Flashcards in Chapter 17 - Guyton Deck (21):
Factors affecting tissue needs?
delivery of oxygen to tissues; delivery of nutrients such as glucose, amino acids, etc.; removal of carbon dioxide, hydrogen, and other metabolites from tissue; transport various hormones and other substances to different tissues (flow is closely related to metabolic rate of tissues)
Which tissue receives the most blood flow?
Decreases in oxygen availability to tissues _________ tissue blood flow.
Two major theories for local blood flow.
vasodilator theory (greater metabolism or decreased availability of oxygen increases vasodilation), oxygen demand theory (absence of oxygen due to it being used causes vasodilation as vessels relax)
Flow (Q) through a blood vessel is determined by the pressure difference (deltaP) between the two ends of the vessel and the resistance (R) of the vessel.
Explain the Vasodilator Theory.
increase tissue metabolism-->increase release of vasodilators-->decrease arteriole resistance-->increase blood flow
Name some vasodilators.
adenosine, CO2, lactic acid, ADP compounds, histamine, K ions, H ions
Explain the Oxygen Demand Theory.
increase tissue metabolism or decrease oxygen delivery to tissues-->decrease tissue oxygen concentration-->decrease arteriole resistance-->increase blood flow
ability of a tissue to maintain blood flow relatively constant over a wide range of arterial pressures
as arterial pressure is decreased, oxygen or nutrient delivery is decreased resulting in a release of vasodilator
as arterial pressure falls, the arterioles have an intrinsic property to dilate in response to decreases in wall tension
Blood flow autoregulation in the kidneys.
feedback system between the tubules and the arterioles
Brain blood flow autoregulation.
controlled by carbon dioxide and hydrogen ion concentrations
tension=pressure x radius
How is long-term local blood flow regulated?
changing the degree of vascularity of the tissues (size and number of vessels)
Important stimulus for regulating tissue vascularity.
growth of new blood vessels
small peptides such as vascular endothelial cell growth factors (VEGF), fibroblast growth factor (FGF), and angiogen
Angiogenic factors released from?
ischemic tissue, rapidly growing tissue, tissue with high metabolic rates
Humoral regulation of blood flow vasoconstrictors.
norepinephrine, epinephrine, angiotensin, vasopressin, endothelin