GNUR 156 EXAM 3: Blood Vessels, Blood Flow, and Blood Pressure

Flow rule

Blood flow equals pressure difference divided by resistance.

Mean arterial pressure

The average pressure that drives blood through the circulatory system.

Relationship between resistance and vessel radius

Resistance is inversely related to the fourth power of the vessel’s radius. A small change in radius causes a large change in resistance.

Vasoconstriction

When blood vessels narrow, resistance increases and blood flow decreases.

Vasodilation

When blood vessels widen, resistance decreases and blood flow increases.

Total peripheral resistance

The combined resistance of all blood vessels in the systemic circulation.

Arteries

Carry blood away from the heart under high pressure and are elastic.

Arterioles

Small vessels that control resistance and regulate blood flow and blood pressure.

Capillaries

Microscopic vessels where gases, nutrients, and wastes are exchanged between blood and tissues.

Venules

Collect blood from capillaries and begin its return to the heart.

Veins

Return blood to the heart under low pressure and contain valves to prevent backflow.

Arteries as pressure reservoir

Arteries expand when the heart pumps blood and recoil between beats to maintain continuous blood flow.

Veins as a volume reservoir

Veins can stretch easily and hold about sixty percent of the body’s blood at rest.

Pulse pressure

The difference between systolic pressure and diastolic pressure.

Mean arterial pressure formula

Diastolic pressure plus one-third of the pulse pressure.

Korotkoff sounds

The sounds heard with a stethoscope when measuring blood pressure using a cuff.

Vascular compliance

How easily a blood vessel can stretch when pressure changes.

Arteriolar tone

The normal baseline level of contraction in arteriolar smooth muscle.

Active hyperemia

An increase in blood flow to tissues that are more metabolically active.

Reactive hyperemia

A temporary increase in blood flow after a period of restricted blood supply.

Metabolic substances that cause vasodilation

Increased carbon dioxide, hydrogen ions, potassium ions, adenosine, and nitric oxide cause local vasodilation.

Substances that cause vasoconstriction

Low oxygen, endothelin, and high sympathetic stimulation cause local vasoconstriction.

Myogenic response

Automatic constriction of a blood vessel when it is stretched, helping to keep blood flow constant.

Sympathetic control of arterioles

Norepinephrine binds to alpha receptors on smooth muscle causing vasoconstriction, which raises total peripheral resistance and blood pressure.

Epinephrine effects on arterioles

Epinephrine can bind to beta-two receptors in skeletal and heart muscle to cause vasodilation and increase blood flow.

Vasopressin (antidiuretic hormone)

A hormone that causes vasoconstriction and helps the kidneys retain water, increasing blood pressure.

Angiotensin two

A strong hormone that causes vasoconstriction and raises blood pressure.

Intrinsic control of blood flow

Local regulation of vessel diameter based on the tissue’s metabolic needs.

Extrinsic control of blood flow

Regulation of vessel diameter by the nervous system and hormones to control blood flow and pressure throughout the body.

Arteriole radius control extrinsically

Sympathetic nerves and hormones like epinephrine, vasopressin, and angiotensin two adjust arteriolar radius.

Capillary wall structure

Composed of a single layer of endothelial cells to allow efficient diffusion.

Continuous capillaries

Capillaries with small gaps that allow water and small solutes to pass through.

Fenestrated capillaries

Capillaries with larger pores that allow proteins and sometimes cells to move through.

Metarteriole

A small vessel that directly connects an arteriole to a venule, bypassing capillaries if needed.

Precapillary sphincter

A ring of smooth muscle that controls blood flow into capillaries.

Filtration

The movement of fluid out of capillaries into surrounding tissues due to pressure.

Absorption

The movement of fluid from tissues back into capillaries due to osmotic forces.

Capillary hydrostatic pressure

The blood pressure within capillaries that pushes fluid out of the capillary.

Plasma oncotic pressure

The osmotic pressure created by plasma proteins that pulls fluid into the capillary.

Net filtration pressure

The combined effect of hydrostatic and osmotic pressures that determines fluid movement across capillary walls.

Lymphatic system

A network of vessels that returns excess filtered fluid and proteins from tissues back into the blood circulation.

Skeletal muscle pump

Muscle contractions squeeze veins, pushing blood toward the heart.

Respiratory pump

Pressure changes during breathing move blood from the abdomen toward the chest and heart.

Venous tone

Sympathetic stimulation of smooth muscle in veins that increases pressure and helps return blood to the heart.

Determinants of mean arterial pressure

Heart rate, stroke volume, and total peripheral resistance together determine mean arterial pressure.

How blood pressure changes through the vasculature

Blood pressure is highest in the arteries and decreases steadily through arterioles, capillaries, and veins, reaching its lowest point in the venae cavae.

Hypotension

Abnormally low blood pressure that may cause inadequate blood flow to tissues.

Hypertension

Abnormally high blood pressure that puts stress on the heart and blood vessels.

Baroreceptors

Stretch receptors located in the aortic arch and carotid arteries that detect changes in blood pressure.

Baroreceptor reflex

A rapid feedback system that adjusts heart rate and vessel diameter to stabilize blood pressure.

Cardiovascular control center

The area in the medulla oblongata of the brain that regulates heart and blood vessel function.

Sympathetic activation

Increases heart rate, stroke volume, and vasoconstriction, which raises blood pressure.

Parasympathetic activation

Decreases heart rate and lowers blood pressure.

Chemoreceptors

Sensors that detect carbon dioxide and oxygen levels in the blood to adjust heart rate and blood vessel tone.

Thermoregulatory response

When body temperature rises, blood vessels in the skin dilate to release heat.

Fibrinogen

A plasma protein that is converted to fibrin during blood clotting, helping to form a stable clot.