cardiovascular systems, circulatory system, heart Flashcards
what does the cardiovascular system consist of (3 things)
blood
heart
circulatory system
what are the 2 main function of the cardiovascular system
delivers gases, nutrients, and hormones to the cells and tissues
the circulatory system is made up of 3 parts what are they
pulmonary circulation (heart and lungs) systemic circulation (rest of the body) lymphatic circulation
the arteries/vessels carry blood which way in relation to the heart
blood travels away from the heart in the arteries and returns to the heart in the veins
what are arteries and veins connected by
capillaries (site of gas/nutrient exchange)
in systemic circulation, blood rich in oxygen comes from which side of the heart
left
heart is described from the point of view of the individual - not an onlooker
is the systemic circulation considered high or low pressure
high
what is there instead of a carotid vein
jugular
draw arterial/venous system
draw it
in the pulmonary circulatory system, blood low in oxygen travels from which side of the heart to the lungs
right
is the pulmonary circulatory system considered high or low pressure
low
blood vessels must…3 things
endure changes in pressure
move with surrounding structures
remain open under all conditions
blood vessels have 3 layers what are they from outside in
tunica externa (connective tissue) tunica media (muscle) tunica intima (endothelium)
blood vessel structure is modified according to function, what are the what are the five types
arteries (elastic and muscular) arterioles capillaries (continuous and fenestrated) venules veins
what are the 5 differences between arteries and veins
arteries have thicker walls arteries appear to have a smaller lumen arteries maintain their shape arteries are more resilient than a vein arteries do not contain valves - veins contain many valves
what are the features of elastic arteries and name 3
thick tunica media (muscle) with many elastic fibres
aorta, brachiocephalic, common carotid
what are the features of muscular arteries, what do they do and where are they found
lots of tunica media and think tunica externa
distribute blood to muscles and organs
most arteries are muscular arteries
what happens in capillaries and what is their structure
site of gaseous, nutrient and waste exchange thin walled (can be continuous fenestrated or sinusoid) found in skin, gonads, glomerulus, intestines, pancreas...
what is a capillary bed
10 - 100 capillaries supplied by a single metarteriole ( is a short vessel that links arterioles and venules)
have precapillary sphincters to control flow to individual beds
what are arteriovenous anastomoses
form direct communication between the arteiole and venule
serve as backup routes for blood to flow if one link is blocked or otherwise compromised
what do venules do
collect blood from the capillary beds and deliver it to small veins
what do veins (capacitance vessels) do and what is their structure
return deoxygenated blood to the heart
low pressure, thin walled, easily distensible
what 3 things does the lymphatic system consist of and what are its functions
a network of lymph vessels
lymph - fluid
lymphatic tissues and organs
functions: involved in the body’s defence mechanisms and provides a mechanism for the drainage of interstitial fluid (solution that bathes and surrounds the cells)
how does fluid move out of the lymphatic circulatory system
what is left behind
fluid moves into the interstitial space at the arterial end of the capillary (high pressure)
fluid moves back into the capillary at the b=venous end (low pressure)
15% of lymph is left which is then returned to the blood
what are lymph capillaries and where are they located
blind ended tubes what are located adjacent to capillary beds
what are the 2 lymphatic ducts called, what parts of the body do they drain and where does it empty into
Right lymphatic duct (right side of head and thorax and right upper limb) empties into right subclavian vein
Thoracic duct (remainder of the body) empties into left subclavian vein
lymph re-enters what
the blood vascular circulation
where is the heart located and what is it protected by
in the thorax between the lungs
protected by the ribs and the sternum (breastbone)
what is the pericardium
2 parts Fiberous pericardium (outer) - an inelastic sac of dense connective tissue that wraps around the heart which prevents overfilling
Serous pericardium - (inner) two layers parietal and visceral separated by pericardial cavity which contains serous fluid and prevents friction
what are the 3 layers of the heart wall from the outside in
epicarduim (visceral pericardium)
myocardium (muscle)
endocardium (endothelium)
draw the general organisation of the heart
draw it -NOT DRAWN!
draw the anterior view of the heart
draw it
draw the internal view of the heart
draw it
why does the fiberous connective tissue separate the artia from the ventricles
to create a pause
draw the heart valves
draw it - NOT PRINTED!
how are atrioventricular valves opened
by blood flowing from the atria to the ventricles
what prevents eversion (opposite of invert) of the valves during ventricular contraction
tendon anchorage to papillary muscles - prevent backflow
what initiates electrical impulses within the heart
non-contractile cells
what does the SA node do
sets the rhythm
what happens to the impulse
impulse spreads throughout atria and the remainder of the heart via the cardiac conductive system
what modifies the rate
the ANS (autonomic nervous system)
what does an electrocardiogram (ECG) do
records the spread of electrical activity through the heart muscle
what are the ECG waves
P wave - depolarisation of the atria
QRS complex - depolarisation of the ventricles
T wave - repolarisation of the ventricles
-NO repolarisation of atria!!!
why is the foetal circulation different from the adult
1) oxygen and nutrients received from the placenta via umbilical vein
2) need to bypass non functional lungs
3) circulatory shortcuts
- ductus venosus connects the umbilical vein to the inferior vena cava
- Foramen ovale connects right and left atria
- Ductus arteriosus connects pulmonary artery to arch of aorta
what is the function of the semilunar valves
opened by blood being pushed out of ventricles
blood flows backwards in the aorta and pulmonary trunk during ventricular relaxation - this pools in the cusps and pushes them shut - prevents backflow
NO chordae tendinae
why is blood delivered to myocardium (heart muscle) during ventricular relaxation
because don’t want blood to enter when muscles contracted
how much blood does the heart receive per min
250 ml/min
where do most cardiac veins drain into
the coronary sinus which empties into the right atrium
the anterior cardiac veins drain directly into the right atrium
what is an angiogram
determines whether there is a blockage in the coronary arteries - blockage can lead to myocardinal infarction and angina
what are the properties of cardiac muscle
1) branching network of cells
2) cells are interconnected by intercalated discs which contain gap junctions
3) gap junctions allow ion transport between cells which promotes coordinated contraction
cardiac cells are functional syncytium - what does this mean
A functional syncytium in a heart refers to a single cell or cytoplasmic mass comprising of several nuclei that have been created as a result of fusion of cells or through division of nuclei. The cells are then connected mechanically, chemically and electrically and hence called functional
cardiac muscle is autorhythmic - what does this mean
generates its own rhythmic action potentials
what happens to the lungs at birth
they expand - resistance in the pulmonary circuit falls
what happens to the ductus arteriousus
it closes
what happens to umbilical vessels
they close
the 3 changes to the circulatory system at birth mean that pressure…
what does this lead to
pressure rises in systematic circulation and the left side of the heart
pressure falls in pulmonary circulation and right side of the heart
which leads to closure of the foramen ovale (fossa ovale)
what are the 5 events that occur during 1 heart beat
1) ventricular filling - passive
2) ventricular filling - atrial sysole
3) isovolumetric contraction - the ventricles contract with no corresponding volume change
4) ventricular ejection
5) isovolumetric relaxion - an interval in the cardiac cycle
what is the sound of the heart beating
the valves closing
what happens during ventricular filling (passive)
atria and ventricles are relaxed
AV valves open - blood returning back to heart
semilunar valves closed
blood flows into atria, through open AV valve into ventricles
what happens during ventricular filling (atrial systole) forcing of remaining blood
Atria contracts and force blood into ventricles (P Wave on ECG )
*At the end of this phase the end diastole is around 130ml in each ventricle
what 4 things happen during isovolumetric contraction
(QRS wave on ECG) Atria relax and ventricles contract pressure in ventricle rises semilunar valves remain closed AV valves close (first heart sound - lubb)
*volume in ventricle unchanged - around 130ml in each ventricle
what 2 things happens during ventricular ejection
1) ventricular pressure exceeds aortic and pulmonary pressure forcing semilunar valves open
2) blood is forced into aorta and pulmonary trunk
- at the end of this phase the end systolic volume is around 60ml
In this example how would you work out the stroke volume
130mls - 60mls = 70 (stroke volume)
what happens during isovolumetric relaxation
(T Wave on ECG)
1) Ventricles relax
2) semilunar valves close (seconds heartbeat sounds (dub)
3) AV valves remain closed
- volume in ventricle unchanged - around 60mls
what happens after isovolumetric relaxation
back to the beginning of the cycle (AV valves re-open and cycle begins again)
how do you measure cardiac output
Stroke volume x Heart rate
eg 70ml/beat (Stroke volume) x 75 beats/min (Heart rate) = 5, 250 ml/min Cardiac Output
what is stroke volume
volume of blood ejected per beat
what 3 factors affect stroke volume
1) degree of stretch of myocytes (preload) the more they stretch the more forcefully they contract - Starlings Law of the Heart
2) Forcefulness of contraction (contractility) regardless of stretch
3) pressure required to eject blood (afterload) the pressure in the left ventricle must be higher than that in the aorta in order for the aortic valve to be opened (similarly the pressure in the right ventricle must be greater than in the pulmonary trunk)
what is preload (degree of stretch of myocytes) determined by
End Diastolic Volume (EDV)
what is End Diastolic Volume (EDV) determined by
Venous Return (rate of blood flow back to the heart)
what is VR determined by
volume of circulating blood
e.g pressure gradient between veins and heart, respiratory pump, skeletal muscle pump, gravity
what can forcefulness of contraction be increased by
norepinephrine and epinephrine (SNS)
hypercalcaemia (high calcium levels)
what can forcefulness of contraction be decreased by
hyperkalaemia (high potassium)
hypocalcaemia (low calcium)
myocardial hypoxia (low oxygen)
myocardinal hypercapnia (elevated carbon dioxide)
Heart rate (pulse) varies across ages. what is a babies resting HR and an Adults
baby - 120bpm
adult - 64-80 bpm
what is tachycardia
high HR (above 100bpm)
what is bradycardia
low HR (below 60bpm)
SA node fires spontaneously at 100 bpm but rate is modified by what
cardiac centre of medular oblongata ( the lower half of the brainstem)
what are the 2 parts of the cardiac centre
cardioaccelarator centre: sends sympathetic impules to increase rate of firing at SA node (also stimulates cardiac muscle to increase force of contraction)
cardioinhibitory centre: sends parasympathetic impulses (via vagus nerve_ to decrease rate of firing at SA node
what is the vagal tone
Vagal tone is an internal biological process referring to the activity of the vagus nerve. PNS (peripheral nervous system) activity maintains HR at approx. 70-80 bpm
what is blood pressure
the force that the blood exterts on the walls of the blood vessels
what is systolic BP
maximum pressure when ventricles contract - approx. 120mmHg
what is diastolic BP
maximum pressure when ventricles relax - approx 80mmHg
what is pulse pressure
Systolic blood pressure - diastolic blood pressure
what is mean arterial pressure
diastolic blood pressure + one third of pulse pressure
what is hypertension
Chronically high blood pressure - above 140/90mmHg
what is hypotension
Blood pressure chronically low
how do you measure blood pressure
blood pressure = cardiac output (stroke volume, HR) x Total peripheral resistance (TPR - pressure (average) in all blood vessels
what is the only thing that can change TPR
vessel radius (determined by the sympathetic nervous system)
what maintains the blood vessels in a state of partial vasoconstriction known as sympathetic tone
the SNS (somatic nervous system). Controlled by the vasomotor centre in the medulla oblongata
increased SNS activity = vasoconstriction
decreased SNS activity = vasodilation
blood pressure is controlled by 3 mechanisms - what are they
1) local control - tissues can regulate their own blood supply.
2) neural (short term)
3) hormonal (long term)
what can cause local vasodilation and local vasoconstriction
Hypoxia, CO2, lactic acid - stimulate vasodilation
Histamine, bradykinins, prostaglandins - stimulate vasoconstriction
how does neural control control BP short term (3 centres)
baroreceptors in carotid and aortic sinuses constantly monitor blood pressure
Vasomotor centre: SNS - vasoconstriction to increase TPR (total peripheral resistance)
Cardiac accelerator centre: SNS - increases HR and force of contraction
Cardiac Inhibitor Centre: PNS - decreases HR
How does the body lower BP should it increase (3 stages)
1) increased BP - increased firing rate to cardiac and vasomotor centres
2) stimulates cardioinhibitory centre - increased PNS activity to SA node - decreased HR
3) inhibits cardioaccelorator and vasomotor centres - decrease SNS activity - decreases HR and vasodilation
what is venous pooling
Venous Pooling is also called as Venous distension. It is the distension
on the venous side of circuit due to the difference of the resistance and
the fluid volume within each vessels
Pulmonary vein oxygenated or deoxygenated
Oxygenated-exception to the rule
