exam 3 Flashcards
give a function for actin (which protein makes up thick & thin filaments, which are regulatory proteins - turn off or on, which protein generates active and passive tension)
- contractile protein composing the thin filament
- has regulatory proteins associated with it that determine when sarcomere shortening begins and ends
- is pulled by thick filament during sarcomere shortening
- generates active tension
give a function for myosin (which protein makes up thick & thin filaments, which are regulatory proteins - turn off or on, which protein generates active and passive tension)
- contractile protein composing the thick filament
- provides power for sarcomere shortening
- pulls thin filament during sarcomere shortening
- generates active tension
give a function for titin (which protein makes up thick & thin filaments, which are regulatory proteins - turn off or on, which protein generates active and passive tension)
- protein that generates passive tension whenever sarcomere is stretched beyond its optimal length
- protein that maintains optimal sarcomere length
give a function for tropomyosin (which protein makes up thick & thin filaments, which are regulatory proteins - turn off or on, which protein generates active and passive tension)
- regulatory protein associated with actin
- physically blocks myosin cross bridge binding
- preventing armoire shortening
give a function for troponin (which protein makes up thick & thin filaments, which are regulatory proteins - turn off or on, which protein generates active and passive tension)
- regulatory protein associated with actin
- binds Ca2+ (when present)
- removing tropomyosin block
- allowing for myosin cross bridge binding
- beginning sarcomere shortening
Give a function for each of the following that are involved in excitation- contraction coupling in skeletal muscle: Acetylcholine (ACh), nicotinic receptor, Sarcoplasmic reticulum (SR), Transverse tubules (T- tubules).
acetylcholine:
- neurotransmitter released at all neuromuscular junctions
- binding to a nicotinic receptor on muscle cells initiates a muscle contraction
nicotinic receptor:
- receptor on skeletal muscle cells that binds acetylcholine, causing opening of cation channels that depolarize the muscle cell membrane
sarcoplasmic reticulum:
- storage site for Ca2+ needed to trigger muscle contraction
transverse tubules:
- channels connecting the outside of a muscle cell to its interior
- transmits action potentials to the inside of a muscle cell
list the roles ATP plays in muscle contraction. list the sources of ATP (in order they are consumed), which of the ATP sources would be consumed by red muscle fibers? which sources of ATP would be consumed by white muscle fibers
ATP has 3 major functions in skeletal muscle contractions
- change the shape of the myosin cross bridge (charging the cross bridge) which is then used for shortening the sarcomere
- to cause detachment of the myosin cross bridge to allow for continued contraction
- to pump Ca2+ back into the sarcoplasmic reticulum
sources:
- ATP itself: used 1st in all muscle fibers
- creatine phosphate: used to regenerate ATP and used 2nd in all muscle fibers
- glycogen: used 3rd in white muscle fibers contracting anaerobically
- fatty acids: used 3rd in red muscle fibers contracting aerobically
Compare and contrast red and white muscle fibers. Be sure your answer includes: (1.) Reasons for the color of each fiber; (2.) The relative strength of each fiber; (3.) The relative resistance to fatigue of each fiber; (4.) The major biochemical pathway each fiber uses (i.e., glycolysis or oxidative phosphorylation); (5.) The relative speed of twitch of each fiber (i.e., slow twitch of fast twitch).
red:
- red in color due to presence of hemoglobin
- relatively weak
- relatively high resistance to fatigue
- major biochemical pathway = oxidative phosphorylation
- relatively fast twitch fibers
white:
- white in color due to the presence of glycogen
- relatively strong
- relatively low resistance to fatigue
- major biochemical pathway = glycolysis
- relatively fast twitch fibers
Compare and contrast skeletal, cardiac, and smooth muscle. Make sure your answer includes: (a.) Location of each muscle type in the body; (b.) A description of the muscle’s appearance (i.e., striated or unstriated); (c.) The relative development of SR in each type of muscle; (d.) How the differences in SR development in these muscle types affects the latent periods of these muscle; (e.) The type of control (conscious or subconscious) for each muscle type.
skeletal muscle
- location = attached to bone
- striated appearance
- highly developed SR causing a short latent period
- conscious control
cardiac muscle:
- location = walls of heart
- striated appearance
- medium development of SR causing a longer latent period than skeletal muscle
- subconscious control
smooth muscle:
- location = walls of mist organs
- unstriated appearance
- poorest development of SR causing the longest latent period
- subconscious control
Describe the 4 stages of the cross-bridge cycle. Use the 4 stages to describe the Latch Phenomenon and Stress-Relaxation in smooth muscle.
- attachment of charged myosin cross bridges to thin filament
- changing of shape of charged cross bridged = causing shortening of sarcomere
- detachment of myosin cross bridges = requires input of ATP
- use of ATP from step 3 to change shape of myosin cross bridges
latch phenomenon: allows for extended muscle contraction without additional ATP input/use = smooth muscle remains at step 2
stress relaxation phenomenon: allows for hollow organs to store materials under lower pressure = smooth muscle undergoes step 3 without the need for additional ATP
Briefly describe the events of the latent period of the muscle twitch. Briefly describe the events of the period of contraction of the muscle twitch. Briefly describe the events of the period of relaxation of the muscle twitch.
latent period:
- excitation-contraction coupling = action potential motor neuron
- release of acetylcholine
- binding of acetylcholine to nicotinic receptors
- opening of cation channels
- depolarization of motor end plate
- action potential begins on outside of muscle cell
- action potential transmitted down t-tubules to interior of muscle cell
- action potential triggers release of Ca2+ from SR
- Ca2+ binds to troponin, which moves tropomyosin out of myosin cross bridge
- binding site on thin filament
period of contraction:
- cross bridge cycle (step 1-4 of last question)
period of relaxation:
- Ca2+ actively transported back into SR causing tropomyosin to cover cross bridge binding sites on thin filament
Smitin is a smooth muscle protein that resembles titin, which is found in skeletal muscle. What is the role of titin in skeletal muscle? Is titin more important in active or passive tension in skeletal muscle? Assuming smitin plays a similar role in smooth muscle, should smitin be more or less important to smooth muscle than titin is to skeletal muscle? Defend your answer.
titin creates passive tension (tension is generated whenever skeletal muscle is pulled behind its optimal length)
simitin should be less important in smooth muscle since smooth muscle has a wide range of optimal lengths
Does cardiac muscle more closely resemble red or white skeletal muscle fibers? Defend your answer.
cardiac muscle more closely resembles red muscle fibers. its similar to res muscle fibers in many ways including the color (due to presence of myoglobin), biochemical pathway (aerobic = oxidative phosphorylation), and resistance to fatigue (due to high oxygen use).
what is the ‘on’ switch for skeletal muscle (MLCK or troponin)
troponin
what is the ‘on’ switch for smooth muscle (MLCK or troponin)
MLCK
what is the ‘off’ switch for skeletal muscle (MLCP or tropomyosin)
tropomyosin
what is the ‘off’ switch for smooth muscle (MLCP or tropomyosin)
MLCP
Ca2+ binding protein (calmodulin or troponin) for skeletal muscle
troponin
