Basic Training Series: Nervous System: Peripheral Nervous System

Here's another quickie post on the Nervous System focusing on the Peripheral Nervous system.

Quick facts:

- All spinal and cranial nerves transmit information to the CNS
- 12 cranial nerves are all specialized. Some only send info, some only receive info and some are mixed

    I     - Olfactory
    II    - Optic
    III   - Oculomotor
    IV   - Trochlear
    V    - Trigeminal
    VI   - Abducens
    VII  - Facial
    VIII - Auditory
    IX   - Glossopharyngeal
    X    - Vagus
    XI   - Accessory
    XII  - Hypoglossal

- 31 pairs spinal nerves are mixed afferent and efferent

- Spinal nerves are formed by the joining of dorsal and ventral roots and contain somatic and autonomic motor and sensory nerve fibers

- Fibers of the anterior divisions or ventral rami supply the antero-lateral parts of the trunk and limbs

• - For the most part are larger than the posterior division/dorsal rami
• -Fibers extend to the limbs to form PLEXUSES.

• Cervical 
• Located from C1-C4
• Brachial plexus: 
• Located in axillary region
• Redistributes fibers to the major nerves of the upper extremites
• Median
• Ulnar 
• Radial 
• Axillary
• Musculocutaneous
• Lumbosacral plexus:
• Located in the lower abdominal cavity and pelvis
• Redistributes the fibers to the major nerves of the lower extremities
• Femoral
• Obturator
• Sciatic
• Tibial
• Peroneal

- Fibers of the posterior divisions or dorsal rami 

• Carry visceral motor, somatic motor, and sensory information to and from the skin and deep muscles of the back
• Are distinct from each other
• Innervate a narrow strip of skin and muscle along the back at the level from which the ramus leaves the spinal nerve

Well, that's good for now. Lots of info to process but very pertinent. 

Questions? Comments? Let me know.

Will

Basic Training Series: Nervous System: Central Nervous System

The Nervous System has 3 main divisions. They are:

- Central Nervous System
- Peripheral Nervous System
- Autonomic Nervous System (which has 3 sub-divisions: 1) Sympathetic 2) Parasympathetic 3) Enteric)

In this post, I will summarize the CENTRAL NERVOUS SYSTEM (CNS).

The CNS is composed of the brain and spinal cord.

Briefly about the brain....

- evolved from 5 vesicles in the cranial section of the neural tube
- vesicles are bilateral, mostly symmetrical and specialized

- 5 vesicles are:

• Cerebral Hemisphers
• Diencephalon
• Mid Brain
• Pons
• Medulla
• *Cerebellum (should be 6th region)

- interconnected by a 4 chamber ventricular system with connecting aqueduct 

Briefly about the spinal cord....

• thin, cylinder like structure
• attached to the brain 
• 5 sections with 31 segments 
• Cervical (8 segments)
• Thoracic (12 segements)
• Lumbar (5 segments)
• Sacral (5 segments)
• Coccygeal (1 segement)
• Each segment has a pair of spinal nerves
• transmission of sensory information to the brain
• regulation of motor and autonomic functions

QUICK OBSERVATIONS:

1) The brain is VERY COMPLEX. Just knowing those 6 regions will take some time but basically it IS the control center of the body. My friend, Peter, likes to call it the President of the body. It's not so much a king because others systems have a lot of input and say of what happens with the body but in the end the President makes the decisions along with input from others. 

2) The spinal cord is the super information highway of the nervous system, and it also mediates motor and autonomic functions; but it still has to answer to the brain in the final say so. 

Well, thats enough. Just wanted to keep these short and sweet. 

I'd love to hear from you with questions or comments. 

In mind, body and spirit,

Will

Basic Training Series: Nervous System Principle #8: CHEMICAL MESSAGE CODING

OKAAAAYYYY...

Here's the last one according to Angevine. Before I get into it, I want to say thanks to those who have been reading these posts. It's been a tremendous education for me to learn these principles. Now that I have them under my belt, so to speak, I will get more detailed with form and function.


"Chemical Message Coding
The basic function of the nervous system, from which all others derive, is communication, performed (with unsung neuroglial support) by neurons. It depends on special electrical, structural,and chemical properties of these diversified cells with their long processes, on their exploitation and refinement of two basic protoplasmic properties, irritability and conductivity, on their external and internal neuronal morphology featuring multipolar shape and integrative design, almost infinite modes of dendritic and axonal branching, widespread, diversified connections, and specialized organelles, and on their use of chemical substances to encode, deliver and decipher messages of their own and other neurons.

Neural circuits are chemically coded. Neuroanatomy encompasses interneuronal connections and also chemical mediators and transmitters. Neuroactive substances comprise neurotransmitters, neuromodulators, and neurohormones. Their definition in contexts other than site of action, postsynaptic neuronal activity, and corelease of one or more additional neuroactive substances can be misleading. Neurotransmitters are small molecules acting swiftly, locally, and briefly on target cells. Neuromodulators are very small (peptides), regulating but not effecting transmission, and neurohormones are also small, with intrinsic activity mediated by neuronal and other cells, exerting slow, widespread, and enduring influence via the extracellular fluid or bloodstream.

Neurons releasing hormones are quasi-endocrine cells, liberating secretory products from axonal endings into the perivascular space to be conveyed to blood vessels and thence to target organs. The provincial concerns of neurophysiology and endocrinology have fused into neuroendocrinology, as psychoneuroimmunology has united psychobiology, molecular neurobiology, and immunology."

Last one but so important as it deals with how the Neuromatrix sends signals all over the body. 

1) I love that Angevine says that "The basic function of the nervous system, from which all others derive is COMMUNICATION (with unsung neuroglial support) by neurons." 

2) These neuromodulators, neurohormones and neurotransmitters are essential to every function in the body. From all my research we are JUST starting to understand how powerful and influential these are. Of course pharmacology has been dealing with them for a while but the extent to which all of the above neurochemicals are affected is not fully known. 

For a GREAT book that is easy to understand, see Robert Sapolsky's "Why Zebras don't get ulcers". This book talks about Prof. Sapolskys favorite topic "glucocorticoids."

Honestly, this topic can is become complicated quickly, so I'm going to leave it at that. I look forward to learning more about them as it's important to trainers and therapists to understand that while we cannot directly affect the chemical coding, the process can be affected by something as simple as proper nutrition. 

Well, that's all for the Principles of the Nervous System.


Again, thanks for reading, and if you have questions or comments, please do not hesitate to post them.

In mind, body and spirit,

Will

Basic Training Series: Nervous System Principle #7: PLASTICITY

Okay, here's Principle #7, according to Jay Angevine:

"Plasticity
Highly reliable in a healthy person, the human nervous system has inherent modifiability, though in adulthood this attribute cannot approach that in invertebrates (moths and snails) or certain other vertebrates (teleosts and amphibians). In mammalian development, neural plasticity is striking. In continues postnatally. Abnormal visual experience at certain sensitive periods profoundly affects ocular dominance and orientation columns in the visual cortex. If an eye is closed at birth, ocular dominance columns for the other eye enlarge at the expense of adjacent blind eye columns, with thalamic fibers arriving in the cortex expanding terminal fields into them. If, shortly after birth, visual stimuli are restricted for a few weeks or even days to stripes of one orientation, cortical cells develop a response preference to lines of that orientation.

In humans, PET imaging studies of cortical blood flow show that tasks requiring tactile discrimination activate visual cortex in people blind at birth or having lost sight in childhood. This suggests that cortical connections reorganize after blindness: that afferent fibers to nearby cortical areas serving polymodal sensory integration usurp the bereft visual cortex. Such plasticity may explain the well-known tactile acuity of the blind.

In later development, neural plasticity operates on many levels, as in fine-tuning circuits to changing body dimensions. Depth perception is recalibrated as the skull enlarges and interpupillary distance increases. Even in adulthood, plasticity persists. Vilayanur Ramachandran has shown that a stroke with a cottonswab on the cheek of a young man who had accidentally lost his left arm led him to feel touch on his missing left hand. Later, the whole hand could be mapped on his face. The findings suggest that the deprived somatosensory cortical region for the hand becomes innervated by fibers from the adjacent face areas and that secondary input to a cortical neuron's broad receptive field becomes functional when primary input is lost.

After injury to the CNS, intact neurons form new terminals, by axon sprouting, to replace those of other neurons lost to trauma and thus reoccupy vacated synapses. Such reactive synaptogenesis, the clinically proven effectiveness of long-range regrowth of PNS axons, and the evident potential for axon regeneration in the CNS (as in teleosts and amphibia) hold promise for circuit reestablishment. But in mammals, these factors are thwarted by myelin debris, glial scarring, usurpation of sprouts, unresponsive injured neurons, and complex central connections. Developmental neuroscience now focuses on the cerebral cortex. The human nervous system appears to learn very rapidly by using preconstructed circuits and by locking neurons into specific types and functions after cell origin."

So this one is just AWESOME!  I was first introduced to this idea of "neuroplasticity" in the book The Brain that changes itself by Dr. Norman Doidge.  This book pretty much changed my life and the way I approached therapy and training/conditioning. I COULD go on and on, but I'll keep this one short too. Here goes my observations:

1) The first sentence mentioned in the HEALTHY person that the nervous system is able to be modified but no where close to invertebrates like moths and snails. However, it is still impressive. 

2) Dr. Angevine then goes into an example of how loss of sense like vision affects the brain. It seems the  neural resources that would have been utilized for vision are re-appropriated and still used. It seems the system has inherent intolerance for low usage of important structures and systems. 

3) A special interest to therapists and trainers, the nervous system changes based on dimensions of the body. Well, this is pretty intuitive. Something happens in the body (the skull was used by Angevine) and the nervous system recognizes this and adjusts so as to keep the body trekking on. Amazingly, all of this is under our "conscious" radar.  

4) When there is an injury to the body, like a loss of a limb, research has shown that plasticity starts remapping and the sensations of the lost limb can still be "felt." Ramanchandran demonstrated this when by touching the face of a patient who had lost a limb but the tactile sensation was still experienced. Whoa! 

5) In the final paragraph, Angevine discusses how the when the CNS is injured it can replace some of the structure in FROGS. Ugh... He explains that the other body processes that accompany the injury can thwart the regeneration; HOWEVER, there was some research done that stated:

"Wernig et al in Proc Natl Acad Sci U S A May (2008) have achieved a real breakthrough. They have been able to convert fibroblasts to neurons. These converted cells form into neurons, glia, and even dopaminergic cells. There has always been concern that converted cells might form tumors, but these scientists painstakingly separated the cells turned into neurons from pluripotential cells with fluorescent stains."

So, there's hope after all. Ordinary cells can be converted into neurons given the proper transcription factors. 

This principle is so important to me as a therapist, trainer and coach as we see that changes can occur not only in the body but in the all important nervous system. If our brains couldn't adjust all the REMARKABLE changes that took place in the mesodermal-derived structures like bones, joints, muscles, fascia, etc, we would be always be stuck mentally "small" in a "big" container. I don't think that would be too much fun. 

Anyway, this post is running long, so I'll cut it short here. 

Questions? Comments? I'd love to see what you're thinking!

In mind, body and spirit,

Will

Basic Training Series: Nervous System Principle #6: UNIFORMITY WITH VERSATILITY

Okay, #6 Principle courtesy of Dr. Jay Angevine,

Uniformity with Versatility
The vertebrate nervous system is accurately and reproducibly assembled. In animals of like genus and species it appears almost identical, although this is not absolute when genetic histories differ. Minor variations in the size of components and arrangements of cells are seen between species, striking ones between classes, orders and families. Yet basic regions and properties, cells and circuits, and overall organization are sufficiently alike to permit instant recognition off the basic brain plan and insights as to what these parts and cells contribute to function. Humans show increases in brain size and regional elaboration, numbers of neurons and prominence of certain connections, variations in cerebral sulcation, hemispheric asymmetry, and long projections."

Interesting principle to say the least. Here's what I got from it:

1) It looks like VERTEBRATES basically have the same nervous system plan. BASICALLY. Of course there are going to be differences but it shows how similar we are to other species, especially mammals. 

My friend, Diane Jacobs, PT wrote a little more on this, and I want to post it here because I could not have said it any better. In it she describes how little "bits" were added by nature throughout our evolution  and why we have the same basic nervous system plan as other creatures, great and small. Thanks, Diane!!

Once nature came up with a way to do something at a cellular level and this cellular model survived all the predatory and thermodynamic slings and arrows, it became handed down more less intact. Neurons are highly useful, but expensive metabolically; once a working model became established it became highly conserved, replicated endlessly in all manner of species filling all manner of niches, each species phenotype using the basic neuron model in endlessly inventive ways.

As creatures evolved, bits got added to the nervous system, but nothing was ever really deleted from it. As a result, we share basic neuron structure design with animals that date back to the days prior to the division that occurred between vertebrates and our invertebrate cousins on the planet - everything considered "animal" has neurons, except for sponges. The list includes radially symmetric jelly fish, starfish, etc., insects... - all have neurons (i.e., we humans are not "special" for having neurons, but our neuron number and arrangement is - "specie-al" to humans).

As evolution proceeded our (really ancient animal) ancestors found their neuronally equipped selves becoming bilaterally symmetrical, better for getting a grip on the world to haul a little body physically perhaps, but requiring more hard drive to coordinate two sides. So the nervous system found itself clumped up a bit at one end. After that it was probably just more economical for special senses to evolve where there was already extra hard drive built in. 

Everything after that, all the way to us, is a result of addition rather than truly different body plan. Apparently no other types of body plan were able to make it in the real world of predation and thermodynamic forces. So we share our bilaterally symmetric body plan with all other primates, quadrupeds, land vertebrates, and sea vertebrates including fish, who "invented" backbones and spinal cords, and everything else all the way back through time to whatever represents the fork in the road that led to worms on one side and fish ancestors on the other. Although worms lack a vertebral arrangement or any bones for that matter, they do have a bilaterally symmetric body plan, neurons, and a little "brain", up in front, to run all of it. 

Questions? Comments? I'd love to hear from you.

In mind, body and spirit,

Will

Basic Training Series: Nervous System Principle #5: PURPOSEFULNESS

Now we turn to Principle #5: PURPOSEFULNESS.

Here is another except from Dr. Jay Angevine's writing from the Encyclopedia of the Human Brain.


"The Purposefulness of Neural Components
Every part of the nervous system has at least one function, often many more. Small parts of the CNS may play crucial roles, as in the extensive distribution and profound influence of axons from inconspicuous brain centers. The locus ceruleus ("blue spot") on each side of the fourth ventricle contains about 12,000 large melanin-pigmented neurons. These synthesize norepinephrine and release it in the cerebral cortex, cerebellum, and almost every other part of the CNS. Electrically, they are almost silent in sleep, hypoactive in wakefulness, and hyperactive in watchful or startling situations. They serve vigilance and attention to novel stimuli. They contribute, indirectly but no less crucially, to perceptual and cognitive functions. By contrast, immense structures make large but expensive contributions, as in the cognitive and motor abilities afforded us by the billions of neurons in our cerebral and cerebellar cortices."


Even though the above paragraph is shorter, it's no less important to understanding that the EVERY part of the nervous system, has a purpose to it. No matter how small. Here are some things I picked out of it.

1) As I stated before, everything from the smallest "part" to the largest has a purpose or several purposes that we CURRENTLY know of; however, I am willing to bet that changes frequently as the science delves deeper into the NS.

2) I think a lot of folks concentrate on either the peripheral or central nervous systems but it seems that EACH part of each system (which is MANY) has a purpose and together those purposes start to add up into something that we really do not fully understand. Just my humble opinion.

3) The example about the locus ceruleus was great as it gave insight to how a small part affects the overall organism. This "small" part releases a very important chemical into critical areas of the brain which are charged with larger tasks like cognition and perception. Whoa. So what happens when one of these "small" parts stops working? Hmmmmm.... chaos maybe? For instance, the locus cereleus secretes norepinephrine in the brain, and its main function is directing attention to novel and potentially challenging stimuli.  Recently, they found that the LC also suppresses neruo-inflammation in the brain through the norepinephrine secretion. This is important in Alzheimer's Disease as there is a progression of the disease after the destruction of the LC.  The cognitive decline is well documented, so we see how small parts affect the whole.

4) Finally, the author informs us that the immense structures "make large and expensive contributions" like thinking and moving. Pretty important! Diane Jacobs, PT, always remarks how the nervous systems makes up 2% of the body BUT utilizes 20% of all resources in the body. If someone wants to debate the PURPOSEFULNESS of the nervous system, I'd like to see them do it without their cerebral cortex. ;-)

Pretty cool, stuff, huh????

I hope you are getting excited as I am about the Nervous System. The next post is Principle #5: UNIFORMITY WITH VERSATILITY.

Questions? Comments?

In mind, body, and spirit,

Will

Basic Training Series: Nervous System Principle #4: SPECIALIZATION

Okay, here we are at Nervous System Principle #4: Specialization. Lots of rich info here and a bit of foreshadowing into the complexity of the system.


"Specialization"
Reflecting its diverse tasks, the nervous system is specialized, from the single neuron to each brain region. Specialized subsystems analyze sensations. They differ in some ways, but data processing is progressive and networked in all. Neurons and the neuroglia have special shapes and roles, but both enjoy all criteria for cells and work in concert. Less obvious but equally specialized are subsystems for other functions: sleep-wakefulness, alertness, attention, affect, collating pages of a report, reading out loud from a book, self-awareness, brain damage control, and so on ad infinitum. 

Ubiquitous specializations include those for high nerve conduction velocity (large axon diameter, thick myelin sheath), space-saving bundling (small-axon diameter, thin myelin sheath, shared sheaths), short latency response (monosynaptic reflex), staggered, persistent latencies (parallel side chaining of long-axoned neurons), dependability (neuron redundancy), feature analysis (parallel processing), effect monitoring (feedback circuits), and force multiplication (feed-forward circuits). The neurons performing such tasks and the neuroglia backing them up are as specialized as these many diversified services. For neurons and the neuroglia, form indeed reflects function."

Now, this is just getting interesting! Looking at the paragraph above, I had to stop and do a little research about these specialized subsystems. To be honest, that will take SEVERAL posts and not something I want to go into now because ...well, I don't understand it fully. Later on that. 

Anyway, here's what I gathered from this excerpt:

1) The nature of the Nervous System is diversity in its activities, so this necessitates subsystems that are delegated for each task with the accompanying specialized "equipment" of neurons and neuroglia for support. 

2) Different subsystems analyze internal and external sensations. 

3) Even though the neurons and neuroglia (support staff for neurons) have different shapes and sizes, they are still cells and work together for the greater good of function. 

3) The nervous systems subsystem tasks are numerous and make up activities like wakefulness, brain damage control, alertness, attention, etc. 

4) The second paragraph gets into the specifics of how the specializations are combined and their resultant activity like feed forward and feedback circuits. We see how this is vitally important to the entire body in terms of organism survival and homeostasis. 

Another WOW moment for me as this Principle  touches on how the nervous system is ORGANIZED so that it can carry out functions. 

As promised, I'm keeping these posts shorter. 

Lookout tomorrow for Principle #5: PURPOSEFULNESS

Questions or comments, please let know.

In mind, body and spirit,

Will