skeletal text

Question 1

What is the best-known feature of skeletal muscle?

Answer 1

Its ability to contract and cause movement

Question 2

What role do skeletal muscles play in maintaining posture?

Answer 2

They resist gravity to maintain posture

Question 3

What do small, constant adjustments of skeletal muscles help with?

Answer 3

Holding a body upright or balanced in any position

Question 4

How do muscles contribute to skeletal stability?

Answer 4

They prevent excess movement of the bones and joints

Question 5

What can happen to joints if muscles do not stabilize them?

Answer 5

Joints can become misaligned or dislocated

Question 6

Where are skeletal muscles located in relation to internal tracts?

Answer 6

At the openings of internal tracts to control movement of various substances

Question 7

What functions do skeletal muscles allow to be under voluntary control?

Answer 7

• Swallowing
• Urination
• Defecation

Question 8

How do skeletal muscles protect internal organs?

Answer 8

By acting as an external barrier to trauma and supporting organ weight

Question 9

How do skeletal muscles contribute to homeostasis?

Answer 9

By generating heat through muscle contraction

Question 10

What is produced when ATP is broken down during muscle contraction?

Answer 10

Heat

Question 11

What noticeable effect occurs during exercise due to muscle contraction?

Answer 11

Body temperature rises

Question 12

What types of integrated tissues are included in skeletal muscles?

Answer 12

• Skeletal muscle fibers
• Blood vessels
• Nerve fibers
• Connective tissue

Question 13

What are the three layers of connective tissue that enclose skeletal muscles called?

Answer 13

Mysia

Question 14

What is the name of the sheath of dense, irregular connective tissue that wraps each muscle?

Answer 14

Epimysium

Question 15

What is the function of the epimysium?

Answer 15

Allows muscle to contract and move powerfully while maintaining structural integrity

Question 16

What does the epimysium separate muscle from?

Answer 16

Other tissues and organs in the area

Question 17

Fill in the blank: The epimysium allows the muscle to move _______.

Answer 17

[independently]

Question 18

What is a fascicle in skeletal muscle?

Answer 18

An individual bundle of muscle fibers organized by perimysium

Fascicular organization allows for specific muscle movement by activating subsets of fibers.

Question 19

What connective tissue layer encases each muscle fiber?

Answer 19

Endomysium

The endomysium contains extracellular fluid and nutrients for muscle fibers.

Question 20

What does the perimysium do?

Answer 20

Organizes muscle fibers into fascicles

It is a middle layer of connective tissue in skeletal muscle.

Question 21

How does the tension created by muscle contraction affect bone movement?

Answer 21

It transfers through mysia to tendon and then to periosteum

This process pulls on the bone for skeletal movement.

Question 22

What is the role of blood vessels in skeletal muscle?

Answer 22

Nourishment, oxygen delivery, and waste removal

Every skeletal muscle is richly supplied by blood vessels.

Question 23

What is an aponeurosis?

Answer 23

A broad, tendon-like sheet of connective tissue

It can fuse with mysia or fascia, like in the lower back with the latissimus dorsi.

Question 24

What connects skeletal muscle fibers to the nervous system?

Answer 24

Axon branch of a somatic motor neuron

This signaling is essential for muscle contraction in skeletal muscle.

Question 25

True or False: Skeletal muscle can contract without nervous system signaling.

Answer 25

False ## Footnote Unlike cardiac and smooth muscle, skeletal muscle requires nerve signals to contract.

Question 26

What intertwines with the collagen of a tendon in skeletal muscle?

Answer 26

Collagen in the three tissue layers called mysia ## Footnote This connection aids in the transfer of tension during muscle contraction.

Question 27

Fill in the blank: The connective tissue between skin and bones is called _______.

Answer 27

Fascia ## Footnote Fascia plays a role in the structural organization of muscles.

Question 28

What are skeletal muscle cells commonly referred to as?

Answer 28

Muscle fibers

Question 29

What is the diameter range of skeletal muscle fibers in human cells?

Answer 29

Up to 100 μm

Question 30

What is the maximum length of skeletal muscle fibers, specifically in the Sartorius of the upper leg?

Answer 30

Up to 30 cm (11.8 in)

Question 31

What process forms multinucleated skeletal muscle fibers?

Answer 31

Fusion of embryonic myoblasts

Question 32

What does having multiple nuclei in skeletal muscle fibers allow for?

Answer 32

Production of large amounts of proteins and enzymes

Question 33

What does the Greek term 'sarco' mean?

Answer 33

Flesh

Question 34

What is the plasma membrane of muscle fibers called?

Answer 34

Sarcolemma

Question 35

What is the cytoplasm of muscle fibers referred to as?

Answer 35

Sarcoplasm

Question 36

What is the specialized smooth endoplasmic reticulum in muscle fibers called?

Answer 36

Sarcoplasmic reticulum (SR)

Question 37

What is the functional unit of a skeletal muscle fiber?

Answer 37

Sarcomere

Question 38

What are the two contractile myofilaments found in a sarcomere?

Answer 38

Actin (thin filament) and myosin (thick filament)

Question 39

Fill in the blank: The sarcoplasmic reticulum stores, releases, and retrieves _______.

Answer 39

Calcium ions (Ca++)

Question 40

True or False: Skeletal muscle fibers have a single nucleus.

Answer 40

False

Question 42

What gives skeletal muscle fibers their striated appearance?

Answer 42

The arrangement of myofilaments of actin and myosin in sequential order

Question 43

What is a sarcomere?

Answer 43

A packet of microfilaments and their regulatory proteins, including troponin and tropomyosin

Question 44

What is the functional unit of the muscle fiber?

Answer 44

The sarcomere

Question 45

What structures border the sarcomere?

Answer 45

Z-discs (or Z-lines)

Question 46

How thick are myofibrils?

Answer 46

Approximately 1.2 μm in diameter

Question 47

What is the length of each sarcomere?

Answer 47

Approximately 2 μm

Question 48

What type of arrangement do sarcomeres have?

Answer 48

Three-dimensional cylinder-like arrangement

Question 49

What are the two types of filaments in a sarcomere?

Answer 49

* Thin filament (actin) * Thick filament (myosin)

Question 50

What anchors the actin myofilaments in a sarcomere?

Answer 50

Z-discs

Question 51

What is the role of myofibrils in muscle contraction?

Answer 51

As myofibrils contract, the entire muscle cell contracts

Question 52

What is the mass difference between actin and myosin filaments?

Answer 52

Actin is thinner and has less mass, while myosin is thicker and has more mass

Question 53

Fill in the blank: The thin filament of the sarcomere is made of _______.

Answer 53

actin

Question 54

Fill in the blank: The thick filament of the sarcomere is made of _______.

Answer 54

myosin

Question 55

True or False: Each muscle fiber contains only one sarcomere.

Answer 55

False

Question 56

How many sarcomeres can be found inside one muscle fiber?

Answer 56

Hundreds to thousands

Question 57

What proteins are involved in the regulation of muscle contraction at the sarcomere?

Answer 57

* Troponin * Tropomyosin

Question 58

What is the neuromuscular junction (NMJ)?

Answer 58

The site where a motor neuron’s terminal meets the muscle fiber, initiating muscle fiber response to signaling ## Footnote The NMJ is crucial for the functional activation of skeletal muscle fibers to contract.

Question 59

What is the role of excitation signals from the neuron?

Answer 59

They are the only way to functionally activate the muscle fiber to contract ## Footnote This activation is essential for muscle movement.

Question 60

Define membrane potential.

Answer 60

An electrical gradient across cell membranes, typically around -60 to -90 mV inside relative to outside ## Footnote Membrane potential is critical for generating electrical signals in neurons and muscle cells.

Question 61

How do neurons and muscle cells generate electrical signals?

Answer 61

By controlling the movement of ions across their membranes via ion channels ## Footnote The movement of these ions creates small electrical currents necessary for signaling.

Question 62

What is an action potential?

Answer 62

A special type of electrical signal that can travel along a cell membrane as a wave ## Footnote Action potentials allow for rapid and faithful signal transmission over long distances.

Question 63

What is meant by excitation-contraction coupling?

Answer 63

The process where a muscle fiber must first be excited to fire an action potential, leading to contraction ## Footnote This involves the release of calcium ions (Ca++) from the sarcoplasmic reticulum.

Question 64

What triggers the excitation step in skeletal muscles?

Answer 64

Signals from the somatic motor division of the nervous system ## Footnote This signaling is essential for muscle contraction.

Question 65

What happens after the muscle fiber action potential is generated?

Answer 65

Calcium ions (Ca++) are released from the sarcoplasmic reticulum, allowing myosin to pull actin filaments ## Footnote This interaction leads to muscle fiber shortening and contraction.

Question 66

Fill in the blank: The inside of a cell membrane typically has a membrane potential of around _______.

Answer 66

-60 to -90 mV

Question 67

True or False: Every skeletal muscle fiber is innervated by multiple motor neurons at the NMJ.

Answer 67

False ## Footnote Each skeletal muscle fiber is innervated by a single motor neuron.

Question 68

Where do motor neurons originate that tell skeletal muscle fibers to contract?

Answer 68

The spinal cord and brainstem

Question 69

What are the long processes of motor neurons called?

Answer 69

Axons

Question 70

What do the axons of multiple neurons bundle together to form?

Answer 70

Nerves

Question 71

What initiates signaling in motor neurons?

Answer 71

Neuronal action potential

Question 72

What chemical messenger is released at the neuromuscular junction (NMJ)?

Answer 72

Acetylcholine (ACh)

Question 73

What is the space called that ACh diffuses across at the NMJ?

Answer 73

Synaptic cleft

Question 74

Where are ACh receptors located?

Answer 74

Motor end-plate of the sarcolemma

Question 75

What happens when ACh binds to its receptor?

Answer 75

A channel opens for positively charged ions to enter the muscle fiber

Question 76

What does depolarization of the muscle fiber mean?

Answer 76

The membrane potential becomes less negative

Question 77

What triggers the opening of voltage-gated sodium channels?

Answer 77

Depolarization of the membrane

Question 78

What spreads along the entire membrane to initiate excitation-contraction coupling?

Answer 78

Action potential

Question 79

What happens immediately after depolarization of the membrane?

Answer 79

Repolarization occurs

Question 80

Which enzyme degrades ACh in the synaptic cleft?

Answer 80

Acetylcholinesterase (AChE)

Question 81

What is the consequence of ACh degradation by AChE?

Answer 81

Prevents unwanted extended muscle excitation and contraction

Question 82

What is the excitation portion of excitation-contraction coupling?

Answer 82

Propagation of an action potential along the sarcolemma

Question 83

What triggers the release of calcium ions (Ca++) from the sarcoplasmic reticulum (SR)?

Answer 83

Excitation of the muscle fiber

Question 84

What are the invaginations in the sarcolemma called?

Answer 84

T-tubules

Question 85

What does the 'T' in T-tubules stand for?

Answer 85

Transverse

Question 86

What is the arrangement of a T-tubule with the membranes of SR called?

Answer 86

Triad

Question 87

What cylindrical structure does the triad surround?

Answer 87

Myofibril

Question 88

What two proteins are contained within myofibrils?

Answer 88

Actin and myosin

Question 89

What do T-tubules carry into the interior of the cell?

Answer 89

Action potential ## Footnote T-tubules are essential for transmitting the electrical signal that leads to muscle contraction.

Question 90

What triggers the opening of calcium channels in the membrane of the adjacent SR?

Answer 90

Arrival of action potential ## Footnote The action potential allows calcium ions to flow from the SR into the sarcoplasm, which is crucial for muscle contraction.

Question 91

What is the role of Ca++ in muscle contraction?

Answer 91

Initiates contraction of the muscle fiber ## Footnote Ca++ binds to proteins in the sarcomeres, enabling the contraction process.

Question 92

Where does Ca++ diffuse to after being released from the SR?

Answer 92

Into the sarcoplasm ## Footnote The diffusion of Ca++ into the sarcoplasm is a key step in the muscle contraction mechanism.

Question 93

What are the contractile units of muscle fibers called?

Answer 93

Sarcomeres ## Footnote Sarcomeres are the structural and functional units of muscle fibers that facilitate contraction.