Anatomy Chapter 9

Front 1

Approx number of skeletal muscles

Back 1

greater than 700

Front 2

skeletal Muscle cell is also called

Back 2

muscle fiber

Front 3

Epimysium

Back 3

-dense irregular connective tissue layer
-surrounds entire skeletal muscle
-separates muscle form surrounding tissues and organs
-very strong

Front 4

Perimysium

Back 4

-surrounds fascicles
-thinner connective tissue
-lots of blood vessels and nerves

Front 5

Endomysium

Back 5

-surrounds each muscle fiber
-binds fibers to each other
-delicate network of reticular fibers

myosatellite cells lie between endomysium and muscle fibers

Front 6

Functions of skeletal muscles

Back 6

-produce skeletal movement
-maintain posture and body position
-support soft tissue
-guard entrances and exits
-maintain body temperature

Front 7

How are tendons formed?

Back 7

connective tissue extends past muscle cell

Front 8

All muscles have what kinds of connective tissue?

Back 8

-epimysium
-perimysium
-endomysium

Front 9

Neuromuscular synapse

Back 9

-chemical communication between a synaptic terminal of the neuron and skeletal muscle cell
-only 1 in a muscle fiber
-located in middle of cell

Front 10

Aponeuroses

Back 10

broad and flat tendon

Front 11

Sarcolemma

Back 11

plasma membrane of muscle cell

Front 12

Sarcoplasm

Back 12

cytoplasm of muscle cell

Front 13

Muscle fibers

Back 13

-multinucleated, very large
-myoblasts
-myofibrils
-satellite cells

Front 14

Myoblasts

Back 14

-stem cell
-undifferentiated
-fuse together to form muscle fiber

Front 15

Myofibrils

Back 15

-responsible for contraction
-fill muscle fiber
-shorten entire cell

Front 16

Satellite cells

Back 16

-replace damaged muscle tissue

Front 17

Sarcoplasmic reticulum

Back 17

-responsible for storehouse for calcium
-closely associated with T-tubules
-controls contractions of individual myofibrils

Front 18

Transverse tubules

Back 18

-made up of sarcolemma
-carry signal to inside of cell for contraction

Front 19

Myofilaments

Back 19

proteins in myofibrils
-thin filaments
-thick filaments

Front 20

Thin filaments

Back 20

actin
troponin
tropomyosin
titin
ect

Front 21

Thick filaments

Back 21

myosin

Front 22

What gives sarcomere a banded appearance?

Back 22

arrangement of thick and thin filaments within sarcomere give it banded appearance

Front 23

Sarcomere

Back 23

smallest functional unit of muscle fiber

Front 24

M-line

Back 24

anchors thick filaments

Front 25

Z-line

Back 25

-anchors thin filaments to each other
-delineate the ends of sarcomere

Front 26

A-band

Back 26

-area of sarcomere containing thick filaments
-includes M-line, H-band, zone of overlap (thick and thin filaments)

Front 27

H-band

Back 27

thick bands only

Front 28

I-band

Back 28

-region between the A band and Z line
-contains only thin filaments

Front 29

Motor end plate

Back 29

-area on muscle surface in exact center of length of muscle fiber
-invaginated
-has receptors coupled to ion channels

Front 30

Synaptic knob

Back 30

end of motor neuron

Front 31

Synaptic clefts

Back 31

separates the synaptic knob from the motor end plate of skeletal muscle fiber

Front 32

Synaptic vesicles

Back 32

where neurotransmitters are stored
-on end of motor neuron

Front 33

Acetylcholine

Back 33

neurotransmitter released in skeletal muscles by motor neuron
-communication takes the form of a change in the transmembrane potential of that cell

Front 34

Motor unit

Back 34

all of the muscle fibers controlled by a single motor neuron

Front 35

Recruitment

Back 35

the smooth but steady increase in muscular tension produced by increasing the number of active motor units

Front 36

Muscle tone

Back 36

resting tension in a skeletal muscle
-helps stabilize the position of bones and joints
-even when muscle is at rest, some motor units are always active

Front 37

Muscle hypertrophy

Back 37

enlargement of stimulated muscle
-more mitochondria, greater glycolytic enzymes, larger glycogen reserves
-occurs in muscles stimulated to near max tension

Front 38

Muscle atrophy

Back 38

-reduction in muscle size, tone, and power
-occurs when muscle not stimulated by motor neuron regularly
-muscle becomes flaccid and muscle fibers become smaller and weaker
-initially reversible, but dying muscle fibers are not replaced, and in extreme atrophy the functional losses are permanent

Front 39

What are the differences between skeletal muscle fiber types?

Back 39

Differences reflect differences in ways they obtain ATP to support their contractions

Front 40

Fast oxidative fibers

Back 40

-contract faster than slow fibers but slower than fast glycolytic fibers
-most mitochondria than fast glycolytic
-increased capillary support than fast glycolytic
-greater resistance to fatigue than fast glycolytic

Front 41

Slow oxidative fibers

Back 41

-half diameter of fast glycolytic fibers
-take 3 times as long to contract as fast glycolytic
-specialized to continue contracting for extended periods
-contain myoglobin
-aerobic metabolism to get ATP
-more extensive capillaries

Front 42

Fast glycolytic fibers

Back 42

-large in diameter
-densely packed myofibrils
-large glycogen reserves
-relatively few mitochondria
-most of skeletal muscle fibers
-anaerobic glycolysis to get ATP

Front 43

Distribution of skeletal muscle fibers

Back 43

-most muscles are mixed fiber types
-no slow fibers in eyes or hands
-many back and calf muscles are slow fibers to help maintain posture
-geneticall determined

Front 44

Parallel muscles

Back 44

-most muscles in body
-has central body (belly)
-greatest range of motion
-fascicles are parallel to the long axis of the muscle

Front 45

Conergent muscles

Back 45

-fan-shaped
-most versatile
-do not pull as hard of the tendon when all muscle units contract as compared to parallel muscles because the muscle fibers on opposite sides pull in different directions rather than all pulling in the same direction

Front 46

Example of parallel muscle

Back 46

biceps brachii

Front 47

Example of convergent muscle

Back 47

pectoralis muscles

Front 48

example of unipennate muscle

Back 48

extenson digitorum muscle

Front 49

Example of bipennate muscle

Back 49

rectus femoris muscle

Front 50

Example of multipennate muscle

Back 50

deltoid muscle

Front 51

Pennate muscles

Back 51

-1 or more tendons run through the body of the muscle
-generate greater tension that other muscle types
-subtypes: unipennate, bipennate, multipennate

Front 52

Circular muscles

Back 52

sphincter muscles
-concentrically arranged around an opening
-guard entrances and exits

Front 53

First class lever

Back 53

-like a see-saw
-fulcrum lies between the applied force and the resistance
-can change the amount of force transmitted to the resistance and alter the direction and speed of movement
-ex. muscles that extend the neck

Front 54

Second class lever

Back 54

-resistance is located between the applied force and the fulcrum
-magnifies force at the expense of distance and speed
-direction of movement remains unchanged

ex. plantar flexion, calf muscles act across a second class lever

Front 55

Third class lever

Back 55

-force applied between the resistance and the fulcrum
-most common
-increases speed and distance moved but requires a larger applied force

Front 56

Levers provide..

Back 56

levers provide speed and versatility

Front 57

Origin

Back 57

remains stationary and is proximal

Front 58

Insertion

Back 58

moves and is distal

Front 59

Prime mover

Back 59

agonist
-muscle whose contraction is responsible for producing a particular movement

Front 60

Synergist

Back 60

assists the prime mover in performing that action
-may provide additional pull near the insertion or stabilize the point of origin

Front 61

Antagonist

Back 61

muscle whose actions oppose that of the agonist

Front 62

Rectus

Back 62

straight
-parallel muscles whose fibers run along long axis of body

Front 63

Transversus

Back 63

muscles whose fibers run across the body

Front 64

Oblique

Back 64

muscles whose fibers run at an oblique angle to the long axis of the body

Front 65

Longus

Back 65

long muscles

Front 66

Teres

Back 66

long and round muscles

Front 67

Brevis

Back 67

short muscles

Front 68

Maximus

Back 68

biggest muscle

Front 69

Minor

Back 69

smaller muscle

Front 70

What is the perimysium? What structures would be located here?

Back 70

The perimysium is the connective tissue partition that separates adjacent fasiculi in a skeletal muscle. The perimysium contains blood vessels and nerves that supply each individual fasicle

Front 71

Describe the difference between a tendon and an aponeurosis?

Back 71

Tendons are collagenous bands that connect skeletal muscle to the skeleton. Aponeuroses are thick, flattened tendinous sheets

Front 72

What is the difference between a myoneural junction and a motor end plate?

Back 72

A myoneural junction is the site where the axon meets the muscle sarcolemma. A motor end plate is the region of teh sarcolemma at the neuromusclar synapse

Front 73

Why does skeletal muscle appear striated when viewed with a microscope?

Back 73

Skeletal muscle appears striated when viewed under the microscope because it is composed of the myofilaments actin and myosin, whihc are arranged in such a way as to produce a banded appearance in the muscle

Front 74

What are myofibrils? Where are they found?

Back 74

A myofibril is a cylindrical collection of myofilaments within a cardiac or skeletal muscle cell

Front 75

Myofilaments consist primarily of what proteins?

Back 75

Myofilaments consist primarily of actin and myosin, along with accessory proteins of the thin filament (tropomyosin and troponin)

Front 76

What is the function unit of skeletal muscle?

Back 76

The functional unit of skeletal muscle is the sarcomere

Front 77

What two proteins help regulate actin and myosin interaction?

Back 77

The proteins tropomyosin and troponin help regulate the actin and myosin interactions

Front 78

What happens to the A bands and I bands of a myofibril during a contraction?

Back 78

During contraction, the width of the A band remains the same and the I band gets smaller

Front 79

List the sequence of events during a contraction

Back 79

Stimulation of a motor neuron triggers the release of chemicals at the neuromuscular synapse, which alters the transmembrane potential at the sarcolemma. This change sweeps across the surface of the sarcolemma and into the T-tubules. The change in the transmembrane potential of the T-tubules triggers the release of calcium ions by teh sarcoplasmic reticulum. This release initiates the contraction, which proceeds as myosin heads go through repeated cycles of attach-pivot-detatch-return

Front 80

How do terminal cisternae and transverse tubules interact to cause a skeletal muscle contraction?

Back 80

Terminal cisternae are expanded chambers of the sarcoplasmic reticulum-they store calcium ions, which are required to initiate contractile activities within skeletal muscle cells. Transverse tubules are sandwiched between terminal cisternae. A transverse tubule is an invagination of the sarcolemma, which conducts the stimulation into the interior of the cell. On arrival, it causes the release of calcium ions from the terminal cisternae, and this results in muscle contraction

Front 81

Why does a sprinter experince muscle fatigue after a few minutes, while a marathon runner can run for hours?

Back 81

The sprinter requires large amounts of energy for a relatively short burst of activity. To supply this demand for energy, the muscles switch to anaerobic metabolism. Anaerobic metabolism is not as efficient in producing energy as is aerobic metabolism, and the process also produces acidic waste products. The combination of less energy and the waste products contributes to fatigue. Marathon runners, on the other hand, derive most of their energy from aerobic metabolism, which is more efficient and does not produce the level of waste products that anaerobic metabolism does.

Front 82

What type of muscle fibers would you expect to predominate in the large leg muscles of someone who excels at endurance activities such as cycling or long distance running?

Back 82

Individuals who are naturally better at endurance types of activies have a higher percentage of slow-twitch muscle fibers, which are physiologically better adapted to this type of activity than the fast twitch fibers, which are less vascular and fatigue faster

Front 83

Why do some motor units control only a few muscle fibers, whereas other control many fibers?

Back 83

It depends on the number of branches in the moton neurons. A lesser number of branches results in teh activation in only a few motor neurons

Front 84

What is recruitment?

Back 84

Recruitment is the smooth but steady increase in musclar tension produced by increasing the number of active motor units

Front 85

What does the name flexor digitorum longus tell you about this muscle?

Back 85

This is a long muscle that flexes the joints of the finger

Front 86

Describe the difference between the origin and insertion of a muscle

Back 86

Each muscle begins at an origin which typically remains stationary, and ends at an insertion, which is the part of the muscle that moves during a contraction

Front 87

What type of muscle is a synergist?

Back 87

A synergist contracts to assist the prime mover in performing a specific action

Front 88

What is the difference between major and minor designations for a muscle?

Back 88

Major is used to describe muscles that are bigger, whereas minor is used to describe muscles that are smaller

Front 89

When do active sites on the actin become available for binding

Back 89

calcium binds to troponin

Front 90

The function of a neuromuscular synapse is to..

Back 90

to facilitate chemical communication between a neuron and a muscle fiber

Front 91

The direct energy supply produced by the skeletal muscles in order to enable them to contract is..

Back 91

ATP

Front 92

In a pennate muscle, the fibers are...

Back 92

oblique to the tendon

Front 93

Interactions between actin and myosin filaments of the sarcomere are responsible for..

Back 93

muscle contraction

Front 94

The bundle of collagen fibers at the end of a skeletal muscle that attaches the muscle to bone is called..

Back 94

a tendon

Front 95

All of the muscle fibers controlled by a single moton neuron constitute a ...

Back 95

motor unit

Front 96

To lessen the rate at which muscles fatigue during a contraction, motor units are activated..

Back 96

on a rotating basis

Front 97

Where would the ratio of motor neurons to muscle fibers be the greatest?

Back 97

the eye

Front 98

If a person is cold, a good way to warm up is to exercise. What is the mechanism of this warming?

Back 98

Muscle contraction uses ATP and the utilization of this energy generates heat, which helps warm the body

Front 99

Summarize the basic sequence of events that occurs at a neuromuscular synapse

Back 99

A nerve impulse arrives at the terminal bouton of the neuromuscular synapse and causes ACh to be released into the synaptic cleft. The ACh released then binds to receptors on teh sarcolemma surface, initiating a change in the local transmembrane potential. This change results in the generation of electrical signals that sweep over the surface of the sarcolemma.

Front 100

What is the role of connective tissue in the organization of skeletal muscle?

Back 100

Connective tissues bind and attach skeletal muscles to other structures. There are 3 concentric layers of connective tissue. The outer layer, epimysium, surrounds the entire muscle. The middle layer, perimysium, divides the muscle into a series of internal compartments, each containing a bundle of muscle fibers. Each compartment is called a fascicle. The inner nayer, endomysium, surrounds each skeletal muscle fiber and binds each fiber to its neighbors.

Front 101

A motor unit from a skeletal muscle contains 1500 muscle fibers. WOuld this muscle be involved in fine delicate movements or powerful gross movements? Explain

Back 101

A motor unit with 1500 fibers would be involved in powerful gross movement. The greater the number of fibers in a motor unit, the more powerful the contraction, and the less fine control exhibited by the motor unit.

Front 102

What is the role of the zone of overlape in the production of tension in a skeletal muscle?

Back 102

In the zone of overlap, the thin filaments pass between the thick filaments. It is in this region that interaction between thick and thin filaments occurs to form cross-bridges so that contraction may occur and tension may be generated.