Circulation Flashcards
What is the function of the kidneys?
How are they controlled?
Plasma volume control
Glomerular filteration rate (GFR)- all fluid entering all Bowmans capsules. Increased renal blood flow increases GFR
Endocrine and autonomic NS
State 6 function of circulation
How is pulmonary circulation different to systemic circulation?
Infection control
Supply oxygen and glucose to respiring cells
thermal regulation
removing waste
haemostasis of extracellular fluid in kidneys
Distribution of hormones
Pulmonary circulation is in series, systemic circulation is in parallel
Whats the equation for BP and how are resistance, pressure and flow related ?
BP=CO x PR
Blood flow rate = pressure difference/ resistance
Blood pressure is the balance between circulatory blood volume and circulatory capacity.
State the function of each blood vessel type.
Aorta - stretch and recoil, energy Arteries- distribute, volume adjust Arterioles- regulate capillary pressure, set BP and TPR Capillary- exchange Venules- collect blood, some exchange Veins- blood reservoir, muscle pump
How does the right and left heart differ in appearance in the sagittal plane? Any other differences?
Right- Crescent shape
Left - Circular cross section
Compare the changes in pressure between
a) LV systole and aortic systole
b) LV systole and arterial pressure
c) Arterial and LV diastole
d) LV systole and RV systole
e) LV diastole and mean LA/RA
f) RV systole and RV diastole
g) mean LA and mean RA
a) Equal
b) Approx. equal
c) Ten times >
d) Five times >
e) LVD approx. equal
f) 5-7x >
g) >
Compare the changes in pressure between
a) PA systole and RV systole
b) PA diastole and PA systole
c) PA diastole and RV diastole
a) Equal
b) <
c) >
What is the apex beat?
During systole, the apex (most inferior and lateral part of the heart) strikes the chest wall.
Describe the differences between atrioventricular valves and semi-lunar valves with examples.
Atrioventricular valves: Tricuspid valve and Mitral valve Papillary fibres Closed during systole Responsible for "Lub" sound
Semilunar valves:
Pulmonary valve and Aortic valve
Diastole time > Systolic time so delayed “Dub”
Outline the steps involved contraction of the heart.
Cardiomyocyte is stimulated by neighbouring cells or conducting cells
Action potential causes extracellular environment to become more negative and the intracellular environment to become less negative
Increase in cytosolic free calcium ions
Muscle contraction
Calcium ions removed and muscle relaxes
Describe the changes in GFR according to the following changes:
a) Increase in size of afferent artery, decrease in efferent artery size
b) Decrease in size of afferent artery
a) increase in pressure, increase in filtration
b) decrease in pressure, decrease in filtration
Define a) Hypoxia b) Anoxia c) Hypoxaemia and d) Ischaemia
State a possible cause of Hypoxia and Ischaemia
a) Hypoxia - insufficient O2 supply to an area of the body
b) Anoxia- complete deprivation of O2 supply (low po2)
c) Hypoxaemia- insufficient O2 throughout arterial blood
d) Ischaemia- insufficient perfusion
Hypoxia can be caused by hypoxaemia and/or ischaemia.
Ischaemia can be caused by blockage, constriction of a vessel, decreased BP or insufficient pressure generation by the heart
Describe the fast homeostatic response to decreased cardiac output.
Increased sympathetic activity leading to:
Increased heart rate
Increased heart contractility
Vasoconstriction
Describe the slow homeostatic response to decreased cardiac output.
Kidneys accumulate fluid which leads to decreased GFR
As a result an increase in central venous pressure
Leads to increased venous return and increased preload
Describe the similarities and differences between a low output stage and a low volume state.
Both end in shock
Low output stage more common in patients over 50 and maintains normal blood pressure.
Low volume stage can occur at any age and is due to loss of fluid (i.e. haemorrhage and diuresis)
State the equation for cardiac output. Which factors effect it?
CO= HR x SV
Stroke volume is affected by contractility, preload and after load. Preload itself is affected by venous tone and volume. If returning blood vessels high, preload likely to increase
What is meant by mean arterial pressure and what is the equation used to calculate it?
MAP, or mean arterial pressure, is defined as the average pressure in a patient’s arteries during one cardiac cycle.
MAP= DBP + 1/3(SBP-DBP)
Define stroke volume. Equation?
How does the heart rate and RR interval relate. What is the RR interval?
The volume of blood pumped out of one ventricle per beat. SV= EDV-ESV
Heart rate is 1/RR.
The RR interval refers to the QRST complexion an ECG. It depicts the interval between two successive peaks
Define end diastolic volume and end systolic volume.
EDV= The volume of blood in the ventricle after trial systole.
ESV= The volume of blood left in the ventricle after ventricular systole.
What is term given to the percentage of ventricular volume pumped out during a heart beat? What is its formula?
How can this be indicative of heart failure ?
Ejection fraction = SV/EDV
Ejection fraction is less than 40% in HF
What does Poiseuilles law suggest to us about blood flow.
Viscosity, radius and length of BV change the flow of blood.
An increase in the blood vessel radius will cause the greatest increase in blood flow (i.e. decreased resistance)
Describe the physiological changes that occur during exercise and when standing in terms of blood vessels, HR and BP.
Exercise causes peripheral vasodilation and vasoconstriction of inactive skeletal muscles and the gut.
HR increases as does systolic BP. Diastolic pressure decreases
When standing the blood follows gravity and wants to pool in the lower extremities and not the brain. The sympathetic system senses the initial drop in BP and employs compensatory measures.
HR increases as does diastolic BP. Systolic pressure remains the same
Describe the three methods by which systemic pressure is controlled
Local- NO from endothelium
Neurological- autonomic sympathetic: noradrenaline
Humoral- kidney secreted hormones as does pituitary and adrenal gland.
Describe the two forces that act on blood vessel walls.
Hydrostatic pressure
Shear force: frictional force parallel to the wall
It is atheroprotective and enhanced by laminar flow
Describe the location and function of baroreceptors
Carotid sinuses, left and right internal carotid arteries
Senses low blood pressure
Describe the location and function of chemoreceptors
Carotid bodies and aortic bodies
Detect low O2
Describe the key principles of the Frank-Starling mechanism
The stroke volume of the heart is directly proportionate to the end diastolic volume, to an extent.
The heart pumps a greater volume with greater force.
What is the difference between preload and afterload?
How does volume overload occur?
How does pressure overload occur?
Preload is the initial stretching by cardiac myocytes of the ventricles during diastole. It depends on venous return
Afterload the resistance that the chambers of the heart must overcome in order to eject blood out of the heart. It can be increased by back pressure and failure of exit valves to open.
Preload too large which causes the heart is overfilling
Afterload load to large
Which factors can affect preload?
Increased ventricular compliance (increases elasticity
Decreased heart rate (increased diastolic time)
Increased central venous return
Increased aortic pressure because the ventricle doesn’t empty enough
Describe features of pulmonary circulation
High capillary density low vascular resistence acts a blood reservoir Endocrine control of bp (produces ACE) filter
When O2 supply to lungs is low or ventilation is low, vasoconstriction occurs and perfusion is low to minimise the blood that is poorly oxygenated.
Describe the difference between laminar and turbulent flow.
How does tension and vessel size relate?
Laminar flow is slower at edges due to friction.
Turbulent flow occurs in high speed, low viscosity and branching vessels. Its caused by junctions, mixing, atherosclerosis and endothelium damage.
The greater the vessel, the greater the wall tension
Describe functions of the endothelium
- Maintaining blood vessel tone: local control of perfusion, vasodilation (NO)
- Fluid filteration: as in blood brain barrier, CSF, glomerulus, GI secretions
- Haemostasis
- White cell recruitment
- Angiogenesis
- Hormone trafficking: e.g. as in transcytosis (travel through the cytoplasm of a cell)
What is meant by contractility?
The intrinsic ability of the myocardium to contract
