Biology nervous system and microscope

Practice Question Solving
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Hey guys! I would like to ask a few questions which confuse me when I was reviewing the lessons.

The first question is about the factors which influence the rate of nervous system AP transmission. Having Myelin and larger diameter helps increase the rate of impulse transmission. So how abt increasing the axon length? Does it decrease the rate as the axon becomes longer and there is more resistance in the dimensions?

The second question is about the structures which can be seen under the light microscope. Can we see centrioles and lysosomes when we are viewing the cells under the optics microscope?

Can someone please clarify my doubts? Thank you very much in advance :heart:!

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hi! great questions!

  1. i’m assuming you’re referring to IMAT 2011 Q 56, this is Ari’s worked answer:
    “The longer the axon, the faster the transmission will go, imagine it like a waterfall, if the top of the waterfall is higher, the water that falls will have a much quicker velocity with the help of the acceleration, so this one does help the speed of transmission.”

i’m not sure about 2)

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Hey Stella!

For the second question, I think only the largest structures are visible under the light microscope, which include the nucleus, chloroplasts, mitochondria, cell membrane, cell wall, cytoplasm and sometimes large vacuoles. Lysosomes and centrioles are already too small, so we would need an electron microscope for that:)

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Hey Juliette! Thank you very much for the clear explanation! I thought I remember having seen the question somewhere but did not exactly remember where , thats why I was a bit confused. I understand clearly now :ok_woman:t2:🫶🏻 thanks a lot !!

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Hey!
completely agree with you but i think there must be some exceptions to watch out for, lysosomes can be used to destroy and recycle other organelles such as mitochondrias, or even entire cells for macrophages, i feel like we could see that under a light microscope?
also anything the size of a protein can’t be seen as it’s too small, but i think we can see secretory vesicles under a light microscope (ex: eosinophils)

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Thank you very much Darius !! I came across a question where they said lysosomes are visible and thats why I was very confused. Thanks again for the clarification !

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Hahaha that happens to me all the time! you can look up key words in the searchbar to see if anyone has posted the solution on here, it usually works :smile:

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Thanks for your information :ok_woman:t2::two_hearts:, I will try it next time :joy:

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I looked a little into those structures and it appears that lysosomes, even though they can destroy the whole mitochondrion, arent normally visible under a light microscope. Lysosomes destroy organelles by fusing their membrane with the other organelle membrane (if the organelle has one - bigger organelles usually) and secreting a mix of hydrolytic enzymes that break down the structure.

Secretory vesicles are also quite small to be honest, the thing we can see in eosinophils is the double-lobed nucleus and many many granules (which are the storage of glycogen, lipid or protein). Hope this makes sense, if someone finds a better explanation please share:)

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Yes! I did practicals when I was in school using a light microscope and an electron microscope. Larger structures can be IDENTIFIED using a light microscope but I saw multiple little “dots” which my teacher told me were most likely lysosomes that are fused with something else or granules however it’s hard to determine it. due to the size.

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Thank you very much for the contributed answer Raya!! Appreciate your explanation a lot :heart_eyes_cat::two_hearts:

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