Chapter 21 Assessment of Cardiovascular Function Flashcards
Function of the Heart
Pump blood to tissues (supplies them w/O2 & other nutrients)
Layers of the Heart (3)
Endocardium, Myocardium, & Epicardium
Endocardium
Consists of endothelial tissues and lines the inside of the heart and valves
Myocardium
Middle layer of the heart composed of muscle fibers & is responsible for the pumping action
Epicardium
Exterior layer of the heart
Pericardium
A thin, fibrous sac that protects the heart
Pericardial Space
The space between the pericardium’s two layers that is filled w/ ~20 mL of fluid
-Lubricates the surface of the heart
-Reduces friction during systole
Diastole
All 4 chambers of the heart relax simultaneously, which allows the ventricles to fill in prep for contraction
-Ventricular filling phase
Systole
Period of ventricular contraction resulting in ejection of blood from the ventricles into the pulmonary artery & aorta
What comes first? Atrial systole or diastole?
Atrial systole comes first, at the end of diastole, followed by ventricular systole
Where does the right side of the heart distribute blood to?
The RT side of the heart (RT atrium & RT ventricle) distributes venous blood to the lungs via pulmonary artery for oxygenation
What is the only artery in the body that carries deoxygenated blood?
The pulmonary artery
From where does the RT atrium get blood from?
Superior vena cava: Head, neck, & upper extremities
Inferior vena cava: Trunk & lower extremities
Coronary sinus: Coronary circulation
Where does the left side of the heart distribute blood to?
The LT side of the heart (LT atrium & LT ventricle) distributes oxygenated blood to the remainder of the body via the aorta
Where does the LT atrium receive blood from?
Receives oxygenated blood from pulmonary circulation via 4 pulmonary veins
Apical impulse
Impulse normally palpated at the 5th intercostal space, LT midclavicular line
-Caused by LT ventricular contraction
Atrioventricular (AV) Valves
Separate the atria from the ventricles
Tricuspid Valve
Composed of 3 leaflets that separate the RT atrium from the RT ventricle
Mitral/Bicuspid Valve
Composed of 2 cusps that lies between the LT atrium from the LT ventricle
Coronary Arteries
Supply the heart with blood & nutrients
-LT main coronary (LT descending & circumflex)
-RT main coronary
Where do the coronary arteries originate from?
They originate from the aorta, right above the aortic valve leaflets
When are the coronary arteries perfused?
They are perfused during diastole
As heart rate increases…
…diastolic time is shortened
-May not allow adequate time for myocardial perfusion
Myocardial ischemia
Condition in which heart muscle cells receive less oxygen than required
Cardiac Conduction System
Specialized heart cells strategically located throughout the heart that are responsible for methodically generating & coordinating the transmission of electrical impulses to the myocardial cells
Automaticity
Ability to initiate an electrical impulse
Excitability
Ability to respond to an electrical impulse
Conductivity
Ability to transmit an electrical impulse from one cell to another
Sinoatrial (SA) Node
Primary pacemaker of the heart
Atrioventricular (AV) Node
Secondary pacemaker of the heart
Depolarization
Electrical activation of a cell caused by the influx of sodium into the cell while potassium exits the cell
Repolarizatoin
Return of the cell to resting state, caused by the reentry of potassium into the cell while sodium exits the cell
Phase 0
Cellular depolarization is initiated as (+) ions influx into the cell
-Atrial & ventricular myocytes rapidly depolarizes as Na+ moves into the cell via sodium channels
-SA & AV node depolarize when Ca+2 enters these cells via slow-calcium channels
Phase 1
Early cellular repolarization begins during this phase as K+ exits into intracellular space
Phase 2 (Plateu Phase)
Rate of depolarization slows (Ca+2 ions enter intracellular space)
Phase 3
Completion of repolarization & return of the cell to its resting state
Phase 4
Resting phase before next depolarization
Effective Refractory Period
Cell is completely unresponsive to any electrical stimulus
-Incapable of initiating an early depolarization
Relative Refractory Period
If the electrical stimulus is stronger than normal, the cell may depolarize prematurely
Hemodynamic Monitoring
Use of pressure monitoring devices to directly measure cardiovascular function
Cardiac Output (CO)
Total amount of blood ejected via one of the ventricles in L/min
Formula for Calculating Cardiac Output (CO)
CO = HR X SV
Stroke Volume
Amount of blood ejected from one of the ventricles per heartbeat
Factors that Affect the Metabolic Demand of Tissues
Exercise, stress, & illness
PSNS Heart Rate Control
Branches of the PSNS travel to the SA node via vagus nerve
->Vagus nerve stimulation slows down the HR
SNS Heart Rate Control
SNS increases HR via innervation of the beta-1 receptor sites w/in the SA node
Baroreceptors
Specialized nerve cells w/in the aortic arch & in both LT & RT carotid arteries
Preload
The degree of stretch of the ventricular cardiac muscle fibers at the end of diastole
When is the degree of ventricle muscle stretch the highest?
It is highest at the end of diastole
As the volume of blood returning to the heart increases…
…muscle fiber stretch also increases
-Preload increases
->Results in stronger contractions & greater stroke volume
Frank-Starling Law
The greater the initial length or stretch of the sarcomeres (cardiac muscle cells), the greater the degree of shortening occurs
What decreases preload?
Reduction in volume of blood returning to the ventricles
-Diuresis
-Venodilating agents: Nitrates
-Excessive blood loss
-Dehydration: vomiting, diarrhea, diaphoresis
