Module 3: Lecture 6 Flashcards
what is an ionotropic receptor?
anytime we have a neurotransmitter triggering an ion channel to open and allow ions to flow
essentially
- respond to a ligand or a neurotransmitter binding to them to all ions to flow through them. they are a channel
- the receptor itself can be an ion channel DIRECTLY
what is a metabotropic receptor?
still respond to a ligand or a neurotransmitter binding to them but they are not an ion channel
- receptor can INDIRECTLY act on an ion channel
- it is a second messenger
what are the two types of subsynaptic receptors on the subsynaptic membrane?
- ionotropic receptors
- metabotropic receptors
what are ligand-gated channels/chemically gated ion channels?
- active or respond in response to a neurotransmitter or chemical or ligand binding
what determines if an excitatory or inhibitory synapses is created?
depending on what neurotransmitter is released and what receptor it binds to
what is an EPSP?
an excitatory postsynaptic potential
- a graded potential that will decrementally spread from the synapse by local current
what is an excitatory synapses?
the post-synaptic response to the neurotransmitter is a depolarization
- neurotransmitter is binding to an ion channel (ionotropic receptor) inducing depolarization
what is the net movement of excitatory synapses?
net movement of positive charges inside the cell
can the activation of ONE excitatory synapse lead to an action potential?
no, it is not sufficient to lead to an action potential (it can be as small as 0.5mV)
- HOWEVER, it brings the membrane closer to the threshold such that additional EPSPs could eventually trigger an action potential
what is an IPSP?
- inhibitory postsynaptic potential
- bringing cell further away from threshold potential
how can IPSPs hyperpolarize the membrane?
by increasing membrane permeability to K+ or Cl- because they want to move closer to their membrane potential (potassium will want to leave and chloride will want to enter, but making it more negative. both go down concentration gradient)
what is chlorides equilibrium potential?
-70mV
do all cells have active transport of Cl- into the cell?
no. SOME cells(neurons) have ACTIVE transport of Cl- into OR out of the cell
how would neurons do depolarize(EPSP) using chloride?
depolarize by exporting Cl- to ECF
what will passive diffusion of Cl- depend on?
its equilibrium potential relative to membrane potential (varies across types of neurons)
what does free movement of Cl- in the membrane do?
serves to stabilize membrane potential to help counter leak of other ions and decrease the likelihood of reaching threshold (an IPSP that ‘stabilizes’ the membrane potential like a break pedal/limit change in membrane potential)
what is the notion of synaptic delay?
the generation of the electrical signals, the chemical conversion to neurotransmitters actually being released and binding as well as regenerating that electrical signal in the postsynaptic neuron and it all takes time
- all these processes have to happen at every synapse
- the total sum of all those processes
- typically 0.5-1 msec for 1 synapse
what is determined by the sum of the synaptic delays?
total reaction time
as long as there is neurotransmitter within that synaptic cleft and its bound to these ion channels, these ion channels are?
going to remain active
if the unbound neurotransmitters are removed from the cleft, the number of occupied receptors will?
decrease
is there an equilibrium between a neurotransmitter that is bound to its receptor relative to the amount that is unbound?
yes
how do we remove the neurotransmitter in the synaptic cleft?
we degrade/remove the unbound neurotransmitter that’s floating in that synaptic cleft which will putt the equilibrium potential more towards the unbound form by degrading more towards the unbound form by degrading those unbound neurotransmitters
what is are the 3 mechanisms that are used to remove the unbound neurotransmitter?
- reuptake
- diffuse away from the receptor site and the cleft
- enzymatically transformed into inactive substances (and eventually recycles into the presynaptic axon terminal)
what is a reuptake?
unbound neurotransmitters are actively transported back into the presynaptic axon terminal
