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Term IV: Neuro > Synapses & Signal Integration > Flashcards

Flashcards in Synapses & Signal Integration Deck (35):
1

What are boutons?

Specialized sites where neurons communicate by release of neurotransmitters

2

Small molecules that transmit impulses at chemical synapses

Neurotransmitters

3

Main excitatory neurotransmitter

Glutamate

4

Main inhibitor neurotransmitter

GABA

5

What are the three criteria for a neurotransmitter?

- Present in the nervous system in pre-synaptic terminals
- Released in response to pre-synaptic depolarization in a Ca2+ dependent manner
- Specific receptors exist for the transmitter on post-synaptic cells that generate a signal in the post-synaptic cell

6

What are the steps in synaptic transmission?

1. Action potential in nerve terminal opens Ca2+ channels
2. Ca2+ entry causes vesicle fusion and transmitter release
3. Receptor-channels open, Na+ enters post-synaptic cell and vesicles recycle

7

T or F. Under most conditions, membrane potential changes occur only with significant change in ion concentration.

FALSE - membrane potential changes occur with LITTLE change in ion concentration under most conditions

EXCEPTION: when Ca2+ channels are active, significant concentration changes do occur for intracellular Ca2+

8

Electrical signaling often results in a ____ influx to transduce the electrical signal into other biochemical signals.

Ca2+

9

Where are Ca2+ channels position in the pre-synaptic bouton?

Directly below the active zone

10

What machinery in the synapses is a target of bacterial toxins?

Fusion machinery

11

T or F. Vesicles are destroyed after releasing neurotransmitter.

FALSE - they are recycled and reused

12

What is channel gating?

Conformational changes that affect channel open probability

13

What are 4 common gating mechanisms?

1. Voltage-gated
2. Ligand-gated (extracellular molecule)
3. Signal-gated (intracellular molecule)

14

What are the main receptors found at excitatory synapses? What type of ion do they allow to pass through the channel?

Ionotrophic glutamate receptors

Cations

15

Opening of the glutamate receptor channel is near 0 mV so opening it drives membrane potential to _____ (depolarize/hyperpolarize)

Depolarize

16

_____ ensures that ionic currents will go to 0 if conductance is kept constant.

System attractor point

17

____ shift system attractor point toward channel's 0 current potential if conductance is _____ or away if conductance is _____

Channel conductance changes

Increasing

Decreasing

18

Are glutamate receptors open or closed at rest? Why?

Closed - because opening it requires a torqued conformation which is not energetically favorable

19

Ligand binding to glutamate receptors only stabilizes the _____ state (activated or closed)

Activated

20

Where is glycine primarily used as a neurotransmitter? Is it excitatory or inhibitory

Spinal cord - inhibitory

21

Excitatory sites primarily use ____ channels, while inhibitory sites primarily use ____ channels

Cation

Cl-

22

Where in the neuron are synaptic responses generated? Where are action potentials produced?

Dendrites

Soma and hillock

23

For sustained current injections, the signals decay exponentially with distance with a characteristic _______

Space Constant

24

For passive spread of signals in neurons, _____ membrane resistance and _____ axial resistance increase the space constant

Higher

Lower

25

For transient current injections, the signals decay even faster with distance due to _____

charging of the membrane capacitance

26

What are complicating factors for signal propagatino?

- Varying dendritic branch diameters
- Varying distance of inputs from the soma
- Voltage-gated channels that reshape basic synaptic responses

27

T or F. An action potential can be generated with a single synaptic event.

FALSE - many small synaptic events must sum together to reach threshold

28

Simultaneous stimulation of two connections

Spatial summation

29

Sub-linear summation

If two EPSP synaptic events occur together within an electrically overlapping compartment, then they will affect the currents being generated and summate in a sub-linear fashion

30

Linear summation

If EPSPs are generated in electrically distant compartments, then they will sum almost linearly since each generates independent currents that will reach the soma and work together to drive membrane depolarization

31

Repetitive stimulation of same connection

Temporal summation

32

What is rate limiting step for response termination?

Elimination of transmitters within synaptic cleft or for higher affinity receptors, neurotransmitter unbinding from receptor

33

Temporal summation is ____ (linear/sub-linear)

Sub-linear

34

If receptor population is overlapping, there will be competition between transmitters for the same receptors, producing ____(linear or sub-linear) summation.

Sub-linear

35

What are the three types of coordinated activity of excitatory and inhibitory synapses?

1. Feedback
2. Feed-forward
3. Lateral inhibition - winner take all