Muscle Physiology (REYNOLDS) Flashcards
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
Muscles have three layers of connective tissue. What are they?
Epimysium, Perimysium and Endomysium
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
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)
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
Which of the following separates muscle from surrounding tissue?
A. Epimysium
B. Perimysium
C. Endomysium
A. Epimysium
Which of the following contains capillaries and nerve fibers contacting muscle cells?
A. Epimysium
B. Perimysium
C. Endomysium
C. Endomysium
Which of the following contains myosatellite cells (stem cells) that repair damage?
A. Epimysium
B. Perimysium
C. Endomysium
C. Endomysium
note: contains capillaries to help repair damage
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
Skeletal muscles fibers develop through fusion of mesodermal cells known as _____.
Myoblasts
List the 4 thin filament proteins:
- F-actin
- Nebulin
- Tropomyosin
- Troponin
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
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
Which of the following contain ONLY actin filaments?
A. Z line
B. M line
C. A bands
D. I bands
D. I bands
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
Which of the following holds F-actin strands together?
A. F-actin
B. Nebulin
C. Tropomyosin
D. Troponin
B. Nebulin
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
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?
- arrival of an action potential at the synaptic terminal
- Release of ACh into synaptic cleft
- Ach binding at motor end plate of synaptic cleft (causing Na+ to rush into the cell)
- 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?
- Exposure of active sites
- Ca2+ binds to receptor on troponin
- Troponin-tropomyosin complex changes exposing active site of F-actin
- Formation of cross-bridges
* “energized” myosin head bind to underlying actin forming cross-bridges - Ratchet Action (pivoting) of myosin heads
* myosin undergoes conformation change termed “ratchet action” that pulls actin toward the center of the sarcomere - Detachment of cross-bridges
- myosin releases ADP
- binding of ATP to myosin decreases the affinity of myosin for actin, thereby releasing myosin from actin
- 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?
- Automacity
- contraction w/o neural stimulation
- controlled by pacemaker
- Variable contraction tension
* controlled by nervous system - Extended contraction time
* 10 times as long as skeletal muscle - 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?
- long, slender and spindle shaped
- have single, central nucleus
- have no T tubules, myofibrils or sarcomeres
- Have no tendons or aponeuroses
- have scattered myosin fibers
- myosin fibers have more heads per thick filament
- have thin filaments attached to dense bodies
- 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
