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188 Cards in this Set

  • Front
  • Back
Name 4 broad functions of skeletal muscle
contraction, metabolic, protective, thermoregulation
Give 2 examples of how skeletal muscle regulates temperature
shivering and dissipation of heat
name 2 things skeletal muscle protects
joints and abdominal viscera
Name 3 ways that the skeletal muscle functions metabolically
1. major site for glucose disposal (major insulin target tissue)
2. Major storage depot for glycoge
3. major store of body protein; supplies gluconeoginc amino acis for gluconeogenesis
Name 3 contractional functions of skeletal muscle
Movement of skeleton (force production
2. Respiration, contraction of the diapharm
3. Skeletal muscle pump (postural sway)
what is gluconeogenesis? Give an example of a precursor
synthesis of glucose from noncarbohydrate precursors; protein
What is the function of the postural sway
enhances veinous blood making sure it returns to the heart
What intervates skeletal muscle for the contraction of the diaphram? What spinal cord leve is it?
somatic alpha motor neurons, SC level C4
What are the 3 types of muscle?
skeletal, cardiac, and smooth
which of the muscle types are striatd
skeletal and cardiac
what does it mean to be striated?
that the sarcomere is the basic unit
where is skeletal muscle located?
attached to the skeleton
Where is smooth muscle located?
lines all hollow tubes/ organs
What is the function of smooth muscle?
propells contents
What is the function of cardiac muscle?
to pump the blood
Where is cardiac muscle located?
in the heart
What innervates skeletal muscle?
somatic alpha motor neuron
What is the transmitter for smooth muscle
Acetylcholine
What innervates smooth muscle?
Pacemaker ANS motdifices inherent properties
What intervates cardiac muscle
pacemaker-ANS modifies inherent pacemaking
what are the neurontransmiters for cardiac muscle?
ACh,norepi, and epi
What is the contratile mechanism for skeletal muscle
Actin binds to myosin
Calcium regulated through troponin and tropomyosin
What is the contractile mehcanism for smooth muscle?
actin and myosin react
Calcium binds to MLCJ
What is the contractile mechanism for cardiac muscle
Actin binds to myosin
Calcium regulated thru troponin and tropomyosin
What is the growth/repair of cardiac musle?
hypertrophy only
what is the growth/repair of smooth muscle
hypertrophy and hyperplasia
How does the skeletal muscle of children grow?
By addink sarcameres at the ends
How does the skeletal muscle of adults grow?
hypertrophy
How is skeletal muscle repaired?
fixed post-mitotic, repaired by??
myofiber
muscle/cell fiber
myofibril
long strand w/ in a muscle fiber, that make muscle look straited. run parallel making up individual myofibers
How does the size of myofibrils increase?
w/ exercise and more protein the gerth grows
sarcomere
repeating unit (each single one) that gives the muscle stration. (functional unit)
Runs from1 z line to the next
What are the 3 broad categories of proteins that help muscle function
contractile, calcium regulatory, cytoskeletal
What are the proteins for contractile muscle functions?
actin and myosin
What are the muscle proteins for calcium regulatory muscle function?
troponin and tropomyosin
What are 2 jobs of the cytoskeletal muscle function?
1.Organization-provides a scaffold for muscle structure
2. Plays a key role in providing the force for muscle contraction
Which function are most dystrophies and myopathies a distruption of
cytoskeletal
Name 3 types of connective tissue
epimysium, perimysium, endomysium
Epimysium
surrounds/sits upon the whole muscle
Perimysium
surrounds muscle bundles
Endomysium? fxns?
surrounds individual muscle cell/fiber
interacts w/ other endomysium for organization
helps to transmit force
What are 4 properties of skeletal muscle?
excitability, relaxation, contraction, elasticity
What is the electrical switch that triggers excitability in skeletal muscle?
calcium
Which homeostasis system must be in order for proper excitation of skeletal muscle?
homeostasis of electrolytes
What part of skeletal muscle is excitable?
excitable plasma membrane with voltage regulated channels
Why is elasticity of skeletal muscle necessary?
so it can return to its post contractile/pre-streteched state
Which part of skeletal muscle is responsible for elasticity?
cytoskeleton
What is relaxation of muscle dependent upon?
a pump to remove calcium
What does relaxing a muscle do?
it stops the contraction
Where are costameres found?
connected to the sarco lamina
@ all z discs
@ all m line regions
@ muscle tendon junctions
What does a sarcomere contain?
transmembrane and extracellular membrane proteins
Which part of the muscle extends the entire length of the myofibril?
titin
Which protein is most important for elasticity
titin
Where does desmin connect?
w/ in the sarcomrere and w/ in the plasma membrane @ the z lines
What does desmin connect?
adjacent myofibrils at z lines`
What disease is a result of mutation of Distrophin?
Jerry's kids and 1 other?
What is distrophin?
Intracellular protein that connects thin filament to SL
What is the fxn of distrophin?
maintain the integrity of the SL
maintain the integrity of contractions
Why is the relation ship btwn strucutre and function important?
Mutation of proteins can lead to dystrophies and myopathies
2 facts about force
1. Force transmitted laterally, as well as length
2. 50% of foce goes out into extra cellular matrix
Name 3 thick fillament proteins?
myosin, titin, myosin binding proteins
What is the fxn of each myosin head?
binding site for nucleotide and actin
What is a nucleotide on myosin?
enzymatic site that hydrolyzes
-ATP: ATP→ ADP + Pi
What do myosin binding proteins do?
stabilize myosin filament
what compacts together forming the backbone?
myosin
what spans half the sarcomere?
titin
What is on Each side of PVEK? What happens when you unfold this?
Ig; stretch PEVK
What are IG & PEVK. #
1. Elastic element that gives passive tension ( w/ out calcium/nerve intervention)
2. Scaffold for myofibillogenesis
3. Kinase activity @ M-line-signals
Name thin fillament proteins
1. Actin
2. Troponin-calcium
3. Tropomyosin-calcium
4. Nebulin
What is nebulin
· Prolocates in thin filament
· Molecular ruler: runs from z-line to thin filament, limiting the length of the actin filament
What makes up the z disc? Where is it located?
1. Titin, actin, desmin
2. in the thin fillament
What is the fxn of the z-disc?
Signaling molecules/development of muscle
What are the cell organelles?
1.Sarcoplasmic Reticulum

2.Mitochondria

3.T tubules
What is the fxn of the sarcoplasmic reticulum?
Stores, releases, sequesters clacium
What is the plasma membrane?
Transveres tubule
What is the fxn of the mitochondria? what determines its plasticity?
1.Takes transferred energy and produces ATP
2. Plasticity based on exercise, pattern, usage
What determines the density of the capallaries
Density is Plastic, changes w/ aerobic training
What is myonuclei?
“nuclear domain" that can sustain and support a limited area of the myofiber
Describe the relationship between hypertrophy and myonuclei
If you hypertrophy, you need more myonuclei, which are fixed post mitotic, so you must get it from stem cells
What are satellite cells?
source of stem cells for myonuclei
§ Mitosis of satellite cells→ formation of another satellite cell and a new myonuclei
Where are satelite cells located? what must be intact for them to work?
Located outside the SL in the Basal Lamina,basal lamina
Name 7 functions of the basement membrane?
1. Morphogenic and trophic role in development
2. Site for attachment of growth factors and hormone
3. Scaffold for development and repair
4. Maintain membrane (SL) integrity
5. Keep the satellite cell in close proximity to myofiber
6. Basal Lamina for peripheral nerve regeneration
7. Proteins function as important signaling proteins
Name 2 intracellular proteins that connect intrasarcomeric proteins w/ the basement membrane
Dystrophin-anchors thin fillament to plasma membrane
costameres
Name 4 proteins of the basememnt membrane
1. Lamin
2.Integrin
3. Dystroglycans
4. sarcoglycans
What happens when there are mutations in Dystroglycans?
limb-girdle/ facial scapalithies?
What kind of proteins is Sarcoglycan? What is the result of mutations of sarcoglycan?
Transmembrane
progressive muscle weakness ie tible gerty?
What kind of protein is Integrin? What are it's fxns? What are the results of mutations in Integrin?
Transmembrane proteins
Signaling/adhesion
Myopaties
What kind of protein is Lamin ? What is its xn? what are the results of mutations of Lamin
?
1. Extracellular matrix protein
2. Signaling
3. Mutation→ myopathies
Describe the sliding fillament mechansim
Force at one end, length at the other
Too long/short=lose all overlap
What is a powerstroke?
movement of myosin head, allowing form movement of muscle
-Only 1 head of each myosin can attach @ 1 time, although there are 2 head
Describe the Early experiment :Length Tension Relationship of muscle
-Length muscle is placed @ where it correlates w/ tension.
- Found point of maximum tension, Lo, which is the point of maximum overlap of actin and myosin
-Isolated myofiber→ tethered to force transducer (measures force) and a mechanism to change the length
-Isometric contractions: @ fixed length giving max. stimulus
-Measured the tension of contactions
What is the approx. Lo of a frog?
Lo in a frog is approx. 2.2
What does the length the muscle is placed at correlate w/
tension
What is Lo?
The point of max. tension, which is the point of optimal overlap of actin and myosin
What are isomeric contractions?
Isometric contractions: @ fixed length giving max. stimulus
Name the 3 early experiments
Lenght tension relationship of muscle
Electron micrographs
Enzyme treatment of myosin
What did the enzyme treatmeant of myosin do?
Find points where myosin is flexible/breaks easily
What are the 2 later experiments?
Sliding fillament assay
Xray-Crystallography of Contractile proteins
What was discovered from Xray-Crystallography of Contractile proteins
1. See both actin binding site & ATP
2. Exist bound to either of those sites
3. ATP types can hydrolyze it also (fast and slow)
4. Light chains play a role in modifying ATP pocket in hydrolysis
Describe the Actin and myosin interaction
1.A+M•ATP→(ATP hydrolysis) A+M*•ADP•Pi
· Energized head still not attaced to myosin
2. A+M*•ADP•Pi→ (calcium) A•M*•ADP•Pi
3. A•M*•ADP•Pi → A•M + ADP + Pi (release hydroylsis products→ A•M (Rigor State)
4. A•M + ATP→ (ATP binding) A + M• ATP
What represent the rigor state? what is the rigor state?
A bound to M; Can't be detached by external forces
What is the net result of 1 power stroke?
hydrolysis of one ATP
What 2 things can myosin exist bound to?
nucleotide or actin
What does the state of A•M*•ADP•Pi represent?
a pre-power stroke state where actin is weakly “docked” to myosin
What happens during maximal contraction?
15-30% of crossbridges are attached at any one time
What is the rate limiting step? What does this step allow?
The release of Pi is the rate-limiting step in myofibrillar ATPase reaction. The release of Pi allows myosin to proceed to a force-generating state
Each cross-bridge action requires
1 ATP
When does eschemic burn occur?
once over 50% of maximum effort of contraction
The binding of ATP @ the end of the power stroke causes ?
a dramatic decrease in the affinity of myosin for actin
Name 4 Calcium release units
1. Dihydropyridine Receptors
2. Ryanodine Receptors
3. Calsequestrin
4. SERCA
What is SERCA?
Calcium pump that pumps calcium back into SR
Requires ATP/energy
What is calsequestrin?
Binding protein that binds and stores calcium
What do Ryanodine Receptors
do?
allow calcium out
Describe Dihydropyridine Receptors and their fxn
-On the T-tubule
-Forms calcium release unit w/?
-Voltage synsetive
-When calcium is released it gates open Ryanodine Receptors
What is malignant hypotherma?
genetic mutation of Calcium release, get too much calcium, creating a lot of contractions/heat→ potentially lethal
What are 3 fxns of ATP dealing w/ Actin myosin interaction
1.Provides energy for power stroke
2. Breaks rigor state when binds to ?
3. Pumps calcium so muscle can relax (when muscles fatigue it takes longer for them to relax
Name 2 calcium regulatory proteins
Troponin and Tropomyosin
What do troponin and tropomyosin have in common when it comes to inhibition?
Convey an inhibitory conformation onto the contractile proteins that prevents actomyosin interaction
Inhibition can be removed in the presence of calcium
What does tropomyosin look like? How big is it?Where is it?What does it do in the abscence of calcium? What happens when calcium is added?
-Rod shaped protein
-Spans the length of about 7 actin molecules
-Attached end to end forming a chain that is intimately associated w/ F-actin
-Covers myosin binding sites on actin in the absence of calcium
-When calcium is added tropomyosin moves and releases myosin binding sites
What happens when calcium binds to troponin?
-Induces conrormational change in torpomysin
-Tropomyosin moves so that actin binding sites are exposed
-Allows formation cross bridges-actomyosin complexes
What does troponin look like? Where is it? What is its function? special feature?
-Small gobular protein
-Bound to actin and tropomyosin
-Helps secure tropomyosin position covering actin sites for yosin
-Contains a binding site that reversible binds calcium
Describe an alpha motor neuron
-There is 1 alpha motor neuron/ myofiber
-An alpha motor neuron may branch and innervate a number of neighboring myofibers
What is the motor end plate? What happens when ACh is released?
-Site where alpha motor neuron synapses onto the myofiber
-ACh release results in local potential change called an EEP
What is the neuromuscular junction NMJ?
Where neuron comes in and connects to motor end plant
What 3 things make up the NMJ?
1. Presynaptic axon terminal
2. Synaptic cleft
3. Postsynaptic membrane on the myofiber
What is the postsynaptic receptor of the NMJ?
nicotine
What is this a discription of?
-Ligand operated-won’t open unless it has 2 Ach bound to it
-Allow local conductance to small cations (mainly sodium)
NMJ
Describe the process of Excitation Contraction Coupling
LOONG-see notes
What stops contraction in the presence of calcium?
1. Cesation of neural drive to contract (release ACh)
2. The enzyme Acetylcholinesterase degrades ACh. ACh→ choline + acetate
3.the sarcoplasmic reticulum by the calcium ATPase
What happens when ceasing contraction in the absence of calcium?
1. In the absence of calcium, calcium regulatory proteins confer an inhibitory conformation that prevents actomyosin interaction
What is a twich contraction?
mechanical response of muscle to a single stimulus
What is the latent period? What can affect it?
-Period between when action potential is propogated and when there is
-Can be affected by fiber type and how quickly ATP can be developed
When does contraction begin to relax?
right after it reaches peak
What stops contraction in the presence of calcium?
1. Cesation of neural drive to contract (release ACh)
2. The enzyme Acetylcholinesterase degrades ACh. ACh→ choline + acetate
3.the sarcoplasmic reticulum by the calcium ATPase
What stops contraction in the presence of calcium?
1. Cesation of neural drive to contract (release ACh)
2. The enzyme Acetylcholinesterase degrades ACh. ACh→ choline + acetate
3.the sarcoplasmic reticulum by the calcium ATPase
What happens when ceasing contraction in the absence of calcium?
1. In the absence of calcium, calcium regulatory proteins confer an inhibitory conformation that prevents actomyosin interaction
2.Serca (calcium pumps) pump calcium back inside the muscle
What is a twich contraction?
mechanical response of muscle to a single stimulus
What is the latent period? What can affect it?
-Period between when action potential is propogated and when there is
-Can be affected by fiber type and how quickly ATP can be developed
What happens when ceasing contraction in the absence of calcium?
1. In the absence of calcium, calcium regulatory proteins confer an inhibitory conformation that prevents actomyosin interaction
2.Serca (calcium pumps) pump calcium back inside the muscle
When does contraction begin to relax?
right after it reaches peak
What is a twich contraction?
mechanical response of muscle to a single stimulus
What is the latent period? What can affect it?
-Period between when action potential is propogated and when there is
-Can be affected by fiber type and how quickly ATP can be developed
What stops contraction in the presence of calcium?
1. Cesation of neural drive to contract (release ACh)
2. The enzyme Acetylcholinesterase degrades ACh. ACh→ choline + acetate
3.the sarcoplasmic reticulum by the calcium ATPase
When does contraction begin to relax?
right after it reaches peak
What happens when ceasing contraction in the absence of calcium?
1. In the absence of calcium, calcium regulatory proteins confer an inhibitory conformation that prevents actomyosin interaction
2.Serca (calcium pumps) pump calcium back inside the muscle
What is a twich contraction?
mechanical response of muscle to a single stimulus
What is the latent period? What can affect it?
-Period between when action potential is propogated and when there is
-Can be affected by fiber type and how quickly ATP can be developed
When does contraction begin to relax?
right after it reaches peak
What is required for relaxation?
ATP is required to pump calcium back in (relax)
Which take longer: building up tension or relaxing
relax
What makes it harder to relax?
being fatigued
How do u determine the size of a motor unit? In a hand? In a leg? Why
Size-based on the # of myofibers; 300; 1000; less myofibers if it need so do more specific movements
what is a motor unit
1 alpha motor neuron and all the myofiber that innervates it
What happens to subsequent tensions w/ no relaxation inbetween? Why?
• Tension increased when relaxation is not allowed b/c the calcium has not been uptaken, therefore there is more available
Skeletal muscle force is porportional 2?
intracellular calcium concentration & the PCSA-physiological cross sectional area of muscle
Increase in action potential does what to the myofiber?
increases calcium inside the myofiber
What is teatnus?
the maximal response of muscle to high frequency
What are 2 ways to increase the force of contraction of the whole muscle?
1. Increase action potential frequency
2. Recruitment of more motor neurons
What is the approx. Lo for humans?
 Many times it is beneficial to begin w/ a decline
-Optimal operating range for Human muscle is 2.6 micron meters; sometimes it is beneficialto begin w/ the decline
What happens@ maximum isometric tension
zero velocity, you can't move
What is MVC maximum isolated/voluntary contraction
-Can hold, but not shorten
-Can hold a little more until all of a sudden you can’t hod at all
When is power the greatest?
@ 30% load b/c power=work/time
What are the 3 major myofiber classifications?
FO; FOG, SO
Name 4 sources of ATP
1.Stored in ATP cell
2. Creatine Phospate
3. Oxidative Phosphorylation (aerobic metabolism)
4.Substrate Phosphorylation (anaerobic metabolism)
How much aTP stored in the cell? How fast is it depleted?
very limited, used quicly
What is creatine phosphate? What does it do to make ATP? What enzyme is involved? How much is it/how long does it last? What happens when there excess?
-Muscle protein loses phosphate b/c of enzyme creatine kinase
-Phosphate binds to ADP to make ATP
-Very limited/ depleted quickly
-Excess draws water into muscle cell (giving the appearance of hypertrophy)
How does oxidative phosyphorylation work? efficient?How long does it last? What is the negative part?
-Aerobic metabolism
-Completely oxidize fuels-krebs cycle and electron ttransport chain
-Very efficient- lots of ATP for little fuel
-Long lasting, but takes time to begin
How does substrate phosphorylation work?
anerobic metabolism
glucose to pyruvate to lactate
what is glycolysis
glucose to pyruvate
How does Myosin ATPase distinguish myofiber classifications?
-fast vs. slow muscle
-Hyrolysis site and myosin nature of alpha motor neuron makes the distinction
What does Succinate Dehydrogenase distinguish between in myofiber classification?
oxidative vs. nonoxidative fibers
What does Alpa-glycerophosphate dehydrogenase distinguish between?
glycolytic potential
What is Immunohistochemical clastification of MHC (myosin Heavy chain) do?
identifies 4 major fiber types?
what are the 4 major fiber types identified by Immunohistochemical clastification of MHC (myosin Heavy chain) ? Describe them
Type 1: similar to slow oxidative
Type 2: similar to fast oxidative
Type 2B: similar to fast glycolitic
Type 2X: in between
Where is there evidence of fiber type conversions?
-Cross Innervation Studies of the Cat Hindlimb
-Training Induced Changes
What is the only way change from a slow fiber to a fast fiber?
denerverate and renerverate
If you do a lot of aerobic work your fibers are more...?
oxidative
If you do a lot of sprinting/lifting your fibers are more...?
glycolitic
What kind of pathways can fast fibers have?
oxidative or glycolitic
What kind of pathways can slow fibers have?
oxidative
Can a motor unit have different myofiber characteristics?
• 1 motor unit will have all the same myofiber characteristics
What is the order of recruitment of motor units?
1. Recruit ones that last a long time
2. Then fast oxidation
3. Finally fast glycolitic
-Therefore 1→2A→2B
Which fibers are most easily brought to threshold?
smaller oxidative
Rank the fibers based on Maximum Contraction Velocity expressed as fiber length/sec
2B>2X>2A>1
Rank the fibers based on Maximum Tension expressed as force/unit area
o
-Fast muscle slight>slow muscle (smaller)
-2B>2A>1
what is the best predictor of maximum force?
the size of the myofiber, Force is proportional to the PCSA of fiber size
Rank the fibers based on endurance
SO>FOG>FG