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Neuro > Axons and Transmissions > Flashcards

Axons and Transmissions Flashcards

1
Q

What is the resting potential of a cell

A

-50 to -70 mV

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2
Q

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

A

K+

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3
Q

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

A

Na+

Cl-

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4
Q

At depolarisation what channels are open

A

Voltage-gated sodium ion channels

Makes the inside cell more positive

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5
Q

What must be met for an action potential to be reached

A

Threshold potential

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6
Q

What is an action potential described as

A

All or nothing

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7
Q

Once the cell has depolarised what happens

A

Voltage gated sodium channels begin to close

Voltage gated potassium channels open

K+ moves out of the cell

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8
Q

When is the absolute refractory period

A

Overlaps depolarisation and around 2/3 of repolarisation phase

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9
Q

Absolute refraction

Can a new action potential be generated and why

A

No

Voltage-gated sodium channels already open

OR

Sodium channels inactive recover from inactive state

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10
Q

When is the refractory period

A

1/3 of repolarisation (last)

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11
Q

Can a new action potential be generated during reflective period

A

Possible

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12
Q

In depolarisation what ions are moving

A

Na+ IN

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13
Q

During repolarisation what ions are moving

A

K+ out

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14
Q

What re-establishes resting state

A

Refractory period

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15
Q

Define a synapse

A

Gap present between two neurones

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16
Q

Where is acetylcholine synthesised

A

In the axon

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17
Q

What are the basic components of the neuron

A

Dendrites

Cell body/soma

Axon

Presynaptic terminal

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18
Q

What can move across a neuronal cell membrane

A

Easily - K+ Cl-

Difficulty - Na+

Some not at all - large organic proteins -ve charge

19
Q

What is role of myelination

A

Speeds up axonal conduction

20
Q

What are between myelin

A

Nodes of Ranvier

21
Q

What do most CNS neurones have

A

Myelin

22
Q

What breaks down acetylcholine

A

Acetylcholinesterase

23
Q

Describe synaptic transmission

A

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

24
Q

What are the five processes of synaptic transmission

A

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

25
Q

Give examples of fast neurotransmitters

A

ACh

Glutamate (GLU)

Gamma-aminobutyric acid (GABA)

26
Q

Give examples of slow neurotransmitters

A

Dopamine (DA)

Noradrenaline

Serotonin

27
Q

Describe the initation and propagation of action potentials

A

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

28
Q

What can neurotransmitters be divided into

A

Excitatory

Inhibitory

29
Q

Define excitatory neurotransmitters

A

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

30
Q

Define inhibitory neurotransmitters

A

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

31
Q

In the peripheral axons what is myelination produced by

A

Schwann cells

32
Q

In the central axons what is myelination produced by

A

Oligodendrocytes

33
Q

How do you remember which cell is responsible for myelination

A

COPS

Central - oligodendrocytes

Peripheral - Schwann

34
Q

How many axons does a Schwann cell myelinate

A

1

35
Q

How many Schwann cells will peripheral axons have

A

Multiple

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

36
Q

What are the gaps called between Schwann cells and myelin sheath

A

Nodes of Ranvier

37
Q

How many axons does a single oligodendrocyte myelinate

A

Multiple

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

38
Q

In which cell that produces myelin is neurilemma found

A

Schwann cell

Cell body and nucleus enveloping an axon

39
Q

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

A

CNS have fewer

40
Q

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

A

Can be growth

41
Q

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

A

Little

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

42
Q

Describe chemical synapse

A

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

43
Q

Describe electrical synapse

A

Direct physical connection between the presynaptic and postsynaptic neuron

Uses gap junctions - allow current-ions to flow from one cell to another

Neuro (15 decks)

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