Med school question

[h2266]

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Hey guys, I don't quite understand the concept of interneurons and 1st, 2nd, 3rd order neurons.

This is what I gathered after doing some revision. Could someone please correct and help me with the problems I faced below?

From the image below, I gathered that the first order neuron, the second order neuron and the the third order neuron are all sensory neurons. But isn't there only one sensory neuron?

From the images below, I gathered that the interneuron connects the sensory neuron to the motor neuron.
But then what about the first, second. third order neurons - why aren't they present here? How come they don't have any role here?

I am struggling to put interneurons and 1st,2nd, 3rd order neurons on the same page. Whenever interneurons are being explained on a youtube vid, the 1st,2nd, 3rd order neurons are never mentioned. I am not really sure how they are related and the differences between them. Therefore, I find it hard to connect the sensory neuron, the 1st, 2nd, 3rd order neurons, the interneuons and motor neuron and therefore the pathway of a signal. It almost feels like I don't fully understand the function of each one of them and that I only have a very basic idea 🙁

Would really appreciate if someone could help and try to make this clearer for me

 

[libertyyne]

first second and third only refer to specific modality of pathway, sensory or motor. Interneurons are not part of those pathways rather link the two together.

Its like having two one way streets running in opposite and parallel directions, one is sensory and one is motor. The interneurons would be the side street joining the two.

 

[7331poas]

boards and beyond or kaplan neuroscience

 

[h2266]

first second and third only refer to specific modality of pathway, sensory or motor. Interneurons are not part of those pathways rather link the two together.

Its like having two one way streets running in opposite and parallel directions, one is sensory and one is motor. The interneurons would be the side street joining the two.

Hi! Thank so much for your reply! 🙂

I think I see what you mean.

However, doesn't modality mean the type of sensory information being carried i.e. somatosensory or viscerosensory? Tbh, I still don't quite the concept of modality 🙁

Below is my attempt at trying to explain the pathway of a signal. Could you please possibly correct or maybe add to what I've wriiten? there are some things I don't get and it is in brackets with purple font.

There is a stimulus e.g. touch. Sensory receptor (What is the Sensory receptor? Is it the dendrites and dendrons of the sensory neuron or is it something completely different) detects it in the peripheral area (the skin) and passes it onto the sensory neuron ( I am not exactly sure how a signal is passed from a sensory receptor to a sensory neuron - Ik I should know this 🙁 I don't think it is via a synapse because when I think about it,.. a sensory receptor doesn't really have axons,dendrites, dendrons or a cell body,..so how could there even by a synapse between a sensory receptor and sensory neuron to pass on a signal? Or maybe chemicals are released? A diagram would help lmao but can't find a good one atm. I hate guessing :/)..

...Ok anyways, the dendron of the sensory neuron goes to the cell body located in the dorsal root ganglion. The dendron synapses with that cell body.

This is the point where I would then start to mention the 1st order neuron... and how the sensory neuron connects with the 1st order neuron. However, I am struggling to do so, because the cell body of the first order neuron is located in the dorsal root ganglion. So where is the cell body of the sensory neuron located? I apologise for my ignorance!

Sorry for taking so long to reply back - the notification thingamajig wasn't working lol

 

[h2266]

bump

 

[kraskadva]

I'm just gonna insert bold text to keep Q/A straight..
QUOTE="h2266, post: 21108540, member: 997380"
Hi! Thank so much for your reply! 🙂

I think I see what you mean.

However, doesn't modality mean the type of sensory information being carried i.e. somatosensory or viscerosensory? Tbh, I still don't quite the concept of modality 🙁

Stimulus modality - Wikipedia

en.wikipedia.org

Basically, sensory receptors are coded to recognize specific things (hot, cold, pain, light, sound, etc, etc.) Doesn't matter if you stimulate i.e. a heat-sensitive receptor with heat or induced depolarization, your brain will read it as "hot", never as cold or pain

Below is my attempt at trying to explain the pathway of a signal. Could you please possibly correct or maybe add to what I've wriiten? there are some things I don't get and it is in brackets with purple font.

There is a stimulus e.g. touch. Sensory receptor (What is the Sensory receptor? The end of a primary sensory neuron. See 2nd/3rd pics below. Is it the dendrites yes and dendrons not a thing of the sensory neuron or is it something completely different) detects it in the peripheral area (the skin) and passes it onto the sensory neuron doesn't "pass it onto" bc they're not separate entities. the receptor is depolarized, signal is propagated down the dendrite to the cell body and around to the axon hillock. If enough dendrites are being depolarized/signal is strong enough at axon hillock, then the signal is propagated down the axon. At the end of the axon, neurotransmitters are released into the synapse with the next nerve in line.( I am not exactly sure how a signal is passed from a sensory receptor to a sensory neuron - Ik I should know this 🙁 I don't think it is via a synapse because when I think about it,.. a sensory receptor doesn't really have axons,dendrites, dendrons or a cell body,..so how could there even by a synapse between a sensory receptor and sensory neuron to pass on a signal? There's not a synapse here (usually, exception discussed below). See previous comment. Or maybe chemicals are released? A diagram would help lmao but can't find a good one atm. 2nd/3rd pics I hate guessing :/)..

...Ok anyways, the dendron dendrite of the sensory neuron goes to the cell body located in the dorsal root ganglion. The dendron synapses Not a synapse, just different parts of the same cell with that cell body.

This is the point where I would then start to mention the 1st order neuron... and how the sensory neuron connects with the 1st order neuron.Sensory neuron *is* the 1st order neuron. See 1st pic However, I am struggling to do so, because the cell body of the first order neuron is located in the dorsal root ganglion. So where is the cell body of the sensory neuron located? I apologise for my ignorance!

Sorry for taking so long to reply back - the notification thingamajig wasn't working lol
For orientation, in this pic, blobs/stars on side/end of diagrammed neurons indicate the location of the cell body. If it's at the end, know that there *are* dendrites, they're just very short.

1st order, aka sensory, neurons run from receptor (dendrite end of the cell) to spinal cord (axon end) where they synapse with a 2nd order neuron (level dependant on specific type of sensory neuron)
2nd order neuron (still sensory) decussates (i.e. crosses over) in either the spinal cord or brain stem (dependant on specific type of 1st order sensory neuron) Synapse between 1' and 2' neurons is the axon of the 1' and dendrite of the 2'. Axons of 2' neurons are all in the thalamus where they synapse (axon of 2', dendrite of 3') with a 3' neuron that goes to the cortex. Info is processed there, signal is passed from sensory to motor cortex for response.
@libertyyne 's analogy of one way streets and side streets is a good one here. The sensory pathway is a one way street from receptor to cortex. Motor is a separate one way street from cortex to muscle/end organ. There are multiple side streets - in the cortex between sensory and motor, in the spinal cord through interneurons (this is specifically for reflexes) and a couple other places you don't need to worry about now.

A & B here would be examples of skin receptors. Gut or muscle stretch receptors are similar setups.
C would be in the eye (and the exception to the receptor not being a direct continuation of the 1' neuron, but instead a separate cell)
D would be the hair fibers in the ear

Lots of options for skin receptors. Everything pictured here falls under the B category above, except free nerve endings, which would be A

Motor is it's own thing. There can be 2 or 3 neurons in the pathway. If it starts in the cortex, it's an upper motor neuron. If it starts in the spinal cord or peripherally, then it's a lower motor neuron. Again, side streets exist both within the cortex and in the spinal cord to connect sensory to motor.
Below are variations on how the LMNs can be arranged, depending on the type of motor we're talking about.

The pictures you have above with interneurons are specifically for reflexes - i.e. things that happen before you can think about/process the sensory info in your cortex. It's a short circuit to let the body prevent damage. These happen with stretch receptors in the deep tendons (like every time you had your knee tapped with a hammer by a doc and kicked out before you consciously felt it) and with some other types of receptors (heat - snatch your hand back from a stove before getting badly burned, gag reflexes from uvula, cough reflexes from bronco cilia, etc)

Does that help clear it up for you?

 

[h2266]

I'm just gonna insert bold text to keep Q/A straight..
QUOTE="h2266, post: 21108540, member: 997380"
Hi! Thank so much for your reply! 🙂

I think I see what you mean.

However, doesn't modality mean the type of sensory information being carried i.e. somatosensory or viscerosensory? Tbh, I still don't quite the concept of modality 🙁

Stimulus modality - Wikipedia

en.wikipedia.org

Basically, sensory receptors are coded to recognize specific things (hot, cold, pain, light, sound, etc, etc.) Doesn't matter if you stimulate i.e. a heat-sensitive receptor with heat or induced depolarization, your brain will read it as "hot", never as cold or pain

Below is my attempt at trying to explain the pathway of a signal. Could you please possibly correct or maybe add to what I've wriiten? there are some things I don't get and it is in brackets with purple font.

There is a stimulus e.g. touch. Sensory receptor (What is the Sensory receptor? The end of a primary sensory neuron. See 2nd/3rd pics below. Is it the dendrites yes and dendrons not a thing of the sensory neuron or is it something completely different) detects it in the peripheral area (the skin) and passes it onto the sensory neuron doesn't "pass it onto" bc they're not separate entities. the receptor is depolarized, signal is propagated down the dendrite to the cell body and around to the axon hillock. If enough dendrites are being depolarized/signal is strong enough at axon hillock, then the signal is propagated down the axon. At the end of the axon, neurotransmitters are released into the synapse with the next nerve in line.( I am not exactly sure how a signal is passed from a sensory receptor to a sensory neuron - Ik I should know this 🙁 I don't think it is via a synapse because when I think about it,.. a sensory receptor doesn't really have axons,dendrites, dendrons or a cell body,..so how could there even by a synapse between a sensory receptor and sensory neuron to pass on a signal? There's not a synapse here (usually, exception discussed below). See previous comment. Or maybe chemicals are released? A diagram would help lmao but can't find a good one atm. 2nd/3rd pics I hate guessing :/)..

...Ok anyways, the dendron dendrite of the sensory neuron goes to the cell body located in the dorsal root ganglion. The dendron synapses Not a synapse, just different parts of the same cell with that cell body.

This is the point where I would then start to mention the 1st order neuron... and how the sensory neuron connects with the 1st order neuron.Sensory neuron *is* the 1st order neuron. See 1st pic However, I am struggling to do so, because the cell body of the first order neuron is located in the dorsal root ganglion. So where is the cell body of the sensory neuron located? I apologise for my ignorance!

Sorry for taking so long to reply back - the notification thingamajig wasn't working lol
For orientation, in this pic, blobs/stars on side/end of diagrammed neurons indicate the location of the cell body. If it's at the end, know that there *are* dendrites, they're just very short.
View attachment 273858
1st order, aka sensory, neurons run from receptor (dendrite end of the cell) to spinal cord (axon end) where they synapse with a 2nd order neuron (level dependant on specific type of sensory neuron)
2nd order neuron (still sensory) decussates (i.e. crosses over) in either the spinal cord or brain stem (dependant on specific type of 1st order sensory neuron) Synapse between 1' and 2' neurons is the axon of the 1' and dendrite of the 2'. Axons of 2' neurons are all in the thalamus where they synapse (axon of 2', dendrite of 3') with a 3' neuron that goes to the cortex. Info is processed there, signal is passed from sensory to motor cortex for response.
@libertyyne 's analogy of one way streets and side streets is a good one here. The sensory pathway is a one way street from receptor to cortex. Motor is a separate one way street from cortex to muscle/end organ. There are multiple side streets - in the cortex between sensory and motor, in the spinal cord through interneurons (this is specifically for reflexes) and a couple other places you don't need to worry about now.
View attachment 273859
A & B here would be examples of skin receptors. Gut or muscle stretch receptors are similar setups.
C would be in the eye (and the exception to the receptor not being a direct continuation of the 1' neuron, but instead a separate cell)
D would be the hair fibers in the ear
View attachment 273860
Lots of options for skin receptors. Everything pictured here falls under the B category above, except free nerve endings, which would be A

View attachment 273861
Motor is it's own thing. There can be 2 or 3 neurons in the pathway. If it starts in the cortex, it's an upper motor neuron. If it starts in the spinal cord or peripherally, then it's a lower motor neuron. Again, side streets exist both within the cortex and in the spinal cord to connect sensory to motor.
Below are variations on how the LMNs can be arranged, depending on the type of motor we're talking about.

View attachment 273863

The pictures you have above with interneurons are specifically for reflexes - i.e. things that happen before you can think about/process the sensory info in your cortex. It's a short circuit to let the body prevent damage. These happen with stretch receptors in the deep tendons (like every time you had your knee tapped with a hammer by a doc and kicked out before you consciously felt it) and with some other types of receptors (heat - snatch your hand back from a stove before getting badly burned, gag reflexes from uvula, cough reflexes from bronco cilia, etc)

Does that help clear it up for you?

Ah thank you so much for your time and help!! 🙂 🙂 🙂Honestly, this is amazing stuff and things are so much more clearer now! Really really appreciate this!
I should actyually be sleeping as it is currently 4:30 am where I am at lol. Actually on that note, I think I am going to bed 🙂 I am going to read over this again when I wake up and keep you posted if I have any other questions - hopefully I won't yikes.

Once again, thank you so much!!! mEans a lot!

 

[h2266]

I'm just gonna insert bold text to keep Q/A straight..
QUOTE="h2266, post: 21108540, member: 997380"
Hi! Thank so much for your reply! 🙂

I think I see what you mean.

However, doesn't modality mean the type of sensory information being carried i.e. somatosensory or viscerosensory? Tbh, I still don't quite the concept of modality 🙁

Stimulus modality - Wikipedia

en.wikipedia.org

Basically, sensory receptors are coded to recognize specific things (hot, cold, pain, light, sound, etc, etc.) Doesn't matter if you stimulate i.e. a heat-sensitive receptor with heat or induced depolarization, your brain will read it as "hot", never as cold or pain

Below is my attempt at trying to explain the pathway of a signal. Could you please possibly correct or maybe add to what I've wriiten? there are some things I don't get and it is in brackets with purple font.

There is a stimulus e.g. touch. Sensory receptor (What is the Sensory receptor? The end of a primary sensory neuron. See 2nd/3rd pics below. Is it the dendrites yes and dendrons not a thing of the sensory neuron or is it something completely different) detects it in the peripheral area (the skin) and passes it onto the sensory neuron doesn't "pass it onto" bc they're not separate entities. the receptor is depolarized, signal is propagated down the dendrite to the cell body and around to the axon hillock. If enough dendrites are being depolarized/signal is strong enough at axon hillock, then the signal is propagated down the axon. At the end of the axon, neurotransmitters are released into the synapse with the next nerve in line.( I am not exactly sure how a signal is passed from a sensory receptor to a sensory neuron - Ik I should know this 🙁 I don't think it is via a synapse because when I think about it,.. a sensory receptor doesn't really have axons,dendrites, dendrons or a cell body,..so how could there even by a synapse between a sensory receptor and sensory neuron to pass on a signal? There's not a synapse here (usually, exception discussed below). See previous comment. Or maybe chemicals are released? A diagram would help lmao but can't find a good one atm. 2nd/3rd pics I hate guessing :/)..

...Ok anyways, the dendron dendrite of the sensory neuron goes to the cell body located in the dorsal root ganglion. The dendron synapses Not a synapse, just different parts of the same cell with that cell body.

This is the point where I would then start to mention the 1st order neuron... and how the sensory neuron connects with the 1st order neuron.Sensory neuron *is* the 1st order neuron. See 1st pic However, I am struggling to do so, because the cell body of the first order neuron is located in the dorsal root ganglion. So where is the cell body of the sensory neuron located? I apologise for my ignorance!

Sorry for taking so long to reply back - the notification thingamajig wasn't working lol
For orientation, in this pic, blobs/stars on side/end of diagrammed neurons indicate the location of the cell body. If it's at the end, know that there *are* dendrites, they're just very short.
View attachment 273858
1st order, aka sensory, neurons run from receptor (dendrite end of the cell) to spinal cord (axon end) where they synapse with a 2nd order neuron (level dependant on specific type of sensory neuron)
2nd order neuron (still sensory) decussates (i.e. crosses over) in either the spinal cord or brain stem (dependant on specific type of 1st order sensory neuron) Synapse between 1' and 2' neurons is the axon of the 1' and dendrite of the 2'. Axons of 2' neurons are all in the thalamus where they synapse (axon of 2', dendrite of 3') with a 3' neuron that goes to the cortex. Info is processed there, signal is passed from sensory to motor cortex for response.
@libertyyne 's analogy of one way streets and side streets is a good one here. The sensory pathway is a one way street from receptor to cortex. Motor is a separate one way street from cortex to muscle/end organ. There are multiple side streets - in the cortex between sensory and motor, in the spinal cord through interneurons (this is specifically for reflexes) and a couple other places you don't need to worry about now.
View attachment 273859
A & B here would be examples of skin receptors. Gut or muscle stretch receptors are similar setups.
C would be in the eye (and the exception to the receptor not being a direct continuation of the 1' neuron, but instead a separate cell)
D would be the hair fibers in the ear
View attachment 273860
Lots of options for skin receptors. Everything pictured here falls under the B category above, except free nerve endings, which would be A

View attachment 273861
Motor is it's own thing. There can be 2 or 3 neurons in the pathway. If it starts in the cortex, it's an upper motor neuron. If it starts in the spinal cord or peripherally, then it's a lower motor neuron. Again, side streets exist both within the cortex and in the spinal cord to connect sensory to motor.
Below are variations on how the LMNs can be arranged, depending on the type of motor we're talking about.

View attachment 273863

The pictures you have above with interneurons are specifically for reflexes - i.e. things that happen before you can think about/process the sensory info in your cortex. It's a short circuit to let the body prevent damage. These happen with stretch receptors in the deep tendons (like every time you had your knee tapped with a hammer by a doc and kicked out before you consciously felt it) and with some other types of receptors (heat - snatch your hand back from a stove before getting badly burned, gag reflexes from uvula, cough reflexes from bronco cilia, etc)

Does that help clear it up for you?

Hi again 🙂 Most of what I was struggling to understand has been cleared up but just have a few questions. Once again, thank you so much for your help and no worries at all if you are busy🙂

I have highlighted a part in the pic below. Aren't axons efferent nerve fibres and dendrites afferent nerve fibres? I understand that dendrites are sensory receptors but they are also afferent nerve fibres, right?

In regards to modality, this is what I gathered after some revision and using the wikipedia link you kindly added: Could you please kindly correct my errors?

For sensory modality, you can't have somatosensory or viscerosensory as a type of sensory modality,..because these refer to the location that the sensory info has been taken from... Somatosensory (sensory info from muscles), Viscerosensory (sensory info from organs) #Actually, I feel something is not right here tbh!

Sensory modality is the type of sensory information being carried. e.g. light, sound, taste, temperature, pressure & smell,..so light sensory info, sound sensory info, smell sensory info etc...

Crude touch and Fine touch are also sensory modalities.

Fine touch = can sense the touch sensation and locate where the touch sensation is on your skin (not touch sensation in body or on internal organs #also not sure what sensation/ modality that would be?)

Crude touch = can sense the touch sensation but cannot locate where the touch sensation is on your skin

So there are sensory neurons specific for fine touch and there are sensory neurons specific for crude touch right?

About the image above: could you please highlight any further mistakes and kindly let me know your thoughts about some questions below?

The upper motor neuron starts in the cortex and its pathway is always downwards like in the image shown - red arrow.

The lower motor neuron starts in the periphery (outside the brain & spinal cord) or the spinal cord and its pathway is always to the periphery - green arrow.

Also, how can a motor neuron start in the periphery? I am always so used to the cell body of a motor neuron being in the spinal cord. Is there a diagram which could highlight a motor neuron starting in the periphery?

In regards to motor modality:..

How can there be motor modality of a pathway of a signal ( I think this is what libertyyne highlighted in their post)? I though it was just for sensory that you have the modalities.

And also what are the types of motor modalities? You kindly mentioned the upper motor neuron & the lower motor neuron - are these to do with the motor modality? What I mean is that for sensory modality we have pressure, touch, taste etc but not for motor modality.

Thank you so so much! Apologies for asking so many silly questions!
Really appreciate your help and no worries at all if you are busy with other things 🙂

 

[h2266]

bump

 

[sella.turcica]

I don't think you're asking silly questions, just basic questions. You need to do your homework on your own. Get a good neurophysiology book and you'll be fine.

 

[kraskadva]

I don't think you're asking silly questions, just basic questions. You need to do your homework on your own. Get a good neurophysiology book and you'll be fine.

@h2266 I don't disagree with this...

For the kind of questions you're asking, this book may actually be a good place to start...
Amazon product ASIN 0064603067
Give me a hot minute though and I'll go through your last set of questions

 

[kraskadva]

Going with bold text again...
QUOTE="h2266, post: 21109907, member: 997380"
Hi again 🙂 Most of what I was struggling to understand has been cleared up but just have a few questions. Once again, thank you so much for your help and no worries at all if you are busy🙂

I have highlighted a part in the pic below. Aren't axons efferent nerve fibres and dendrites afferent nerve fibres? I understand that dendrites are sensory receptors but they are also afferent nerve fibres, right?
Afferent means "moving in/towards" Efferent means "moving out/away from". These terms can be applied at all levels of the nervous system (single cell to whole nerve/tract) to indicate direction of conductance.
Nerve fibers are collections of axons. A/Efferent is applied in regards to whether they are transmitting towards/away from the brain. So sensory nerve fibers are afferent, motor are efferent. (clicking on those blue hyperlinks in wikipedia can answer a lot of this)

Afferent nerve fiber - Wikipedia

en.wikipedia.org

Efferent nerve fiber - Wikipedia

en.wikipedia.org

Dendrites (while they include sensory receptors as a subtype) are just the recieving end of the neuron.

View attachment 273882

In regards to modality, this is what I gathered after some revision and using the wikipedia link you kindly added: Could you please kindly correct my errors?

For sensory modality, you can't have somatosensory or viscerosensory as a type of sensory modality,..because these refer to the location that the sensory info has been taken from... Somatosensory (sensory info from muscles body, including muscles, skin, etc.), Viscerosensory (sensory info from organs) correct. those are big broad categories. theres also special sensory (vision, taste, hearing, proprioception, etc) #Actually, I feel something is not right here tbh!

Sensory modality is the type of sensory information being carried. e.g. light, sound, taste, temperature, pressure & smell,..so light sensory info, sound sensory info, smell sensory info etc...yes

Crude touch and Fine touch are also sensory modalities.yes

Fine touch = can sense the touch sensation and locate where the touch sensation is on your skin yes, go look up which receptors are for this (not touch sensation in body or on internal organs correct #also not sure what sensation/ modality that would be?)mostly just stretch. no receptors for touch, cut, crush, or burn in the organs.

Crude touch = can sense the touch sensation but cannot locate where the touch sensation is on your skin sense deep pressure or vibration. can tell if it's on say, your distal anterior forearm to within half a centimeter or so, but not which milli- or micrometer of skin.

So there are sensory neurons specific for fine touch and there are sensory neurons specific for crude touch right? yep

View attachment 273887yeah. those are just some basic examples listed in the yellow bubbles. which category if falls into is dependant on type of receptor/sensory neuron

View attachment 273891not sure what your question is here. both arrows (as I read it) are indicating LMNs - they're the ones that start in the spinal cord and go to the muscle or other end organ.

About the image above: could you please highlight any further mistakes and kindly let me know your thoughts about some questions below?

The upper motor neuron starts in the cortex and its pathway is always downwards like in the image shown - red arrow. ah, I see. yes, that's correct

The lower motor neuron starts in the periphery (outside the brain & spinal cord) or the spinal cord and its pathway is always to the periphery - green arrow. 1st LMN always starts in the spinal cord. Sometimes there's a 2nd one that starts in the periphery.

Also, how can a motor neuron start in the periphery? I am always so used to the cell body of a motor neuron being in the spinal cord. Is there a diagram which could highlight a motor neuron starting in the periphery? search ganglion. follow the hyperlinks...

Ganglion - Wikipedia

en.wikipedia.org

In regards to motor modality:..

How can there be motor modality of a pathway of a signal ( I think this is what libertyyne highlighted in their post)? I though it was just for sensory that you have the modalities.

View attachment 273892
"...specific modality of pathway, ^whether^ sensory or motor..."
Sympathetic, parasympathetic, somatic - could all be termed modalities, but we just talk about them as pathways
And also what are the types of motor modalities? ^ You kindly mentioned the upper motor neuron & the lower motor neuron - are these to do with the motor modality? no What I mean is that for sensory modality we have pressure, touch, taste etc but not for motor modality.Sympathetic, parasympathetic, somatic

Thank you so so much! Apologies for asking so many silly questions!
Really appreciate your help and no worries at all if you are busy with other things 🙂

What class are you studying for? What books/resources are you using? I get that this can all be confusing on 1st pass, but all of this is laid out in any textbook on the topic, even in wikipedia (when you folllow enough hyperlinks 😉).

 

[h2266]

Going with bold text again...
QUOTE="h2266, post: 21109907, member: 997380"
Hi again 🙂 Most of what I was struggling to understand has been cleared up but just have a few questions. Once again, thank you so much for your help and no worries at all if you are busy🙂

I have highlighted a part in the pic below. Aren't axons efferent nerve fibres and dendrites afferent nerve fibres? I understand that dendrites are sensory receptors but they are also afferent nerve fibres, right?
Afferent means "moving in/towards" Efferent means "moving out/away from". These terms can be applied at all levels of the nervous system (single cell to whole nerve/tract) to indicate direction of conductance.
Nerve fibers are collections of axons. A/Efferent is applied in regards to whether they are transmitting towards/away from the brain. So sensory nerve fibers are afferent, motor are efferent. (clicking on those blue hyperlinks in wikipedia can answer a lot of this)

Afferent nerve fiber - Wikipedia

en.wikipedia.org

Efferent nerve fiber - Wikipedia

en.wikipedia.org

Dendrites (while they include sensory receptors as a subtype) are just the recieving end of the neuron.

View attachment 273882

In regards to modality, this is what I gathered after some revision and using the wikipedia link you kindly added: Could you please kindly correct my errors?

For sensory modality, you can't have somatosensory or viscerosensory as a type of sensory modality,..because these refer to the location that the sensory info has been taken from... Somatosensory (sensory info from muscles body, including muscles, skin, etc.), Viscerosensory (sensory info from organs) correct. those are big broad categories. theres also special sensory (vision, taste, hearing, proprioception, etc) #Actually, I feel something is not right here tbh!

Sensory modality is the type of sensory information being carried. e.g. light, sound, taste, temperature, pressure & smell,..so light sensory info, sound sensory info, smell sensory info etc...yes

Crude touch and Fine touch are also sensory modalities.yes

Fine touch = can sense the touch sensation and locate where the touch sensation is on your skin yes, go look up which receptors are for this (not touch sensation in body or on internal organs correct #also not sure what sensation/ modality that would be?)mostly just stretch. no receptors for touch, cut, crush, or burn in the organs.

Crude touch = can sense the touch sensation but cannot locate where the touch sensation is on your skin sense deep pressure or vibration. can tell if it's on say, your distal anterior forearm to within half a centimeter or so, but not which milli- or micrometer of skin.

So there are sensory neurons specific for fine touch and there are sensory neurons specific for crude touch right? yep

View attachment 273887yeah. those are just some basic examples listed in the yellow bubbles. which category if falls into is dependant on type of receptor/sensory neuron

View attachment 273891not sure what your question is here. both arrows (as I read it) are indicating LMNs - they're the ones that start in the spinal cord and go to the muscle or other end organ.

About the image above: could you please highlight any further mistakes and kindly let me know your thoughts about some questions below?

The upper motor neuron starts in the cortex and its pathway is always downwards like in the image shown - red arrow. ah, I see. yes, that's correct

The lower motor neuron starts in the periphery (outside the brain & spinal cord) or the spinal cord and its pathway is always to the periphery - green arrow. 1st LMN always starts in the spinal cord. Sometimes there's a 2nd one that starts in the periphery.

Also, how can a motor neuron start in the periphery? I am always so used to the cell body of a motor neuron being in the spinal cord. Is there a diagram which could highlight a motor neuron starting in the periphery? search ganglion. follow the hyperlinks...

Ganglion - Wikipedia

en.wikipedia.org

In regards to motor modality:..

How can there be motor modality of a pathway of a signal ( I think this is what libertyyne highlighted in their post)? I though it was just for sensory that you have the modalities.

View attachment 273892
"...specific modality of pathway, ^whether^ sensory or motor..."
Sympathetic, parasympathetic, somatic - could all be termed modalities, but we just talk about them as pathways
And also what are the types of motor modalities? ^ You kindly mentioned the upper motor neuron & the lower motor neuron - are these to do with the motor modality? no What I mean is that for sensory modality we have pressure, touch, taste etc but not for motor modality.Sympathetic, parasympathetic, somatic

Thank you so so much! Apologies for asking so many silly questions!
Really appreciate your help and no worries at all if you are busy with other things 🙂

What class are you studying for? What books/resources are you using? I get that this can all be confusing on 1st pass, but all of this is laid out in any textbook on the topic, even in wikipedia (when you folllow enough hyperlinks 😉).

Ah thanks a million! 🙂 I am studying for anatomy - will be going into my first year in Sept. I am actually not using any resources apart from the internet atm haha. I have purchased some anatomy books (these are made by my uni) but I don't understand much of it because well, there are many mistakes ( I am going to a uni abroad so english is not the first language there and hence their books don't make much sense). So yeah, just preparing now lol

Thanks so much for the link for that book!!

 

[kraskadva]

Ah thanks a million! 🙂 I am studying for anatomy - will be going into my first year in Sept. I am actually not using any resources apart from the internet atm haha. I have purchased some anatomy books (these are made by my uni) but I don't understand much of it because well, there are many mistakes ( I am going to a uni abroad so english is not the first language there and hence their books don't make much sense). So yeah, just preparing now lol

Thanks so much for the link for that book!!

Gotcha.
Then I would also recommend the Netter's Anatomy coloring book (also available on Amazon), for gross anatomy.
But any course where you don't know what you don't know, start with a book. The internet is very useful when you know what to search for, but if you don't even know the terms, best to have someone lay them out for you.