VCE Biology Question Thread

[vox nihili]

I have a few questions...wondering if someone can answer them.
- What is the difference between refractory period and resting state?
- Is the undershoot in the action potential graph the refractory period?
- Why is there an undershoot?
- Define action potential.

1. Resting state (more commonly resting potential) is what the cell's membrane potential is at when it's all normal. In the "resting state" the cell can depolarise. The refractory period, on the other hand, is the short time after the conclusion of an action potential during which a cell can't deploarise again.

2. Yes

3. Complicated, you don't need to know in VCE. In a "why is it good" sort of way, it's about ensuring that the action potential goes in the one direction.

4. You could just as easily google this.

[mtDNA]

I just wanted to clarify:

Does humoral and cellular immunity occur separately, or in conjunction?

I'm pretty sure it's in conjunction seeing that you need the Th cell to allow for clonal expansion in B cells, but I just wanted to check if these processes could ever occur separately...

Also, I have read that NK cells act like Tc cells in which they release perforin to allow for virally infected cells to lyse. The thing is - by causing lysis in the virally infected cell, wouldn't that just allow for the replication of viruses and allow them to "live"? I could see how this could be effective for preventing tumour growth and infection of other pathogens, but not viruses...

Thanks in advance

[gameboy99]

Out of curiosity, What is the role of cAMP phosphodiesterase in signal transduction???

[vox nihili]

I just wanted to clarify:

Does humoral and cellular immunity occur separately, or in conjunction?

I'm pretty sure it's in conjunction seeing that you need the Th cell to allow for clonal expansion in B cells, but I just wanted to check if these processes could ever occur separately...

Also, I have read that NK cells act like Tc cells in which they release perforin to allow for virally infected cells to lyse. The thing is - by causing lysis in the virally infected cell, wouldn't that just allow for the replication of viruses and allow them to "live"? I could see how this could be effective for preventing tumour growth and infection of other pathogens, but not viruses...

Thanks in advance

In conjunction. Basically, everything you've learned about in immunology occurs at the same time. Perhaps the biggest failure of the VCE course is the fact that it doesn't make it clear that, in fact, they're all interconnected. For instance, without innate immunity, you simply wouldn't have adaptive. Also, adaptive immunity helps to enhance innate immunity and may actually work with it in some cases. They're not separate process. The body's not that simple!

Viruses leave cells when they've been properly assembled and are ready to leave. NK cells and Tc cells kill them before they've prepared for the journey, as it were. Think about what viruses need to grow and get around and it should make sense to you.

[vox nihili]

Out of curiosity, What is the role of cAMP phosphodiesterase in signal transduction???

Hmmm probably a bit complicated for VCE. cAMP is a common second messenger, therefore phosphodiesterases basically turn off the intracellular signalling.

[geminii]

What are the differences between dendrites and synapses? (Apart from dendrites receiving a signal and the synapses passing the signal on to the next neuron's dendrite.) Are they made of different things, are they structured differently? Just curious! Thanks

[vox nihili]

What are the differences between dendrites and synapses? (Apart from dendrites receiving a signal and the synapses passing the signal on to the next neuron's dendrite.) Are they made of different things, are they structured differently? Just curious! Thanks

I think you're confused between axon and synapse.

Dendrites receive signals and axons transmit them to the next neurone. The junction between two neurones is referred to as the synapse.

As far as dendrites and axons are concerned, yes they are structured differently, although they are made of basically the same parts (on a molecular level there are some differences though)

[geminii]

I think you're confused between axon and synapse.

Dendrites receive signals and axons transmit them to the next neurone. The junction between two neurones is referred to as the synapse.

As far as dendrites and axons are concerned, yes they are structured differently, although they are made of basically the same parts (on a molecular level there are some differences though)

Ah, thanks! But I thought the other end of the neuron is called a synapse, and the gap is called the synaptic terminal? That's what we learnt at school today, anyway.

[plsbegentle]

Ah, thanks! But I thought the other end of the neuron is called a synapse, and the gap is called the synaptic terminal? That's what we learnt at school today, anyway.

The synapse is basically the junction between two neurons.
A neuron one end has dendrites which receive information while the other end; axon carries information away. When ur talking about synaptic terminal, do u mean axon terminal?
Go on google images and type in synapse or neurotransmitter should give u a good understanding

[vox nihili]

Ah, thanks! But I thought the other end of the neuron is called a synapse, and the gap is called the synaptic terminal? That's what we learnt at school today, anyway.

The gap itself is called the synaptic cleft.

The pre-synaptic terminal is the axon, and the post-synaptic terminal is the dendrite. A synapse is all three of those structures basically. The very tips of the dendrites and the axons, plus the gap in between.

[geminii]

When ur talking about synaptic terminal, do u mean axon terminal?

Yes, my teacher said we could use them interchangeably.

The gap itself is called the synaptic cleft.

The pre-synaptic terminal is the axon, and the post-synaptic terminal is the dendrite. A synapse is all three of those structures basically. The very tips of the dendrites and the axons, plus the gap in between.

Oh, ok, I see. I'll search up some pictures on google to help me get it!

[vox nihili]

Yes, my teacher said we could use them interchangeably.

Oh, ok, I see. I'll search up some pictures on google to help me get it!

Strictly speaking, this is not correct. Both axons and dendrites can form synaptic terminals, pre and post respectively.

[vox nihili]

Is this correct?
Thyroxine is amine based, but is hydrophobic and acts that way (alters gene transcription).

yep

[anniebrejcha]

hi hi hi!

would someone be able to explain the purpose of myelin to me? i've been told so many different things for such a long time and really just need a definite answer asides from the textbook one.
thanks in advance guys!

[cosine]

hi hi hi!

would someone be able to explain the purpose of myelin to me? i've been told so many different things for such a long time and really just need a definite answer asides from the textbook one.
thanks in advance guys!

For some context: Myelin sheath is the insulation that is produced by two specific types of cells in the Nervous System. In the Peripheral Nervous System (PNS), cells known as Schwann cells produce this myelin sheath and wrap it around the axon of the neurones. In the Central Nervous System (CNS), oligodendocrytes are the cells that myelinate the neurones in the spinal cord and brain, in other words, the interconnecting neurones are myelinated by oligodendrocytes. Anyways myelin sheath a protein coating that provides insulation to the neurones and consequentially speeds up the propagation of the electrical message during the action potential. This is why myelinated neurones transmit messages faster than unmyelinated neurones. In fact, snails do not have myelinated neurones, which contributes to their very slow movement and responses to their environment.