Chemical vs. Electrical Synapses

Question 1

electrical synapses (gap junctions)

Answer 1

two cells joined by connexins, which allow ions and other small molecules to flow through bidirectionally
many connexins = one connexon; two connexons from neighboring cells join to form gap junction

Question 2

chemical synapses

Answer 2

neurotransmitter released from presynaptic cell activates postsynaptic receptors

Question 3

postsynaptic potnetial (PSP)

Answer 3

change in membrane potential in postsynaptic cell
excitatory PSP (EPSP): getting neuron closer to threshold
inhibitory PSP (IPSP): keep the cell from reaching threshold

Question 4

benefits of electrical synapse

Answer 4

faster, lower energy, synchronization, reliable (hard to interfere with)

Question 5

benefits of chemical synapse

Answer 5

more controlled direction, more variety of signals (NT types), can turn an excitatory signal into an inhibitory one, plasticity (can increase or decrease the magnitude of a signal)

Question 6

sending a chemical signal

Answer 6

neurotransmitters are contained in vesicles, voltage gated Ca2+ channels let Ca2+ into the axon terminal, Ca2+ triggers exocytosis, vesicles fuse with the presynaptic membrane, neurotransmitter binds to ligand gated ion channels in the post synaptic membrane, neurotransmitter opens the channels to allow K+ to rush out and Na+ to rush in

Question 7

SNARE proteins

Answer 7

on plasma membrane of neurons and vesicles, coordinate the exocytosis of synaptic vesicles upon Ca2+ entry

Question 8

intro to neurotransmitters

Answer 8

glutamate: major excitatory NT in the brain
GABA: major inhibitory NT in the brain

Question 9

types of receptors

Answer 9

transmitter-gated (ionotropic): NT binding opens a channel in the receptor to allow ions to flow through to generate an IPSP or EPSP
metabotropic: NT binding activated a second messenger signaling cascade

Question 10

total current

Answer 10

Itotal= INa + IKa

Question 11

Iion

Answer 11

Ion = gion (Vm - Eion)
gion = conductance: how much an ion is allowed to flow through channel
Vm - Eion = DFion: how much ions want to move

Question 12

AMPA receptor

Answer 12

DFNa > DFK

INa > IK

Question 13

reversal potential (Erev)

Answer 13

property of individual channels, the membrane potential at which the current through the channel is equal to zero, helps us know which way current will flow, for single ion calculate using Nerst, for many ions calculate using Goldman’s, PSPs often never reach Erev because channels close

Question 14

receptor antagonist

Answer 14

drug that blocks the NT activation of a receptor

Question 15

receptor agonist

Answer 15

drug that activates a receptor without NT present

Question 16

how could you tell the difference between a chemical and electrical synapse?

Answer 16

antagonist will only affect chemical synapses. electrical synapses are significantly faster. bidirectional signaling (that doesnt reach threshold). change from excitation in one cell to inhibition in the next. elimination of Ca2+ would affect chemical synapses