Axons and Transmissions

Question 1

What is the resting potential of a cell

Answer 1

-50 to -70 mV

Question 2

At resting what is found at higher concentrations within the cell that outside

Answer 2

K+

Question 3

At resting what is found at higher concentrations outside the cell than inside

Answer 3

Na+

Cl-

Question 4

At depolarisation what channels are open

Answer 4

Voltage-gated sodium ion channels

Makes the inside cell more positive

Question 5

What must be met for an action potential to be reached

Answer 5

Threshold potential

Question 6

What is an action potential described as

Answer 6

All or nothing

Question 7

Once the cell has depolarised what happens

Answer 7

Voltage gated sodium channels begin to close

Voltage gated potassium channels open

K+ moves out of the cell

Question 8

When is the absolute refractory period

Answer 8

Overlaps depolarisation and around 2/3 of repolarisation phase

Question 9

Absolute refraction

Can a new action potential be generated and why

Answer 9

No

Voltage-gated sodium channels already open

OR

Sodium channels inactive recover from inactive state

Question 10

When is the refractory period

Answer 10

1/3 of repolarisation (last)

Question 11

Can a new action potential be generated during reflective period

Answer 11

Possible

Question 12

In depolarisation what ions are moving

Answer 12

Na+ IN

Question 13

During repolarisation what ions are moving

Answer 13

K+ out

Question 14

What re-establishes resting state

Answer 14

Refractory period

Question 15

Define a synapse

Answer 15

Gap present between two neurones

Question 16

Where is acetylcholine synthesised

Answer 16

In the axon

Question 17

What are the basic components of the neuron

Answer 17

Dendrites

Cell body/soma

Axon

Presynaptic terminal

Question 18

What can move across a neuronal cell membrane

Answer 18

Easily - K+ Cl-

Difficulty - Na+

Some not at all - large organic proteins -ve charge

Question 19

What is role of myelination

Answer 19

Speeds up axonal conduction

Question 20

What are between myelin

Answer 20

Nodes of Ranvier

Question 21

What do most CNS neurones have

Answer 21

Myelin

Question 22

What breaks down acetylcholine

Answer 22

Acetylcholinesterase

Question 23

Describe synaptic transmission

Answer 23

Neurotransmitter released

Calcium ion channels open when action potential reaches pre-synaptic terminal

Ca2+ ions cause vesicles to move to the release sites - fuse with the cell membrane - and discharge their contents

Transmitter substance diffuses across synaptic cleft

Attach to receptor sites on post-synaptic membrane

Question 24

What are the five processes of synaptic transmission

Answer 24

Manufacture - intracellular biochemical processes

Storage - vesicles

Release - by action potential

Interact with post-synaptic receptors - diffusion across the synapse

Inactivation - break down or re-uptake

Question 25

Give examples of fast neurotransmitters

Answer 25

ACh Glutamate (GLU) Gamma-aminobutyric acid (GABA)

Question 26

Give examples of slow neurotransmitters

Answer 26

Dopamine (DA) Noradrenaline Serotonin

Question 27

Describe the initation and propagation of action potentials

Answer 27

Receptors - neurotransmitter activated ion channels (dendritic tree and cell body) Summination at the axon hillock Voltage activated ion channels (mainly Na+ and K+) Positive outside to positive inside

Question 28

What can neurotransmitters be divided into

Answer 28

Excitatory Inhibitory

Question 29

Define excitatory neurotransmitters

Answer 29

Increase likelihood of postsynaptic neurone depolarisation and generation of an action potential

Question 30

Define inhibitory neurotransmitters

Answer 30

Reduce likelihood of postsynaptic neurone depolarisation and generation of an action potential

Question 31

In the peripheral axons what is myelination produced by

Answer 31

Schwann cells

Question 32

In the central axons what is myelination produced by

Answer 32

Oligodendrocytes

Question 33

How do you remember which cell is responsible for myelination

Answer 33

COPS Central - oligodendrocytes Peripheral - Schwann

Question 34

How many axons does a Schwann cell myelinate

Answer 34

1

Question 35

How many Schwann cells will peripheral axons have

Answer 35

Multiple One Schwann cell wraps a lipid-rich membrane around approx 1mm of an axons length

Question 36

What are the gaps called between Schwann cells and myelin sheath

Answer 36

Nodes of Ranvier

Question 37

How many axons does a single oligodendrocyte myelinate

Answer 37

Multiple The cell body and nucleus of oligodendrocytes remain separate from the myelin sheath

Question 38

In which cell that produces myelin is neurilemma found

Answer 38

Schwann cell Cell body and nucleus enveloping an axon

Question 39

What is the difference between Nodes of Ranvier between CNS and PNS

Answer 39

CNS have fewer

Question 40

PNS - if an axon is damaged how much growth can there be

Answer 40

Can be growth

Question 41

CNS - if an axon is damaged how much growth can there be

Answer 41

Little Due to inhibitory influence on regrowth from the oligodendrocytes and lack of neurolemma

Question 42

Describe chemical synapse

Answer 42

Involves neurotransmitter Carry information from the pre-synaptic-sending-neuron to the post synaptic -receiving cell Single axon can have multiple branches can synapse on various post synaptic cells Synaptic vesicles - membrane bound spheres filled with neurotransmitter molecules

Question 43

Describe electrical synapse

Answer 43

Direct physical connection between the presynaptic and postsynaptic neuron Uses gap junctions - allow current-ions to flow from one cell to another