Chapter 5 The Heart and Monitoring Heart Function Flashcards
Why do multicellular organisms need a mass transport system?
Multicellular organisms need a mass transport system because:
-there is a higher demand for nutrients and greater production of waste
-higher metabolic rate
-more active organisms which means that there is a larger number of cells respiring very quickly so a greater demand for oxygen, glucose and carbon dioxide
-the SA:V is too low for diffusion to deliver nutrients at an appropriate rate nor remove wastes at a suitable rate
-hence a transport system is needed to ensure the demand of all individual cells is met
The Cardiac cycle: Atrial systole (and ventricle diastole)
During atrial systole muscles in the atrial walls contract, whereas muscles in the ventricle walls relax. This causes an increase in atrial pressure and a decrease in atrial volume, forcing the atrioventricular valves open. Blood is forced into the ventricles.
Ventricular systole
During ventricular systole muscles in the ventricle walls contract only once waves of excitation pass through the Purkyne fibres, whereas muscles in the atrial walls relax. This causes an increase in ventricular pressure and a decrease in ventricular volume, forcing the atrioventricular valves closed and the semi lunar valves open. Blood is forced into the arteries.
Complete cardiac diastole (ventricular and atria diastole)
-Both atria and ventricles relax
-higher pressure in pulmonary artery and aorta so semi lunar valves close to prevent backflow of blood into ventricles
atria fill with blood (increasing their pressure) due to higher pressure in the vena cava and pulmonary vein
ventricles continue to relax so pressure in atria is greater than pressure in ventricles
AV valves open and blood flows passively into ventricles
process continues
When will valves open?
Valves open when the pressure behind them is greater than the pressure in front of them.
Explain how valves close
Valves close when pressure in front of the valve is greater than the pressure behind.
Control of the cardiac cycle
Electrical impulse is generated at sinoatrial node (SAN)
Electrical impulses sent across atrial walls.
Muscles in atrial walls contract
Layers of non-conducting collagen tissue between atria and ventricles prevents wave of excitation passing directly to ventricles.
AVN receives impulse which causes a slight delay to ensure the atria have stopped contracting before the ventricles contract.
Electrical impulse is sent down bundle of His.
Impulse sent to perkinje fibres.
Electrical impulse arrives at apex of the heart.
At apex, Purkyne fibres spread out through both ventricle walls. Waves of excitation triggers simultaneous contraction of ventricles starting at the apex ( to allow more efficient emptying of ventricles) ventricular systole occurs from the bottom of the heart upwards
Explanation for when the calculated value is greater than the critical value
Calculated value is greater than the critical value
degrees freedom
there is a less than 5% probability that the difference between mean pulse rate…and… is due to chance.
rejecting the null hypothesis.
there is a statistically significant difference between…
Explanation of calculated value
Calculated value is less than the critical value
degrees freedom
there is a more than 5% probability that the difference between…and…
accept the null hypothesis
there is not a statistically significant difference between…and…
Cardiac Muscle of the heart
-myogenic
-muscle contracts in regular rhythm
does not fatigue
-specialised striated muscle
-fibres are branched and uninucleated
-cardiac muscle cells interconnect resulting in simultaneously contraction
intermediate contraction speed and intermediate length of contraction
cardiomyocytes supplied with oxygen and glucose by coronary artery if it becomes blocked—-> heart attack
Function of aorta
-carries oxygenated blood at (high pressure as it has to force the blood over a large distance hence overall there is higher resistance within the blood vessels) from left ventricle to the body
function of pulmonary artery
-carries deoxygenated blood from right ventricle to the lungs
function of pulmonary vein
-carries oxygenated blood from lungs to right atrium
Function of atria
-contract to generate a force to move blood at low pressure into the ventricles
pressure is low as walls of atria are thin (less cardiac muscle)
Both atria always contract simultaneously
Function of carotid arteries
-blood vessels that carry oxygen-rich blood to the head, brain and face
Function of ventricles
-contract to generate a force to move blood at high pressure out of the heart
Pressure is high as LV is thickest (most cardiac muscle)
LV: Forces oxygenated blood into aorta at high pressure
RV: forces deoxygenated blood into the pulmonary artery at lower pressure than LV as if it was the same, the pressure would be too high and would rupture the alveoli.
Both ventricles contract simultaneously
Function of semilunar valves
AORTIC valve: found between LV and aorta so prevents backflow of blood from aorta to LV during ventricular diastole
PULMONARY valve: found between the RV and the pulmonary artery so prevents backflow of blood from pulmonary to RV during ventricular diastole.
Function of Atrio-ventricular valves
Right atrioventricular valve:
prevents backflow of blood from RV to RA during ventricular systole.
closes when pressure in RV is greater than the pressure in RA
ensures deoxygenated blood flows into pulmonary artery.
Left atrioventricular valves: prevents backflow of blood from LV to LA during ventricular systole.
closes when the pressure of LV is greater than pressure of LA
ensures oxygenated blood flows into the aorta
Function of septum
-separates RHS from LHS so keeps oxygenated blood separated from deoxygenated blood
Function of vena cava
-carries deoxygenated blood from the body to RA
superior vena cava delivers deoxygenated blood from head
Inferior vena cava delivers oxygenated blood from rest of body
Function of chordae tendinae
-holds valves in place
-attaches valves to muscle wall of the ventricles
-prevents valves inverting when under pressure (during ventricular systole)
Function of Bundle of His and Purkyne fibres
Bundle of His is located in septum and Purkyne fibres located in walls of ventricles
AVN stimulates Bundle of His
Bundle of His conducts wave of excitation to apex of heart
Stroke volume
volume of blood pumped out of LV during each cardiac cycle
Cardiac Output
volume of blood pumped out of the LV each minute
Heart rate
number of beats per minute
Equation for CO
CO=SVXHR (cm cubed min -1)
Measuring pulse rate
Count number of beats in an artery in 30s and then double (less prone to counting errors so more accurate)
What is pulse?
distension of artery wall as blood surges through artery with ventricular systole, followed by elastic recoil of artery wall during ventricular diastole