Lecture 5

Question 1

What is synaptic transmission?

Answer 1

Transfers information at a synapse
- named by Charles Sherrington

Question 2

What’s the direction of information transfer?

Answer 2

Neuron to target cell
- Presynaptic neuron to postsynaptic neuron

Question 3

What are the 2 types of synapses?

Answer 3

Electrical and Chemical Synapses

Question 4

What are gap junctions made of?

Answer 4

connexin proteins formed by 6 connexins

Question 5

What are cells electrically coupled?

Answer 5

flow of ions from cytoplasm of one cell to the cytoplasm of another cell

Question 6

How do electrical synapses differ from chemical ones?

Answer 6

• bidirectional
• fast transmission (postsynaptic potentials)
• multiple PSPs occur at the same time to excite a neuron (cause action potential)

Question 7

What are the 5 synaptic arrangements in the CNS?

Answer 7

• axodendritic: axon to dendrite
• axosomatic: axon to cell body
• axoaxonic: axon to axon
• axospinous: axon to dendritic spine
• dendrodenritic: dendrite to dendrite

Question 8

What is Gray’s type I morphology?

Answer 8

asymmetrical, excitatory synapses
- Glutamate neurotransmitterW

Question 9

What is Gray’s type II morphology?

Answer 9

symmetrical, inhibitory synapses
- GABA or glycine neurotransmitter

Question 10

What’s the purpose of the neuromuscular junction?

Answer 10

studies of this established the principles of synaptic transmission

Question 11

What is the neuromuscular junction made of?

Answer 11

junctional folds with numerous neurotransmitter receptors

Question 12

How do chemical synaptic transmissions work?

Answer 12

1) Neurotransmitter synthesis
2) Load neurotransmitter into synaptic vesicles
3) Vesicles fuse to presynaptic terminal
4) neurotransmitter spills into synaptic cleft
5) Binds to postsynaptic receptors
6) Biochemical/electrical response elicited in postsynaptic cell
7) removal of neurotransmitter from synaptic cleft

Question 13

What are the 3 groups of neurotransmitters with an example?

Answer 13

Amino acids: small organic molecules - vesicle (GABA)
Amines: small organic molecules - vesicles (dopamine)
Peptides: short amino acid chains - secretory granules (dynorphin)

Question 14

What are secretory granules made of?

Answer 14

peptide neurotransmitter at the soma by the rough ER (golgi apparatus pathway)
- sent to presynaptic sites by microtubule transport

Question 15

What do synaptic vesicles require?

Answer 15

Neurotransmitter synthesizing enzyme and vesicular neurotransmitter transport protein

Question 16

What is docking of synaptic vesicles mediated by?

Answer 16

v-SNARES and t-SNARES proteins

Question 17

What causes exocytosis?

Answer 17

Increase in intracellular calcium
Ca++ binds to calcium sensor proteins (Synaptotagmin) and alters conformation of SNARE complexes, triggering vesicle membrane incorporation into presynaptic membrane
Neurotransmitter released into cleft
Vesicle membrane recovered by endocytosis

Question 18

What are examples of neurotransmitter receptors?

Answer 18

Transmitter-gated ion channels
Metabotropic Receptors
G-protein coupled receptors

Question 19

Contrasts EPSP and IPSP.

Answer 19

EPSP = Excitatory Post-Synaptic Potential
- transient postsynaptic membrane depolarization caused by presynaptic release of neurotransmitter
- EPSPs added together to produce significant, postsynaptic depolarization
- Threshold can be reached to fire action potential after integration

IPSP = Inhibitory Post-Synaptic Potential
- Transient hyperpolarization of postsynaptic membrane potential caused by presynaptic release of neurotransmitter

Question 20

What causes generation of an EPSP?

Answer 20

Neurotransmitter (usually glutamate) and Glutamate ion channels like AMPA, NMDA

Question 21

How do you quantitatively measure EPSPs?

Answer 21

Synaptic vesicles: elementary units of synaptic transmission
Quantum: invisible unit
Quantal analysis: used to determine number of vesicles that release during neurotransmission

Question 22

What are some important dendritic properties?

Answer 22

Many have voltage gated channels
They contribute to more complex integrative properties
Membrane depolarization falls off exponentially with increasing distance along a dendrite

Question 23

How do different EPSP summations affect the graph?

Answer 23

Spatial summation = high peak on action potential
Temporal summation = little bumps upwards

Question 24

What’s the point of EPSP summation?

Answer 24

allows for neurons to perform sophisticated computations

Question 25

How do excitatory and inhibitory synapses differ?

Answer 25

They bind different neurotransmitters, allowing different ions to pass through channels

Question 26

When will IPSP have hyperpolarizing effect?

Answer 26

when membrane potential is less negative than -65 mV

Question 27

What is shunting inhibition?

Answer 27

Synapse inhibits current flow from soma to axon hillock

Question 28

What are autoreceptors?

Answer 28

Presynaptic receptors sensitive to the neurotransmitter released by the presynaptic terminal

Question 29

What is the function of autoreceptors?

Answer 29

Safety valve
- common effect is inhibition of neurotransmitter release

Question 30

What are the possible fates of synaptic released neurotransmitters?

Answer 30

• diffusion of transmitter molecules away from the synapse
• reuptake: neurotransmitter re-enteres presynaptic axon terminal (requires plasma membrane transport proteins)
• uptake by nearby glia cells AKA astrocytes (requires plasma membrane transport proteins)
• enzymatic degradation

Question 31

What is neuropharmacology?

Answer 31

study of effect of drugs on the nervous system

Question 32

What are receptor antagonists?

Answer 32

inhibitors of neurotransmitter receptors
ex. curane

Question 33

What are receptor agonists?

Answer 33

mimic actions of naturally occurring neurotransmitters
ex. nicotine

Question 34

How does drug addiction work molecularly?

Answer 34

destroys brain reward circuits