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Explain how a nerve impulse passes along a non-myelinated neuron.
Nerve impulses are electrical impulses that travel along the axons of nerve cells (neurons) carrying various information. Propagation of electricity is possible due to differences in electrical potential between the inside of neuron and what is outside. This difference is due to different constitution of positive and negative ions when comparing the inside of neuron and its surroundings;
There are 3 stages, which are resting potential, action potential and restoration phase.

Resting potential is the time when no impulse is propagated. During the resting potential the inside of neuron is negatively charged (around -70 mV), while the outside matter is positive.

Action potential has 3 sub-stages, which are depolarization, repolarization and hyperpolarization.

Depolarization causes the Na+ channels to open changing the the inside of the neuron from negative to positive and outside from positive to negative.

Repolarization is when the Na+ channels close, membrane permeability to Na+ declines to resting levels. As the sodium gates close, voltage sensitive K+ gates open. The K+ exits the cell and internal negativity of the resting neuron is restored.

Finally there is the refractory period where the resting potential comes back.

To reestablish resting potential we need to move Na+ outside and K+ in. This happens during the restoration phase.

For the restoration we need sodium/potassium pump. This pump is powered by ATP so this is an example of active transport. It moves 3 Na+ ions outside and 2 K + in.

In the end, resting potential is reestablished: there is more of Na+ outside, more K+ inside so both the charges and ions are correctly allocated and the new impulse can be sent along the axon.

Explain the principle of synaptic transmission.

1.  An action potential (change in electrical potential) arrives at the pre-synaptic neuron.

2. The voltage-gated calcium channels on the pre-synaptic neuron to open causes the change in voltage in the neuron causing

3. Calcium ions then diffuse into the pre-synaptic neuron.

4. The increased concentration of Calcium in the neuron then causes synaptic vesicles, containing the neurotransmitter acetylcholine, to move towards the membrane on the pre-synaptic neurone.

5. The vesicles fuse to the membrane and the neurotransmitter is released into the gap between the two neurons (known as the synaptic cleft).

6. The acetylcholine neurotransmitter then diffuses across the synaptic cleft towards the post-synaptic neurons membrane.

7. Here, the acetylcholine neurotransmitter then binds to the complimentary receptors on the post-synaptic neuron's membrane.

8. The increase in concentration of the neurotransmitter causes ligand (chemical) gated sodium channels in the post-synaptic neuron membrane to open, allowing sodium to diffuse into the post-synaptic neuron.

9. The increased concentration of sodium ions now in the post-synaptic neuron depolarize the neuron's membrane causing EPSPs (excitatory post-synaptic potentials).

10.  these EPSPs reach a certain threshold, then an action potential is initiated in the post-synaptic neuron and the impulse has been successfully transmitted from one neuron to the next.

Outline the use of four methods of membrane transport in nerves and synapses

1. Active transport
- sodium-potassium pump resets resting potential in the axon following nerve impulse
- re-uptake of neurotransmitters to the pre-synaptic neuron following synaptic transmission
-removal of Ca2+ from pre-synpaptic neuron following synaptic transmission

2. Simple Diffusion
- diffusion of neurotransmitters across synaptic cleft
- diffusion of K+ ions out of axon in resting potential

3. Facilitated diffusion
- opening of voltage-gated Na+ and K+ channels in action potential
- opening of voltage-gated Ca2 channels at pre-synaptic terminal
- Na+ channels activated at post-synaptic terminal to propagate AP

4. Vesicle Transport
- influx of Ca+ activates vesicles  of neurotransmitters
-exocytosis of neruotransmitters from pre-synaptic neuron to synaptic cleft

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Q1. Explain the principal of synaptic transmission.

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Q1. Explain the principal of synaptic transmission.

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Q2. Explain how a nerve impulse passes along a non-myelinated neuron.
Q3. Outline the use of four methods of membrane transport in nerves and synapses

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Explain the principal of synaptic transmission
-nerve impulse reached to pre synaptic neuron terminal
-depolarization: calcium gated channel open. Influx of calcium ions
-calcium ions causes vesic;es to move to membrane and fuse out
-neurotransmitters diffuse across the synaptic cleft
-neurotransmitter binds to the receptor
-sodium gated chennel open. depolarization of post synaptic neuron
-neurotransmitter broken and absorbed by pre synaptic neuron

Outline the use of four methods of membrane transport in nerves and synapses

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Explain the principle of synaptic transmission:
The nerve impulses reaches the pre-synaptic nerve ending causing the calcium gated channels in the plasma membrane to open, allowing the diffusion of calcium ions. The diffusion of calcium ions cause the vesicles to fuse to the membrane, of the presynaptic axon end, exocytosis takes place, and the neurotransmitters diffuses across the synaptic cleft and binds to the receptors on the post synaptic membrane. This causes the sodium gated channels to open. Finally, the neurotransmitters are broken and absorbed.
Outline the use of four methods of membrane transport in nerves and synapses
1. Active transport
2. Facilitated diffusion
3. Simple diffusion
4. Vesicle transport

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Explain the principal of synaptic transmission
- nerve impulse reaches the presynaptic neuron
- opening of Ca2+ gated channel
- synaptic vesicles fuse with the membrane of presynaptic neuron
- fused vesicles release neurotransmitters into the synaptic cleft by exocytosis
- NT binds to the receptor sites on the membrane of postsynaptic neuron
- causes ion channels to open (diffusion of Na+)
- leads to action potential and depolarisation in postsynaptic neuron

Outline the use of four methods of membrane transport in nerves and synapses.
- facilitated diffusion
--> sodium, potassium gated channel
--> depolarisation and repolarisation (action potential)
- active transport
--> Na+/ K+ pump
--> polarisation

(resting potential)
- exocytosis and endocytosis
--> diffusion
--> synaptic vesicles
(releasing NT from presynaptic neuron to postsynaptic neuron through synaptic cleft)

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Explain the principle of synaptic transmission
- Nerve impulses reached to pre synaptic neuron terminal
- Ca gated channel open and an influx of Ca ions enter causing depolarisation to occur.
- Ca causes the vesicles to move to the membrane and fuse (Exocytosis)
- Neurotransmitters diffuse across the synaptic cleft
- Which bind to the receptors
- Na gated channel open and depolarisation of post synaptic neuron

3) Outline the use of four methods of membrane transport in nerves and synapses
- Diffusion
- Facilitated diffusion
- Sodium potassium channels
- Exo/endocytosis

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resting membrane is polarized;
interior is –70 mV/negative relative to outside;
more sodium ions outside than inside;
more potassium ions inside than outside;
disturbance of membrane opens sodium ion channels;
sodium ions rush to inside of cell;
causing depolarization;
sodium ion channels shut;
potassium ion channels open;
potassium ions rush out;
helping to restore polarized state of membrane;
sodium–potassium pumps maintain polarity;
process repeated along the length of neuron / sodium ions diffuse between region with an action potential and the region at resting potential;

[8 max]

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2.
Nerve impulse reaches endplate of presynaptic neuron.
Ca2+ gated channel open allow facilitated diffusion of Ca2+ ion from synaptic cleft into end plate and activate vesicles containing neurone transmitter. Neurotransmitter move out of pre-synaptic cell by exocytosis into synaptic cleft and bind to voltage gated receptor of post synaptic neurone. cause the dendrite of the post-synaptic neurone to reach threshold potential. Na+ gated channel open allow depolarisation of post synaptic neurone. neurotransmitter is broken down by enzyme of the post synaptic neurone and return into presynaptic neurone by active transport. The Ca2+ ion is released back to synaptic cleft by active transport.

3.
Active transport: Na+/K+ pump at membrane of axon. pump 3 Na+ outside simultaneously absorbing 2K+ inside to restore resting potential. require ATP.
Removal of Ca2+ from presynaptic cell into the synaptic cleft and entrance of broken down neurotransmitter into the presynaptic cell

Facilitated diffusion through Na+ gated channel allow influx of Na+ into the axon causing depolarisation of the axon.

Facilitated diffusion through K+ gated channel allow movement of K+ outside the cell, causing repolarisation of axon

Simple diffusion of Na+ and K+ through membrane of the axon causing region of higher concentration to region with lower concentration, further contributing to depolarization and repolarization.
Neurotransmitter diffusion by simple diffusion to the receptor of post synaptic neurone

Vesicle movement of neurotransmitter: After been activated by Ca2+ ion, phospholipid bilayer of vesicle containing neurotransmitter will fuse with the membrane of pre-synaptic cell and expel the neurotransmitter out of the presynaptic cell into the synaptic cleft.

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Explain the principle of synaptic transmission.
- Once a nerve impulse reaches the pre-synaptic neuron terminal, calcium-gated channels open, allowing calcium ions to enter the neuron.
- This influx of calcium ions causes vesicles containing neurotransmitters to move towards the membrane of the neuron and fuse.
- Exocytosis causes the neurotransmitters in vesicles to diffuse across the synaptic cleft.
- Neurotransmitters bind to receptors on the post-synaptic neuron
- Causes sodium channels to open and sodium ions to enter the post synaptic neuron --> depolarisation occurs
- Neurotransmitters are absorbed back by the pre-synaptic neuron

Outline the use of 4 methods of membrane transport in nerves and synapses.
Active transport
- Sodium potassium pump along the membrane of axons - 3 sodium ions move out, 2 potassium ions move in, requiring ATP.
- Calcium re-uptake by pre-synaptic neutron
- Re-uptake of NTs by pre-synaptic neuron
Facilitated diffusion
Sodium and potassium gated channels cause depolarisation/repolarisation of axon
Calcium gated channel
Exocytosis
Occurs when influx of calcium ions in pre-synaptic neuron causes vesicles containing neurotransmitters to fuse with the membrane and release the NTs towards the post-synaptic neuron.
Simple diffusion
Neurotransmitters diffuse across the synaptic cleft towards the post-synaptic neuron.

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Explain how a nerve impulse passes along a non-myelinated neuron. 

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Explain how a nerve impulse passes along a non-myelinated neuron. 

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Nerve impulses are electrical impulses that travel along the axons of nerve cells (neurons) carrying various information. Propagation of electricity is possible due to differences in electrical potential between the inside of neuron and what is outside. This difference is due to different constitution of positive and negative ions when comparing the inside of neuron and its surroundings;

Resting potential is the time when no impulse is propagated. During the resting potential the inside of neuron is negatively charged (around -70 mV), while the outside matter is positive.

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Explain the principle of synaptic transmission.
- Synaptic transmission is the transfer of neurotransmitters between synaptic neurons.
- As the nerve impulse reaches the pre-synaptic neuron terminal, calcium gated channels in the terminal open, and calcium ions enter the synapse.
- The movement of calcium ions into the cell cause vesicles to fuse with the synapse's membrane.
- Neurotransmitters are released into the synaptic cleft through exocytosis.
- These neurotransmitters will pass through the membrane and bind to receptors on the post-synaptic neuron.
- This causes sodium gated channels to open, and sodium ions enter into the synapse.
- Depolarisation then occurs again, resulting in an action potential passing down the post-synaptic neuron.
- The neurotransmitters are no longer needed and are degraded, along with the calcium ions being pumped out through active transport.

Outline the use of four methods of membrane transport in nerves and synapses.
Active transport
- Can be used to transfer calcium ions out of pre-synaptic neurons.
- Allows for the reabsorption of neurotransmitters after synaptic transmission.
- Resets resting potential through the sodium potassium pump.

Diffusion
- Allows neurotransmitters to diffuse across the synaptic cleft.
-

Vesicles
- Release the neurotransmitters through exocytosis into the synaptic cleft.

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Q1. explain how a nerve impulse pass along a non myelinated neutron                                      Q2. Explain the principle of Synaptic Transmission.

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Q1. explain how a nerve impulse pass along a non myelinated neutron                                      Q2. Explain the principle of Synaptic Transmission.

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Q3. outline the use of four methods of membrane transport in nerve and synapses.

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Explain the principle of synaptic transmission:
- The nerve impulse first reaches the pre synaptic neutron terminal
- It opens the calcium gated channels and depolarization occurs due to an influx in calcium ions
- These calcium ions cause the vesicles to move to the membrane and fuse
- It undergoes exocytosis and neurotransmitters are diffused across the synaptic cleft
- The neurotransmitters then attach to the receptors in the post synaptic neuron and cause the sodium gated channels to open
- This causes the depolarisation of the post synaptic neuron due to an influx of sodium ions
- The neurotransmitters will then be broken down and are absorbed by the the pre-synaptic neuron

Outline the use of four methods of membrane transport in neutron and synapses?
- Active transport is used when calcium ions diffuse out of the calcium gated channels. Also occurs in the sodium potassium pump.
- Vesicle transport: Exocytosis occurs when the calcium ions cause the vesicles in the pre synaptic neutron to fuse with the membrane
- Facilitated diffusion occurs when in the sodium potassium gated channels

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Explain how a nerve impulses passes along a non-myelinated neuron

Neurons are at resting potential -70mv inside the axon terminal is negative, outside is positive

In response to a signal, depolarisation occurs
Influx of sodium ions cause axon terminal to become positive, once it reaches -55mv it causes a large number of sodium ion channels to open, causing a massive influx of sodium ions

Results in an action potential which results in the axon terminal being positively charged to about 30mv

Once 30mv, repolarization occurs

Potassium channels open, causes efflux of potassium ions outside of the axon terminal

Restores negative inner charge of axon

Then the refractory period takes place

Is a period of time where the inside of the axon is slightly more negative than -70mv

Due to rapid efflux of potassium

Resting potential must be restored so sodium potassium channels

Explain the principle of synaptic transmission

Neurotransmitters are chemical messengers released from neurons and function to transmit signals across the synaptic cleft

Released in response to depolarisation of axon terminal of presynaptic neuron

Depolarisation causes the opening of calcium ion channels

Influx of calcium cause vesicles containing the neurotransmitters to bind to the cell membrane

Releasing neurotransmitters into the synaptic cleft

Neurotransmitters bind to receptors on postsynaptic neuron,

Can either by excitatory or inhibitory

Outline the use of four methods of membrane transport in nerves and synapses

Exocytosis
Vesicles containing neurotransmitters

Active transport
Sodium Potassium pumps
Antiporters

Facilitated diffusion
Sodium ion channels
Potassium ion channels
Calcium ion channels

Simple diffusion
potassium ions out of axon terminal

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explain the principle of synaptic transmission (Kano)

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explain the principle of synaptic transmission (Kano)

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1. action potential reaches the terminal axon of pre synaptic neuron.
2.calcium gate open,calcium ions diffuse into the cell.
3.calcium ions cause vesicles move toward the cell membrane.
4.vesicles diffuse neurotransmitters outside the cell into synaptic cleft.
5.neurotransmitters bind to the receptors on the post synaptic neuron.
6.sodium channel open, sodium diffuse into the post synaptic cell.
7.depolarization occur in the post transmitter cell.
8.neurotransmitters are recycled or broke down after attaching to the receptors.

explain the use of four methods of membrane transport  in nerve and synaptic.

active transport:
sodium-potassium pump exchange 3 sodium ions out of the cell and 2 potassium ions into the cell.
neurotransmitters uptake back to pre synaptic neuron.

facilitated transport
potassium channel diffuse potassium out of the cell
calcium channel diffuse calcium into the cell

exocytosis
vesicles diffuse neurotransmitters  into synaptic cleft.

simple diffusion
diffusion of neurotransmitters in synaptic cleft.

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Explain the principle of synaptic transmission (Rhea)

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Explain the principle of synaptic transmission (Rhea)

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1. Nerve impulse reached to the pre-synaptic neuron terminal
2. Depolarisation; calcium gated channels open. There is an influx of calcium positive ions (cations)
3. These positively charged calcium causes vesicles to move to the membrane and fuse
4. The neurotransmitters diffuse across the synaptic cleft
5. The neurotransmitters bind to the receptors present on the post synaptic cleft
6. The sodium gated channel open. This causes depolarisation to occur in the post synaptic neuron.
7. The neurotransmitters are broken and re-absorbed by the presynaptic cleft. Neurotransmitters acetylcholine is broken down into acetate and choline.

Outline the use of four methods of membrane transport in nerves and synapses.

-Vesicle transport (endocytosis & exocytosis): the influx of calcium positively charged ions activates the vesicles in neurotransmitters.

- Active Transport: the presence of the sodium potassium pump. the reuptake of the broken down neurotransmitter in the post synaptic neuron.

- Facilitated Diffusion: in the form of sodium potassium, potassium ion and calcium ion channels. The opening of the sodium ion and potassium ion channels in action potential is through facilitated diffusion. The opening of calcium ion channels in the presynaptic neuron is facilitated diffusion.

-Simple Diffusion: The movement of potassium ions out of the axon in resting potential.

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Explain the principle of synaptic transmission.
- A nerve impulse reaches the terminal knob a neuron.
- The depolarization of the pre-synaptic membrane causes the calcum channels to open
- This will cause an influx of calcium ions to flow into the pre-synaptic neuron.
- When the calcium ions are entering, it will cause the vesicles to move towards the membrane and fuse with it (exocytosis) which releases the neurotransmitters into the synaptic cleft.
- The neurotransmitters then diffuse across the synaptic cleft to the postsynaptic membrane, where they bind with a receptor.
- The sodium gated channel open and there is a depolarization in the post synaptic neuron.
- Neurotransmitters then is absorbed back to the pre synaptic neuron.

Outline the use of four methods of membrane transport in nerves & synapses.
- There are four methods of membrane transport: Active transport, simple diffusion, facilitated diffusion and vesicle transport.
- Active transport occurs in the sodium-potassium pump when it resets the resting potential in the axon.
- There is also active transport that occurs in the pre-synaptic neuron.
- Simple diffusion occurs when the neurotransmitters diffuse across the synaptic cleft.
- Simple diffusion when K ions move out of the axon.
- facilitated diffusing occurs when the calcium gated channels atthe pre-synaptic neuron openes and allows the calcium ions to enter.
-

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Explain the principle of synaptic transmission. (chemical transmission)

1. When the nerve impulses reach the pre synaptic neuron terminal,
2. calcium ion gated channels open and calcium ions enter the pre synaptic neuron, causing depolarisation to occur
3. calcium ions causes vesicles to move to the membrane and fuses with it to release the neurotransmitters in the synaptic cleft.
4. neurotransmitters diffuse across the synaptic cleft to bind with the receptor in the post synaptic neuron.
5. sodium ion gated channel opens, causing sodium ions to enter the post synaptic neurone and hence depolarisation of post synaptic neuron
6.  neurotransmittors broken and absorbed by pre synaptic neuron

Outline the use of four methods of membrane transport in nerves and synapses

Facilitated diffusion:
sodium and potassium ions via sodium and potassium ion gated channel during active potential

Active transport:
sodium and potassium ions via sodium-potassium pump during restoring resting potential

calcium uptake

neurotransmission uptake

Simple diffusion:
Neurotransmitters diffuse across the synaptic cleft

Vesicle Transport:
transport of neurotransmitters within pre synaptic neuron