Chapter 9 (Midterm 1) Flashcards
What are the differences between force generation and sacromere length?
larger fiber = greater force || more actin/myosin = more cross-bridges forming
In length-tension relationship, what shape does the graph have?
active tension developed in the stimulated fiber = parabolic || passive tension in relaxed fiber = exponential
What is the size principle in muscle?
small motor neurons = stimulated fast
What is tetanus?
maintained contraction in response to repetitive stimulation
What is summation?
increase in muscle tension from successive APs happening during the phase of mechanical activity
What is a twitch?
a mechanical response of a muscle fiber to a single AP
What are fast-oxidative-glycolytic fibers?
combine high myosin-ATPase activity with high oxidative capacity and intermediate glycolytic capacity?
What are slow-oxidative fibers?
combine low myosin-ATPase activity with high oxidative capacity
What are fast-glycolytic fibers?
combine high myosin ATPase activity with high glycolytic capacity
What is isometric conctraction?
muscle develops tension but does not shorten/lengthen || constant length
What is concentric contraction?
tension exceeds load = muscle fiber shortening occurs
What are fast-twitch fibers?
reach peak tension faster than slow twitch
What is cross-bridge cycling?
cycle between cross-bridge binds to thin filament, moves –> cycle repeats
In the cross-bridge cycle, when is ATP needed?
Step 3 in order to cause cross-bridge to detach from actin
How is cross-bridge cycling controlled?
myosin light chain phosphorylation / hydrolysis of ATP
How is cross-bridge cycling stopped?
ATP must stay unhydrolyzed to prevent attachment of cross bridges to myosin
What are cross-bridges
the two globular myosin heads attached (bridged) together by the myosin tails
During the cross-bridge cycle, what happens to actin and myosin?
when myosin is energized via ATP hydrolysis, it binds to actin; ATP binding to myosin breaks this linkage
What is the structure of skeletal muscle cell?
myofibrils, sarcoplasmic reticulum, terminal cisternae, transverse tubules, mitochondrion, cytosol/plasma membrane
What is the form of skeletal muscle?
striated muscle due to the arrangement of the thick/thin filaments (myofibrils)
What are the skeletal muscle’s functions?
support and movement
What are myofibrils function?
contraction
What is the sarcoplasmic reticulum and its function?
muscle endoplasmic reticulum that stores Ca2+ and is released after membrane excitation
What are the characteristics of a skeletal muscle fiber?
multinucleated, many mitochondria, myofibrils/sarcomeres, and Transverse tubules
What is a motor end-plate of a neuromuscular junction?
the highly folded post-synaptic side
What is the muscle metabolic function under aerobic conditions?
production of ATP via ox-phos or glycolysis (less ATP, suitable for low O2)
What size of muscle fibers are better suited for the GLYCOLYTIC pathway and what is the purpose?
larger fibers for strong contractions due to strenuous activity = low O2 conditions
What size of muscle fibers are better suited for the OX-PHOS pathway and what is the purpose?
small fibers
In length-tension relationship, where is the maximum force generated?
at the optimal length
In length-tension relationship, what causes changes in the force generated?
the muscle length
What is a neuromuscular junction?
synapse-like junction between an axon terminal of an efferent nerve fiber and a skeletal muscle fiber
What is a synapse?
junctions between neurons
Where are neuromuscular junctions located?
skeletal muscle
Where are synapses located?
between neurons or between a neuron and an effector cell
How is contraction stopped?
sarcoplasmic Ca2+ must be lowered by closing the ryanodine receptors and removing extracellular Ca2+ via ATPase and Na/Ca exchanger
What is the structure of smooth muscle?
single nucleated, unstriated, actin/myosin in parallel arrangement and anchored to connective tissues at dense bodies
What is the form of smooth muscle?
smooth not striated due to actin and myosin not arranged in sarcomeres, no myofibrils
What are the functions of smooth muscle?
allows organ or blood vessel to undergo change in volume (stretching)
What is a single unit smooth muscle?
less innervated and more gap junctions
What is a multi-unit smooth muscle?
very innervated and few/no gap junctions,
Where is smooth muscle found?
blood vessels and internal organs
Define innervate?
to supply with nerves
Which of the three muscles does it contract the slowest?
smooth muscle
What effect do fast glycolytic fibers have on fatigue?
fatigue very rapidly, highly susceptible to fatigue
What kind of force do fast glycolytic fibers generate?
fast and strong movements
What effect do fast oxidative-glycolytic fibers have on fatigue?
have an intermediate capacity to resist fatigue
What kind of force do fast oxidative-glycolytic fibers have on fatigue?
intermediate force-generating ability
What effect do slow oxidative fibers have on fatigue?
very resistant to fatigue = maintain contractile activity for long periods & barely loss of tension
What kind of force do slow oxidative fibers have on fatigue?
does not produce a lot of tension or contraction, used for maintaining posture and fine movements — small non-rigorous things
