Peripheral Nervous System

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Peripheral Nervous System

• Composed of nerves and ganglia.
• Nerves are bundles of axons
• Each axon is a nerve fiber
• Cranial nerves take impulses to and from the
  brain.
• Spinal nerves take impulses to and from the
  spinal cord.

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Cranial and Spinal Nerves
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Somatic System

• Somatic system includes nerves that take sensory
  information from external sensory receptors to
  the CNS and motor commands away from the CNS to
  the skeletal muscles.
• Voluntary control of skeletal muscle
• Reflexes are automatic responses to a stimulus.
• Does not require cortical processing
• Involuntary
• Protective function

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Reflex Arc
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Autonomic System

• Autonomic system regulates the activity of
  cardiac and smooth muscles and glands.
• Similar features of sympathetic and parasympathic
  divisions
• Function automatically, usually involuntary
• Innervate all internal organs
• Comprised of a preganglionic neuron, ganglia, and
  a postganglionic neuron

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Autonomic System

• Sympathetic division brings about fight or flight
  responses.
• Thoracolumbar origin
• Role of sympathetic chain ganglia
• Neurotransmitter norepinephrine (similar in
  structure to adrenalin)
• Parasympathetic division brings about relaxed
  responses.
• Cranial and sacral origin
• Neurotransmitter acetylcholine

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Drug Abuse

• Drugs that affect the nervous system have two
  general effects.
• Impact limbic system.
• Promote or decrease action of a particular
  neurotransmitter.
• Drug abuse is apparent when a person takes a drug
  at a dose level and under circumstances that
  increase the potential for a harmful effect.

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Drug Actions at a Synapse
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Drug Abuse

• Alcohol.
• May affect GABA and Glutamate
• Overuse leads to decreased fat metabolism, fat
  build up in the liver and liver damage
• Nicotine.
• Causes neurons to release dopamine.
• Excess dopamine has reinforcing effect that leads
  to dependence.
• Regular use increased nicotine receptors in the
  brain
• Stimulant for neurons and other cells (cardiac)
• Cocaine.
• Prevents synaptic uptake of dopamine.
• Continued use causes body to produce less
  dopamine.
• Rush sensation followed by arousal followed by a
  crash
• Overuse can lead to seizures, cardiac and
  respiratory arrest
• Long term brain damage, link to Parkinsonss
  disease

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Drug Abuse

• Heroin.
• Binds to receptors meant for endorphins.
• Derived from morphine
• 3-6 minutes, relief from pain and feeling of
  euphoria
• Continued use causes body to produce fewer
  endorphins.
• Overuse can lead to hallucinations, mental and
  emotional disorders
• Marijuana.
• Binds to receptor for anandamide.
• Active chemical is THC or tetrahydrocannabinol
• Mild euphoria, alters sensory perception
• Brain impairment? Medicinal Benefits?

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Degenerative Nervous System Diseases

• Alzheimer disease.
• Presence of abnormal neurons.
• Plaques.
• Neurofibrillary tangles.
• Parkinson disease.
• Overactive basal nuclei due to the degeneration
  of dopamine-releasing neurons in the brain.

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