7 Synapses: CNS and NMJ Flashcards Preview

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Flashcards in 7 Synapses: CNS and NMJ Deck (34):
1

synapse def

point of contact between the terminals of one neuron and the target neuron

2

release of a chemical transmitter from the terminals of the presynaptic neuron occurs in response to ____ by an ____

depolarization by an AP

3

the _____ signal in the presynaptic nerve is converted into a ______ one in the postsynaptic nerve

electrical, chemical

4

quantum of transmitter is stored in

synaptic vesicles of the presynaptic nerve

5

vesicles are anchored at the

active zone

6

after the nerve is depolarized, this happens (4 steps)

voltage gated Ca2+ channels open in the active zone
Ca2+ enters near the vesicles
vesicle fusion and excytosis
release of transmitter (quantum)

7

probability that vesicles at CNS synapses will fuse and release is low and depends on (2 things)

1/ number of vesicles in active zone
2/ increase in Ca2+ ions in the vicinity of the vesicles (due to AP frequency - higher frequency leaves a little Ca2+ behind and it builds up)

8

Ca2+ ions are removed by (3 things)

1/ Na+/Ca2+ exchange (secondary active transport)
2/ primary active transport across the PM or into the SR (Ca2+ ATPase)
3/ uptake by mitochondria

9

transmitter action terminates when it gets too low. this happens by two mechanisms:

1/ reuptake
2/ breakdown of the transmitter

10

postsynaptic receptors bind ____

ligands (chemical signaling molecules)

11

agonist

a ligand that produces a response in the target cell when it binds to the receptor

12

antagonist

a ligand that binds to the receptor but does NOT produce a response

13

transducer

convert chemical signals into cellular responses (all receptors are this)

14

this is how the post synaptic receptor works

-ligand (receptor) binds to the channel on the extracellular domain
-ion channel opens
-ions flow in, down their electrochemical gradient
-transmitter dissociates from receptor and channel closes

15

post synaptic potential (PSP)

-created by the ionic current that flows through open post synaptic channels
-graded, localized
-spreads passively

16

2 excitatory transmitters

acetylcholine
L-glutamate

17

main excitatory transmitter in the CNS

L-glutamate

18

excitatory transmitter at the NMJ

acetylcholine

19

excitatory post synaptic potential (EPSP)

produced by an inward positive ion concentration
*depolarization*

20

how many EPSPs must sum together to fire APs?

hundreds or thousands

21

the NMJ is the simplest synapse meaning

one to one relay

22

excitatory synapse at NMJ includes

single AP
acetylcholine released
nicotinic receptors (b/c ligand gated)
(open when they bind 2 Ach molecules, also permeable to Na+ and K+ ions)

23

2 inhibitory transmitters in CNS

GABA
glycine

24

inhibitory transmitters do this

open ion channels that are permeable to chloride ions
chlorine goes in, membrane is hyperpolarized (super negative)
IPSP (inhibitory postsynaptic potential) created

25

inhibitory synapses are located on

proximal dendrites or cell body of target neuron

26

AMPA receptor

L-glutamate
allow Na+ and K+ ions to pass and set up fast EPSPs
*fast ionotropic signaling*

27

NMDA receptor

blocked by magnesium ions at RMP
once open, Na+, K+, and Ca2+ can get in
**Ca2+ coming in is special - has to do with long term potentiation, learning, and depression**

28

transmitters involved in GPCR signaling (4)

norepi
serotonin
dopamine
L-glutamate

29

peptide transmitters are stored in

large dense cored vesicles (LDCV)

30

kinesin

a motor protein that moves macromolecules along microtubules. these macromolecules are involved in synthesis and storage of small transmitter molecules.

31

denervation supersensitivity

upregulation of postsynaptic receptors following loss of presynaptic nerve due to damage; its a pathological change

32

desensitization

when receptors are exposed to high conc of agonist (transmitter) for an extended period of time and they become unresponsive

33

long term potentiation (LTP)

-when central synapses are activated strongly and the number of receptors expressed in the postsynaptic membrane is increased/upregulated (can persist for hours/days)
-increase in # AMPA receptors (upregulation) + phosphorylation of these receptors

34

long term depression

-when weakly activated central synapses show a down regulation of receptors that persists for hours or days
-at glutamatergic synapses
-dephosphorylation of AMPA receptors
-triggered by diff levels of intracellular calcium