Does CNS in spine have single fiber per inervated muscle?

In summary, the conversation discusses the concept of how information is sent from limbs to the brain. It is explained that there is not a single neuron that goes from the brain to the toe, but rather a group of connected neurons. This process becomes more complex with sensory input, where there is "packet addressing" and potential errors in addressing sensory information. The discussion also mentions species-specific differences, such as horses having a secondary structure along the spinal cord that controls leg movements, and octopuses having nine brains, with each arm having its own.
  • #1
cave_cat
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if I can move specific muscle in my toe via brain command, does this mean that in spinal cord there is a specific fiber that extends from brain to that toe? And let's say if in a lab rat we cut that single CNS fiber, the muscle affected will stop working without any other consequences to the organism?

Or is this mental model in fact completely wrong so that let's say CNS does time domain multiplexing (or packet addressing? or some other form of multiplexing?), allowing it to send commands to multiple muscles through a single "cable" / fiber?
 
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  • #3
There is not a single neuron that goes from the brain to the toe. There is however a group of connected neurons that travel this path. For muscle innervation it's pretty straightforward 1:1 type connections. It gets more tricky for sensory input where you do have "packet addressing". In fact we get errors in addressing sensory information. Probably the easiest example is with referred pain and the best example of that is wit heart attacks (easy to Google). Can't elaborate more right now I'm on my phone and I hate typing on phones!
 
  • #4
In reference to the specific wording of the original post, it partially depends upon the species. A horse, for instance, has sort of a "second brain" partway along the spinal cord somewhat similar to the way a stegosaurus did. The real brain will send a signal to trot, or walk, or gallup, and the secondary structure takes over sequencing of the motor neurons that control the legs. I'm pretty sure that's why it's so incredibly difficult to make a horse go in reverse; it isn't "hard wired".

edit: I just thought of this now. Even weirder is the octopus. It has 9 brains. Each arm has its own, plus one to coordinate them and take care of macroscopic duties such as logic, respiration and vision.
 
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  • #5


The concept of a single fiber per innervated muscle in the spinal cord is a simplified model that does not accurately reflect the complexity of the nervous system. While there are specific pathways that connect the brain to specific muscles, the reality is that there are multiple neural pathways and connections involved in any movement.

When you move a specific muscle in your toe via a brain command, it is not just one single fiber extending from the brain to that toe. Rather, it is a network of neurons and neural pathways that work together to coordinate and execute the movement.

In addition, the nervous system is constantly adapting and changing, so even if a specific fiber is cut in a lab rat, the body may be able to compensate and find alternative pathways to control the affected muscle. This is known as neuroplasticity.

Furthermore, the nervous system does use different forms of multiplexing to send commands to multiple muscles through a single "cable" or fiber. This can include both temporal and spatial multiplexing, where different signals are sent at different times or through different pathways.

Overall, the concept of a single fiber per innervated muscle in the spinal cord is an oversimplification and does not accurately reflect the complexity of the nervous system.
 

1. Does every muscle fiber in the body have a direct connection to the central nervous system (CNS) in the spine?

No, not every muscle fiber in the body has a direct connection to the CNS in the spine. Some muscles are innervated by nerves from the peripheral nervous system, while others may have indirect connections to the CNS through other nerves or pathways.

2. How does the CNS in the spine control muscle movement?

The CNS in the spine controls muscle movement through a complex network of nerves and pathways. Sensory neurons send signals to the spinal cord, which then relays information to the brain. The brain then sends motor signals back to the spinal cord, which activates motor neurons to stimulate muscle movement.

3. Are there any exceptions to the rule of one muscle fiber per nerve in the CNS-spine connection?

Yes, there are some exceptions to the rule of one muscle fiber per nerve. In certain cases, multiple nerve fibers may innervate a single muscle fiber, and vice versa. This is known as "nerve branching" and can occur in certain muscles that require more precise and coordinated movements.

4. Can the CNS in the spine regenerate damaged nerve connections to muscles?

Yes, the CNS in the spine has some ability to regenerate damaged nerve connections to muscles. This process is known as neuroplasticity and involves the rewiring and formation of new nerve connections to compensate for damaged ones. However, the extent of this regeneration depends on the severity and location of the damage.

5. Does the CNS in the spine play a role in muscle memory?

Yes, the CNS in the spine plays a critical role in muscle memory. This is because the spinal cord contains a network of neurons known as the "central pattern generator" which can store and recall movement patterns. This allows for faster and more efficient muscle movements without the need for constant input from the brain.

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