Chapter 17: Control of Cardiovascular Function Porth 3rd
End-systolic volume
residual blood volume following contraction
Afterload
resistance to ejection of blood from heart
Because it is a closed system, the effective function of the circulatory system requires that the outputs of both sides of the heart pump the ____ amount of blood over time.
same
Heart valves
semilunar and atrioventricular
The difference between the end-diastolic and end-systolic volumes (approximately 70 mL) is called the ____.
stroke volume
The neural control of the circulatory system occurs primarily through the _____ and ______ divisions of the autonomic nervous system.
sympathetic, parasympathetic
The ____ circulation consists of the left heart, the aorta and its branches, the capillaries that supply the brain and peripheral tissues, and the systemic venous systems and the vena cava.
systemic
Diastole
Resting phase of cardiac cycle
Pericardium
Sac that covers the heart
How is blood vessel diameter controlled?
Sympathetic innervation via α-adrenergic receptors is excitatory in that they produce vasoconstriction; β-adrenergic receptors are inhibitory in that they produce vasodilation. Smooth muscle contraction and relaxation also occur in response to local tissue factors such as lack of oxygen, increased hydrogen ion concentrations, and excess carbon dioxide. Nitric oxide acts locally to produce smooth muscle relaxation and regulate blood flow.
The ____ function as collection chambers for blood and the _____ are the main pumping chambers of the heart.
atria, ventricles
The ____ refers to the maximum percentage of increase in cardiac output that can be achieved above the normal resting level.
cardiac reserve
Pressure in the right atrium is called the ____.
central venous pressure
The key factor that retrains fluid loss from the capillaries is the _______ pressure generated by the plasma proteins.
colloidal osmotic
Systole
contractile phase of cardiac cycle
The circulatory system can be divided into two parts: the ____ circulation and the ____ circulation.
pulmonary, systemic
What are the factors that travel in the bloodstream that will regulate blood flow? Indicate if each factor is a dilator or a vasoconstrictor.
1. Norepinephrine - potent vasoconstrictor 2. Epinephrine - mild vasoconstriction or dilation depending on the receptor type found in target tissue. 3. Angiotensin II - powerful vasoconstrictor 4. Histamine - powerful vasodilator and can increase permeability 5. Serotonin - vasoconstrictor 6. Bradykinin - vasodilator 7. Prostaglandins - vasodilator or vasoconstrictor depending on the type of prostaglandin.
The stroke volume is the amount of blood ejected with every contraction of the ventricle. It is broken down into quarters. What is the approximate amount of the stroke volume per quarter?
60%, 20%, 20%, and little blood. Approximately 60% of the stroke volume is ejected during the first quarter of systole, and the remaining 40% is ejected during the next two quarters of systole. Little blood is ejected from the heart during the last quarter of systole, although the ventricle remains contracted.
______ of blood flow is mediated by changes in blood vessel tone due to changes in flow through the vessel or by local tissue factors.
Autoregulation
Cardiac output (CO) is used to measure the efficiency of the heart as a pump. What is the equation used to express CO?
CO = SV X HR. The efficiency of the heart as a pump often is measured in terms of cardiac output (CO) or the amount of blood the heart pumps each minute. The CO is the product of the stroke volume (SV) and the heart rate (HR), and can be expressed by the equation: CO = SV X HR. AV stands for atroventricular and EF stands for ejection fraction. Neither is part of the equation for CO.
As the needs of the body change, the heart's ability to increase output necessarily needs to change too. This ability in the heart depends on what factors?
Cardiac contractility, Heart Rate, Preload, and Aferload.The heart's ability to increase its output according to body needs mainly depends on four factors: the preload, or ventricular filling; the afterload, or resistance to ejection of blood from the heart; cardiac contractility; and the heart rate. Cardiac reserve doses not add to the heart's ability to increase its output.
The dispensability of the blood vessel is the major factor in which of the vessel's characteristics?
Compliance. Compliance refers to the total quantity of blood that can be stored in a given portion of the circulation for each millimeter rise in pressure. Compliance reflects the distensibility of the blood vessel. Wall tension, laminar blood flow, and resistance are not major factors in the distensibility of the blood vessel.
When the intracranial pressure rises to levels that equal intra-arterial pressure, blood vessels to the vasomotor center become compressed, initiating the central nervous system ischemic response. This is known as the ___.
Cushing Reflex
When intracranial pressure (ICP) equals intracranial pressure, the central nervous system ischemic response is initiated. This response is directed at raising arterial pressure above intracranial pressure (ICP), thereby re-establishing blood flow to the vasomotor center of the brain. What is this response called?
Cushing Reflex. The Cushing reflex is a special type of central nervous system reflex resulting from an increase in intracranial pressure. When the intracranial pressure rises to levels that equal intra-arterial pressure, blood vessels to the vasomotor enter becomes compressed, initiating the central nervous system ischemic response. The purpose of this reflex is to produce a rise in arterial pressure to levels above intracranial pressure so that the blood flow to the vasomotor center can be re-established. Should the intracranial pressure rise to the point that the blood supply to the vasomotor center becomes inadequate, vasoconstrictor tone is lost, and the blood pressure begins to fall. The elevation in blood pressure is associated with the Cushing reflex is usually of short duration and should be considered a protective homeostatic mechanism. The brain and other cerebral structures are located within the rigid confines of the skull, with no room for expansion, and any increase in intracranial pressure tends to compress the blood vessels that supply the brain.
____ is marked by ventricular relaxation and filling.
Diastole
The ___ mechanism allows the heart to accommodate various levels of venous return.
Frank-Starling
The lymph system correlates with the vascular system without actually being a part of the vascular system. Among other things, the lymph system is the main route for the absorption of fats from the gastrointestinal system. The lymph system empties into the right and left thoracic ducts, which are the points of juncture with the vascular system. What are these points of juncture?
Junctions of the subclavian and internal jugular veins. The lymph capillaries drain into larger lymph vessels that ultimately empty into the right and left thoracic ducts. The thoracic ducts empty into the circulation at the junctions of the subclavian and internal jugular veins. The lymphatic system only joins the vascular system in one place.
Nitroglycerin is the drug of choice in treating angina. What does nitroglycerin release into the vascular smooth muscle of the target tissues?
Nitric oxide. The fact that nitric oxide is released into the vessel lumen (to inactivate platelets) and away from the lumen (to relax smooth muscle) suggests that it protects against both thrombosis and vasoconstriction. Nitroglycerin, which is used in treatment of angina, produces its effects by releasing nitric oxide in vascular smooth muscle of the target tissues.
Resistance to flow is determined by the blood vessels and the blood vessel itself. An equation has been developed for understanding the relationship between the diameter of the blood vessel, the viscosity of the blood, and resistance. What is the equation called?
Poiseuille's Law. The blood vessels and the blood vessel itself constitute resistance to flow. A helpful equation for understanding the relationship between resistance, blood vessel diameter (radius), and blood viscosity factors that affect blood flow was derived by the French physician Poiseuille more than a century ago. The other laws do not address resistance to flow.
Colloidal osmotic pressure acts differently than the osmotic effects of the plasma proteins. What is its action?
Pulls fluid back into the capillary. The osmotic pressure caused by the plasma proteins in the blood tends to pull fluid from the interstitial spaces back into the capillary. This pressure is termed colloidal osmotic pressure to differentiate the osmotic effects of the plasma proteins, which are suspended colloids, from the osmotic effects of substances such as sodium and glucose, which are dissolved crystalloids.
What is the importance of the Frank-Starling mechanism?
The anatomic arrangement of the actin and myosin filaments in the myocardial muscle fibers is such that the tension or force of contraction depends on the degree to which the muscle fibers are stretched just before the ventricles begin to contract. The maximum force of contraction and cardiac output is achieved when venous return produces an increase in left ventricular end-diastolic filling (i.e. preload) such that the muscle fibers are stretched about two and one-half times their normal resting length. When the muscle fibers are stretched to this degree, there is optimal overlap of the actin and myosin filaments needed for maximal contraction.
The heart and blood vessels receive both sympathetic and parasympathetic innervation from neural control. What controls the parasympathetic-mediated slowing of the heart rate?
The cardioinhibitory center. The medullary cardiovascular neurons are grouped into three distinct pools that lead to sympathetic innervation of the heart and blood vessels and parasympathetic innervation of the heart. The first two, which control sympathetic-mediated acceleration of heart rate and blood vessel tone, are called the vasomotor center. The third, which controls parasympathetic-mediated slowing of heart rate, is called the cardioinhibitory center.
What are the factors involved in regulating the flow of blood and how are they related?
The most important factors governing the flow of blood in the cardiovascular system are pressure, resistance, and flow. Blood flow (F) through a vessel or series of blood vessels is determined by the pressure difference (Δ P) between the two ends of a vessel (the inlet and the outlet) and the resistance (R) that blood must overcome as it moves through the vessel. (F = ΔP/R).
Downstream peripheral pulses have a higher pulse pressure because the pressure wave travels faster than the blood itself. What occurs in peripheral arterial disease?
The pulse decreases rather than increases with amplitude. With peripheral arterial disease, there is a delay in the transmission of the reflected wave so that the pulse decreases rather than increases in amplitude.
Blood volume is dictated by age and body weight. Neonates have a higher blood volume per kilogram than do adults. What is the blood volume range per kilogram in an adult?
The total blood volume is a function of age and body weight, ranging from 85 to 90 mL/kg in the neonate and from 70 to 75 mL/kg in the adult.
The velocity of blood in the circulatory system varies considerably between large vessels and capillaries. Normally, when fluid flows from a large vessel to a smaller vessel, the velocity increases, but this does not occur in the circulatory system. Why and for what purpose?
This is because, even though each individual capillary is very small, the total cross-sectional area of all the systemic capillaries greatly exceeds the cross-sectional area of other parts of the circulation. Because of this large surface area, the slower movement of blood allows ample time for exchange of nutrients, gases, and metabolites between the tissues and the blood.
The troponin complex is one of a number of important proteins that regulate actin-myosin binding. Troponin works in a striated muscle to help regulate calcium-mediated contraction of the muscle. Which of the troponin complexes are diagnostic of a myocardial infarction?
Troponin T and Troponin I. In clinical practice, the measurement of the cardiac forms of troponin T and troponin I are used in the diagnosis of myocardial infarction. Troponin C is not diagnostic of a myocardial infarction. Troponin A is not one of the troponin complexes.
____ blood flow may predispose to clot formation as platelets and other coagulation factors are exposed to the endothelial lining of the vessel.
Turbulent
____ in the veins of extremities prevent retrograde flow with the help of skeletal muscles that surround and intermittently compress the leg veins to move blood forward to the heart.
Valves
Preload
Ventricular filling
____ is the resistance to flow caused by the friction of molecules in a fluid.
Viscosity
End-diastolic volume
Volume in heart following passive filling phase
In the heart and other vital structures, ______ channels exist between some of the smaller arteries.
anastomotic
The ____ and ____ valves control the movement of blood out of the ventricles.
aortic, pulmonic
The ____ represents the energy that is transmitted from molecule to molecule along the length of the vessel.
arterial pressure pulse
Water-filled junctions, called the ______, join the capillary endothelial cells and provide a pathway for passage of substances through the capillary wall.
capillary pores
The efficiency of the heart as a pump often is measured in terms of the ____ or the amount of blood the heart pumps each minute.
cardiac output
With peripheral arterial disease, there is a delay in the transmission of the reflected wave so that the pulse _____ in amplitude.
decreases
The total quantity of blood that can be stored in a given portion of the circulation for each millimeter rise in pressure is termed compliance, and reflects the ____ of the blood vessel.
distensibility
The stroke volume divided by the end-diastolic volume is the ____ fraction.
ejection
The aorta is highly _____ and as such stretches during systole to accommodate the blood that is being ejected from the left heart during systole.
elastic
The ____ determines the frequency with which blood is ejected from the heart.
heart rate
Cardiac output
heart rate x stroke volume
The term ____ refers to the principles that govern blood flow in the circulatory system.
hemodynamics
An increase in local blood flow is called _____.
hyperemia
Because flow is directly related to the radius, small changes in vessel radius can produce ____ changes in flow to an organ or tissue.
large
The ____ pressure of the pulmonary circulation allows blood to move through the lungs more slowly, which is important for gas exchange.
low
The neural control centers for the integration and modulation of cardiac function and blood pressure are located bilaterally in the _____.
medulla oblongata
The term _____ refers to the functions of the smallest blood vessels, the capillaries, and the neighboring lymphatic vessels.
microcirulation
Myocardium
muscular wall of heart
The circulatory system delivers ___ and nutrients needed for metabolic processes to the tissues, carries ____ products from the tissues to the kidneys and other excretory organs for elimination, and circulates electrolytes and ___ needed to regulate body function.
oxygen, waste, hormones
The electrical activity, recorded on the electrocardiogram, _____ the mechanical events of the cardiac cycle.
precedes
The ____ circulation consists of the right heart, the pulmonary artery, the pulmonary capillaries, and the pulmonary veins.
pulmonary
Wall tension is inversely related to wall thickness, such that the _____ the vessel wall, the lower the tension.
thicker
The outermost layer of a vessel, the ____ is composed primarily of loosely woven collagen fibers.
tunica adventitia
The innermost layer of a vessel, the _____ consists of a single layer of flattened endothelial cells.
tunica intima
The middle layer of a vessel, the _____, is largely a smooth muscle layer.
tunica media
Blood flow in the circulatory system depends on a blood ____ that is sufficient to fill the blood vessels and a ____ difference across the system that provides the force to move blood forward.
volume, pressure