Circulatory & Respiration Flashcards
Increase in venous return results in an increase in _____, which lengthens cardiac fibers, which improves the force of contractility, resulting in an increase in _____.
- End-Diastolic BP
2. Stroke Volume
End-Diastolic Volume
(Preload)
How much blood is in the left ventricle before it squeezes
Factors of Venous Return
- Venoconstriction
- Muscle Pump
- Respiratory Pump
Venoconstriction
Reduces the volume capacity of the veins to store blood –> blood moves toward heart
Muscle Pump
When muscles contract during exercise, they compress veins & push blood back toward the heart
Respiratory Pump
During inspiration, pressure in the thorax decreases & the abdominal pressure increases. This creates a flow of venous blood from the abdominal region into the thorax = venous return
Predominant factor of venous return.
Stroke Volume
Volume per beat
Stroke Volume is regulated by?
- End-Diastolic Volume
- Afterload (Aortic BP)
- Strength of ventricular contraction (Contractility)
Preload
The pressure on the wall of the heart
**more blood = more pressure
Afterload
The pressure on the aortic semilunar valve (Diastolic BP)
Overcoming the pressure to open the semilunar valves
Stroke Volume in relation to Afterload
SV is inversely proportional to the Afterload; increase in aortic pressure produces a decrease in SV
Contractility
How hard the heart squeezes
Mechanisms of Contractility
- the effect of epinephrine & norepinephrine
- direct sympathetic stimulation by cardiac accelerator nerves
Both increase the Calcium available to the myocardial cell
Ejection Fraction
The percentage of blood pumped out of a filled ventricle during contraction.
The greater the EF, the greater the Stroke Volume which increases Cardiac Output.
Cardiac Output
Volume of blood pumped to the body per minute
Q= HR * SV
Heart Rate
Beats per minute
Isovolumic Contraction
The pressure increases while volume stays the same
Surfactant
Lowers the surface tension of the alveoli & prevents its collapse
Purpose of the Cardiovascular System
- The transport of O2 to the tissues & removal of wastes
- The transport of nutrients to tissues
- Regulation of body temperature
Myocardium
“Heart Muscle”
-responsible for contracting & forcing blood out of the heart
Cardiac Muscle Fiber vs. Skeletal Muscle Fibers
- They’re shorter & connected in a tight series; branched & contraction is involuntary
- They’re interconnected via intercalated discs (permit the transmission of electrical impulses from one fiber to another)
- Fibers cannot be divided into different fiber types (type similar to SO Type I)
Systole
Contraction phase of the cardiac cycle
Diastole
Relaxation period of the cardiac cycle
Heart 2-Step Pumping Action
- Right & Left Atria contract together, which then empties atrial blood into the ventricles.
- Then ventricular contraction occurs, delivering blood into systemic & pulmonary circuits.
Blood Distribution During Rest
Systole ejects 2/3s of the blood in the ventricles, leaving 1/3 in the ventricles. Ventricles then fill with blood during the next diastole (longer time in diastole)
The effects of rising heart rate on Diastole & Systole
Rising heart rate results in a greater time in reductionism diastole, whereas systole is less affected. (Diastole is reduced greatly)
Pressure Changes During the Cardiac Cycle
70% of the blood entering the atria during diastole flows directly into the ventricles through the atrioventricular valves before contraction. Contraction then forces the remaining 30% into the ventricles.
The rise in pressure closes the AV Valve & prevents backflow.
Pressure Changes During the Cardiac Cycle (continued…)
When the ventricular pressure exceeds the pressure of the pulmonary artery & the aorta, the pulmonary & aortic valves open & blood is forced into both pulmonary & systemic circulations.
Heart Sounds
1st- closing of the AV valve
2nd- closing of the aortic & pulmonary valves
Systolic BP
Pressure generated as blood is ejected from the heart during ventricular systole
Diastolic BP
Time during ventricular relaxation (diastole) & the arterial blood pressure decreases
Mean Arterial Blood Pressure (MAP)
Average pressure during the cardiac cycle at REST
-determines the rate of blood through the systemic circuit
Pulse Pressure
Difference between systolic & diastolic blood pressure
Hypertension
High blood pressure
Rise above 140/90mmHG
Mean Arterial BP is determined by:
- Cardiac Output
- Total Vascular Resistance
Increase in determents = increase of MAP
Blood Pressure Factors
- Cardiac Output
- Blood Volume
- Resistance to Flow
- Blood Viscosity
What regulates BP?
Acute: sympathetic NS
Long-Term: kidneys
-kidneys regulate BP by controlling blood volume
Total Vascular Resistance
Sum of resistance to blood flow provided by ALL systemic blood vessels
Increase in Arterial BP
Baroreceptors send impulses to the cardiovascular control center, which responses by decreasing sympathetic activity
Decrease in Arterial BP
Reduction of baroreceptor activity to the brain, resulting in Cardiovascular Control Center increasing sympathetic outflow
Sinoatrial Node (SA Node)
Pacemaker of the heart; electrical activity occurs
Modified by:
- parasympathetic NS
- sympathetic NS
Heart Rate Breakdown
HR increases at the beginning of exercise due to withdrawal of parasympathetic tone.
At higher work rates, the increase in HR is achieved via an increased sympathetic outflow to the SA Nodes.
Hemodynamics
The study of pressure, resistance, & flow of blood
Blood Flow Resistance Factors
- length of the blood vessel
- viscosity of the blood
- RADIUS OF THE VESSEL
Resistance = (length * viscosity) / Radius^4
Greatest vascular resistance to blood flow
Occurs in the arterioles.
Increased Oxygen Delivery to Exercising Skeletal Muscles is Accomplished by:
- Increase in Cardiac Output
2. Redistribution of blood flow from inactive organs to working muscle
