Cellular Neurophysiology Flashcards
Action Potential (AP)
an electrical impulse that changes the permeability of a membrane
Transport proteins
(channels/carrier) facilitates ion movement across the plasma membrane
Chemical gradient (concentration gradient)
the energy provided by the difference in concentration across the plasma membrane
Electrochemical gradient
the energy associated with moving charged molecules across a plasma membrane - when a membrane potential exist
Nerst potential value
this tells us what the membrane potential is if one ion is in control
Resting Membrane Potential (RMP)
charge difference across the plasma membrane
Na+ / K+ ATPase
maintains the RMP by ensuring that K+ and Na+ does not reach equilibrium
Local potentials
changes in membrane potential of a cell neuron occurring at and nearby the part of the cell that is stimulated
axial resistance
How well a current can move through the cytoplasm
- bigger axon diameter, less axial resistance
Depolarisation
The change from a negative resting potential to a positive resting potential which is caused by the opening of sodium channels
- moves towards zero, more positive
Overshoot
anything that cause the membrane potential to pass across zero
repolarisation
the change from a positive resting potential back to a negative resting potential which is caused by the opening of potassium channels
- move away zero, become mor negative
Hyperpolarisation
An increase in the potential difference across a cell membrane, making it more negative than the resting membrane potential (>-70)
polarisation
when the outside of the cell is zero and the inside of the cell is -70 its polarised
threshold
Level of stimulation needed to trigger a neural impulse
absolute refractory period
time during which another action potential is impossible; limits maximal firing rate
relative refractory period
the period of time following an action potential, when it is possible, but difficult, for the neuron to fire a second action potential, due to the fact that the membrane is further from threshold potential (hyperpolarized)
afterhyperpolarisation (undershoot phase)
the hyperpolarizing phase of a neurons action potential where the cells membrane potential falls below the normal resting potential
regenerative
propagated without decreasing amplitude
How is RMP altered if threshold is not reach?
it occurs by changing the permeability of the membrane to a particular ion
conductance
the permeability and dricving force together
Permeability
dictated by number of channels in the membrane and how many of them are open
Activation gate
part of the voltage-gated Na+ channel that opens when the membrane voltage reaches threshold (value of depolarization)
selectivity filter
the part of an ion channel structure that determines which ions it can transport
inactivation gate
open at rest and closes relatively slowly after depolarization in a single step
electrical signaling
action potential
axon hillock
the only are where action potential is generated which is caused by the very high density of sodium voltage gated channels
exocytosis
release of substances out a cell by the fusion of a vesicle with the membrane
full fusion
vesicle collapses fully into the plasma membrane, retrieved through a clathrin-coated process
Kiss and run fusion
when a vesicle forms a fusion pore but does not fully fuse with the cell membrane
EPSP (excitatory postsynaptic potential)
a light depolarization of a postsynaptic cell, bringing the membrane potential of that cell closer to the threshold for an action potential
IPSP (inhibitory postsynaptic potential)
synaptic potential that makes a postsynaptic neuron less likely to generate an action potential
temporal summation
summation between EPSPs from the same input that occur close enough together in time
Spatial summation
summation between events that occurs close enough together in space from different inputs - still requires them to be close in time
endplate potential
the postsynaptic potential that occurs in the motor endplate in response to release of acetylcholine by the terminal button
long term potentiation
an increase in a synapse’s firing potential after brief, rapid stimulation. Believed to be a neural basis for learning and memory
Neurotransmitters
chemical signals that initiate actions
Glutamate
most prevalent excitatory neurotransmitters
- glutamate release allows excitation of post synaptic membrane to occur
GABA
most prevalent inhibitory neurotransmitter
- GABA being release at the post synaptic cell will going to get inhibitory (IPSP)
2 types of receptors
1) ionic receptors: ion channels opens which allows ion through
2) g protein
acetyl cholinesterase
Acetyl cholinesterase turns acetylcholine into acetyl coA which is then reuptake into the vesicles and recycled
synergy
an interaction between two different types of hormones which are combined together and this results in a greater effect than the sum of their separate effects
hormone targeting
they bind with specific proteins receptors inside or in the surface of the cell and specifically change the cell’s activities
upregulation
how likely it is to bind hormones to its receptors is dependent on the balance between the synthesis and degration
downregulation
degrade more of receptors than we synthesized, decrease number of receptors will decrease the sensitivity
intracellular receptors
these are lipid soluble so they can cross across the membrane, but as they not water soluble they can not float freely in a solution. These are receptors that detects hormones.
steroid hormone complex
activates primary responses in genes
- inhibits transition and induces synthesis of gene
Primary responses
turns on or shut off other responses and generate a whole lot of secondary gene transcription
Ligand gated ion channel
an integral membrane protein that contains a pore which allows the regulated flow of selected ions across the plasma membrane
ryanodine receptors
- a calcium channel
- responsible for calcium release from the intracellular store during the excitation contraction coupling in both cardiac and skeletal muscle
Kinase
- an enzyme which adds phosphates to other molecules
- anything that contains a kinase will be able to phosphorylate proteins and turn on channels
confirmational change
changing the charge in the amino acid will change the structure of the protein
