Lecture Notes: Autonomic Motor Pathways
Introduction
- Focus on motor pathways of the autonomic nervous system (ANS).
- Distinction between somatic and autonomic motor pathways.
Somatic Nervous System Recap
- Pathway: Starts in the central nervous system (CNS), typically cerebral cortex.
- Travels through: Brain, spinal cord, to effector organs (exclusively skeletal muscles).
- Pathway characteristics: Simple direct pathway, one neuron from CNS to skeletal muscle.
Autonomic Nervous System Overview
- Two divisions: Parasympathetic and Sympathetic.
- Effector organs: Heart, glands, smooth muscles, blood vessels, adipose tissue.
- Control: Involuntary, no conscious control.
Autonomic Nervous System Characteristics
- Neuronal Pathway: Two neurons involved, linked by a synapse.
- Parasympathetic: Longer first neuron.
- Sympathetic: Longer second neuron.
- Neuron Names:
- Pre-ganglionic neuron
- Post-ganglionic neuron (synapse at a ganglion).
Anatomical Differences
- Parasympathetic Division
- Origins: Cranial (brain, cranial nerves) and sacral regions.
- Cranial nerves involved: III, VII, IX, X.
- Vagus Nerve (X): Critical for parasympathetic responses, conducts 75% of parasympathetic commands.
- Sympathetic Division
- Origins: Thoracic and lumbar regions.
- Sympathetic Trunk: Parallel to spinal cord, used for sympathetic pathways.
Sympathetic Trunk
- Structure: Sympathetic trunk ganglia (gray matter bulges).
- Function: Facilitates travel of sympathetic motor pathways.
- Pathway from spinal cord, synapses at sympathetic trunk, travels to effector organ.
Pathway Summary
- Parasympathetic: Cranial nerves, especially vagus nerve, used to reach effector organs.
- Sympathetic: Utilizes spinal nerves and sympathetic trunk.
Conclusion
- Overview of pathway roles and structures.
- Future content: Functionality of ANS in controlling body and reflexes.
This summary consolidates understanding of the autonomic motor pathways, highlighting the differences and characteristics of parasympathetic and sympathetic divisions.