Meaning
Small, muscular blood vessels that branch off from arteries and regulate the overall resistance to blood flow in the body. By altering their diameter, resistance arterioles determine how much blood reaches individual tissues and establish systemic blood pressure. Under chronic stress, these vessels remain constricted, forcing the heart to pump against higher pressure.
Flow Regulation
Smooth muscle cells in the walls of these small vessels respond to local and systemic signals to adjust their diameter. When the sympathetic nervous system is highly active, it releases neurotransmitters that cause these muscles to contract. This contraction reduces the flow of blood to non-essential organs to prioritize muscles and the brain, raising the overall pressure within the system.
Tissue Remodeling
Chronic constriction triggers structural changes in the walls of the vessels. The muscle cells grow larger to withstand the high pressure, which permanently narrows the internal opening of the vessel. This narrowing makes it difficult for the vessels to dilate even when the stress hormone levels return to normal.
Perfusion Cost
Maintaining blood flow through these narrowed pathways requires the heart to work harder. The increased resistance elevates systemic blood pressure, which damages other parts of the vascular system.
