Unit 2: Muscle Flashcards
What are two major functions of the Muscular System?
Facilitates movement, metabolic reservoir (glycogen), and body support/protection (abs)
What are the three types of muscle?
Skeletal, Cardiac, and Smooth
Which types of muscle are considered striated?
Skeletal and Cardiac muscle are considered striated.
Shape of skeletal muscle
Long, cylindrical
Shape of cardiac muscle
Branched
Shape of smooth muscle
Spindles, non striated.
Tendons
collagen fibers that attach muscle to bone
What are the levels of muscle anatomy?
Muscle,muscle fiber, myofibril,sarcomere
What level of muscle anatomy is considered a muscle cell?
The muscle fiber level
How are muscles created?
Myoblasts grow and fuse together, multiple nuclei, do not undergo mitosis
Describe the process of hypertrophy
During exercise, the muscles swell, proteins are created, and the muscle tears. Satellite cells come in and help with regrowth and fusion with the help of hormones.
A Band
Overlap with actin and myosin
I Band
No overlap with actin and myosin
Z line
Connection of actins
H zone
just myosin
Titin
elastic fibers associated with myosin moving from z line to myosin
Two major components of actin
Troponin, and tropomyosin
Tropomyosin
Blocks myosin at rest to prevent contraction
Troponin
Binds to calcium to move tropomyosin
Contraction
binding of myosin to actin
T tubules
communicating depolarization at the membrane to all fibrils
Sarcoplasmic Reticulum (SR)
membrane tunnels that encase myofibrils, can send calcium to the muscles
What is the geometric ratio of thick/thin filaments?
6 thin filaments surround 1 thick filament. 3 thick filaments surround one thin filament
Terminal Cisternae
The ends of the SR encompassed near the T tubules
Sarcolemma
The name of muscle cell membrane
Motor End plate
The place where the neuron interacts with the sarcolemma (muscle cell membrane)
Junctional folds
At the neuromuscular junction, where there exist folds for increased surface area.
What type of transmitter and receptor is used at neuromuscular junctions?
Acetylcholine is used at nicotinic receptors.
What is important about the end result of acetylcholine at a neuromuscular junction?
It must be degraded by acetylcholinesterase so that the Na+ channels can close.
What is a local depolarization of the motor end plate called?
An EPP (end plate potential)
What is a difference between an EPSP and an EPP?
An EPP is much larger due to increase surface area from the junctional folds. This means that usually only one action potential is needed for the postsynaptic cell to create its action potential.
Neuromuscular IPSPs
do not exist.
D-Tubocurarine (curare)
Ach antagonist. Binds to the receptor, but does not cause opening of Na+ channels. No depolarization in muscle. Can cause death by lack of contraction of the lungs (asphyxiation)
Organophosphates/ “Nerve Gas”
Prevents the action of acetylcholinesterase, which cannot degrade Ach, therefore keeping channels open. inactivation and desensitization of Na+ channels cause paralysis.
Succinylcholine
Agonist, produces a depolarizing block similar to nerve gas. Used during surgery
Botox
Prevents the release of Ach vesicles from the presynaptic by degrading SNARES that would otherwise help to fuse the vesicles with the presynaptic membrane.
Latent period
The time between the action potential, and the muscle contraction reaction.
Relationship between Ca2+, tropomyosin, troponin, and the myosin head
In the presence of high amounts of Ca2+, the troponin moves the tropomyosin away from the binding site so that myosin can bind.
Relationship between sarcolemma, T tubules, terminal cistern, DHP receptors, ryanodine, and Ca2+
During an action potential, signal propagates from sarcolemma down the T tubules, to the DHP receptor, which acts as a voltage sensor. The DHP tugs on the ryanodine receptor, opening it so that Ca2+ can flow into the cytosol and work with troponin.
ATP is required for what part of Ca2+ movement?
ATP is required for reuptake of Ca2+ after it has attached to troponin.
Cross Bridge Cycle: Step 1
Elevated Ca2+ causes combination of ADPxPxAxM
Cross Bridge Cycle: Step 2
Power Stroke and release of ADPxP from AxM
Cross Bridge Cycle: Step 3
New ATP is added to break Myosin from Actin, however, ATP IS NOT BROKEN HERE AS ENERGY but is rather an allosteric modulator.
Allosteric Modulator
When the addition of a charge on one part of a protein causes a conformational change
Cross Bridge Cycle: Step 4
ATP is hydrolyzed into ADPxP and attaches to myosin, again energizing it.
Contraction time
Time from action potential to peak tension
Isometric Contraction
Same length, different load
Isotonic Contraction
Same load, different length
Different types of Isotonic contraction
Eccentric and Concentric
Which type of twitch has a greater latent period?
Isotonic
What does contraction time depend on?
Ca2+ and rate of ATPase
Light Load [shortening velocity,peak shortening, rate of re-lengthening]
fast shortening, and a large peak shortening, slow rate of re-lengthening.
Heavy Load [shortening velocity, peak shortening, rate of re-lengthening]
slow shortening, and a small peak shortening, fast rate of re-lengthening.
Sources of Energy Metabolism in Skeletal Muscle
ATP is produced from Creatine phosphate, from Glycolysis, and from Oxidative phosphorylation.
What are some possible causes of fatigue?
Slow Ca2+ handling, desensitivity to Ca2+, inhibited cross bridge cycles
Slow Oxidative {SO} Type I Fibers: [Primary ATP Source,Mitochondria,Rate of fatigue,contraction velocity,fiber diameter]
Oxidative phosphorylation,many mitos , slow rate of fatigue,slow velocity,small fiber diameter
Fast-Oxidative-Glycolytic Fibers {FOG} Type IIa: [Primary ATP Source,Mitochondria,Rate of fatigue,contraction velocity,fiber diameter]
Oxidative phosphorylation, many mitos, intermediate rate of fatigue,fast contraction velocity,large fiber diameter
Fast-Glycolytic-Fibers {FG} Type IIb: [Primary ATP Source,Mitochondria,Rate of fatigue,contraction velocity,fiber diameter]
Glycolysis,few mitos, fast rate of fatigue, fast contraction velocity, large fiber diameter
During endurance training:
Increased mitochondria, increased blood circulation, increased FOGs, decreased FG, mildly decreased muscle fiber diameter
During strength training:
Increase in FG fibers, hypertrophy, fast fatigue, improved recruitment
Hormones involved in whole muscle growth [for and against]
IGF1 and Androgens promote, myostatin inhibits.
Muscle soreness is most likely due to extensive ____ contractions
eccentric
Smooth muscle structure
diagonal junctions with dense bodies
Differences of smooth muscle from skeletal muscle
smaller, 1 nucleus per cell, autonomic, multiple optimal lengths, Ca2+ from SR and extracellular, no troponin
Latch State
prolonged contraction of smooth muscle due to slow or stopped cross bridge cycling, e.g: sphincter
Smooth muscle signaling pathway
Cytosolic Ca2+ goes up, activates calmodulin, which activates myosin light chain kinases to phosphorylate myosin cross bridges towards actin filaments with the help of ATP.
[true/false] signals received by smooth muscle can only be excitatory, like skeletal muscle.
false
