NerveMuscle Physiology Exam

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M1 Nerve/Muscle Physiology ExamReview9/1/04Sta
cy Trent and Joe Walsh
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• Test Details
• Approx. 3 questions per lecture
• 1.2 minutes per question
• Department practice exam on Blackboard
• TLEs on M1 website (go to Class Materials then
  Physiology)

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Membranes
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• Fluid Mosaic Model
• Phospholipid bilayer with proteins and
  cholesterol embedded within bilayer.
• Cholesterol makes bilayer stiffer 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
• Intrinsic proteins span the entire membrane and
  contain hydrophillic ends and a hydrophobic core,
  often serving as transporters.
• Extrinsic proteins are present on one side of the
  bilayer or the other and are anchored by
  electrostatic interactions.
• Glycolipids can 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 gt large, polar
• 2) Osmosis
• - water follows solute
• 3) Facilitated Diffusion
• - not energy dependent transport of solute
  down its concentration gradient
• 4) Active Transport
• - energy dependent transport of solute
  against its concentration gradient
• Note All transport mechanisms exhibit saturation
  kinetics, chemical specificity and competitive
  inhibition. When the substrate increases, the
  transportation rate increases until transport
  mechanism becomes saturated.

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Transport
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Diffusion

• Diffusion is driven by concentration gradients.
• Ficks 1st Law of Diffusion
• Use to calculate Rate of Diffusion
• Note ?C C1-C2 where 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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Which factors allow fast diffusion?

• Lipid solubility (?) - the more lipid soluble,
  the faster the diffusion.
• ?C - the greater the change in concentration, the
  faster the diffusion.
• Membrane thickness - the thinner the membrane,
  the faster the diffusion.
• Viscosity of membrane - the less viscous the
  membrane, the faster the diffusion.
• Radius of molecule - the smaller the radius of
  the molecule, the faster the diffusion.

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Osmosis

• Vant Hoffs Law pRT(?iC)
• Use to calculate osmotic pressure
• p pressure required to oppose the movement of
  water from an area of high H2O (low osmolarity)
  to an area of low H2O (high osmolarity).
• Osmotic Flow Rate
• VwL??p
• Use to calculate the osmotic flow rate of water
  when the membrane is permeable to both water and
  solute.
• ? reflection coefficient (0-1) - a high
  reflection coefficient reflects a solute that
  does NOT permeate the membrane well.

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Hypertonic vs. Hypotonic Solutions

• Hypotonic solutions have a lower osmolarity than
  cellular osmolarity (0.3 osm) and thus the cell
  will swell when placed in a hypotonic solution.
• Cell will swell in hypOtonic solution
• Hypertonic solutions have a higher osmolarity
  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

• Against concentration gradient
• Requires Energy (ATP)
• Primary Active Transport
• Transporter directly breaks down an energy
  molecules (mostly ATPNa/K pump)
• Secondary Active Transport
• Transporter is indirectly dependent 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 - passive diffusion through
  a channel opened through ligand binding (hormone
  or neurotransmitters)
• Voltage Gated Channels - passive diffusion
  through a channel opened by changes in the
  membrane potential
• Vesicle Mediated Transport
• Requires Energy!!
• Endocytosis - into cell
• Exocytosis - out of cell

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Membrane Potentials

• Results because of an unequal distribution of
  charge across a membrane
• Two equations you need to know
• Nernst Equation
• Goldmans Equation

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• Nernst Equation
• (Dont forget about zvalence of ion)
• Use to calculate the membrane potential of an ion
  at equilibrium
• Represents the electrical potential necessary to
  maintain a certain concentration gradient of a
  permeable solute.

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• Goldmans Equation
• Used to calculate overall membrane potential when
  multiple ions are involved.
• Incorporates permeability of each ion.
• Permeability of K gt Na gt Cl- thus..
• K drives Resting
• Membrane Potential
• 
  

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Neurotransmitters

• Acetylcholine (ACh)
• Somatic NS
• At neuromuscular junction
• Autonomic NS
• Preganglionic PNS and SNS neurons
• Postganglionic PNS
• Norepinephrine
• ANS- postganglionic SNS neurons
• GABA
• Inhibitory neurotransmitter of brain
• Glutamate
• Excitatory neurotransmitter of brain

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Receptors

• Ionotropic - binding of NT opens ion channel
• nACh receptors - Na and K channels
• At neuromuscular junction and autonomic ganglion
• GABA receptors - ligand gated Cl- channels
• Glutamate receptors
• Non-NMDA - ligand gated Na and K channels
• NMDA
• Must bind glycine to be active
• Ligand gated Na, K and Ca channels blocked by Mg
  at rest

• Metabotropic - binding of NT generates a 2nd
  messenger which opens an ion channel
• Binding activates G-protein which activates and
  enzyme serving as a 2nd messenger
• mACh receptors
• 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-PNS Effects
• Neostigmine - Inhibits Acetylcholinesterase
  prolonging ACh activity
• Propanolol - ? antagonist
• Pro-SNS Effects
• Isoprotenerol - ? agonist
• Belladonna and Atropine - mACh antagonist
• Anti-ANS (both PNS and SNS)
• Hexamethonium - nACh antagonist (ganglia)
• Anti-Skeletal Muscle Contraction
• Curare - nACh antagonist (NMJ)

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Action Potentials (APs)

• APs are the result of time and voltage dependent
  changes in ionic permeability of excitable cells
  (i.e. neurons).
• Na and K channels that generate APs are only
  found at the axon hillock. Any other
  depolarization in a neuron is called a receptor
  potential.
• APs are ALL-OR-NOTHING events. A stronger
  stimulus only increases the frequency of firing.

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Phases of Action Potentials

• Slow depolarization to threshold
• Rapid depolarization due to opening of voltage
  dependent Na channels leading to Na influx
  (Hodgkin Cycle!)
• Repolarization due to increased K conductance
  leading to K efflux
• Hyperpolarization (refractory period)
• Resting membrane potential

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Refractory Periods

• Absolute Refractory Period - due to time
  dependence of Na channel
• No amount of inward current will generate another
  AP
• Due to the Na inactivation gate which is slow to
  close when triggered at threshold
• Relative Refractory Period
• Need an excess of current to generate an AP
  because the Na channels are still inactivated
  until the end of repolarization phase

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Velocity of Conduction of AP

• Velocity increases with increased diameter of
  axon.
• Velocity increases when membrane resistance
  increases (myelination!)

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Synaptic Transmission

• Presynaptic Membrane
• AP ? Ca2 channels opening ? Ca2 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 a generator or action potential.

http//mcb.berkeley.edu/courses/mcb136/topic/Tissu
e_Cells_Membranes/SlideSet3/AP20review_files/slid
e0012_image012.gif
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Response of Post-Synaptic Cell

• Response may be inhibitory or excitatory
  depending on the nature of postsynaptic cell (NOT
  Neurotransmitter!!)
• 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, Ca2 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 (motor end plate)
• Controlled by voluntary thought (motor cortex)

• Autonomic NS
• Acts on smooth muscle, glands, cardiac muscle
• 2 neurons post and preganglionic
• PreG ACh ?nACh
• Post G
• PNS ACh ? mACh
• SNS NE ? ? or ?
• Controlled by hypothalamus (involuntary)
• Associated w/ limbic system leads to emotionally
  linked response
• Ablation (cant respond to changes)

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Autonomic NS

• Sympathetic
• Cell bodies of postganglionic nerves are in
  ganglia near spinal cord
• Diffuse control (110 ratio of pre to postG
  fibers)
• Short preganglionic nerves (ACh ? nACh receptors)
• Long post ganglionic nerves (NE?? ?1,?2, ?1 and
  ?2)

• Parasympathetic
• Cell bodies of postganglionic nerves are in
  ganglia near organ
• Precise control (13 ratio of pre to postG
  fibers)
• Long preganglionic nerves (ACh ? nACh receptors)
• Short postganglionic nerves (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 to heart, brain and skeletal
  muscle
• Inhibits digestion
• Piloerection
• Gluconeogenesis and glycogenolysis (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 endplate skeletal muscle on the receiving
  end of nm junction
• End Plate Potential (EPP) generator potential
  of skeletal muscle
• ACh release is quantal (miniature end plate
  potential 0.4 mV)

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Organization and Structure of Muscle
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Classification of Muscle
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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

Epimysium, perimysium, and endomysium all come
together at the ends of muscles 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
Myoblasts
Myotubes
Re-Enter the Cell Cycle
Myofibers
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The SarcomereBasic Contractile Unit in Muscle
M line
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Myofilament Arrangements
A cross-section through the A Band/I Band
overlap shows the hexagonal array of thick and
thin myofilaments
When muscle contracts, the sarcomere shortens.
The I band and H Zone also shorten. But the
length of the A band remains the same.
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The Thick Myofilament
MHC 220,000 Daltons MLC 15 20,000 Daltons
Myosin Light Chains
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.
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• Thin myofilaments
• Actin core
• Tropomyosin
• Filamentous protein blocks myosin binding site on
  actin
• Troponin
• T attaches troponin complex to tropomyosin
• I along with tropomyosin inhibits myosin
  binding site on actin
• C binds free intracellular calcium to produce a
  conformational change 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 Actinin anchors thin myofilaments to the
  Z-line
• Beta Actinin determines length of thin
  filaments
• Myomesin binds titin, aligns thick filaments
  into hexagonal array
• Desmin cytoskeletal protein, connects adjacent
  sarcomeres
• C-, H-, and X- proteins form rings around thick
  filaments, maintains thick filament structure
  during contraction
• Cap-Z and tropomodulin associated with opposite
  ends of growing thin filaments, regulates length
• Dystrophin anchors actin filaments to
  sarcolemma, defective in MD
• Myotilin interacts with alpha actinin and
  Z-lines, sarcomeric organization

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Nerve Muscle Relation
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Some definitions

• Motor Unit
• Composed of an alpha motorneuron and all the
  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 motor endplate
  meet

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Size Principle of Motor Unit Recruitment
Input from CNS
Corticospinal Tract
Recruited Last Forceful Contractions
Recruited First Finesse Contractions
Spinal chord
Small Cell Body
Large Cell Body
Type II
Type I
few myofibers easily recruited
Two different motor units within the same myofiber
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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
No
at resting membrane potential
RyR Receptor
Ca
Ca
Ca
Ca
_
_
Ca
Ca
DHP Receptor
Ca


Calsequestrin
Ca
Ca
Ca
SR-Ca ATPase
ATP
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Excitation-Contraction CouplingContracting Muscle
Depolarized
RyR Receptor
Ca
Ca
Ca
Ca


Ca
Ca
DHP Receptor


Calsequestrin
Ca
Ca
SR-Ca ATPase
Ca
Ca
Ca
ATP
Ca
Crossbridge Formation
Sarcomeric Shortening
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Excitation-Contraction CouplingRelaxing Muscle
No
at resting membrane potential
RyR Receptor
Ca
Ca
Ca
Ca
_
_
Ca
Ca
DHP Receptor
Ca


Calsequestrin
Ca
Ca
Ca
SR-Ca ATPase
Ca
ADP Pi
Tension is longer than electrical or biochemical
events
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• Steps in excitation-contraction coupling
• Action Potential
• Depolarization of the T-Tubules - Causes
  conformational change in the DHPR - opens Ca2
  channels(Ryr) on sacroplasmic reticulum
• Ca2 released from SR into ICF
• Ca2 binds to Troponin C cooperatively - causes
  conformational change
• Tropomyosin is out of way
• Cross-bridge cycling
• Relaxation via Ca2 ATPase

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The Crossbridge Cycle
Crossbridge detachment
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Features of the Crossbridge Cycle

• CB cycle is repetitive
• CB cycle is asynchronous
• Tension is proportional to CB number
• Velocity is proportional to cycle rate
• Velocity is inversely proportional to load

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.
57
Sliding Filament Theory

• Describes the mechanism of muscle contraction
• Free energy from cleavage of MgATP induces a
  bend in myosin head from a 90 to 45 degree angle
• Actin filaments slide toward the H zone, pulling
  the Z lines inward
• Sarcomere shortens and muscle contracts
• This happens in a wave - not synchronous for each
  sarcomere

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Sample Question 1

• Lengths at rest
• A band 1.5 ?m
• I 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 ?m
• I band 1.0 ?m
• H zone 0.7 ?m
• What is the length of the
• a) sarcomere? 1.5 1.0 2.5 ?m
• b) thin filament? (2.5 0.7) / 2 0.9 ?m
• c) overlap? 1.5 0.7 0.8 ?m

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Sample Question 2

• Lengths at rest
• A band 1.5 ?m
• I band 1.0 ?m
• H zone 0.7 ?m
• Sarcomere 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 ?m
• I band 1.0 ?m
• H zone 0.7 ?m
• Sarcomere 2.5 ?m
• During contraction, the muscle shortens by 20.
  What is the length of the
• a) sarcomere? 2.5 0.5 2.0 ?m
• b) thick filament? 1.5 ?m (no change!)
• c) I band? 2.0 1.5 0.5 ?m
• d) H zone? 2.0 (2) x (0.9) 0.2 ?m
• e) overlap? 1.5 0.2 1.3 ?m

62
Length Tension Relationship

• Generation of tension in a muscle depends on its
  initial length
• Maximal tension can be developed at a sarcomeres
  optimal length, usually its resting length
• At the optimal length, a maximum number of
  cross-bridge sites are accessible to the actin
  molecules for binding and bending
• When a muscle is passively stretched, the thin
  filaments are pulled out and there are less actin
  sites available for cross-bridge binding,
  decreasing tension
• When a muscle is shorter than its optimal length,
  tension decreases because the thin filaments
  overlap and the thick filaments become forced
  against the Z-lines

63
Length vs. Tension

• AT OPTIMAL LENGTH
• - maximum of crossbridges
• gt OPTIMAL LENGTH
• - thin filaments pulled away and less room
  on actin for binding less tension
• lt OPTIMAL LENGTH
• - thin filaments overlap, thick filaments
  run into Z lines less tension

64
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

65
Elastic and Contractile Components

• 1) Contractile Component Responsible
• for Active Tension(proportional to of
  crossbridges that cycle)
• Parallel Elastic Component Responsible for
  Passive Tension
• Series Elastic Component Must be
• stretched in order to develop active
• tension

66
Modulation of Muscle Contraction
67
Summation

• Muscle force can be modulated by the frequency of
  stimulation
• Depends on active state and refractory period
• Skeletal muscle exhibits a long active state and
  a short refractory period
• Allows a second action potential long before the
  initial twitch response is complete
• Subsequent twitches build upon the one before,
  ultimately achieving a tetanus state

68
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.
69
Tetanus and Fatigue
Onset of Fatigue
1/sec
10/sec
50/sec
5/sec
Stimulation at low frequencies produces summation
of twitches and tetanus. 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
70
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.
71
Leverage

• Because muscles operate across joints, the force
  applied to move an object depends on the leverage
  factor
• LF Leverage arm / Distance from joint
• The farther away from the joint a muscle is
  inserted, the smaller the leverage factor and the
  easier it is to move an object (example door
  hinge)
• The closer a muscle is inserted to the joint, the
  larger the leverage factor (mechanical
  disadvantage), but the more maneuverable the
  object is

72
Preload, Afterload and the Latent
Period(influence on twitch force)
Preloaded with 10 kg
Afterloaded with 10 kg

• The latent period is
• prolonged 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.

Action Potential
Muscle Twitch
Muscle Twitch
Action Potential
Extent of Shortening
Extent of Shortening
12 msec latent period
8 msec latent period
Preloaded with 20 kg
Afterloaded with 20 kg
Action Potential
Action Potential
Muscle Twitch
Muscle Twitch
Extent of Shortening
Extent of Shortening
20 msec latent period
8 msec latent period
73
Load-Velocity Relationship
As load increases the velocity of shortening
decreases.
74
Sample Question 3

• A muscle which weighs 12 g and is 100 cm long is
  stimulated 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?

75
Sample Question 3

• A muscle which weighs 12 g and is 100 cm long is
  stimulated 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 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
  J
• Power 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

76
Rate of Onset of Energy Pathways
100
Aerobic Mechanisms
Anaerobic Glycolysis
Percent Capacity of Energy Generating System
Creatine Phosphate
10 sec.
30 sec.
2 min.
5 min.
Exercise Duration
77
Characteristics of Muscle Fiber Types
Biochemical Profile
Performance Profile
Fiber Type Glycolytic Oxidative
MHC-ATPase Fatigue Activity
Profile
Activity
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
The activity profile of the major muscle fiber
types matches the biochemical and contractile
profiles for these fiber types.
78
Anaerobic Threshold
60
100
80
45
Oxygen Consumption (ml/kg/min)
Blood Lactate (mg/dL)
60
Anaerobic Threshold
40
30
20
Untrained
Trained
Exercise Work Load
REST
79
Oxygen Debtoxygen debt and oxygen repayment are
equal
Oxygen Debt
Oxygen Repayment
Rate of Energy Expenditure
Oxygen Consumption
0
2
8
Time (minutes)
80
Parameters of Endurance Training
TCA Cycle Enzymes
Oxidative Potential of Fast Fibers
De-training
Training
Adaptive Ratio (Control/Trained)
Capillary Density
VO2 Max
Slow twitch fiber diameter
1
12
24
6
Time (months)
81
Efficiency Calculations

• A 70-kg individual does 20 pullups, lifting his
  body weight 1 meter each time. In doing so, he
  consumes 4 liters of O2. Baseline is 400 ml of
  O2/min. Total exercise time is 5 mins. What is
  his gross and net mechanical efficiency.
• 1 L O2 4.8 kcal
• 1 cal 4.186 J

82
Efficiency Calculations

• A 70-kg individual does 20 pullups, lifting his
  body weight 1 meter each time. In doing so, he
  consumes 4 liters of O2. Baseline is 400 ml of
  O2/min. Total exercise time is 5 mins. What is
  his gross and net mechanical 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

83
Efficiency Calculations

• A 70-kg individual does 20 pullups, lifting his
  body weight 1 meter each time. In doing so, he
  consumes 4 liters of O2. Baseline is 400 ml of
  O2/min. Total exercise time is 5 mins. What is
  his gross and net mechanical 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 kcal
• Net E (4 L 0.4 L x 5 min) x 4.8 kcal 9.6
  kcal

84
Efficiency Calculations

• A 70-kg individual does 20 pullups, lifting his
  body weight 1 meter each time. In doing so, he
  consumes 4 liters of O2. Baseline is 400 ml of
  O2/min. Total exercise time is 5 mins. What is
  his gross and net mechanical 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 kcal
• Net E (4 L 0.4 L x 5 min) x 4.8 kcal 9.6
  kcal
• Gross Efficiency W/E 3.3 kcal/19.2 kcal 17
• Net Efficiency 3.3/9.6 34

85
Fiber Types
86
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

87
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

88
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 chain kinase(MLCK)
• 3) Activated MLCK phosphorylates myosin, which
  can now form an break cross-bridges
• amount of cross-bridgestensionintracellular
  Ca2
• 4) Intracellular Ca2 decreases(b/c of SRs Ca2
  ATPase) and myosin is dephosphorylated by myosin
  light chain phosphatase(MLCP)
• Ratio of MLCKMLCP is main determinant of tension
  in smooth muscle

89
Practice Questions for Nerve/Muscle Physio Test

• 9/1/2004

90
Choose the correct sequence of events during
excitation/contraction coupling

• Action potential, calcium release, depolarization
  of the t-tubules, contraction, calcium re-uptake
• Action potential, depolarization of the
  t-tubules, calcium release, contraction, calcium
  re-uptake
• Action potential, depolarization of the
  t-tubules, calcium re-uptake, contraction,
  calcium release
• Action potential, calcium release, contraction,
  depolarization of the t-tubules, calcium
  re-uptake

91
Choose the correct sequence of events during
excitation/contraction coupling

• Action potential, calcium release, depolarization
  of the t-tubules, contraction, calcium re-uptake
• Action potential, depolarization of the
  t-tubules, calcium release, contraction, calcium
  re-uptake
• Action potential, depolarization of the
  t-tubules, calcium re-uptake, contraction,
  calcium release
• Action potential, calcium release, contraction,
  depolarization of the t-tubules, calcium
  re-uptake

92
At equilibrium the concentration of Na is 5 mM
inside the cell and 500 mM outside the cell.
What is the Na equilibrium potential for this
cell?

• 90 mV
• -90 mV
• 120 mV
• -120 mV
• 60 mV

93
At equilibrium the concentration of Na is 5 mM
inside the cell and 500 mM outside the cell.
What is the Na equilibrium potential for this
cell?

• 90 mV
• -90 mV
• 120 mV
• -120 mV
• 60 mV

94
According to the "size principle" which of the
following statements would be true?

• large motor units are recruited first but
  generate less force
• large motor units are recruited first and
  generate more force
• small motor units are recruited first and
  generate more force
• small motor units are recruited first but
  generate less force
• motor unit size and force production are not
  related so none of the above are true.

95
According to the "size principle" which of the
following statements would be true?

• large motor units are recruited first but
  generate less force
• large motor units are recruited first and
  generate more force
• small motor units are recruited first and
  generate more force
• small motor units are recruited first but
  generate less force
• motor unit size and force production are not
  related so none of the above are true.

96
According to the sliding filament theory, which
of the following occurs during a muscle
contraction

• The thin filaments pull the H zone to the center
  of the sarcomere.
• The Z lines pull the thick filaments in the
  overlapping region.
• The area of overlap between the thick and thin
  filaments increases, however the actual lengths
  of the thick and the thin filaments remain
  unchanged.
• The width of both the I band and the A band
  decreases while the H zone increases.

97
According to the sliding filament theory, which
of the following occurs during a muscle
contraction

• The thin filaments pull the H zone to the center
  of the sarcomere.
• The Z lines pull the thick filaments in the
  overlapping region.
• The area of overlap between the thick and thin
  filaments increases, however the actual lengths
  of the thick and the thin filaments remain
  unchanged.
• The width of both the I band and the A band
  decreases while the H zone increases.

98
Warming the blood supply to the hypothalamus
causes

• shivering.
• increased pulmonary circulation.
• piloerection.
• increased cutaneous circulation.
• increased mesenteric circulation.

99
Warming the blood supply to the hypothalamus
causes

• shivering.
• increased pulmonary circulation.
• piloerection.
• increased cutaneous circulation.
• increased mesenteric circulation.

100
Which of the following features are the same in
the sympathetic and parasympathetic nervous
system?

• Average length of preganglionic fibers.
• Average length of postganglionic fibers.
• Neurotransmitter in preganglionic fibers.
• Neurotransmitter in postganglionic fibers.

101
Which of the following features are the same in
the sympathetic and parasympathetic nervous
system?

• Average length of preganglionic fibers.
• Average length of postganglionic fibers.
• Neurotransmitter in preganglionic fibers.
• Neurotransmitter in postganglionic fibers.

102
The following data are given for a skeletal
muscle fiber 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?

• 1.20 um
• 1.60 um
• 1.76 um
• 2.08 um
• Cannot be determined from above data.

103

• H-zone 0.4 um
• Thin Filaments 0.8 um

104

• 0.8 0.8 0.4 2.0 um
• 2.0 x 80 1.6 um

105
The following data are given for a skeletal
muscle fiber 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?

• 1.20 um
• 1.60 um
• 1.76 um
• 2.08 um
• Cannot be determined from above data.

106
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