Chapter 20
What is the average mass of a heart in females?
250 g
What is the average mass of a heart in males?
300 g
The heart generally decreases in size after approximately age _____
65
Explain how the nervous system detects in response to each of the following A. A decrease in blood pressure B. An increase in blood carbon dioxide level C. A decrease in blood pH D. A decrease in blood oxygen level
A. B. C. D.
Differentiate between end-diastolic volume and end-systolic volume
EDV - volume of blood in ventricles during ventricular diastole ESV - volume of blood remaining in the ventricles at the end of ventricular systole
What effect does an increase or a decrease in extracellular potassium, calcium, and sodium ions have on the heart's rate and force of contraction
Excess K+ — causes the heart rate and stroke volume to decrease
How is the prolonged refractory period generated in cardiac muscle and what is the advantage?
It is generated when the plateau phase of the action potential in cardiac muscle delays repolarization to the resting membrane potential It ensures that contraction and most relaxation are completed thus preventing titanic contractions in cardiac muscles and is responsible for arrhythmia contractions.
The heart is located in the _________
mediastinum
Explain the relationship among mean arterial pressure, cardiac output, and peripheral resistance and define them.
MAP = CO x PR Mean arterial pressure(MAP) - Slightly less than the average of the systolic and diastolic pressure in the aorta Cardiac output(CO) - amount of blood pumped by the heart per minute Peripheral resistance(PR) - total resistance against which blood must be pumped
Describe the baroreceptor reflex and the heart's response to an increase in venous return
Measure blood pressure by detecting the degree of stretch of blood vessel walls Venous return ???
What happens when blood flows through tissues in the heart?
O2 is released from the blood and moves into the tissues. In resting person blood flowing through the coronary arteries gives up approximately 70% of its O2(near maximum) so it cannot increase substantially during exercise.
What neurotransmitters are released by parasympathetic and sympathetic post ganglionic neurons of the heart? What effects do they have on membrane permeability and excitability?
Parasympathetic - Acetylcholine, binds to ligand-gated channels that cause plasma membranes of cardiac muscle cells to become more permeable to K+ Sympathetic - Norepinephrine, increase his heart rate and increases the force of contraction
What effects do parasympathetic stimulation and sympathetic stimulation have on heart rate, force of contraction, and stroke volume?
Parasympathetic - alters(reduces) heart rate, can increase if venous returns is constant Sympathetic - increase his heart rate and force of contraction
Why does cardiac muscle have slow onset of contraction and prolonged contraction?
Preferential pathways conduct action potentials from the essay no to the AV node and a greater velocity than they are transmitted in the remainder of the atrial muscle cells. The slow rate of action potential conduction in the AV node is due to the smaller-diameter muscle cells and if you were gap junctions in their intercalated disks -> fewer myofibrils than most cardiac muscle cells
Name the two main hormones that affect the heart. Where are they produced, what causes the release, and what effects do they have on the heart?
Released from the adrenal medulla and it occurs in response to increased physical activity, emotional excitement, or other stressful situations. They can markedly influence the hearts pumping effectiveness thus increasing the rate and force of heart contractions *** epinephrine takes a longer time to act on the heart but lasts longer
Define isovolumetric and when does most ventricular filling occur?
Same volume Most occur when all chambers are relaxed and blood is flowing from the veins into the atria and possibly into the ventricles
What side does the systemic circulation pump blood through and what does it do?
The left side; delivers O2 a nutrients to the remaining tissues of the body. From those tissues CO2 to another waste products are carried back to the right side of the heart.
Define afterload and describe its affects on the pumping effectiveness of the heart
The pressure in the aorta that must be overcome to open the semi lunar valve and eject blood. Aortic blood pressure must increase to more than 170 mm Hg The heart pumping effectiveness is very insensitive to large changes in afterload unless it reaches above 170 mm Hg
What side does the pulmonary circulation pump blood through and what does it do?
The right side; carries blood to the lungs where CO2 diffuses from the blood and into the lungs and O2 diffuses from the lungs into the blood
T/F: blood flow through the coronary blood circulation is not continuous
True; when the cardiac muscles contract blood vessels in the wall of the heart are compressed so blood does not readily flow through them. When the cardiac muscle relaxers the blood vessels are not compressed and blood flow through the coronary blood vessels resumes
Define systole and diastole
systole - contraction diastole - relaxation
How do you calculate cardiac output(CO)?
CO = heart rate(HR) x stroke volume(SV=EDV-ESV) CO = HR x (EDV-ESV) Example: 72 bpm x (125 mL - 55 mL)= 5040 mL/min
What is cardiac reserve and how can exercise influence it?
The difference between cardiac output when a person is at rest and maximum Exercise can greatly increase cardiac reserve by increasing cardiac output. Lack of exercise can reduce cardiac reserve and affect a persons quality of life.
Why is cardiac muscle referred to as autorhythmic and what are ectopic foci?
Because it stimulates itself to contract at regular intervals Ectopic Foci - any part of the heart other than the SA node that generates a heartbeat ***caused by malfunction of SA node or blockage of conducting pathways between the SA node and other parts of the heart
What produces the first and the second hard sounds?
1st - caused by vibration of the atrioventricular valves and surrounding fluid as the valves close(beginning of ventricular systole) 2nd - results from closure of the aortic and pulmonary semilunar valve(beginning of ventricular diastole) ***diastole lasts longer
Describe the structure of the pericardium
(1.) Fibrous Pericardium (2.) Serous Pericardium (a.) Parietal Pericardium (b.) Parietal Cavity (c.) Visceral Pericardium (Epicardium)
Explain why Purkinje fibers conduct action potentials more rapidly than other cardiac muscle cells
- large-diameter cardiac muscle fibers - fewer myofibrils and do not contractors forcefully - well developed intercalated disks and numerous gap junctions
List the five periods of the cardiac cycle and state whether the AV and semilunar valves are open or closed and the phase of the ECG for each.
1. Active ventricular filling(atrial systole) - AV open/SL closed - P wave 2. Period of isovolumetric contraction(AP from AV node to Purkinje fibers/ventricular systole) - Both are closed - QRS Complex 3. Period of ejection(ventricular systole/atrial diastole) - AV closed/SL open - Maybe T Wave 4. Period of isovolumetric relaxation(Ventricular repolarization) - Both are closed - T wave 5. Passive ventricular filling (Atrial/Ventricular Diastole) - AV open/SL closed - Maybe P Wave
Describe ion movement during the depolarization, early repolarization, plateau, and final repolarization phases
1. Depolarization: caused by Na* channels opening 2. Early Depolarization: caused by some K+ channels being open 3. Plateau: caused by Ca^2+ channels still open which slows repolarization ***K+ and Ca^2+ channels are balanced ***1 Ca going in 2 K going out 4. Final Repolarization: caused by Ca^2+ channels closing and more K+ channels opening
List the layers of the heart wall and describe the structure and function of each
1. Epicardium(Visceral Epicardium) - Sin service membrane that constitutes the smooth outer surface of the heart 2. Myocardium - thick middle layer composed of cardiac muscle cells and is responsible for the hearts ability to contract 3. Endocardium - consists of simple squamous epithelium over layer of connective tissue. Forms of smooth inner surface of the heart chambers which allows blood to move easily through the heart without friction also lions live pathetic vessels as well as covers the surfaces of the heart valves
List the major functions of the heart
1. Generating blood pressure 2. Routing blood 3. Ensuring one way blood flow 4. Regulating blood supply
Describe the location and blood flow through the coronary arteries
1. Left & Right Coronary Arteries - exit the aorta 2. anterior interventricular artery - first branch of the left coronary artery and supplies blood to most of the anterior part of the heart 3. Left marginal artery - Second major branch of the left coronary artery and supplies blood to the lateral wall of the left ventricle 4. Circumflex artery - third major branch of the left coronary artery and supplies blood to much of the posterior wall of the heart 5. Right marginal artery - larger branch of the right coronary artery and supplies blood to the lateral wall of the right ventricle 6. Posterior interventricular artery - Second branch of the right coronary artery and supplies blood to the posterior and inferior part of the heart 7. Anastomosis - Direct connections between arteries that may form either between branches of a given artery or between branches of different arteries.
Why is it important for health professionals to know the location of the heart and the thoracic cavity?
1. Positioning a stethoscope to hear the heart sounds 2. Positioning electrodes to record an electrocardiogram 3. Effective CPR
Review the structure and functions of the chambers of the heart
1. Right Atrium - receives blood from the body through the superior vena cava and the inferior vena cava. As well as receives blood from the heart through the opening of the coronary sinus. 2. Left Atrium - receives blood from the lungs through the pulmonary veins. 3. Right Ventricle - allows blood to flow into pulmonary trunk 4. Left Ventricle - Allows blood to flow into aorta **The thicker wall of the left ventricle allows for stronger contractions to pump blood through the systemic circulation. ———(Milne: " pumps blood through longer blood vessels and narrower capillaries)
Relate the large veins and arteries that enter and exit the heart
1. Superior Vena Cava - carries blood from upper body to the right atrium 2. Inferior Vena Cava - carries blood from the lower body to the right atrium 3. Pulmonary Veins - carry blood from the lungs to the left atrium 4. Pulmonary trunk - carries blood from the right ventricle to the lungs 5. Aorta - carries blood from the left ventricle to the body 6 Pulmonary Arteries - carry blood from the pulmonary trunk to the lungs
Name the valves of the heart and state their locations and functions
Atrioventricular Valves - ensure blood flows from the atria into the ventricle preventing blood from flowing back into the atria Semilunar Valves - when blood flows back from the aorta or pulmonary trunk toward the ventricles and enters the pockets of the cusp causing the cusps to snap shut
Compare and contrast cardiac muscle and skeletal muscle
Cardiac Muscle - much smaller muscle cells - usually branched - usually one nucleus (some w/ 2) - more mitochondria because they can't run on oxygen that they have to generate ATP and get enough oxygen for muscle contractions - cardiac cells are attached by intercalated discs with desmosomes and gap junctions - some calcium from the extracellular fluid and from t-tubules - less extensive Sarcoplasmic reticulum and broader T-tubules -intrinsic capacity to spontaneously generate action potentials for contraction Skeletal Muscle - long muscle cells - very huge and thick muscle cells - low number of Sarcoplasmic reticulum and T tubules - adequate calcium for contraction is stored in the sarcoplasmic reticulum - sarcomeres end-to-end to form myofibrils and mitochondria provide ATP for contraction
Relate why the SA node is the pacemaker of the heart
Cardiac muscle cells have the intrinsic capacity to spontaneously generate action potentials and add a greater frequency
What is the heart skeleton composed of and what are its functions?
Consists of fibrous connective tissue rings which surround the heart valves and separate the atria from the ventricles. Muscle fibers our range so that the contractions of the ventricles produces a ringing motion and the distance between the Apex and the base of the heart shortens
How does the depolarization of pacemaker cells differ from the depolarization of other cardiac cells and what is the pacemaker potential?
Depolarization of pacemaker cells is dependent on Na+, K+ and Ca^2+ Pacemaker Potential is a spontaneous developing local potential -if it reaches threshold, then action potentials are generated in the SA node
What was the name for fossa ovalis and what was its purpose?
Foramen Ovale; opening between the right and left atria in the embryonic and fetal heart Allows blood to flow from the right to the left atrium and bypass the pulmonary circulation
What is another function not listed?
If blood pressure is too high the cardiac muscle cells and the right atrium will go and release a chemical that will end up causing your blood pressure to drop
What does ECG measure? Name of the waves and intervals and state what events occur during each one
Summation of all action potentials at a given time. P wave - atrial depolarization QRS Complex - ventricular depolarization T wave - ventricular repolarization PR (aka PQ, Q is very small) interval - atrial contracts, begins to relax and ventricle behind to depolarize near the end; 0.16 sec QT Interval - Approx. length time of ventricular contraction and relaxation; 0.36 sec
Starting at the vena cava and ending at the aorta trace the flow of blood through the heart
Superior/Inferior Vena Cava ➡️ Right Atrium ➡️ Tricuspid Valve ➡️ Right Ventricle ➡️ Pulmonary semilunar valve ➡️ Pulmonary trunk ➡️ Pulmonary arteries ➡️ lung tissue (Pulmonary circulation) ➡️ pulmonary veins ➡️ Left Atrium ➡️ Mitral Valve ➡️ Left Ventricle ➡️ Aortic Semilunar Valve ➡️ Aorta ➡️ EITHER Body tissues (Systemic Circulation) ➡️ Vena Cava OR Heart Tissue (Coronary Circulation) ➡️ Coronary Sinus & Cardiac Veins ➡️ Right Atrium
What part of the brain regulates the heart and describe the automatic nerve supply to the heart.
Sympathetic - increased Cardiac Output Parasympathetic - decreased Cardiac Output (smaller effect on CO) May influence the pumping action of the heart by affecting both heart rate(HR) and stroke volume(SV)
Explain the production of the following in the aorta: systolic pressure, diastolic pressure, and the dicrotic notch(incisura)
Systolic pressure - 120 mm Hg Diastolic pressure - 80 mm Hg Dicrotic notch - sudden change in aortic pressure
Identify the parts of the conducting system of the heart and explain how it coordinates contraction of the atria and ventricles
The system consists of modified cardiac muscle cells that form two nodes and a conducting bundle 1. Sinoatrial(SA) Node (aka The Pacemaker) - Originate action potentials and travel across the wall of the atrium 2. Atrioventricular(AV) Node - Receive AP, slows down b/c of the smaller-diameter muscle cells and fewer gap junctions in their intercalated disks 3. Atrioventricular (AV) bundle - AP velocity increases dramatically and pass through left and right bundle branches 4. Purkinje fibers - AP pass through each individual PF that penetrate the myocardium of the ventricles Interventricular Septum is stimulated ➡️ ventricles contract at apex ➡️ contract progressively towards base ***The spiral arrangement results in a ringing action that decreases the distance between the Apex and base enforces blood upwards tour of the great vessels***
Describe the location and blood flow through the cardiac veins
Veins carry the blood from the heart walls to the right atrium 1. Great cardiac vein - drains blood from the left side of the heart 2. Small cardiac vein - drains the right margin of the heart Veins me toward the posterior part of the coronary sulcus and empty into the coronary sinus which in turn empties into the right atrium
What is venous return? Explain how it affects preload. How does preload affects cardiac output? State the Sterling law of heart.
Venous return - the amount of blood returning to the heart from the systematic circulation As venous return increases, end-diastolic volume(EDV) increases Sterling law of heart - with increased preload, there is a greater contraction force and greater stroke volume (SV)
What is stroke volume and what are two ways to increase it?
Volume of blood pumped during each heartbeat Increased force of contraction that either decreases end systolic volume or ejects increased and systolic volume
Explain calcium induced calcium release (CICR)
What an action potential occurs in the cardiac muscle cell Ca^2+ enters the cell and binds to receptors in the membranes of the sarcoplasmic reticulum(SR) resulting in the opening of calcium channels on the membrane of the SR
What are the functions of the Papillary muscles and Chordae Tendineae?
[P.M] cone shaped muscular pillars that are attached to the costs of the atrioventricular valves by thin strong connective tissue strings. ventricles contract ➡️ papillary muscles contract ➡️ pulling on chordae tendineae ➡️ closing the valve cusps