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M1 Nerve/Musc le
Phys io logy Exam
Review
9/1/04
Stacy Trent and Joe Walsh
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Test Details:
1) Approx. 3 questions per lecture
2) 1.2 minutes per question
3) Department practice exam on
Blackboard
4) TLEs on M1 website (go to: Class
Materials then Physiology)
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Membranes
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Fluid Mosaic Model
Phospholipid bilayerwith proteins and cholesterol embeddedwithin bilayer.
Cholesterol makes bilayerstiffer or more viscous!!
Membrane composition depends on function (ie. More lipid in
Schwann cells and more protein in mitochondria).
Intrinsic/Integral vs. Extrinisic/Peripheral Proteins
Intrinsicproteins span the entire membrane and contain
hydrophillic ends and a hydrophobic core, often serving as
transporters. Extrinsicproteins are present on one side of the bilayer or the
other and are anchored by electrostatic interactions.
Glycolipidscan be conjugated with either an intrinsic or extrinsic
protein and serve as a surface marker for the cell.
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Transport
1) Simple Diffusion
- small, nonpolar > large, polar
2) Osmosis
- water follows solute
3) Facilitated Diffusion
- notenergy dependent transport of solute down itsconcentration gradient
4)Active Transport
- energy dependent transport of solute against itsconcentration gradient
Note: All transport mechanisms exhibit saturation kinetics,chemical specificity and competitive inhibition. Whenthe [substrate] increases, the transportation rateincreases until transport mechanism becomessaturated.
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Diffusion
Diffusionis driven by concentrationgradients.
Ficks 1st Law of Diffusion: Use to calculate Rate of Diffusion Note: C = C1-C2where C1= target compartment
Stokes-Einstein Equation: Use to calculate Diffusion Coefficient
Partition Coefficient() Expresses relative Lipid Solubility
0 (lipid insoluble) 1 (completely lipid soluble)
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J DAC
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D kT
6r
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Which factors allow fast
diffusion?1. Lipid solubility ()- the morelipid soluble, the
faster the diffusion.
2. C- the greaterthe change in concentration,
the faster the diffusion.3. Membrane thickness- the thinnerthe
membrane, the faster the diffusion.
4. Viscosity of membrane- the lessviscous the
membrane, the faster the diffusion.5. Radius of molecule- the smallerthe radius of
the molecule, the faster the diffusion.
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Osmosis
Vant Hoffs Law: =RT(iC)o Use to calculate osmotic pressure
o = pressurerequired to oppose the movement ofwater from an area of high [H2O] (low osmolarity)to an area of low [H2O] (high osmolarity).
Osmotic Flow Rateo Vw=Lo Use to calculate the osmotic flow rate of water
when the membrane is permeable to both water
and solute.o = reflection coefficient(0-1) - a high reflection
coefficient reflects a solute that does NOTpermeate the membrane well.
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Hypertonic vs. Hypotonic
Solutions Hypotonicsolutions have a lowerosmolarity
than cellular osmolarity (0.3 osm) and thus the
cell will swell when placed in a hypotonic
solution. Cell will swell in hypOtonic solution
Hypertonicsolutions have a higherosmolarity
than cellular osmolarity and thus the cell will
shrink when placed in a hypertonic solution.
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Facilitated Diffusion
Helps larger, less soluble molecules cross
the membrane
Dependent on concentration gradient
No Energy Needed!
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Active Transport
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Active Transport
Againstconcentration gradient Requires Energy (ATP)
Primary Active Transport Transporter directlybreaks down an energy
molecules (mostlyATPNa+/K+pump)
Secondary Active Transport Transporter is indirectlydependent on energy
expenditure from another transporter
ex. Na/glucose co-transporter fueled by Na+/K+pump
NOTE: Na+/K+pump = PumpKin(Pump K+in)
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Gated Channels
Utilize gradient: high to low[ ]
Ligand Gated Channels- passivediffusionthrough a
channel opened through ligand binding(hormone or
neurotransmitters)
Voltage Gated Channels- passivediffusionthrough a
channel opened by changes in the membrane potential
Vesicle Mediated Transport
Requires Energy!!
Endocytosis- into cell
Exocytosis- out of cellQuickTime and a
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Membrane Potentials
Results because of an unequaldistribution of charge across a
membrane
Two equations you need to know:1) Nernst Equation
2) Goldmans Equation
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Nernst Equation:
(Dont forget about zvalence of ion)
- Use to calculate the membrane potentialof an
ion atequilibrium
- Represents the electrical potentialnecessary tomaintain a certain concentration gradient of a
permeable solute.
E 60mV
z
log
X AX
B
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Goldmans Equation
Used to calculate overall membrane potential whenmultiple ionsare involved.
Incorporates permeabilityof each ion.
Permeability of K+> Na+> Cl- thus..
K+drives Resting
Membrane Potential
Em (60mv)log
Pk K o PNa Na o PCl Cl i
Pk K
i P
Na Na
i P
Cl Cl
o
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Neurotransmitters
Acetylcholine(ACh) SomaticNS
At neuromuscular junction
AutonomicNS
Preganglionic PNS and SNS neurons Postganglionic PNS
Norepinephrine ANS- postganglionic SNS neurons
GABA Inhibitoryneurotransmitter of brain
Glutamate Excitatoryneurotransmitter of brain
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Receptors
Ionotropic- binding of
NT opens ion channel nACh receptors- Na+
and K+ channels
At neuromuscularjunction and autonomic
ganglion GABA receptors- ligand
gated Cl- channels
Glutamate receptors
Non-NMDA - ligandgated Na+ and K+
channels NMDA
Must bind glycine tobe active
Ligand gated Na, Kand Ca channels
blocked by Mg at rest
Metabotropic- binding
of NT generates a 2ndmessenger which
opens an ion channel
Binding activates G-
proteinwhich activatesand enzyme serving as a
2nd messenger
mAChreceptors
At PNS effector
organs
1, 2, 1, 2, and 3 At SNS effector
organs
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SNS Receptors
1- contraction (sphincters) 2- decreases sections (salivary glands) 1- heart (excitatory) and kidney 2- lungs, pupil (relaxation)Mnemonic: 1, 2 lungs
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Agonists and Antagonists
Pro-PNSEffects Neostigmine- Inhibits Acetylcholinesterase prolonging ACh
activity
Propanolol- antagonist
Pro-SNSEffects Isoprotenerol- agonist Belladonna and Atropine- mACh antagonist
Anti-ANS(both PNS and SNS) Hexamethonium- nACh antagonist (ganglia)
Anti-Skeletal MuscleContraction Curare- nACh antagonist (NMJ)
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Action Potentials (APs)
APsare the result of timeand voltagedependent changes in ionic permeabilityofexcitable cells (i.e. neurons).
Na+
and K+
channelsthat generateAPsare onlyfound at the axon hillock. Any otherdepolarization in a neuron is called a receptorpotential.
APsare ALL-OR-NOTHINGevents. A strongerstimulus only increases the frequencyof firing.
Ph f A ti
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Phases of Action
Potentials1. Slow depolarizationto
threshold
2. Rapid depolarizationdueto opening of voltagedependent Na+channelsleading to Na+influx(Hodgkin Cycle!)
3. Repolarizationdue toincreased K+
conductance leading toK+efflux
4. Hyperpolarization(refractory period)
5. Resting membranepotential
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Refractory Periods
AbsoluteRefractory Period- due to time
dependence of Na+channel
Noamount of inward current will generate another AP
Due to the Na+inactivationgate which is slow to closewhen triggered at threshold
RelativeRefractory Period
Need an excess of currentto generate an APbecause the Na+ channels are still inactivated until
the end of repolarization phase
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Velocity of Conduction
of AP Velocity increaseswith
increaseddiameter of
axon.
Velocity increaseswhenmembrane resistance
increases(myelination!)
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Synaptic Transmission
Presynaptic Membrane:
APCa+2channelsopening Ca+2 influx synaptic vesicle fusion release of NTs
Post-synaptic membrane:
Neurotransmitter binds to
postsynaptic neuron or
muscle leading to
increased conductance
of Na+ and K+ causing agenerator or action
potential.
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Response of Post-Synaptic Cell
Responsemay be inhibitory or excitatory depending on thenature of postsynaptic cell (NOTNeurotransmitter!!)
Temporal or Spatial Summation
Temporal- multiple signals from 1 axon firing in rapid
succession such that successive inputs add to the still-
existent present inputs. Spatial- multiple signals from different axons occurring
simultaneously.
Repetitive Stimulations
Facilitation- successive APs cause postsynaptic membrane
potential to grow more and more intense in amplification
Post-tetanic Potentiation- after repetitive firing, Ca+2
channels are synchronized resulting in a more amplified
EPSP following tetanus
Synaptic Fatigue- delay in response after synapse following
prolonged tetanus (NTs have to be re-packaged)
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Generator vs. Action Potentials
Generator Potentials
Subthreshold
Graded
Intensity of signal =larger response
Decremental
conductance
Longer length constant =less decrement
Larger nerves = longer
length constant
Action Potentials
Over threshold
All or Nothing!!!
Intensity of signal =more frequent Aps
No decrement in
signal
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Autonomic vs. Somatic NS
Somatic NS Acts on skeletal
muscles
1 neuron
ACh nACh (motorend plate)
Controlled by
voluntarythought
(motor cortex)
Autonomic NS Acts on smooth muscle,
glands, cardiac muscle
2 neurons: post andpreganglionic
PreG: ACh nACh
Post G: PNS: ACh mACh SNS: NE or
Controlled by hypothalamus(involuntary)
Associated w/ limbic systemleads to emotionally linkedresponse
Ablation (cant respond tochanges)
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Autonomic NS
Sympathetic Cell bodies of
postganglionicnerves are inganglia near spinal
cord Diffuse control (1:10
ratio of pre to postGfibers)
Shortpreganglionicnerves (ACh nACh receptors)
Longpost ganglionicnerves (NE1,2,
1 and 2)
Parasympathetic Cell bodies of
postganglionicnerves are inganglia near organ
Precise control (1:3ratio of pre to postGfibers)
Longpreganglionicnerves (ACh nACh receptors)
Short postganglionicnerves (ACh mACh receptors)
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SNS vs. PNS
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SNS vs. PNS
SNS = fight or flight
Dilates pupils
Opens airways
Increases heart rate and
BP
Increases blood flow toheart, brain and skeletal
muscle
Inhibits digestion
Piloerection
Gluconeogenesis andglycogenolysis (makes
glucose available)
PNS = rest and digest
Constricts pupils
Restricts airways
Decreases heart rate and
BP
Promotes digestion Increases blood flow to
gut
Increase saliva
Glyconeogenesis (stores
glucose as glycogen)
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SNS vs. PNS
Salivary Secretions: SNS: salivary amylase production PNS: watery saliva
Defecation SNS: motility of colon until appropriate time PNS: motility of colon leads to expulsion of stool
Urination SNS: Relaxation of bladder to allow for fill-up
PNS: Contraction of bladder Erection
SNS: Ejaculation and psychogenic erections
PNS: Erection (ACh NO release
vasodilation)
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Muscle
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Skeletal Muscle
Controlled by Somatic NS
Skeletal muscle specific terms:
Neuromuscular junction
Motor endplateskeletal muscle on thereceiving end of nm junction
End Plate Potential (EPP)generatorpotential of skeletal muscle
ACh release is quantal (miniature endplate potential = 0.4 mV)
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Organization and
Structure of Muscle
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Classification of Muscle
Striated
Muscle
Smooth
Muscle
Multi-Unit
Single-UnitCardiac
Skeletal
FunctionalSyncytium
Automaticity
Motor Unit
Composition
Motor Nerve
Required
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Connective Tissue (Know
this!) Epimysium
surrounds entire muscle
Perimysium separates muscle into bundles of muscle fibers (fascicles)
contains blood vessels Endomysium
separates muscle fascicles into individual muscle cells(myofibers)
contains capillaries
Epimys ium, perimys ium , and endomysium all com e together at
the ends of m uscles to form TENDONS
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Anatomy of a Muscle
c
Nerves and blood vessels are embedded in connective tissue. The major
connective tissue components are collagen and elastin. Muscles are attached
to bones by tendons at their origin and insertion.
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Muscle Growth During Development
Activated
by injury
or trauma
Cell Div is ion
(Hyperplasia)Cell Fusion
Cell Growth
(Hypertrophy)
Satellite Cell
(quiescent)
Re-Enter
the
Cell Cycle
Myoblasts Myotubes
Myofibers
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The SarcomereBasic Contractile Unit in Muscle
M line
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Myofilament Arrangements
I IA
When muscle contracts, the
sarcomere shortens. The I band
and H Zone also shorten. But
the length of the A band remains
the same.
A cross-section through
the A Band/I Band overlap
shows the hexagonal arrayof thick and thin myofilaments
The Thick Myofilament
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The Thick Myofilament
The thick myofilaments are composed of myosin molecules arranged in an
end to end fashion at the M-line. Each myosin is composed of two myosin
heavy chain subunits and two pair of myosin light chains.
Myosin Light Chains
MHC220,000 Daltons
MLC1520,000 Daltons
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Thin myofilaments Actin core
Tropomyosin
Filamentous proteinblocks myosin bindingsite on actin
Troponin Tattaches troponin
complex totropomyosin
Ialong withtropomyosin inhibitsmyosin binding site onactin
Cbinds freeintracellular calcium to
produce aconformationalchange in tropomyosin
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Other Structural Proteins Titin
keeps thick myofilaments centered in sarcomere
extends from M line to Z line, largest MW protein known
Nebulin determines length of thin myofilaments, molecular ruler
Alpha Actininanchors thin myofilaments to the Z-line
Beta Actinindetermines length of thin filaments
Myomesinbinds titin, aligns thick filaments into hexagonal array
Desmincytoskeletal protein, connects adjacent sarcomeres
C-, H-, and X- proteinsform rings around thick filaments, maintains thickfilament structure during contraction
Cap-Z and tropomodulinassociated with opposite ends of growing thinfilaments, regulates length Dystrophinanchors actin filaments to sarcolemma, defective in MD
Myotilininteracts with alpha actinin and Z-lines, sarcomeric organization
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NerveMuscle
Relation
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Some definitions
Motor Unit
Composed of an alpha motorneuron and allthe myofibers innervated by that neuron
Motor Endplate The region of the myofiber directly under the
terminal axon branches
Neuromuscular junction
Where the axon terminal and the motorendplate meet
Size Principle of Motor Unit
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Size Principle of Motor Unit
Recruitment
Input from CNSCorticospinal Tract
Small Cell Body
few myofibers
easily recruited
Large Cell Body
Type IType II
Recruited First
Finesse Contractions
Recruited Last
Forceful ContractionsSpinal chord
Two different motor units within the same myofiber
Acetylcholine receptor
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Acetylcholine receptor
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T-tubules are aligned w/ ends of A band(near myosin heads).
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Excitation-Contraction CouplingResting Muscle
DHP
Receptor
RyR
Receptor
Ca++
Ca++Calsequestrin
Ca++
Ca++
Ca++
Ca++
Ca++
Ca++
Ca+++ +
_ _Ca++
ATP
No
at resting membrane potential
SR-Ca++ATPase
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Excitation-Contraction CouplingContracting Muscle
DHP
Receptor
RyR
Receptor
Ca++
Ca++
Calsequestrin
Ca++
Ca++
Ca++
Ca++
Ca++
Ca++
Ca+++ +
+ +Ca++
ATP
Depolarized
Crossbridge
Formation
Sarcomeric Shortening
Ca++
Ca++SR-Ca++ATPase
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Excitation-Contraction CouplingRelaxing Muscle
DHP
Receptor
RyR
Receptor
Ca++
Ca++Calsequestrin
Ca++
Ca++
Ca++
Ca++
Ca++
Ca++
Ca+++ +
_ _Ca++
ADP + Pi
No
at resting membrane potential
Ca++ SR-Ca++ATPase
Tension is longer than electrical or biochemical events
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Steps in excitation-contraction coupling:
1) Action Potential
2) Depolarization of the T-Tubules - Causes conformationalchange in the DHPR - opens Ca2+channels(Ryr) on
sacroplasmic reticulum
3) Ca2+released from SR into ICF
4) Ca2+ binds to Troponin C cooperatively - causes
conformational change
5) Tropomyosin is out of way
6) Cross-bridge cycling
7) Relaxation via Ca2+ATPase
The Crossbridge Cycle
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Crossbridge
detachmentATP
ADP + Pi
AM
AMATP AMADPPi
A + MADPPi(Charged Intermediate)
Relaxed state
Rigor mortis if no ATP
Crossbridge
energized
Crossbridge
attachment
Crossbrige
Motion
Ca2Actin-Myosin
Binding Sites
3
The Crossbridge Cycle
Features of the
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Crossbridge Motion
Changes in the conformation of the hinge
region of the myosin molecule allow for
swivel motion of the crossbridges that
produces sarcomeric shortening.
Features of the
Crossbridge Cycle
1) CB cycle is repetitive2) CB cycle is asynchronous
3) Tension is proportional to CB number
4) Velocity is proportional to cycle rate
5) Velocity is inversely proportional to load
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Sliding Filament Theory
Describes the mechanism of muscle contraction
Free energy from cleavage of Mg*ATP induces abend in myosin head from a 90 to 45 degreeangle
Actin filaments slide toward the H zone, pullingthe Z lines inward
Sarcomere shortens and muscle contracts
This happens in a wave - not synchronous foreach sarcomere
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Sample Question #1
Lengths at rest:
A band = 1.5 mI band = 1.0 m
H zone = 0.7 m
What is the length of the
a) sarcomere?
b) thin filament?
c) overlap?
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Sample Question #1
Lengths at rest:
A band = 1.5 mI band = 1.0 m
H zone = 0.7 m
What is the length of the
a) sarcomere? 1.5 + 1.0 = 2.5 mb) thin filament? (2.50.7) / 2 = 0.9 mc) overlap? 1.50.7 = 0.8 m
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Sample Question #2
Lengths at rest:A band = 1.5 mI band = 1.0 mH zone = 0.7 mSarcomere = 2.5 m
During contraction, the muscle shortens by 20%. What is the length of the
a) sarcomere?
b) thick filament?
c) I band?
d) H zone?
e) overlap?
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Sample Question #2
Lengths at rest:A band = 1.5 mI band = 1.0 mH zone = 0.7 mSarcomere = 2.5 m
During contraction, the muscle shortens by 20%. What is the length of the
a) sarcomere? 2.50.5 = 2.0 mb) thick filament? 1.5 m (no change!)c) I band? 2.01.5 = 0.5 md) H zone? 2.0[(2) x (0.9)] = 0.2 me) overlap? 1.50.2 = 1.3 m
Length Tension
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LengthTension
Relationship Generation of tension in a muscle depends on its initial
length
Maximal tensioncan be developed at a sarcomeresoptimal length, usually its resting length
At the optimal length, a maximum number of cross-
bridge sites are accessible to the actin molecules forbinding and bending
When a muscle is passively stretched, the thin filamentsare pulled out and there are less actin sites available forcross-bridge binding, decreasing tension
When a muscle is shorter than its optimal length, tensiondecreases because the thin filaments overlap and thethick filaments become forced against the Z-lines
Length vs. Tension
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Length vs. Tension
AT OPTIMAL LENGTH
- maximum # of crossbridges
> OPTIMAL LENGTH
- thin filaments pulled away and less
room on actin for binding = less tension
< OPTIMAL LENGTH
- thin filaments overlap, thick filaments
run into Z lines = less tension
Active State
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Active State
Describes criteria which must be met for
contraction to occur:
a) binding of calcium to troponin C
b) cross-bridge formation
c) ATP splitting
d) cross-bridge motion
Twitch force
Ca-troponin
complex
Myoplasmic [Ca]
Action potential
El ti d C t til C t
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Elastic and Contractile Components
Contractile
Component
Parallel Elastic
Component
Series Elastic
Component
1) Contractile Component: Responsiblefor Active Tension(proportional to # of
crossbridges that cycle)
2) Parallel Elastic Component:
Responsible for Passive Tension
3) Series Elastic Component: Must be
stretched in order to develop active
tension
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Modulation of Muscle
Contraction
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Summation
Muscle force can be modulated by the frequencyof stimulation
Depends on active state and refractory period
Skeletal muscle exhibits a long active state anda short refractory period
Allows a second action potential long before theinitial twitch response is complete
Subsequent twitches build upon the one before,ultimately achieving a tetanus state
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Summation of Twitches
The force of muscle contraction can be increased by increasing the frequency
of nerve stimulation. The key is the difference in the time course for the
action potential, calcium transient, and mechanical response.
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Tetanus and Fatigue
1/sec 5/sec 10/sec 50/sec
Stimulation at low frequencies produces summation of twitches andtetanus. However, when stimulation frequency reaches a rate rapid
enough to produce a complete tetanus, fatigue will develop.
Fatigue in tetany is due to fast twitch muscles
Onset of
Fatigue
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Muscle Architecture
Force production and velocity of shortening of the whole muscle depends
on the architecture. It is important to remember that force is proportional
to myofiber number, while velocity is proportional to myofiber length.
Therefore, strap-like muscles provide the greatest velocity of shortening,
while pennate muscles can generate more force.
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Leverage
Because muscles operate across joints, theforce applied to move an object depends on theleverage factor
LF = Leverage arm / Distance from joint
The farther away from the joint a muscle isinserted, the smaller the leverage factor and theeasier it is to move an object (example: doorhinge)
The closer a muscle is inserted to the joint, thelarger the leverage factor (mechanicaldisadvantage), but the more maneuverable theobject is
Preload Afterload and the Latent Period
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Preload, Afterload and the Latent Period(influence on twitch force)
Preloaded with 10 kg Afterloaded with 10 kg
8 msec latent period 12 msec latent period
Preloaded with 20 kg
8 msec latent period
Afterloaded with 20 kg
20 msec latent period
Action
Potential
Action
PotentialAction
Potential
Action
Potential
Muscle
Twitch
Muscle
Twitch
Muscle
Twitch
Muscle
Twitch
The latent period isprolonged in an after-
loaded muscle because
it takes time to stretch
the series elastic
component.
The length of the latent
period is dependent on
load for afterloaded
muscle, but independent
of load for preloaded
muscle.
Increasing load
decreases twitch
shortening independent
of effects on latent
period.
ExtentofShortening
ExtentofShortening
ExtentofShortening
ExtentofShortening
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Load-Velocity Relationship
As load increases the velocity of shortening decreases.
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Sample Question #3
A muscle which weighs 12 g and is 100 cm long isstimulated for a total of one hour at a frequency
of 4/min. Upon each stimulation the muscle lifts
204 g and shortens 0.5 meters. What is the
work and power output of that muscle?
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Sample Question #3
A muscle which weighs 12 g and is 100 cm long isstimulated for a total of one hour at a frequencyof 4/min. Upon each stimulation the muscle lifts204 g and shortens 0.5 meters. What is thework and power output per hour of that muscle?
Force produced per stimulation = 0.204 kg x 9.81 m/s2= 2.00124 N
Work done during 1 contraction = 2 N x 0.5 m = 1.0 Joules
Work done per hour = 1.0 J x 4/min x 60 min = 240 JPower output over 1 hour = 240 J / 3600 sec = 0.067 Watts
Total work per gram of muscle = 240 J / 12 g = 20.0 J/g
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Rate of Onset of Energy Pathways
Aerobic
Mechanisms
Anaerobic
Glycolysis
Creatine
PhosphatePercentCapacity
ofEnergy
GeneratingSystem
Exercise Duration
10 sec. 30 sec. 2 min. 5 min.
100
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Biochemical Profile Performance Profile
Fiber Type Glycolytic Oxidative MHC-ATPase Fatigue Activity ProfileActivity Activity Twitch Speed Resistance
Fast Twitch White V. High Low High Low Short term phasic
IIB
Fast Twitch Red Moderate V. High High High Sustained phasic
IIA
Slow Twitch Low Moderate Low V. High Sustained Tonic
I
Characteristics of Muscle Fiber Types
The activity profile of the major muscle fiber types matches the biochemical
and contractile profiles for these fiber types.
Anaerobic Threshold
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Anaerobic Threshold
OxygenConsu
mption
(ml/kg/min)
Exercise Work LoadREST
30
45
60
100
20
40
60
80
Blood
Lactate(mg/dL
)
Anaerobic
Threshold
Untrained Trained
Oxygen Debt
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Oxygen Debtoxygen debt and oxygen repayment are equal
Rate
ofEnergyExpen
diture
Time (minutes)
Oxygen Debt
Oxygen Repayment
O
xygenConsump
tion
0 2 8
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Parameters of Endurance Training
Time (months)
AdaptiveR
atio
(Control/Tra
ined)
TCA Cycle
Enzymes
Oxidative Potential
of Fast Fibers
Capillary Density
Slow twitch fiber diameter
VO2Max
1 12 24 6
Training De-training
Effi i C l l ti
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Efficiency Calculations
A 70-kg individual does 20 pullups, lifting his body weight 1 meter eachtime. In doing so, he consumes 4 liters of O2. Baseline is 400 ml ofO2/min. Total exercise time is 5 mins. What is his gross and netmechanical efficiency.
1 L O2 = 4.8 kcal
1 cal = 4.186 J
Effi i C l l ti
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Efficiency Calculations
A 70-kg individual does 20 pullups, lifting his body weight 1 meter eachtime. In doing so, he consumes 4 liters of O2. Baseline is 400 ml ofO2/min. Total exercise time is 5 mins. What is his gross and netmechanical efficiency.
1 L O2 = 4.8 kcal
1 cal = 4.186 J
W = mgh = (70 x 9.8 x 1) x 20 reps = 13.7 kJ
= 13.7 kJ/4.186 kJ/kcal = 3.3 kcal
Effi i C l l ti
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Efficiency Calculations
A 70-kg individual does 20 pullups, lifting his body weight 1 meter eachtime. In doing so, he consumes 4 liters of O2. Baseline is 400 ml ofO2/min. Total exercise time is 5 mins. What is his gross and netmechanical efficiency.
1 L O2 = 4.8 kcal
1 cal = 4.186 J
W = mgh = (70 x 9.8 x 1) x 20 reps = 13.7 kJ
= 13.7 kJ/4.186 kJ/kcal = 3.3 kcal
Total E = 4 L x 4.8 kcal = 19.2 kcalNet E = (4 L0.4 L x 5 min) x 4.8 kcal = 9.6 kcal
Effi i C l l ti
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Efficiency Calculations
A 70-kg individual does 20 pullups, lifting his body weight 1 meter eachtime. In doing so, he consumes 4 liters of O2. Baseline is 400 ml ofO2/min. Total exercise time is 5 mins. What is his gross and netmechanical efficiency.
1 L O2 = 4.8 kcal
1 cal = 4.186 J
W = mgh = (70 x 9.8 x 1) x 20 reps = 13.7 kJ
= 13.7 kJ/4.186 kJ/kcal = 3.3 kcal
Total E = 4 L x 4.8 kcal = 19.2 kcalNet E = (4 L0.4 L x 5 min) x 4.8 kcal = 9.6 kcal
Gros s Efficienc y = W/E = 3.3 kcal/19.2 kcal = 17%
Net Eff ic iency = 3.3/9.6 = 34%
Fib T
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Fiber Types
Metabolism ATPase
activity
Fatigue
Resistance
Contraction Adaptation Example
White
Fast
Glycolysis + - Short term
phasic
hypertrophy Power lift
Slow Red Oxidative - ++ Sustained
tonic
Incr mt
myoglobin
Postural mm
Fast Red Oxid/Glyc + + Sustained
phasic
both rowing
S th M l U it
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Smooth Muscle: Unitary
Present in GI tract, bladder, uterus, and ureter
Contracts in coordinated fashion b/c of gap jxns
Modulated by NTs and hormones
Has pacemaker activity, slow waves
S th M l M lti it
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Smooth Muscle: Multiunit
Found in iris, ciliary muscels of lens, and the vas deferens
Cells dont communicate w/ each other electrically
Densely innervated by autonomics
E it ti C t ti i S th M l
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Excitation-Contraction in Smooth Muscle
1) Action potential opens Ca2+ channels in sacrolemmal membrane
2) Rise in intracellular Ca2+concentration causes Ca2+bind to calmodulin -the Ca2+ - Calmodulin complex binds to and activates myosin light chainkinase(MLCK)
3) Activated MLCK phosphorylates myosin, which can now form an breakcross-bridges
*amount of cross-bridges=tension=intracellular Ca2+
4) Intracellular Ca2+decreases(b/c of SRs Ca2+ATPase) and myosin isdephosphorylated by myosin light chain phosphatase(MLCP)
Ratio of MLCK:MLCP is main determinant of tension in smooth muscle
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Practice Questions for
Nerve/Muscle Physio
Test
9/1/2004
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Choose the correct sequence of events
during excitation/contraction coupling:
a) Action potential, calcium release, depolarization ofthe t-tubules, contraction, calcium re-uptake
b) Action potential, depolarization of the t-tubules,calcium release, contraction, calcium re-uptake
c) Action potential, depolarization of the t-tubules,calcium re-uptake, contraction, calcium release
d) Action potential, calcium release, contraction,depolarization of the t-tubules, calcium re-uptake
C f
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Choose the correct sequence of events
during excitation/contraction coupling:
a) Action potential, calcium release, depolarization ofthe t-tubules, contraction, calcium re-uptake
b) Action potential, depolarization of the t-tubules,calcium release, contraction, calcium re-uptake
c) Action potential, depolarization of the t-tubules,calcium re-uptake, contraction, calcium release
d) Action potential, calcium release, contraction,depolarization of the t-tubules, calcium re-uptake
At equilibrium the concentration of Na + is 5
M i id th ll d 500 M t id th
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mM inside the cell and 500 mM outside the
cell. What is the Na + equilibrium potential
for this cell?
a) +90 mV
b) -90 mVc) +120 mV
d) -120 mV
e) +60 mV
At equilibrium the concentration of Na + is 5
M i id th ll d 500 M t id th
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mM inside the cell and 500 mM outside the
cell. What is the Na + equilibrium potential
for this cell?
a) +90 mV
b) -90 mVc) +120 mV
d) -120 mV
e) +60 mV
A di t th " i i i l " hi h f
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According to the "size principle" which of
the following statements would be true?
a) large motor units are recruited first but generate less force
b) large motor units are recruited first and generate more force
c) small motor units are recruited first and generate more force
d) small motor units are recruited first but generate less force
e) motor unit size and force production are not related so noneof the above are true.
A di t th " i i i l " hi h f
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According to the "size principle" which of
the following statements would be true?
a) large motor units are recruited first but generate less force
b) large motor units are recruited first and generate more force
c) small motor units are recruited first and generate more force
d) small motor units are recruited first but generate less force
e) motor unit size and force production are not related so noneof the above are true.
According to the sliding filament theory,
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According to the sliding filament theory,
which of the following occurs during a
muscle contraction:
a) The thin filaments pull the H zone to the center of thesarcomere.
b) The Z lines pull the thick filaments in the overlapping region.
c) The area of overlap between the thick and thin filamentsincreases, however the actual lengths of the thick and thethin filaments remain unchanged.
d) The width of both the I band and the A band decreases whilethe H zone increases.
According to the sliding filament theory,
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g g y,
which of the following occurs during a
muscle contraction:
a) The thin filaments pull the H zone to the center of thesarcomere.
b) The Z lines pull the thick filaments in the overlapping region.
c) The area of overlap between the thick and thin filamentsincreases, however the actual lengths of the thick and thethin filaments remain unchanged.
d) The width of both the I band and the A band decreases whilethe H zone increases.
W i th bl d l t th
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Warming the blood supply to the
hypothalamus causes
a) shivering.
b) increased pulmonary circulation.
c) piloerection.
d) increased cutaneous circulation.
e) increased mesenteric circulation.
Warming the blood s ppl to the
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Warming the blood supply to the
hypothalamus causes
a) shivering.
b) increased pulmonary circulation.
c) piloerection.
d) increased cutaneous circulation.
e) increased mesenteric circulation.
Which of the following features are the same
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g
in the sympathetic and parasympathetic
nervous system?
a) Average length of preganglionic fibers.
b) Average length of postganglionic fibers.
c) Neurotransmitter in preganglionic fibers.
d) Neurotransmitter in postganglionic fibers.
Which of the following features are the same
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g
in the sympathetic and parasympathetic
nervous system?
a) Average length of preganglionic fibers.
b) Average length of postganglionic fibers.
c) Neurotransmitter in preganglionic fibers.
d) Neurotransmitter in postganglionic fibers.
The following data are given for a skeletal muscle fiber:
Length of thin filament: 0 8um
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a) 1.20 um
b) 1.60 um
c) 1.76 um
d) 2.08 um
e) Cannot be determined from above data.
Length of thin filament: 0.8um
Length of H-zone: 0.4um
The muscle is stimulated under isotonic conditions and
it shortens 20%. What is the approximate length of the
sarcomere in the contracted muscle according to the
sliding filament theory?
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QuickTime and a
TIFF (Uncompressed) decompressorare needed to see this picture.
H-zone = 0.4 um
Thin Filaments = 0.8 um
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0.8 + 0.8 + 0.4 = 2.0 um
2.0 x 80% = 1.6 um
QuickTime and a
TIFF (Uncompressed) decompressorare needed to see this picture.
The following data are given for a skeletal muscle fiber:
Length of thin filament: 0 8um
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a) 1.20 um
b) 1.60 um
c) 1.76 um
d) 2.08 um
e) Cannot be determined from above data.
Length of thin filament: 0.8um
Length of H-zone: 0.4um
The muscle is stimulated under isotonic conditions and
it shortens 20%. What is the approximate length of the
sarcomere in the contracted muscle according to the
sliding filament theory?
GOOD LUCK!!
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GOOD LUCK!! http://www2.uic.edu/stud_orgs/prof/M1/courses/physiology/
BIOCHEM REVIEW NEXT WEEK, SAME TIME,
ROOM TBA
Obi Ekwenna and Jason Emer
QuickTime and a
TIFF (Uncompressed) decompressorare needed to see this picture.
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