Lab Muscle Contraction Model Story

Front 1

A triad is composed of 2 what and 1 what?

Back 1

2 terminal cisternae on either side and the T Tubule, which provides achorage for sarcoplasmic reticulum

Front 2

Skeletal muscles composed of relatively long large cynlindrical cells called

Back 2

fibers

Front 3

The nuclei of skeletal muscle pushed peripherally by longitudinally arranged _____ that fill the sarcoplasm

Back 3

myofibrils

Front 4

Myofibrils are made up of even smaller threadlike structures called

Back 4

myofilaments

Front 5

The myofilaments are composed largely of actin and

Back 5

myosin, contractile proteins

Front 6

The contractile unit of a muscle is called a

Back 6

sarcomere

Front 7

The indentation of the sarcolemna, plasma membrane of muscle, are called

Back 7

t tubules

Front 8

The tubules run between cross channels called

Back 8

terminal cisternae

Front 9

The combination of t tubule and terminal cisternae at either end is called a

Back 9

triad

Front 10

Each muscle fiber enclosed by areolar connective tissue sheath called

Back 10

endomysium

Front 11

Several muscle fibers aer wrapped by a collagenic membrane called

Back 11

perimysum

Front 12

The junction between a nerve fiber or axon and a muscle cell is called a

Back 12

neuromuscular junction

Front 13

The neuron and all the muscle cells it stimulates is called a

Back 13

motor unit

Front 14

The neuron and muscle fiber membranes do not touch, but are separated by a small, fluid-filled gap called a

Back 14

synaptic cleft

Front 15

Each myofibril is a bundle of parallel protein filaments called

Back 15

myofilaments

Front 16

Atoms

Back 16

small building blocks of matter

Front 17

Sarcoplasm is the cytoplasm of a muscle fiber; while, sarcolema is the _______ ________of a fiber

Back 17

plasma membrane

Front 18

The dilated ends of the sarcoplasmic reticulum extending from one side of muscle fiber to another.

Back 18

Terminal cisternae

Front 19

Thick filament

Back 19

a myofilament made of myosin

Front 20

thin filament

Back 20

a myofilament made of troponin, tropomysosin, and actin

Front 21

Mixtures

Back 21

combination of two substances that maintain their own chemical identity

Front 22

The H band is a lighter region in the middle of an ___ _____ that contains thick filaments only. Thin filaments do not _____ this far into A band in relaxed muscle.

Back 22

A band
reach

Front 23

The M line is a dark line in the middle of a H band, and the origin of the ______ _________.

Back 23

thick filaments

Front 24

The I band is a _______ _______composed of thin filaments only.

Back 24

light band

Front 25

The Z disc is a protein disc to which thin filaments and elastic filaments are ________ at each end of a ________. Appears as narrow dark line in the middle of an _____ _____.

Back 25

anchored
sarcomere
I band

Front 26

The distance from one ____ band to the next, contractile unit of a muscle fiber.

Back 26

Z

Front 27

The neuromuscular junction is the functional connection between the distal end of a nerve fiber and the middle of a ______ fiber.

Back 27

muscle

Front 28

The synaptic knob is the dilated tip of a nerve fiber; contains _______ vessicles.

Back 28

synaptic

Front 29

Synaptic cleft is a gap between the synaptic knob and ________

Back 29

sarcolemna

Front 30

Ach is the neurotransmitter released by a ______ _____ _____that stimulates a skeletal muscle cell.

Back 30

somatic motor fiber

Front 31

A nerve signal arrives at the synaptic knob and stimulates voltage-regulated calcium gates to ______

Back 31

open

Front 32

Calcium stimulates exocytosis of the synaptic vessicles which release _____ into the synaptic cleft.

Back 32

ACH

Front 33

Ach diffuses across the _______ ______ and binds to receptor proteins on the sarcolemna.

Back 33

synaptic cleft

Front 34

These receptors are ligand-gated ____ _____.

Back 34

ion gates

Front 35

2 Ach molecules must bind to each ______ to open the gate.
When this happens, Na+ diffuses quickly into cell and K+ diffuses out.

Back 35

receptor

Front 36

As a result of Na+ in and K+ out, the sarcolemna reverses ______. The rapid fluctutation in membrane voltage at the motor end plate Is

Back 36

polarity
end plate potential or epp

Front 37

Areas of the sarcolemna next to the motor end plate, have voltage-regulated ion gates that open in response to _____

Back 37

EPP.

Front 38

4 Some opening of gate specific to Na+ some specific to K+. Ion movements create _______ ________

Back 38

action potential

Front 39

A wave of action potentials spreads from _____ _________ in all directions. When the excitation reaches the t tubules, it continues down into sarcoplasm.

Back 39

end plate

Front 40

Voltage regulated ion gates in the t tubules are linked to calcium channels in the terminal ______ of the SR.

Back 40

cisternae

Front 41

7 Gates in the SR open and ______ diffuses out.

Back 41

calcium

Front 42

8 Calcium binds to the troponin of the _____ _______

Back 42

thin filament

Front 43

9 The troponin-tropomyosin complex changes shape and sinks deeper into the groove of the thin filament. This exposes the_______ ______of thin filaments and makes them availabe to Mysoin heads.

Back 43

active sites

Front 44

10The myosin head must have an _____ ______bound to it to intiate contraction.

Back 44

ATP molecule

Front 45

11 Myosin ATPase an enzyme in the _____ ______hydrolyzes this ATP.

Back 45

Mysoin head

Front 46

12. The energy released by this process ______ the head, cocks it.

Back 46

activates

Front 47

13 The cocked mysoin binds to an exposed active site on the thin filament forming a ________ between myosin and actin.

Back 47

cross- bridge

Front 48

14 Upon binding more ATP, mysoin releases actin, It can now repeat the process. It will hyrolyze ATP and a recovery stroke will allow attachement to a new _______ ______ farther down the thin filament and produce another power stroke.

Back 48

active site

Front 49

15. When nerve signals stop arriving at the NMJ, the synaptic knob stops releasing ______

Back 49

ACh

Front 50

16 As Ach separates from its receptor, ACHE breaks it down into fragments that cannot ________the muscle. At power stroke, thick filament slide over thin filament.

Back 50

stimulate

Front 51

17 Active transport, which requires ATP, pumps begin pumping Ca from cytosol into cisternae. The Ca binds to _________

Back 51

Calsequestrin

Front 52

ATP is needed for muscle contraction as well as muscle ______

Back 52

relaxation.

Front 53

18 As Ca ions dissociate from Troponin they are pumped into the ____ and not replaced.

Back 53

SR

Front 54

19 Tropomyosin moves back to blocking the active sites of actin filament. Mysoin can no longer bind to _____ and the muscle fiber ceases producing tension.

Back 54

actin

Front 55

A band is a dark band formed by parallel _____ ______ that partly overlap the thin filaments.

Back 55

thick filaments

Front 56

a thick filament is a myofilament composed of bunded _____ molecules.

Back 56

myosin

Front 57

A myofibril is a bundle of protein _______

Back 57

microfilaments

Front 58

The smooth endoplasmic reticulum of the muscle fiber is the _______ _______

Back 58

sarcoplasmic reticulum

Front 59

the dilated end sacs of the sarcoplasmic reticulum are ___________ _________

Back 59

terminal cisternae

Front 60

Tubular infoldings of the sarcoplasmic reticulum are _________

Back 60

T tubules

Front 61

A t tubule and the 2 terminal cisternae associated with it constitue a ____

Back 61

triad

Front 62

Actin and myosin are called _________ proteins cause help shorten the muscle fiber.

Back 62

contractile

Front 63

Tropin and tropomyosin are regulatory proteins cause they determine when fiber can or can't ______

Back 63

contract

Front 64

M line is a dark line in middle of ___ band. Origin of thick filaments.

Back 64

H

Front 65

Myofilament a threadlike complex of several hundred contractile _____ molecules

Back 65

protein

Front 66

A bundle of protein microfilaments

Back 66

myofibril

Front 67

The distance from one Z disc to the next

Back 67

sarcomere

Front 68

Fibrous connective tissue surrounding each muscle fiber

Back 68

endomysium

Front 69

Fibrous connective tissue or endomysium continuous with collagen fibers of

Back 69

tendons

Front 70

Endomysium thin sleeve of connective tissue surrounds each ______ ______

Back 70

muscle fiber

Front 71

A thicker connective tissue sheath that wraps muscle fibers into bundles called fasciles.

Back 71

Perimysium

Front 72

Fibrous sheath that surrounds the entire muscle

Back 72

Epimysium

Front 73

Sheet of connective tissue separating muscles or muscle groups from each other

Back 73

Fascia

Front 74

The point where a nerve fiber meets sit target cell

Back 74

synapse

Front 75

Junction between a nerve fiber and a muscle cell

_____ _________

Back 75

neuromuscular junction

Front 76

A neuromuscular junction is also called a ____ _____ ____

Back 76

motor end plate

Front 77

At each synapse, the nerve fiber ends in a bulbous swelling called a _____ _____

Back 77

synaptic knob

Front 78

Small space between the synaptic knob and muscle fiber

Back 78

synaptic cleft

Front 79

Spheroidal organelles of synaptic knob

Back 79

synaptic vessicles

Front 80

The insulating layer around a nerve fiber

Back 80

Myelin Sheath

Front 81

The end of the nerve cell, where it connects with another nerve cell, or a different type of cell, such as a muscle. Here that electrical signals sent from one cell to another.Distal terminations of the branches of an axon. An axon nerve fiber is a long, slender projection of a neuron, that conducts electrical impulses away from the soma, in order to transmit those impulses to other neurons.

Back 81

Axon terminal

Front 82

A ______ is a single stimulus–contraction–relaxation sequence in a muscle fiber.

Back 82

twitch

Front 83

Twitches vary in duration, and can be divided into a latent period, a _______ phase, and a relaxation phase:

Back 83

contraction

Front 84

A single stimulation produces a single twitch, but twitches in a skeletal muscle do not accomplish anything useful. All normal activities involve _______ muscle contractions.

Back 84

sustained

Front 85

Wave Summation and Incomplete Tetanus occurs when a second stimulus arrives before the relaxation phase has ended, a second, more ______ ______occurs. The addition of one twitch to another in this way constitutes the summation of twitches, or wave summation (Figure 10-13a).

Back 85

powerful contraction

Front 86

The duration of a single twitch determines the maximum time available to produce ______summation. For example, if a twitch lasts 20 msec (1/50 sec), subsequent stimuli must be separated by less than ___msec--a stimulation rate of more than 50 stimuli per second. Rather than refer to stimulation rate, we usually use frequency, which is a number per unit time. In this instance, a stimulus _____ of greater than 50 per second produces wave summation, whereas a stimulus frequency below 50 per second will produce individual _______.

Back 86

wave
20
frequency
twitches

Front 87

If the stimulation continues and the muscle is never allowed to relax completely, tension will rise to a peak A muscle producing peak tension during rapid cycles of contraction and relaxation is in _______ ________.

Back 87

incomplete tetanus

Front 88

If a skeletal muscle is stimulated a second time immediately after the relaxation phase has ended, the contraction that occurs will develop a slightly higher maximum tension than did the contraction after the first stimulation. The increase in peak tension will continue over the first 30–50 stimulations. Thereafter, the amount of tension produced will remain constant at roughly 25 percent of the maximal tension that would be produced in complete tetanus. Because the tension rises in stages, like the steps in a staircase, this phenomenon is called treppe, a German word meaning "stairs." The rise is thought to result from a ______ increase in the concentration of calcium ions in the sarcoplasm, in part because the ion pumps in the sarcoplasmic reticulum are unable to recapture them in the time between stimulations.

Back 88

gradual

Front 89

.The latent period begins at stimulation and typically lasts about 2 msec. Over this period, the action potential sweeps across the sarcolemma and the sarcoplasmic reticulum releases calcium ions. The muscle fiber ____ ____ produce tension during the latent period, because the contraction cycle has yet to begin.

Back 89

does not

Front 90

In the contraction phase, tension rises to a peak. As tension rises, calcium ions are binding to troponin, active sites on thin filaments are being exposed, and cross-_____ interactions are occurring. The contraction phase ends roughly 15 msec after stimulation.

Back 90

bridge

Front 91

The ________ phase then continues for about another 25 msec. During this period, calcium levels are falling, active sites are being covered by tropomyosin, and the number of active cross-bridges is declining

Back 91

relaxation

Front 92

If the stimulation continues and the muscle is never allowed to relax completely, tension will rise to a peak (Figure 10-13b). A muscle producing peak tension during rapid cycles of contraction and relaxation is in _______tetanus.

Back 92

incomplete

Front 93

Complete tetanus is obtained by increasing the ________ rate until the ________phase is eliminated (Figure 10-13c). During complete tetanus, action potentials arrive so rapidly that the sarcoplasmic reticulum does not have time to reclaim the _____ ions. The high Ca2+ concentration in the cytoplasm _______ the contraction state, making it continuous. Virtually all ______ muscular contractions involve complete tetanus of the participating muscle fibers

Back 93

stimulation
relaxation
calcium
prolongs
normal

Front 94

A______contraction in response to a single nerve action potential is called a twitch contraction.

Back 94

muscle

Front 95

The latent period is the time required for the release of ____

Back 95

Ca2+

Front 96

The contraction period represents the time during actual muscle _______.

Back 96

contraction

Front 97

The relaxation period is the time during which Ca2+ is returned to the sarcoplasmic reticulum by _____ transport.

Back 97

active

Front 98

The refractory period is the time immediately following a _______ during which the muscle fiber will not respond to a second stimulus. For skeletal muscle fibers, this period typically ends during the early part of the contraction period.

Back 98

stimulus

Front 99

A ______ effect (treppe) is produced if each successive stimulus occurs after the relaxation period of the previous stimulus. Each successive muscle contraction is greater than the previous one, up to some maximum value. In addition to the accumulation of Ca2+, other factors, such as increases in temperature and changes in pH, may contribute to this “warming up” effect commonly employed by athletes.

Back 99

staircase

Front 100

Wave (temporal) summation occurs if ________ stimuli are applied during the relaxation period of each _______muscle contraction. In this case, each _______ contraction builds upon the previous contraction before its _________ period ends.

Back 100

preceding
consecutive
subsequent
relaxation

Front 101

Incomplete (unfused) tetanus occurs when the _______ of stimuli increases. Successive muscle contractions begin to blend, almost appearing as a single large contraction.

Back 101

frequency

Front 102

Complete ______ tentanus occurs when the frequency of stimuli increases still further. In this case, individual muscle contractions completely _____to produce one large muscle contraction.

Back 102

fused
fuse

Front 103

Isotonic contractions occur when muscles _______ length during a contraction. Picking up a book is an example

Back 103

change

Front 104

By increasing the number of motor units firing, we
can produce a steady increase in muscle force, a process called
recruitment or

Back 104

multiple motor unit summation.

Front 105

a single
contraction of skeletal muscle is called a muscle ----------

Back 105

twitch

Front 106

A tracing of a muscle twitch is divided into
three phases: latent, ______, and relaxation.

Back 106

contraction

Front 107

The latent
period is a short period between the time of stimulation and
the beginning of ________. Although no force is generated
during this interval, chemical _______ occur intracellularly in
preparation for contraction, such as the release of ______
from the sarcoplasmic reticulum.

Back 107

contraction
changes
calcium

Front 108

The first activity you will conduct simulates an isometric,
or fixed length, contraction of an isolated skeletal

Back 108

muscle

Front 109

As the stimulus to a muscle is increased, the amount of force produced by the muscle also

Back 109

increases

Front 110

Maximal
contraction occurs when all the muscle cells have been
activated. Any stimulation beyond this voltage will not increase
the force of contraction. This experiment mimics muscle
activity in vivo where the recruitment of additional motor
units increases the total force produced. This phenomenon is
called.

Back 110

multiple motor unit summation or recruitment.

Front 111

A myogram, a
recording of a muscle twitch, reveals this phenomenon as the
_______, or staircase, effect. For the first few twitches, each
__________ stimulation produces slightly more force than the
previous contraction as long as the muscle is allowed to fully
_____ between stimuli, and the stimuli are delivered relatively
______ together. Treppe is thought to be caused by increased
efficiency of the ______systems within the cell and increased
availability of intracellular calcium.

Back 111

treppe
enzyme
successive
relax
close

Front 112

Wave summation is achieved by increasing the _______
frequency, or rate of stimulus delivery to the muscle. Wave
summation occurs because the muscle is already in a partially ________ state when subsequent stimuli are delivered.

Back 112

stimulus
contracted

Front 113

Wave summation is achieved by increasing the _______
frequency, or rate of stimulus delivery to the muscle. Wave
__________ occurs because the muscle is already in a partially ________ state when subsequent stimuli are delivered.

Back 113

stimulus
summation
contracted

Front 114

Passive force is generated by ________ the muscle and is due to the elastic properties of the tissue itself.
This passive force is largely due to the protein titin,
which acts as a molecular bungee cord.

Back 114

stretching

Front 115

Active force is generated
by the _________contraction of the muscle.

Back 115

physiological

Front 116

During isotonic contraction, muscle length changes, but the force produced stays the same (iso  same, tonic  force).Unlike the isometric exercise in which both ends of the muscle are held in a fixed position, one end of the muscle remains
_____ in the isotonic contraction exercise.

Back 116

free

Front 117

Amotor unit consists of a motor neuron and all of the muscle fibers it innervates.
Motor neurons direct muscles when and when not to contract. A motor neuron and
a muscle cell intersect at what is called the ________ junction.

Back 117

neuromuscular

Front 118

Specifically,
the neuromuscular junction is where the axon _______ of the neuron meets a specialized
region of the muscle cell’s plasma membrane. This specialized region is
called the ______ _______ _______

Back 118

terminal
motor end plate

Front 119

An action potential (depolarization) in a motor neuron
triggers the release of acetylcholine, which diffuses into the muscle plasma membrane
(also known as the sarcolemma). The acetylcholine binds to receptors on the
_______ cell, initiating a change in ion permeability that results in ________of the muscle plasma membrane, called an end-plate potential. The end-plate potential,
in turn, triggers a series of events that results in the contraction of a muscle
cell. This entire process is called excitation-contraction coupling.

Back 119

depolarization
muscle

Front 120

muscle twitch—the mechanical ______ to a single action
potential.

Back 120

response

Front 121

the latent period, which is the period of time that elapses between the generation of an action potential in a muscle cell and the start of muscle ________;

Back 121

contraction

Front 122

the contraction phase, which starts at the
Skeletal Muscle Physiology
E X E R C I S E 2
O B J E C T I V E S
1. To define motor unit, twitch, latent period, contraction phase, relaxation
phase, threshold, summation, tetanus, fatigue, isometric contraction,
and isotonic contraction
2. To understand how nerve impulses trigger muscle movement
3. To describe the phases of a muscle twitch
4. To identify threshold and maximal stimuli
5. To understand the effect of increases in stimulus intensity on a muscle
6. To understand the effect of increases in stimulus frequency on a muscle
7. To demonstrate muscle fatigue
8. To explain the differences between isometric and isotonic muscle
contractions
17
end of the latent period and ends when muscle tension peaks;
and the relaxation phase, which is the period of time from
peak tension until the end of the muscle _______ (Figure

Back 122

contraction

Front 123

y definition, the threshold is the minimal _______ needed
to cause a depolarization of the muscle plasma membrane
(sarcolemma.) The threshold is the point at which sodium
ions start to move into the cell (instead of out of the cell) to
bring about the membrane __________

Back 123

stimulus
depolarization

Front 124

Treppe is the _______ increase in force generated when a muscle is stimulated at a sufficiently _____ frequency. At such a frequency, muscle twitches follow one another ______, with each successive twitch peaking slightly higher than the one before. This step-like increase in force is why treppe is also known as the ________phenomenon.

Back 124

progressive
high
closely
staircase

Front 125

When a muscle is stimulated ______, such that the stimuli
arrive one after another within a short period of time,
twitches can overlap with each other and result in a stronger
muscle _______ than a stand-alone twitch. This phenomenon
is known as ______. Summation occurs when muscle
fibers that have already been ________ once are stimulated
again, before the fibers have relaxed.

Back 125

repeatedly
summation
stimulated
contraction
wave summation
contracted

Front 126

However,
if stimuli continue to be applied frequently to a muscle
over a prolonged period of time, the muscle force will eventually
reach a plateau—a state known as _______. If stimuli
are applied with even greater frequency, the twitches will begin
to fuse so that the peaks and valleys of each twitch become
indistinguishable from one another—this state is
known as complete (fused) tetanus. The stimulus frequency
at which no further increases in force are generated by the
muscle is the _________ _________ ________.

Back 126

tetanous
maximal tetanic tension

Front 127

Fatigue is a decline in a muscle’s ability to maintain a constant
force of contraction after prolonged, repetitive stimulation.
The causes of fatigue are still being investigated, though
in the case of high-intensity exercise, lactic acid buildup in
muscles is thought to be a factor. In low-intensity exercise,fatigue may be due to a depletion of _____reserves.

Back 127

energy

Front 128

if stimuli continue to be applied frequently to a muscle
over a prolonged period of time, the muscle force will eventually reach a _____—a state known as _____. If stimuli are applied with even greater frequency, the twitches will begin
to _____ so that the peaks and valleys of each twitch become
indistinguishable from one another—this state is
known as _______ _______ _______

Back 128

plateau
tetanus.
fuse
complete fused tetanus

Front 129

By increasing the number of _____ _____ firing, we
can produce a steady increase in muscle force, a process called
recruitment or _______ motor unit summation

Back 129

motor units
multiple

Front 130

a single contraction of skeletal muscle is called a muscle _____

Back 130

twitch

Front 131

The latent period is a short period between the time of stimulation and the beginning of ________. Although no force is generated during this interval, chemical changes occur intracellularly in
preparation for contraction, such as the release of ________from the sarcoplasmic reticulum.

Back 131

contraction
calcium

Front 132

Relaxation takes place when contraction has ended
and the muscle returns to its normal ______ _____and length.

Back 132

resting state

Front 133

isometric\ is a or ____ _____, contraction of an isolated skeletal muscle.

Back 133

fixed length

Front 134

Active force is produced during
muscle contraction, while passive force results from the muscle
being stretched (much like a rubber band). The total force
is the sum of _____ and ++++Active force is produced during
muscle contraction, while passive force results from the muscle
being stretched (much like a rubber band). The total force
is the sum of active and passive forces.Active force is produced during
muscle contraction, while passive force results from the muscle
being stretched (much like a rubber band). The total force
is the sum of _____ and ____ forces. forces.

Back 134

passive and active

Front 135

the recruitment of additional motor
units increases the total force produced. This phenomenon is
called _____ _____ _____ summation or recruitment.

Back 135

multiple motor unit

Front 136

For the first few twitches, each
successive stimulation produces slightly ______ _____than the previous contraction as long as the muscle is allowed to fully _____ between stimuli, and the stimuli are delivered relatively close together. Treppe is thought to be caused by increased efficiency of the enzyme systems within the cell and increased availability of _________ _________.

Back 136

relax
more force
intracellular calcium

Front 137

Multiple motor unit summation relied on increased stimulus intensity in that simulation. Another way to increase force is by wave, or _______, summation.Wave summation is achieved by increasing the stimulus __________, or rate of stimulus delivery to the muscle. Wave summation occurs because the muscle is already in a partially
_______ state when subsequent stimuli are ______.

Back 137

temporal
frequency
contracted
delivered

Front 138

Tetanus can be considered an extreme form of wave
summation that results in a steady, sustained contraction. In
effect, the muscle does not have any chance to relax because
it is being stimulated at such a high frequency. This fuses the _____ _____so that we observe a smooth tracing

Back 138

force peaks

Front 139

activated units are maximally
contracted. By increasing the number of motor units firing, we can produce a _____increase in muscle force, a process called
recruitment or _____ _____ ______ ______.

Back 139

steady
multiple motor unit summation

Front 140

a single contraction of skeletal muscle is called a _____ ____

Back 140

muscle twitch

Front 141

A tracing of a muscle twitch is divided into three phases: -------, ______, and ______

Back 141

latent
contraction
relaxation

Front 142

The latent
period is a short period between the time of _______ and the beginning of ________.

Back 142

stimulation
contraction

Front 143

During the period of ______, chemical changes occur intracellularly in
preparation for _______, such as the release of _______from the sarcoplasmic reticulum.

Back 143

latency
contraction
calcium

Front 144

an isometric is a
_____ ______ contraction of an isolated skeletal muscle.

Back 144

fixed length

Front 145

As more voltage is delivered
to the whole muscle, more muscle fibers are activated
and the total force produced by the muscle is _______ Maximal contraction occurs when all the muscle cells have been activated. Any stimulation beyond this voltage will not increase
the force of ________.

Back 145

increased
contraction

Front 146

the recruitment of additional _____ _____ increases the total _____ produced. This phenomenon is
called multiple _____ ____ ____ or recruitment.

Back 146

motor units
force
multiple motor unit

Front 147

When a muscle first contracts, the ______it is able to produce is _____ than the force it is able to produce in ________ contractions
within a relatively narrow time span. A myogram, a
recording of a muscle twitch, reveals this phenomenon as the ______, or staircase, effect.

Back 147

force
less
subsequent
treppe

Front 148

Treppe is thought to be caused by increased
efficiency of the ______systems within the cell and increased availability of ______ _______

Back 148

enzyme
intracellular calcium

Front 149

with single stimuli, multiple
motor unit summation is one way to ______the amount of
force produced by muscle.Another
way to increase ______ is by _____, or temporal, summation.
Wave summation is achieved by increasing the stimulus
_______, or rate of stimulus delivery to the muscle.by increasing the stimulus
frequency, or rate of stimulus delivery to the muscle.

Back 149

increase
force
wave
frequency

Front 150

Wave
summation occurs because the muscle is already in a partially ______ state when subsequent______are delivered.

Back 150

contracted
stimuli

Front 151

______ can be considered an extreme form of wave
summation that results in a steady, _______contraction. In
effect, the muscle does not have any chance to relax because
it is being stimulated at such a _____frequency. This fuses the _____ _____so that we observe a smooth tracing.

Back 151

tetanus
sustained
high
force peaks

Front 152

the stimulus rate above which
there appears to be no ______ _____ in force.
stimuli/sec
This rate is the______frequency, also called tetanus.

Back 152

significant increase
fusion

Front 153

An axon terminal is a _____knob which form synapses or _______between neurons or _____ cells.

Back 153

synaptic
junctions
effector

Front 154

Dendrites bear receptors for ___________ released by other neurons

Back 154

neurotransmitters

Front 155

myelin sheath

Back 155

fatty insulating fiber layer underneath plasma membrane of neuron.

Front 156

Myelin fibers formed by ______ _____

Back 156

Schwann Cell

Front 157

_____knob which form synapses or _______between neurons or _____ cells.

Back 157

synaptic
junctions
effector