Muscle Physiology (REYNOLDS) Flashcards by Gavin Kallabat

What are the 6 functions of skeletal muscles?

Produce skeletal movement
Maintain body position
Support soft tissues
Guard openings
Maintain body temperature
Store nutrient reserves

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Muscles have three layers of connective tissue. What are they?

Epimysium, Perimysium and Endomysium

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All of the following are true regarding the Epimysium EXCEPT:

A. Exterior collagen layer

B. Surrounds muscle fiber bundles (fascicles)

C. Connected to deep fascia

D. Separates muscle from surrounding tissues

E. None of the above

B. Surrounds muscle fiber bundles (fascicles)

Perimysium surrounds muscle fiber bundles

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Which of the following is true regarding the Perimysium?

A. Surrounds individual muscle cells (muscle fibers)

B. Surrounds muscle fiber bundles (fascicles)

C. Connected to deep fascia

D. Separates muscle from surrounding tissues

E. None of the above

B. Surrounds muscle fiber bundles (fascicles)

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Which of the following is true regarding the Endomysium?

A. Surrounds individual muscle cells (muscle fibers)

B. Surrounds muscle fiber bundles (fascicles)

C. Connected to deep fascia

D. Separates muscle from surrounding tissues

E. None of the above

A. Surrounds individual muscle cells (muscle fibers)

Epimysium = exterior collagen layer

Perimysium = surrounds muscle fiber bundles

Endomysium = surrounds individual muscle cells

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Which of the following separates muscle from surrounding tissue?

A. Epimysium

B. Perimysium

C. Endomysium

A. Epimysium

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Which of the following contains capillaries and nerve fibers contacting muscle cells?

A. Epimysium

B. Perimysium

C. Endomysium

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Which of the following contains myosatellite cells (stem cells) that repair damage?

A. Epimysium

B. Perimysium

C. Endomysium

note: contains capillaries to help repair damage

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Which of the following contains the blood vessels and nerves to supply the fascicles?

A. Epimysium

B. Perimysium

C. Endomysium

B. Perimysium

Perimysium surrounds muscle fiber bundles (fascicles)

Endomysium surrounds muscle fibers

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Skeletal muscles fibers develop through fusion of mesodermal cells known as _____.

Myoblasts

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List the 4 thin filament proteins:

F-actin
Nebulin
Tropomyosin
Troponin

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All of the following are thin filament proteins EXCEPT:

A. Myosin

B. F-actin

C. Nebulin

D. Tropomyosin

E. Troponin

A. Myosin

Myosin and Titin = thick filament

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Which of the following contain both myosin and actin filaments?

A. Z line

B. M line

C. A bands

D. I bands

C. A bands

A band = actin + myosin

I band = actin ONLY

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Which of the following contain ONLY actin filaments?

A. Z line

B. M line

C. A bands

D. I bands

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Which of the following do thick filaments contain?

(select all that apply)

A. Myosin

B. Troponin

C. Titan

D. Tropomyosin

A. Myosin

C. Titan

Thick filaments = Titan + Myosin

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Which of the following holds F-actin strands together?

A. F-actin

B. Nebulin

C. Tropomyosin

D. Troponin

B. Nebulin

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Which of the following is a globular protein that binds tropomyosin to G-actin and is controlled by Ca²⁺?

A. Myosin

B. Nebulin

C. Troponin

D. Titan

C. Troponin

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Which of the following is double stranded and prevents actin-myosin interactions?

A. F-actin

B. Nebulin

C. Tropomyosin

D. Troponin

C. Tropomyosin

Which of the following is two twisted rows of globular G-actin?

A. F-actin

B. Nebulin

C. Tropomyosin

D. Troponin

A. F-actin

note: the active sites on G-actin strands bind myosin

F-actin: two twisted rows of globular G-actin

Nebulin: holds F-actin strands together

Tropomyosin: prevents actin-myosin interactions

Troponin: binds tropomyosin to G-actin

Discuss the sarcomere function:

Transverse tubules encircle the sarcomere near zones of overlap
Ca2+ released by SR causes thin and thick filaments to interact
Skeletal muscle contraction

Discuss the Sliding filament theory:

Thin filaments of sarcomere slide toward M line, alongside thick filaments
The width of A zone stays the same
Z lines move closer together
The process of contraction
Neural stimulation of sarcolemma causes excitation-contraction coupling
Cisternae of SR release Ca2+, which triggers interaction of thick and thin filaments consuming ATP and producing tension initiating contraction
Ca2+ binds to receptor on troponin molecule

Neural stimulation of the ________ causes excitation-contraction coupling.

Sarcolemma

Discuss the process of skeletal muscle contraction:

Neural stimulation of sarcolemma causes excitation-contraction coupling
Cisternae of SR release Ca²⁺ which triggers interaction of thick and thin filaments consuming ATP and producing tension
Initiating contraction:
- Ca²⁺ binds to receptor on troponin molecule
- Troponin-tropomyosin complex changes exposing the active site of F-actin
Myosin action:
- “energized” myosin heads bind to actin forming cross-bridges
- myosin undergoes a conformational change termed “ratchet action” that pulls actin towards center of sarcomere
- myosin releases ADP
- binding of ATP to myosin decreases affinity of myosin for actin thus releasing myosin from actin

Discuss the neuromuscular junction:

Where does it end at?
- What does the previous answer release?

Neuromuscular junction

ends at synaptic terminal
Synaptic terminal releases acetylcholine into the synaptic cleft (gap between synaptic terminal and motor end plate)

Discuss the neural transmitter Acetylcholine (ACh):

**_Acetylcholine_** * travels along synaptic cleft * binds to motor end plate of sarcolemma * causes Na+ rush into sarcoplasm * is quickly broken down by **acetylcholinesterase**

What are the 4 steps of acetylcholine in muscle contraction?

1. arrival of an action potential at the synaptic terminal 2. Release of ACh into synaptic cleft 3. Ach binding at motor end plate of synaptic cleft (causing Na+ to rush into the cell) 4. Appearance of an action potential in the sarcolemma (ACh is broken down by AChE at this step)

An action potential is generated by an increase of ______ in the sarolemma. A. Ca²⁺ B. ATP C. Acetylcholine D. Na⁺ E. K⁺

D. Na⁺

What are the 5 main steps of the contraction cycle?

1. Exposure of active sites * Ca²⁺ binds to receptor on troponin * Troponin-tropomyosin complex changes exposing active site of F-actin 2. Formation of cross-bridges * "energized" myosin head bind to underlying actin forming cross-bridges 3. Ratchet Action (pivoting) of myosin heads * myosin undergoes conformation change termed **"ratchet action"** that pulls actin toward the center of the sarcomere 4. Detachment of cross-bridges * myosin releases ADP * binding of ATP to myosin decreases the affinity of myosin for actin, thereby releasing myosin from actin 5. Reactivation of myosin * reactivation of myosin by partially hydrolyzing ATP

\_\_\_\_\_\_ is a fixed muscle contraction that occurs after death due to Ca²⁺ build up in sarcoplasm.

Rigor mortis

Discuss the Cori Cycle:

The removal and recycling of lactic acid by the liver, which recharges muscle glycogen

Which of the following contains **myoglobin**? A. Slow fibers B. Intermediate fibers C. Fast fibers D. All of the above

A. Slow fibers

Which of the following contain **intercalated discs**? A. Skeletal muscle B. Cardiac muscle C. Smooth muscle D. All of the following

B. Cardiac muscle Intercalated discs: * specialized contact points between cardiocytes that join cell membranes of adjacent cardiocytes (gap junctions, desmosomes) * Functions: * maintain structure * enhance molecular and electrical connections * conduct action potentials

What are the 4 functions of cadiac tissue?

1. Automacity * contraction w/o neural stimulation * controlled by pacemaker 2. Variable contraction tension * controlled by nervous system 3. Extended contraction time * 10 times as long as skeletal muscle 4. Prevention of wave stimulation * long refractory periods

Which of the following is **nonstriated**? A. Skeletal muscle B. Cardiac muscle C. Smooth muscle

C. Smooth muscle

What are the 8 charateristics of smooth muscle?

1. long, slender and spindle shaped 2. have single, central nucleus 3. have no T tubules, myofibrils or sarcomeres 4. Have no tendons or aponeuroses 5. have scattered myosin fibers 6. myosin fibers have more heads per thick filament 7. have thin filaments attached to dense bodies 8. dense bodies transmit contractions from cell to cell

Which of the following contain a multiple nuclei? A. Skeletal muscle B. Cardiac muscle C. Smooth muscle

A. Skeletal muscle Cardiac and smooth muscle contain one centralized nuclei

Which of the following contains calmodulin? A. Skeletal muscle B. Cardiac muscle C. Smooth muscle

C. Smooth muscle

\_\_\_\_\_ is a stair-step increase in twitch tension.

Treppe * repeated stimulations immediately after relaxation phase * causes a series of contractions with increasing tension

Which of the following is characterized as fast oxidative? A. Slow-twitch fibers B. Intermediate fibers C. Fast-twitch fibers

B. Intermediate fibers Slow-twitch fibers = slow oxidative Intermediate fibers = fast oxidative Fast-twitch fibers = fast glycolytic

Which of the following is characterized as fast glycolytic? A. Slow-twitch fibers B. Intermediate fibers C. Fast-twitch fibers

C. Fast-twitch fibers

Skeletal muscle develops tension but is prevented from changing length: A. Isotonic contraction B. Isometric contraction

B. Isometric contraction "Iso" = same "metric" = length

Discuss Isotonic contraction: * does skeletal muscle change in length? * If muscle tension \> load does the muscle shorten or lengthen? * _____ contraction is another term for muscles lengthening.

Isotonic contraction * skeletal muscle changes length resulting in motion * Muscle tension \> load = muscle shortens * Muscle tension \< load = muscle lengthens * Eccentric contraction is another term for muscles lengthening

\_\_\_\_\_\_\_ occurs when twitches reach maximum tension. A. Complete tetanus B. Incomplete tetanus

B. Incomplete tetanus Incomplete tetanus: twitches reach maximum * If rapid stimulation continues and muscle is not allowed to relax, twitches reach maximum level of tension Complete tetanus: if stimulation frequency is high enough, muscle never begins to relax, and is in continuous contraction