Signaling Flashcards
What are cations vs anions?
positive vs negative ions
What are the two types of diffusion gradients?
concentration gradient (move based on concentration), voltage gradient (move based on charge)
What is equilibrium potential?
when the concentration gradients equals the voltage gradient
What is the resting potential of a neuron?
the electrical charge across the cell membrane in the absence of stimulation (about -70mV on inside)
What particles help produce the resting potential? Where do they have a higher concentration?
Na+ and Cl- have a higher concentration outside the axon
K+ and A- (large proteins) have a higher concentration inside the axon
What three features contribute to the resting potential?
- membrane is mostly impermeable to large molecules the A- proteins will remain inside the cell
- ungated K+ and Cl- channels allow them to pass freely but gated Na+ channels keep them out
- Na+ - K+ pumps remove Na+ and take in K+
How much potassium is taken into cell through pump versus how much sodium is taken out?
2 K+ taken in and 3 Na+ sent out
What is an action potential?
a large, brief reversal in polarity of an axon
What is the threshold potential?
the level that the membrane potential must reach in order for an action potential to happen (-50-55mV)
How does an action potential happen?
Na+ enters the cell and K+ leaves the cell, this results in an action potential from the summed voltage changes
How can the voltage activated Na+ and K+ channels be blocked?
tea blocks K+ channels and ttx blocks sodium channels
Which voltage activated channel open faster? Which stay open longer?
sodium opens faster but potassium stays open longer
How many gates do sodium channels have?
2, one closes once the membrane depolarizes to +30mV
What does epsp vs ipsp stand for?
excitatory postsynaptic potential vs inhibitory postsynaptic potential
What channels are excitatory/inhibitory postsynaptic potentials usually associated with?
excitatory is w/sodium
inhibitory is w/potassium and chloride
How can EPSP and IPSP be summed?
temporal (rapid weak pulses from same place), spatial (signals from multiple presynaptic neurons being received by one postsynaptic neuron)
What do EPSP do?
brief depolarization of neuron membrane in response to stimulation, makes it more likely to produce an action potential
What do IPSP do?
brief hyperpolarization of neuron membrane in response to stimulation, less likely to produce action potential
What is saltatory conduction?
where nerve impulses move down a myelinated axon and excitement occurs only at the nodes of ranvier
What channels are responsible for the frequency of action potential?
sodium and potassium
What is the absolute refractory period?
the state an axon is in in the repolarizing period, new action potential cannot be made, sodium gate 2 is closed (not voltage activated)
What is the relative refractory period?
state of axon in the later phase of an action potential, a stronger electrical current is required to produce another action potential, potassium channels are still open
Do synapses use electrical or chemical signalling?
Usually chemical
What is storage granules?
stores synaptic vesicles in the presynaptic neuron
What are the 5 steps in anterograde synaptic transmission?
- synthesis of neurotransmitter
- packaging and storing at axon terminal
- transportation to presynaptic membrane and releasing into cleft
- bidning/activating receptors on postsynaptic membrane
- degradation/removal
What does anterograde synaptic transmission mean?
sending message forward using neurotransmitters
How are neurotransmitters made?
in axon terminal (building blocks from food are used)
in cell body (instructions from DNA, transported by microtubules)
What triggers neurotransmitters to be released?
at terminal, action potential opens the voltage gated calcium channels, Ca2+ enters the terminal and binds to calmodulin, the complex this makes causes some vesicles to empty into the synapse and others get ready to
What are the types of receptors that can be found on the post synaptic terminal?
transmitter-activated receptors, ionotropic receptors, metabotropic receptors, autoreceptor, quantum
What are the ways neurotransmitters are inactivated?
diffusion(drifts away from cleft), degradation(changes shape), reuptake(taken back into terminal that released), astrocyte uptake (astrocytes take up them)