
Smooth muscle may be found in the
digestive tract
White muscle is so named because it has little or no
I band
Broad stripe on sarcomere bisected by Z line
small fiber size, small motor unit, slow twitch speed, highest capillary density, low glycogen content, slow fatigability rate
Type IIa
40. During tetanus, what happens to the contraction phase?
it is constant
What are the 3 layers of connective tissue from outermost to innermost?
All of these extend beyond the muscle belly to form the tendon
Duchene Muscular Atrophy
This condition is inherited as a sex-linked recessive gene. eventually, the muscles shorten casue immobility of the joints and scoliosis
third-class levers
LOAD - EFFORT - FULCRUM. Example: biceps curl & tweezers.
Adenosine Triphosphate (ATP)
broken down by enzymes into ADP
bginds to enzyme on myosin head
ATP molecule is cleaved, ADP and phosphate remain bound to the head.
What is a muscle fiber?
A single, cylindrical, multinucleate muscle cell about .1 mm in diameter and a few mm long.
89. What type of muscle fiber is a fast oxidative-glycolytic fiber?
intermediate fibers
What happens during relaxation
AChE breaks down ACh in synaptic cleft
Muscle AP stops
Ca2+ release channels close and Ca2+ is pumped back into SR
Troponin and tropomyosin move to cover actin's binding site
Sarcomeres return to resting length
What are the 2 kinds of muscle contraction?
Isotonic and Isometric
The thin filaments of a sarcomere in a skeletal muscle fiber are anchored to the
Z line
Which strand contracted?
The one that was treated with KCl MgCl2 and ATP
81. What type of muscle fibers are slow oxidative fibers?
red, slow twitch fibers
What happens in the relaxation state of a muscle?
Calcium releases and channels close
Troponin holds tropomyosin in position to block myosin-binding sites on actin
What are the main sources of energy for muscle contraction?
aeoriciv resperisation, anaeobic resperation, cellular resperation, creatine phosphate, glycogen
What does "Vmax" represent?
It is the maximum velocity that a muscle can contract when maximally stimulated with a theoretical condition of no afterload.
great ability to make energy
fatigue resistant, bc have lots of mitochondria, blood & oxygen (aerobic fuels)
3. What muscle fiber characteristics would you see at the motor end plate?
hightly folded sarcolemma and lots of mitochondria
What gives us striations and where do they attach?
Thick and Thin filaments
Z disc
List some major characteristics of Smooth Muscle
Aids in Homeostasis (regulates BP and temp)
Has slow contractions
Requires little E (compared to skeletal)uses less ATP but has the same force
maintain force, yet resistant to fatigue
low O2 consumption

Contractions are signaled by Hormones and NT
Can be Excited or Inhibited
Have variable electric properties
List the sequence of events starting with an increase in cytoplasmic Ca2+ concentration and leading to the activation of the crossbridge cycle in smooth muscle.
Calcium enters the sarcoplasm and binds calmodulin, activating the myosin light-chain kinase (MLCK). MLCK phosphorylates the regulatory myosin light chain, changing it to an active form. The phosphorylated myosin can participate in the mechanical crossbridge cycle.
**It is important to remember that variations in the internal [Ca2+] can cause corresponding gradations in the contractile force in smooth muscle.
Explain isotonic and isometric muscle contractions. Which is preferred for exercises to increase muscle strength?
Tension changes as one pulls harder in an effort to move an object that is too big to move.
Isotonic is better for physical activity because it gives full range of muscles used and also increases coordination of muscles
What is a motor unit?
A single motor axon and all the fibers it innervates.
41. During tetanus, how much tension is generated?
the greatest amount of tension (at its peak)
split ATP at very fast rate; used for walking & sprinting
Fast twitch speed, high capillary density, aerobic & anaerobic, intermediate glycogen content, fatigability rate, fiber size, and motor unit size
Which conditions can lead to fatigue of a muscle?
- ATP production is less than ATP use- accumulation of lactic acid- ionic imbalances
striated, involuntary
bathes the myofibrils
Muscle fiber cell membrane
Knoblike swellings of certain autonomic axons containing mitochondria and synaptic vesicles. Releases neurotransmitters into diffuse junctions.
neurotransmitter released when nerve impulses reach the muscle fiber at the neuromuscular junction
these are painful spastic muscle contractions that usually result form an irritation within a muscle
Beta-adrenergic Agonists
Increase intracellular cAMP to phosphorlate and activate calcium channels. Ionotrophic Agent.
The layer of dense irregular connective tissue surrounding the whole muscle.
red muscle
Because myoglobin imparts a reddish-brown color oxidative fibers, these fibers are often referred to as ____ _______.
portion of the muscle with fibers
actin only
almost disappears during muscle contraction
is the protein of the myofibril between 2 successive Z lines
After the action potential travels along the sarcolemma (plasma membrane of muscle cells), where else will the AP travel?
transerve tubules
What NT is released into the Neuromuscular Cleft?
Make up muscle fibers. Contains ~3000 thin and ~1500 thick filaments.
Immoveable or less movable bone in which the muscle is attached.
increase in # of active motor units
Heart muscle is also known as
cardiac muscle
Intercalated discs
Binds ends of cardiac muscle together
Many gap junctions- electrical current flows easily.
during relaxation-build more creatine p stores
anaerobic cellular respiration
62. What is the immediate source of energy for a muscle contraction (provides only few seconds of energy)
51. What type of muscle contraction will not change muscle length?
isometric contraction
List the components of a muscle from the smallest to the largest part
Muscle fiber
Blood Capillary
Motor Neuron
Duchene Muscular Dystrophy
is almost exclusively affects males, and by early adolescence, the individual is weelchair bound
relaxation phase
typically the longest of the tree phases, is the time btwn peak tension and the end of the contraction, when tension returns to zero.
The contraction of a muscle fiber is known as a
smooth muscle tone
•Prolonged presence of calcium in the cytosol leads tosmooth muscle tone, a state of continued partialcontraction• Stress-Relaxation Response: smooth muscle fibers canstretch considerably without developing tension• Useful for maintaining blood pressure or a steadypressure on the contents of GI tract
Z lines
actin filaments are attached to it at the ewnd of I band
71. What is produced as a waste product of glycolysis?
lactic acid
Energy for muscle contraction
-  cellular ATP (1-2 sec.)
-  phosphocreatine (5-8 sec.)

-  intramuscular glycogen (1 min.)
-  oxidative metabolism (hours)
Facioscapullohumeral Muscular Dystrophy
it is an inherited and progressice condition. the muscles of the face and shoulder girdle are primarily involved
Step 5
Na+ causes Ca(2+) to be released from transverse tubules (TT) and sarcoplasmic reticulum
Thin filaments
one of 2 types of myofilaments which compose sarcomere
Run parallel to one another
made of protein actin
What is tetanus?
A sustained contraction due to rapid, repeated motor signals.
What is a mucle body?
Things like Biceps and triceps
90. What type of muscle fiber is type IIa or type III fibers?
intermediate fibers
What 3 things are needed to keep the contraction cycle repeating?
Nerve signal
What is the Maximum Rate of Oxygen Consumption?
Our aerobic capasity
Muscle Fiber Type II
( Fast-Twitch Fibers )
few mitochondria
rich in glycongen
depend on creatine phosphate and glyocolysis for atp production
fatique easily with prodcuion of lactic acid
low in myoglobin hence whitish in color (white meat in turkey)
activated by large diameter, thus, fast-conduction motor neurons
dominant in muscles used for rapid movement
Striated muscle
formed by repeating A and I bands in the myofibrils
How do muscles contract?
The myosin heads swing inward, pulling the thin filaments towards the center of the sarcomere.
What happens during Botulinum toxin (Botox)?
Blocks release of neurotransmitter at the NMJ so muscle contraction can not occur
single-unit smooth (visceral) muscle
Located in the walls of all hollow organs, contracts rhythmically, has gap junctions between cells, exhibits spontaneous action potentials and is quite common.
What is the major difference between glycolysis and oxidative phosphorylation?
Oxidative phosphorylation is aerobic and generates 36 more ATPs than anaerobic pathways like glycolysis, which only produces 2 ATPs.
sarcomeres, muscle fiber and muscle shorten*thick and thin filaments do not change in length
*can't generate anymore force or tension in full contraction
86. What type of muscle fiber is a type I fiber?
red, slow twitch fiber
What is a Motor Unit
A somatic motor neuron and all the muscle cells (fibers) it innervates
What is the tetanus-twitch ratio?
The amount of force produced in a tetanus compared to the amount of force produced in a twitch; the force of tetanus is typically several times that of a twitch.
What are the three binding sites of troponin?
- tropomyosin- actin- calcium ion (Ca2+)
What are the major routes of Ca2+ into and out of the cytoplasm of smooth muscle cells?
Calcium enters through voltage-gated channels, ligand-gated channels, "leak" channels, and from the SR.
Second messengers can also cause calcium release from the SR
Calcium exits the cell or enters the SR via a calcium ATPase pump; it also exits the cell via a Ca2+/Na+ exchanger
What is series elastic component? What is the source of this elasticity.
term given to the elasticity found in the crossbridges, myofilaments, sacrolemma, and tissues connecting muscle cells to bones.
some elasticity in muscle tissue and some in connective tissue
What is the function of MgCl2 in muscle contraction?
It is the cofactor for the ATPase
What role does Ca++ play in muscle contraction?
Ca++ binds to Troponin which moves it and Tropomyosin out of the way to allow myosin to bind to actin.
/ 173

Leave a Comment ({[ getComments().length ]})

Comments ({[ getComments().length ]})


{[ comment.comment ]}

View All {[ getComments().length ]} Comments
Ask a homework question - tutors are online