2026-04-16_Sympathetic and Parasympathetic Nervous Systems

Course Details

  • Course Code: IMC533

  • Institution: University at Buffalo

  • Professor: Dr. Stuart Inglis

Learning Objectives

By the end of the session, students will be able to:

  • Distinguish between the sympathetic and parasympathetic nervous systems:
      - Compare similarities and differences in form and function.

  • Trace the paths that sympathetic nerve fibers take to their destinations.

  • Identify the four cranial nerves that contain parasympathetic nerve fibers.

  • Describe the structure of the pelvic splanchnic nerves.

  • Describe the morphology of sympathetic and parasympathetic nerves supplying the thorax, abdomen, and pelvis.

  • Detail the effects of sympathetic and parasympathetic stimulation throughout the body with an emphasis on the abdomen.

Overview of the Autonomic Nervous System

  • Categories:
      - Sympathetic Nervous System
      - Parasympathetic Nervous System

  • Target Cells:
      - Skeletal Muscle Cells: innervated by somatic nervous system.
      - Smooth Muscle Cells: innervated by autonomic nervous system (both sympathetic and parasympathetic).

Sympathetic Nervous System

  • Key Structures:
      - Cervical Sympathetic Ganglia:
        - Superior
        - Middle
        - Inferior
      - Sympathetic Chain Ganglia:
        - Gray rami to spinal nerves
        - Postganglionic fibers to spinal nerves, specifically for innervating the integumentary system.
      - Preganglionic Neurons and Postganglionic Neurons:
      - PONS involvement in sympathetic nerves.

Innervation Areas

  • Targets of sympathetic nerves:
      - Eye
      - Salivary Glands
      - Heart
      - Lungs
      - Liver
      - Gallbladder
      - Stomach
      - Spleen
      - Pancreas
      - Small and Large Intestine
      - Rectum
      - Uterus
      - Ovary
      - Penis
      - Scrotum
      - Adrenal Medulla
      - Kidney
      - Urinary Bladder

Structure of Sympathetic Pathways

  • Preganglionic Neurons: originate in the lateral horn of the spinal cord (T1-L2).

  • Postganglionic Neurons: located in the sympathetic chain or collateral ganglia.

  • Notable nerves:
      - Greater Splanchnic Nerve
      - Celiac Ganglion
      - Inferior Mesenteric Ganglion
      - Coccygeal Ganglia (fused Co₁)

Parasympathetic Nervous System

  • Key Structures:
      - Cranial Nerves:
        - N III (Oculomotor): Ciliary ganglion
        - N VII (Facial): Pterygopalatine & Submandibular ganglia
        - N IX (Glossopharyngeal): Otic ganglion
        - N X (Vagus): extends to multiple organs
      - Pelvic Splanchnic Nerves: originates from S2-S4, innervates pelvic organs and part of large intestine.

Target Organs of Parasympathetic Nerves

  • Lacrimal Glands

  • Heart

  • Lungs

  • Liver

  • Gallbladder

  • Stomach

  • Spleen

  • Pancreas

  • Small Intestine

  • Rectum

  • Uterus

  • Penis

  • Ovary

  • Scrotum

  • Kidney

  • Bladder

Function of Autonomic Nervous System

  • Sympathetic Stimulation:

  • Increases heart rate & blood pressure.

  • Dilates bronchioles for improved airflow.

  • Inhibits digestive functions.

  • Parasympathetic Stimulation:

  • Decreases heart rate.

  • Stimulates digestion & promotes glandular secretion.

  • Constriction of bronchioles (less airflow needed during rest).

Key Connections and Implications

  • Celiac Plexus: major nerve plexus suppling abdominal organs.

  • Autonomic Plexuses: network of sympathetic and parasympathetic fibers intertwining to peripherals such as the gastrointestinal tract.

  • Enteric Nervous System: a subdivision of the ANS that governs the functions of the gastrointestinal system, possesses its own reflex activities independent of CNS.

Summary of Nerve Pathways

  • Sympathetic and Parasympathetic Pathways: how they harmonize to regulate bodily functions through opposing actions (fight or flight vs. rest and digest).

Diagrams and Visual Aids

  • Understanding the anatomy of the sympathetic and parasympathetic systems through diagrams (e.g., ganglia locations, peripheral targets).

References

  • Connexions/Openstax for visual representations of autonomic pathways.

  • Carl Toldt, anatomical insights on nerve functions in the ANS.

Conclusions

  • Recap on the integration between sympathetic and parasympathetic systems in maintaining homeostasis.

  • Acknowledge the implications in health, disease, and therapeutic practices.

Additional Notes

  • Emphasis on real-world applications: understanding patients' nervous system-related disorders.

  • Ethical considerations in manipulation of autonomic pathways for treatment.

End of Presentation

  • The presentation concludes with a review of the sympathetic and parasympathetic systems' complexities and intricacies as essential elements of human physiology.