Synaptic Transmission

Question 1

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

Answer 1

A synapse

Question 2

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

Answer 2

Neuromuscular junction

Question 3

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

Answer 3

Neuroglandular junction

Question 4

What are the two types of synapse?

Answer 4

1. Chemical synapse

2. Electrical synapse

Question 5

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

Answer 5

A neurotransmitter

Question 6

In an electrical synapse how is the message carried?

Answer 6

By flow of a current through a low resistance electrical junction

Question 7

What is the more common synapse in mammals?

Answer 7

Chemical

Question 8

What is the neurotransmitter and the neuromuscular junction?

Answer 8

Acetylcholine

Question 9

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

Answer 9

Nicotine is an agonist at acetylcholine nictonic receptors

Question 10

What is an antagonist of aetylchloine at nictotinic receptors?

Answer 10

Curare (tubocurraine)(competitve reversible)

Question 11

What is the effect of curare (tubocurraine)

Answer 11

It blocks the transmission at the neuromuscular junction and causes paralysis

Question 12

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

Answer 12

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

Question 13

Where do 95% of all synapses take place?

Answer 13

Between an axon terminal (releases neurotransmitter) and a dendrite

Question 14

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

Answer 14

The presynaptic element

Question 15

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

Answer 15

The post synaptic element

Question 16

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

Answer 16

It means there is a synaptic cleft between the two elements

Question 17

What is the synaptic delay?

Answer 17

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

Question 18

How long is the synaptic delay?

Answer 18

0.5ms

Question 19

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

Answer 19

A dense structure of proteins and receptors

Question 20

What are the two actions of the chemical synapses?

Answer 20

1. Excitation

2. Inhibition

Question 21

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

Answer 21

Excitatory neurotransmitters make the post synaptic element more positive

Question 22

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

Answer 22

Excitatory postsynaptic potentials (EPSPs)

Question 23

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

Answer 23

The threshold

Question 24

What is temporal summation?

Answer 24

When several EPSPs are generated in rapid succession by one synapse

Question 25

What is spatial summation?

Answer 25

When several synapses generate EPSPs simulataneously

Question 26

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

Answer 26

Inhibitory neurotransmitters - they make the post synapic element more negative

Question 27

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

Answer 27

Inhibitory postsynaptic potentials (IPSPs)

Question 28

How does hyperpolarisation lead to imhibition?

Answer 28

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

Question 29

Where are inhibitory synapses located?

Answer 29

On the cell body or around the axon hillock

Question 30

What are excitatory synapses located?

Answer 30

On the dendrites

Question 31

What is presynaptic inhibition?

Answer 31

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

Question 32

What are inhibitory synapses formed between two axon terminals called?

Answer 32

Axo-axonic synapses

Question 33

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

Answer 33

The post and pre synaptic terminals

Question 34

How do axo-axonic inhibitory synapses work?

Answer 34

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

Question 35

How could you demonstrate the existence of electrical synapses?

Answer 35

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

Question 36

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

Answer 36

Small positive or negative potentials with no synaptic delay

Question 37

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

Answer 37

Using dyes with a molecular weight

Question 38

What are the substrates of electrical synapses?

Answer 38

Gap junctions

Question 39

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

Answer 39

Connexons or an array of tubes

Question 40

What is the reason electrical synapses operate very quickly?

Answer 40

No synaptic delay

Question 41

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

Answer 41

1. Escape mechanism as shown in the crayfish tail flip

2. Synchronising neuronal activity e.g. burster neurons in pond snails generate rhymic activity