Week 4 (cardiovascular system) Flashcards
What is the heart?
A pump that provides continuous linkage with the vascular components.
What is the arterial system?
A high-pressure distribution circuit
What are the capillaries?
Exchange vessels
What is the venous system?
A low pressure collection and return circuit
What is blood?
A body fluid that transports essential substances and metabolic waste products.
Name the layers of the heart
Pericardium
Epicardium
Myocardium
Endocardium
Describe the pericardium
Membrane that surrounds and protects the heart
Describe the epicardium
External layer composed of fibroelastic and adipose tissue and contains blood vessels, lymphatic and nerves that supply the myocardium.
Describe the myocardium
Middle layer composed of cardiac muscle tissue.
Describe the endocardium
Innermost layer of endothelium overlying thin layer of connective tissue.
What are the atria?
Two superior chambers receiving chambers
What are the ventricles?
Two inferior pumping chambers
What does the intraventricular septum do?
Separates the right and left sides
What do the atrioventricular valves do?
(Tricuspid and bicuspid)
Ensure one-way blood flow between the atria and ventricle.
What is the pulmonary circulation?
The right side which receives deoxygenated blood from the body (via the vena cava) and pumps blood to the lungs.
What is the systemic circulation?
The left side which receives oxygenated blood from the lungs (via the pulmonary vein) and pumps blood into the aorta for distribution throughout the body.
What is coronary circulation?
The myocardium’s own network of blood vessels.
What do the coronary arteries do?
Deliver oxygen and nutrients to the heart muscle and collects carbon dioxide and waste, and then moves into coronary veins.
What do arterioles do?
Control blood flow and feed capillaries.
Describe capillaries
Exchange vessels
Single layer of endothelium cells
500-2000 capillaries per mm2 of skeletal muscle tissue
Large surface area + slow rate of BF = effective oxygen and carbon dioxide exchange.
What is a precapillary sphincter?
A band of smooth muscle that adjusts blood flow into capillaries.
Name the layers of blood vessels
Tunica intima (inner lining)
Tunic media (middle layer)
Tunica adventitia (outer covering)
Describe the tunica intima (inner lining)
Epithelial lining consisting of endothelial cells lining the lumen of the vessel, and a connective tissue.
Describe the tunica media (middle layer)
Smooth muscle and elastic connective tissue.
Primary role is to regulate the diameter of the lumen.
Middle layer helps to distinguish between the different types of vessels.
Describe the tunica adventitia (outer covering)
Connective tissue mainly collagen fibres.
Contains nerves and small blood vessels.
Describe the pathway of cardiac impulse transmission
SA node
Atria
AV node
AV bundle
Purkinjean fibres
Ventricles
What is the cardiac cycle?
A period from the beginning of one heart beat to the beginning of the next one.
It can be split into two basic phases; diastole and systole.
What happens in diastole?
Heart muscles relax.
Blood fills the chambers.
At rest the heart spends tow thirds of its time in diastole.
What happens in systole?
Heart muscle contracts.
Blood is pumped out of the chambers.
At rest the heart spends one third of its time in systole
What is venous return?
The total blood volume returning to the heart by vena cava into the atria.
What is ventricular end diastolic volume (EDV)?
The total blood volume in each ventricle at the end of diastole.
What is ventricular end systolic volume (ESV)?
The total blood volume in each ventricle at the end of systole (ejection)
What is stroke volume?
The blood volume ejected per beat from each ventricle.
What is the equation for ejection fraction?
Stroke volume / end diastolic volume
What is blood pressure?
The pulsatile force exerted by blood pushing against the walls of the arteries as the heart pumps blood.
What is systolic pressure?
Highest pressure in an artery during ventricular contraction.
What is diastolic pressure?
Lowest pressure in artery during ventricular relaxation.
What is mean arterial pressure?
The average pressure over an entire cardiac cycle.
What values does the resting BP fluctuate between in the aorta and large arteries?
120 systolic
80 diastolic
What is the equation for blood flow?
Perfusion pressure / resistance
What is perfusion pressure?
Pressure differences drives blood flow.
Flows from regions of higher (aorta) to lower (vena cava) pressure.
What is resistance?
The force that opposes blood flow.
Dependent on blood viscosity, vessel length and radius.
Resistance = (blood viscosity x vessel length) / radius
What is the equation for mean arterial blood pressure?
Flow x resistance
Describe the intrinsic regulation of heart activity.
Cardiac muscle has ‘spontaneous rhythmicity. This allows it to contract without external.
Describe the extrinsic regulation of heart activity.
Neural via ANS.
Hormones via endocrine system
Describe the activation of the parasympathetic nervous system.
Stimulates the release of acetylcholine from the Vagus nerve.
Binds to muscarinic receptors on cardiac cells.
Causes hyperpolarisation of cells in SA and AV node which decreases heart rate.
At rest, PNS activity predominates (heart under ‘vagal’ tone).
An increase of vagal tone = slows HR = bradycardia.
A decrease of vagal tone = increases HR = tachycardia.
As exercise begins there is a decrease in PNS activity.
Describe the activation of the sympathetic nervous system
Stimulates the release of catecholamines.
Noradrenaline is released from sympathetic fibres/cardiac accelerator nerves.
Adrenaline is released from the adrenal gland.
Activates adrenoceptors in the cardiac cells.
Increases heart rate and increases force of ventricles contraction.
The SNS predominates during stress when heart >100bpm.
What is the equation for cardiac output?
Heart rate x stroke volume
Describe the local regulation of blood pressure/flow
The ability of local blood vessels to dilate/constrict altering regional BF depending on metabolic needs of the tissue.
Describe the systemic regulation of blood pressure and flow.
Short term: redistribution of systemic blood flow is controlled by neural mechanisms and hormones.
Long term: changes in blood volume and blood pressure regulated by hormones.
How is blood flow distributed to where it is needed?
Via local vasodilation
What is metabolic regulation?
Build up of local metabolic products stimulate VSM vasodilation.
What is endothelium mediated vasodilation?
Vasodilators produced by the endothelium stimulate VSM vasodilation.
What is the resting heart rate for;
a. general population
b. unconditioned population
c. elite athletes
a. 60-80bpm
b. >100bpm
c. <40bpm
Why is pre-exercise HR not a reliable estimate of resting HR?
Anticipatory rise
Adrenaline and noradrenaline
Withdrawal of vagal tone
Describe the heart rates response to exercise
HR increases in proportion to exercise intensity, and is triggered by withdrawal of vagal tone and the stimulation of SNS.
How do you calculate maximum heart rate?
220 - age
What causes maximum heart to decrease by 1 beat per year?
Reduced medullary outflow of sympathetic activity.
What happens to heart rate as a result of endurance training?
Lower resting heart rate
Lower heart rate response to submaximal exercise.
Lower myocardial oxygen demand.
Unchanged maximum heart rate.
Describe stroke volume response to exercise
Higher preload at lower intensities due to increased venous return due to skeletal and respiratory pump.
Increased contractility at higher intensities due to increased SNS activation.
Lowe afterload due to systemic vasodilation.
SV plateaus due to increased heart rate.
Describe the changes of stroke volume as a result of training
Increases at rest and at exercise.
Describe blood flow’s response to exercise
Increased cardiac output which increases the available blood flow.
