Lecture: The Parasympathetic Nervous System and Cranial Nerves

Introduction to Heart Rate and Autonomic Nervous System

• Resting Heart Rate: ~60 beats per minute
• Without Autonomic Nervous System: Heart rate would increase to ~100 bpm
  • Increased wear and tear on cardiac muscle
  • Greater pressure on blood vessels
  • Higher energy requirement; body out of balance

Parasympathetic Nervous System (PNS)

• Functions:
  • Calms the body after stress (antidote to sympathetic nervous system)
  • Handles digestion, reproduction, excretion, and immune response
  • Maintains balance for the regular functioning of the body
• Ganglia Location: Near effector organs
• Neurotransmitters:
  • Uses acetylcholine (ACh) for both pre- and post-ganglionic synapses

Sympathetic Nervous System (SNS)

• Functions:
  • Prepares the body for 'fight or flight'
• Ganglia Location: Near the spinal cord
• Neurotransmitters:
  • Uses acetylcholine (ACh) for preganglionic synapses
  • Uses norepinephrine for postganglionic synapses

Structural Differences: PNS vs SNS

• Sympathetic Nerves:
  • Origin: Thoracolumbar area of spinal cord
• Parasympathetic Nerves:
  • Origin: Craniosacral (cranial nerves from brain and sacral nerves near tailbone)
• Cranial Nerves:
  • 12 nerves, various functions (motor, sensory, or both)

Cranial Nerves Overview

• Olfactory Nerve: Scent information
• Optic Nerve: Visual information
• Oculomotor Nerve: Controls 4 eye muscles
• Trochlear Nerve: Controls 1 eye muscle
• Trigeminal Nerve: Innervates face and jaw muscles
• Abducens Nerve: Controls side-to-side eye movement
• Facial Nerve: Facial expressions
• Auditory Nerve: Hearing
• Glossopharyngeal Nerve: Tongue and pharynx
• Vagus Nerve: Key nerve connecting brain to visceral organs
• Spinal Accessory Nerve: Head and shoulder movement
• Hypoglossal Nerve: Swallowing and talking

Mnemonics for Cranial Nerves

• Names: O-O-O-T-T-A-F-A-G-V-S-H
  • Example Mnemonic: Onward old orcs! Toward the Argonath for a Great Villain! Slay Hobbits!
• Functions (Sensory, Motor, Both): S-M-M-B-M-M-B-S-B-M-M
  • Example Mnemonic: Some say marry money, but my brother says big brains matter more.

Vagus Nerve (X)

• Lengthy nerve connecting to visceral organs (heart, lungs, stomach)
• Functions:
  • Sensory: Conveys information about visceral organs to the brain
  • Motor: Sends commands from the brain to visceral organs
• Example: Relaxation response after a meal (lower heart rate, glucose storage etc.)

Balance of Autonomic Systems

• Homeostasis: Balance between sympathetic and parasympathetic systems is crucial
• Sexual Function: Requires both systems to work together

Conclusion

• Importance of parasympathetic nervous system and cranial nerves
• Understanding of how these systems contribute to vital bodily functions

Credits

• Thanks to contributors and production team for making the lecture possible.