Chapter 14 Summary PDF

CHAPTER 14 The Cardiovascular System: Blood Vessels, Blood Flow, and Blood Pressure affect the anterior pituitary. Another portal vein links capillary beds of the gastrointestinal tract to capillary beds of the liver. The absorbed molecules transported to the liver are processed before they enter...

CHAPTER 14 The Cardiovascular System: Blood Vessels, Blood Flow, and Blood Pressure affect the anterior pituitary. Another portal vein links capillary beds of the gastrointestinal tract to capillary beds of the liver. The absorbed molecules transported to the liver are processed before they enter the general circulation. Yet another exception is the connection of two capillary beds in the kidneys not by a portal vein, but rather by a sec- 459 ond arteriole. Thus blood flows from (afferent) arterioles to (glomerular) capillaries to (efferent) arterioles to (peritubular) capillaries. This arrangement allows for finer control over the filtering of blood by the kidneys as well as a pathway for exchange between blood and kidneys after filtration has taken place. Copyright © 2017. Pearson Education, Limited. All rights reserved. SOL Go to MasteringA&P for Interactive Physiology tutorials, Interactive Flowcharts, Dynamic Study Modules, and more! VE IT! Why Does Mio Keep Falling Down? While walking to work, Mio has a sudden onset of dizziness and feels she will faint. In addition, she experiences diaphoresis (excessive sweating) and palpitations (rapid, fluttering heart). When she arrives at her office, her concerned colleagues call an ambulance. In the emergency department, the nurse and doctor make the following notes in Mio’s record: TABLE 1 Supine (laying down) 133/64 • 55-year-old female; blood pressure = 162/110 mm Hg; on metoprolol, furosemide, and propafenone. • Blood pressure dropped upon standing to 102/65 mm Hg and palpitations were observed. After receiving a 1L fluid infusion, Mio is discharged with the following patient plan: metoprolol adjusted to twice a day; discontinued furosemide, propafenone. Prescribed meclizine. However, over a period of six weeks, Mio’s symptoms become progressively worse. Mio experiences an increased number of dizzy spells, and the degree of dizziness she experiences worsens. In addition, Mio falls several times. After her last fall at the grocery store, she is admitted to the hospital. Since Mio’s primary symptom is dizziness, her doctors must take into account several body systems that might influence or cause Mio’s dizziness symptoms. Go to MasteringA&P to Solve It: Why Does Mio Keep Falling Down? in Chapters 11, 13, 14, and 19. The emergency department nurse records Mio’s symptoms: Sitting 151/73 85 Standing 103/69 103 • Patient is dizzy and faint upon standing, but never in sitting or supine positions; palpitations, muscle weakness in the legs, feeling of falling. Dizziness has worsened over 6 weeks. • Occupation: restaurant server. No history of smoking, alcohol, or illicit drug use; no history of mental illness. Body Position On Admission Blood pressure (mm Hg) Pulse (beats/min) 58 The emergency room doctor, Dr. Samuel Dorff, is concerned about Mio’s dizziness during her attempts to stand. He orders blood pressure and heart rate measurements for Mio while she is in various body positions (see Table 1 above). Why does Mio’s heart rate increase when blood pressure decreases during periods of standing? A. Gravity stimulates the heart to increase its rate in order to increase blood perfusion to the brain. B. Standing causes an increase in venous return, which increases heart rate in order to increase blood perfusion to the brain. C. Standing stimulates increased parasympathetic nervous system to increase heart rate in order to increase blood perfusion to the brain. D. The baroreceptor reflex is compensating for the drop in blood pressure in order to increase blood perfusion to the brain. *Additional questions from this Solve It activity can be assigned in MasteringA&P. CHAPTER REVIEW SUMMARY 14.1 Physical Laws Governing Blood Flow and Blood Pressure, p. 425 • The flow of blood through any vessel or network of vessels depends on the pressure gradient (∆P ) and the resistance (R) of the vessel or network: flow = ∆P>R. • The overall pressure gradient driving • The combined resistances of all blood flow through the systemic circuit is the difference between MAP and CVP. Because CVP is virtually identical to MAP, the ∆P driving blood flow for the systemic circuit is equal to MAP. • The main influence on vascular resistance is vessel radius. vessels in the systemic circuit is the total peripheral resistance (TPR). • The flow rule for the systemic circuit can be written as CO = MAP>TPR. Cardiovascular, Factors That Affect Blood Pressure Measuring Blood Pressure Stanfield, Cindy. Principles of Human Physiology, Global Edition, Pearson Education, Limited, 2017. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/mqu/detail.action?docID=5187887. Created from mqu on 2023-08-18 06:03:44. 460 CHAPTER 14 The Cardiovascular System: Blood Vessels, Blood Flow, and Blood Pressure 14.2 Overview of the Vasculature, p. 428 • All blood vessels possess a lumen that is lined by a layer of endothelial cells. • The walls of all blood vessels, except for the capillaries, contain varying amounts of smooth muscle and connective tissue. Cardiovascular, Anatomy Review: Blood Vessel Structure and Function 14.3 Arteries, p. 429 • Arteries, which conduct blood away from • • • • the heart and toward the body’s tissues, have thick walls that enable them to withstand the high pressure of blood within them, and have relatively low compliance. Arterial walls are elastic, a property that enables them to expand during systole and then recoil inward during diastole. Because of this elastic recoil, arteries function as a pressure reservoir that maintains blood flow throughout the cardiac cycle. Arterial blood pressure varies with the cardiac cycle. Systolic pressure is the maximum pressure that occurs during systole; diastolic pressure is the minimum pressure that occurs during diastole. MAP is the average arterial pressure during the cardiac cycle. 14.4 Arterioles, p. 432 • Arterioles are the passageway for blood • Copyright © 2017. Pearson Education, Limited. All rights reserved. • • • • • • to enter the capillaries; they contain relatively large amounts of smooth muscle, which enables them to expand or contract, thereby regulating blood flow through capillary beds. Arterioles are important in regulating the distribution of CO to the organs and in controlling MAP. Regulation of the distribution of blood flow among the various systemic organs is achieved through intrinsic control of organ vascular resistance. Blood flow through any given systemic organ is determined by MAP and that organ’s vascular resistance: Organ blood flow = MAP>organ resistance. Chemical changes associated with increased metabolic activity lead to vasodilation, decreased resistance, and increased blood flow (active hyperemia). The resistance of an organ can also change in response to local variations in blood flow. If blood flow becomes insufficient to meet metabolic demands (ischemia), local mechanisms induce vasodilation, with a resultant increase in blood flow (reactive hyperemia). In those tissues in which vascular smooth muscle is responsive to stretch, an increase in perfusion pressure causes arterioles to stretch, which stimulates vasoconstriction and a reduction in blood flow; this response is called a myogenic response. • Extrinsic controls of arteriole radius (and therefore total peripheral resistance) regulate MAP: MAP = CO * TPR. • Extrinsic factors include the autonomic nervous system and hormones (epinephrine, vasopressin, and angiotensin II). 14.5 Capillaries and Venules, p. 439 • Capillaries have the thinnest walls of all • • • • • the blood vessels and are highly permeable to water and small solutes. The primary function of the capillaries is to permit exchange of materials between the blood and the tissues; they are classified as continuous, fenestrated, or discontinuous, depending on their degree of “leakiness.” The movement of fluid across capillary walls is driven by the net filtration pressure, which depends on the Starling forces (capillary hydrostatic pressures, interstitial fluid hydrostatic pressures, capillary osmotic pressure, interstitial fluid osmotic pressure). Most of the fluid that is filtered from capillaries is returned to the cardiovascular system by absorption. Excess filtrate is returned to the cardiovascular system by the lymphatic system. Venules are thin-walled vessels that also participate in material exchange. Capillary Pressures and Capillary Exchange 14.6 Veins, p. 446 • Veins are large thin-walled vessels. • Most veins possess valves that permit blood to flow toward the heart but not away from it. • Veins have a high compliance and function as volume reservoirs. • Venous pressure influences arterial pressure because it affects venous return, end-diastolic volume, stroke volume, and CO. • Factors affecting venous pressure include activity of the skeletal muscle pump, activity of the respiratory pump, blood volume, and venomotor tone (which is regulated by sympathetic input to the veins). 14.7 The Lymphatic System, p. 449 • The lymphatic system is an open system of vessels starting with capillaries in the periphery. • The capillaries pick up excess filtrate to form lymph. • The lymph travels through a system of lymphatic veins to the thoracic duct, which returns the lymph to the blood in the right atrium. Interactive Physiology: Lymphatic Organs 14.8 Mean Arterial Pressure and Its Regulation, p. 449 • To supply the organs and tissues with • • • • adequate blood flow, the driving force for flow (MAP) must be maintained. MAP is controlled by both short-term and long-term extrinsic regulatory mechanisms. Short-term regulation is achieved through neural and hormonal control of cardiovascular function; long-term regulation is achieved through control of blood volume, which involves the kidney. Short-term regulation includes the baroreceptor reflex, a negative feedback system whereby baroreceptors detect changes in MAP and relay this information to the cardiovascular control center, which then acts on the autonomic nervous system to exert appropriate control over cardiovascular function. Autonomic control of MAP is accomplished through (1) sympathetic and parasympathetic input to the SA node, which controls heart rate; (2) sympathetic input to the myocardium, which controls ventricular contractility and stroke volume; and (3) sympathetic input to arteriolar smooth muscle in most tissues, which regulates total peripheral resistance. Cardiovascular, Factors That Affect Blood Pressure Cardiovascular, Blood Pressure Regulation Arterial Baroreceptor Reflex Autoregulation and Capillary Dynamics 14.9 Other Cardiovascular Regulatory Processes, p. 456 • Cardiovascular function is influenced by activity in arterial chemoreceptors, which monitor concentrations of oxygen and carbon dioxide in arterial blood. • Regulation of blood flow to the skin, which is controlled by sympathetic nerves to skin blood vessels, is important in body temperature regulation. • Cardiovascular responses to exercise are largely achieved through changes in the activity of autonomic nerves to the heart and blood vessels—changes that are orchestrated by cortical and limbic brain regions. • Blood flow to the heart and skeletal muscle is also regulated by local factors operating within these tissues. Stanfield, Cindy. Principles of Human Physiology, Global Edition, Pearson Education, Limited, 2017. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/mqu/detail.action?docID=5187887. Created from mqu on 2023-08-18 06:03:44.