Lecture 16; The Chemical Brain 2

Question 1

What is the function of electrical synapses?

Answer 1

Physically connects cytoplasm of two cells
if one cell depolarises, so does the other
Reduction of signal strength as it passes
Faster
Used in some Reflexes • Escape Responses
Bidirectional

Question 2

What are the advantages of chemical synapses?

Answer 2

Synaptic delay’ but 
• GAIN (Amplification)
Unidirectional (one-way)
The post synaptic neurones can either depolarise of hyper polarise
reater complexity of processing
• Produce long-lasting changes... 
• Synaptic plasticity
• LTP, LTD

Question 3

Where are gap junctions present between?

Answer 3

neurons
glial cells, including astrocytes, oligodendrocytes, and microglia;
ependymal cells
eptomeningeal cells.

Question 4

What does each neurone have?

Answer 4

many incoming synapses, and may have multiple outgoing synapses

Question 5

What are necessary for action potentials?

Answer 5

Simultaneous signals

Question 6

What is involved in a tripartite synapse?

Answer 6

Astrocytes

Question 7

What do astrocytes do?

Answer 7

They recycle NTs
If glutamate is left over, it will use the G-G cycle in order to return back to neurone and create more NTs
Have own receptors which respond to NTs

Question 8

How are microglia now involved in the Tripartite Synapse?

Answer 8

Microglia now also known to regulate synapses

Resident macrophage in the CNS

Question 9

Without microglia, what do you not get properly?

Answer 9

Synaptic plasticity, microglia is very involved in the development of synapses being known as a synaptic modellers

Question 10

What is a method to define a NT?

Answer 10

1. Must be present within the presynaptic neuron
2. Must be released in response to presynaptic depolarization, and must be Ca2+-dependent
3. Specific receptors for the substance must be present on the postsynaptic cell

Question 11

How to tell apart NT and Neuromodulator apart?

Answer 11

A NT has a;
Anatomically-specialised junction (release site)
Across narrow cleft (distance of effect)

Question 12

What can delivering new dopamine producing cells to Parkinsons patients do?

Answer 12

can restore function, without recreating synapses

Question 13

How are Neuromodulators different to NTs?

Answer 13

released at axon terminals, but can act outside synaptic clefts

Question 14

How do NTs get to the synapse?

Answer 14

along the tracks microtubules provide, they travel down the soma
the directional movement of these membrane bound vesicles is due to the family of motor proteins linking the vesicles to the microtubule
Kinesin travels down soma
Dyenin travels up to the soma

Question 15

What are NT receptors either?

Answer 15

Ionotropic or Metabotropic

Question 16

What do Ionotropic receptors consist of?

Answer 16

Combined Binding site + Ion channel
• Short latency (10-50 ms)
• Postsynaptic (usually…)

Question 17

What do Metabotropic receptors consist of?

Answer 17

Binding site not associated with Ion channel
• G-protein / 2nd Messenger
• Longer latency
• Pre- and post-synaptic

Question 18

What NTs are involved in both Metabotropic and Ionotropic receptors?

Answer 18

ACh
GABA
Glutamate
5-HT

Question 19

What two entrances does metabotropic receptors use?

Answer 19

Using G protein to activate Ion channel

Using G protein to create a signalling cascade

Question 20

Which receptors associated with glutamate is Ionotropic?

Answer 20

NMDA, AMPA, Kainate

Excitatory response

Question 21

Which receptors associated with glutamate is Metabotropic?

Answer 21

Group I, II, III
I - slow and excitatory response
II & III - slow and inhibitory response

Question 22

What can glutamate receptors be?

Answer 22

pre-, post- and extra-synaptic

Question 23

Why do NT Receptors have different locations and actions?

Answer 23

• Some Depolarise or Hyperpolarise the post-synaptic neuron
• Some physically alter the synapse to change future responses
• Increase strength of future de- or hyper-polarisation
• Achieved by adding / removing different receptors
• Synaptic plasticity • LTP, LTD

Question 24

What is GABA A receptor?

Answer 24

consists of five subunits that span the membrane
they bind together creating a chloride channel
When chloride travels through it changes the membrane potential

Question 25

Does GABA have inotropic and metabotropic receptors?

Answer 25

yes

Question 26

What is conditioning?

Answer 26

This is where the function of synapses can be altered and modulated so that it can increase productivity.

An example could be instead of one receptor being activate, 3 are instead leading to many intracellular reactions and eventually altered gene expression.