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Flashcards in Synaptic Transmission Deck (41):
1

What is the junction between neurons over which a signal is transferred?

A synapse

2

What is the junction between a neuron and a muscle over which as signal is transferred?

Neuromuscular junction

3

What is the specialised junction between a neuron and a gland over which a signal is transferred?

Neuroglandular junction

4

What are the two types of synapse?

1. Chemical synapse
2. Electrical synapse

5

Is a chemical synapse what is the message carried by across the synapse?

A neurotransmitter

6

In an electrical synapse how is the message carried?

By flow of a current through a low resistance electrical junction

7

What is the more common synapse in mammals?

Chemical

8

What is the neurotransmitter and the neuromuscular junction?

Acetylcholine

9

What is an agonist of acetylcholine at the neuromuscular junction? What receptors do they both bind two?

Nicotine is an agonist at acetylcholine nictonic receptors

10

What is an antagonist of aetylchloine at nictotinic receptors?

Curare (tubocurraine)(competitve reversible)

11

What is the effect of curare (tubocurraine)

It blocks the transmission at the neuromuscular junction and causes paralysis

12

How would you reverse the effect of curare (tubocurraine) at the NMJ?

Use a drug (eserine, neostigmine) that inhibits the drug acetylcholinesterase that breaks down acetylcholine so inhibiting it will increase the concentration of Ach and reverse the effect of the antagonist

13

Where do 95% of all synapses take place?

Between an axon terminal (releases neurotransmitter) and a dendrite

14

What is the axon terminal known as when its taking place in a synapse?

The presynaptic element

15

What is the dendrite known as when its taking part in a synapse?

The post synaptic element

16

What does it mean when you say the synaptic elements are discontinuous?

It means there is a synaptic cleft between the two elements

17

What is the synaptic delay?

The time it takes for the neurotransmitter to be released from the axon terminal in a vesicle via exocytosis and diffuse across the synaptic cleft

18

How long is the synaptic delay?

0.5ms

19

What kind of structure is present at the post synaptic element?

A dense structure of proteins and receptors

20

What are the two actions of the chemical synapses?

1. Excitation
2. Inhibition

21

What kind of neurotransmitters cause depolarisation of the postsynaptic membrane? What effect do they have?

Excitatory neurotransmitters make the post synaptic element more positive

22

What are the depolarisations of the post synaptic membrane by an excitatory neurotransmitters called?

Excitatory postsynaptic potentials (EPSPs)

23

What does the sum of the EPSPs have to reach in order for an action potential to fire?

The threshold

24

What is temporal summation?

When several EPSPs are generated in rapid succession by one synapse

25

What is spatial summation?

When several synapses generate EPSPs simulataneously

26

What kind of neurotransmitters cause hyperpolarisation of the post synaptic membranes? What effect do they have?

Inhibitory neurotransmitters - they make the post synapic element more negative

27

What are the hyperpolarisation of the post synaptic membrane by the inhibitory neurotransmitters called?

Inhibitory postsynaptic potentials (IPSPs)

28

How does hyperpolarisation lead to imhibition?

Because the output of the neuron is coverned by the sum of EPSPs and IPSPs so hyperpolarisation by lots of IPSPs means the neurone wont reach threshold to fire an action potential

29

Where are inhibitory synapses located?

On the cell body or around the axon hillock

30

What are excitatory synapses located?

On the dendrites

31

What is presynaptic inhibition?

Special type of inhibition that occurs in the brain and the spinal chord

32

What are inhibitory synapses formed between two axon terminals called?

Axo-axonic synapses

33

What are the axon terminals of the axo-axonic synapses known as?

The post and pre synaptic terminals

34

How do axo-axonic inhibitory synapses work?

They reduce the amount of neurotransmitter released from the postsynaptic terminal so inhibit it

35

How could you demonstrate the existence of electrical synapses?

By injecting depolarising or hyperpolarising current into one neuron and recording from another neuron

36

What is recorded that shows the prescence of a electrical synapse?

Small positive or negative potentials with no synaptic delay

37

How could you use dyes to show the prescense of an electrical synapse?

Using dyes with a molecular weight

38

What are the substrates of electrical synapses?

Gap junctions

39

What are responsible for the communication across gap junctions if they do not have vesicles but still have a small gap?

Connexons or an array of tubes

40

What is the reason electrical synapses operate very quickly?

No synaptic delay

41

Name two properties the animals that have evolved electrical synapses have evolved?

1. Escape mechanism as shown in the crayfish tail flip
2. Synchronising neuronal activity e.g. burster neurons in pond snails generate rhymic activity