Nervous System Confusion

[powersellingmom]

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Hey you guys. I'm having some serious trouble untangling all of the jargon of the nervous system anatomy. I've read the chapters on the nervous system by several books, but I still feel like I have some things wrong in my head.

So I know that it is separated into the central and peripheral systems. The central nervous system consists only of interneruons within the brain or spinal chord that integrate information from the peripheral nervous system.

But now here is the hard part. The peripheral nervous system is divided into the somatic and the autonomic nervous system. The somatic nervous system is divided into sensory and motor neurons. Sensory neurons relay messages from sensory receptors to the central nervous system, where they are integrated, and then sent back to the motor neurons which stimulate effectors that are under our conscious control.

The autonomic nervous system regulates organ function in the body and is also split into sensory and motor nerves. Like the sensory nerves of the somatic nervous system, these relay signals from sensory receptors to the central nervous system, which integrates them. The CNS then stimulates either the sympathetic or parasympathetic effector neurons based on the sensory information. If the sympathetic nervous system is acted on, the preganglionic (a ganglion is a bundle of axons that are part of the peripheral nervous system) cells are stimulated at the thorac/lumbar region. The preganglions are part of the SNS. The preganglions then stimulate the postganglions, which stimulate the effectors. For the parasympathetic, the process is the same, except the preganglions are at the base of the brain or the base of the spinal chord, and they only use acetylcholine whereas the postganglions of the SNS use epinephrine or norepinephrine.

Be honest, am I done for?

 

[Gigantron]

Hey you guys. I'm having some serious trouble untangling all of the jargon of the nervous system anatomy. I've read the chapters on the nervous system by several books, but I still feel like I have some things wrong in my head.

So I know that it is separated into the central and peripheral systems. The central nervous system consists only of interneruons within the brain or spinal chord that integrate information from the peripheral nervous system.

But now here is the hard part. The peripheral nervous system is divided into the somatic and the autonomic nervous system. The somatic nervous system is divided into sensory and motor neurons. Sensory neurons relay messages from sensory receptors to the central nervous system, where they are integrated, and then sent back to the motor neurons which stimulate effectors that are under our conscious control.

The autonomic nervous system regulates organ function in the body and is also split into sensory and motor nerves. Like the sensory nerves of the somatic nervous system, these relay signals from sensory receptors to the central nervous system, which integrates them. The CNS then stimulates either the sympathetic or parasympathetic effector neurons based on the sensory information. If the sympathetic nervous system is acted on, the preganglionic (a ganglion is a bundle of axons that are part of the peripheral nervous system) cells are stimulated at the thorac/lumbar region. The preganglions are part of the SNS. The preganglions then stimulate the postganglions, which stimulate the effectors. For the parasympathetic, the process is the same, except the preganglions are at the base of the brain or the base of the spinal chord, and they only use acetylcholine whereas the postganglions of the SNS use epinephrine or norepinephrine.

Be honest, am I done for?

I thought the PNS had Sensory and Motor Divisions, with the motor division being further divided into the Somatic and Autonomic nervous systems (with the autonomic nervous system controlling parasympathetic and sympathetic actions). You might have it the other way around.

 

[Testosterone]

The peripheral nervous system is divided into autonomic nervous system and the somatic nervous system. Both systems contain sensory neurons and motor neurons.

 

[RocketSurgeon]

I thought the PNS had Sensory and Motor Divisions, with the motor division being further divided into the Somatic and Autonomic nervous systems (with the autonomic nervous system controlling parasympathetic and sympathetic actions). You might have it the other way around.

Hmm nope. Let's think about this. What does motor mean? Think motor when you think muscle. Okay, a motor unit is a group of neurons (motor neurons) that innervate a group of muscles (one neuron can innervate multiple muscle fibers but one muscle fiber is only innervated by one motor neuron). You can control motor activities in two ways. One, descending control from the cranial nuclei (Red Nuclei, Vesibular Nuclei and so on). Two, spinal reflex (Knee Jerk/Crossed Extensor Reflex). The autonomic nervous system does not participate in these activities (with a few exceptions that you do not need to know).

Sensory, outside the CNS, this would refer to all the peripheral nerves which send sensory information into the CNS. Think of all the senses. (Optic system is part of the CNS as it develops from the diencephalon). A few examples are neurons that 1) take information from proprioceptors to the SI and SII areas of the cortex (dorsal columns) 2) Pain information: C fibres lateral spinal columns 3) or neurons that form the circuit for the knee jerk reflex these synapse on motor neurons in the ventral horns of the spinal cord

The autonomic nervous system is a different entity altogether dont get them mixed up. **Correction apparently a lot of intro books do not make this distinction. We treated motor systems and sensory systems as related topics. Autonomic system was grouped with neuroendocrinology, enteric divisions and so on. From what I remember Fundamental Neuroscience treats them as diff topics as well.

Feel free to PM me if you have any neuroanatomy/physiology questions !

 

[manohman]

Hmm nope. Let's think about this. What does motor mean? Think motor when you think muscle. Okay, a motor unit is a group of neurons (motor neurons) that innervate a group of muscles (one neuron can innervate multiple muscle fibers but one muscle fiber is only innervated by one motor neuron). You can control motor activities in two ways. One, descending control from the cranial nuclei (Red Nuclei, Vesibular Nuclei and so on). Two, spinal reflex (Knee Jerk/Crossed Extensor Reflex). The autonomic nervous system does not participate in these activities (with a few exceptions that you do not need to know).

Sensory, outside the CNS, this would refer to all the peripheral nerves which send sensory information into the CNS. Think of all the senses. (Optic system is part of the CNS as it develops from the diencephalon). A few examples are neurons that 1) take information from proprioceptors to the SI and SII areas of the cortex (dorsal columns) 2) Pain information: C fibres lateral spinal columns 3) or neurons that form the circuit for the knee jerk reflex these synapse on motor neurons in the ventral horns of the spinal cord

The autonomic nervous system is a different entity altogether dont get them mixed up. **Correction apparently a lot of intro books do not make this distinction. We treated motor systems and sensory systems as related topics. Autonomic system was grouped with neuroendocrinology, enteric divisions and so on. From what I remember Fundamental Neuroscience treats them as diff topics as well.

Feel free to PM me if you have any neuroanatomy/physiology questions !

Does the autonomic nervous system include sensory nerves?

 

[Hadi7183]

It does, but I don't think it's tested on the MCAT. An example is the pathway involved in measuring the pH and PCO2 levels by chemoreceptors in carotid artery and medulla and setting the heart rate accordingly. Check out the following link:

http://www.scholarpedia.org/article/Autonomic_nervous_system#Afferent_inputs_to_autonomic_pathways

 

[Czarcasm]

Hey you guys. I'm having some serious trouble untangling all of the jargon of the nervous system anatomy. I've read the chapters on the nervous system by several books, but I still feel like I have some things wrong in my head.

So I know that it is separated into the central and peripheral systems. The central nervous system consists only of interneruons within the brain or spinal chord that integrate information from the peripheral nervous system.

But now here is the hard part. The peripheral nervous system is divided into the somatic and the autonomic nervous system. The somatic nervous system is divided into sensory and motor neurons. Sensory neurons relay messages from sensory receptors to the central nervous system, where they are integrated, and then sent back to the motor neurons which stimulate effectors that are under our conscious control.

The autonomic nervous system regulates organ function in the body and is also split into sensory and motor nerves. Like the sensory nerves of the somatic nervous system, these relay signals from sensory receptors to the central nervous system, which integrates them. The CNS then stimulates either the sympathetic or parasympathetic effector neurons based on the sensory information. If the sympathetic nervous system is acted on, the preganglionic (a ganglion is a bundle of axons that are part of the peripheral nervous system) cells are stimulated at the thorac/lumbar region. The preganglions are part of the SNS. The preganglions then stimulate the postganglions, which stimulate the effectors. For the parasympathetic, the process is the same, except the preganglions are at the base of the brain or the base of the spinal chord, and they only use acetylcholine whereas the postganglions of the SNS use epinephrine or norepinephrine.

Be honest, am I done for?

You have the right idea. Anatomically, we have a central and peripheral ns. However, the terms somatic and autonomic are just a different way of making a functional distinction of the peripheral nervous system.

Somatic is anything we can consciously perceive or control. Think of all the five senses: sight, hearing, sound, touch, and smell or the skeletal muscles within your body. Each one of these has a sensory and motor component. These are things you could consciously perceive or control.

You can feel the breeze on a windy day because sensory neurons wrapped around your hair follicles (swaying back and fourth) send that information to the spinal cord which travels all the way up to the sensory component of the cerebrum where sensory input is received and you become consciously aware of the stimuli. The brain then sends that info to the motor component of the cerebrum (via motor neurons), then to skeletal muscle, ultimately causing the goosebumps you experience on a cool, windy day.

Consider what happens when you are carrying a heavy object. Within the major skeletal muscles of our body, we have specialized receptors wrapped around muscle fibers and tendons called prioprioreceptors that recognize strain and tension. This sensory input travels to the cerebrum of the brain where it gets integrated by the sensory component of the cerebrum (so you become consciously aware); You then consciously control skeletal muscle action. "This box is too damn heavy. Let me put it down."

Autonomic refers to things we are not consciously aware of and cannot control, atleast not directly. Generally, this refers to internal organs (digestive tract, lungs, heart, etc.)

Consider what happens when you breath. Within our body, we have special sensory receptors (chemoreceptors and baroreceptors on the aorta of the heart) that monitor both the metabolic products of our blood and our blood pressure. This sensory input travels to the CNS but a very specific part of the CNS where unconcious input is received: the brainstem (specifically, the medulla oblongata). Within the medulla, we have special nuclei centers that integrate this sensory information and ultimately decide whether to increase of decrease respiration (via motor neurons: sympathic or parasympathic input) to the muscles controlling respiration (the diaphram and intercostal muscles). At the same time, this integrated info determines the heart rate.This is not something you are consciously control and usually, you don't even think about this happening.

That's really all there is too it. Sure things can get a little murky at times when you consider things like perceived pain or controlled respiration, but these are not something you generally have to consider. Regardless, as long as you realize this is a functional characterization, you'll be okay.

EDIT: just realized this was posted ages ago, my bad.

 

[neurodoc]

You have the right idea. Anatomically, we have a central and peripheral ns. However, the terms somatic and autonomic are just a different way of making a functional distinction of the peripheral nervous system...

The distinction between CNS and PNS is anatomical...CNS is the brain and spinal cord, nerve tissue within the meningeal tissues that surround the brain and spinal cord and brainstem spinal nerves. One major histologic difference between CNS and PNS is the myelin of CNS and PNS neurons. CNS myelin is produced by oligodentrocytes and PNS myelin is produced by Schwann cells. As you say, the distinction between the ANS and Somatic Nervous System (SNS) is functional. ANS is a system that operates without conscious awareness, whereas SNS involves consciousness.

Both systems involve afferent inputs to the CNS. Indeed, the CNS would not be able to perform its function of responding to the environment without a means to register, in some way, environmental information. "Afferent" information is provided by PNS neurons that respond to some sort of stimuli, which they transmit to the CNS. Based on this afferent information, the CNS mediates an "efferent" response from the organism. "Afferent " simply means that the information is carried from the periphery to the CNS. "Afferent" is generally taken to mean "sensory." "Sensory," however, generally implies some sort of conscious awareness. An "efferent" is generally taken to mean a voluntary "motor" response.

As regards the function of the ANS, it's clear that the ANS has both afferent and efferent functions, and these can be considered as sensory and motor functions.