The nervous system

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The nervous system
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Introduction

• In order to synchronize the functions of
  trillions of cells in the human body two control
  systems exist, that happen to be tightly
  interlinked.
• What are they?

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Control Systems

• Nervous System (NS)
• Endocrine System (ES)
• Sometimes collectively know as the Neuroendocrine
  system
• Unlike the separation of departments in a medical
  or chiropractic college, the body functions as an
  integrated unit.

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Nervous System

• Together with the endocrine system regulate most
  internal functions
• Organize and control activities we know
  collectively as human behavior
• Eg. Smiling, walking, palpation, anger,
  motivation, ideas, memory
• Divided into a peripheral and central nervous
  system for convenience

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Neuroendocrine interactions

• Genesis of the patterns of neuronal discharge
  lead to the release of hypothalamic hormones
  which control pituitary function
• Hypothalamic control of the secretion of the
  pituitary gland.
• Endocrine glands outside the head are innervated
  by the autonomic nervous system, which affects
  their function

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Chemical messengers

• Hormonal peptides are found all over the body and
  are manufactured by neurons, endocrine glands and
  other tissues

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Neuroendocrine system

• These observations make it clear that instead of
  a rigidly separated nervous and endocrine
  systems, there is a neuroendocrine system with
  the same chemical messengers being synthesized
  and secreted by both endocrine cells and neurons
  alike.

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Host resistance

• So what does this have to do with health anyway?
• It has been known for centuries that those who
  have recovered from an infectious disease do not
  usually suffer from that disease again, they are
  immune.

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Neuroimmunomodulation

• The immune system which for many years was
  believed by most to function completely
  independently of the major control systems
  (neuroendocrine) in the body
• That has given way to a new concept that
  recognizes this interaction of the nervous,
  endocrine and immune systems

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Neuroimmunomodulation

• The study of how the nervous, endocrine and
  immune systems communicate with each other
• There is a wealth of information that actually
  dates back to the 19th century
• Does the intergrity of the neuroendocrine system
  affect host resistance?
• What role can chiropractic intervention play in
  the integrity of the neuroendocrine system

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Neuroimmunomodulation

• Neural innervation of immune organs
• Nervous, Endocrine and Immune Systems
• Share common receptors and peptides
• Key area is the hypothalamus
• Hypothalamic control of the autonomic NS
• Hypothalamic control of the pituitary
• Hypothalamic control of the immune system

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Bidirectional Communication
NS
IS
ES
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Neuroimmunomodulation

• Neuropeptides mostly inhibit immune cell
  proliferation and are released during episodes of
  physical or psychologic stress which may mediate
  the suppression of the immune system

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Prolonged stress

• Associated with increased susceptibility to
  disease and infection
• Decreased immume function which precedes
  increased susceptibility to disease and infection
  may be mediated by the neuropeptides released by
  neuroendocrine system in response to stress

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Chiropractic

• The concept of segmental facilitation
• Based on the work of Denslow and Korr
• The level of the subluxation causes that segment
  to be in a state of facilitation
• Neurons in that cord level are closer to
  threshold and can fire inappropiately
• scream louder and longer
• Any spinal cord traffic (afferent and efferent)
  will cause this segment to fire inappropriately
  creating excessive outflow to target tissues in
  the line of fire

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Segmental Facilitation

• The facilitated segment can act as a focusing
  lens, bombarding its target tissues with
  excessive neural activity
• Output from the ventral horn can be associated
  with muscle spasm
• Output from the intermediolateral horn cells can
  be associated with hyperactivity of sympathetic
  outflow which could affect blood flow, vegatative
  functions, immune function

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Homeostasis

• The idea of a stable internal environment in the
  face of changing external conditions was first
  proposed in the 19th century by French
  physiologist Claude Benard
• This idea was developed further by American
  physiologist Walter Cannon who put forward the
  concept of homeostasis as the complex physiologic
  mechanisms that maintain the internal milieu
  (enviornment)
• The hypothalamus is a key area

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The cerebellum (little brain)

• 10 of the total volume of the brain but contains
  more than ½ of all neurons
• Major influence on decending motor systems via
  the cerebral cortex
• Regulates balance, eye movements, body and limb
  movements
• Input from the spinal cord, mainly from the
  somatosensory receptors (joint and muscle
  proprioceptors)

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The cerebellum (cont.)

• The cerebellum participates in motor learning
• The cerebellum may have a role in cognitive
  processing and emotion
• The cerebellum is loaded by the integrity of
  joint mechanoreceptors
• Anatomical studies also reveal direct and
  reciprocal connections between the cerebellum and
  the hypothalamus

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Last but not least

• The prevailing view during most of the 20th
  century was that the nervous system was hard
  wired from birth.
• That neurons make specific connections with one
  another raises an interesting question. How if
  the nervous system is wired so precisely, is
  behavior modified?

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Plasticity

• The ability to alter connections in the NS
• There is considerable evidence for plasticity at
  synapes both short term (hours) and long term
  (days) changes which can include growth of new
  connections (synaptogenesis)
• Neurogenesis in adults
• Appears limited in mammalian species to
• Olfactory bulb
• hippocampus

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Plasticity

• Neuronal synapses can be modified functionally
  and anatomically
• during development and regeneration
• Through experience and learning
• Functional alterations are typically short term
• Involve changes in effectiveness of exsisting
  synaptic connections
• Anatomic alterations involve the growth of new
  synaptic connections between neurons

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Conclusion

• The nervous system is extremely complex in its
  structure, function and interactions both within
  itself and with other systems
• It plays a key role in host resistance and health
  through its interactions and communication with
  the endocrine and immune systems
• Chiropractic intervention may play a key role in
  optimizing the function of the neuroendocrine
  system through its effects on segmental
  facilitation and normalizing joint proproceptive
  input into the central nervous system