heart anatomy and physiology Flashcards
where is the sinoatrial node located?
in the posterior wall of the right atrium
what does the moderator band do?
conducts the impulse from the bundle branches to the anterior papillary muscle of the right ventricle
what does the QRS complex on an ECG represent?
ventricular depolarisation
trace the path of an action potential through the conducting system
sinoatrial node → internodal pathways → atrioventricular node → AV bundle → bundle branches → purkinje fibres
where is the heart positioned in the body?
posterior to the sternum, in the mediastinum between the two pleural cavities, in the pericardial sac
what is the role of connective tissue fibres in the epicardium?
physical support
distributes contractile forces
prevents overexpansion
elasticity - helps heart return to its original size and shape
how long does the cardiac cycle last?
about 0.8 seconds
what are three ways to diagnose MI?
ECG
troponin levels (Tn I) - more troponin, more damage
creatine kinase (non specific)
what are the symptoms of MI?
severe, prolonged, crushing pain dyspnoea cool, clammy skin sweating pallor
what is the difference between STEMI and non STEMI MIs?
STEMI - complete blockage of coronary artery
non STEMI - partial obstruction - tissue damage not as bad
what is the formula for measuring BMI?
weight divided by (height squared)
where is the atrioventricular node located?
in the floor of the right atrium, near the septum
what is the left AV valve also know as?
bicuspid valve or mitral valve
what is isovolumetric contraction?
all valves are closed, ventricles contracting (same volume).
like squeezing a bottle with the lid on - pressure increases, but volume remains the same
what are the two types of cardiac muscle cell and what do they do?
conducting system cells: control and coordinate the heartbeat
contractile cells: produce contraction that propel blood
what do width and height equal on an ECG?
height equals voltage
width equals time
what effect would an increase in venous return have on stroke volume?
increased venous return = more stretch in heart muscle = greater force of contraction = higher stroke volume
what effect would an increase in sympathetic stimulation of the heart have on end-systolic volume?
increased heart rate and increased force of contraction leads to higher stroke volume = lower end-systolic volume
define end-diastolic volume (EDV) and end-systolic volume (ESV)
EDV - amount of blood in left in the ventricle at the end of relaxation
ESV - amount of blood left in the ventricle at the end of contraction
list the phases of the cardiac cycle
atrial systole
atrial diastole
ventricular systole
ventricular diastole
what is stroke volume?
what is it measured in
the amount of blood that leaves the heart with each beat
ml/beat
which blood vessels supply the heart with oxygenated blood?
coronary arteries
describe the pericardium
pericardial sac - visceral and parietal layers with pericardial cavity containing pericardial fluid in between
serous membrane!
what are the characteristics of cardiac muscle cells?
small
branched
single nucleus
intercalated discs
