MODULE 2 Flashcards
What is the purpose of the cardiovascular system?
to provide adequate blood flow to all tissues/organs
The base of the heart is located… and is the…
near the anterior chest wall, entry and exit to the heart
The apex of the heart is located…
inferior tip, points towards the left hip, 12-14cm from base
The heart sits in a cavity called the
anterior mediastinum
Size of the heart
12-14cm long, 9cm wide
The pericardium is… and contains
a double walled sac, an outer parietal pericardium and an inner visceral pericardium/epicardium
3 layers of the heart wall are
epicardium, myocardium, endocardium
Epicardium
covers the heart (visceral pericardium)
Myocardium
the thickest layer, muscular wall consisting of cardiac muscle cells, blood vessels, nerves and connective tissue
Endocardium
endothelium (epithelium) covers the inner surfaces of the heart, including heart valves. Forms smooth inner lining which reduces friction so blood can move through easily
External structures of the heart: 2 superior atria that are…
thin-walled, receiving chambers, expandable regions called auricles, externally separated from ventricles by the coronary sulcus
External structures of the heart: 2 inferior ventricles that are…
thick-walled chambers, discharging chambers, externally separated from each other by an interventricular sulcus (anterior and posterior)
Right atria receives… from…
deoxygenated blood, from the superior vena cava, inferior vena cava and coronary sinus
Left atria receives… from…
oxygenated blood, from right and left pulmonary veins from the lungs
Pulmonary trunk
takes blood from the ventricles and delivers to the lungs for oxygen collection
Aorta/aortic arch
takes blood from the ventricles and delivers to the body (for oxygen delivery)
Internal structures of the heart: atria (right atrium)
the right atrium receives coronary blood (deoxygenated blood) from the superior and inferior venae carvae and coronary sinus
Internal structures of the heart: ventricles are…
separated from the atria via atrioventricular valves (AV) which are anchored via chordae tendinae attached to papillary muscles
Right (tricuspid valve)
Left (bicuspid/mitral valve)
Trabelculae carnae are
muscular ridges, less likely for walls to stick together, blood moves through easily
Blood exits the ventricles via
semilunar (SL) valves:
Right pulmonary semilunar valve
Left aortic semilunar valve
Right ventricle
thinner than the left as it does not have to work as hard (5mm thick)
Left ventricle
(15mm thick) thick muscles, generates 4-6 x more force than the right ventricle. Contracts from bottom (apex) upwards and constricts diameter. Pushes blood into the systemic circuit therefore requires a lot of force
Function of atrioventricular valves (AV)
prevent backflow of blood into the atria when ventricles contract. Chordae tendinae tense, via contraction of the papillary muscles, preventing the AV valves everting into the atria
Function of semilunar valves (SL)
pocket-like crescent shaped cusps, forced open when ventricles contract, close when ventricles relax and blood in the arteries tries to flow backwards
Valves open or close in response to
pressure changes
Valves ensure the
one-way flow of blood through the heart
When AV valves open:
atrial pressure > ventricular pressure. As ventricles contract and intraventricular pressure rises, blood is pushed up against SL valves, forcing them to open.
Sequence of events once AV valves open
- blood returning to the heart fills the atria, putting pressure against AV valves, AV valves are forced open. 2. as ventricles fill, AV valve flaps limply into ventricles. 3. atria contract, forcing additional blood into ventricles
When AV valves close:
atrial pressure < ventricular pressure. As ventricles relax and intraventricular pressure falls, blood flows back from arteries, filling the cusps of SL valves and forcing them to close.
Sequence of events once AV valves close
- ventricles contract, forcing blood against AV valve cusps. 2. AV valves close. 3. papillary muscles contract, and chordae tendinae tighten, preventing valve flaps from everting into atria.
What is coronary circulation?
coronary circulation supplies blood to he myocardium. Left and right coronary arteries arise from the base of the aorta and circle the heart in the coronary sulcus.
Coronary circulation: left coronary artery gives rise to…
the anterior inter-ventricular artery - supplies anterior ventricles
Coronary circulation: right coronary artery gives rise to…
the posterior inter-ventricular artery - supplies posterior ventricles
Blood moves into the coronary arteries when…
the ventricles relax and blood in the aorta attempts to move backwards towards the heart i.e. in between heart beats
Function of the great cardiac vein
drains the anterior regions supplies by the anterior inter-ventricular artery
Function of the middle cardiac vein
drains the posterior regions supplies by the posterior inter-ventricular artery
All veins drain into the…
coronary sinus (then drains into the right atrium)
Coronary artery disease: angina pectoris
temporary deficiency in myocardial blood supply (narrowed coronary vessels). Characterised by thoracic pain, myocardial cells weaken but do not die
Coronary artery disease: myocardial infarction
prolonged coronary artery blockage, ischaemic myocardial cell death. Myocardium is replaced by non-contractile scar tissue (weakens heart). Left ventricle damage most serious
Left side of the heart is what type of pump
systemic pump
Right side of heart is what type of pump
pulmonary pump
Blood always moves down a pressure gradient from an area of
high pressure to low pressure
The pulmonary circuit is supplied by
the right ventricle. Short, low pressure circulation
The systemic circuit is supplied by
the left ventricle. Long, high pressure circulation. Encounters 5 x more resistance to blood flow as the pulmonary circuit
Summary of blood flow through the heart:
Superior vena cava, inferior vena cava, coronary sinus - right atrium - right AV valve - right ventricle - pulmonary SL valve - pulmonary trunk - lungs - left atrium - left AV valve - left ventricle - aortic SL valves
The myocardium includes cardiac…
pacemaker cells (auto rhythmic cells)
Pacemaker cells have an
unstable resting membrane potential, and continually depolarise to generate action potentials
5 components of the intrinsic conduction system:
- sinoatrial node 2. atrioventricular node 3. atrioventricular bundle 4. bundle branches 5. purkinje fibres
Sinoatrial node
right atrial wall, inferior to entry point of superior vena cava, depolarises the fastest. Acts as a pacemaker and determines heart rate
Atrioventricular node
at the junction between the atria and the ventricles
Atrioventricular bundle
aka bundle of His, in the upper interventricular septum, only electrical connection between the atria and ventricles
Bundle branches
travel in the interventricular septum to the apex
Purkinje fibres
subendothelial conducting network, penetrate ventricle walls, depolarise ventricular myodcardium
What is extrinsic innervation
ANS modifies the activity of the heart
2 functions of the cardiac centres in the medulla oblongata:
- cardioacceleratory centre increases heart rate and force of contraction (dilation) 2. cardioinhibitory centre decreases heart rate
What is electrocardiography?
cardiac electrical events can be detected (action potentials)
What is an electrocardiogram?
a graphic record of heart activity
P wave
depolarisation of the atria, beginning at the SA node
QRS complex
depolarisation of the ventricles, atrial repolarisation is masked by this complex
T wave
repolarisation of the ventricles
ECG order of events
- atrial depolarisation causes the P wave 2. the impulse is delayed at the AV node 3. ventricular depolarisation, begins at the apex and causes the QRS complex 4. ventricular depolarisation is complete 5. ventricular repolarisation begins at apex, causing the T wave 5. ventricular repolarisation is complete
Systole
periods of contraction
Diastole
periods of relaxation (in between heart beats)
Atrial systole
atria contract, completely filling the relaxed ventricles with blood
Ventricular systole begins (first phase)
ventricular contraction beginning at the apex, pushing blood upwards and closes the AV valves but pressure not great enough to open SL valves = isovolumetric contraction (no change in ventricular blood volume)
Ventricular systole begins (second phase)
ventricular pressure increases, forcing SL valves open and pushing blood out of the ventricles = ventricular ejection
Ventricular diastole (early)
as the ventricles relax, arterial blood flows backwards and closes the SL valves
Isovolumetric relaxation (no change in ventricular blood volume)
blood flows into the relaxed atria but the AV valves remain closed
Ventricular diastole (late)
all heart chambers are relaxed, the AV valves are open, blood moves passively from the atria to the ventricles to 70% of their final volume
When heart rate increases all phases are..
shortened (less time for passive filling)
Auscultation
listening to body sounds
Heart beat (S1 and S2) =
“lubb-dupp”
Lubb =
closure of the AV valves
Dupp =
closure of the SL valves
Heart murmur
swishing sound as blood backflows through an incompetent valve
Aortic valve
sounds heard in 2nd intercostal space at right sternal margin
Pulmonary valve
sounds heard in 2nd intercostal space at left sternal margin
Mitral valve
sounds heard over apex in line with middle clavicle
Tricuspid valve
sounds typically heard in right sternal margin of 5th intercostal space
Electrical + Mechanical Events
P wave = atrial depolarisation = atrial systole
QRS complex = ventricular depolarisation = ventricular systole
T wave = ventricular repolarisation = ventricular diastole
Cardiac output is
the volume of blood pumped (into the systemic circuit) by the left or right ventricle in one minute
Cardiac output formula
SV x HR
Stroke volume is
volume of blood ejected from the left or right ventricle per beat (mL)
End diastolic volume (EDV)
the volume of blood in a ventricle at the end of its relaxation period (just before it contracts)
End systolic volume (ESV)
the volume of blood remaining in the ventricles after it has contracted
Stroke volume =
EDV - ESV
EDV is determined by…
- venous return (the amount of blood returning to the heart from systemic or pulmonary circuits 2. passive filling time (time both the atria and ventricles are in diastole 3. contractility (amount of force produced during a contraction
Contractility
amount of force produced during a contraction. Greater contractility = higher SV = lower ESV = higher CO
EDV is increased by…
sympathetic stimulation of ventricular myocardium, hormones, high levels of extracellular calcium, exercise
EDV is decreased by…
acidosis (low ECF pH) and increased extracellular K+ levels
Preload =
the degree the myocardium is stretched before it contracts = determines force of ventricular myocardial contraction = determines SV
Afterload (ESV) =
the pressure that the ventricles must overcome to open the semilunar valves to eject blood into the arteries
Bradycardia is
a condition in which the heart rate is slower than normal
Tachycardia is
a condition in which the heart rate is faster than normal
