Neurotransmitters

Question 1

Two main types of synapses are

Answer 1

1) Electrical

2) Chemical

Question 2

What is a gap junction and what makes it up

Answer 2

a channel which forms a low resistance pore between cells

Connexins form a hemichannel in each cell called connexons. These Connexons join to form a gap junction.

Question 3

Gap junctions make up what type of synapses

Answer 3

Electrical

Question 4

How does a chemical synapse work

Answer 4

Action Potential invades and leads to release of a chemical transmitter which diffuses across a synaptic cleft to interact with ligand-gated ion channels in the postsynaptic membrane. Electrical signals are thus transduced into a chemical signal

Question 5

Chemical transmission is unidirectional whereas electrical transmission is bi-directional

Answer 5

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Question 6

Steps of chemical neurotr5ansmission

Answer 6

1) Transmitter is synthesized and stored in vesicles in the synaptic terminal
2) An action potential invades the terminal
3) Terminal depolarizes
4) Depolarization opens up the voltage gated calcium channels leading to influx of calcium
5) Calcium influx causes fusion of synaptic vesicles with presynaptic membrane (via SNARES) Release occurs in packets called quanta. Contents of 1 veisicle = 1 quanta
6) Transmitter is released into synaptic cleft and diffuses across

Postsynaptically

1) Transmitter binds to receptors
2) Opening or closing of ion channels occurs
3) Postsynaptic currents cause membrane potential change

Question 7

What does the “high safety factor” of chemical synaptic transmission at the neuromuscular junction refer to?

Answer 7

Ensures that every time a motoneuron releases neurotransmitter, every muscle fiber it inntervates has a an AP and contracts

Question 8

What are some of the anatomical specializations at the NMJ to ensure this high safety factor

Answer 8

many release sites for neurotransmitter, high number of receptors, high quantal content, and high probability of release for each quanta, high number of postsynaptic receptors

Question 9

What is the neurotransmitter at the NMJ?

Answer 9

Acetylcholine

Question 10

What type of receptors are present at the NMJ?

Answer 10

Nicotinic

Question 11

Know that CNS synapses are much simpler anatomically than the NMJ synapses

Answer 11

ok

Question 12

CNS synapses are also much more diverse than the NMJ, there are many different transmitters and responses can either be excitatory inhibitory or modulatory

Answer 12

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Question 13

Two types of chemical transmission are

Answer 13

Ligand Gated and G- Protein Coupled

Question 14

Fast transmission =

Answer 14

Ligand gated

Question 15

What does it mean to say that Ligand gated channels are an integrated receptor?

Answer 15

The binding site for the ligand - neurotransmitter- is part of the same molecular complex as the channel. Binding of the ligand causes a conformational change in the channel resulting in gating activation.

Question 16

G- Protein coupled Receptors mediate “neuromodulatory effects”, that is

Answer 16

Biochemical changes in the cell which alter function an/or excitability.

Question 17

G- protein coupled receptors have 7 transmembrane spanning regions and when they bind a ligand, conformational change facilitates interaction with a G- Protein.

Answer 17

ok

Question 18

At teh neuromuscular junction, chemical synaptic transmission is specialized for what?

Answer 18

High Safety factor to ensure that every time a motoneuron releases transmitter, every muscle fiber it innervates has an AP

• Many neurotransmitter release sites
• High number of receptors
• High quantal content
• High probability of release for each quanta

Question 19

What is the Neurotransmitter at the NMJ and what type of receptor is present

Answer 19

Ach, Nicotinic

Question 20

What is different about synapses in the CNS than synapses in the NMJ

Answer 20

CNS synapses are much simpler anatomically than the NMJ. Low Quantal content and low safety factor. Much more diverse as well… transmitter responses can be either excitatory, inhibitory, or modulatory

Question 21

Ach

Answer 21

Excitatory

Question 22

Glutamate

Answer 22

Excitatory

Question 23

GABA

Answer 23

Inhibitory

Question 24

Dopamine

Answer 24

Excitatory via D1, Inhibitory via D2

Question 25

Norep

Answer 25

Excitatory

Question 26

Substance P

Answer 26

Excitatory

Question 27

Histamine Excitatory

Answer 27

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Question 28

Calcium interacts with what proteins (directly) in the presynaptic terminals?

Answer 28

SNAREs

Question 29

SNAREs do what

Answer 29

Facilitate docking of neurotransmitters at the postsynaptic terminal

Question 30

Lmbert Eaton Myasthenic Syndrome is what

Answer 30

When small cell carcinomas release antibodies against presynaptic L- type calcium channels

Question 31

Myasthenia Gravis

Answer 31

autoimmune disease that targets the nicotinic receptor at the NMJ

Question 32

Botulinum toxin and SNARE proteins?

Answer 32

Yeah…SNARE proteins can be damaged by the clostridial bacterial toxins botulinum and tetanus.

Question 33

Botox does what

Answer 33

Blocks Ach release at the NMJ

Question 34

Myasthenia Gravis does what

Answer 34

Blocks Acetylcholine uptake by the NMJ

Question 35

EPSP?

Answer 35

Excitatory Post-synaptic potential….increases the likelihood of an AP occurring.

Question 36

What are the most common mediatorys of EPSP?

Answer 36

glutamate or aspartate

Question 37

Remember that most synaptic inputs are far too small to elicit an AP on their own. How do neurons derive an AP from these types of inputs?

Answer 37

Summation

Neuronal somas and initial segments can integrate synaptic inputs and generate summation of inputs that would otherwise be too small to generate an AP alone

Question 38

Two types of synaptic integration

Answer 38

Temporal Summation- occurs when two PSPs elicited in the same synapse occur close enough in time so that the first has not completely decayed before the second occurs

Spatial Summation: refers to addition of effects of two different synapses that are close enough in location

Question 39

Know Brain energy metabolism resting and activated

Answer 39

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