Final answer:
Dilation of a blood vessel by cells within the vessel exemplifies autoregulation, a local mechanism for controlling blood flow and pressure independent of systemic signals. This process, involving vasodilation and vasoconstriction based on smooth muscle stretch response, maintains tissue homeostasis.
Step-by-step explanation:
The dilation of a blood vessel by substances produced by the cells within the blood vessel is an example of autoregulation. This local regulatory mechanism operates independent of systemic signals like those from the nervous or endocrine systems. In situations where blood flow through a vessel is low, the resulting minimal stretch of the vessel's smooth muscle causes the muscle to relax, leading to vasodilation. Conversely, when blood flow is high and the vessel is excessively stretched, the smooth muscle contracts, prompting vasoconstriction that reduces blood flow. These adjustments in vessel diameter affect the resistance to blood flow, as governed by Poiseuille's law, and play a crucial role in maintaining stable blood flow and blood pressure to protect tissues from under- or over-perfusion.