A basic neuroanatomy question:

[Ahsan Iqbal]

I was reading a neuroanatomy book lately. I noted that every time a description of a nerve is made, the author has said the "fibers to the structure". There has been no distinction of whether the fibers are sensory or motor. Both are described as "fibers to the structure".

 

My basic knowledge of the nervous system tells me that motor nerves start from the cerebral cortex (mostly the pre-central gyrus) through the spinal cord or cranial nerve nuclei reaches the structure. Sensory neurons, in contrast, starts at the sensory organ to the spinal cord or cranial nerve nuclei to the relaying stations in the brain and finally to the cerebral cortex (mostly the post-central gyrus).

 

What I want to say is that motor nerve fibers pass FROM the central nervous system TO the peripheral structure. On the other hand the sensory nerve fibers pass FROM the sense organs TO the central nervous system. So when describing the routes of the nerves, shouldn't this be taken into account. Shouldn't we describe sensory nerves fibers as for instance "fibers from the skin of the face pass to trigeminal ganglion in its three divisions" instead of "sensory fibers to the skin of the face pass from the trigeminal ganglion in its three divisions".

 

I have never found a description in which the former method is followed so I am guessing that there is some solid reason behind why sensory fibers are not described as mentioned above. I expect the same difference in description as exists in the description of arteries and veins (arteries TO the kidney and veins FROM the kidney).

 

Has anyone any idea??

[thinker_jeff]

I was reading a neuroanatomy book lately. I noted that every time a description of a nerve is made, the author has said the "fibers to the structure". There has been no distinction of whether the fibers are sensory or motor. Both are described as "fibers to the structure".

 

My basic knowledge of the nervous system tells me that motor nerves start from the cerebral cortex (mostly the pre-central gyrus) through the spinal cord or cranial nerve nuclei reaches the structure. Sensory neurons, in contrast, starts at the sensory organ to the spinal cord or cranial nerve nuclei to the relaying stations in the brain and finally to the cerebral cortex (mostly the post-central gyrus).

 

What I want to say is that motor nerve fibers pass FROM the central nervous system TO the peripheral structure. On the other hand the sensory nerve fibers pass FROM the sense organs TO the central nervous system. So when describing the routes of the nerves, shouldn't this be taken into account. Shouldn't we describe sensory nerves fibers as for instance "fibers from the skin of the face pass to trigeminal ganglion in its three divisions" instead of "sensory fibers to the skin of the face pass from the trigeminal ganglion in its three divisions".

 

I have never found a description in which the former method is followed so I am guessing that there is some solid reason behind why sensory fibers are not described as mentioned above. I expect the same difference in description as exists in the description of arteries and veins (arteries TO the kidney and veins FROM the kidney).

 

Has anyone any idea??

The book writer may not be perfect for every detail. I think that your understanding is correct, which is enough.

[CharonY]

It depends on the focus of the textbook, I presume. Most distinguish between afferent and efferent pathways, though.

[Ahsan Iqbal]

I read one other author and they he has similar description of nerves. Basically, I was studying the cranial nerves. The first cranial nerve (olfactory nerve) is a purely sensory nerve. So it should be described as "nerve FROM the upper part of the nasal cavity". Instead everyone describes it as "nerve TO the upper part of the nasal cavity".

 

Probably their is some embryology involved in it. I don't have any knowledge of the embryology of the nervous system. Probably the nerves (whether sensory or motor) in the fetus follow the path from the CNS to the periphery and probably this is the reason why both sensory and motor nerves are described as "nerve TO the structure".

 

But I still need confirmation on this.

[CharonY]

It is a matter of context. i would have to read the whole passage, but from what it appears in a developmental context it is the projection of the nerve that defines the direction, not the direction in which the AP is going to travel.

 

So your interpretation makes perfect sense in that context.

[Guest Loka]

I think it varies from one book to another

[Joshua201]

The book writer may not be perfect for every detail. I think that your understanding is correct, which is enough.

 

 

It depends on the focus of the textbook, I presume. Most distinguish between afferent and efferent pathways, though.

 

 

I think it varies from one book to another

 

It depends on the author and his area of concentration.He might be an anatomist or a surgeon or perhaps a physiologist. Their methods of description varies. Most differentiate between afferent and efferent pathways as stated above.