Ch. 21 Blood Vessels and Circulation AP2

What does Angiotensin II stimulate?

-Aldosterone production -ADH secretion -Thirst -Cardiac output and peripheral vasoconstriction

Identify 3 mechanisms that control cardiac output and blood pressure.

-Autoregulation: causes immediate, localized homeostatic adjustments. -Neural mechanisms: respond quickly to changes at specific sites. -Endocrine mechanisms: direct long-term changes.

Name and describe the effects of the two cardiac centers.

-Cardioacceleratory center: increases cardiac output. -Cardioinhibitory center: reduces cardiac output.

What's the hepatic portal system?

-Connects two capillary beds -Delivers nutrient-laden blood from capillaries of digestive organs to liver for processing -After processing in liver sinusoids (exchange vessels), blood collects in hepatic veins and empties into inferior vena cava

Describe the effects of natriuretic peptides on blood volume and blood pressure.

-Increasing sodium ion excretion by the kidneys. -promoting water loss by increasing the volume of urine produced. -reducing thirst. -Blocking the release of ADH, aldosterone, epinephrine, and norepinephrine. -Stimulating peripheral vasodilation.

Identify 6 local vasodilators

-Low O2 or high CO2 levels -Lactate -Nitric Oxide (NO) -High K+ or H+ concentrations -Chemicals released by inflammation (histamine) -Elevated local temperature

ADH responds to what situations?

-Low blood volume -High plasma osmotic concentration -Circulating angiotensin II

What are filtration and reabsorption affected by?

-Net capillary hydrostatic pressure -Net capillary colloid osmotic pressure

What contributes to the long-term restoration of blood volume?

-Recall of fluids from interstital spaces -Aldosterone and ADH promote fluid retention and reabsorption -Thirst increases -Erythropoietin stimulates red blood cell production

In the event of hemorrhaging what contributes to the short-term elevation of blood pressure?

-carotid and aortic reflexes: Increase cardiac output which increases heart rate and causes peripheral vasoconstriction. -sympathetic nervous system: Further constricts arterioles and venoconstriction improves venous return. -hormonal effects: Increase cardiac output and increase peripheral vasoconstriction.

Describe the benefits of regular, moderate exercise.

-moves low-density lipoproteins from blood to the liver, where they are converted to bile and excreted -slows the formation of plaques -reduces the risk of myocardial infarction (heart attack) by almost half -speeds recovery after a heart attack -reduces symptoms of coronary artery disease (such as angina)

Identify the largest blood vessels that attach to the heart and which circuits they are a part of.

Pulmonary Trunk - Carries blood from right ventricle to pulmonary circulation. Aorta - Carries blood from left ventricle to systemic circulation.

What's a stroke?

blockage or rupture in a cerebral artery, stops blood flow.

What role do prostaglandins play in autoregulation of blood flow within tissues?

they are released by activated platelets and white blood cells.

What is "normal" blood pressure? Hypertension? Hypotension?

"Normal" blood pressure is 120/80. Hypertension - Abnormally high blood pressure (greater than 140/90). Hypotension - Abnormally low blood pressure.

Identify the 3 layers of blood vessel walls and their characteristics.

1. Tunica intima (inner layer) - -has endothelial lining -connective tissue layer -Internal elastic membrane (in arteries) - Elastic fibers in outer margin of tunica intima 2. Tunica media (middle layer) - -Contains concentric sheets of smooth muscle in loose connective tissue -Encircles the endothelium that lines the lumen (interior space) of the blood vessel -binds to inner and outer layers -External elastic membrane -Separates tunica media from tunica externa 3. Tunica externa (outer layer) - - Anchors vessels to adjacent tissues - Contains: Collagen fibers, elastic fibers, and smooth muscle cells (in veins) -Vasa vasorum

Where is 1/3 of the blood found? Where is the other 2/3 found?

1/3 of the blood is found in heart, arteries, and capillaries. 2/3 of the blood is found in venous system. (1/3 of the venous blood is in large venous networks of the liver, bone marrow, and skin).

What's an aneurysm?

A bulge in an arterial wall that's caused by weak spot in elastic fibers. Pressure may rupture vessel.

Differentiate arteries from veins from capillaries.

Arteries - carry blood away from the heart. Veins - Return blood to the heart. Capillaries - smallest blood vessels with thin walls. Location of exchange between blood and interstitial fluid.

How is blood flow through a capillary bed regulated?

Blood flow through the capillary beds is regulated depending on the body's needs and is directed by nerve and hormone signals. The blood entering some capillary beds is controlled by small muscles, called precapillary sphincters. If the sphincters are open, the blood will flow into the associated branches of the capillary blood. If all of the sphincters are closed, then the blood will flow directly from the arteriole to the venule through the thoroughfare channel. These muscles allow the body to precisely control when capillary beds receive blood flow.

What would happen if circulatory blood pressure did not overcome total peripheral resistance?

Blood wouldn't flow, there would be too much resistance.

Which organ of the body receives top priority in terms of blood flow?

Brain

Describe age related changes in blood, the heart, and blood vessels.

Changes in blood: -decreased hematocrit -peripheral blockage by blood clot (thrombus) -pooling of blood in legs, due to venous valve deterioration Changes in the Heart: -reduced maximum cardiac output -changes in nodal and conducting cells -reduced elasticity of cardiac (fibrous) skeleton -progressive atherosclerosis -replacement of damaged cardiac muscle cells by scar tissue Changes in blood vessels: -Arteries become less elastic, pressure change can cause aneurysm -calcium deposits on vessel walls, can cause stroke or infarction -lipid deposits in tunica media and calcium salts can form atherosclerotic plaques -thrombi can form at atherosclerotic plaques

What does the vasomotor center control? Which neurotransmitters are utilized?

Control of vasoconstriction: controlled by adrenergic nerves which the neurotransmitter utilized is Norepinephrine (NE) stimulate contraction in arteriole walls Control of vasodilation: controlled by cholinergic nerves which the neurotransmitter utilized is acetylcholine (ACh) that stimulates cells to release Nitric oxide (NO) relax smooth muscle

Describe the 3 types of arteries and where they are found.

Elastic Arteries (conducting arteries)- Large vessels (pulmonary trunk and aorta), tunica media has many elastic fibers and few muscle cells, elasticity evens out pulse force. they are located closest to the heart. Muscular Arteries (distribution arteries)- most are medium-sized muscular arteries, tunica media has many muscle cells. Located between the elastic arteries and arterioles. Arterioles (resistance vessels) - Small vessels, have little to no tunica externa, have thin or incomplete tunica media. Located in the "vascular tree" it extends and branches out from an artery and leads to capillaries.

What quality do concentric sheets of smooth muscle in the tunica media give blood vessels?

Encircles the endothelium that lines the lumen (interior space) of the blood vessel.

How does epinephrine affect coronary vessels, heart rate, and contraction strength?

Epinephrine dilates coronary vessels, increases heart rate, and strengthens contractions.

Why is a pressure gradient more important than the absolute pressure generated by ventricular contraction?

Generated by the heart to overcome resistance, absolute pressure is less important than pressure gradient. Pressure gradient is the difference in pressure from one end of a vessel to the other.

What is the importance of elastic rebound?

In arterial walls and they stretch during systole, rebound (recoil to original shape) during diastole, and keep blood moving during diastole.

Calculate Flow (F)

Is proportional to the pressure gradient divided by resistance.

How does blood pressure change from arteries to capillaries to veins?

It keeps decreasing because blood needs a pressure gradient in order to flow.

Which veins have valves? How do the valves work? What can form if valves fail?

Larges veins have valves. The valves work by folds of the tunica intima, prevent blood from flowing backward, compression of veins pushes blood towards heart. If the valves fail varicose veins or hemorrhoids can form.

Compare the cardiovascular response to light vs. heavy exercise. Is blood supply to the brain affected? Why or why not?

Light exercise: -extensive vasodilation occurs, increasing circulation. -venous return increases with muscle contractions. -cardiac output rises in response to: Venous return and atrial stretching. Heavy Exercise: -Activates sympathetic nervous system -Cardiac output increases to maximum about four times resting level -Restricts blood flow to "nonessential" organs -Redirects blood flow to skeletal muscles, lungs, and heart -Blood supply to brain is unaffected

Describe the chemoreceptor reflex. Where are chemoreceptors found?

Respond to changes in carbon dioxide, oxygen, or pH levels in blood and cerebrospinal fluid. They are found in: -Carotid bodies -Aortic bodies

What is shock?

Short-term responses compensate after blood losses of up to 20 percent of total blood volume. Failure to restore blood pressure results in shock.

Compare the skeletal muscle pump (compression of veins) to the respiratory pump.

Skeletal muscle pump (compression of veins)- when leg muscles are immobilized, blood supply to the brain is reduced, and fainting may result. Respiratory pump- thoracis cavity expands during inhalation, decreasing venous pressure to the chest.

Which division of the ANS controls the contractility of arteries?

Sympathetic division

Define Systolic pressure, diastolic pressure, pulse pressure, and Mean Arterial Pressure

Systolic pressure - the peak blood pressure measured during ventricular systole. Diastolic pressure - the minimum blood pressure at the end of ventricular diastole. Pulse pressure - the difference between the systolic and diastolic pressures. Mean arterial pressure (MAP) - diastolic pressure + one-third pulse pressure. we use this to report a single blood pressure value.

What are the vasa vasorum and where are they found?

They are small arteries and veins which are found in walls of large arteries and veins.

Describe the baroreceptor reflex. Where are baroreceptors found?

They respond to changes in blood pressure. specialized receptors that monitor the degree of stretch in the walls of expandable organs. They are found in walls of: -Carotid sinuses -Aortic sinuses -Right atrium

What 3 things is peripheral resistance affect by? Then review Figure 21-7

Vascular resistance Blood viscosity Turbulence

Define vasoconstriction and vasodilation. What do these actions affect?

Vasoconstriction - Contraction of arterial smooth muscle Vasodilation - Relaxation of arterial smooth muscle These actions effect: 1. Afterload on heart 2.Peripheral blood pressure 3.Capillary blood flow

What serves as a "blood reservoir"? How does the body access this blood in response to blood loss?

Veins (capacitance vessels) act as "blood reservoirs". Systemic veins constrict (venoconstriction) in response to blood loss. -Increasing amount of blood in arterial system and capillaries.

Define venous return. How does venous pressure affect venous return?

Venous return - the amount of blood arriving at the right atrium each minute. Venous pressure effects venous return by low effective pressure and low resistance in venous systems.

Understand the dynamics of capillary exchange. Figure 21-11 is helpful.

Vital to homeostasis Materials move across capillary walls by: -Diffusion -Filtration -Reabsorption

Define collaterals, anastomosis, angiogenesis.

collaterals - multiple arteries that contribute to one capillary bed, allow circulation if one artery is blocked. anastomosis - joining of blood vessels. -arterial anastomosis: fusion of two collateral arteries. -arteriovenous anastomoses: direct connections between arterioles and venules, bypass the capillary bed. angiogenesis - formation of new blood vessels

Describe the structure and function of veins

collect blood from capillaries and return it to the heart. Compared to arteries, veins have larger diameters, thinner walls, and lower blood pressure.

Compare and contrast continuous capillaries, fenestrated capillaries, and sinusoids. Where are each found?

continuous capillaries - Supply most regions of the body, has complete endothelial lining. Found in all tissues except epithelia and cartilage. fenestrated capillaries - Have pores in endothelial lining, permit rapid exchange of water and larger solutes. Found in choroid plexus, endocrine organs, kidneys, and intestinal tract. sinusoids - Have gaps between adjacent endothelial cells, permit free exchange of water and large plasma proteins. Found in liver, spleen, bone marrow, endocrine organs.

What is edema and what can cause it?

edema is swelling caused by excess fluid trapped in your body's tissues (an abnormal accumulation of interstitial fluid). Increase in arterial blood pressure, venous pressure, or total circulatory pressure. Example: Sitting or standing too long can cause edema of the legs, especially in hot water and eating foods with too much salt can make it worse.

Where is the cardiovascular center found?

medulla oblongata

What is vasomotion and why is it beneficial?

vasomotion - contraction and relaxation cycle of precapillary sphincters. Causes blood flow in capillary beds to constantly change routes.