Lecture Exam 3
How does caffeine cause positive chronotropic effects?
It blocks the enzyme that degrades cAMP, thereby prolonging the effects of epinephrine
What two factors are used to calculate cardiac output? Select all that apply: A. Heart rate B. Blood pressure C. Stroke volume D. Mean arterial pressure
A. Heart rate C. Stroke volume
What's a possible defense vs MI? How does it work?
Anastomosis is when two blood vessels connect, for example the circumflex artery and the right coronary artery, so if one gets blocked, the other can take over blood delivery
__________ is the amount of blood pumped by the left ventricle with each beat. A. Cardiac output B. Preload C. Afterload D. Stroke volume
D. Stroke volume
How does the delay of the impulse at the atrioventricular node contribute to cardiac function?
It gives the atria time to contract fully, and fill ventricles 2/3rds full, before sending the signal
How does HR change in elderly?
It increases
What is the average HR for an adult male?
64-72 bpm
What NT produces negative chronotropic effects?
Acetylcholine
How does regular exercise affect cardiac reserve?
It increases it, by decreasing resting HR and increasing SV
Describe the baroreceptor reflex
1. Change in BP is detected by the baroreceptors in the aorta and internal carotid artery 2. Baroreceptors signal to the medulla oblongata 3. If bp is low, medulla oblongata signals to the cardioinhibitory centers, which signal to the parasympathetic nerves, causing them to decrease ach release and other parasympathetic activity, creating a negative feedback loop 4. If bp is low, medulla oblongata signals to cardioacceleratory centers, which signals to the sympathetic nerves to increase HR, creating a negative feedback loop
Describe the pathway of cardiac signalling
1. SA node initiates action potential across both atria 2. Atria begin to depolarize, AV node delays signal to the ventricles, allowing ventricles to fill 2/3rds 3. Atria contract, and electric impulse travels through AV node through AV bundle, bundle branches, and purkinje fibers 4. Purkinje fibers distribute wave of depolarization to the ventricular myocytes 5. Ventricles contract via signal traveling from apex up toward the base of heart
Why is afterload important to cardiac function?
Afterload represents the resistance within the arteries to the flow of blood ejected from the ventricles. If uncompensated, if afterload increases, flow will decrease. In order for the heart to maintain adequate flow to overcome increasing afterload, it must pump more forcefully. This is one of the negative consequences of high blood pressure or hypertension.
A patient with hypovolemic shock is given IV fluids. IV fluids will help _________ cardiac output by: A. decrease; decreasing preload B. increase, increasing preload C. increase, decreasing afterload D. decrease, increasing contractility
B. increase, increasing preload
Select the statement below that best describes cardiac afterload: A. It's the volume amount that fills the ventricles at the end of diastole. B. It's the volume the ventricles must work against to pump blood out of the body. C. It's the amount of blood the left ventricle pumps per beat. D. It's the pressure the ventricles must work against to open the semilunar valves so blood can be pumped out of the heart.
D. It's the pressure the ventricles must work against to open the semilunar valves so blood can be pumped out of the heart.
How do gap junctions and intercalated disks aid contraction of the heart?
Gap junctions within the intercalated disks allow impulses to spread from one cardiac muscle cell to another, allowing sodium, potassium, and calcium ions to flow between adjacent cells, propagating the action potential, and ensuring coordinated contractions.
What causes bradycardia?
Good physical condition, sleep
Define bradycardia
HR is less than 60 bpm
What is included in the pulmonary division of the cardio system?
Right heart, pulmonary arteries and veins and lungs
What is preload?
The amount of stretch on the ventricles prior to contraction. Due both to volume and pressure of blood in ventricles.
Describe one cardiac cycle, beginning with both atria and ventricles relaxed.
The cardiac cycle comprises a complete relaxation and contraction of both the atria and ventricles, and lasts approximately 0.8 seconds. Beginning with all chambers in diastole, blood flows passively from the veins into the atria and past the atrioventricular valves into the ventricles. The atria begin to contract following depolarization of the atria and pump blood into the ventricles. The ventricles begin to contract, raising pressure within the ventricles. When ventricular pressure rises above the pressure in the two major arteries, blood pushes open the two semilunar valves and moves into the pulmonary trunk and aorta in the ventricular ejection phase. Following ventricular repolarization, the ventricles begin to relax, and pressure within the ventricles drops. When the pressure falls below that of the atria, blood moves from the atria into the ventricles, opening the atrioventricular valves and marking one complete heart cycle.
Why is the pressure in the pulmonary circulation lower than in the systemic circulation?
The pulmonary circuit consists of blood flowing to and from the lungs, whereas the systemic circuit carries blood to and from the entire body. The systemic circuit is far more extensive, consisting of far more vessels and offers much greater resistance to the flow of blood, so the heart must generate a higher pressure to overcome this resistance. This can be seen in the thickness of the myocardium in the ventricles.
What is stroke volume?
The volume of blood ejected during 1 ventricular contraction
True or False: Pulmonary and systemic vascular resistance both play a role with influencing cardiac afterload. True False
True
Why do the cardiac muscles cells demonstrate autorhythmicity?
Without a true resting potential, there is a slow influx of sodium ions through slow channels that produces a prepotential that gradually reaches threshold.
What happens to preload when there is venous constriction in the veins? a) It increases. b) It decreases. c) It remains constant. d) There is no way to predict.
a) it increases, because at veins constrict, BP increases
The force the heart must overcome to pump blood is known as ________. a) preload b) afterload c) cardiac output d) stroke volume
b) afterload
Most blood enters the ventricle during ________. a) atrial systole b) atrial diastole c) ventricular systole d) isovolumic contraction
b) atrial diastole, passively fills ventricles 70-80% full
In a healthy young adult, what happens to cardiac output when heart rate increases above 160 bpm? a) It increases. b) It decreases. c) It remains constant. d) There is no way to predict.
b) it decreases, because there isn't enough time for ventricles to fill to maximum, therefore stroke volume decreases, decreases cardiac output
In which septum is it normal to find openings in the adult? a) interatrial septum b) interventricular septum c) atrioventricular septum d) all of the above
c) atrioventricular septum
The first heart sound represents which portion of the cardiac cycle? a) atrial systole b) ventricular systole c) closing of the atrioventricular valves d) closing of the semilunar valves
c) closing of the atrioventricular valves
Which chamber initially receives blood from the systemic circuit? a) left atrium b) left ventricle c) right atrium d) right ventricle
c) right atrium
Which component of the heart conduction system would have the slowest rate of firing? a) atrioventricular node b) atrioventricular bundle c) bundle branches d) Purkinje fibers
d)
What is the average HR for an infant?
120 bpm
What's a fit person's c.o.?
21 L/min
What's an olympian's c.o.?
35 L/min.
What is the average c.o.?
4-6 L/min
What is the average HR for an adult female?
72-80 bpm
What conditions below can result in an increased cardiac afterload? Select all that apply: A. Vasoconstriction B. Aortic stenosis C. Vasodilation D. Dehydration E. Pulmonary Hypertension
A. Vasoconstriction B. Aortic stenosis E. Pulmonary Hypertension Vasoconstriction increases systemic vascular resistance which will increase cardiac afterload. It will increase the pressure the ventricle must pump against to open the semilunar valves to get blood out of the heart. Aortic stenosis creates an outflow of blood obstruction for the ventricle (specifically the left ventricle) and this will increase the pressure the ventricle must pump against to get blood out through the aortic valve. Pulmonary hypertension increases pulmonary vascular resistance which will increase the pressure the right ventricle must overcome to open the pulmonic valve to get blood out of the heart....all of this increase cardiac afterload.
A patient has a blood pressure of 220/140. The physician prescribes a vasodilator. This medication will? A. Decrease the patient's blood pressure and increase cardiac afterload B. Decrease the patient's blood pressure and decrease cardiac afterload C. Decrease the patient's blood pressure and increase cardiac preload D. Increase the patient's blood pressure but decrease cardiac output.
B. Decrease the patient's blood pressure and decrease cardiac afterload
Stroke volume plays an important part in cardiac output. Select all the factors below that influence stroke volume: A. Heart rate B. Preload C. Contractility D. Afterload E. Blood pressure
B. Preload C. Contractility D. Afterload
Which statement below best describes the term cardiac preload? A. The pressure the ventricles stretch at the end of systole. B. The amount the ventricles stretch at the end of diastole. C. The pressure the ventricles must work against to pump blood out of the heart. D. The strength of the myocardial cells to shorten with each beat.
B. The amount the ventricles stretch at the end of diastole.
Which treatments below would decrease cardiac preload? Select all that apply: A. IV fluid bolus B. Norepinephrine C. Nitroglycerin D. Furosemide
C. Nitroglycerin D. Furosemide
Define tachycardia
HR is over 100 bpm
How to calculate c.o.?
HR x SV
Why does increasing EDV increase contractility?
Increasing EDV increases the sarcomeres' lengths within the cardiac muscle cells, allowing more cross bridge formation between the myosin and actin and providing for a more powerful contraction. This relationship is described in the Frank-Starling mechanism.
How does thyroid hormone increase positive chronotropic effects?
It increases the number of beta adrenergic receptors, and it increases cells' sensitivity to epinephrine and norepinephrine
Why is the plateau phase so critical to cardiac muscle function?
It prevents additional impulses from spreading through the heart prematurely, thereby allowing the muscle sufficient time to contract and pump blood effectively.
Why is the plateau phase/are the calcium channels so critical to cardiac muscle function?
It prevents other impulses to spread through the heart, giving the heart time to contract efficiently and effectively
What is included in the systemic division of the cardio system?
Left heart, systemic arteries and veins
What NTs, drugs, hormones produce positive chronotropic effects?
NTs: epinephrine Drugs: nicotine, caffeine, albuterol, pseudoephedrine, phenylephrine Hormones: thyroid hormone, epinephrine, adrenaline
What causes tachycardia?
Strenuous activity, anxiety, stress, sympathomimetics, caffeine, heart disease, increase in body temperature
When taking BP, what sounds represent systole? Diastole?
Systole—faint sound Diastole—sound fades away
Which of the following lists the valves in the order through which the blood flows from the vena cava through the heart? a) tricuspid, pulmonary semilunar, bicuspid, aortic semilunar b) mitral, pulmonary semilunar, bicuspid, aortic semilunar c) aortic semilunar, pulmonary semilunar, tricuspid, bicuspid d) bicuspid, aortic semilunar, tricuspid, pulmonary semilunar
a)
Which chamber initially receives blood from the pulmonary circuit? a) left atrium b) left ventricle c) right atrium d) right ventricle
a) left atrium
The cardiovascular centers are located in which area of the brain? a) medulla oblongata b) pons c) mesencephalon (midbrain) d) cerebrum
a) medulla oblongata
Which valve separates the left atrium from the left ventricle? a) mitral b) tricuspid c) pulmonary d) aortic
a) mitral
Ventricular relaxation immediately follows ________. a) atrial depolarization b) ventricular repolarization c) ventricular depolarization d) atrial repolarization
b) ventricular repolarization
What causes a myocardial infarction?
blockage of coronary artery causes myocardium and/or conduction pathways to injure/die
Which of the following is unique to cardiac muscle cells? a) Only cardiac muscle contains a sarcoplasmic reticulum. b) Only cardiac muscle has gap junctions. c) Only cardiac muscle is capable of autorhythmicity d) Only cardiac muscle has a high concentration of mitochondria.
c)
Which of the following is a positive inotrope? a) Na+ b) K+ c) Ca2+ d) both Na+ and K+
c) Ca2+
What is a chronotropic effect?
change in heart rate
The influx of which ion accounts for the plateau phase of membrane potential of cardiac contractile cells? a) sodium b) potassium c) chloride d) calcium
d) calcium. Recall: Slow calcium channels open, allowing calcium to slowly enter the cell.
Which of the following is not important in preventing backflow of blood? a) chordae tendineae b) papillary muscles c) AV valves d) endocardium
d) endocardium
Which portion of the ECG corresponds to repolarization of the atria? a) P wave b) QRS complex c) T wave d) none of the above: atrial repolarization is masked by ventricular depolarization
d) none of the above
Which component of the heart conduction system would have the slowest rate of firing? a) atrioventricular node b) sinoatrial node c) bundle branches d) ventricular myocytes
d) ventricular myocytes: 20-40 bpm SA node: 70-80 bpm AV node: 40-50 bpm
What are the 2 sounds heard in the heart? What do they indicate?
lubb-dubb: S1: lubb=ventricles contracting, av valves closing S2: dubb=ventricles relaxing, semilunar valves closing
Define systole
period of contraction of the heart
Define diastole
period of relaxation of the heart
What three factors govern stroke volume?
preload, contractility, afterload
What is cardiac reserve?
the difference between resting and maximal CO
Define cardiac output
the volume of blood ejected by the ventricles in 1 minute
Define stroke volume
the volume of blood the heart ejects with each beat
