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Neurology > Basic Buliding Blocks And Axonal Neurotransmission > Flashcards

Basic Buliding Blocks And Axonal Neurotransmission Flashcards

1
Q

What is a neuron?

A

Basic cellular unit of the nervous system

Different range with different functions

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2
Q

Basic components

A

Dendrites

Cell body/soma

Axon

Presynaptic terminals

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3
Q

Connections between neurones

A

Axonal transmission

Synaptic transmission

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4
Q

Axonal transmission

A

Transmission of information from location A to B

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5
Q

Synaptic transmission

A

Integration/processing of information and transmission between neurones

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6
Q

The neurones resting potential

A

The inside of the neurone has a negative electrical charge because of the ions within the neurone

-70mV

Reached using Na+/K+ ATP pump

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7
Q

Neuronal cell membrane semi permeable

A

Some substances which are electrically charged (+ve or –ve) cross readily – potassium (K+) and chloride (Cl-)

Some cross with difficulty – sodium (Na+)

Some not at all – large organic proteins (-ve charge)

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8
Q

What are the forces determining distribution of charged ions?

A

Diffusion

Electrostatic attraction/repulsion

Sodium potassium pump

Slide 11

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9
Q

The action potential

A

Neurone fires- a sudden pulse where the -ve resting potential is temporarily reversed

All or nothing process to transmit information

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10
Q

What events occur in the action potential?

A

Depolarization and threshold- voltage gated sodium ion channels open, allowing Na+ into the axon cytoplasm

Reversal of membrane potential

Repolarization of resting potential- voltage gated K+ ions open, allowing more K+ to diffuse out than Na+ in

Refractory period- Limits the no. of AP an excitable membrane can produce in a given time - so APs can be separated
-Absolute refractory period = during repolarisation - neuron cannot generate new AP
-Relative refractory period = hyperpolarisation - neuron can generate new AP if stimulus = larger than one previously

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11
Q

Membrane permeability changes

A

The membrane potential remains in this resting ‘stable’ state until something disturbs the balance

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12
Q

Neurotransmitter initiate such changes at the dendrites of neurones

A

Neurotransmitters activate receptors on dendrites / soma

Receptors open ion channels

Ions cross plasma membrane, changing the membrane potential
The potential changes spread through the cell

If the potential changes felt at the axon hillock are positive (+mV), and large enough, an action potential is triggered

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13
Q

Depolarisation/Hyperpolarisation

A

Depolarise -more +ve V
Polarised at -70mV= RMP
Hyperpolarise -more -ve V

Excitably neurotransmitters depolarise the cell membrane causing them to push towards the membrane
This increases probability of an action potential being evoked
This causes an excitably post synaptic potential

Inhibitory neurotransmitters hyperpolarise the cell membrane decreasing the probability of an action potential being evoked
This causes an inhibitory post synaptic potential (ISPS)

An action potential will be evoked if the membrane potential is depolarised beyond the threshold of excitation

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14
Q

Postsynaptic potentials

A

Voltage changes spread away (decrementally) from point of origin (Passive Conduction)

Whether AP is generated depends on what reaches the axon hillock

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15
Q

Excitatory post synaptic potential (EPSP).

A
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16
Q

Inhibitory post synaptic potential

A
17
Q

Spatial vs Temporal summation

A

Spatial summation occurs when several weak signals from different locations are converted into a single larger one

Temporal summation converts a rapid series of weak pulses from a single source into one large signal

18
Q

The action potential

A

EPSPs begin to depolarise cell membrane
Threshold ~ -60mV (varies from cell to cell)
When reached Na+ channels open (Na+ rushes in) and polarity reverses to +30 inside
Membrane potential reverses with the inside going positive
…at which point voltage-gated Na+ channels close and K+ channels open (K+ rushes out)
…which restores resting membrane potential

19
Q

What are voltage changes caused by?

A

The opening or closing of ion channels

In the cell membrane there are channels which are opened by voltage changes voltage changes control the ion channels which control the voltage changes
The action potential is therefore self perpetuating

When triggered at axon hillock, the action potential will travel along the entire axon

20
Q

Initiation and propagation of the action potential

A

Slide 21

21
Q

How is Axonal conduction sped up?

A

By myelination

Myelin comes from oligodendrocytes in the CNS and from Schwann cells in the PNS

22
Q

Saltatory conduction

A

Decremental (reduced) conduction between nodes (but re-boosted each time)

But very fast along axon

Most CNS neurones

23
Q

Axonal transmission

A

Transmission of information from location A to B

24
Q

Synaptic transmission

A

Integration/ processing of information

25
Q

Novichok

A

Disrupts normal synaptic neurotransmission for neurotransmitter acetylcholine

26
Q

What occurs when the action potential reaches the terminal buttons?

A

Calcium ion channels open when action potential reaches pre-synaptic terminal
Ca++ ions cause vesicles to move to 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

27
Q

What happens to the neurotransmitter then?

A

Continually trying to excite the next neurone

Would remain active in synapse if it wasn’t for:
-enzymatic degradation
-reuptake

Acetylcholinesterase is the enzyme that breaks down ACh

28
Q

What does ACh do?

A

It is the key neurotransmitter at the neuromuscular junction – it activates muscles

Not just skeletal muscles (for voluntary movement), also heart, respiratory muscles, gastrointestinal tract, eye muscles, muscles around blood vessels

29
Q

5 funds,mental 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

Slide 42

30
Q

Fast neurotransmitters

A

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

31
Q

Neuromodulators- slow

A

Dopamine (DA)
Noradrenalin (NA) (norepenephrine)
Serotonin (5HT) (5-hydroxytryptamine)

32
Q

Acetylcholine

A

Transmitter at the neuromuscular junction, also used widely in brain and spinal cord

33
Q

Noradrenaline

A

Transmitter in peripheral (Heart) and CNS

34
Q

Dopamine

A

Important transmitter in basal ganglia

35
Q

Serotonin

A

Involved in many processes in brain no actual function

Diverging projections in brain- innervation many structures

36
Q

GABA

A

Main inhibitory transmitter

Neurology (22 decks)

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