Disorders of the Autonomic Nervous System

Key Terms

• Agonist: A drug or substance that activates a receptor, mimicking the effect of a neurotransmitter.
• Antagonist: A drug or substance that binds to a receptor and counters the effect of a neurotransmitter.

Disorders of the ANS

Raynaud's Disease

• Description: Excessive sympathetic stimulation of blood vessels in fingers and toes.
• Effects: Diverts blood to internal organs, reducing flow to fingers and toes.
  • Causes pain and bluish discoloration of the digits.
  • Often associated with cold temperatures.
• Possible Cause: May have an autoimmune component.

Autonomic Dysreflexia

• Description: Excessive sympathetic response, common in patients with spinal cord injuries.
• Location: Particularly above thoracic level six.
• Effects: Lack of regulated control from higher brain centers causes sudden, potentially life-threatening increases in blood pressure.

Pupillary Reflex

• Sympathetic Stimulation: Causes dilation of pupils (e.g., norepinephrine).
• Parasympathetic Stimulation: Causes constriction of pupils.
• Madriasis: Use of phenylephrine to mimic sympathetic stimulation for eye examinations.

Drugs Affecting the Autonomic Nervous System

Belladonna (Deadly Nightshade)

• Cosmetic Use: Used to dilate pupils by mimicking the sympathetic nervous system.
• Risks: Can be fatal if ingested.
  • Contains compounds atropine and scopolamine.
  • Overdose can cause paralysis, hallucinations, convulsions, and death.

Other Drugs

• Drug Overdoses: Can result in pinpoint pupils; used as a diagnostic sign.