Overview of CVS Flashcards
What is the cardiovascular system defined as?
The cardiovascular system is defined as the heart, blood vessels
and approximately 5 litres of blood
What is passive diffusion?
Random, undirected, thermal
movement of molecules
What is the equation used in passive diffusion?
Time t needed
to diffuse a net distance x
is proportional to
the square of distance
t is proportional to x^2
What is convection transport?
CONVECTION TRANSPORT
causes movement of fluids and solutes
down a pressure gradient
What does convection transport provide?
provides
in a resting healthy person
a circulating blood flow delivering
O2 transport to cells
of about 5 litres per minute
What does failure of heart or pressure gradient prevent?
Failure of heart (e.g., cardiac arrest)
or pressure gradient (e.g., sepsis)
prevents convection transport
- No O2 transport
to tissue and organs -
What type of circulation is the cardiovascular system and what are the parts in?
Cardiovascular System is a Dual circulation
Parts are in parallel and in series
What are the parts in parallel in the CVS?
-Cardiac output is ‘split up
-Safeguard O2 supply
-Most organs are supplied this way
What are the parts in series in the CVS?
-Liver and kidneys receive ‘used’ blood
-Can be an issue for these organs if CVS is
compromised
What type of system is the CVS?
The CVS is a closed system
What happens in the CVS in a closed system?
-5 l/min of blood returns to the right side of the heart (Venous circulation)
-5 l/min of blood is ejected by the right side of the heart to lungs and
-5 l/min of blood returns to left side of heart (Pulmonary circulation)
-5 l/min of blood is ejected by left ventricle to the body (Systemic circulation)
What is heart rate?
Number of heart beats per min
What is stroke volume and units?
(SV, ml) – Volume of blood ejected from heart per beat
What is cardiac output and units?
Cardiac Output (CO, ml/min) – Volume of blood ejected from heart per min
which is the same as Blood Flow (BF, ml/min) in circulation
What is the equation for cardiac output?
CO = HR x SV
What is blood pressure and units?
(mmHg) – Pressure of circulating BF on blood vessel walls
What is total peripheral resistance?
Resistance of arterial blood vessels to BF
What is the equation of arterial BP?
Arterial BP = CO x TPR
What is the equation for blood flow?
Blood flow = Arterial BP / TPR
What does the left ventricle do and what does this create?
Left ventricle - Ejects blood to body at high pressure
High ejection pressures create pressure difference with distance blood vessels
What is the pressure in the aorta?
Aorta (>100mmHg)
What is the pressure in small arteries?
Small arteries (30 mmHg),
What is the pressure in large veins?
Large veins (5 mmHg)
Cardiac muscle gets no nerve input, therefore it is?
Cardiac Muscle is MYOGENIC
What do SA nodes do?
Generates pacemaker potential
What do AV nodes do?
Slows conduction to allow
appropriate filling of ventricles
What do bundle branches, purkinje fibres do?
Conduction
What do atria and ventricles do to electrical conduction?
Action potentials converted into contraction
What are the steps involved in electrical conduction leading to contraction?
(1) Electrical activity generated in SA
node (non-contractile tissue)
spreads out into atria to produce
(2) contraction
Electrical activity enters AV node (non-
contractile tissue), which delays
conduction before stimulating ventricles
- allows ventricles to fill proper from
atrial contraction -
(3) Excitation conducts rapidly through
bundle of His into ventricles
(4) Excitation through purkinje fibres is
conducted throughout the ventricles
producing contraction
Where does ventricular excitation and contraction begin and spread to?
Ventricular excitation and contraction begins at the apex then spreads to base of heart
What is cardiac output?
Cardiac output = volume of blood ejected from ventricles per minute
What 4 things control cardiac output?
- Filling pressure
- sympathetic/parasympathetic autonomic nerves
- Chemical factors-hormones(adrenaline)
- Afterload
What may affect filling pressure?
e.g., Hypovolemia
i.v. fluids given
Increases venous return and SV/CO
Maintains blood pressure and flow
What may affect sympathetic/parasympathetic autonomic nerves?
e.g., Exercise
Increase in sympathetic NS
(release of noradrenaline and adrenaline)
Increase in HR and SV
Increasing CO to > 20 l/min
What may affect afterload?
e.g., Hypertension
High arterial BP
opposes ejection
of blood
Can lead to reduced
SV and heart failure
What is the equation for blood velocity?
Blood velocity = blood flow(cm^3/s)/ cross sectional area(cm^2)(number x pi*r^2 per vessel)
What do arterioles determine and set?
Arterioles determine TPR and set arterial blood
pressure upstream
Why is the pulmonary system low pressure?
low pressure system (allows gaseous exchange to occur)
What is the equation for blood flow?
Blood flow = Arterial BP / TPR
What does a decrease in cardiac output lead to?
Decrease in blood volume
(hypovolemia)
e.g., haemorrhage or dehydration
Will reduce BP and produce poor
blood flow to tissues
What does increased TPR lead to?
Excessive arteriole constriction
will ‘switch off’ blood flow to tissues
Associated with increase arterial BP
upstream of constriction
e.g., in hypertension
What is the equation for BP?
BP=CO*TPR
What are the 4 main functional groups that blood vessels form?
1.Elastic vessels
2.Resistance vessels
3.Capacitance vessels
4. Exchange vessels
What do elastic vessels do?
Accommodate stroke volume
Convert intermittent ejection
into continuous flow
What do resistance vessels do?
Control arterial BP
Control local blood flow
What do capacitance vessels do?
Control filling pressure
Reservoir of blood
What do exchange vessels do?
Nutrient delivery to cells
Tissue water
& lymph formation
Removal of metabolic waste
Where is most of the distribution of blood volume?
Large veins, small veins and venules make up 65%
