Notes on Sympathetic Nervous System
Origin of the Sympathetic Nervous System
- The sympathetic nervous system originates primarily from the thoracic spinal cord, specifically from the segments T1 and T2.
- These spinal nerves play a crucial role in the sympathetic response involving fight-or-flight reactions.
Key Functions of T1 and T2
- T1 and T2 vertebral levels are key in supplying the structures in the head and neck region.
- They influence physiological functions such as heart rate, sweat gland activity, and pupil dilation.
- Horner's syndrome is a condition characterized by:
- Miosis: Constricted pupils.
- Ptosis: Drooping of the upper eyelid.
- Anhidrosis: Absence of sweating on the affected side of the face.
- This syndrome indicates a disruption in the sympathetic innervation pathway, often involving T1 and T2 lesions or other causes affecting sympathetic outflow.
Pathway of Sympathetic Neurons
- The first-order sympathetic neurons originate in the hypothalamus and must traverse down to the preganglionic neurons located in the spinal cord segments T1 and T2.
- Understanding this path is crucial for tracing the effects of sympathetically mediated changes in the body.
Summary
- Remember that T1 and T2 are pivotal for sympathetic supply in the head and neck as well as crucial in clinical conditions like Horner's syndrome. The regulation initiated by the hypothalamus outlines the significance of the central nervous connection to peripheral effects.