Sympathetic Nervous System Overview

Sympathetic Nervous System

• Function: Prepares the body for "fight or flight" responses.
• Neurotransmitters:
  • Epinephrine (adrenaline)
  • Norepinephrine (noradrenaline): Increases alertness, arousal, and blood pressure.
• Receptors:
  • Alpha: Primarily cause vasoconstriction.
  • Beta: Increase heart rate and force of contraction (β1), cause bronchodilation (β2).
• Active State:
  • Increased heart rate and force of contraction
  • Bronchodilation
  • Pupil dilation
  • Increased blood flow to skeletal muscles
  • Decreased blood flow to digestive system
  • Increased blood glucose levels
  • Increased sweating
• Inactive State:
  • Normal resting heart rate
  • Normal bronchial tone
  • Normal pupil size
  • Balanced blood flow distribution
  • Normal digestive function
  • Stable blood glucose levels
  • Normal sweating

Parasympathetic Nervous System

• Function: Responsible for "rest and digest" functions.
• Neurotransmitter: Acetylcholine
• Receptors:
  • Muscarinic: Mediate parasympathetic effects (e.g., decreased heart rate, increased secretions).
  • Nicotinic: Involved in neuromuscular junction signaling and some CNS functions.
• Active State:
  • Decreased heart rate
  • Bronchioconstriction
  • Pupil constriction (miosis)
  • Increased digestive system activity
  • Increased salivation and urination
  • Decreased blood pressure
• Inactive State:
  • Normal resting heart rate
  • Normal bronchial tone
  • Normal pupil size
  • Balanced digestive function
  • Normal salivation and urination
  • Normal blood pressure

Other Receptors

• Opioid Receptors:
  • Location: Primarily in the brain and spinal cord.
  • Function: Modulate pain, reward, and addictive behaviors; can influence autonomic functions indirectly.
• GABA Receptors:
  • Location: Ubiquitous in the brain and spinal cord.
  • Function: Inhibit neuronal activity, leading to calming effects, muscle relaxation, and reduced neuronal excitability.

Anticholinergic Substances

• Mechanism: Block the neurotransmitter acetylcholine, reducing parasympathetic nerve impulses.
• Effects: Drying of bodily fluids, relaxation of smooth muscle, dilation of pupils.
• Uses: Overactive bladder and Parkinson's disease treatment.
• Note: Does not activate the sympathetic response, but instead reduces parasympathetic activity.

Sympathomimetic Substances

• Mechanism: Mimic the effects of the sympathetic nervous system ("fight or flight").
• Effects: Increased heart rate, dilated airways, elevated blood pressure.
• Uses: Asthma, shock, and certain heart conditions.

Explore the key functions, neurotransmitters, and active vs inactive states of the sympathetic nervous system. This quiz delves into mechanisms like heart rate changes, blood flow adjustments, and responses to stress. Test your knowledge of how this system prepares the body for critical situations.