Synapses

Question 1

Chemical Synapses involve…

Answer 1

neurotransmitters (NT) 
that are released from 
the presynaptic cell and 
bind receptors to excite, 
inhibit, or modify post-
synaptic cell.

Question 2

how many NT have been identified

Answer 2

> 100

Question 3

chemical synapse conduction

Answer 3

one way conduction

Question 4

what determines function?

Answer 4

the receptor, not the NT

Question 5

The — receptor subtypes are the largest known neurotransmitter-receptor family (– total receptor types).

Answer 5

serotonin

14

Question 6

Three Morphological Types of Chemical Synapses

Answer 6

axosomatic
axodendritic
axoaxonal

Question 7

Axosomatic synapses terminate on

Answer 7

neuronal cell bodies

Question 8

Axosomatic synapses tend to be

Answer 8

inhibitory

Question 9

axodendritic synapses terminate on

Answer 9

dendrites or dendritic spines

Question 10

axodendritic synapses tend to be

Answer 10

excitatory

Question 11

axoaxonal synapses terminate on

Answer 11

an axon, often close to synaptic terminals

Question 12

axoaxonal synapses modulate

Answer 12

the release of NT

Question 13

Presynaptic Events (4)

Answer 13

1. AP arrival at the synaptic terminal causes membrane depolarization
2. Voltage Gated Ca2+ channels open
3. Ca2+ enters the synaptic terminal
4. Exocytosis of vesicles filled with NT

Question 14

The amount of Ca2+ that enters dictates

Answer 14

the amount of NT released

Question 15

Synaptic delay of at least — between the pre-synaptic depolarization and post-synaptic response

Answer 15

0.5ms

Question 16

synaptic delay is due to (4)

Answer 16

time for calcium entry for exocytosis,
presynaptic neurotransmitter release,
diffusion in the synaptic cleft,
and postsynaptic receptor activation.

Question 17

Allows one to gauge the complexity of a reflex pathway (number of synapses) by looking at the

Answer 17

speed of the reflex

Question 18

Small molecules, rapidly-acting (3)

Answer 18

– Elicit acute responses.
– Final processing occurs in the axon terminal. Vesicles
are docked & ready for release from presynaptic terminal
– Ex: Acetylcholine, Norepinephrine, Dopamine, Serotonin (5-HT), Histamine, Glycine, GABA, Glutamate, Nitric Oxide (NO).

Question 19

Neuropeptides; larger molecules, slower (4)

Answer 19

– Effects are slower, more potent, & more prolonged.
– Produced in the cell body and transported down the
axon via axonal streaming.
– Fewer neuropeptides produced and released
– Ex: LH, ACTH, GH, vasopressin, oxytocin, angiotensin
II, substance P

Question 20

NT action is terminated by: (3)

Answer 20

• Re-uptake by the pre-synaptic membrane
• Absorption by glial cells
• Inactivation by enzymes in the synapse

Question 21

NT binds to receptor on

Answer 21

post-synaptic cell

Question 22

Ionotropic Receptors:

Answer 22

directly affect ion channels

Question 23

Binding of the ligand and the opening or closing the channel can: (4)

Answer 23

1. Change a cell’s membrane potential
2. Stimulate muscle contraction and/or relaxation
3. Stimulate secretion
4. Act as a second messenger to alter cellular activity

Question 24

Metabotropic Receptors:

Answer 24

G-protein coupled receptors

GPCR

Question 25

Nernst Potentials Na+ = Cl- = K+ =

Answer 25

``` Na+ = +61 mV Cl- = -69 mV K+ = -86 mV ```

Question 26

EPSPs due to (2)

Answer 26

* Opening Na+ channels | * Closing K+ and/or Cl- channels

Question 27

IPSPs due to (2)

Answer 27

* Opening Cl- channels | * Increased K+ conductance

Question 28

It is the --- that determines the response produced

Answer 28

specific receptor, not the NT,

Question 29

The 5-HT3 receptor

Answer 29

ligand-gated ion channel (Na+ and K+) that is proposed to be structurally similar to the nicotinic cholinergic receptor. The only 5-HT receptor that is not a GPCR.

Question 30

5HT1A,B response (2)

Answer 30

increase K+ conductance hyper polarization (produce IPSPs)

Question 31

5HT2A/5HT2C response

Answer 31

decrease K+ conductance due to channel closing (produce EPSP)

Question 32

5HT3 response (2)

Answer 32

gating of Na+, K+ due to channel opening \fast depolarization (produce EPSP)

Question 33

5HT4 response (2)

Answer 33

decrease K+ conductance due to channel closing slow depolarization (produce EPSP)

Question 34

Discharge of one pre-synaptic neuron cannot

Answer 34

``` reach threshold (+20 mV more positive than rest) ```

Question 35

The diameter of the soma is large causing almost no resistance to electric current flow through the soma, which allows for --- to occur

Answer 35

summation

Question 36

--- is almost always necessary to produce an AP

Answer 36

Summation

Question 37

two types of summation

Answer 37

spatial | temporal

Question 38

postsynaptic potentials last up to

Answer 38

15 ms

Question 39

SPATIAL summaiton

Answer 39

Simultaneous EPSPs or IPSPs from multiple pre-synaptic neurons (ex. Neuron 1 and Neuron 2). Added in SPACE.

Question 40

TEMPORAL summaiton

Answer 40

Successive EPSPs or IPSPs from a single presynaptic nerve terminal (ex. Neuron 1). Added in TIME.