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
Ca2+ binding protein (calmodulin or troponin) for smooth muscle
calmodulin
filament associated with Ca2+ binding protein (thick or thin) for skeletal muscle
thin
filament associated with Ca2+ binding protein (thick or thin) for smooth muscle
thick
G protein-coupled receptors (yes or no) for skeletal muscle
no
G protein-coupled receptors (yes or no) for smooth muscle
yes
question 3, 9, and 10 about muscle twitches
okay!
skeletal muscle thick filament is
myosin
cross bridge cycle
ATP
1. cross bridge attachment - contraction
2. cross bridge energized - contraction
3. Ca2+ pumping back into SR - relaxation
the number of cross bridges participation is ________ ________ to strength of contraction (tension)
directly proportional
the process in a resting skeletal muscle in which the demand for ATP is low
heat
the processes in a moderately active skeletal muscle in which the demand for ATP is increasing
aerobic muscle contractions (with O2)
the processes in a skeletal muscle at peak activity in which the demand for ATP in enormous
anaerobic (without O2)
sources of energy stored in a typical muscle fiber
- ATP (quick)
- number of twitches: 10
- duration: 2 seconds - creatine phosphate (quick)
- number of twitches: 70
- duration: 15 seconds - glycogen (long)
- number of twitches: anaerobic = 670, aerobic = 12000
- duration: anaerobic = 130 seconds, aerobic = 2400 seconds
myoglobin
temporarily stores O2
slow fibers (type 1 - oxidative) characteristics
- sustains relatively weak contractions
- red muscle = myoglobin
- glycogen content = low
- rate of fatigue = slow
- ATPase activity = low aka slow twitch
- fiber diameter = small (low number of cross-bridges
- motor unit size = small (fine movements)
- innervating by small neurons (high mitochondria, longer latent period)
fast fibers (type 2 - non oxidative)
- explosive strong contractions
- white muscle
- glycogen content = high
- rate of fatigue = fast
- ATPase activity = high aka fast twitch
- fiber diameter = large (high number of cross bridges)
- motor unit size = large (crude movements)
- innervating by large neurons (low mitochondria, shorter latent period)
parasympathetic system
slows heart down
sympathetic system
- speeds heart up
- increases contraction
cardiac muscle
- heart
- oxidative phosphorylation only (very aerobic)
- poorly developed SR (sensitive to changes in blood Ca2+)
- autonomic nervous system
isotonic
- muscle shortens
- tension remains
- movement
isometric
- muscles developed tension but does not shorten
- no movement
smooth muscle
- organs (walls of organs are smooth muscle)
- no z-lines, sarcomeres, troponin, t-tubules
- poorly developed SR (longer latent period and longer period of relaxation)
skeletal muscle Ca2+ binding protein and filament
- troponin protein
- thin filament
smooth muscle Ca2+ binding protein and filament
- calmodulin protein
- thick filament
sarcomeres
dense bodies - actin attachments
troponin
Ca2+ binding
t-tubules
cells are extremely small compared to skeletal muscles
