What I would like to learn: What I know: Regardingibruce/courses/EE3BB3_2011/EE3BB… · Muscle...

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Impulse Propagation

After a external stimulation occurs, a signal is sent from the sensorynerve cells to the connecting nerve cells and relayed up to the brain. Thissignal is sent by the opening and closing of ion channels.

How does the external stimulus initiate a signal?How are different senses distinguished?

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The skeletal muscle

The muscle structure (endomysium, perimysium, epimysium)Muscle contraction fibers (slow twitch, fast twitch)Myofibril structure (A band, sarcomere, H zone)Sliding filament theory (tropomyosin, troponin, actin, myosin)

More about the enzymes, their concentrations and their reactionsinvolved in producing the cross bridges in the sliding filament theoryDetermining the particular lengths of A band, H zone, and sarcomere(especially when it shortens)What Z lines are and their role in the sliding filament theoryThe bigger picture of how skeletal muscle works with other processessuch as the propagation of an action potential

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Electrophysiology used in language comprehension

Used in the measurement of electrical activity of neurons.Functional electrical stimulation helps in converting the thought processinto action

How the thought of words to carry out a particular action can stimulate theaction itself?How thoughts lead to openings of ion channels and stimulating an electriccurrent?How word comprehension is detected by the electrodes on the head, anda physical outcome in limb movement is possible due to FES?

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Bionic Arm receiving electric current from the brain

The action required to be carried out is first thought of. Impulsepropagation occurs along the nerves towards the bionic arm. The bionicarm has a controller (computer) that interprets these electric signals toproduce movement in the arm.

How efficiently is the electric potential in the nerves transmitted to thewires connected on the bionic arm?How is though in an individual's mind used to stimulate nerve impulses?How is redirecting the nerves from the amputated arm to the chest help inbetter propagation of electric current to the bionic arm?

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Functional Electrical Stimulation

In a person with a spinal cord injury, an artificial signal (using anelectrode) initiated in the nerve can cause a muscle twitch.

How the electrode performs as to cause excitation in the targeted tissueonly and not the surrounding tissue.The voltage-current relationship of the electrode.The efficacy of the electrodes in stimulating nerves and muscles(especially the cuff electrode).

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Membrane channels

Action potentials travel down axons due to membrane channels openingand closing, allowing sodium in and potassium out (due to theirconcentration gradients). The action is what allows electrical impulses toreach the desired destinations and stimulate muscle cells.

How exactly are these membrane channels activated to open and close?When a membrane channel "opens" or "closes" what is happening withinthe structure of the channel to cause this?If these membrane channels are what allow electrical impulses to travel,how are electrical impulses able to skip along a myelinated axon via thenodes of Ranvier rather than travel smoothly?

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Nerve's action potentials

A resting potential is -70mV. A temporal or spatialsummation causes Na+ channels to open, raising the membrane'spotential. K channels open to flush out potassium and lower thepotencial inside the membrane. This causes a wave ofdepolarazation.

This seems interesting and it looks quantitative so there might be somemathematical equations to go along with it. What will the speed of theaction potential be?In anatomy lectures it was mentioned that in myelinated axons the signalwas sped up by not polarizing the whole nerve, but only sections, therewere no other details given.

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Sensory Receptors

Hair cells in the organ of Corti are able to move in order to detect sound;and, in the semicircular canals, detect head movement.

How is the movement detected transformed into electrical impulses to beinterpreted by the brain?

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Electric potential at an atomic level

I understand the basic concepts and function of biopotentialmeasurement devices and their application.

But what are quantum level events of molecules to allow these electricpotentials to appear on the device. Basically, what is occurring in thebody as the current is passed through the tissue at an atomic level.

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Direct stimulation of nerves

We learned last term that we can directly electrically stimulate nerves.When this is done, the action potential is capable of traveling in bothdirections.

Normally refractory periods ensure that action potentials travel in onedirection. Are there any consequences in having a bi-directional actionpotential?

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Muscle control of ossicles in the ear

Skeletal muscles in the ear contract to keep the ossicles from vibratingtoo much

I was under the impression that skeletal muscle was under voluntarycontrol, but we have no control over those in the ear. Are there differenttypes of skeletal cells or do we just not have any voluntary nerve controlover certain skeletal muscles?

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Functional Electrical Stimulation with Respect to Limb Control

A stimulator is placed in the proper region inside the brain and thoughtprocesses are used to control limbs.

The stimulator is just placed in one region of the brain. If the signal keepsgetting released to the exact same region of the brain, how do we convertthought processes so that they can individually control specific regions ofthe limb?

If the FES is activated by brain activity, then why don't other thoughtprocesses we have through the day trigger the FES at the same time?

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Neurotransmission

Info is transported via electrical impulsesIon are what are used to transmit action potentialSome are myelinated and some are notMyelinated axons have much faster transmission speedsNeurotransmitters used to communicate

How exactly does an action potential jump across the myelin sheath ofthe nerve axon?How exactly transmissions that have multiple nerves involved coordinatedto keep transmission timed correctly (ex. movements that requiredmultiple muscle contraction)

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Bioelectric Potentials and Currents

How ions are used to help in propagation of impulses.The purpose of having a membrane potential, resting membrane potentialand gated ion channels, to help in impulse conduction.

How devices planted in the body can help stimulate impulses?How the presence of ions in the body fluid act as a medium for impulsepropagation?How bioelectric potentials are used for diagnostic purposes on skin,periosteum and bone?

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Action Potentials

- Action potentials are summed graded potentials (within a few ms andwithin a distance of a few microns) - action potential phases: resting, depolarizing, repolarizing,hyperpolarizing, and the events which take place within these phases (ie:which channels are opened and closed, direction of Na+ and K+ flow) - absolute refractory period: no action potential can be sent - relative refractory period: action potential can be sent, but it is verydifficult to do so

- What determines the rate at which a cell type is excited - which types of cells have excitable membranes? - What other ions are involved in action potentials, and what factorsinfluence this movement (Is it the same ratio and type of ions each time?)

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Functional Electrical Stimulation

- electrical stimulation causes an action potential in the nerves leading tomuscle contraction - it is easier to stimulate the nerves and not the muscle directly (lesscurrent is needed) - Why it is used and the applications (eg: various myopathies, in footdrop device) - main types: surface, percutaneous, implanted - main components: electrodes, leads, stimulators, sensors

- How is it that TENS units block pain with electrical stimulation, but donot cause muscle contraction? (Lower current?) - How is the technology altered to work in specific cases (eg for finerfacial movement and for larger limb movements - differences in current?) - If the muscles are not properly innervated and traditional FES will notwork, can the muscles still be stimulated directly, despite needing a largercurrent?

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Action Potential

It's an electrical signal that propagates along membrane of a neuron ormuscle fibreNerve action potential and muscle action potentialTwo phases depolarizing phase and repolarizing phase

The relationships between different neurons and their different thresholdfor generating action potentials.

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Impulse Propagation

When impulses are generated they must travel along axons to reach theirdestination. Multiple impulses cannot be sent along the same axon at thesame time as there must be a period of repolarization. The propagation iscaused through the use of an electrochemical gradient.

How are we able to control these the path along which these impulsespropagate.Can we simulate this impulse propagation ex vivo.What can be done to mimic impulse propagation in patients where thisdoes not occur properly.

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The neuromuscular junction

The action potential arrives at the pre-synaptic terminal causing Ca2+channels to open and Ca2+ ions to flow into the presynaptic neuron. Theinflux of Ca2+ ions causes the emptying of neurotransmitter into thesynaptic cleft. The transmitter then diffuses through the cleft and attachesto receptors on the post-synaptic membrane. This causes Na+ ions toflow in and K+ ions to flow out of the muscle membrane until they balanceout. This causes depolarization in the muscle membrane and causes anaction potential to propagate again.

How much amount of transmitter is released, the probability of releasingsites, failure sitesConcentrations of Ca2+, Na+ and K+Calculations of currents and voltages caused by depolarization in thepost-synaptic membrane

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Membrane Channels

An ion channel that allows the passive flow of ion

Is there any exception that ion flows against its gradient?What will happen if the transport protein does not work properly?

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Electrical Stimulation of Excitable Tissue

FES is used to stimulate nerves affected by paralysis

How to excite different layers of tissue with different densities usingcurrent sourceHow to isolate a region of simulation specific to movementPreparation needed to install an artificial stimulation system for differenttypes of tissues

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ECGs

For an ECG, electrodes are placed on the chest to detect changes inelectrical activity on the skin caused by the beating of the heart.

What specifically the ECG is measuring, and how the information fromeach electrode is compiled to create a single signal. What processesdoes the information from each electrode have to undergo to isolate theelectrical signal from the heart from the other electrical activity present onthe skin?

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Pacemaker cells

In first term anatomy, pacemaker cells are briefly mentioned as beingpresent in the heart, and they are said to contribute to involuntarycontraction of the heart.

Do these cells have other functions within the heart? How does this cellcreate electrical impulses and how does the electrical impulse propagatethrough cardiac muscle cells?

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Voltage Gated Ion Channels

When the potential difference across a membrane reaches a certainthreshold level, voltage gated ion channels open, allowing for chargedparticles to cross the membrane and cause an action potential.

How does the change in potential difference physically cause the voltagegate to open? How does this threshold differ based on different cells andcan we predict how a certain gate is going to respond to changes involtage?

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Extracellular Fields

It is the electrical potential fields produced by cells outside of the cell.

How clear are the signals produced by these fields?What are the limiting factors of equipment such as EEG, EMG and ECG?

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Neural Electrophysiology

It is the study of the electrical properties of biological cells and tissues.

How can these properties be manipulated for the propose of Biomedicalengineering?What techniques are used to measure the Voltage and Current intissues?

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Extracellular fluid in body cavities

Body fluid outside cellsA lot of waterHelp protect (as in surround organs so they are protected?)

What makes up extracellular fluid other than maybe sodium, potassium?Does it contain CSF?How much in an average person?

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neurons, signals

- neurons send signals when excited, and can inhibit or excite neurons atthe ends of their axons- afferent neurons connect the "inputs" to the "CPU", and efferentneurons connect the "CPU" to the "outputs"- neurons connect to each other in neural networks, i.e.: in series, inparallel, in loops, etc.

- to understand how neural networks work ("wiring")- how, from the structure of neural networks, emerges"calculations"/"processing", or what besides the structure (chemicals?)leads to such

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Neural activity and transmission

Impulses are carried down axons to other neurons by action potentials,and are carried across synapses by neurotransmitters.

Where do action potentials originate from? How and why do they start?

Each neuron is connected to thousands of other neurons, how do theneurotransmitters know which ones to send the information to? How dospecific messages get to the part of the brain that processes theinformation? (eg. how do messages regarding motor planning know howto get to the cerebellum?)

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Cochlear Implant and sound propagation to brain

The cochlear implant uses 8-20 electrodes that successfully replicatefunctionality of 12000 hair cells used by ear in sound recognition. (Thisalso gives hope to engineers making bionic eye that a 1000 electrodemicrochip would be able to sufficiently restore vision and allow for facialrecognition and reading).

How are so few electrodes in the cochlear implants able to take on thefunction of over 600 times the normal cells used by ear for soundrecognition? Are some of the sounds lost or missed by the people usingthese implants?

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Bionic eye and understanding of image by the brain

The Bionic eye operates with about 60 electrodes that perform thefunction of retinal cells but subjects are only able to see phosphenes andsome outlines of objects around them. Originally, the eye contains thelikes of 100 million electrodes (100 MP resolution).

How do electrodes (mechanical element) allow for replication of ganglioncells (biological element) and how the brain forms the image of whateverthe human eye and the bionic eye sees? Will there be a differencebetween the two sights?

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Artificial Limb using a cut up pectoralis major muscle.

When I was in grade 10 one of my teachers showed me a video of aperson missing their left arm and having a prosthetic arm that they wereable to control by using there pectoralis major muscle. The pectoralismuscle was cut up into different sections and each section had its ownhand movement. Here is a video similar to the one I sawhttp://www.youtube.com/watch?v=T6R5bm6qx2E

- Could you go over the technicalities that must be done to create such amedical instrument.- What is the future in this field

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Action Potential

- A large change in electric potential- Caused by multiple changes in electric potential in close proximity or inclose distance- Used in the nervous system to relay messages

- What causes the action potential to stop- Why in the action potential graph does the repolarization undershoot- How does the body produce a stimulus

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Cardiac Electrophysiology

Not much - judging from the name, and a briefresearch, it sounds like analyzing electrical activities in the heart.

How are heart arrhythmias accuratelymeasured in order to be properly treated. Is the procedure invasive ornon-invasive? In what cases are pacemakers required?

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Skeletal muscle

There are 3 types of fibers type I, type IIa and type Iib.They each have trade offs when it comes to fatigue resistance andcontraction time.

Can fibers change type or are they fixedat birth? Would the make up percentage of these fibers predispositionsomeone to be a better runner vs a sprinter or a weightlifter (is thereevidence of this in athletes).

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Neural Signal Transmission & Neural Interface design through Engineerin

The Neural Impulse system is an all or none system and is based onfrequency of impulses to detect various movements and feelings of thebody and signals are transmitted through neurons that may be myelinatedor not. The location of feeling is detected through the level of the spinalcord from where the signal goes to the brain.

How does the brain differentiate between all the feelings, sight, sound,pain, movement and even their intensities using only one kind of impulsetransmission mechanism? Is this system designable using electronicsand computers? (allowing for designing a perfect mechanical ear and eyeusing electrical components that can interface naturally with the humanbrain.)

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EMG (Electromyography) and Skeletal Muscle

EMG is used to analyze and record the activity of skeletal muscles.Electric potential of the muscle cells is analyzed during EMG.

The relationship between specific electric potentials and the size of themuscles.General working knowledge of EMG.

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Extracellular fluid (ECF)

ECF is fluid outside the body cells which includes interstitial fluid andplasma.ECF - 80% is interstitial fluid.

20% is plasma, which is the liquid portion of blood.There are many other extracellular fluids like lymph in the lymphaticvessels, CSF, etc.

How is the balance of the fluids (intracellular fluid and extracellular fluid)maintained between inside and outside of the cell.

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Ions

Sodium, potassium, calcium, chloride & proteins with partial charges allparticipate in some way to the membrane potentials

Why are the individual atoms used for their particular functions?(e.g., why is Ca2+ used for muscle contraction?)

What is the cause of the regular concentrations in intra and extra cellularspaces?(i.e., why is Na+ highest on the outside and K+ the highest on theinside?)

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Electrical Insulation

That the currents propagating through cardiac cells are confined to thespecific cells and are directed to muscle as action potential travels downthe conducting heart tissue.

In circuit theory, the current travels as a result of a difference in potential.

What stops the impulse from spreading out to areas that the AP isunwanted?

What drives the propagation of cardiac AP and how can it be modelledelectrically?

How do defibrillators perform the same function as cardiac pacemakercells?

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Functional Electrical Stimulation controlled by BCI

FES is applying electric current to tissue to support or replace functionthat has been lost in the neurologically impaired. I understand that BCIcan we used to control FES devices and they can be invasive ornon-invasive.

How are brain signals mapped in order to achieve this? How are somebrain waves attributed to muscle movement and some not? How differentare these brain waves in different people? Also how do theseelectromagnetic waves arise?

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Cardiac Electrophysiology

I know that there are desmosomes between cardiac muscle cells to betterconnect them together and gap junctions between them in order to allowfor passage of ions so that all the cells contract at the same time as acoordinated unit.

How and why exactly do these ions pass through these gap junctions?Are they specific to certain ions?

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Information transfer

Signals sent to muscles, sensory information sent from receptors, andvarious complex thoughts and processing in the brain are all sent asrelatively the same format in terms of electrical activity

What is the basis for information in electrical transfer?

How can useful data in the body be contained in simple impulses?

How is this data be "permanently" (at least in the sense that it is localizedto a region of the brain) stored in the brain for a period of time?

What I would like to learn: What I know: Regardingibruce/courses/EE3BB3_2011/EE3BB… · Muscle...

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