Nervous System Functions and Effects

Sympathetic Nervous System (SNS)

• Function: Prepares the body for "fight or flight" responses, active during stress, danger, or vigorous activity.
• Effects:
  • Increases heart rate and force of contraction.
  • Dilates bronchioles in the lungs.
  • Dilates pupils.
  • Inhibits digestion.
  • Stimulates glucose release from the liver.
  • Constricts blood vessels in non-essential organs and dilates them in muscles.
• Receptors: Adrenergic receptors respond to adrenaline (epinephrine) and noradrenaline (norepinephrine).
  • Alpha receptors:
    • Alpha-1: Causes vasoconstriction in blood vessels.
    • Alpha-2: Found in the CNS and presynaptic nerve terminals, modulating neurotransmitter release.
  • Beta receptors:
    • Beta-1: Increases heart rate and force of contraction in the heart.
    • Beta-2: Causes bronchodilation and vasodilation in lungs and skeletal muscle blood vessels.

Parasympathetic Nervous System (PNS)

• Function: Promotes "rest and digest" activities, active during restful periods, conserving energy.
• Effects:
  • Decreases heart rate.
  • Constricts bronchioles in the lungs.
  • Constricts pupils.
  • Stimulates digestion and peristalsis.
  • Promotes glucose storage in the liver.
  • Dilates blood vessels in the gastrointestinal tract.

Receptors (General)

• Cholinergic Receptors: Respond to acetylcholine.
  • Muscarinic Receptors:
    • M1: Found in CNS and gastric parietal cells, involved in cognitive function and gastric acid secretion.
    • M2: Found in the heart, decreases heart rate.
    • M3: Found in smooth muscles and glands, causes smooth muscle contraction and glandular secretion.
    • M4 and M5: Found in the CNS, involved in various central nervous system functions.
  • Nicotinic Receptors: Found in autonomic ganglia (both SNS and PNS) and neuromuscular junctions; transmit nerve impulses to muscles.

Key Differences

• Origin:
  • Sympathetic: Thoracic and lumbar regions of spinal cord (T1-L2).
  • Parasympathetic: Cranial nerves (III, VII, IX, X) and sacral spinal cord (S2-S4).
• Neurotransmitters:
  • Sympathetic: Primarily norepinephrine/noradrenaline.
  • Parasympathetic: Primarily acetylcholine.
• Responses:
  • Sympathetic: Widespread, longer-lasting effects due to adrenaline release from adrenal medulla.
  • Parasympathetic: Localized, shorter-lasting effects.

Explore the intricate functionalities of the sympathetic and parasympathetic nervous systems. This quiz covers their roles, effects on the body, and the different types of receptors involved in these processes. Test your understanding of how these systems prepare the body for various situations.