Bioinstrumentation/Biosensing Flashcards
Membrane potential
charge separation due to the unequal distribution of ions (can also be called voltage)
Active transport proteins
open temporarily in response to stimuli
Passive transport proteins
always open
Ion pump
transport protein that requires external energy
Electric field lines of an electric field
charges placed on an electric field line will move along it, attracted by one charge and repelled by the other (solid, curve towards midline)
Equipotential lines of an electric field
the charge in voltage along an equipotential line is zero
such lines are always perpendicular to the electric field lines
Trinity of an electric field
charge, electric field, potential difference
Equation for resting potential (Vm)
Vm = Vi - Vo which is about -60 mV
Vi is intracellular, Vo is extracellular
What are the two mechanisms of ion distribution?
Drift and diffusion
Describe drift (ion distribution)
motion of charge carriers due to force exerted by electric field
Describe diffusion (ion distribution)
process of particles distributing themselves from regions of high concentration to those of low concentration
Gibbs-Donnan Equilibrium
calculation of potential with two ions
charge neutrality condition -> total positive charges need to equal total negative charges
[X+]o/[X+]i = [X-]i/[X-]o
[X+]o[X-]o = [X+]i[X-]i
Dendrite
neurotransmitter receptor, responds to chemical stimulus and converts it to electricity
Synaptic junction
neurotransmitter producer, electric to chemical transduction
EEG stands for and description
electroencephalogram
electrophysiological brain activity recorded over scalp
Passive
Pacemaker cell
cells that create rhythmic electrical impulses that start at the sinoatrial/SA note -> atrial area -> ventricular area
Gap Junction
cell membrane protein that allows for direct passage of ions between adjacent cardiac muscle cells
ECC/EKG stands for
electrocardiogram, heart activity
Passive
V = IR
current (I) is the rate of flow of dc electrical charge, measured in amps
voltage (v) is the energy given to the charge carriers, measured in volts
resistance (r) is the opposition of a component to the movement of electrical charge, in ohms
Kirchhoffās Voltage Law
for a closed loop series path the algebraic sum of all voltages around any closed loop in a circuit is 0
conservation of energy
Kirchhoffās Current Law
total current entering a circuitās junction is equal to the total current leaving the same junction
conservation of charge
Ideal voltage source
a device that generates an exact output voltage which does not change regardless of the load current
Ideal current source
a device that generates an exact and constant current flow to a circuit regardless of the voltage
Short Circuit
two terminals of a circuit are externally connected with resistance equal to 0 and a voltage drop of 0
Open Circuit
two terminals of a circuit are externally disconnected, equivalent to current = 0
Electrical Impedance (3 parts)
the total opposition that a circuit presents to alternating current, including resistance (DC), inductive reactance, and capacitive reactance
Inductor and Inductive reactance
a device that stores energy in a magnetic field to preserve current
the impedance to AC in an inductor
Capacitor and capacitive reactance
a device that stores energy in an electric field to preserve voltage
the impedance to the flow of AC in a capacitor
Ideal Voltmeter (R=?)
used to measure voltage, should have resistance equal to infinity to block any current passing through the meter and altering the voltage drop of the device the voltmeter is measuring
Passive
Ideal Ammeter (R=?)
used to measure current, should have resistance = 0 to prevent adding additional resistance to the device the ammeter is measuring
Passive
Ideal Ohmmeter (R=?)
used to measure resistance, composed of a voltage source providing a known voltage, small internal resistance (so that current will not go to infinity if the resistance of the device is 0), and an ammeter
Vr = I (Rr + R)
Active
Ground
a point in a circuit chosen to be a reference point with v=0 (voltage is relative), can absorb charge
Earth Ground
a ground physically connected to earth via a conductive material
Common Ground
a ground-collection point that connects to the metal enclosure of an electrical device
Parallel resistance and the current division rule
a parallel circuit acts as current divider; current divides in all branches, and the voltage remains the same across them;
determines the current across the circuit impedance
Series resistance and the voltage division rule
voltage is divided but current is constant, the voltage across a resistor in a series circuit = value of that resistor times the total impressed voltage across the series elements divided by the total resistance of the series elements
V1 = V R1/(R1+R2)
Types of potential static mode (2)
chronoamperometry (DC)
voltammetry (AC)
Active
Potential static mode (provide/measure)
provide programmed voltage and measure corresponding current
Active
Types of galvanostatic (1)
chronopotentiometry
Active
Galvanostatic (provide/measure)
provide programmed current and measure associated voltage
Active
Impedimetric (not impedance) (provide/measure)
measure impedance with AC signal, provide voltage or current and measure associated current or voltage
Active
Potentiometric (provide/measure)
passive voltage measurement with no current (I=0)
Passive
Passive Modes: I = 0 (1)
potentiometric
Active Modes (I>0), Control V (5)
potential static voltammetry chronoampermetry amperometry impedimetric
Active Modes (I>0), Control I (2)
galvanostatic
impedimetric
Passive tests (4) Eā
EEG
ECG/EKG
EGG
EMG
EGG stands for
electrogastrogram, stomach muscles
Passive
EMG stands for
electromyogram, muscles
Passive
Active tests (3) - three letter acronyms
GSR
EDA
ICG
GSR stands for
galvonic skin responce, skin resistance
Active
EDA stands for
electrodermal activity, skin signals
Active
ICG stands for
impedance cardiography
Active
Displacement measurement
displacement is produced by a tensile force (ex: strain stress, pressure)
Strain gauge
flexible substrate with single resistor that bends with pressure, causing a change in resistance
can determine both magnitude and direction of force
Capacitive Sensor
measures compressive force by calculating the change in capacitance (the ability of a system to store an electric charge)
Q = C V
charge = capacitance * voltage
C = E * A/D
capacitance = electricity * (area of plates/thickness or gap)
increase in pressure lowers d and raises c
Two types of temperature sensors
termistors and thermocouples
Termistor
temperature sensitive transducers, resistance changes with the change in temperature
Thermocouples
temperature transducers formed by joining two metals with un= thermal expansion coefficients (bimorph) whose junctions produce an electromotive force when maintained at different temps, allowing the thermocouple to recognize a temperature difference
Ion-sensitive electrodes
composed of 2 half cells, a working electrode and a reference electrode
passive test of equilibrium potential, no current
working electrode is metal -> internal filling solution -> selective membrane (only develops variable potential in response to H+ ions) -> sample solution
reference electrode is sample solution -> liquid junction/salt bridge -> internal solution -> metal
voltmeter, uses E=Eo -(RT/zF) * Log [H+]
potentiometric, passive
Oxygen Sensor
amperometric (measurement is based on the production of a current when a voltage is applied between two electrodes)
uses O2 + 2H2O + 4e- (voltage) -> 4OH- + current
O2 reduced at negative chatode is directly proportional to current produced
electrodes are in electrolyte solution and surrounded by O2 permeable Teflon/polypropylene membrane
Active
Glucose Sensor
based on immobilized glucose oxidase
Glucose + O2 + H2O -> gluconic acid + H2O2
H2O2 -> 2H+ + O2 + 2E- (current)
Pulse oximeter
measure absorbance at two wavelengths, red (where HBO2 > Hb) and near infrared (about =)
photoplethysmographic signal caused by changes in arterial blood volume above resting
electric circuits seperate data into pulsatile (AC) and non-pulsatile (DC)
Fiber optic sensor
used to transmit light with minimal reduction
made of two concentric and transparent glass/plastic materials (center is core, outer is coating/cladding) whose different refractive indexs prevent light from escaping
made of optical fiber, sensing element -> immobilized analyte-specific luminophone, light source (exitate) and photodectector
Luminophore
part of a chemical that is responsible for luminescent properties
Luminescence
includes photoluminescence, fluorescense, chemilumescence
combined from chemical or EM
