VCE Biology Question Thread

[grannysmith]

where are neurotransmitters produced? Also, when they bond to the post synaptic.. knob? vessel? (i forgot what its called), does it form an ion channel such that it can pass through via (endocytosis? or diffusion?) to the begging of the next neurone? sorry im a bit muddled.

They can either be synthesised at the pre-synaptic terminal or the cell body (soma) of a neurone, and are packaged into secretory vesicles. Once they are released into the synaptic cleft via exocytosis (from synaptic knob/terminal), they diffuse across the cleft and bind with receptors on the post-synaptic membrane. This activates sodium ion channels, allowing a rapid influx of sodium ions to enter the cell and thus initiate depolarisation.

[soNasty]

Perfect, thanks so much!

[Rishi97]

Explain what happens in signal transduction
Thanks

[katiesaliba]

1) What exactly are the refractory (absolute and relative) periods?
2) Does the hyperpolarisation stage of an action potential conclude with the closing of the potassium channels? If so, what's the name of the stage that occurs after hyperpolarisation, when the neuron's charge returns back to resting potential?
3) Do inhibitory postsynaptic potentials reduce the likelihood of an action potential occuring by lowering the threshold? Is this achieved by opening channels that allow the diffusion of an ion that will further decrease intracellular charge? If so, what ion diffuses into the cell?

I'm asking these questions because I'm curious and prefer to have a strong understanding.

[katiesaliba]

Also, my TSFX notes tell me that interneurons are not myelinated. However, oligodendrocytes are the cells which produce myelin in the CNS...so which cells will be myelinated in the CNS?

[slothpomba]

1) What exactly are the refractory (absolute and relative) periods?
2) Does the hyperpolarisation stage of an action potential conclude with the closing of the potassium channels? If so, what's the name of the stage that occurs after hyperpolarisation, when the neuron's charge returns back to resting potential?
3) Do inhibitory postsynaptic potentials reduce the likelihood of an action potential occuring by lowering the threshold? Is this achieved by opening channels that allow the diffusion of an ion that will further decrease intracellular charge? If so, what ion diffuses into the cell?

I'm asking these questions because I'm curious and prefer to have a strong understanding.

Try yourself first and i'll correct it. I think its a much more beneficial way of learning than being spoonfed. As for TSFX notes, they're kind of notorious for being rubbish in the regard they include a lot you do not need to know to make it seem like its worth it, careful with those (or at least they were when i did biology).

[katiesaliba]

Try yourself first and i'll correct it. I think its a much more beneficial way of learning than being spoonfed. As for TSFX notes, they're kind of notorious for being rubbish in the regard they include a lot you do not need to know to make it seem like its worth it, careful with those (or at least they were when i did biology).

Okay!
1) What exactly are the refractory (absolute and relative) periods?
I know that the absolute refractory period involves depolarisation and repolarisation. Therefore, I presume that during this stage new action potentials cannot occur because of the depolarisation, and thus, the state of the channels (inactivated/activated). The relative refractory period, due to hyperpolarisation, increases the threshold potential needed to instigate an action potential. As a consequence, only stimuli with larger-than-normal potentials can activate action potentials during relative refraction. This that correct?
2) Does the hyperpolarisation stage of an action potential conclude with the closing of the potassium channels? If so, what's the name of the stage that occurs after hyperpolarisation, when the neuron's charge returns back to resting potential?
I think that hyperpolarisation ends with the closing of the potassium channels, and then, during a phase known as afterhyperpolarisation, the membrane potential returns back to its resting state. 
3) Do inhibitory postsynaptic potentials reduce the likelihood of an action potential occuring by lowering the threshold? Is this achieved by opening channels that allow the diffusion of an ion that will further decrease intracellular charge? If so, what ion diffuses into the cell?
I'm pretty sure that inhibitory postsynaptic potentials reduce the likelihood of action potentials from occuring by lowering the threshold. An ion channel, possibly for K+, would open as a result of the inhibitory potential, and reduce the threshold potential by decreasing the intracellular charge.
 
So, does that mean that interneurons can be myelinated?

Thank you

[howlingwisdom]

Explain what happens in signal transduction
Thanks

Signal transduction is the conversion of an external stimulus into one or more internal events through the binding of a hormone/signalling molecule to a specific receptor which triggers a cascade of events in the target cell (like activation of G-proteins and second messenger molecules that amplify the signal) which results in an amplified cellular response.

[Rishi97]

Signal transduction is the conversion of an external stimulus into one or more internal events through the binding of a hormone/signalling molecule to a specific receptor which triggers a cascade of events in the target cell (like activation of G-proteins and second messenger molecules that amplify the signal) which results in an amplified cellular response.

Thanks. But do I really need to remember it in that much detail. Pls say no

[swagsxcboi]

Thanks. But do I really need to remember it in that much detail. Pls say no

yes you do 

[Rishi97]

yes you do 

noooo...soo much to remember

[thushan]

Signal transduction is the conversion of an external stimulus into one or more internal events through the binding of a hormone/signalling molecule to a specific receptor which triggers a cascade of events in the target cell (like activation of G-proteins and second messenger molecules that amplify the signal) which results in an amplified cellular response.

noooo...soo much to remember

Nah, break it down:

Signal transduction - "trans" means to "alter/change" right? So -

- Signal transduction is the conversion of an external stimulus into one or more internal events (in the cell).

Just described what signal transduction is. But how is it done?

- through the binding of a hormone/signalling molecule to a specific receptor which triggers a cascade of events in the target cell

and what does this cascade lead to?

- which results in an amplified cellular response.

There you go, piece of cake.

[alondouek]

noooo...soo much to remember

It's not so bad! Lets see if I can whip up an analogy.

In Ancient Greece, there obviously weren't any telephones or social media etc. to keep people in contact via communication. However, because the Greeks were often in conflict with some empire or another, e.g. the Persian empire, they needed a way of getting messages from one place to multiple other places by land. In order to do this, there would be a network of messengers who would run to a point and deliver the message to a group of other messages, who would carry the original message to their intended target. The messenger who was given the initial message wouldn't continue on after he'd passed the message to the other messengers. Once the message has been passed on the recipients, the Greeks would be able to carry out some action as dictated by the message.

This is, in essence, what signal transduction is all about. We have an initial messenger that carries a signal to a cell, where it is received and passed on to a secondary messenger, which can then take the "message" (or signal) to target areas of the cell interior. From there, a cellular response to the initial stimulus can be performed. Note that the initial messenger never enters the cell. The rest is just filling in the required biological terminology!

[Rishi97]

It's not so bad! Lets see if I can whip up an analogy.

In Ancient Greece, there obviously weren't any telephones or social media etc. to keep people in contact via communication. However, because the Greeks were often in conflict with some empire or another, e.g. the Persian empire, they needed a way of getting messages from one place to multiple other places by land. In order to do this, there would be a network of messengers who would run to a point and deliver the message to a group of other messages, who would carry the original message to their intended target. The messenger who was given the initial message wouldn't continue on after he'd passed the message to the other messengers. Once the message has been passed on the recipients, the Greeks would be able to carry out some action as dictated by the message.

This is, in essence, what signal transduction is all about. We have an initial messenger that carries a signal to a cell, where it is received and passed on to a secondary messenger, which can then take the "message" (or signal) to target areas of the cell interior. From there, a cellular response to the initial stimulus can be performed. Note that the initial messenger never enters the cell. The rest is just filling in the required biological terminology!

You are a legend!!!! Thank you for taking time to write this up for me.
Thanks heaps

[Rishi97]

Explain why a second messenger is needed to convey a signal inside a cell from a water soluble first messenger.