Chap 19

Describe the role of chemoreceptor reflexes in adjusting cardiovascular activity.

the chemoreceptor reflexes respond to changes in carbon dioxide, oxygen, or pH levels in blood and CSF. stimulation of these chemoreceptors triggers coordinated adjustments in cardiovascular and respiratory activity.

B.How is blood pressure maintained in veins to counter the force of gravity?

Assisted by the presence of valves in the veins, which prevent backflow of the blood, the contraction of the surrounding skeletal muscles squeeze venous blood toward the heart.

B.Describe autoregulation as it relates to cardiovascular function.

It involves local factors changing the pattern of blood flow within capillary beds in response to chemical changes and interstitial fluids.

Explain the hormonal regulation of blood pressure and blood volume.

when blood pressure and volume decrease below normal, the immediate response is the release of epinephrine and norepinephrine from the adrenal medullae, stimulating cardiac output and peripheral vasoconstriction. other important hormones in the long-term response is antidiuretic hormone, angiotensin, erythropoietin, and aldosterone. excessive blood volume triggers a response through its effects on the walls of the heart. when the heart walls are abnormally stretched during diastole, cardiac muscle cells release natriuretic peptides.

Discuss the movement of fluids between capillaries and interstitial spaces.

when hydrostatic pressure is greater, fluid moves from capillaries to interstitial space. when osmotic pressure is greater, fluid flows from interstitial space to capillaries.

Describe the factors that determine blood flow.

•Cardiac output •Central regulation •Peripheral resistance •Venous return

19.2 A.List the five general classes of blood vessels.

The five general classes of blood vessels are arteries, arterioles, capillaries, venules, and veins.

19.5 Review A.Neural and endocrine regulatory mechanisms influence which factors?

Neural and endocrine regulatory Mechanisms influence heart rate stroke volume peripheral resistance in Venus pressure.

Describe the venous system, and indicate the distribution of blood within the cardiovascular system.

Pressure and blood flow in veins. Venoconstriction: reduces amount of blood in venous system. Maintains blood volume. Controlled by the vasomotor center in the medulla oblongata. Venous return: on average, the amount of blood arriving at the right atrium each minute equals to the cardiac output

19.3 A. Identify the two types of capillaries with a complete endothelium.

The two types of capillaries with a complete endothelium are continuous capillaries and fenestrated capillaries.

D. Distinguish among efferent vessels, afferent vessels, and exchange vessels.

Efferent vessels (arteries) carry blood away from the heart, afferent vessels (veins) carry blood to the heart, and exchange vessels (capillaries) exchange nutrients, dissolved gases, and wastes between the blood and interstitial fluid.

Describe the structures of capillaries and their functions in the exchange of dissolved materials between blood and interstitial fluid.

•Continuous capillary Permits diffusion of water, small solutes, and lipid-soluble materials Prevents loss of blood cells and plasma proteins Some selective vesicular transport •Fenestrated (fenestra, window) capillary Contains "windows," or pores, penetrating endothelial lining Permits rapid exchange of water and larger solutes •Sinusoids (sinusoidal capillaries) Permit more water and solute (plasma proteins) exchange

Explain the roles of pressure, resistance, and venous return in cardiac output.

1. Blood pressure: Pressure within the cardiovascular system as a whole. Arterial pressure: is much higher than venous pressure, Must push blood greater distance through smaller vessels. 2.Resistance: Force that opposes movement. Peripheral resistance, Resistance of the arterial system as a whole, Increases as vessels get smaller. 3. Venous return: Amount of blood arriving at the right atrium each minute, On average, equal to the cardiac output.

Describe the factors that influence total peripheral resistance.

1. Vascular resistance: The vessel length ( -Increase in vessel length = increased surface area = increased in friction or resistance) and the vessel luminal diameter 2. Blood Viscocity: •Blood viscosity is about five times that of water -Due to cells and plasma proteins -Viscosity is normally stable oDisorders affecting hematocrit or plasma composition change viscosity and affect peripheral resistance. 3. Turbulence- •Increased turbulence = increased resistance = slow blood flow

B. Describe a capillary.

A capillary is a small blood vessel, located blood vessel, located between an arteriole and a venule, whose thin wall permits exchange between blood and interstitial fluid by diffusion.

C.Which would reduce peripheral resistance: an increase in vessel length or an increase in vessel diameter?

An increase in vessel diameter would reduce peripheral resistance.

A.Define blood flow, and describe its relationship to blood pressure and peripheral resistance.

Blood flow is the volume of blood flowing per unit of times through a vessel of group of vessels; it is directly proportional to arterial pressure And inversely proportional to peripheral resistance.

Explain central regulation, autoregulation, and baroreceptor reflexes in response to changes in blood pressure and blood composition.

Central regulation involves both neural and endocrine mechanisms. Autoregulation involves local changes in the pattern of blood flow within capillary beds. These changes are due to precapillary sphincters that open and close in response to chemical changes in the IF. baroreceptor reflexes respond to changes in blood pressure. arterial baroreceptors are located in the carotid sinuses and the aortic arch

B.Define edema.

Edama is an a normal accumulation of interstitual fluid in peripheral tissues.

B. At what sites in the body are fenestrated capillaries located?

Fenestrated capillaries are located where solutes as large as small peptides move freely into and out of the blood. These sites include endocrine glands, the choroid plexus of the brain, absorptive areas of the intestine, and filtration areas of the kidneys.

Review 19.8 A.Under what general conditions would fluid move into a capillary?

Fluid moves into a capillary whenever blood colloid Osmotic pressure is greater than capillary hydrostatic pressure.

19.4 A.Why are valves located in veins but not in arteries?

In the arterial system, pressures are high enough to keep the blood moving away from the heart and through arteries and capillaries in the venous system, blood pressure is too low to keep the blood moving back toward the heart. Valves in veins prevent blood from flowing backward whenever the venous pressure drops.

B.Explain the equation R ∝ 1/r4.

It states that resistance is inversely proportional to the fourth power of the vessel radius. This means that a small change in vessel diameter result in a large change in resistance.

C. Explain the function of baroreceptor reflexes.

Response to changes in blood pressure. When blood pressure increases the cardiac centers decreased cardiac output in the vasomotor Center is inhibited, resulting in vasodilation; When blood pressure decreases, the cardiac centers increase cardiac output and vasomotor is stimulated, resulting in vasoconstriction.

Review 19.9 A. Define Perfusion

Tissue perfusion is blood flow to tissues that is sufficient to deliver adequate oxygen and nutrients.

D. What factors are involved in the formation of varicose veins?

Varicose veins are sagging, swollen superficial veins in the size and legs. They results from the pooling of blood due to gravity and the failure of venous valves.

C. Why is it beneficial for capillary pressure to be very low?

Very low capillary pressure is beneficial because it allows time for diffusion between the blood and the surrounding interstitial fluid.

19.14 A.What are blood islands, and from which cells do they form?

What islands are aggregations of embryonic cells scattered within the yolk sac that form blood vessels and blood cells during embryonic development these islands give rise to hematopoietic stem cells and hemangioblasts.

Distinguish among the types of blood vessels on the basis of their structure and function.

1.Arteries •Elastic arteries Large vessels close to the heart that stretch and recoil when heart beats, Include pulmonary trunk, aorta, and branches •Muscular arteries Medium-sized arteries, Distribute blood to skeletal muscles and internal organs 2.​Arterioles Poorly defined tunica externa, Tunica media is only 1-2 smooth muscle cells thick 3.​Capillaries Only blood vessels to allow exchange between blood and interstitial fluid, Very thin walls allow easy diffusion 4.​Venules Small veins, Those smaller than 50 µmlack a tunica media and resemble expanded capillaries, Collect blood from capillaries 5.​Veins •Medium-sized veins Range from 2 to 9 mm in internal diameter, Thin tunica media with smooth muscle cells and collagen fibers, Thickest layer is tunica externa with longitudinal collagen and elastic fibers •Large veins Contain all three vessel wall layers, Thin tunica media surrounded by thick tunica externa, Include superior and inferior venae cavae and tributaries

Distinguish between the pulmonary and systemic circuits, and identify afferent and efferent blood vessels.

1.Pulmonary circuit •To and from gas exchange surfaces in the lungs Right atrium (entry chamber) Collects blood from systemic circuit To right ventricle to pulmonary circuit Pulmonary circuit Pulmonary arteries to pulmonary capillaries to pulmonary veins 2.​Systemic circuit •To and from rest of body Left atrium •Receives blood from pulmonary circuit •To left ventricle to systemic circuit ​Systemic circuit •Systemic arteries to systemic capillaries to systemic veins •Arteries (carry blood away from the heart) Also called efferent vessels •Veins (carry blood to the heart) Also called afferent vessels

C. Identify the conditions that would shift the balance between hydrostatic and osmotic forces.

Any condition that affects either blood pressure or osmotic pressure's in the blood or tissues will shift the balance between hydrostatic and osmotic forces.

B.Which is greater: arterial pressure or venous pressure?

Arterial pressure Is much higher than venous pressure because it must push blood a greater distance and through progressively smaller and thinner vessels.

B.In a healthy person, where is blood pressure greater: in the aorta or in the inferior vena cava? Explain.

In a healthy person, blood pressure is greater in the Arorta than in the inferior vena cava. If the pressure were higher in the inferior vena cava then in the Aurora, blood would flow in the reverse direction.

Review 19.1 A. Describe the pulmonary circuit.

The pulmonary circuit transports blood from the right ventricle through the pulmonary arteries, capillaries in the lungs, pulmonary veins an returns it to the left atrium.

C.Which chamber of the heart receives blood from the systemic circuit?

The right atrium receives blood from the systemic circuit.

C. Describe the distribution of total blood volume in the body.

The systemic Venous system And systemic artial system Contain 64 and 13% of the total blood volume, respectively. The remaining volume is contained in the heart 7%, pulmonary circulation 9%, and systemic capillaries 7%.

B.Describe the systemic circuit.

The systemic circuit transports blood through the arteries, capillaries, amd veins of the body from the left ventricle to the right atrium. Blood returning to the heart from the systemic circuit must complete the pulmonary circuit before it re-enters the systemic circuit.

B. What is the function of hemangioblasts?

They remodel blood islands first into capillary networks and then into larger artial and Venus networks.

19.6 A. List the factors that contribute to total peripheral resistance.

Total peripheral resistance reflects a combination of vascular resistance, vessel length, vessel luminal Diameter, Blood velocity, and turbulence.