Cardiovascular system Flashcards
(20 cards)
systole+diastole meanings
-systole=contraction
-diastole=relaxation
Cardiac Cycle (all the stages)
- Atria and ventricles are in diastole
- Blood flows into the atria via the pulmonary vein and vena cava
- This causes the pressure in the atria to rise
- At a certain point, atrial pressure becomes greater than ventricular pressure, causing the atrioventricular valves to open
- this causes blood to flow down into the ventricles from the atria
- Atrial systole occurs, forcing the remianing blood down into the ventricles
- Ventricular systole occurs, rapidly increasing the pressure in the ventricles
- At a certain point, the pressure in the ventricles becomes greater than the pressure in the atria, causing atrial diastole, and the atrioventricular valve to close, preventing backflow of blood into the atria
- This also causes the semilunar valve to open, and blood flows from the ventricles and out of the heart via the pulmonary vein and aorta
- Ventricular diastole then occurs, and at a certain point the pressure in the aorta and pulmonary vein becomes greater than the ventricular pressure and the semilunar valves close, preventing backflow of blood into the ventricles
- The heart is then ready for another cardiac cycle
Heart is myogenic
-The heart is myogenic, meaning it generates it’s own impulse
Sino atrial node (SAN) (conduction system in relation to the cardiac cycle)
-Located in the right atrium
-initiates the electrical impulse
-causes atrial systole
-determines heart rate
Atrioventricular node (AVN) (conduction system in relation to the cardiac cycle)
-Located between the atria and ventricles
-Delays the impulse by 0.1 seconds to allow full atrial contraction and ventricular filling before ventricular systole
Bundle of his (conduction system in relation to the cardiac cycle)
-Located in the septum of the heart
-Bundle of his splits the impulse from the AVN into two
-Left and right bundle branches conduct the impulse to the Purkinje fibers
Purkinje fibers
-Located on the walls of both ventricles
-Causes ventricular systole (pushes blood out of the heart)
Cardiac values definitions and units (e.g heart rate, stroke volume, cardiac output etc)
-Heart rate - The number of cardiac cycles per minute (bpm)
-Stroke volume: The volume of blood ejected out of the left ventricle per beat (ml/L)
-Cardiac output: The volume of blood ejected out of the left ventricle per minute (L/min)
Cardiac output formula
-Cardiac output (L/min)= heart rate (bpm) x stroke volume (L)
Cardiac Values (Heart rate (bpm))
-Trained at rest= 50 bpm
-Untrained at rest= 70-72 bpm
-Trained at maximal exercise= 220-age
-Untrained at maximal exercise= 220-age
Cardiac Values (stroke volume (ml))
-Trained at rest= 100ml
-Untrained at rest=70ml
-Trained at maximal exercise= 120-200ml
-Untrained at maximal exercise=90-120ml
Cardiac values (cardiac output (L/min))
-trained at rest= 5L/min
-Untrained at rest=5L/min
-Trained at maximal exercise= 30-40L/min
-Untrained at maximal exercise=20-30L/min
effects of cardiac values on sub-maximal/maximal exercise (heart rate)
-SUB MAXIMAL
-heart rate slightly increases at rest due to the release of adrenaline, during exercise, heart rate increases steadily and then plateaus; during recovery, heart rate decreases steadily until reaching resting hear rate
MAXIMAL
heart rate slightly increases due to the release of adrenaline; during exercise, heart rate increases rapidly until it reaches maximum heart rate; during recovery, heart rate decreases at a steady rate
effects of cardiac values on sub maximal/maximal exercise (stroke volume)
-SUB MAXIMAL
- Stroke volume steadily increases, then plateaus at max value
MAXIMAL
- the plateau (max SV value) continues
Frank starling law
-The greater the venous return, the greater the stretch of the ventricular walls, therefore the greater the force of contraction, leading to increased stroke volume
effects of cardiac values on sub maximal/maximal exercise (cardiac output)
SUB MAXIMAL
-Cardiac output gradually increases then plateaus
MAXIMAL
-Plateau stays steady at the same value (cardiac output)
Two main nerves involved in the redistribution of cardiac output
During exercise = accelerator nerve
During recovery= vagus nerve
Redistribution of cardiac output (during exercise)
1.During exercise chemoreceptors detect an increase in CO2 and a decrease in O2, baroreceptors detect an increase in blood pressure, and mechanoreceptors detect an increase in muscle activity
2.These receptors send the information to the Cardiac control center (CCC) in the medulla oblongata in the brain
3.The CCC uses the parasympathetic nervous system to increase the heart rate via the accelerator nerve
4. At working muscles, the CCC causes the arterioles to vasodilate and the pre-capillary sphincters to dilate, therefore increasing the blood flow to working muscles
5. At non-vital organs, the CCC causes arterioles to vasoconstrict and pre capillary sphincters to close, reducing blood flow to non-vital organs
Redistribution of cardiac output (during recovery)
1.During recovery; chemoreceptors detect a decrease in CO2 and an increase in O2, baroreceptors detect a decrease in blood pressure, and mechanoreceptors detect a decrease in muscle activity
2.These receptors send this information to the Cardiac control center (CCC) in the medulla oblongata in the brain
3. The CCC then uses the parasympathetic nervous system to decrease the heart rate via the vagus nerve
4. At the muscles, the CCC causes the arterioles to vasoconstrict and the pre-capillary sphincters to close, therefore reducing blood flow to muscle tissues
5. At non-vital organs, the CCC causes the arterioles to vasodilate and the pre-capillary sphincters to open, increasing the blood flow to non-vital organs
Mechanisms of venous return
-Pocket valves- prevents the backflow of blood
-Skeletal muscle pump- muscles contract to squeeze more blood back to the heart
-Respiratory pump- Thoracic cavity creates a difference in pressure, therefore squeezing more blood back to the heart
-Gravity- Allows blood from the upper body to return to the heart faster
