Synapse 1

Question 1

Functions of neurons:

Answer 1

Cell processes

Interconnect cells

Transmit information

Use electrical signals

Question 2

What’s important to know about neurons?

Answer 2

Separate entities - separate cells that communicate with each other

Question 3

What’s the only way that neurons can communicate with each other?

Answer 3

Through axons

Question 4

Direction of signal in dendrites?

Answer 4

Propagates towards cell body

Question 5

Direction of signal in axons?

Answer 5

Propagates away from cell body

Question 6

Potential difference in axon before electrical activity generated?

Answer 6

-70 mV

Resting membrane potential

Question 7

Characteristics of action potentials:

Answer 7

Self propagates

Travels in one direction - vectorial down axon

No ‘volume control’ - always same size of AP

Question 8

What happens if there is a higher frequency of action potentials?

Answer 8

Faster signal

Question 9

How are action potentials graded?

Answer 9

In frequency not amplitude

Question 10

Where do action potentials start?

Answer 10

At cell body (axon hillock)

Question 11

Where are action potentials transmitted in axons?

Answer 11

Towards end of axon - to end bulb/synapse

Question 12

What do action potentials cause at the end of the axon?

Answer 12

Secretion of chemicals (neurotransmitters)

Question 13

What essentially are neurons?

Answer 13

Elongated secretory cells that are polarised

Question 14

How are neurons similar to secretory cells?

Answer 14

Axon is equivalent to apex of secretory cell

Dendrites are equivalent to basal aspect of secretory cell

Question 15

What’s the axon end bulb the site of?

Answer 15

Chemical neurotransmitter release

Question 16

What is the gap between two neurons called?

Answer 16

Synaptic cleft

Question 17

WHat’s the cell before the gap called?

Answer 17

Presynaptic cell

Question 18

What’s the cell called after the gap?

Answer 18

Postsynaptic cell

Question 19

What does the swelling in terminal of presynaptic cell form?

Answer 19

Bouton

Question 20

What is reception of signals by?

Answer 20

Via highly branched processes - dendrite tree and dendritic spines

Question 21

How does vesicle and presynaptic membrane recognise each other?

Answer 21

v-SNARE on vesicle complexes with t-SNARE at presynaptic membrane

Question 22

What do v-SNARE and t-SNARE do?

Answer 22

They form a complex that folds strongly to draw vesicle and presynaptic membranes close

Question 23

What happens when vesicle and presynaptic membranes are drawn close?

Answer 23

Vesicle is docked on membrane - clamped by synaptotagmin

Question 24

What removes vesicle from synaptotagmin clamp?

Answer 24

Action potential triggers calcium influx at end-bulb

This reorient membrane and helps align SNARE complex for fusion

Question 25

Where are peptide neurotransmitters made?

Answer 25

RER Packaged into vesicles in Golgi

Question 26

What happens after peptide neurotransmitters leave Golgi?

Answer 26

Transported along microtubules to axon terminal Vesicles are then charged in axon terminal

Question 27

What are the two classes of receptors for neurotransmitters on post synaptic membrane?

Answer 27

Ionotropic receptors - fast signals Metabotropic - slow signals

Question 28

How do ionotropic receptors work?

Answer 28

Neurotransmitter binds to receptor - induces conformational change Pore opens + ions flow in/out Voltage of cell then changes

Question 29

What can ionotropic receptors do to voltage of cell?

Answer 29

Decrease potential = negative ions out or positive ions in Increase potential = negative ions in or positive ions out

Question 30

Give an example of ionotropic receptor:

Answer 30

Acetylcholine receptor

Question 31

Give an example of metabotropic receptor:

Answer 31

G protein-linked receptor

Question 32

What happens in metabotropic receptors?

Answer 32

Receptor binds G-protein (GTP replaces GDP) Active G-protein then leaves + binds target enzyme Enzyme generates messenger Messenger binds channel + channel opens

Question 33

What happens after metabotropic receptor causes ion channel to open?

Answer 33

GDP-ase removes P from GTP which then inactivated G protein G protein then leaves enzyme - inactivated enzyme G protein is then free + ready to bind to receptor

Question 34

Summary of how an ionotropic receptor works:

Answer 34

Neurotransmitter binds Channel opens Ions flow across membrane

Question 35

Summary of how metabotropic receptors work:

Answer 35

Neurotransmitter binds G-protein is activated G-protein subunits or intracellular messengers modulate ion channels Ions flow across membrane Ion channel opens

Question 36

What have electrophysiological experiments shown?

Answer 36

That the release of neurotransmitters is quantal - in packets

Question 37

What does quanta relate to?

Answer 37

The release of contents of single vesicles at the presynaptic membrane

Question 38

What results in a stronger signal at the post synaptic membrane?

Answer 38

More vesicles released

Question 39

What are PSPs caused by?

Answer 39

The passage of ions through ion channels which have opened following receptor/neurotransmitter interactions

Question 40

What does PSP stand for?

Answer 40

Post synaptic potential

Question 41

What is an excitatory PSP (EPSP)?

Answer 41

A net flow of positive ions into the cell Causes depolarisation of membrane - brings closer to threshold

Question 42

Single ESPs:

Answer 42

Rarely result in action potential

Question 43

Amplitude in inhibitory and excitatory PSPs:

Answer 43

Amplitude of signal decreases with distance and time

Question 44

What’s the typical amplitude of an EPSP?

Answer 44

Positive deflection (depolarisation) of between 1-5mV

Question 45

What’s the typical amplitude of an IPSP?

Answer 45

Negative deflection (hyperpolarisation) of between 1-5 mV

Question 46

What’s spatial summation?

Answer 46

Multiple end-bulbs on same dendrite Make large change in potential

Question 47

What’s temporal summation?

Answer 47

One axon firing very quickly Recovery is slow

Question 48

Difference between single EPSP and summed SPSPs:

Answer 48

Single = potential difference may not reach threshold Summed = threshold reached and AP generated

Question 49

What’s hyperpolarisation caused by?

Answer 49

Inhibitory PSP IPSP

Question 50

What can APSPs be caused by?

Answer 50

Direct (ionotropic) or indirect (metabotropic) gating