The Cardiovascular System Flashcards
What are the two components of the CV system?
Pulmonary & systemic
What are the major functions of the CV system?
1) Transport oxygen & remove carbon dioxide
2) Transport nutrients & remove wastes
3) Fight disease
4) Transport hormones
5) Regulate body temperature
Where do the right and left pumps of the heart pump blood?
Right: Lungs
Left: Through peripheral organs
Where do the atria and ventricles pump blood?
Atria: Into the ventricles
Ventricles: Into circulation
What is the pulmonary pathway of blood through the heart?
Systemic veins - right atrium - right ventricle - pulmonary artery - lungs
What is the systemic pathway of blood through the heart?
Lungs - pulmonary vein - left atrium - left ventricle - systemic arteries
What are the three types of cardiac muscle?
Atrial, ventricular and excitatory/conductive
What do cardiac muscle cells form and what does it allow?
A syncytium, allowing synchronised contraction
How many syncytia is the heart composed of and what are they separated by?
Two; fibrous tissue
What do the syncytia of the heart allow?
The atria to contract before the ventricles
What are the two types of heart valves?
Atrioventricular and semilunar
What are the two types of atrioventricular valves?
Tricuspid & mitral
What do the atrioventricular valves prevent?
Backflow from the ventricles into the atria during systole
How do the atrioventricular valves attach?
To papillary muscles by the chordae tendineae
What are the two types of semilunar valves?
Aortic & pulmonary
What do the semilunar valves prevent?
Backflow into the ventricles during diastole
What are the semilunar valves constructed of?
Stong, flexible fibrous tisse
How does left ventricle contraction affect aortic pressure?
Causes pressure increases until the aortic valve opens, which then causes pressure increases in the aorta (80mmHg - 120mmHg)
What happens when the aortic valve closes?
Blood flows from arteries into periphery as the arteries return to their previous size, pressure returns to 80mmHg
What is the cardiac cycle?
Beginning of one heart beat to the beginning of the next
What is the cardiac cycle initiated by?
Action potential of the sinus node
Which occurs first, atrial or ventricle systole?
Atrial
What volume of blood is pumped at rest?
4-6 litres
By how much does the volume of blood pumped increase during strenuous exercise?
4-7x
What are the two major mechanisms of regulation for heart pumping?
Intrinsic regulation & control by the autonomic nervous system
What are two other mechanisms of regulation for heart pumping?
Potassium/calcium ions & temperature
What is intrinsic regulation also known as?
The Frank-Starling mechanism
What is the amount of blood pumped out of the heart normally determined by?
The rate of blood flow into the heart (venous return)
What happens when more cardiac muscle is stretched during filling?
Greater contraction strength & volume of blood expelled
What system of nerves is the main controller of the heart?
The specialised excitatory and conductive system
What is the specialised excitatory and conductive system made up of?
- Sinus node
- Internodal pathways
- Atrioventricular node
- AV bundle
- Left & right branches of Purkinje fibres
What occurs during normal conditions for control of the heart by nerves?
Continuous low-level sympathetic stimulation
What does increasing sympathetic stimulation do?
Increase both rate and force of contractions
What nerve is associated with parasympathetic stimulation of the heart and what does it achieve?
Vagus nerve; slowing of heart rate
True or false: Increased arterial pressure has little effect on cardiac output in normal ranges
True
What is cardiac output tied to?
Blood flow through the body and hence venous return
What is an electrocardiogram?
A recording of the electrical potentials generated by the heart
What does the P wave, QRS complex and T wave represent?
P wave: Atrial depolarisation
QRS complex: Ventricle depolarisation
T wave: Repolarisation
What is a cardiac arrhythmia?
An abnormal rhythm of the heart
What are the causes of cardiac arrhythmias?
Pacemaker abnormality, shift of the pacemaker, blockage of nervous impulse, abnormal pathways, spontaneous generation of false impulses
What percentage of circulation is systemic?
84%
What percentage of circulation is pulmonary?
9%
What is systemic circulation also known as?
Peripheral circulation of greater circulation
What vessels have the largest total cross-sectional area of the circulation?
Capillaries
What is the formula for velocity of blood flow?
Velocity of blood flow = blood flow/cross sectional area
Where is velocity of blood flow greatest?
Aorta
What vessels hold the majority of blood volume?
Veins (64%)
In what areas of the circulatory system are there high pressures, low pressures and a large pressure drop?
High pressures: Arterial tree (aorta, arteries, arterioles)
Low pressures: Venous system
Large pressure drop: Arteriolar-capillary junction
What is blood flow to tissues controlled in relation to?
Tissue needs, by dilation/constriction, CNS and hormones
What is cardiac output controlled by?
Local tissue flow, with help from nerve signals
Arterial pressure is controlled independent of __?
Local blood flow control or cardiac output control
What is arterial pressure controlled by?
Nervous reflexes
What is blood flow?
The quantity of blood that passes a given point in the circulation in a given period of time
How is a unit of blood flow usually expressed?
Volume/time (usually mL/min or L/min)
What is the overall flow in the circulation (cardiac output) of an adult?
5 litres
What is laminar flow?
Blood flows in streamlines with each layer of blood remaining the same distance from the wall
What happens when laminar flow occurs and what does it create?
Velocity of blood in the centre of the vessel is greater than that toward the outer-edge; creates a parabolic profile
What are the causes of turbulent flow?
High velocities, sharp turns in circulation, rough surfaces and rapid narrowing of the blood vessels
Laminar flow is silent, whereas turbulent flow tends to cause __?
Murmurs
What are murmurs, or bruits, important in diagnosing?
Vessel stenosis, vessel shunts and cardiac valvular lesions
What does turbulent flow increase?
Wall stress
What is blood pressure?
The force exerted by the blood against any unit area of vessel wall
What is blood pressure measured in?
mmHg
Which vessel walls are stronger, arteries or veins?
Veins
What is vascular distensibility?
The fractional increase in volume for each mmHg rise in pressure
What is vascular capacitance?
The total quantity of blood that can be stored in a given portion of the circulation for each mmHg
What is the formula for capacitance?
Capacitance = volume x distensibility
What happens when veins are constricted?
Large quantities of blood are transferred to the heart, increasing cardiac output
What is central venous pressure and what is it determined by?
Pressure in the right atrium; determined by the balance of the heart pumping blood out of the right atrium and the flow of blood from the large veins into the right atrium
What factors increase right atrial pressure?
- Increased blood volume
- Increased venous tone/pressure
- Dilation of arterioles
- Decreased cardiac function
What doe increases in right atrial pressure cause?
Blood to back up into the venous system, increasing venous pressure
What factors cause resistance to flow in large peripheral veins?
Compressional factors, e.g. blood vessel turning near a bone
Where can venous pressure become negative and why?
In the dural sinuses, because the skull cavity prevents vein collapse
What is the function of venous valves?
Ensure blood only flows towards the heart & reduce venous pressure in the lower limbs
How can venous valves become damaged and what does it result in?
Due to over stretching from excess venous pressure, as valves cannot expand. Results in further increases in venous pressure
What organs/vessels serve as blood reservoirs?
Spleen, liver, large abdominal veins and venous plexus
What two changes lead to increases in blood flow?
Increases in tissue metabolism & decreases in oxygen availability
What are the two major theories of local blood flow?
The vasodilator theory & the oxygen demand theory
What is the function of the lymphatic system?
Provide an accessory route for interstitial fluid & destroy bacteria