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The Cardiovascular System Overview
Students will understand the division of the CV system into the pulmonary circulation and the systemic circulation and the unique needs of these two circulatory systems.
Students should be able to describe the path of the blood through the heart.
Students will understand the similarities and differences between cardiac muscle and skeletal muscle and how these differences relate to differences in the function of these two muscle types.
Students will be able to explain the differences between a contractile muscle cell and a pacemaker cell action potential.
Students will understand the control of cardiac output by control of Heart rate and Stroke Volume, and understand how these two variables are controlled.
Students will be able to define the waves of an electrocardiogram and related them to the electrical and mechanical changes in the heart.
Key Terms & Concepts
Cardiovascular system: a circulatory system comprising a heart, blood vessels, and blood.
Capillaries: the microscopic vessels where blood exchange material with the interstitial fluid Arteries: Blood vessels carry blood away from the heart
Veins: Blood vessels that return blood to the heart
Septum: the heart id divided by a central wall; into right and left halves
Atria: receives blood returning to the heart from the blood vessels
Ventricles: pumps blood out into the blood vessels
***The right side of the heart receives blood from the tissues and sends it to the lungs for oxygenation. The left side of the heart receives newly oxygenated blood from the lungs and pumps it to tissues throughout the body.
Pulmonary circulation: the blood vessels that go from the right ventricle to the lungs and back to the left atrium are known collectively as the pulmonary circulation.
Aorta: is the main artery in the human body, originating from the left ventricle of the heart and extending down to the abdomen, where it splits into two smaller arteries (the common iliac arteries). The aorta distributes oxygenated blood to all parts of the body through the systemic circulation.
Systemic circulation: the blood vessels that carry blood from the left side of the heart to the tissues and back to the right side of the heart are collectively known as the systemic circulation.
Vena cava (superior and inferior): the veins from the upper part of the body join to form the superior vena cava. Those from the lower part of the body form the inferior vena cava. The two vena cavae empty into the right atrium.
Resistance: the tendency of the cardiovascular system to oppose blood flow
Vasoconstriction: a decrease in blood vessel diameter
Vasodilation: an increase in blood vessel diameter
Pericardium: the heart is encased in a tough membranous sac
Myocardium: the heart itself is mostly composed of cardiac muscle
Atrioventricular valves: between the atria and ventricles
Semilunar valves: between the ventricles and the arteries
Pacemaker potential: In the pacemaking cells of the heart (e.g., the sinoatrial node), the pacemaker potential (also called the pacemaker current) is the slow, positive increase in voltage across the cell's membrane (the membrane potential) that occurs between the end of one action potential and the beginning of the next action potential
If channels: When the cell membrane potential is -60mV, If channels that are permeable to both K+ and Na+ open. These channels are called If channels because they allow current (I) to flow and because of their unusual properties.
Sinoatrial node: the depolarization begins in the sinoatrial node (SA node), autorhythmic cells in the right atrium that serve as the main pacemaker of the heart.
Atrioventricular node (AV node): a group of autorhythmic cells near the floor of the right atrium.
Purkinje fibers: specialized conducting cells of the ventricles, transmit electrical signals very rapidly down the atrioventricular bundle, or AV valve, also called the bundle of His, in the ventricular septum.
Electrocardiogram: show the summed electrical activity generated by all cells of the heart.
P wave: corresponds to depolarization of the atria
QRS complex: represents the progressive wave of ventricular depolarization.
T wave: represents the repolarization of the ventricles.
***Atrial repolarization is not represented by a specific wave but is incorporated into the QRS complex.
Systole: the timing during which the muscle contracts
Diastole: the timing during which cardiac muscle relaxes
Stroke volume: the amount of blood pumped by one ventricle during a contraction
Cardiac Output: the volume of blood pumped by one ventricle in a given period of time. Because all blood that leaves the heart flows through the tissues, cardiac output is an indicator of total blood flow through the body.
Heart rate: the number of heartbeats occurring within a specific length of time
Frank-Starling Law of the Heart: stroke volume is proportional to EDV. As additional blood enters the heart, the heart contracts more forcefully and ejects more blood. It means that within physical limits, the heart pumps blood that return to it.
Venous return: Venous return is the rate of blood flow back to the heart. It normally limits cardiac output. Superposition of the cardiac function curve and venous return curve is used in one hemodynamic model. Venous return (VR) is the flow of blood back to the heart
End-diastolic volume: is the volume of blood in the right and/or left ventricle at end load or filling in (diastole) or the amount of blood in the ventricles just before systole.
End-systolic volume: is the volume of blood in a ventricle at the end of contraction, or systole, and the beginning of filling, or diastole. ESV is the lowest volume of blood in the ventricle at any point in the cardiac cycle.
Silverthorn: Chapter 14 pp. 436-476
Outline the path the blood takes through the heart from its arrival into the right atrium until its ejection from the left ventricle, including the action of the heart valves.
List 3 similarities and 3 differences between contractile cardiac and skeletal muscle and one similarity and one difference with smooth muscle and relate these differences to differences in the function of these two muscle types.
Using the numbered steps, compare the events shown in EC Coupling in skeletal muscle and smooth muscle:
Smooth and cardiac muscle are the same except where indicated. (1) Multi-unit smooth muscle and skeletal muscle require neurotransmitters to initiate the action potential. (2) No significant Ca2+ entry in skeletal muscle. (3) No CICR in skeletal muscle. (4) Ca2+ leaves the SR in all types. (5) Calcium signal is all types. (6)-(7) Smooth muscle lacks troponin. Skeletal muscle is similar too cardiac. (8) Same in all types. (9) NCX lacking in skeletal muscle. (10) Same in all types.
Outline the path of excitation coupling in cardiac muscles.
Identify the different steps involved in the action potential of a cardiac contractile cell.
What is the lowest voltage of the unstable membrane potential for a myocardial autorhythmic cells and how does this relate to the depolarization process? What controls the speed of pacemaker depolarization?
Autorhythmic cells have unstable membrane potentials called pacemaker potentials.
A: The pacemaker potential gradually becomes less negative until it reaches threshold, triggering an action potential.
B: Ion movements during an Action and Pacemaker Potential
C: State of Various Ion channels
Speeds up the depolarization rate of the pacemaker potential: Increase in Ca+ influx and Increase in Na+ influx
Trace the steps of the electrical signal for cardiac contraction beginning at the SA node. Why does the contraction push blood up from the bottom of the ventricle?
Briefly map the events of an electrocardiogram (P wave, QRS complex and T wave) onto their corresponding electrical events.
Define systolic versus diastolic blood pressure.
The top number is the maximum pressure your heart exerts while beating (systolic pressure), and the bottom number is the amount of pressure in your arteries between beats (diastolic pressure). The numeric difference between your systolic and diastolic blood pressure is called your pulse pressure.
Define stroke volume and cardiac output.
Stroke Volume: is the amount of blood ejected by the left ventricle in one contraction. Although stroke volume can refer to either left or right side of the heart, it is most associated with the left side. It is measured in ml/beat and generally has a normal value of about 1 cc/kg
Cardiac Output: The amount of blood the heart pumps through the circulatory system in a minute. The amount of blood put out by the left ventricle of the heart in one contraction is called the stroke volume. The stroke volume and the heart rate determine the cardiac output.
How does the Autonomic Nervous System Impact Heart Rate?
The sympathetic and parasympathetic branches of the autonomic division influence heart rate through antagonistic control. Parasympathetic activity slows heart rate, while sympathetic activity speeds it up.
What is the role of venous return in regulating stroke volume? What are 3 factors that influence venous return?
Venous return: the amount of blood that enters the heart from the venous circulation.
The Three factors that affect Venous Return:
Contraction or compression of veins returning blood to the heart (the skeletal muscle pump)
Pressure changes in the abdomen and thorax during breathing (the respiratory pump)
Sympathetic innervation of veins.
*** According to the Frank Starling law, stroke volume increases as end-diastolic volume increases.
Fall 2016ion, or systole, and the beginning of filling, or diastole. ESV is the lowest volume of blood in the ventricle at any point in the cardiac cycle.
The top number is the maximum pressure your heart exerts while beating (systolic pressure), and the bottom number is the a