Muscles

Question 1

What are the three types of muscle tissue?

Answer 1

• Skeletal
• Cardiac
• Smooth

Question 2

Define:

Excitability

Answer 2

Plasma membranes can change electrical states and send action potential along membrane length

Question 3

What are the three properties of muscle tissue?

Answer 3

• Elasticity
• Extensibility
• Contractility

Question 4

Define:

Elasticity

Answer 4

Allows muscle to return to original length when relaxed due to elastic fibers

Question 5

Define:

Extensibility

Answer 5

Muscle tissue can stretch or extend

Question 6

Define:

Contractility

Answer 6

Allows muscle tissue to pull on its attachment points and shorten with force

Question 7

Define:

Epimysium

Answer 7

Outer sheath of dense, irregular connective tissue covering muscle

Question 8

Define:

Fascicle

Answer 8

Bundles of muscle fibers

Question 9

Define:

Sarcomere

Answer 9

Functional unit of skeletal muscle

Question 10

What are the two key proteins that make up contractile machinery?

Answer 10

Actin and myosin

Question 11

What happens to sarcomere structure when muscle contracts?

Answer 11

• A band stays the same.
• I band becomes smaller.
• Z-discs come closer together.

Question 12

Define:

Myosin

Answer 12

• Thick filament
• Composed of globular head and long tail

Question 13

Define:

Actin

Answer 13

• Thin filament
• Double helix, “string of pearls”

Question 14

Define:

Troponin

Answer 14

Globular molecule attached at regular intervals to tropomyosin

Question 15

Define:

Tropomyosin

Answer 15

Long polypeptide chain that lies in grooves between actin helices

Question 16

What is the force generated by actin-myosin interaction proportional to?

Answer 16

The number of myosin heads that can interact with thin filament

Question 17

What is the excitation portion of “excitation-contraction coupling”?

Answer 17

Propagation of action potential along sarcolemma

Question 18

Where does the action potential travel from the sarcolemma to reach the sarcoplasmic reticulum?

Answer 18

The transverse-tubules (T-tubules)

Question 19

What ion initiates muscle fiber contraction?

Answer 19

Calcium

Question 20

What are the steps involved in cross-bridge cycling?

Answer 20

1. ATP binds with myosin head, forming ADP and Pi with calcium binding to troponin.
2. Myosin binds with exposed actin binding site, generating force.
3. ADP and Pi released from myosin head.
4. Another ATP binds to myosin.

Question 21

How does muscle relaxation occur?

Answer 21

• Signaling from motor neuron ends and sarcolemma repolarizes
• Muscle runs out of ATP and becomes fatigued

Question 22

Define:

Sliding filament theory of muscle contraction

Answer 22

Shortening of sarcomere results from relative movement of actin and myosin filaments past each other while each filament retains original length

Question 23

Define:

Creatine phosphate

Answer 23

Created when resting muscle transfers energy from excess ATP to creatine to produce ADP and creatine phosphate

Question 24

What are the three types of muscle contraction?

Answer 24

• Isotonic
• Isometric
• Isokinetic

Question 25

# Define: Isotonic contraction

Answer 25

Tension in muscle stays constant and load is moved while length of muscle changes

Question 26

# Define: Concentric contraction

Answer 26

Muscle shortens to move load

Question 27

# Define: Eccentric contraction

Answer 27

Muscle lengthens while resisting load

Question 28

# Define: Isometric contraction

Answer 28

Muscle produces tension without changing length and not moving load

Question 29

# Define: Isokinetic contraction

Answer 29

Muscle contraction and resulting change in joint angle at constant speed

Question 30

How is the number of muscle fibers in a motor unit determined?

Answer 30

By degree of control required by muscle ## Footnote Fine movement muscles have fewer muscle fibers per unit while coarse movement muscles have many muscle fibers per unit.

Question 31

# Define: Myogram

Answer 31

Measures muscle activation and contraction

Question 32

What are the three phases of a twitch?

Answer 32

1. Latent period 2. Contraction period 3. Relaxation phase

Question 33

# Define: Latent period

Answer 33

When action potential is propagated along sarcolemma and calcium ions released from sarcoplasmic reticulum

Question 34

# Define: Contraction phase

Answer 34

* Calcium ions bind to troponin * Tropomyosin moves away from actin bindinng sites, causing cross-bridges to form

Question 35

# Define: Relaxation phase

Answer 35

Tension decreases as contraction stops with calcium ions pumped out of sarcoplasm into sarcoplasmic reticulum

Question 36

# Define: Muscle tone

Answer 36

Small amount of contraction in skeletal muscles

Question 37

# Define: Hypotonia

Answer 37

Absence of low-level contractions that cause muscle tone

Question 38

# Define: Hypertonia

Answer 38

Excessive muscle tone and excessive reflex responses (hyperreflexia)

Question 39

# Define: Slow oxidative, type I muscle fiber

Answer 39

* Contract relatively slowly and use aerobic respiration to produce ATP

Question 40

# Define: Fast oxidative, type IIa muscle fiber

Answer 40

Have fast contractions and primarly use aerobic respiration but can also use anaerobic respiration

Question 41

# Define: Fast glycolytic, type IIb muscle fiber

Answer 41

Have relatively fast contractions and use glycolysis to produce ATP

Question 42

# Define: Gap junction

Answer 42

Forms channels between adjacent fibers allowing depolarizing current from cations to flow from one muscle cell to next

Question 43

What is the function of electric coupling

Answer 43

Quick transmission of action potentials and coordinate heart contractions

Question 44

# Define: Syncytium

Answer 44

Functional unit of contraction created by network of electrically connected cardiac muscle cells

Question 45

# Define: Desmosomes

Answer 45

Cell structure anchoring ends of cardiac muscle fibers together

Question 46

What is the function of pacemaker cells?

Answer 46

Control heart contractions in response to signals from autonomic nervous system to speed up/slow down heart rate

Question 47

# Define: Autorhythmicity

Answer 47

The ability to depolarize and fire action potentials independently

Question 48

Where is smooth muscle most commonly found?

Answer 48

* Walls of hollow organs * Bloood vessels * Respiratory/urinary system * Eyes * Skin

Question 49

What is the equivalent of Z-discs found in smooth muscle?

Answer 49

Dense bodies

Question 50

# Define: Calveoli

Answer 50

Membrane indentations that supply calcium ions via the sarcoplasmic reticulum

Question 51

What is cross-bridge formation regulated by in smooth muscle cells?

Answer 51

Calmodulin

Question 52

What is the stress-relaxation response in visceral smooth muscle?

Answer 52

Mechanical stress from stretching muscle triggers contraction followed by relaxation.

Question 53

What is the function of somites?

Answer 53

Give rise to myoblasts

Question 54

# Define: Myoblast

Answer 54

Muscle stem cell

Question 55

# Define: Fibrosis

Answer 55

Scar tissue

Question 56

What is the function of satellite cells?

Answer 56

Help repair skeletal muscle cells

Question 57

How is smooth muscle regenerated?

Answer 57

From pericytes