Autonomic Nervous System Structure and Origin

Study Notes

Afferent neurons carry sensory information from receptors in the skin and organs to the central nervous system
- Also known as sensory neurons
- Cell bodies are located outside of the spinal cord
Efferent neurons carry motor information from the brain to the peripheral nervous system
- Also known as motor neurons
- Cell bodies are located in the ventral horn of the spinal cord

Autonomic Division regulates involuntary bodily responses
- Relays information from the dorsal root ganglion
Somatic Division controls voluntary movement by skeletal muscles
- Relays motor information via the ventral root
Sympathetic Nervous System
- Originates in the thoracolumbar region of the spinal cord
Parasympathetic Nervous System
- Originates in the craniosacral region of the spinal cord
Sympathetic Nervous System
- Controls "fight or flight" responses
- Uses norepinephrine and acetylcholine as neurotransmitters
Parasympathetic Nervous System
- Controls "rest and digest" responses
- Uses acetylcholine as a neurotransmitter

Definition: Collection of neurons outside the central nervous system
Function: Acts as a distributing center
Types:
- Paravertebral ganglia (lateral)
  - Present on both sides of the vertebral column
  - Relay of the sympathetic nervous system
- Collateral ganglia
  - Present midway between the spinal cord and viscera
  - Relay of the sympathetic and parasympathetic nervous systems
- Terminal ganglia
  - Present near or inside the viscera
  - Relay of the parasympathetic nervous system

Head and Neck:
- Eye:
  - Pupil dilation (mydriasis) due to contraction of the dilator pupillae muscle
  - Elevation of the upper eyelid (widening of the palpebral fissure)
  - Decreased tear secretion of the lacrimal gland
- Salivary glands: Decreased salivary secretions
Thorax: (Heart and Lung)
- Heart:
  - Increased excitability and rate of conduction
  - Positive inotropic effect (increase in force of contraction)
  - Positive chronotropic effect (increase in heart rate)
  - Vasodilation of coronary vessels
- Lung:
  - Bronchodilation (relaxation of bronchial muscles)
  - Vasoconstriction of pulmonary vessels