How does resistance affect blood flow?

How does resistance affect blood flow?

Resistance is a force that opposes the flow of a fluid. In blood vessels, most of the resistance is due to vessel diameter. As vessel diameter decreases, the resistance increases and blood flow decreases. Very little pressure remains by the time blood leaves the capillaries and enters the venules.

What has the greatest impact on peripheral resistance to blood flow?

However, the site of the most precipitous drop, and the site of greatest resistance, is the arterioles. This explains why vasodilation and vasoconstriction of arterioles play more significant roles in regulating blood pressure than do the vasodilation and vasoconstriction of other vessels.

How can peripheral resistance affect the blood pressure?

Peripheral Vascular Resistance The greater the compliance of an artery, the more effectively it is able to expand to accommodate surges in blood flow without increased resistance or blood pressure. Veins are more compliant than arteries and can expand to hold more blood.

What happens when you increase peripheral vascular resistance?

Vascular resistance is used to maintain organ perfusion. In certain disease states, such as congestive heart failure, there is a hyper-adrenergic response, causing an increase in peripheral vascular resistance. Prolonged increases in blood pressure affect several organs throughout the body.

What are the three important sources of resistance to blood flow?

There are three important sources of resistance: vessel length, blood viscosity, and vessel diameter. Let’s discuss blood vessel length first. Resistance, as it pertains to total blood vessel length is easy: The longer the blood vessel, the greater the resistance.

What has the greatest impact on total peripheral resistance?

The last factor affecting resistance is blood vessel diameter. This factor is the most variable of the three and has the greatest impact on resistance. So the peripheral blood vessels dilate to increase blood flow to the limbs.

What factors affect blood flow?

The variables affecting blood flow and blood pressure in the systemic circulation are cardiac output, compliance, blood volume, blood viscosity, and the length and diameter of the blood vessels.

What factors affect peripheral circulation?

Peripheral vascular disease is the reduced circulation of blood to a body part, other than the brain or heart, due to a narrowed or blocked blood vessel. Risk factors include diabetes, obesity, smoking and a sedentary lifestyle.

What does peripheral resistance do?

Peripheral resistance is the resistance of the arteries to blood flow. As the arteries constrict, the resistance increases and as they dilate, resistance decreases.

Which factor will increase the flow of blood?

It is by elevation of stroke volume or heart rate, or both. This will increase blood pressure and enhance the flow of blood. Such factors are sympathetic stimulation, the catecholamines norepinephrine and epinephrine, increased levels of calcium ions, and thyroid hormones.

What is the relationship between blood flow pressure and resistance?

In the arterial system, as resistance increases, blood pressure increases and flow decreases. In the venous system, constriction increases blood pressure as it does in arteries; the increasing pressure helps to return blood to the heart.

What is the difference between pulmonary and peripheral vascular resistance?

If referring to resistance within the pulmonary vasculature, this is called pulmonary vascular resistance (PVR). Peripheral vascular resistance (systemic vascular resistance, SVR) is the resistance in the circulatory system that is used to create blood pressure, the flow of blood and is also a component of cardiac function.

What is systemic vascular resistance (SVR)?

Systemic vascular resistance (SVR), also known as total peripheral resistance (TPR), is the amount of force exerted on circulating blood by the vasculature of the body. Three factors determine the force: the length of the blood vessels in the body, the diameter of the vessels, and the viscosity of the blood within them.

How does the radius of blood vessels affect resistance to flow?

This equation shows that modifying the radius of the vessel has drastic effects on the resistance to blood flow. As the vessel dilates (radius increases), the resistance is divided by the change to the fourth power; this goes for a decrease in radius as well, such as during an adrenergic state (e.g., exercise) when blood pressure must increase.

What is the total resistance of the entire circulatory system?

Therefore, the resistance of the entire systemic circu-lation, called the total peripheral resistance, is about 100/100, or 1 PRU. In conditions in which all the blood vessels through-out the body become strongly constricted, the total peripheral resistance occasionally rises to as high as 4 PRU.