Sympathetic Nervous System Lecture Notes

Introduction

• Focus on sympathetic nervous system (SNS)
• Review of previous video on autonomic nervous system
  • Different types of ganglia
  • Intro to sympathetic and parasympathetic systems

Thoracolumbar Outflow

• From T1 to L2 (sometimes to L3)
• Preganglionic motor neurons are in the lateral gray horn

Ganglia

• Collection of cell bodies in the peripheral nervous system
  • Chain ganglia: side of spinal cord
  • Collateral ganglia: front of spinal cord

Cervical Ganglia

• Superior Cervical Ganglion (SCG), Middle Cervical Ganglion (MCG), Inferior Cervical Ganglion (ICG)
• Nerve fibers from T1 to T3 move up to SCG
  • Synapse on cell bodies
  • Form carotid plexus

Target Organs and Effects

• Eye
  • Dilator pupillae muscle: pupillary dilation for far vision
  • Ciliary muscle: accommodation for far vision
• Salivary Glands
  • Decreased blood flow, increased mucin production
• Lacrimal Glands
  • Decreased lacrimation
• Heart
  • Increase heart rate (positive chronotropic action)
  • Increase contractility and cardiac output
• Esophagus
  • Decrease peristalsis and secretions
• Lungs
  • Dilation of bronchioles
  • Decreased secretions, vasoconstriction of bronchial arteries

Splanchnic Nerves and Associated Ganglia

Greater Splanchnic Nerve (T5-T9)

• Celiac Ganglion
  • Stomach: Inhibit peristalsis, decrease secretions, constrict blood vessels
  • Liver: Glycogenolysis
  • Pancreas: Decrease insulin, increase glucagon
  • Adrenal Medulla: Release norepinephrine and epinephrine

Lesser Splanchnic Nerve (T10-T11)

• Aorticorenal Ganglion
  • Kidney: Decrease urine production, increase renin release

Least Splanchnic Nerve (T12)

• Renal Plexus
  • Support kidney effects

Lumbar Splanchnic Nerves (L1-L3)

• Inferior Mesenteric Ganglion
  • Decrease peristalsis in descending and sigmoid colon

Hypogastric Plexuses

• Superior Hypogastric Plexus: Affects bladder and internal urethral sphincter
• Inferior Hypogastric Plexus
  • Gonads: Sympathetic control for ejaculation and uterine contractions

Higher Brain Control

• Hypothalamus and limbic nuclei influence SNS
• Some cortical control (e.g., biofeedback) possible

Conclusion

• Review of sympathetic nervous system effects
• Encouragement to engage with educational content and support channels

These notes cover the key points and pathways associated with the sympathetic nervous system as discussed in the lecture. The discussion includes anatomy, physiological effects, and higher-level brain influences on sympathetic activity.