Cardiac 1 Flashcards
What are the parts that make up the heart?
Chambers:
- Right atruim
- Left atrium
- Right ventricle
- Left ventricle
Valves:
- Pulmonary valve
- Mitral valve
-Tricuspid valve
- Aortic valve
Blood flow:
- Superior vena cave
- Pulmonary artery
- Inferior vena cava
- Pulmonary veins
What is the order that blood moves thru the heart to the body again?
- SVC or IVC
- Right atrium (thru AV vales ‘tricuspid’)
- Right ventricle (out the pulmonary vale)
- To the lungs
- Left atrium (thru AV vales, bicuspid ‘mitral’)
- Left ventricle (to aortic valve)
- Out of the aorta
What are the 2 mechanical contractions of the heart?
Constitute as two pumps in a series
- Right ventricle propels blood to pulmonary circulation
- Left ventricle propels blood to systemic circulation
What is the volume output from the LHS to the RHS of the heart
~5 liters/min or ~70 ml/beat
What is the pressure generated in the LHS of the heart?
~4x RHS ~120 vs 30 mmHg
Where does gas exch take place in the lungs?
In the capillary beds of the lungs
What is the pressure of the blood like when it leaves vs enters he heart?
Leaves = enters circulation w high pressue
Enters = blood in venous circulation is present at low pressure
Where does gax exch take place in the body?
In the capillary beds of all body tissues
How does deoxygenated blood return to the heart?
Via the vena cavae
During moderate exercise what is the total cardiac output?
12.5L/min
Maximal is 25-30L/min
At rest what is the total cardiac output?
5 L/min
During exercise what happens to CO?
CO inc to meet the inc metabolic needs of the body –> particularly due to inc blood flow req to skeletal muscles
What is the formula for Cardiac Output?
Cardiac output = Heart Rate X Stroke volume
(litres/min) (beats/min) (ml/beat)
What happens to venous return during exercise?
Rises bc of compression of veins by contracting skeletal muscle → inc CO
What happens to SNS activity during exercise?
Inc by higher brain centres which initiate exercise & in part by receptors in exercising muscles → HR inc which leads to inc in CO
What happens to PNS activity during exercise?
Inhibited during exercise which inc in CO
What is cardiac hypertrophy
This develops with prolonged training → left ventricle enlarges, raising SV
What are the factors affecting HR?
- Autonomic innervation
- Fitness level
- Age
What factor affects stroke volume?
- Heart size
- Gender
- Duration of contraction
How are the aorta & large arteries structured?
- Blood moves rapidly through the aorta & its arterial branches
- Branches become thinner as they approach the periphery
- In larger arteries, pressures are only slightly lower than in aorta
What is the structure of of the aorta & large arteries?
Thick walled, highly elastic
What is the function of the aorta & large arteries?
Distribution (conduit), handles high pressure reservoir, forward propulsion
How do arterioles contract & why?
- Contraction of the circular muscle of small arterioles permits regulation of tissue blood flow & helps to control arterial blood pressure
- Change from pulsatile (intermittent ejection from heart) to steady blood flow
What are the layers of the aorta & large arteries?
- Inner layer: Tunica intima
- Middle layer: Tunica media
- Outer layer: Tunica extrema
What is the tunica extrema (outer layer) made up of?
Collagen fibres
What is the tunica media (middle layer) made up of?
Smooth muscle cells & innervation
What is the tunica intima (inner layer) made up of?
Endothelium that lines the lumen of ALL vessels
What are the layers of the arterioles?
- Inner layer: Tunica intima
- Middle layer: Tunica media
- Outer layer: Tunica extrema
What is the structure of the arterioles?
Thick walled, muscular, highly innervated
What is the function of the arterioles?
Tissue distribution flow, variable resistance
Describe capillaries in general:
- Many capillaries arise from each arteriole
- Blood flow & velocity drop significantly across the capillary bed
- Walls are only one cell thick
What is the structure of capillaries?
Thin walled (single cell), lacking elastic tissue & smooth muscle
What is the function of the capillaries?
Exchange
What are the layers of the capillaries?
- Single layer: Endothelium - endothelium that lines the lumen of ALL vessels
- Lumen: very small (only large enough for 1 RBC to pass thru at a time)
Describe the venules & veins in general:
- On return to the heart from the capillaries, blood passes through venules & then veins
- Return blood back to the heart (venous return)
- Pressure decreases progressively until blood reaches heart
What are the layers of the venules & veins?
- Lumen = large lumen
- Valves = facilitate movement of blood back to heart
- Venous walls = thin layer of muscle & elastic tissue w thin outer layer
What is the structure of the venules & veins?
Thin walled, some muscle & innervation, valves (unidirectional)
What is the function of the venules & veins?
Reservour (capacitance); at rest approx 60% blood vol
Insert tabe of comparison of blood vessel anatomy
Thanks xx
Which blood vessel has the largest cross section?
The capillaries
What are the blood vessels with the largest diameters?
- Aorta > arteries > arterioles > capillaries
- Veins > venules > capillaries
What does the blood stream velocity depend on?
On the cross sectional area
‘River’ area:
- Area = 2cm^2
- Velocity = 5cm/s
‘Lake’ area:
- Area = 10cm^2
- Velocity = 1cm/s
Pls insert cross sectional area diagram here
Constant flow rate (CO) = ?
Constant flow rate (CO) = blood flow velocity X cross-sectional area
What are the determinants of blood flow (Q)?
- Flow Q refers to the vol of fluid that passes a given cross-section of the vessel per unit time
- Fluid velocity is inversely proportional to cross-sectional-area → the larger the area, the lower the velocity
What is the formula for flow rate?
Flow rate = volume / unit time
What is the formula for velocity?
Velocity = distance / unit time
What happens if flow rate is constant?
Velocity is inversely proportional to cross-section area
i.e. slowest capillaries
What are the factors that the relationship between pressure & flow (Q) depend on?
1 - Pressure = flow is proportional to the difference between inflow & outflow pressure (Pi - Po)
2 - Length = flow is inversely propotional to length of the vessel (L)
3 - Radius = flow is proportional to radius of the vessel (r^4)
4 - Viscosity = Flow inversely proportional to viscosity of the blood (ƞ)
What was the law proposed to do with pressure & flow
Poiseuille’s Law was proposed more than a century ago to help describe the factors that affect flow rate thru a conduit (vessel)
Pls insert the pressure & flow equation
Thanks x
Which blood vessel have the greatest capacity to change their radius?
Arterioles
They can therefore influence resistance
What us peripheral resistance’s relationship to pressure?
- In electrical theory, resistance = voltage drop/electrical current flow (R=V/I)
- In the vasculature, the equation for this is similar:
Resistance = Pressure difference / flow
R = Pi - Po / Q
