lecture 3 - cardiovascular physiology Flashcards
where does gas exchange take place?
between the blood and tissues
what are the functions of the cv system?
circulate o2 and co2, provides cells with nutrients, removes waste products of metabolism, clotting, regulate body temp, transport hormones, protect body against disease and infection
what happens in the heart?
blood flows from the right atrium to the right ventricle - deoxuygenated blood - then pumped to the lungs where it receives o2 - flows into the left atrium to the left ventricle where its then pumped around the body
what blood does the right side of the heart receive?
deoxygenated
what blood does the left side of the heart receive?
oxygenated
what does the bicuspid valve do?
causes a one way blood flow
what does the aortic valve do?
prevents blood flowing back into the heart between contractions
what does the superior vena cava do?
transports deoxygenated blood from upper body to right atrium
what does the inferior vena cava do?
transports deoxygenated blood from tissues below the heart to the right atrium
what are arterioles?
“resistance vessels” containing circular layers of smooth muscle, which can either constrict or relax to regulate blood flow to the periphery which allows redistribution of blood
what is blood pressure and what does it do?
cardiac output x total peripheral resistance - propells more blood out and increases output on the arterial walls
what is total peripheral resistance?
vessel diameter, vessel length, blood viscosity
what does the venus system do?
deoxygenated blood returns to the heart via the superior and inferior vena cava
why do arteries have thicker walls than veins?
more difficult for blood to be propelled through veins
what is myosin?
has myosin heads which bind to actin and pull it to the middle of the sarcomere which causes it to shorten and causes force to be generated
what is cardiac cellular structure and function?
During contraction of a cardiac muscle cell (cardiomyocyte), myosin heads pull actin towards the centre of the sarcomere, generating the force for contraction of the heart
what is depolarisation?
excitable cells - heart muscle cells can be activated, measure charge in the interior of the cell, due to diffs in the intracellular and extracellular concentrations of ions
pos ions flow into the cell so that it is less polarised
what is repolarisation?
pos ions flow out of the cell
what do action potentials mean?
causes an alteration in this permeability, sodium and ca cant enter the cell, permeability of this outcome changes, causes an influx of pos charged ions
what does the sinonatrial node do?
Specialised muscle tissue located in the top right of the right atrium which spontaneously depolarises and repolarises, which spreads throughout the right atrium to the atrioventricular node
what does the AV node do?
Specialised muscle tissue located near the interatrial septum which receives signals from the SA node and, following a brief delay, transmits them to the ventricles
what is step 1?
The SA node transmits a wave a depolarisation which begins to spread across the right and left atria
what is step 2?
Depolarisation is complete, and the atria contract, pumping blood into the ventricles.
When the depolarisation reaches the AV node, the impulse is delayed
what is step 3?
Ventricular depolarisation begins, traveling through the Bundle of His and onto the right and left ventricles (in orange in the image)
Simultaneously, there is repolarisation (relaxation) of the atria (in red in the image)
what is step 4?
Ventricle depolarisation is complete, and ventricles contract.
what is step 5?
ventricular repolarisation
what is the P wave?
atrial depolarisation
what is the QRS wave?
ventricular depolarisation
what is the T wave?
ventricular repolarisation
what is step 1 of the Wiggers diagram?
atrial depolarisation, which initiates atrial systole
what is step 2 of the Wiggers diagram?
With blood leaving the left atrium, the pressure drops to below that of the left ventricle, this causes the mitral/bicuspid valve to close.
- This represents the end of ventricular diastole. The volume of blood remaining in the left ventricle is the end-diastolic volume
what is step 3 of the wiggers diagram?
valves remain closed - isovolumetric contraction which causes pressure to rapidly increase
what is step 4 of the wiggers diagram?
Once ventricular pressure exceeds aortic pressure, the aortic valve opens and blood leaves the left ventricle.
what is step 5 of the wiggers diagram?
With blood leaving the left ventricle, the pressure within the left ventricle eventually drops to below that of the aorta, causing the aortic valve to close.
The volume of blood left in the ventricle following systole is the end systolic volume
what is step 6 of the wiggers diagram?
The t-wave represents ventricular repolarisation, causing ventricular diastole.
Pressure within the left ventricle continues to drop, causing it to fall below left atrial pressure, which in turn causes the mitral valve to open
what is step 7 of the wiggers diagram?
With the mitral valve open, blood passively flows into the left ventricle from the left atria, causing left ventricular volume to increase
what mechanisms regulate cardiac output?
SV, HR
what is the preload influence on SV?
ventricles stretched, blood leaves aorta
what is the afterload influence on SV?
resistance of lv must overcome to circulate blood through the aorta
what do resistance vessels do?
constrict and dilate to alter the amount of blood flow going to each of the things
what is the vascular network?
distribution/resistance, exchange, capacitance
what is functional anatomy?
an artery can contain smooth muscle and elastin - elastic tissue which gives it this compliance and allows the walls to stretch
why do venules and veins have thin walls?
more stretchy so hold more blood
what does arterial blood pressure mean?
blood pressure away from the heart
what do baroreceptors do?
detect a decrease in pressure, there is a reduction in the number/frequency of signals sent from the baroreceptors to the cardiovascular control centre in the medulla
