action resting potentials
DESCRIPTION
electronic insrumentationTRANSCRIPT
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Bio-Medical Instrumentation
Sources
Bio Chemical Cardiovascular Respiratory Nerves Measurement Systems -
Bio-Chemical
Energy to activate bodyWith Intake ofFood
Water
air
Support Messenger agent material forgrowth
repair of parts of body
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Cardiovascular
Closed Hydraulic system Four Valves Pump Heart connected to flexible/elastic tubing Blood VesselsFunctionTransportation of Oxygen , Co2
Heart drives blood 72 times/hr
Activities monitored by Electro - cardiography
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Respiratory
Pneumatic system Air pump Diaphragm create +ve and ve pressure in sealed chamber Thoractic cavity Cause air to be sucked and forced out Oxygen is taken into blood and Co2 is transferred from blood to air -
Nervous system
Communication network Brain is Central information processorMemory
Computational
Decision making
I/O Channel
Central Part-- Encephalon and Spinal cord Peripheral part- Nerves and group of nerves -
Brain
Cerebrum responsible forhearing
sight
touch
Volume muscle control
CerebellumIntercept sensors
Motor nerves
Smooth out , avoid jerking motions
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Bio-Medical Instrumentation
Involves Study of
Action PotentialBio- Potential electrodesRecording Systems
ECG,EEG,EMGExploratory Systems
X-Rays Machines, Ct Scanners, MRI and Ultrasonic Imaging Systems -
Nervous System
The brain communicates with the rest of the body through the spinal cord and the nerves.
Each nerve is a bundle of hundreds or thousands of neurons (nerve cells).
The spinal cord runs down a tunnel of holes in your backbone or spine.
The cord is a thick bundle of nerves, connecting your brain to the rest of your body.
Brain
Spinal Cord
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Nervous System
The nervous system is made up of nerve cells or neurons that are "wired" together throughout the body. Neurons carry messages in the form of an electrical impulses. The messages move from one neuron to another to keep the body functioning.
The axon of one neuron doesn't touch the dendrites of the next. Nerve signals have to jump across a tiny gap. To get across the gap they have to change from electrical signals into chemical signals then back into electrical signals.
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Action Potentials
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Resting Cell Membrane Potential
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The potential difference (70 mV) across the membrane of a resting neuronIt is generated by different concentrations of Na+, K+, Cl, and protein anions (A)Ionic differences are the consequence of:Differential permeability of the membrane to Na+ and K+Membrane Potential
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The outside (extracellular) face is positive, while the inside face is negativeThis difference in charge is the resting membrane potentialThe predominant extracellular ion is Na+The predominant intracellular ion is K+The sarcolemma is relatively impermeable to both ionsElectrical Conditions of a Polarized Sarcolemma
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Used to integrate, send, and receive informationMembrane potential changes are produced by:Changes in membrane permeability to ionsAlterations of ion concentrations across the membraneMembrane Potential Signals
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Depolarization
Initially, this is a local electrical event called end plate potentialLater, it ignites an action potential that spreads in all directions across the sarcolemmaThreshold critical level of stimulus -
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Action Potential
A transient depolarization event that includes polarity reversal of a sarcolemma (or nerve cell membrane) and the propagation of an action potential along the membrane -
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Application of voltage causes a patch of the sarcolemma to become permeable to Na+ (sodium channels open)Na+ enters the cell, and the resting potential is decreased (depolarization occurs)If the stimulus is strong enough, an action potential is initiatedDepolarization and Generation of the Action Potential
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Polarity reversal of the initial patch of sarcolemma changes the permeability of the adjacent patchVoltage-regulated Na+ channels now open in the adjacent patch causing it to depolarizeThus, the action potential travels rapidly along the sarcolemmaOnce initiated, the action potential is unstoppable, and ultimately results in the contraction of a musclePropagation of the Action Potential
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Repolarization Restores the resting electrical conditions of the neuronDoes not restore the resting ionic conditionsIonic redistribution back to resting conditions is restored by the sodium-potassium pump
Role of the Sodium-Potassium Pump -
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Repolarization
Immediately after the depolarization wave passes, the sarcolemma permeability changesNa+ channels close and K+ channels openK+ diffuses from the cell, restoring the electrical polarity of the sarcolemmaRepolarization occurs in the same direction as depolarization, and must occur before the muscle can be stimulated again The ionic concentration of the resting state is restored by the
Na+-K+ pump -
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Hyperpolarization
Occurs when membrane potential increasesInside of membrane becomes more negative -
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Phases of the Action Potential
1 resting state2 depolarization phase3 repolarization phase4-- hyperpolarization -
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Time from the opening of the Na+ activation gates until the closing of inactivation gates The absolute refractory period:Prevents the neuron from generating an action potentialEnsures that each action potential is separateEnforces one-way transmission of nerve impulsesAbsolute Refractory Period
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The interval following the absolute refractory period when:Sodium gates are closedPotassium gates are openRepolarization is occurringRelative Refractory Period
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Action Potential
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Membrane potential propagation
Action Potential 1 msRepolarisation 150 to 300msMuscle twitch 10 ms after repolarisation -
Graded potentials*
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Graded Potentials
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Graded Potential Action Potential
Short-lived, local changes in membrane potentialDecrease in intensity with distanceTheir magnitude varies directly with the strength of the stimulusSufficiently strong graded potentials can initiate action potentialsAction potentials are only generated by muscle cells and neuronsThey do not decrease in strength over distanceThey are the principal means of neural communicationAn action potential in the axon of a neuron is a nerve impulse -
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What if ..?
The amount of extracellular K+ were below normal?
Opening of the voltage-gated sodium channels were prevented?
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Extracellular K+ were below normal?
Stronger tendency of K+ to diffuse out Therefore more difficult to reach threshold and action potentialSigns and symptoms = muscle weakness, sluggish reflexes, -
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Extracellular Na were below normal
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Some of the Na channels which are normally closed will remain open Easier to reach threshold and action potentialSigns and Symptoms nervousness, muscle spasms tetany. -
Bio-potential Electrodes
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