Chapter 7:Cardiovascular System Flashcards
Role of the Cardiovascular System
Comprises a complex transport network consisting of the heart, blood, and blood vessels acting together to maintain blood pressure
Eliminates metabolic waste products and carbon dioxide
Helps regulate blood pH
Maintains constant internal body temperature
Transports fuel and nutrients to working muscle and other tissues
Delivers hormones to their sites of action
Structure of the Heart
Two atrial chambers
Two ventricular chambers
Right ventricle: Pumps blood to lungs for oxygenation
Left ventricle: Pumps blood to peripheral tissues
The Heart Pump
Right and left heart pumps work in parallel and pump the same amount of blood at the same rate throughout each heartbeat.
The interventricular septum is a thick muscular wall that divides the right and left sides of the heart and prevents blood from mixing between the right and left ventricles.
Four one-way valves
–Two atrioventricular valves, a tricuspid valve, and a semilunar valve
Cardiac Tissue
Roughly the “size of your fist”
Cardiac chamber dimensions tend to be smaller in women.
Beats continuously throughout the life span (possibly up to 3 billion times)
Nourishes itself through its own blood supply
Can beat on its own without prior stimulation
Pericardium
Protective covering over the heart and anchors the large blood vessels entering and exiting the heart
Includes two separate layers of tissue
Serous pericardium (inner layer)- Parietal, visceral, pericardial space
Fibrous Pericardium (outer layer)
Cardiac Wall
Endocardium- innermost layer of heart
Myocardium- Middle layer, AKA “Cardiac Muscle”
Epicardium-Outermost layer- Houses major coronary blood vessels, cardiac nerves, and other small vessels
Myocardium
Striated- contains actin and myosin within sarcomeres and allows cardiac muscle to contract like skeletal muscle
Functions Involuntarily- no motor units and only Type 1 muscle fibers
Ability to depolarize and contract as one muscle
Relies almost exclusively on aerobic metabolism
Can be forced to rely on anaerobic metabolism in situations of decreased oxygen (CAD)
Pulmonary Circulation
Includes the right atrium and ventricle (the right heart pump) and the pulmonary arteries and veins
Delivers oxygen-poor blood (deoxygenated) from the right side of the heart to the lungs through the pulmonary arteries for gas exchange
Systemic Circulation
Comprised of the left atrium and ventricle (the left heart pump), the aorta, and all other blood vessels
Delivers fresh oxygenated blood to the peripheral organs and tissues.
Coronary Circulation
The coronary circulatory system includes blood vessels that supply the myocardium with blood.
Coronary circulation begins with the right and left main coronary arteries and then branches into smaller arteries.
The majority of blood flow through the coronary system occurs during diastole.
Stroke Volume
Stroke volume is the amount of blood ejected by the heart in one beat.
SV=EDV-ESV
EDV is the peak volume of blood that has filled the right and left ventricles during relaxation.
ESV is the volume of blood remaining in the ventricles after ejection.
In a healthy human at rest, the amount of blood that fills the heart (EDV) is typically 120 mL, while the amount of blood left over after ejection (ESV) is 50 mL.
Stroke volume would equal 70 mL.
Venous Return
Amount of blood returned to the heart from peripheral veins
Frank-Starling Law of the Heart: An increased stretch of the ventricles (preload) leads to a stronger contraction.
The greater the volume of blood returning to the heart during diastole (EDV), the greater volume of blood ejected during systole (SV).
Plasma Volume
Consists of mostly water, electrolytes, and plasma proteins
Loss in plasma volume = decreased stroke volume and drop in venous return/ventricular filling pressure
How Does Exercise Impact the Heart?
At high heart rates, EDV will be lower
Endurance exercise can cause increases in ventricular chamber size (greater filling volume and greater stroke volume)
Afterload
The resistance to eject blood out of the heart
Increased afterload=decreased stroke volume
Afterload decreases during cardiorespiratory exercise, which helps to enhance stroke volume and exercise performance.
During exercise, blood vessels vasodilate, which lowers the resistance of blood flow to the working muscle and reduces the load on the heart.
Resistance exercise tends to increase afterload, because high intramuscular compression impedes blood flow through the blood vessels.
Some Terms to Know…
Cardiac Output: Amount of blood pumped by the heart per minute
Q= HR x SV
120/80
Blood Pressure
Systolic blood pressure (SBP) is the pressure exerted on the systemic arterial walls during the period of ventricular systole (contraction).
Diastolic blood pressure (DBP) is the pressure exerted during the period of ventricular diastole (relaxation).
Rate-Pressure Product (RPP)= HR x SBP
Ejection Fraction (%EF)
Fraction of blood ejected from the ventricles per heartbeat
Ejection Fraction= (EDV-ESV)/EDV x 100%
Machine avaliable
Relation Among Pressure, Cardiac Output, and Vascular Resistance
Mean arterial pressure (MAP), cardiac output, and total peripheral resistance are the primary factors that govern the flow of blood from the heart to peripheral organs and tissues.
An increase in cardiac output or total peripheral resistance will increase blood pressure, whereas a decrease in cardiac output or resistance will lower blood pressure.
Blood flow will be elevated by either an increase in pressure or by a decrease in resistance.
Reducing the internal radius of a blood vessel (vasoconstriction) increases resistance, whereas increasing the radius (vasodilation) lowers resistance.
Neural Control of Cardiovascular System
Control of HR, BP, and ventricular contractility are controlled by higher brain centers in cerebral cortex referred to as central command.
Medulla oblongata is the primary coordinating center that receives sensory input from central commandand hypothalamus to maintaincardiovascular homeostasis.
Sympathetic Control
Upon activation from the cardiovascular control center, the nerve endings release the catecholamine norepinephrine, which acts to directly increase the pacemaker activity of the SA and AV nodes, thereby increasing heart rate to rates above 100 beats per minute.
Hemodynamics
Study of factors that contribute to the flow of blood through the cardiovascular system.
Regulated by: Pressure, flow, resistance
–If heart rate increases or if the heart contracts more forcefully, the delivery of blood will also increase.
–Changes in the resistance provided by the circulation can also affect the flow of blood.
Parasympathetic Control
Nerve impulses arising from the parasympathetic nervous system are transmitted by the vagus nerve to innervate the SA and AV nodes and atrial and ventricular myocardial cells.
Releases acetylcholine, a neurotransmitter that acts directly on the SA and AV nodes.
Parasympathetic tone—parasympathetic activity keeps heart rate below 100 beats per minute while at rest.
Peripheral Controlcontrol Blood flow
Mechanical Receptors (mechanoreceptors) sense changes in blood pressure, blood volume, and muscle tension
Ex: Baroreceptors
ChemicalReceptors (chemoreceptors) sense changes in blood gases (i.e., oxygen and carbon dioxide) and blood pH.
Thermoreceptors: Sense body temperature
Humoral Control of Cardiovascular System
Involves the release of substances into circulation that directly or indirectly affect heart rate and myocardial function, the degree of arteriolar vasodilation or vasoconstriction, and arterial blood pressure
Catecholamines (epinephrine and norepinephrine)
Renin-angiotensin Aldosterone System (RAAS)- Activation is central to hypertension, heart failure, and renal disease.Critical regulator of blood volume, electrolyte balance, and systemic vascular resistance.
Angiotensin- Elevates BP
Endothelin- Vasocontsriction
