Anatomy: Ch 19
List the phases of the cardiac cycle
Atrial systole, atrial diastole, ventricular systole, and ventricular diastole
Explain the function of baroreceptor reflexes
Baroreceptor reflexes respond to changes in blood pressure. The baroreceptors, located in the walls of the carotid sinuses, aortic sinuses and right atrium, monitor the degree of stretch at those sites
Describe the roles of the natriuretic peptides
Excessive stretching of the right atrium during diastole causes the release of atria natriuretic peptide (ANP). Excessive stretching of the ventricles during diastole causes the release of brain natriuretic peptide (BNP). The roles of these peptides are to trigger responses whose combined effects act to decrease blood volume and blood pressure. As blood volume and blood pressure decrease, natriuretic peptide production stops.
Under what general conditions would fluid move into a capillary?
Fluid moves into a capillary whenever blood colloid osmotic pressure (BCOP) is greater than capillary hydrostatic pressure (CHP)
Caffeine has effects on conducting cells and contractile cells that are similar to those of NE. What effect would drinking large amounts of caffeinated beverages have on the heart rate?
Like NE, caffeine acts directly on the conducting system and contractile cells of the heart, increasing the rate at which they depolarize. Drinking large amounts of caffeinated beverages would therefore increase the heart rate.
Is the heart always pumping blood when pressure in the left ventricle is rising? Explain.
No. When pressure in the left ventricle first rises, the heart is contracting but blood is not leaving the heart. During this initial phase of contraction, called the period of isovolumetric contraction, both the AV valves and the semilunar valves are closed. The increase in pressure is the result of the cardiac muscle contracting. When the pressure in the ventricle exceeds that in the aorta, the aortic semilunar valves are forced open, and blood is rapidly ejected from the ventricle.
List the important features of the ECG, and indicate what each represents
P wave (atrial depolarization), the QRS complex (ventricular depolarization), and the T wave (ventricular repolarization)
Describe the sites and actions of the cardioinhibitory and cardioacceleratory centers
The cardioacceleratory center in the medulla oblongata activates sympathetic neurons to increase heart rate; the cardioinhibitory center (also in the medulla oblongata) controls the parasympathetic neurons that slow heart rate
Which structures collect blood from the myocardium, and into which heart chamber does this blood flow?
coronary veins collect the blood from the myocardium and carry it to the right atrium
When a chamber is relaxed, which phase is it in?
diastole
From superficial to deep, name the layers of the heart wall
epicardium. myocardium, and endocardium
Neural and hormonal regulation influence which factors?
heart rate, stroke volume, peripheral resistance, and venous pressure
Is the apex located on the superior or inferior aspect of the heart?
inferior
What are the two phases of ventricular systole?
isovolumetric contraction and ventricular ejection
Name the four cardiac chambers
left atrium, right atrium, left ventricle, and left atrium
Describe the tissue layers of the epicardium
outer mesothelium and an underlying layer of areolar tissue that attaches directly to the myocardium
Define the cardiac cycle
period between the start of one heartbeat and the beginning of the next
Damage to the semilunar valve on the right side of the heart would affect blood flow to which vessel?
pulmonary trunk
List the three stages of an action potential in a cardiac muscle cell
rapid depolarization, plateau, and repolarization
What effect does an increase in the respiratory rate have on CO2 levels?
reduces CO2 levels
What is the function of chemoreceptor reflexes?
respond to decreasing pH and oxygen levels and increasing CO2 levels in the blood and cerebrospinal fluid (CSF). These reflexes stimulate responses by the cardiovascular centers to increase vasoconstriction, cardiac output and blood pressure that increase pH and oxygen levels and decrease CO2 levels
The anterior view of the heart is dominated by which structure?
right atrium and right ventricle
Why is it beneficial for capillary pressure to be very low?
so blood can flow slowly and allow time for diffusion between the blood and the surrounding interstitial fluid
Give the alternate terms for heart contraction and heart relaxation
systole and diastole
Define automaticity
the ability of cardiac muscle tissue to contract without neural or hormonal stimulation
Define cardiac regurgitation
the abnormal back flow of blood into the atria when the ventricles contract, and it is prevented by the chordae tendineae and papillary muscles
Why can cardiac tamponade be a life-threatening condition?
the accumulating fluid within the pericardial cavity restricts heart movement
What do semilunar valves prevent?
the back flow of blood into the ventricles
Describe the heart's location in the body
the heart is surrounded by the pericardial sac in the anterior mediastinum, deep to the sternum and superior to the diaphragm
If the cells of the SA node failed to function, how would the heart rate be affected?
the heart would continue to beat but at a slower rate; the AV node would act as the pacemaker
Define mediastinum
the region between two pleural cavities that contains the heart along with the great vessels (large arteries and veins attached to the heart), thymus, esophagus, and trachea
Explain the formula R= 1/r^4
the resistance (R) is inversely proportional to the fourth power of the vessel radius (r). This means that a small change in vessel diameter results in a large change in resistance
Describe the purpose of a stent
wire-mesh tubes that prop open the natural blood vessel, creating a conduit to restore blood flow. Without adequate blood flow to the cardiac muscle, the tissue would die
List the arteries and veins of the heart
Arteries: left coronary artery, anterior inter ventricular artery, right coronary artery, marginal arteries, circumflex artery, and posterior interventricular artery. Veins: great cardiac vein, anterior cardiac veins, posterior cardiac vein, middle cardiac vein, and small cardiac vein
Compare arteriosclerosis with atherosclerosis
Arteriosclerosis is any thickening and toughening of arterial walls; atherosclerosis is a type of arteriosclerosis characterized by changes in the endothelial lining and the formation of fatty deposits (plaque) in the tunica media
What effect would an increase in venous return have on the stroke volume?
An increase in in venous return would stretch the heart muscle. The more the heart muscle is stretched, the more forcefully it will contract (to a point). The more forceful the contraction, the more blood the heart will eject with each beat (stroke volume). Therefore, increased venous return would increase the stroke volume (if all other factors are constant)
What effect would an increase in sympathetic stimulation of the heart have on the end-systolic volume (ESV)?
An increase in sympathetic stimulation of the heart would increase heart rate and force of contraction. The end-systolic volume (ESV) is the amount of blood that remains in a ventricle after a contraction (systole). The more forcefully the heart contracts, the more blood it ejects. Therefore, increased sympathetic stimulation results in a lower ESV.
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. (An increase in vessel length would increase peripheral resistance.)
Identify the conditions that would shift the balance between hydrostatic osmotic forces
Any condition that affects either blood pressure or osmotic pressures in the blood or interstitial fluid will shift the balance between hydrostatic and osmotic forces
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 vessels
Compare bradycardia with tachycardia
Bradycardia is a heart rate below 60 beats per minute; tachycardia is a heart rate above 100 beats per minute
Why does tetany not occur in cardiac muscle?
Cardiac muscle has a long refractory period that continues until relaxation is well under way. As a result, another action potential cannot arrive quickly enough for summation to occur, and thus tetany cannot occur
Why is it so important that cardiac tissue contain many mitochondria and capillaries?
Cardiac tissue is metabolically active and dependent on mitochondrial activity for ATP and local capillaries for obtaining oxygen and nutrients
Describe auto regulation as it pertains to cardiovascular function
Cardiovascular auto regulation involves local factors changing the pattern of blood flow within capillary beds in response to chemical changes in interstitial fluids
Describe circulatory shock, progressive shock, and irreversible shock
Circulatory shock occurs when blood loss exceeds about 35 percent of the total blood volume. Circulatory shock involves a series of positive feedback loops that are initiated after homeostasis has been disrupted. Progressive shock is the next stage after circulatory shock. It too is a series of positive feedback loops that accelerate tissue damage. Irreversible shock is the fatal stage that occurs if the positive feedback loops initiated during progressive shock are not broken
What prevents the AV valves from swinging into the atria?
Contraction of the papillary muscles pulls on the chordae tendineae, which prevent the AV valves from swinging into the atria
Describe what happens to blood flow during elastic rebound
During elastic rebound, some blood in the aorta is driven forward into the systemic circuit, and some is forced back toward the let ventricle and into the coronary arteries
Identify the hormones responsible for short-term regulation of decreasing blood pressure and blood volume.
Epinephrine and norepinephrine from the adrenal medullae provide short-term regulation of decreasing blood pressure and blood volume
Why is it important for impulses from the atria to be delayed at the AV node before they pass into the ventricles?
If the impulses from the atria were not delayed at the AV node, they would be conducted through the ventricles so quickly by the bundle branches and Purkinje cells that the ventricles would begin contracting before the atria had finished contracting. As a result, the ventricles would not be as full of blood as they could be, and the pumping action of the heart would be less efficient.
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 aorta than in the inferior vena cava. If the pressure were higher in the inferior vena cava than in the aorta, blood flow in the reverse direction.
Compute Joe's stroke volume if his end-systolic volume (ESV) is 40 mL and his end-diastolic volume (EDV) is 125 mL.
SV = EDV - ESV, so SV = 125 - 40 = 85 mL
Describe slow calcium channels and the significance of their activity
Slow calcium channels are voltage-gated calcium channels that open slowly and remain open for a relatively long period - about 175 msec. When they are open, the entry of calcium ions into the cell roughly balances balances the loss of sodium ions through the active transport of sodium ions. As a result, the membrane potential remains near 0 mV for an extended period.
Why is it a potential problem if the heart beats too rapidly?
The amount of blood that the heart pumps is proportional to the amount of blood that enters it. A heart that is beating too rapidly does not have adequate filling time, and it pumps less blood; peripheral tissues can be damaged by inadequate blood flow
Compare the anterior cardiac veins to the posterior cardiac vein
The anterior cardiac veins drain the anterior surface of the right ventricle and empty into the right atrium. The posterior cardiac vein drains the area (posterior surface of the left ventricle) supplied by the circumflex artery
Name and describe the shallow depressions and grooves found on the heart's external surface
The anterior inter ventricular sulcus marks the boundary between the left and right ventricles on the heart's anterior surface; the shallower posterior interventricular sulcus marks the boundary between the left and right ventricles on the posterior surface; the coronary sulcus is a deep groove that marks the border between the atria and the ventricles
Define end-diastolic volume (EDV) and end-systolic volume (ESV)
The end-diabolic volume (EDV) is the amount of blood a ventricle contains at the end of diastole, just before a contraction begins; the end-systolic volume (ESV) is the amount of blood that remains in the ventricle at the end of ventricular systole
Name the immediate and long-term problems related to profuse blood loss
The immediate short-term problem during hemorrhaging is maintaining adequate blood pressure and peripheral blood flow; the long-term problem is restoring normal blood volume
Cite the locations of chemoreceptors
carotid bodies, in the aortic bodies, and on the ventrolateral surfaces of the medulla oblongata
Why is the left ventricle more muscular than the right ventricle?
The more muscular left ventricle must generate enough force to propel blood throughout the body (except the lungs), whereas the right ventricle must generate only enough force to propel blood the short distance to the lungs
Compare the structure of the tricuspid valve with that of the pulmonary valve
The tricuspid valve is composed of three relatively large flaps (cusps); the pulmonary valve is made up of here smaller half-moon shaped cusps
Define tissue perfusion
Tissue perfusion is blood flow to tissues that is sufficient to deliver adequate oxygen and nutrients
List the factors that contribute to the total peripheral resistance
Total peripheral resistance reflects a combination of vascular resistance, vessel length, vessel diameter, blood viscosity, and turbulence
Why must blood flow to visceral organs be reduced during exercise?
Unless compensatory vasoconstriction occurs in "nonessential" organs such as those of the digestive system vasodilation in skeletal muscles would cause a potentially dangerous decrease in blood pressure and blood flow throughout the body during exercise
Calculate the mean arterial pressure for a person whose blood pressure is 125/70.
Using the formula MAP = diastolic pressure + (125 - 70)/3 which equals 70 + 18.3 or 88.3 mm Hg.
How does the kidney respond to vasoconstriction of the renal artery?
Vasoconstriction of the renal artery would decrease both blood flow and blood pressure at the kidney. In response, the kidney would increase the amount of renin it releases, which in turn would increase the level of angiotensin II. The angiotensin II would bring about increased blood pressure and increased blood volume
Why is ventricular fibrillation fatal?
Ventricular fibrillation, which causes the condition known as cardiac arrest is fatal because the ventricles merely quiver and do not pump blood into the systemic circulation
Describe the changes in cardiac output and blood flow during exercise
cardiac output increases and blood flow to skeletal muscles increases at the expense of blood flow to less essential organs
What is coronary ischemia?
a condition in which the blood supply of the coronary arteries is reduced
Define heart failure
a condition in which the heart can no longer meet the oxygen and nutrient demands of peripheral tissues
Describe the respiratory pump.
a mechanism by which a reduction of pressure in the thoracic cavity during inhalation assists venous return to the heart
Define electrocardiogram
a recording of the electrical activities of the heart over time
Define edema
an abnormal accumulation of interstitial fluid in peripheral tissues
Identify the compensatory mechanisms that respond to blood loss
an increase in cardiac output, a mobilization of venous reserves, peripheral vasoconstriction, and the release of hormones that promote the retention of fluids and the maturation of erythrocytes
The great veins and arteries are attached to which aspect of the heart?
base of the heart
Define blood flow, and describe its relationship to blood pressure and peripheral resistance
blood flow is the volume of blood flowing per unit of time through a vessel or group of vessels; it is directly proportional to blood pressure and inversely proportional to peripheral resistance