Electricity Flashcards
what is the function of neurons?
to receve, modify and transmit signals quickly
how does the nervous system transport signals?
as rapidly changing voltages
what is charge
fundamental buidling block of electricity
all matter contains charged particles
what are the two components of charge?
protons and electrons
what are the biological charge carriers?
ions
what is an anion and cation
anion = negative charge (more electrons) cation = more positive (more protons)
what are the four main cations and the main anion
na, k, mg, ca
cl
what is current
net flow of charge
what is current in a nerve
the flow of ions
what are three factors which make ions flow
voltage and a conducting path
metabolic pump
chemical gradient/permeable membrane
what is the potential difference
the difference in field strength between 2 charged points in space
how do we generate a voltage
charge seperation generates the electric field and voltage is measure of field strnegth between these two points
what is the equation for electrical field force?
F=Qxe
what are the conditions for many ions flowing and not many ions flowing?
many = low resistance / high conductance low = high resistance/ low conductance
what is the equation for resistance and conductance
R=1/g
what is the ohms law equation
V=IR or V=Ig
describe current if we have a large resistance
smaller current flow
what are two key points about the conservation of charge and current
you cannot creat nor destroy net charge
the sum of currents ar a point in a circuit is zero
what are three things which capacitors do
store charge
slow down changes in voltage
introduce time into the electrical circuits
what is a conductor i neuron
cytoplasm and blood separated by lipid membrane (insulator)
what is the process of applying voltage to a capcacitor
charge flows into capacitor causing voltage to develop across it
charge flows until the voltage on capacitor= applied voltage
capacitor is now full so flow stops
amount of charge stored for a given V depends on the capacitance of capacitor
what is the equation for voltage, charge, and capacitance
Q=VC or C=e x A/d
what are two descriptors of passive conduction
response amplitude is proportional to different stimulus strengths
attenuates with distance
what are four descriptors of active conductio
response amplitude is constant with stimulus strength
response frequency is proportional to different stimulus strengths
no attentuation
finite conduction velocity
whats two advantages of active conduction
noise resistant
quite fast
whats two disadvantages of active conduction
indirect coding
limited dynamic range
what are two disadvantages of passive conduction
attenuation
noise
what are two advantages of passive conduction
direct coding
signals can be summated
what are the two types of summation?
spatial (inputs from seperate branches)
temporal(consequetive)
what are two modes of summation
excitatory (depolarise)
inhibitory(hyperpolarise)
