Muscle Tissue

Front 1

Which muscle have the largest mitochondria

Back 1

Cardiac muscles have the largest

Front 2

Exposure to clostridium tetani causes continuous release of ACh, what is the effect on smooth muscle

Back 2

The continuous release of ACh has no effect of this muscle after the introduction of Clostridium Tetani

Front 3

Competitive weight lifters work to increase the

Back 3

average number of myofibrils/muscle fibers

Front 4

In treppe, twitches become progressively ________ because

Back 4

Twitches become progressively stronger calcium accumulates in the sarcoplasm faster than the sarcoplasmic reticulum can reabsorb it

Front 5

Sarcolemma of a resting muscle fiber is most permeable to

Back 5

potassium

Front 6

Why does cardiac muscle have very little capacity for regenerating

Back 6

Because it lacks satellite discs

Front 7

When does skeletal muscle generate the greatest tension?

Back 7

Skeletal muscle generates the greatest tension when it is partially stretched before being stimulated

Front 8

What is the function of creatine kinase?

Back 8

It catalyzes transfer from phosphate from CP to ADP

Front 9

Deficiency in ACh receptors leads to

Back 9

muscle paralysis in myasthenia gravis

Front 10

What is incomplete tetanus?

Back 10

Incomplete tetanus is if one nerve stimulus arrives at a muscle fiber so soon that the fiber has only partially relaxed from the previous twitch

Front 11

What is an isotonic contraction?

Back 11

Shortening of a muscle while maintaining constant tension

Front 12

In a relaxed muscle fiber, the active sites of the actin are blocked by _______

Back 12

Tropomyosin

Front 13

What is the purpose of a triad?

Back 13

A triad allows for calcium release when the muscle is excited

Front 14

One somatic neuron is stimulated by ____ muscle fibers?

Back 14

One somatic neuron is stimulated by zero muscle fibers

Front 15

A myofilament that connects a thick filament and anchors it into a z disc called an ______ _______

Back 15

elastic filament

Front 16

Skeletal muscles depend solely on

Back 16

the sarcoplasmic reticulum and its calcium source

Front 17

Smooth muscle contracts and relaxes _____ ______ than skeletal muscle

Back 17

more slowly

Front 18

Varicosities release

Back 18

norepinephrine

Front 19

What would happen if ACh was inhibited at the synapse?

Back 19

Tetanus

Front 20

Collagen is

Back 20

elastic

Front 21

What is the smooth ER of a muscle fiber?

Back 21

Sarcoplasmic reticulum

Front 22

What are intercalated discs of cardiac muscle?

Back 22

Numerous gap junctions in muscular tissue

Front 23

What makes a triad?

Back 23

two terminal cisternau and one t-tubule make a

Front 24

The deltoid muscle is

Back 24

extrinsic

Front 25

Calcium channel blockers

Back 25

prevent calcium from entering the smooth muscle, allowing smooth muscle to relax

as a result, blood pressure decreases because the arteries vasodilate

Front 26

During an isometric contraction, what happens to muscle length?

Back 26

The muscle length does not change.

Front 27

The minimum stimulus needed to cause muscle contraction is called

Back 27

the threshold

Front 28

The contraction strength of smooth muscle is relatively independent of its resting length partly because

Back 28

it does not have Z discs.

Front 29

Muscle fibers are arranged in bundles called

Back 29

fascicles

Front 30

Loss of muscle mass from lack of activity is termed

Back 30

atrophy

Front 31

Release of ACh

Back 31

increases permeability of the sarcolemma.

Front 32

Which muscle(s) can contract without the need for nervous stimulation?

Back 32

cardiac and smooth muscles can contract without the need for nervous stimulation

Front 33

Which of the following would be caused by contraction of smooth muscle?

Back 33

goose bumps

Front 34

The protein that acts as a calcium receptor in skeletal muscle is

Back 34

troponin

Front 35

Where are single-unit smooth muscles found?

Back 35

most blood vessels and viscera as circular and longitudinal muscles

Front 36

Periosteum is

Back 36

NOT a muscle tissue

Front 37

The ability of the muscle cell to stretch under tension is known as

Back 37

extensibility

Front 38

T-tubules are extensions of the _____ in skeletal muscle.

Back 38

sarcolemma (plasma membrane)

Front 39

One motor neuron can stimulate up to _____ muscle fiber(s).

Back 39

1000

Front 40

Fatigue can be caused by all of the following except

Low acetylcholine supplies
pH imbalance
Excess of myoglobin
Excess of lactic acid
Reduced ATP concentration

Back 40

excess myoglobin

Myoglobin supplies oxygen for a limited amount of aerobic respiration at onset; it is rapidly depleted

Front 41

What are the contractile proteins?

Back 41

Actin
Myosin

Front 42

Muscle fibers are grouped in bundles called fascicles by which layer of connective tissue?

Back 42

perimysium

Front 43

A brief activity using maximum muscular effort (weight-lifting) is fueled best by the

Back 43

glycogen-lactic acid system (anaerobic)

Front 44

Smooth muscles lack..

Back 44

T-tubules

Front 45

What is the major purpose of the muscular system?

Back 45

Converting the chemical energy in ATP into the mechanical energy of motion

Front 46

This connective tissue of the muscle separates neighboring muscles or muscle groups from each other and the subcutaneous tissue

This tissue is made of dense regular connective tissue

Back 46

Fascia

Front 47

This layer of connective tissue of muscle forms a fibrous sheath around the entire muscle, is made of denser regular connective tissue

Back 47

Epimysium; its outer surface grades into the fascia

Front 48

This layer of connective tissue surround fascicles (bundles of muscle fibers), and carry larger nerves and blood vessels and stretch receptors

Back 48

Perimysium

Front 49

This layer of connective tissue of muscle is a thin sleeve of loose connective tissue that surrounds each muscle fiber (cell)
it allows room for capillaries and nerve fibers to reach each muscle fiber

Back 49

Endomysium

Front 50

List the layers of connective tissue of muscle from superficial to deep

Back 50

Fascia
Epimysium
Perimysium
Endomysium

Front 51

Deep Fascia are found between

Back 51

adjacent muscles

Front 52

Superficial fascia, AKA _________ are found between ________________________ and contain _________________

Back 52

between skin and muscles and contain adipose tissue

Front 53

Characteristics of tendons

Back 53

Attachments between muscle and bone
Dense-regular connective tissue composed of collagen fibers
The epimysium surrounding the entire muscle is continuous with collagen fibers of tendons
Which in turn, are continuous with connective tissue (periosteum) of bone

Front 54

Collagen is somewhat

Back 54

extensible and elastic

Front 55

Characteristics of collagen

Back 55

Collagen stretches slightly under tension and recoils when released
-resists excessive stretching and protects muscle from injury
-returns muscle to its resting length
-contribute to power output and muscle efficiency

Front 56

What determines the strength of a muscle and the direction of its pull?

Back 56

Shape and orientation of its fascicles

Front 57

Fusiform muscles are

Back 57

thick in the middle and tapered at the ends

Front 58

Triangular (convergent) muscles are

Back 58

broad at origin and tapering to a narrower insertion

Front 59

Parallel muscles have ______ fascicles and ______________________________

Back 59

parallel fascicles; can span longer distances than other shapes

Front 60

Circular muscles

Back 60

are skeletal muscles that act as sphincters, and ring around the body opening

Front 61

Pennate muscles

Back 61

fascicles insert obliquely on a tendon (feather shaped)

Front 62

Tendons attach _____ to ______

Back 62

muscle to bone

Front 63

Aponeurosis

Back 63

tendon is a broad, flat sheet

Front 64

Which skeletal muscles do not insert on bone, but in dermis of the skin

Back 64

muscles of facial expression

Front 65

This type of muscle modifies the direction of movement, stabilizes the nearby joints and aids the prime mover

Back 65

synergist

Front 66

This type of muscle prevents excessive movement and injury, relaxes to give the prime mover control over an action

Back 66

antagonist- also opposes the prime mover

Front 67

This type of muscle prevents movement of bone

Back 67

fixator

Front 68

Intrinsic muscles

Back 68

contained within a region, both of its origin and insertion are in the same region (phalanges)

Front 69

Extrinsic muscles

Back 69

act on a designated region but have orgins elsewhere

Front 70

Responsiveness (exciteability)

Back 70

to chemical signals, stretch and electrical changes across the plasma membrane

Front 71

Conductivity

Back 71

local electrical change triggers a wave of excitation that travels along the muscle fiber

Front 72

Contractility

Back 72

shortens when stimulated

Front 73

Extensibility

Back 73

capable of being stretched between contractions

Front 74

Elasticity

Back 74

returns to its original resting length after being stretched

Front 75

This muscles is

voluntary
striated
and attached to one or more bones

Back 75

Skeletal muscle

Front 76

What are striations a result of?

Back 76

Overlapping of internal contractile proteins

Front 77

What is a skeletal muscle made of

Back 77

muscle cells, called muscle fibers or myofibers

Front 78

How long are muscle fibers or myofibers of a skeletal muscle?

Back 78

30 cm long

Front 79

Myofibers are muscle cells composed of _________ which are composed of _________

Back 79

myofibrils; myofilaments

Front 80

Myofibrils are

Back 80

long protein bundles that occupies the main portion of the interior of a muscle fiber.

They make up myofibers

Myofibrils are composed of myofilaments

Front 81

Myofilaments make up ______ which make up __________; they are

Back 81

myofibrils which make up myofibers; they are a protein microfilament responsible for muscle cell contraction

Front 82

Myofilaments are composed of ______ or ______ proteins

Back 82

myosin or actin proteins

Front 83

Sarcolemma

Back 83

plasma membrane of a muscle fiber

Front 84

Sarcoplasma

Back 84

cytoplasm of a muscle fiber

Front 85

Mitochondria

Back 85

packed in spaces between myofibrils

Front 86

Terminal Cisternae

Back 86

dilated end-sacs of SR which cross muscle fiber from one side to the other- store calcium

Front 87

T tubule

Back 87

tubular infoldings of the sarcolemma which penetrate through the cell and emerge on the other side

Front 88

What are the two internal proteins of myofibers?

Back 88

Glycogen and Myoglobin

Front 89

Glycogen, an internal protein of myofibers, are

Back 89

stored in abundance to provide energy with heightened exercise

Front 90

Myoglobin, an internal protein of myofibers, are

Back 90

red pigment that stores oxygen needed for muscle activity

Front 91

Glycogen and myoglobin are long protein bundles that occupy the main portion of the sarcoplasm, AKA ______ that make up ______

Back 91

internal proteins that make up myofibers

Front 92

How do myofibers repair?

Back 92

by fibrosis rather than regeneration of functional muscle

Front 93

Myofibers are made up of multiple nuclei that are pressed against the inside of the sarcolemma, as well as stem cells that fuse to form each muscle fiber called ______ and unspecializd myoblasts remaining between the muscle fiber and endomysium called _________ ________

Back 93

myoblasts are stem cells that fuse to form each muscle fiber

satellite cells are unspecialized myoblasts remaining between the muscle fiber and endomysium

Front 94

The three kinds of myofilaments found in a myofibril are called

Back 94

Thin, thick and elastic filaments

Front 95

These are stem cells that fuse to form each muscle fiber

Back 95

Myoblasts

Front 96

These are unspecialized myoblasts remaining between the muscle fiber and endomysium

Back 96

Satellite cells

Front 97

Thin filaments are found in myofibrils that are made of

Back 97

myosin protein

Front 98

Thick filaments are found in myofibrils that are made of

Back 98

primarily actin proteins

Front 99

Elastic filaments are found in myofibrils that are made of

Back 99

titin (connectin) proteins

Front 100

Thick myofilaments are made of several hundred _________ molecules. Their heads are directed ______ in a helical array around the bundle.

Back 100

myosin; outward

Front 101

Thin myofilaments are made of three things:

Back 101

Fibrous (F) actin
Tropomyosin
and
Troponin complex

Front 102

Fibrous (F) actin, found in ______ ______, are

Back 102

found in thin myofilaments, are two intertwined strands, a string of globular (G) actin subunits each with an active site that can bind to head of myosin molecule

Front 103

Tropomyosin, found in ____ _____________,

Back 103

thin myofilaments, each block 6 or 7 active sites on G actin subunits

Front 104

The troponin complex of ______ ________ are

Back 104

thin myofilaments, are small, calcium-binding proteins on each tropomyosin molecule

Front 105

Elastic Myofilaments are made of _______ (______)

Back 105

titin (connectin)

Front 106

titin (connectin) make up _____ ________ and are characterized as

Back 106

elastic myofilaments and are characterized by huge springy protein, they flank each thick filament and anchor it to the Z disc, help the cell recoil to its resting length (elastiity), keep thick and thin filaments aligned (help stabilize the thick filament and center it between the thin filaments), and prevent overstretching

Front 107

The regulatory proteins, _____ and ______, act

Back 107

tropomyosin and troponin, act like a switch that states and stops contraction

Front 108

How i contraction activated?

Back 108

By the release of calcium into sarcoplasm and its binding to troponin

Front 109

What happens after calcium enters the sarcoplasm and binds to troponin?

Back 109

Troponin changes shape and moves tropomyosin off the active sites on actin

Front 110

What are the function of accessory proteins

Back 110

Accessory proteins of thick and thin filaments act to anchor the myofilaments, regulate length of myofilaments, and align myofilaments for optimal effectiveness

Front 111

What is the most clinically important accessory protein? What is its function?

Back 111

Dystrophin – most clinically important
links actin in outermost myofilaments to transmembrane proteins and eventually to fibrous endomysium surrounding the entire muscle cell
transfers forces of muscle contraction to connective tissue around myofiber
genetic defects in dystrophin produce disabling disease muscular dystrophy

Front 112

Group of hereditary diseases in which skeletal muscles degenerate & are replaced with scar tissue and adipose tissue

Back 112

Muscular Dystrophy

Front 113

Fascioscapulohumeral MD is

Back 113

facial & shoulder muscle only
affects both sexes equally

Front 114

Myostatin is a protein that limits muscle growth. Some mutations in the gene coding for myostatin can lead to the production of non-functional protein. What would be the phenotypic result of this mutation in a baby?

Back 114

Baby is abnormally muscular

Front 115

What is the function of myosin and actin

Back 115

function in cellular motility, mitosis, transport of intracellular material

Front 116

A band

Back 116

– dark – A stands for anisotropic
part of A band where thick and thin filaments overlap is especially dark
H band in the middle of A band – just thick filaments
M is in the middle of the H band

Front 117

H band

Back 117

middle of A band- just thick filaments

Front 118

I band

Back 118

alternating lighter band-
I= isotropic

Front 119

Z disc

Back 119

– provides anchorage for thin filaments and elastic filaments
bisects I band

Front 120

M is the middle of the

Back 120

H band

Front 121

A sarcomere is a

Back 121

segment of the myofibril from one z disc to the next

Front 122

functional contractile unit of the muscle fiber

Back 122

Sarcomere

Front 123

Muscles shorten when

Back 123

individual sarcomeres shorten and pull z discs closer to eachother as thick and thin filaments slide past eachother

Front 124

Segment from Z disc to Z disc

Back 124

Sarcomere

Front 125

During muscle contraction, what happens the the thick and thin filaments?

Back 125

Neither change length during shortening, only the amount of overlap changes

Front 126

Skeletal muscle must be stimulated by a ______ or it will not contract

Back 126

nerve

Front 127

What happens if nerve connections are severed or poisoned, a muscle is _________

Back 127

paralyzed

Front 128

Denervation atrophy is

Back 128

shrinkage of paralyzed muscle when connection not restored

Front 129

Somatic motor neurons

Back 129

stimulate skeletal muscle
cell bodies are located in the brainstem and spinal cord

Front 130

Somatic motor fibers

Back 130

– axons of somatic motor neurons
lead to the skeletal muscle
each nerve fiber branches out to a number of muscle fibers
200 myofibers on average are controlled by a single somatic motor neuron
each myofiber is supplied by only one motor neuron
one nerve fiber and all the muscle fibers innervated by it is a motor unit

Front 131

Motor unit=

Back 131

one nerve fiber and all the muscle fibers innervated by it

Front 132

Myofibers of one motor unit

Back 132

dispersed throughout the muscle
contract in unison
produce weak contraction over wide area
provides ability to sustain long-term contraction as motor units take turns contracting
postural control
effective contraction usually requires the contraction of several motor units at once

Front 133

Average motor unit

Back 133

200 muscle fibers/neuron

Front 134

Small motor units

Back 134

fine degree of control
3-6 muscle fibers per neuron
eye and hand muscles

Front 135

Where are small motor units found?

Back 135

Eye and hand muscles

Front 136

Large motor units have more _______ then _______

Back 136

strength than control

Front 137

Large motor units

Back 137

powerful contractions supplied by large motor units
many muscle fibers per motor unit
gastrocnemius – 1000 myofibers per neuron

Front 138

Synapse

Back 138

point where a nerve fiber meets its target cell

Front 139

Neuromuscular junction (NMJ)

Back 139

- when target cell is a muscle fiber
each terminal branch of the nerve fiber within the NMJ forms separate synapse with the muscle fiber
one nerve fiber stimulates the muscle fiber at several points within the NMJ

Front 140

Synaptic knob

Back 140

swollen end of a nerve fiber

Front 141

The synaptic knob contains ______ _______ filled with _________

Back 141

synaptic vesicles filled with acetylcholine (ACh)

Front 142

Synaptic vesicles undergo _______ releasing ACh into synaptic cleft

Back 142

exocytosis

Front 143

Synaptic cleft

Back 143

- tiny gap between synaptic knob and muscle sarcolemma

Front 144

Schwann cell

Back 144

envelops & isolates all of the NMJ from surrounding tissue fluid

Front 145

How many Ach receptors– proteins are incorporated into muscle cell plasma membrane

Back 145

50 million

Front 146

ACh receptors are

Back 146

junctional folds of sarcolemma
increases surface area holding ACh receptors

Front 147

The lack of ACh receptors can lead to

Back 147

paralysis

Front 148

Basal lamina

Back 148

thin layer of collagen and glycoprotein separates Schwann cell and entire muscle cell from surrounding tissues

contains acetylcholinesterase (AChE)

Front 149

What is acetylcholinesterase (AChE)? Where is it found?

Back 149

breaks down ACh after contraction causing relaxation, found in the basal lamina

Front 150

cholinesterase inhibitors

Back 150

bind to acetylcholinesterase and prevent it from degrading ACh
which leads to spastic paralysis - - a state of continual contraction of the muscles
possible suffocation

Front 151

Tetanus

Back 151

(lockjaw) is a form of spastic paralysis caused by toxin of Clostridium tetani
glycine (inhibitory neurotransmitter) in the spinal cord normally stops motor neurons from producing unwanted muscle contractions
tetanus toxin blocks glycine release in the spinal cord and causes overstimulation and spastic paralysis of the muscles

Front 152

tetanus toxin blocks ____________ release in the spinal cord and causes overstimulation and spastic paralysis of the muscles

Back 152

glycine

Front 153

Flaccid paralysis

Back 153

a state in which the muscles are limp and cannot contract

Front 154

Curare is an example of

Back 154

flaccid paralysis; curare – plant poison used by South American natives to poison blowgun darts

Front 155

In __________ _________, compete with ACh for receptor sites, but do not stimulate the muscles

Back 155

flaccid paralysis

Front 156

Botulism occurs wen a bacterium releases a neurotoxin that prevent motor neurons from releaseing Ach. Now which of te following is not an effect of botulism flaccid paralysis

Back 156

Tetany- muscle gets contracted and cant relax

Front 157

______ ______ and _______ are electrically excitable cells

Back 157

muscle fibers and neurons

Front 158

Electrophysiology

Back 158

- the study of the electrical activity of cells

Front 159

In an unstimulated (resting) cell

Back 159

there are more anions (negative ions) on the inside of the plasma membrane than on the outside
the plasma membrane is electrically polarized(charged)
there are excess sodium ions (Na+) in the extracellular fluid (ECF)
there are excess potassium ions (K+) in the intracellular fluid (ICF)
also in the ICF, there are anions such as proteins, nucleic acids, and phosphates that cannot penetrate the plasma membrane
The inside of the plasma membrane is negatively charged by comparison to its outer surface

Front 160

Voltage (electrical potential)

Back 160

a difference in electrical charge from one point to another

Front 161

Resting membrane potential (RMP) of a myofiber is about _____ ____ and is maintained by

Back 161

90 mV

maintained by sodium-potassium pump

Front 162

Slide 10

Back 162

Muscles part 2

Front 163

4 major phases of contraction and relaxation

Back 163

Excitation
Excitation- contraction coupling
Contraction
Relaxation

Front 164

Excitation

Back 164

the process in which nerve action potentials lead to muscle action potentials

Front 165

Excitation-contraction coupling

Back 165

events that link the action potentials on the sarcolemma to activation of the myofilaments, thereby preparing them to contract

Front 166

Contraction

Back 166

step in which the muscle fiber develops tension and may shorten

Front 167

Relaxation

Back 167

when its work is done, a muscle fiber relaxes and returns to its resting length

Front 168

Excitation (steps 1 and 2)

Back 168

Nerve signal opens voltage-gated calcium channels in synaptic knob
Calcium stimulates exocytosis of ACh from synaptic vesicles
ACh released into synaptic cleft

Front 169

Excitation (steps 3 and 4)

Back 169

2 ACh molecules bind to each receptor protein, opening Na+ and K+ channels.
Na+ enters shifting RMP goes from -90mV to +75mV, then K+ exits and RMP returns to -90mV
quick voltage shift is called an end-plate potential (EPP)

Front 170

Excitation (step 5)

Back 170

Voltage change (EPP) in end-plate region opens nearby voltage-gated channels producing an action potential that spreads over muscle surface

Front 171

Excitation-Contraction Coupling (steps 6 and 7)

Back 171

Action potential spreads down into T tubules
Opens voltage-gated ion channels in T tubules and Ca+2 channels in SR
Ca+2 enters the cytosol

Front 172

Excitation-Contraction Coupling (steps 8 and 9)

Back 172

Calcium binds to troponin in thin filaments
Troponin-tropomyosin complex changes shape and exposes active sites on actin

Front 173

Contraction (steps 10 and 11)

Back 173

Myosin ATPase enzyme in myosin head hydrolyzes an ATP molecule

Activates the head “cocking” it in an extended position
ADP + Pi remain attached

Head binds to actin active site forming a myosin - actin cross-bridge

Front 174

Contraction (steps 12 and 13)

Back 174

Myosin head releasesADP and Pi, flexes pullingthin filament past thick - power stroke

Upon binding more ATP, myosin releases actin and process is repeated
each head performs 5 power strokes per second
each stroke utilizes one molecule of ATP

Front 175

Relaxation (steps 14 and 15)

Back 175

Nerve stimulation & ACh release stop
AChE breaks down ACh & fragments reabsorbed into synaptic knob
Stimulation by ACh stops

Front 176

Relaxation (step 16)

Back 176

Ca+2 pumped back into SR by active transport. Ca+2 binds to calsequestrin while in storage in SR
ATP is needed for muscle relaxation as well as muscle contraction

Front 177

Relaxation (steps 17 and 18)

Back 177

Ca+2 removed from troponin is pumped back into SR

Tropomyosin reblocks the active sites

Muscle fiber ceases to produce or maintain tension

Muscle fiber returns to its resting length
due to recoil of elastic components & contraction of antagonistic muscles

Front 178

Rigor Mortis

Back 178

hardening of muscles and stiffening of body beginning 3 to 4 hours after death
deteriorating sarcoplasmic reticulum releases Ca+2
deteriorating sarcolemma allows Ca+2 to enter cytosol
Ca+2 activates myosin-actin cross-bridging
muscle contracts, but can not relax

Front 179

Rigor mortis peaks about ____ hours after death, then diminishes over the next ____ to ____ hours

Back 179

12; 48-60 hours

Front 180

What causes no contraction

Back 180

If signal doesn’t go down neuron
If Ach not present or not released
If Ach cant bind to receptors
If SR doesn’t release Calcium

Front 181

Length-Tension Relationship

Back 181

the amount of tension generated by a muscle and the force of contraction depends on how stretched or contracted it was before it was stimulated

Front 182

Overly contracted

Back 182

contracted at rest, a weak contraction results
thick filaments too close to Z discs and can’t slide

Front 183

Too stretched

Back 183

before stimulated, a weak contraction results
little overlap of thin and thick does not allow for many cross bridges to form

Front 184

Optimum resting length

Back 184

produces greatest force when muscle contracts



CNS continually monitors & adjusts length of the resting muscle
maintains a state of partial contraction – muscle tone (tonus)
maintains optimum length and makes the muscles ideally ready for action

Front 185

Myogram

Back 185

chart of timing & strength of a muscle contraction

Front 186

A weak, subthreshold, electrical stimulus causes

Back 186

no contraction

Front 187

Threshold

Back 187

the minimum voltage necessary to generate an action potential in the muscle fiber and produce a contraction

Front 188

Twitch

Back 188

a quick cycle of contraction when stimulus is at threshold or higher

Front 189

Phases of a twitch contraction

Back 189

latent period
contraction phase
relaxation phase

Front 190

Latent period

Back 190

2 msec delay between the onset of stimulus and onset of twitch response
time required for excitation, excitation-contraction coupling and tensing of elastic components of the muscle

Front 191

internal tension

Back 191

– force generated during latent period and no shortening of the muscle occurs

Front 192

Contraction phase

Back 192

phase in which filaments slide and the muscle shortens


once elastic components are taut, muscle begins to produce external tension – in muscle that moves a load
short-lived phase

Front 193

Relaxation

Back 193

last phase of twitch contraction


SR quickly reabsorbs Ca+2, myosin releases the thin filaments and tension declines
muscle returns to resting length
entire twitch lasts from 7 to 100 msec

Front 194

Subthreshold stimulus

Back 194

– no contraction at all

Front 195

Threshold intensity and above

Back 195

a twitch is produced
twitches caused by increased voltage are no stronger than those at threshold

Front 196

Muscle Tissue Part 2

Back 196

Slides 30-36

Front 197

Myoglobin

Back 197

supplies oxygen for a limited amount of aerobic respiration at onset
rapidly depleted

Front 198

Muscles meet most of ATP demand by borrowing ______________ from other molecules and transferring them to ___

Back 198

phosphate groups; ADP

Front 199

2 enzyme systems control these phosphate transfers

Back 199

myokinase
creatinekinase

Front 200

myokinase

Back 200

transfers Pi from one ADP to another converting the latter to ATP

Front 201

creatinekinase

Back 201

obtains Pi from a phosphate-storage molecule creatine phosphate (CP)
fast-acting system that helps maintain the ATP level while other ATP-generating mechanisms are being activated

Front 202

Posphagen system

Back 202

ATP and CP collectively
provides nearly all energy used for short bursts of intense activity
one minute of brisk walking
6 seconds of sprinting or fast swimming
important in activities requiring brief but maximum effort
football, baseball, and weight lifting

Front 203

As the posphagen system is exhausted..

Muscles shift to ___________ ________________

Back 203

anaerobic fermentation

Front 204

During anaerobic fermentation

Back 204

muscles obtain glucose from blood and their own stored glycogen
in the absence of oxygen, glycolysis can generate a net gain of 2 ATP for every glucose molecule consumed
converts glucose to lactic acid

Front 205

Glycogen-lactic acid system

Back 205

the pathway from glycogen to lactic acid
produces enough ATP for 30 – 40 seconds of maximum activity

Front 206

After ~40 sec

Back 206

the respiratory and cardiovascular systems “catch up” and deliver oxygen to the muscles fast enough for aerobic respiration to meet most of the ATP demands

Front 207

During aerobic respiration
___ to ______ ATP/glucose are produce

Back 207

36 to 38

Front 208

During aerobic respiration

Back 208

efficient means of meeting the ATP demands of prolonged exercise
one’s rate of oxygen consumption rises for 3 to 4 minutes and levels off to a steady state in which aerobic ATP production keeps pace with demand
little lactic acid accumulates under steady state conditions
depletion of glycogen and blood glucose, together with the loss of fluid and electrolytes through sweating, set limits on endurance and performance

Front 209

Muscle fatigue

Back 209

progressive weakness and loss of contractility from prolonged use of the muscles

Front 210

Causes of muscle fatigue

Back 210

ATP synthesis declines as glycogen is consumed
ATP shortage slows down the Na+ - K + pumps
compromises their ability to maintain the resting membrane potential and excitability of the muscle fibers
Lactic acid lowers pH of sarcoplasm
inhibits enzymes involved in contraction, ATP synthesis, and other aspects of muscle function
Release of K+ with each action potential causes the accumulation of extracellular K+
hyperpolarizes the cell and makes the muscle fiber less excitable
Motor nerve fibers use up their ACh
less capable of stimulating muscle fibers – junctional fatigue
Central nervous system fatigues by unknown processes
less signal output to the skeletal muscles

Front 211

Endurance

Back 211

the ability to maintain high-intensity exercise for more than 4 to 5 minutes

Front 212

What determines endurance

Back 212

determined in large part by one’s maximum O2 uptake(VO2max)

Front 213

maximum oxygen uptake

Back 213

the point at which the rate of oxygen consumption reaches a plateau and does not increase further with an added workload

Front 214

Maximum oxygen uptake characteristics

Back 214

proportional to body size
peaks at around age 20
usually greater in males than females
can be twice as great in trained endurance athletes as in untrained person
results in twice the ATP production

Front 215

Oxygen Debt

Back 215

Heavy breathing continues after strenuous exercise

Front 216

excess post-exercise oxygen consumption (EPOC)

Back 216

the difference between the resting rate of oxygen consumption and the elevated rate following exercise

Front 217

Oxygen Debt is needed

Back 217

replace oxygen reserves that were depleted in the first minute of exercise

replenishing the phosphagen system


oxidizing lactic acid


serving the elevated metabolic rate

Front 218

Oral creatine supplement

Back 218

increases level of creatine phosphate in muscle tissue and increases speed of ATP regeneration


useful in burst type exercises – weight-lifting

Front 219

Carbohydrate loading

Back 219

dietary regimen
packs extra glycogen into muscle cells
extra glycogen is hydrophilic and adds 2.7 g water/ g glycogen
some athletes feel sense of heaviness outweighs benefits of extra available glycogen

Front 220

Fatigue can be caused by all of the following except

Low acetylcholine supplies
pH imbalance
Excess of myoglobin
Excess of lactic acid
Reduced ATP concentration

Back 220

excess myoglobin

Front 221

Slow oxidative (SO), slow-twitch, red, or type I fibers

Back 221

“dark meat”
abundant mitochondria, myoglobin and capillaries - deep red color
adapted for aerobic respiration and fatigue resistance
relative long twitch lasting about 100 msec
soleus of calf and postural muscles of the back

Front 222

Fast glycolytic (FG), fast-twitch, white, or type II fibers

Back 222

“white meat”
fibers are well adapted for quick responses, but not for fatigue resistance
rich in enzymes of phosphagen and glycogen-lactic acid systems
generate lactic acid causing fatigue
less mitochondria, myoglobin, and blood capillaries which gives paler appearance
SR releases & reabsorbs Ca+2 quickly so contractions are quicker
(7.5 msec/twitch)
extrinsic eye muscles, gastrocnemius and biceps brachii

Front 223

You would expect a body-builder to have more _______ muscle fibers than a marathon runner. Slow oxidative fibersFast glycolytic fibers

Back 223

Fast- glycolytic fibers

Front 224

A single muscle has both

Back 224

FG and SO muscle fibers but differ in ratio

Front 225

Ratio of different fiber types have

Back 225

genetic predisposition

Front 226

gastrocnemius is predominantly
___ for quick movements

Back 226

FG

Front 227

soleus is predominantly _____ used for endurance (jogging)

Back 227

SO

Front 228

Muscular strength depends primarily on

Back 228

muscle size

Front 229

fascicle arrangement
vs
strength

Back 229

pennate are stronger than parallel, and parallel stronger than circular

Front 230

Size of motor units

vs strength

Back 230

larger the motor unit the stronger the contraction

Front 231

multiple motor unit summation – recruitment

vs strength

Back 231

when stronger contraction is required, the nervous system activates more motor units

Front 232

temporal summation

Back 232

nerve impulses usually arrive at a muscle in a series of closely spaced action potentials
the greater the stimulation frequency, the more strongly a muscle contracts

Front 233

length – tension relationship

Back 233

a muscle resting at optimal length is prepared to contract more forcefully than a muscle that is excessively contracted or stretched

Front 234

Resistance training (weight lifting)

Back 234

contraction of a muscles against a load that resist movement
a few minutes of resistance exercise a few times a week is enough to stimulate muscle growth
growth is from cellular enlargement
muscle fibers synthesize more myofilaments and myofibrils and grow thicker

Front 235

Endurance training (aerobic exercise)

Back 235

improves fatigue resistant muscles
slow twitch fibers produce more mitochondria, glycogen, and acquire a greater density of blood capillaries
improves skeletal strength
increases the red blood cell count and oxygen transport capacity of the blood
enhances the function of the cardiovascular, respiratory, and nervous systems

Front 236

Required properties of cardiac muscle

Back 236

contraction with regular rhythm

muscle cells of each chamber must contract in unison

contractions must last long enough to expel blood

must work in sleep or wakefulness, with out fail, and without conscious attention

must be highly resistant to fatigue

Front 237

Characteristics of cardiac muscle cells

Back 237

Striated (like skeletal muscle)
Myocytes (cardiocytes or cardiomyocytes) are shorter and thicker

Each myocyte is joined to several others at the uneven, notched linkages – intercalated discs
appear as thick dark lines in stained tissue sections
electrical gap junctions allow each myocyte to directly stimulate its neighbors
mechanical junctions that keep the myocytes from pulling apart

Sarcoplasmic reticulum less developed, but T tubules are larger and admit supplemental Ca2+ from the extracellular fluid

Damaged cardiac muscle cells repair by fibrosis
a little mitosis observed following heart attacks
not in significant amounts to regenerate functional muscle

Front 238

_________ stimulation
contains a built-in __________ that rhythmically sets off a wave of electrical excitation
wave travels through the muscle and triggers ___________ of heart chambers
___________ – because of its ability to contract rhythmically and independently

Back 238

Can contract without need for nervous stimulation
contains a built-in pacemaker that rhythmically sets off a wave of electrical excitation
wave travels through the muscle and triggers contraction of heart chambers
autorhythmic – because of its ability to contract rhythmically and independently

Front 239

Autonomic nervous system (ANS) does send ______fibers to the heart
can increase or decrease heart rate and contraction strength

Back 239

nerve

Front 240

Smooth muscle twitches are

Back 240

Very slow twitches - does not exhibit quick twitches like skeletal muscle
maintains tension for about 200 to 250 msec
gives the heart time to expel blood

Front 241

Cardiac muscle uses __________ respiration

Back 241

aerobic respiration almost exclusively


rich in myoglobin and glycogen
has especially large mitochondria
25% of volume of cardiac muscle cell
2% of skeletal muscle cell with smaller mitochondria

Front 242

Cardiac muscle

Very adaptable with respect to fuel used

Very vulnerable to interruptions of __________ ____________

Highly ________ resistant

Back 242

Very adaptable with respect to fuel used

Very vulnerable to interruptions of oxygen supply

Highly fatigue resistant

Front 243

Smooth muscle


Composed of ________ that have a ________ shape

Back 243

myocytes, fusiform

Front 244

if injured smooth muscle

Back 244

Smooth muscle


Capable of mitosis and hyperplasia

regenerates well

Front 245

Some smooth muscles lack ______ ________, while others receive ________ fibers, not ________ motor fibers as in skeletal muscle

Back 245

Some smooth muscles lack nerve supply, while others receive autonomic fibers, not somatic motor fibers as in skeletal muscle

Front 246

________ needed for muscle contraction comes from the _______ by way of ____________ channels in the sarcolemma

Back 246

calcium; ECF; calcium

Front 247

Sarcoplasmic reticulum of smooth muscle have no

Back 247

T tubules

Front 248

Intermediate filaments in the cytoplasm of smooth muscle provide

Back 248

mechanical linkages between the thin myofilaments and the plasma membrane

Front 249

In smooth muscle, Z discs

Back 249

are absent and replaced by protein plaques well ordered array of protein masses in cytoplasm
dense bodies on the inner face of the plasma membrane

Front 250

Smooth muscle,
are named smooth muscle because

Back 250

reason for the name ‘smooth muscle’
thick and thin filaments are present, but not aligned with each other

Front 251

Multiunit smooth muscle

occurs in

Back 251

some of the largest arteries and pulmonary air passages, in piloerector muscles of hair follicle, and in the iris of the eye

Front 252

Multiunit smooth muscle have a autonomic innervation

Back 252

similar to skeletal muscle
terminal branches of a nerve fiber synapse with individual myocytes and form a motor unit
each motor unit contracts independently of the others

Front 253

Single-unit smooth muscle
are more widespread, and occur in

Back 253

most blood vessels, in the digestive, respiratory, urinary, and reproductive tracts – also called visceral muscle
often in two layers
inner circular
outer longitudinal

Front 254

Single-unit smooth muscle

myocytes of this cell type are electrically coupled to each other by

Back 254

gap junctions

Front 255

Single-unit smooth muscle

directly stimulate each other

Back 255

and a large number of cells contract as a single unit

Front 256

Smooth muscle is involuntary and can contract without __________ ____________

Back 256

nervous stimulation

Front 257

Most smooth muscle is innervated by

Back 257

autonomic nerve fibers

Front 258

stimulate smooth muscle with either _______ or _________

Back 258

stimulate smooth muscle with either acetylcholine or norepinephrine

Front 259

In single unit smooth, each autonomic nerve fibers has up to 20,000 beadlike swelling called ________________

Back 259

In single unit smooth, each autonomic nerve fibers has up to 20,000 beadlike swelling called varicosities

Front 260

Each varicosity of smooth muscle contains

Back 260

each contains synaptic vesicles and a few mitochondria
nerve fiber passes amid several myocytes and stimulates all of them at once when it releases its neurotransmitter
diffuse junctions – no motor end plates; receptors scattered throughout surface
no one-to-one relationship between nerve fiber and myocyte

Front 261

Contraction is triggered by

Back 261

Contraction is triggered by Ca+2, energized by ATP, and achieved by sliding thin past thick filaments

Front 262

During contraction and relaxation Calcium binds to __________ on thick filaments

Back 262

Calcium binds to calmodulin on thick filaments

Front 263

Calcium binds to calmodulin on thick filaments, myosin light-chain kinase is activated
adds phosphate to regulatory protein on myosin head
activates myosin ________ - hydrolyzes ATP
enables myosin similar power and recovery strokes like skeletal muscle

Back 263

Calcium binds to calmodulin on thick filaments, myosin light-chain kinase is activated
adds phosphate to regulatory protein on myosin head
activates myosin ATPase - hydrolyzes ATP
enables myosin similar power and recovery strokes like skeletal muscle
thick filaments pull on thin ones, thin ones pull on dense bodies and membrane plaques
force is transferred to plasma membrane and entire cell shortens
puckers and twists like someone wringing out a wet towel

Front 264

Contraction and relaxation of smooth muscle are very different in comparison to skeletal muscle

latent period in skeletal 2 msec, smooth muscle __ - ___ msec
tension peaks at about ___ msec (0.5 sec)
declines over a period of _____-_____seconds
slows myosin ATPase enzyme and slow pumps that remove Ca+2
Ca+2 binds to calmodulin instead of __________
activates kinases and ATPases that hydrolyze ATP

Back 264

latent period in skeletal 2 msec, smooth muscle 50 - 100 msec
tension peaks at about 500 msec (0.5 sec)
declines over a period of 1 – 2 seconds
slows myosin ATPase enzyme and slow pumps that remove Ca+2
Ca+2 binds to calmodulin instead of troponin
activates kinases and ATPases that hydrolyze ATP

Front 265

latch-bridge mechanism

Back 265

latch-bridge mechanism is resistant to fatigue
heads of myosin molecules do not detach from actin immediately
do not consume any more ATP
maintains tetanus tonic contraction (smooth muscle tone)
arteries – vasomotor tone; intestinal tone; bladder tone
makes most of its ATP aerobically

Front 266

Stretching smooth muscle

Back 266

can open mechanically-gated calcium channels in the sarcolemma causing contraction

Front 267

peristalsis

Back 267

waves of contraction brought about by food distending the esophagus or feces distending the colon
propels contents along the organ

Front 268

Stress-relaxation response

Back 268

(receptive relaxation) -helps hollow organs gradually fill (urinary bladder)
when stretched, tissue briefly contracts then relaxes – helps prevent emptying while filling

Front 269

Skeletal muscle cannot contract forcefully if ________________

Back 269

Skeletal muscle cannot contract forcefully if overstretched

Front 270

Smooth muscle contracts forcefully ____________________________ this
allows hollow organs such as the stomach and bladder to fill and then expel their contents efficiently

Back 270

Smooth muscle contracts forcefully even when greatly stretched
allows hollow organs such as the stomach and bladder to fill and then expel their contents efficiently

Front 271

Smooth muscle can be anywhere from _________ to __________ its resting length and still contract powerfully

Back 271

Smooth muscle can be anywhere from half to twice its resting length and still contract powerfully

Front 272

Smooth muscle can be anywhere from half to twice its resting length and still contract powerfully

3 reasons:
there are no _____ _______, so thick filaments cannot butt against them and stop contraction
since the thick and thin filaments are not arranged in orderly sarcomeres, stretching does not cause a situation where there is too little overlap for cross-bridges to form
the thick filaments of smooth muscle have myosin heads along their entire length, so cross-bridges can form anywhere

Back 272

Smooth muscle contracts forcefully even when greatly stretched
allows hollow organs such as the stomach and bladder to fill and then expel their contents efficiently

Smooth muscle can be anywhere from half to twice its resting length and still contract powerfully

3 reasons:
there are no z discs, so thick filaments cannot butt against them and stop contraction
since the thick and thin filaments are not arranged in orderly sarcomeres, stretching does not cause a situation where there is too little overlap for cross-bridges to form
the thick filaments of smooth muscle have myosin heads along their entire length, so cross-bridges can form anywhere

Front 273

plasticity

Back 273

the ability to adjust its tension to the degree of stretch
a hollow organ such as the bladder can be greatly stretched yet not become flabby when it is empty

Front 274

Myasthenia GravisAutoimmune disease in which antibodies attack neuromuscular junctions and bind ACh receptors together in clusters
disease mainly of women between 20 and 40
muscle fibers then remove the clusters of receptors from the sarcolemma by endocytosis
fiber becomes less and less sensitive to ACh
effects usually first appear in facial muscles
drooping eyelids and double vision, difficulty swallowing, and weakness of the limbs

Back 274

Myasthenia Gravis

Front 275

Strabismus

Back 275

inability to fixate on the same point with both eyes

Front 276

Which of the following would NOT occur as a result of living in near zer-gravty conditions?
Bone loss
Cardiac muscle atrophy
Joint luxation
Skeletal muscle atrophy

Back 276

Joint luxation (dislocation)

- zero gravity does not take much effort for your muscles to do work, they don’t have stress on them, they instead are not being stressed and bone loss results from inactivity, the heart does not work as hard either and the heart muscle weakens

Front 277

Treatments for myasthenia gravis

Back 277

cholinesterase inhibitors retard breakdown of ACh allowing it to stimulate the muscle longer
Immunosuppressive agents suppress the production of antibodies that destroy ACh receptors
thymus removal (tymectomy) – helps to dampen the overactive immune response that causes myasthenia gravis
plasmapheresis –technique to remove harmful antibodies from blood plasma

Front 278

cholinesterase inhibitors

Back 278

retard breakdown of ACh allowing it to stimulate the muscle longer

Front 279

Immunosuppressive agents

Back 279

suppress the production of antibodies that destroy ACh receptors

Front 280

thymus removal (tymectomy)

Back 280

helps to dampen the overactive immune response that causes myasthenia gravis

Front 281

plasmapheresis

Back 281

technique to remove harmful antibodies from blood plasma

Front 282

You would expect a body-builder to have more _______ muscle fibers than a marathon runner. Slow oxidative fibersFast glycolytic fibers

Back 282

Fast- glycolytic fibers