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39 Cards in this Set

  • Front
  • Back
Cardiac Cycle
complete heartbeat consisting of diastole and systole of both atria and both ventricles
Cardiac Output
volume of blood pumped by one ventricle per minute
Chemoreceptor Reflex
functions as an emergency mechanism when hypoxia or hypercapnia endangers the stability of the internal environment
Diastole
relaxation of the heart (especially the ventricles), during which it fills with blood; opposite of systole
Electrocardiogram
graphic record of the heart's action potentials
Minute Volume
volume of blood circulating through the body per minute
Pacemaker
The sinoatrial node (SA node, or pacemaker) consists of hundreds of cells located in the right atrial wall near the opening of the superior vena cava
Peripheral Resistance
resistance to blood flow caused by friction of blood passing through blood vessels
Pressoreflex
baroreceptors in blood vessels, operating in feedback loops to maintain homeostasis of blood pressure; also called pressoreflex
Stroke Volume
amount of blood that is ejected from the ventricles of the heart with each beat
Systole
contraction of the heart muscle
Vasoconstriction
(vay-soh-kon-STRIK-shun) [vaso- vessel, -constrict- draw tight, -ion state of]
Vasodilation
(vay-soh-DYE-lay-shun) [vaso- vessel, -dilat- to widen, -ion state of]
Venous Return
refers to the amount of blood that is returned to the heart by way of the veins. Various factors influence venous return, including the reservoir function of veins, which occurs whenever blood pressure drops and the elasticity of the venous walls adapts the diameter of veins to the lower pressure, thus maintaining blood flow and venous return to the heart
List the principal structures of the heart's conduction system.
Sinoatrial node, atrioventricular node, AV bundle, and Purkinje system
are the three types of deflection waves seen in a typical ECG?
P wave, QRS complex, and T wave
What event does each type of ECG wave represent?
P wave: represents depolarization of the atria. QRS complex: represents depolarization of the ventricles. T wave: reflects repolarization of the ventricles
Using Figure 19-8, describe the major events of the cardiac cycle.
Atrial systole: emptying of blood out of the atria into the ventricles. Isovolumetric ventricular contraction: between the start of ventricular systole and the opening of the semilunar valves. Ejection: The semilunar valves open and blood is ejected from the heart. Isovolumetric ventricular relaxation: period between closure of the semilunar valves and opening of the atrioventricular valves. Passive ventricular filling: Return of venous blood increases intraatrial pressure until the atrioventricular valves are forced open and blood rushes into the relaxing ventricles
As the ventricles contract, their volume remains constant for a period of time. Can you explain why the volume does not begin to decrease immediately?
The abrupt inflow of blood that occurred immediately after opening of the atrioventricular valves is followed by a slow but continuous flow of venous blood into the atria and then through the open atrioventricular valves into the ventricles. This (diastasis) lasts about 0.2 second and is characterized by a gradual increase in ventricular pressure and volume.
State the primary principle of circulation.
Fluid always travels from an area of high pressure to an area of low pressure. Blood tends to move from an area of high average pressure at the beginning of the aorta toward the area of lowest pressure at the end of the venae cavae. Blood flow between any two points in the circulatory system can always be predicted by the pressure gradient
Relate stroke volume and heart rate to cardiac output.
Stroke volume x heart rate = Cardiac output
8. If the amount of blood returned to the heart increases, what happens to the stroke volume? What principle explains this?
An increase in the amount of blood to the heart will tend to increase stroke volume. Starling’s Law of the Heart
How does the body use a pressoreflex to counteract an abnormal increase in heart rate? An abnormal decrease in heart rate?
These pressoreflexes contain receptors (baroreceptors) sensitive to changes in pressure. Baroreceptors operate with integrators in the cardiac control centers in negative feedback loops that oppose changes in pressure by adjusting heart rate
10. Peripheral resistance is affected by two major factors: blood viscosity and what else?
Diameter of arterioles and capillaries
the diameter of the arteries decreases, what effect does it have on peripheral resistance?
A decrease in the diameter of the arteries will result in an increase in peripheral resistance
In general, how do vasomotor pressoreflexes affect the flow of blood?
Vasomotor reflexes detect changes in blood pressure and send the information back to the cardiac control center and the vasomotor center in the medulla. In response, these control centers alter the ratio between the sympathetic and parasympathetic output. If the pressure is too high, a dominance of parasympathetic impulses will reduce it by slowing heart rate, reducing stroke volume, and dilating blood “reservoir” vessels. If the pressure is too low, a dominance of sympathetic impulses will increase it by increasing heart rate and stroke volume and constricting reservoir vessels
What is a chemoreflex? How do chemoreflexes affect the flow of blood?
Chemoreflexes detect changes in carbon dioxide, decreases in oxygen, and decreases in pH. When changes are detected, this information is fed back to the cardiac control center and the vasomotor control center of the medulla, which, in turn, alter the ratio of parasympathetic and sympathetic output. When oxygen drops, carbon dioxide increases, and/or pH drops, a dominance of sympathetic impulses increases heart rate and stroke volume and constricts reservoir vessels, in response.
What is meant by the term venous return?
Venous return refers to the amount of blood that is returned to the heart by way of the veins.
Briefly describe how the respiratory pump and skeletal muscle pump work.
The respiratory pump operates by alternately decreasing thoracic pressure during inspiration and increasing pressure in the thorax during expiration. The skeletal muscle pump operates by the alternate increase and decrease in peripheral venous pressure that normally occur when the skeletal muscles are used for the activities of daily living.
How does Starling's law of the capillaries explain capillary exchange?
At the arterial end of a capillary, the outward driving force of blood pressure is larger than the inwardly directed force of osmosis—thus fluid moves out of the vessel. At the venous end of the capillary, the inward driving force of osmosis is greater than the outwardly directed force of hydrostatic pressure—thus fluid enters the vessel.
What three hormonal mechanisms work together to regulate blood volume?
Antidiuretic hormone, rennin-angiotensin and aldosterone mechanisms, and atrial natriuretic hormone.
What is meant by the term minute volume?
Minute volume is the volume of blood circulating through the body per minute.
How is minute volume related to peripheral resistance?
The volume of blood circulated per minute is directly related to mean arterial pressure minus central venous pressure and inversely related to resistance.
What device is used in clinical settings to measure arterial blood pressure?
Sphygmomanometer.
Which is more important for assessing health—the systolic pressure or the diastolic pressure?
Diastolic pressure.
In which type of vessel is blood most likely to be flowing at a very slow rate—an artery, a capillary, or a vein?
Capillaries
Without being specific, where are pulse points normally located in the body?
Radial artery, temporal artery, common carotid artery, facial artery, brachial artery, popliteal artery, posterior tibial artery, and dorsalis pedis artery
Hemodynamics
a term used to describe a colection of mechanism that influence the active and changing or dynamic circulation of blood
Intrinsic rythym
this means w/o any stimulation by nerve impulses from the brain and cord, they themselves initiate impluses at regular intervals.