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The Nervous System Overview

Posted On February 1, 2019

Excerpts from previous naturopathy assignments HLT60512.  The Nervous System in Point Form

The Central nervous system (CNS) consists of brain and spinal cord only, yet the peripheral nervous system (PRNS) relays information away from and too the CNS via afferent and efferent neurons. The two major divisions of the PRNS are autonomic (ANS) and somatic (SomNS). The PRNS is further classified into the autonomic Parasympathetic (PNS) and Sympathetic (SNS).

(AIAS, 2018)

SNS is responsible for ‘fight or flight’ reactions and utilises hormones such as norepinephrine to generate energy to muscles to, run away from danger for example. The parasympathetic is the ‘rest and digest’ system, it utilises input such as hormones like acetylcholine to manage metabolic functions (Low, 2018)

All cells in the Nervous system are made of neurons, which consist of axons and dendrites able to conduct and transmit signals away from cells or towards cells respectively. Nerves send signals to and from the brain and spinal cord and other body organs via nerve impulses. They’re termed as motor (MN) sensory (SN), or (IN) interneurons. Information from the CNS to muscles, organs, and glads utilise MN. Information from the organs and internal and external environment is carried to the CNS SN. Information relayed between MN and SN is conducted by IN (Thought Co, 2018)

Brain, Nervous Tissue, Spinal Cord, Associated Nerves

Brain

  • Brain stem, diencephalon, cerebrum and cerebellum
  • Cerebral cortex, basal nuclei, thalamus, hypothalamus, cerebellum, diencephalon, brain stem
  • Frontal cortex, prefrontal cortex, cerebellum, occipital lobe, parietal and temporal lobes, Protected by the blood brain barrier (BBB) meningeal fluid (MF) and Cranial bones.
  • Pia mater (PM), arachnoid mater (AM) and dura mater (DM) composes meninges
  • Protected by cerebrospinal fluid (CSF)
  • Waste exits e.g. dead cells exit via CSF and interstitial fluid (IF) (AIAS, 2018)

Spinal Cord

  • Protected by spinal column
  • Covered by the meninges, grey and white matter
  • Ascending nerves carry information from body to brain and descending nerves from brain to body pertaining to motor function
  • The brain is supplied with blood vessels which supply oxygen & glucose (AIAS, 2018)

Nerves and nervous tissue

  • Nerve cells consist of nerve fibres axons, dendrites, and glial cells
  • Grey matter contains neuronal cell bodies dendrites and glial cells.
  • White matter is insulated conductive tissue and consists of myelinated axons
  • Glial cells form connective tissue within the CNS and physically, metabolically and functionally support the neurons.
  • Oligodendrocytes synthesise myelin.
  • Microglial cells are the defence cells and remove debris from dead cells (infection fighting cells)
  • Astrocytes support cells in the CNS and join them together
  • Glial progenitor cells produce new astrocytes and oligodendrocytes
  • The brain utilises about 20% of the oxygen used by the entire body.
  • The brain is one of the most metabolically active organs in the body Mental activity for example increases oxygen use
  • If the blood flow to is interrupted unconsciousness may result and if the cells are deprived of oxygen for as little as four minutes there may be permanent brain injury.
  • Myelinated neurons conduct nerve impulses more efficiently.  Neurotransmitters can activate or inhibit a second neuron  (AIAS, 2018)

The Autonomic and somatic nervous systems 

The autonomic nervous system (ANS) is ‘automatic’ without conscious thought, and the somatic nervous system (SomNS) is controlled by thought. ANS regulates information like heart contractions, blood pressure, rate of breathing, metabolism, sexual response, urination, defecation (Low, MD). SomNS regulates information like reflex responses, catching a ball, and other intended body movement. ANS and SomNS obtain information from motor, sensory, and interneurons which receive information from mechanoreceptors, thermoreceptors, nociceptors, photoreceptors and chemoreceptors to relay information (Low, 2018). For Nervous System Outline See appendix. 3

Brief description of the anatomy of the brain, nervous tissue, and spinal cord and associated nerves

Brain, Nervous Tissue, Spinal Cord, Associated Nerves 

The brain stem, diencephalon, cerebrum and cerebellum and spinal cord are innervated with neurons. Ascending nerves in the spinal cord carry PNS messages to the brain and descending nerves CNS messages to the body (AIAS)

Axons, dendrites, and glial cells compose neurons. White matter is insulated conductive tissue (of myelinated axons) and Grey matter contains neurons responsible for structure and functions of the nervous system.

Oligodendrocytes synthesise myelin, microglial cells fight infections and remove debris from dead cells via interstitial fluid.

Astrocytes support cells in the CNS and join them together (AIAS, 2018).

Heather Indiana Rose

Copyright 2019

 

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