S2 Neuro Exam 1: Synaptic Transmission 1

Front 1

Describe electrical synapses

Back 1

-ionic currents
- cytoplasmic continuity (gap jxns)
-rapid bidirectional transmission
-electrotonic transmission

(membrane modifications btwn adjacent cells,
common btwn astrocytes & in neurons)

Front 2

How do astrocytes use gap junctions?

Back 2

-to form syncytium, compartment around & w/i groups of neurons
-involved in removal of excess K+ from ECF, pH regulation, & Ca2+ waves= modulate synaptic environment

Front 3

How do intracellular channels promote localized tissue homeostasis?

Back 3

-maintain electrical potential diff
-buffer differences in secondar messengers & small molecules (Ca2+ & ATP)
-nutrient transport

Front 4

How do intercellular channels regulate signal transmission?

Back 4

-propagate electrical signals btwn cells
-cellular differentiation in embryonic tissues

Front 5

How do intercellular channels maintain cellular organization?

Back 5

-compartmentalization of cell groups
-amplification or gain control of cell group responses
-coordinate rhythmic drive (neurons) w/ oscillatory activity

Front 6

Describe chemical synapses

Back 6

-use neurotransmitters
-cells separated by synaptic cleft (not cytoplasm)
-slow unidirectional transmission
-complex process of excitatory/inhibitory signal amplification

Front 7

3 components of chemical synapse:

Back 7

1. presynaptic element
(axon terminal/bouton)
2. synaptic cleft
3. postsynaptic element
(postsynaptic density)

Front 8

Within the cell membrane of the axon terminal, the _________ contains high concentration of voltage gated calcium channels

Back 8

active zones

Front 9

What are the 3 main types of synaptic vesicles?

Back 9

1. Small clear
(glutamate, GABA, ACh)

2. small/medium spherical dense-core
(catecholamines, serotonin)

3. large spherical dense-core
(neuropeptides- SP, Enk)

Front 10

Differentiate btwn the vesicles containing glutamate & GABA

Back 10

glutamate- small spherical, clear vesicles

GABA- small flattened, clear vesicles

Front 11

The _____________________, within the postsynaptic element. contains Ca2+/calmodulin -dpendent protein kinase II channels and MAGUK & PSD95 proteins

Back 11

postsynaptic density

Front 12

What are the 3 common types of synaptic linkages in the CNS?

Back 12

1. axodendritic
axon terminals contact dendrite/dendritic spine

2. axosomatic
axon terminal contacts soma

3. axoaxonic
axon terminal contacts another axon

Front 13

(neuropeptides/classical neurotransmitters) are transported in secretory vesicles from the golgi apparatus w/i the soma to axon terminal
(fast axonal transport)

Back 13

neuropeptides

Front 14

(neuropeptides/classical neurotransmitters) are synthesized in the axon terminal & loaded into vesicles arriving from the soma

Back 14

classical neurotransmitters

Front 15

Describe the role of calcium in vesicle release

Back 15

1. AP depolarizes membrane , opening voltage gated Ca2+ channels
2. Ca2+ enters terminal, & binds to synaptogamin
3. Synaptogamin promotes membrane fusion & neurotransmitter exocytosis

Front 16

(SNARE hypothesis)
Vesicles containing _____________ bind to specific target membrane proteins, ______________. The formation of the ______ leads to membrane fusion.

Back 16

SNARE proteins/v-SNAREs (snaptobrevin/VAMP)

t-SNAREs (SNAP-25 & syntaxin)

SNARE complex

Front 17

(SNARE hypothesis)
During docking, ____________ is recruited to the SNARE complex, & acts as a calcium sensor.

Back 17

synaptotagmin

Front 18

During calcium influx, how does synaptogamin regulate neurotransmitter release?

Back 18

Synaptotagmin has 2 low-affinity calcium binding domains (C2A & C2B). When bound, acts as a positive regulator of neurotransmitter release, promoting vesicle fusion & exocytosis.

Front 19

Once neurotransmitters have been released, the SNARE complex is disassembled via _____ & _______.

Which of these is an ATPase that liberates energy to unravel complex?

Back 19

NSF & SNAP (soluble cytoplasmic proteins)


NSF

Front 20

What are 2 ways for vesicles to be recycled?

Back 20

1. endocytosis & formation of clathrin-coated vesicles
2. kiss and run- detached after fusion

Front 21

How are neurotransmitters removed after use?

Back 21

1. inactivation
destroyed or modified
2. reuptake
via transporter proteins (endocytosis)

Front 22

What defines the response that a cell will have to a released neurotransmitter?

Back 22

the receptor on the neuron

*receptor diversity allows the same neurotransmitter to serve multiple functions

Front 23

How do receptors on neuroglial cells control synaptic environment?

Back 23

-inactivation & recycling
-balance of ions

Front 24

Classify receptors based on function

Back 24

-Ligated channels, open/close transmembrane pores/channels
-G-protein coupled/2nd messenger
-transmembrane receptors w/ modified enzyme activity
-ligand-dependent regulators of nuclear transcription
-sequestration of intracellular ions (Ca2+)

Front 25

_______ are involved in sensory transduction, postsynaptic responses (EPSPs, IPSPs)

Back 25

local potentials

(graded, subthreshold, proportional to intensity)

Front 26

Describe Battery in relation to the neuronal membrane

Back 26

built into membrane
concentration gradient creates voltage (Vm)

Front 27

Describe Resisitance in relation to the neuronal membrane

Back 27

resists charge movement
membrane channels (Rm)
cytoplasm (Ri)
ECF (Ro)

Front 28

Describe Capacitance in relation to the neuronal membrane

Back 28

ability to store charge
2 conductors separated by non-conductor/insulator (Cm)

Front 29

Speed in which voltage changes across the membrane is determined by its ____________ & ______________

Back 29

capacitance & resistance

Front 30

What does the time constant (t) represent?

Back 30

t= Rm x Cm

-the time it takes for passive voltage to reach 63% Vmax

*fewer channels open = longer time

Front 31

Current flow in the neurite & change in potential (increases/diminishes) w/ distance from origin

Back 31

diminished

*increase Rm
*decrease Ri

Front 32

What does the ration Rm/Ri determine?

Back 32

the distance that change in membrane potential is passively transmitted

Front 33

Neurons with greater t (time constant) have (greater/lesser) capacity for temporal summation

Back 33

greater

*consecutive synaptic potential at same site add together (temporal summation)

Front 34

Neurons with (greater/lesser) sigma allows for signal to reach trigger zone with less decrement

Back 34

greater

*synaptic potentials from diff inputs in same area summate (spatial summation)

Front 35

__________ synapses have greater influence on AP generation due to their proximity to the initial segment

Back 35

axosomatic

Front 36

When is inhibitory shunting most effective?

Back 36

When in close proximity to initial segment

*significant inhibitory inputs in CNS often occurs on neuronal cell body

Front 37

Where do the bulk of excitatory neuronal inputs in the CNS terminate?

Back 37

on dendritic spines