The Excitable Cell Flashcards
How are APs coded
frequency
Describe generation of an AP
all or nothing
Describe an AP
unit of size - fixed
What is the function of APs
travel along axons, in one direction
How are graded potentials coded
size
Describe graded potenitals
local signals that travel short distances, variable size
Which direction do graded potentials pass
can travel both ways
TRUE or FALSE - strength of stimulus affects strength of potential
True
What is the resting potential
when no potentials are produced
Describe the resting potential
negative - unequal distribution of charged molecules
What is charge of the resting membrane potential
-70mv ish
What physical forces control ion movements in solution
diffusion, electrical fields, ion movement
What does the nernst equation calculate
equilibrium potential for an ion
What channel is a key determinant of the resting potential
potassium channel
Why is the resting potential so important
required for functioning nervous system
What do ion pumps in membrane set up
ionic concentration gradient
Describe the effect of high intracellular Ca in neurons
toxic
Does calcium move in or out of neurons
out
What does the Goldman equation calculate
resting potential
What are the phases of an action potential
rising phase, overshoot, falling phase, undershoot
What are the majority of action potentials mediated by
changes in permeability for sodium
What are some action potentials mediated by
changes in permeability for calcium
When are APs mediated by changes in permeability for calcium important
developing nervous system
TRUE or FALSE - action potential propagation decreases along the axon
FALSE
When are all sodium channels closed
resting state
When do some of the sodium channels open
when membrane potential rises to -50mV
Describe permeability changes of the membrane at -50mV
permeability for sodium increases, permeability for potassium decreases
What does an influx of sodium cause
membrane depolarisation
What happens when sodium channels close
repolarisation
Describe permeability changes during repolarisation
permeability for potassium ions increase
When are most of the potassium channels open
resting state
describe the structure of voltage-gated sodium channels
complex proteins with 4 subunits
Describe domain 4 of voltage gated sodium channels
special domain - positively charged AAs
What is the function of domain 4 of voltage gated sodium channels
sense change in voltage
Name some poisons affecting the excitable cell
Tetraethlyammonium, lidocaine, tetrodotoxin
What is the effect of tetraethlyammonium on cells
blocks potassium channels
What is the effect of lidocaine on cells
blocks Na+ channels - local anaesthietic
What is the effect of tetrodotoxin on cells
blocks sodium channels
Describe the rising phase of an action potential
rapid depolarisation
What causes the rising phase of an action potential
influx of Na+ into neuron
What happens during the falling phase of an action potential
voltage gated Na+ channels close, voltage gated K+ channels open
What moves out of the neuron during the rising phase
K+
How come an action potential only moves in one direction
sodium channels on one side are inactive
What factors influence conduction velocity
myelination, diameter, permeability
What does myelination act to increase
membrane resistance, space constant
What is a disadvantage of myelination
high metabolic and volume cost
What process do the nodes of ranvier induce
saltatory conduction
When is myelination mainly used
long distances
What does the space constant define
membrane potential decay
Where are axon potentials generally generated?
axon hillock
What type of potential do dendrites have?
graded potentials
What does continuous stimulation of a neuron produce?
train of action potentials
What is stimulus potential encoded by ?
action potential frequency
What is a EPSP
excitatory post synaptic potential
What is the effect of an EPSP
depolarises the membrane
What is an IPSP
inhibitory post synaptic potential
what is the effect of an IPSP
hyper polarises the membrane
What is an IPSP a result of
activation of inhibitory receptors
What are ionotropic receptors permeable for
chloride
What are metabotropic receptors
GPCRs
What are ionotropic receptors
ligand gated ion channels
Which receptor is faster working - ionotropic or metabotropic
ionotropic
TRUE or FALSE - Graded potentials can summate
TRUE
