Neurotransmission Flashcards

1
Q

What is the main function of nerve cells or neurons ?

A

Is to receive o, conduct and transmit signals

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2
Q

Pre -Synaptic cleft

A

Pre-synaptic terminal (at end of axon):  Storage vesicles for a particular extracellular signalling molecule (neurotransmitter)

 (How is release triggered?)  Synaptic cleft:  12-20 nm gap 

Post-synaptic membrane: transmitter-gated ion channels

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3
Q

What triggers an action potential ?

A

Depolarization , of the plasma membrane

Membrane potential is less negative value inside

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4
Q

Voltage -gates Na+ channel?

A

In nerve and skeletal muscle cells , a stimulus that causes sufficient depolarization promptly opens the vated gated Na+ channels allowing a small amount of Na + to enter the cell down electrical gradient

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5
Q

Summary of ion gradients in resting cells

A

Na+/K+ ATPase: Actively pumps ions against electrochemical gradient

At rest, ion channels are largely closed.

The voltage generated in neurons at rest is about -70 mV to -80 mV (i.e., negative inside)

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6
Q

Different stimuli might open a channel

A

The plasma membrane of all excitable cells contain

Voltage gated channel which are responsible for generating NA+ to enter the cell down

The influx of positive charge depolarizes the membrane further , thereby opening more Na+ channels which admits more Na + ions causing further depolarization

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7
Q

Cytoskeleton ?

A

Dynamic and adaptable

Regulation of the dynamic behaviour and assembley of cytoskeleton filaments allow eukaryotic cells to build an enourmous range of structures from three basic filaments systems

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8
Q

Different stimuli might open a channel

A

The plasma membrane of all excitable cells contain Voltage gated channel which are responsible for generating an electrical wave (action potential) that travels along the membrane.

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9
Q

What happens to the transmembrane voltage as a result of: Opening sodium channels?

A

Depolarises the membrane (Na+ ions move inside down their electrochemical gradient, collapsing the negative-inside electrical gradient) 

Excitatory neurotransmitters generally open Na+ channel receptors, causing a local depolarisation at the postsynaptic membrane 

Large change, as Na+ is far from equilibrium

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10
Q

What happens after Depolarisation ?

A

After depolarisation, Na+ channels inactivate, preventing further Na+ fluxes until membrane potential is restored

Depolarisation by Na+ influx increases membrane permeability to K+

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11
Q

Which class of Receptors might be engaged? Why ?

A

Because the signal that needs to be propagated from one neuron to another is electrical

Involved in rapid synaptic signalling between nerve cells and other electrically excitable targets such as nerve and muscle cells

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12
Q

How does our brain communicate to our muscle to contract?

A

When acetylcholine binds to its receptor on the muscle membrane it transiently opens Na+ channel inducing depolarization of the membrane

The depolarization activates voltage gated Ca2+ channels in the transverse tubules of this membrane

This induces Ca2+ channel in the sarcoplasmatic reticulum membrane

The increase in Ca2+ induces the myofibrils to contract

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13
Q

What happens if there is a lack of myelin?

A

In demyelinating neurons the propagation of the nerve impulse is slow

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14
Q

Do you know in which diseases this might happen?

A

In Multiple Sclerosis and many others..

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15
Q

Describe the signalling at the synapse.

A

The action potential triggers the
opening of Ca2+ channels at the presynaptic neuron.

The increase in
Ca2+ triggers the release of neurotransmitter in the presynaptic cleft.

The neurotransmitter binds to its receptor on the post-synaptic neuron

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16
Q

Why the neurotransmission is based on ion channels?

A

Because the
signal travelling through the axon is an action potential, an electrical
wave.

17
Q

What is myelin?

A

It is a plasma membrane that wraps up the axon of

some nerve cells, forming an electrically insulating layer.

18
Q

What is the function of myelin?

A

Myelin is essential for the proper
functioning of the nervous system as it allows faster propagation of
action potential from one node to another.

19
Q

Why micro tubules are oriented in the same direction in axons?

A

To
ensure that vescicles containing neurotransmitters travel from the
soma to the axon. Different motor proteins move vesicles in
anterograde and retrograde directions.

20
Q

Neurotransmission

A

1) When an action potential
arrives at the presynaptic site the
depolarization of the membrane

2) opens voltage gated Ca2+
channels that are clustered at the
pre-synaptic membrane.

 3)Ca2+ influx induces the release of
neurotransmitters in the synaptic
cleft.

 4)The neurotransmitter reaches the
postsynaptic neuron and binds a
transmitter-gated ion channel,
provoking an electrical change in
the postsynaptic cell.
21
Q

Why the neurotransmission is based on ion channels?

A

Because the
signal travelling through the axon is an action potential, an electrical
wave.

22
Q

What do Microtubes do ?

A

Determine the positions of membrane enclosed organelles , direct intrtracellular transport and form mitotic spindle that segregates the chromosomes during cell division

23
Q

What do Actin Filaments do ?

A

Determine the shape of the cells surface and are necessary for whole cell locomotions

24
Q

What do intermediate filaments provide ?

A

Provide mechanical strength