lecture 12 modulation

Question 1

things that can cause synaptic strength to change

Answer 1

diseases (myasthenia gravis, startle disease)
drugs (therapeutic, recreational)
prior or ongoing activity (experience changes thoughts and actions by altering synaptic function

Question 2

what mechanisms lead to altered synaptic strength

Answer 2

addition or loss of synaptic connection
(can take hours to occur)

growth or shrinkage of synapse
(synaptic current directly proportional to number of open receptors)

rapid change in synaptic efficacy with no structural change
(no new proteins)

Question 3

how to measure synaptic strength between 2 neurons

Answer 3

1) stimulate axon with electricity
2) fires action potential
3) releases neurotransmitters
4) epsp detected by recording electrode in post synaptic cell

Question 4

how is facilitation different from temporal summation

Answer 4

facilitation piggybacks but the amplitude gets bigger every time and the second one starts after the first has gone back to rest (presynaptic because it relies on residual calcium)
vs
temporal summation where the epsps piggyback on top of each other and the next one starts before the first one has ended (postsynaptic because it relies on open lgic)

Question 5

spatial summation

Answer 5

several weaker signals from different locations vs temporal several weak signals from one source that add up

Question 6

facilitation increases quantal content why

Answer 6

the residual calcium hypothesis- ca enters to trigger neurotransmitter release then is removed
when second stimulus arrives soon after the first, new ca enters before the initial pulse is fully removed

Question 7

this causes smaller synaptic potentials with repetitive stimulation

Answer 7

short term depression

Question 8

ionotropic receptors

Answer 8

fast, ion channels

Question 9

metabotropic receptors

Answer 9

slower, ligand gated, can activate a g proteins

Question 10

g protein coupled receptors steps

Answer 10

1) binding of neurotransmitter to the extracellular receptor protein
2) activation of g proteins
3) activation of effector systems

Question 11

secondary messengers

Answer 11

the activated proteins are enzymes that generate small molecules (second messengers like cyclic amp)
camp activates protein kinase a (pka) which phosphorylates proteins by adding phosphate groups and changes the properties of the proteins so it can activate other proteins

Question 12

the 3 general second messenger systems that interact with specific g proteins

Answer 12

increases camp (gs)
decreases camp (gi/go)
stimulates phospholipase c, dag, ip3, pkc

Question 13

opiate receptors are…

Answer 13

GPCRs and the ligands are small peptides called enkephalins and endorphins

Question 14

pain modulation by opiate receptors

Answer 14

drg cells sense pain
spinal interneuron releases enkephalin
enkephalin binds GPCR
g protein (go) inhibits VGca channel
less neurotransmitter release when activated (weaker pain signals w opioid receptor activation)

Question 15

aplysia

Answer 15

giant sea slug that has simple nervous system and large neurons, stereotyped behaviors

Question 16

habituation

Answer 16

repetitive stimulation leads to decreased response

Question 17

what does habituation lead to

Answer 17

smaller epsps, decreased quantal content due to short term depression

Question 18

sensitization

Answer 18

intensified response after harmful stimulus

Question 19

Synaptic Strength

Answer 19

the average change in membrane potential of a postsynaptic neuron
elicited by a presynaptic action potential

Question 20

changes in strength or efficacy of neuronal connections. Can be
caused by a variety of physiologic and signaling mechanisms at time scales that vary from ms
to days or longer

Answer 20

Synaptic modulation

Question 21

Short-term plasticity

Answer 21

a change in synaptic
strength (time scale of milliseconds to
seconds) caused by presynaptic mechanisms
which alter the quantal content (average # of
vesicles released by one presynaptic action
potential

Question 22

Facilitation

Answer 22

increased synaptic strength
(EPSP amplitude) apparent after two or more
presynaptic action potentials. Caused by
elevation of residual Ca2+ in the presynaptic
termina

Question 23

Short-term depression

Answer 23

decreased synaptic
strength (EPSP amplitude) apparent after two
or more pre-synaptic action potentials.
Caused by depletion of vesicles from the
presynaptic terminal

Question 24

Ionotropic receptor

Answer 24

a neurotransmitter-gated ion channel which directly leads to changes in
membrane potential

Question 25

Metabotropic receptor

Answer 25

a neurotransmitter receptor that effects neuron excitability or
membrane potential indirectly through
intracellular signaling cascades

Question 26

Neuropeptides

Answer 26

large classification of
neurotransmitter molecules that are
made up of a short polypeptide chain.
Neuropeptides active GPCRs (see
below) for diverse effects on varying
timescales.

Question 27

G-protein coupled receptor (GPCR)

Answer 27

Type of metabotropic receptor with 7
transmembrane domains that interacts
with G proteins. GPCRs are a diverse
group with each subtype activated by
one of a variety of ligands (light,
specific neuropeptides, sugars, or
lipids)

Question 28

Second messenger

Answer 28

one of the intracellular signaling molecules that is activated by an
extracellular signal (i.e. activation of GPCR) and triggers a signaling cascade to alter a neuron’s
excitability or physiology

Question 29

Aplysia

Answer 29

a type of sea slug used as an experimental animal to study the molecular
underpinnings of behavioral learning or plasticity. A relatively simple circuit causes a reflexive
retraction of the gills when the animal’s siphon is touched. This response and the underlying
synaptic strengths can be modulated

Question 30

Habituation

Answer 30

a decrease in the
magnitude of behavioral responses to
repeated stimuli. In Aplysia, repeated
stimulation of the siphon causes a
reduced gill retraction after multiple
stimulations. This is due in part to a
decrease in the synaptic strength
between the sensory and motor
neurons

Question 31

Habituation

Answer 31

a decrease in the
magnitude of behavioral responses to
repeated stimuli. In Aplysia, repeated
stimulation of the siphon causes a
reduced gill retraction after multiple
stimulations. This is due in part to a
decrease in the synaptic strength
between the sensory and motor
neurons

Question 32

Sensitization

Answer 32

an increase in the
magnitude of a behavioral response to a
stimulus after a separate, often noxious
stimulus has been applied. In Aplysia,
pairing a shock to the tail with
stimulation of the siphon, causes a
increase in gill retraction when then
stimulating the siphon alone

Question 33

Heterosynaptic plasticity

Answer 33

when synaptic strength between two neurons maybe be regulated by a third neuron/synapse. (e.g.
sensitization in Aplysia)

Question 34

Know the mechanisms underlying synaptic facilitation and short-term depression and be
able to graph the effects of each on EPSPs

Question 35

Predict how changes in the presynaptic terminal and [Ca2+] affect the magnitude of the
EPSP

Question 36

Explain the differences between slow and fast synaptic responses, including any
advantages of slow, metabotropic signaling

Question 37

Diagram how a synapse can be purely modulatory including mechanisms that would either
increase (potentiate) or decrease (depress) a post synaptic response