Synapses Part 2

Question 1

Excitability of a Neuron Changes

in Response to: (3)

Answer 1

synaptic input
prolonged activation
changes in membrane permeability, ion concentration, other chemicals..

Question 2

Synaptic input (pre-and post-synaptic) (3)

Answer 2

A. Postsynaptic inhibition or excitation
B. Presynaptic inhibition
C. Presynaptic facilitation

Question 3

Presynaptic inhibition & Presynaptic facilitation are due to

Answer 3

axoaxonic synapses

Question 4

Prolonged Activation (3)

Answer 4

A. Synaptic fatigue
B. Long-term Potentiation (LTP)
C. Long-term Depression (LTD)

Question 5

Excitability of a Neuron Changes in Response

to

Answer 5

Synaptic Input

Question 6

Synapses on both the pre-synaptic

cell & post-synaptic cell will

Answer 6

modulate
the final effect (change in membrane
potential).

Question 7

Synapses on both the pre-synaptic
cell & post-synaptic cell will modulate
the final effect (change in membrane
potential) (3)

Answer 7

A. Post-synaptic Inhibition or
Excitation
B. Pre-synaptic inhibition
C. Pre-synaptic facilitation

Question 8

Axo-axonal synapses are responsible for (2)

Answer 8

presynaptic inhibition and facilitation

Question 9

When an inhibitory interneuron (red)
releases an inhibitory transmitter (ex.
GABA) on a postsynaptic neuron. This
produces an

Answer 9

IPSP that decreases the
potential of the postsynaptic neuron from
reaching threshold

Question 10

When an excitatory interneuron (green)
releases an excitatory transmitter (ex.
Glutamate) on a postsynaptic neuron. This
produces an

Answer 10

EPSP that increases the
potential of the postsynaptic neuron from
reaching threshold

Question 11

Withdrawal Reflex:

Answer 11

Initiated by activation of nociceptors
and leads to withdrawal of the affected limb away from
the painful stimulus (ex. lifting up foot when you step on
something sharp, opening mouth when you bite down
on your tongue, etc.).

Question 12

Presynaptic Inputs

Change

Answer 12

Action

Potentials

Question 13

Pre-synaptic Inhibition results from

Answer 13

axoaxonal synapses 
where neurons reduce transmitter 
release from the excitatory neuron 
and decreases the EPSP produced in 
the post-synaptic neuron

Question 14

Inhibition occurs due to
increased Cl–
conductance (reduces AP
size) which decreases the

Answer 14

Ca2+ entry and amount of

excitatory NT released

Question 15

Pre-synaptic Facilitation results from

Answer 15

axoaxonal synapses 
where neurons increase transmitter 
release from the excitatory neuron 
and increases the EPSP produced in 
the post-synaptic neuron.

Question 16

Facilitation occurs due to
increased AP time so
there is increased

Answer 16

Ca2+
entry and more NT is
released.

Question 17

Synaptic Fatigue

Answer 17

Each successive 
stimulus is identical, but 
the response is 
progressively smaller.
Due to a presynaptic 
change.

Question 18

LTP and LTD occur in response to

Answer 18

repetitive synaptic activity and

cause changes in synaptic strength that can last for days to weeks

Question 19

LTP

Answer 19

Enhanced stimulation of the post-synaptic neuron after a brief
period of rapidly repeated stimulation of the presynaptic neuron

Question 20

Glutamate (Glu) can bind to (2) receptors on

the post-synaptic neuron

Answer 20

AMPA and NMDA

Question 21

LTP is best studied at

Answer 21

Glutamate 
(Glu) synapses in the 
hippocampus (part of the Limbic 
System that is involved with 
learning and memory).

Question 22

LTD is the
opposite of LTP
as it decreases

Answer 22

synaptic strength

Question 23

Increase excitability (5)

Answer 23

 Hyperkalemia (up to 6 mM)
 Hypocalcemia
 Alkalosis
 Caffeine & theophylline
 Up-regulation of receptors

Question 24

Decrease excitability (8)

Answer 24

 Hyperkalemia (above 6 mM)
 Hypokalemia
 Hypercalcemia
 Acidosis (ex. Diabetic DKA)
 Anesthetics (ex. Lidocaine)
 Down-regulation of receptors
 Hypoxia
 Fatigue