Chapter 11 Cardiovascular System
Explain intrinsic regulation of the heart
Intrinsic regulation refers to mechanisms contained within the heart itself. The force of contraction produced by cardiac muscle is related to the degree of stretch of cardiac muscles fibers. The amount of blood in the ventricles at the end of ventricular diastole determines the degree to which cardiac muscle fibers are stretched.
Predict what will happen (i.e where will blood back up) if the opening of either of the AV valves (tricuspid or bicuspid/mitral) or either of the semilunar valves was narrowed or stenotic
It would end up in the left ventricle- valve is right after left ventricle thus all blood would be stuck in left ventricle
List the 4 chambers of the heart
Left and right atrium Left and right ventricles
Systemic circulation
Left side; pumps blood to the rest of the body
What causes the hear sounds? -lubb and dubb What is a heart murmur?
Lubb- shutting of the AV valves Dubb- shutting of the semilunar valves Heart murmur: blood can leak or regurgitate from the ventricles back to the atria
Predict what will happen to the amount of blood ejected from the heart with a mitral valve prolapse and regurgitation
Mitral valve prolapse- the valve "flops back" into the atria (doesn't close properly during contraction of the left ventricle) Mitral regurgitation- blood goes from the ventricle into the atrium Effect: Less blood will be ejected through the heart
Which layer of the heart wall contains cardiac myocytes?
Myocardium
What does the P wave, QRS complex, and T wave of an ECG represent?
P wave: atrial depolarization QRS complex: ventricular depolarization T wave: ventricular repolarization
What type of blood is in the right and left sides of the heart?
Right side: Unoxygenated Left side: Oxygenated
Pumlonary circulation
Right side; pumps blood to the lungs
What is the role of the SA and AV nodes in the heart?
SA node: (heart's pacemaker) action potential starts in SA node allowing ATRIA to depolarize and contract AV node: delay while the action potential travels through the AV node allowing VENTRICLES to depolarize and contract
How does increasing pressure in the ventricles (i.e with ventricular contraction) affect the AV and semilunar valves?
Semilunar valves open when pressure in the left ventricle exceeds pressure in the aorta AV valves open when pressure in the left atrium exceeds pressure in the left ventricle
What causes a myocardial infarction or heart attack?
A clot in the coronary artery- blood supply to tissue downstream is shut off
Define cardiac tamponade and explain the effect is has on the pumping function of the heart
A potentially fatal condition in which fluid or blood accumulates in the pericardial cavity and compresses the heart from the outside. When compressed by fluid within the pericardial cavity, it cannot expand when the cardiac muscle relaxes. The heart cannot fill with blood during relaxation, which makes pumping impossible. Fluid must be removed.
Why do the AV valves open during ventricular relaxation, whereas the semilunar valves open during ventricular contraction?
AV valves open during relaxation so blood can flow into the ventricles while semilunar valves open during contraction due to increased pressure and eject blood into the pulmonary trunk and aorta AV: pressure in the left atrium exceeds pressure in the left ventricle Semilunar: pressure in the left ventricle exceeds pressure in the aorta
Define cardiac output, stroke volume and heart rate. Know the formula for cardiac output
CO- volume of blood ejected from the heart (left ventricle) per minute SV- volume of blood pumped per ventricle each time the heart contracts HR- number of times the heart beats per minute Formula: CO= SV + HR
Compare the action potential in skeletal muscle and cardiac muscle. a. What are the phases of each? b. What is responsible for each phase? c. What causes the action potential for cardiac muscle to be so long compared to skeletal muscle? Why is this important?
Action potentials last much longer in cardiac muscle than in skeletal muscle. a. Skeletal muscle has the depolarization phase and repolarization phase. Cardiac muscle has the depolarization, early repolarization, plateau, and final repolarization phases. b. S: Na+ influx causes depolarization, K+ influx causes repolarization C: Na influx causes depolarization, Ca influx causes the plateau phase, and K efflux causes the repolarization phase. c.The plateau phase makes the action potential and its refractory period last longer. The prolonged action potential and refractory period allow cardiac muscle to contract and relax completely before another action potential can be produced. The long refractory period in cardiac muscle prevents tetanic contractions from occurring, ensuring a rhythm of contraction and relaxation for cardiac muscle.
Follow the conduction pathway for action potentials starting in the SA node and ending in the ventricles. Correlate this with atrial and ventricular contraction.
Action potentials originate in the SA node and travel across the wall of the atrium from the SA node to the AV node. Action potentials pass through the AV node and along the AV bundle, which extends from the AV node, through the fibrous skeleton, into the interventricular septum. The AV bundle divides into right and left bundle brahces, and action potentials descend to the apex of each ventricle along the bundle branches. Action potentials are then carried by the Purkinje fibers from the bundle branches to the ventricular walls. Action potential starts in the SA node Atria depolarize and contract Delay while the action potential travels thru the AV node Ventricles depolarize and contract (repeats)
How does an increase or decrease in venous return affect preload?
As venous return increases, preload increases.
What is the sequence of contraction and relaxation of the atria and ventricles (i.e do they contract at the same time? if not, which contracts first? when do they relax?)
Atria contract first then the ventricles As the atria contract, the ventricles relax As the ventricles contract, the atria relax
Describe how an ECG appears with atrial fibrillation, ventricular fibrillation, and AV block
Atrial fibrillation ECG will have no P waves, normal QRS and T waves, irregular timing AV block will have an ECG where there is not a QRS with every P wave. Ventricular fibrillation there will not be a nice discrete QRS complex.
Define atrial systole and diastole? Define ventricular systole and diastole?
Atrial systole= contraction of 2 atria Atrial diastole= relaxation of 2 atria Ventricular systole= contraction of 2 ventricles Ventricular diastole= relaxation of 2 ventricles
Explain why it is important for cardiac output to increase with exercise
Because more blood needs to be delivered to the tissues.
Follow the path of blood from the superior and inferior vena cava to heart, to lungs,back to the heart, to the aorta. List the chambers, blood vessels and valves that the blood passes through.
Blood enters the right atrium from the superior and inferior vena cava. From the right atrium, it goes through the tricuspid valve to the right ventricle. From the right ventricle, it goes through the pulmonary semilunar valves to the pulmonary trunk. From the pulmonary trunk it moves into the right and left pulmonary arteries to the lungs. From the lungs, oxygenated blood is returned to the heart through the pulmonary veins. From the pulmonary veins, blood flows into the left atrium. From the left atrium, blood flows though the bicuspid or mitral valve into the left ventricle. From the left ventricle, it goes through the aortic semilunar valves into the ascending aorta. Blood is distributed to the rest of the body from the aorta.
Where are intercalated disks and what is their function?
Cardiac muscle cells are bound end-to-end and laterally to adjacent cells by specialized cell-to-cell contacts called intercalated disks. The membranes of the intercalated disks are highly folded and the adjacent cells fit together, greatly increasing contact between them and preventing cells from pulling apart. Gap junctions in intercalated disks allow cytoplasm to flow freely between cells, enabling action potentials to pass easily from one cell to the next. Function: important for the heart to contract as one unit
How does contraction of the atria or ventricles change the pressure within that chamber?
Contraction causes pressure to INCREASE
What supplies blood (oxygen and nutrients) to most of the heart wall?
Coronary arteries- majority of the heart has to get blood supply from coronary arteries
Explain how emotion can increase cardiac output?
Excitement, anxiety, or anger can affect the cardioregulatory center, resulting in increased sympathetic stimulation of the heart and increased cardiac output. Depression, on the other hand, can increase parasympathetic stimulation of the heart, causing a slight reduction in cardiac output.
4 functions of the heart
Generating blood pressure Routing blood Ensuring one-way blood flow Regulating blood supply
What is an electrocardiogram?
Graphical record of the electrical activity of the heart
What are the chordae tendineae? Is their proper functioning important during ventricular systole and diastole? What would happen if they were damaged and malfunctioned?
Help prevent the AV valves from 'flopping' back or prolapsing into the atria. Function during ventricular systole If the valves didn't close properly, blood can leak or regurgitate from the ventricles back into the atria.
What is the main function of pericardial fluid?
Helps reduce friction as the heart moves within the pericardium
Does blood flow from an area of higher pressure to lower pressure or vice versa?
Higher pressure to lower pressure
How does an increase or decrease in preload affect stroke volume and cardiac output? How is this represented by Starling's law of the heart?
If venous return increases, the heart fills to a greater volume and stretches the cardiac muscle fibers, producing an increased preload. In response, cardiac muscle fibers contract with a greater force. The greater force of contraction causes an increased volume of blood to be ejected from the heart, resulting in an increased stroke volume. As venous return increases, resulting in an increased preload, cardiac output increases. Conversely, if venous return decreases, resulting in a decreased preload, the cardiac output decreases. The relationship between preload and stroke volume is called Starling's law of the heart. For example, muscular activity during exercise causes increased venous return, resulting in increased preload, stroke volume and cardiac output.
What effect will stenotic (i.e thickening and immobility of either the mitral valve or aortic semilunar valve so they don't open properly) have on pressure and volume changes in the left atria and left ventricle?
Increased pressure in the left atrium during atrial diastole
An increase in which intracellular ion is responsible for causing action and myosin interactions and contraction of cardiac myocytes?
Intracellular calcium levels
Predict the effect of blocking either some of the sodium, calcium, or potassium channels on the action potential of a cardiac myocyte. Which phase of the action potential would be affected and how would it change?
Sodium: initial, rapid depolarization phase of the action potentials results from the opening of voltage gated Na+ channels, which increase permeability of the cell membrane to Na+. Sodium ions then diffuse into the cell, causing depolarization. This depolarization stimulates the opening of voltage gated Ca2+ channels, and Ca2+ begins to diffuse into the cell contributing to the overall depolarization. At the peak of depolarization, the Na_ channels close, and a small number of K+ channels open. However, the Ca2+ channels remain open. Thus, the exit of K+ from the cell is counteracted by the continued movement of Ca2+ into the cell. Consequently, the plateau phase is primarily the result of the opening of voltage-regulated Ca2+ channels. The slow diffusion of Ca2+ into the cell is the reason the cardiac muscle fiber action potential lasts longer than action potentials in skeletal muscle fibers. The plateau phase ends, and the repolarization phase begins as Ca2+ channels close and many K+ channels open, allowing K+ to move out of the cell. If blocked it would shorten the plateau phase of the action potential and cause a weaker contraction. An increase in intracellular Ca during depolarization causes contraction. A decrease in intracellular Ca during repolarization causes relaxation.
What affect does sympathetic and parasympathetic stimulation have on the SA node ( heart rate) and atrial and ventricular myocytes ( force of contraction)? What neurotransmitter and receptor is involved with each? How would each affect cardiac output?
Sympathetic: Affects SA node by increasing heart rate/SV. Affects myocytes in the atria and ventricles by increasing force of contraction. Neurotransmitter: Norepinephrine and epinephrine activate Beta adrenergic receptors Increase cardiac output Parasympathetic: Affects the SA node by decreasing heart rate. No innervation of the ventricles and no effect on ventricular contractility. Neurotransmitter: Acetylcholine activates muscarinic receptors Decrease cardiac output
How does and increase or decrease in afterload affect stroke volume and cardiac output?
The afterload influences cardiac output less than preload influences it. Decrease in afterload: decrease the workload in the heart. Decrease stroke volume and cardiac output Increase in afterload: increase the workload in the heart. Increase stroke volume and cardiac output Hypertension= chronic increase in afterload
Explain the baroreceptor reflex. What happens to sympathetic activity and parasympathetic activity on the heart if blood pressure either decreases or increases? How would this reflex response affect cardiac output and blood pressure?
The baroreceptor reflex is a mechanism of the nervous system that plays an important role in regulating heart function. Baroreceptors are stretch receptors that monitor blood pressure in the aorta and in the wall of the internal carotid arteries, which carry blood to the brain. Changes in blood pressure result in changes in the stretch of the walls of these blood vessels—and changes in the frequency of action potentials produced by the baroreceptors. The action potentials are transmitted along nerve fibers from the stretch receptors to the medulla oblongata of the brain. The cardioregulatory center controls the action potential frequency in sympathetic and parasympathetic nerve fibers that extend from the brain and spinal cord to the heart. When blood pressure increases, the baroreceptors are stimulated. AP are sent along the nerve fibers to the medulla oblongata at increased frequency. This prompts the cardioregulatory center to increase parasympathetic stimulation and decrease sympathetic stimulation of the heart. The heart rate and stroke volume decrease, causing BP to decline. When blood pressure decreases, less stimulation of the baroreceptors occurs. A lower frequency of action potentials is sent to the medulla oblongata of the brain, and this triggers a response in the cardioregulatory center by increasing sympathetic stimulation of the heart and decreasing parasympathetic simulation. The heart rate and stroke volume increase, causing BP to increase.
Describe the cardiac cycle and the relationship among the contraction of each of the chamber, the pressure in each of the chambers, and the phases of the ECG, and the heart sounds
The cardiac cycle is all the events associated with the flow of blood through the heart during one complete heartbeat. 1. atrial systole-atria contract, AV valves open, semilunar valves closed 2. Start ventricular systole- AV valves slam shut, semilunar valves closed, ventricles contract- Isovolumetric ventricular contraction 3. Pressure changes produced within the heart chambers as a result of cardiac muscle contraction move blood from areas of higher pressure to areas of lower pressure. When ventricles relax, atria contract and vise versa Shutting of AV valves: 'lubb' Shutting of semilunar valves: 'dubb'
What is the pericardial sac and pericardial cavity?
The heart lies in the pericardial cavity. The pericardial cavity is formed by the pericardium (pericardial sac), tissues that surround the heart and anchor it within the mediastinum. The pericardium consists of 2 layers, The tough fibrous CT outer layer is called the fibrous pericardium, and the inner layer of flat epithelial cells, with a thin layer of CT is called the serous pericardium.
Explain how and why an increase in blood CO2 levels (or decrease in blood pH) can increase cardiac output.
The more blood needed, the more the heart must contract and pump blood
Define venous return, preload, and afterload
Venous return is the amount of blood that returns to the heart. Preload is the degree to which the ventricular wall is stretched at the end of diastole. Afterload refers to the pressure against which the ventricles must pump blood.