blood flow

What law is related to Blood Flow (Q)?

Ohm's Law

According to the Poisseuile-Hagen formula, Flow (Q) is directly proportional to the pressure (P) and the fourth power of the…?

Radius (r⁴)

Resistance is inversely proportional to the ___ ___ of the radius.

fourth power

What vessels are the main site of resistance to blood flow?

Arterioles

Resistance is directly proportional to the ___ of the tube.

Length (L)

Resistance is directly proportional to the ___ of the fluid.

Viscosity (V)

Blood is how many times more viscous than water?

3 times

What type of blood flow is characterized by smooth, parallel layers?

Laminar flow

What type of blood flow is characterized by chaotic, swirling eddies?

Turbulent flow

Velocity of blood flow is ___ related to the blood vessel's cross-sectional area.

inversely

Where is blood flow velocity the slowest?

Capillaries (where cross-sectional area is highest)

Velocity of blood flow decreases as it moves from…?

aorta -> arteries -> capillaries

Velocity of blood flow increases as it moves from…?

veins -> right atrium

Regulation of arteriolar diameter is divided into what two main categories?

Local regulation and Systemic regulation

Systemic regulation is divided into Neuronal mechanisms and…?

Circulating vasoactive substances

Sympathetic vasoconstrictor fibers release what neurotransmitter?

Norepinephrine (NA)

Sympathetic vasoconstrictor fibers act on what receptors?

alpha-adrenergic receptors

The continuous discharge from the VMC in the medulla oblongata causing partial VC is called…?

Sympathetic VC tone

Sympathetic vasodilator fibers to coronary vessels act on what receptors?

B1 adrenergic receptors

Sympathetic vasodilator fibers to skeletal muscle are ___ and secrete ___.

cholinergic

The sympathetic vasodilator system to skeletal muscles originates in the…?

Cerebral cortex

Parasympathetic vasodilator fibers supply what organs?

Genital organs (sacral outflow)

Impulses from pain receptors that travel anti-dromically to skin arterioles causing VD are called…?

Antidromic vasodilator fibers

The skin vasodilation caused by antidromic fibers is called the…?

Flare reaction

What are the main circulating vasoconstrictor substances?

Catecholamines, RAS, Vasopressin

What are the main circulating vasodilator substances?

Kinins, ANP

The two Kinin systems are the Plasma kallikrein system and the…?

Tissue kallikrein system

What is the product of the Plasma kallikrein system?

Bradykinin

What is the product of the Tissue kallikrein system?

Kallidin

Kinins cause potent ___ of arterioles by acting on B2 receptors.

vasodilatation

Besides vasodilation, Kinins also increase capillary permeability and stimulate…?

Pain sensation (on B1 receptors)

What is ANP?

Atrial natriuretic peptide

Where is ANP secreted from?

Atria, ventricles, and brain

ANP is secreted in response to ___ right atrial pressure or ___ blood volume.

increased

ANP causes marked natriuresis (Na+ excretion) and…?

Diuresis (water excretion)

ANP opposes the actions of Aldosterone and…?

Angiotensin II

What is the effect of Noradrenaline on blood vessels?

Potent vasoconstriction (by stimulating alpha-adrenergic receptors)

What does the Renin-Angiotensin System (RAS) respond to?

Decreased blood pressure / renal ischemia

Where is Renin secreted from?

Kidney (JGA - Juxtaglomerular apparatus)

Where is Angiotensinogen produced?

Liver

What enzyme converts Angiotensin I to Angiotensin II, and where?

ACE (Angiotensin-converting enzyme)

What is the primary effect of Angiotensin II on arterioles?

Strong direct arteriolar vasoconstriction

What hormone does Angiotensin II stimulate the release of from the adrenal cortex?

Aldosterone

What is another name for Vasopressin?

ADH (Antidiuretic hormone)

Where is Vasopressin (ADH) secreted from?

Posterior pituitary gland

Vasopressin acts on what receptors in vascular smooth muscle to cause vasoconstriction?

V1 receptors

Vasopressin acts on what receptors in the nephrons to increase water reabsorption?

V2 receptors

Local regulation of arterioles includes 02 tension, Metabolites, Autoregulation, and…?

Substances released by the endothelium

What is Autoregulation?

The ability of a tissue to regulate its blood flow according to its need

What is the Myogenic theory of autoregulation?

Stretch of vascular smooth muscle causes contraction

What is the Metabolic theory of autoregulation?

Accumulation of vasodilator metabolites causes vasodilation

Increased CO2 tension, acidosis, K+, and adenosine are all…?

Vasodilator metabolites

An increase in blood flow to active tissues due to metabolite accumulation is…?

Active hyperemia

An increase in blood flow after a temporary occlusion is…?

Reactive hyperemia

What vasodilator substance is released by the endothelium and derived from arachidonic acid?

Prostacyclin

What potent vasodilator is synthesized from arginine by NO synthase?

EDRF (Nitric Oxide - NO)

What are Endothelins (ET)?

A group of very potent vasoconstrictor polypeptides released by the endothelium

Endothelins are released in response to…?

Stretching of blood vessels

What effect do endothelins have on the heart?

Positive inotropic and chronotropic effects