The systems that are only innervated by the sympathetic nervous system are:
1. Most blood vessels
- Sympathetic innervation of blood vessels plays a crucial role in regulating blood flow and pressure in the body. The sympathetic nervous system can cause vasoconstriction (narrowing of blood vessels) to increase blood pressure or vasodilation (widening of blood vessels) to increase blood flow to certain areas.
2. Arrector pili muscles in the skin
- Arrector pili muscles are small muscles attached to hair follicles in the skin. When these muscles contract in response to sympathetic stimulation, they cause the hairs to stand on end, which is commonly known as goosebumps. This response is part of the fight-or-flight reaction of the sympathetic nervous system.
Therefore, the sweat glands in the trunk and the bronchioles in the lungs are not exclusively innervated by the sympathetic nervous system. Sweat glands are innervated by both the sympathetic and parasympathetic nervous systems, while bronchioles in the lungs receive innervation from both the sympathetic and parasympathetic divisions as well.
