Local and Humoral Control of Tissue Blood Flow

The amount of blood delivered per minute to various organs under normal conditions.

The brain receives 14% of the cardiac output at rest.

Kidneys receive 22% of cardiac output at rest.

Inactive muscles receive approximately 15% of the cardiac output.

Blood flow is measured in milliliters per minute per 100 grams of tissue.

A situation where a tissue lacks enough oxygen, often due to reduced blood flow or metabolic demand.

When a tissue experiences oxygen shortage, its blood flow significantly increases to deliver more oxygen.

Cyanide disrupts oxygen use in cells, causing extreme oxygen deficiency and a sevenfold increase in blood flow to the affected area.

This theory proposes that low oxygen or high metabolic activity in a tissue leads to the production of vasodilator substances, causing blood vessels to widen and increase blood flow.

This theory suggests that increased oxygen demand by a tissue directly triggers an increase in blood flow to meet the higher requirements.

The body uses complex mechanisms like the vasodilator theory and the oxygen demand theory to control blood flow to different tissues based on their needs.

Adenosine, a compound produced during metabolism, acts as a potent vasodilator, playing a role in local blood flow regulation.

The processes involved in regulating blood flow to various tissues are intricate and not fully understood.

Chemicals that cause blood vessels to widen, increasing blood flow to a specific area.

Increasing the rate of metabolism in a tissue, like during exercise, leads to increased blood flow to that area.

When tissues don't have enough oxygen, they release vasodilators, causing increased blood flow and delivering more oxygen.

A vasodilator released when oxygen levels are low. It helps bring more blood and thus more oxygen to the area.

A substance released when oxygen is low, acting as a vasodilator.

A vasodilator that increases when oxygen is low. It helps deliver more oxygen to the tissues.

Tiny muscles that control blood flow into individual capillaries.

Short vessels that connect arterioles to capillaries, playing a role in regulating blood flow.

The cyclical opening and closing of precapillary sphincters and metarterioles, a rhythmic blood flow regulation in tissues.

This theory explains local control of blood flow based on the tissue's needs for nutrients, primarily oxygen. Increased oxygen demand will lead to vasodilation, while higher oxygen levels trigger vasoconstriction.

The theory states that the amount of blood flow to a particular tissue is determined by the tissue's need for nutrients, primarily oxygen.

When oxygen levels are high or the tissue doesn't need nutrients, these tiny muscles constrict to reduce blood flow in the capillaries.

Higher oxygen concentration in the tissue theoretically leads to stronger sphincter contraction, narrowing blood flow.

Precapillary and metarteriole sphincters open to allow more blood flow, providing more oxygen and other nutrients to the tissue.

The cyclical opening and closing of precapillary sphincters in response to the tissue's needs helps to ensure an adequate supply of oxygen and nutrients.

An enzyme found in endothelial cells that produces nitric oxide (NO) from arginine and oxygen.

A gas released from endothelial cells that acts as a vasodilator, relaxing blood vessels and increasing blood flow.

An enzyme activated by NO in vascular smooth muscle cells, leading to the production of cGMP.

A molecule produced by soluble guanylate cyclase, triggering relaxation of smooth muscle cells in blood vessels.

Force exerted by blood flowing against the endothelial lining of blood vessels.

A potent vasoconstrictor released by damaged endothelial cells, causing blood vessels to narrow.

Narrowing of blood vessels, reducing blood flow.

Endothelin is released in larger amounts after injury to prevent excessive bleeding from damaged arteries.

A surgical connection directly linking a large artery and vein, bypassing smaller vessels. This is often used for dialysis access in patients with kidney failure.

The artery connected to an AVF undergoes outward remodeling, meaning its diameter increases, while its wall thickness stays the same.

The vein side of an AVF experiences outward hypertrophic remodeling, meaning both its diameter and wall thickness increase.

The sympathetic nervous system helps regulate blood flow by releasing norepinephrine and epinephrine. These hormones cause vasoconstriction, narrowing blood vessels.

A very powerful vasoconstrictor, acting like a tiny muscle squeezing blood vessels. Even a small amount can significantly raise blood pressure.

Angiotensin II mainly constricts small arterioles, potentially severely reducing blood flow to a specific area if isolated.

The process by which blood vessels adapt to changes in blood flow, pressure, or shear stress. This can include changes in diameter, wall thickness, and structure.