Cardiovascular Flashcards
overview of conducting system; describe route of AP
- SA node (atria)
- AV node
- Bundle of His
- Purkinje fibres (wall of ventricles)
where is the AV node?
anterior to coronary sinus (R atrium)
where is the SA node?
wall of R atrium; inf. to opening of sup vena cava
name of cells which form the pacemaker?
autorhythmic cells
which has a higher Na+ concentration; intracellular or extracellular?
extracellular
what is a funny current, and what effect on the resting membrane potential?
- leakage of Na+ into the cell
- inhibits K+ from leaving
- causes increase in RMP = -40mM
- triggers AP
what ion channel is opened in response to an AP?
slow L-type Ca2+
3 steps in cardiac myocyte AP
- depolarisation
- plataeu phase
- repolarisation
what is a refractory period?
time where another AP cannot be fired
2 advantages of the refractory period?
- non-return valve; prevent AP from backflowing
2. prevents 2nd contraction before 1st contraction has ended (tetanic contraction)
disadvantage to a tetanic contraction
produces long, slow muscular contractions - dont allow heart to pump sufficiently.
what is hyperpolarisation?
overshoot in repolarisation - more negative than -90mV
P wave:
depolarisation of atria
QRS complex
depolarisation of ventricles
T wave
repolarisation of ventricles
PQ segment
conduction time between SA node + ventricular depolarisation
where is the plateau phase
ST segment
ECG: ventricular systole
QT wave
where on ECG is the ventricular diastole
after T wave
why is there a delay at the AV node?
allows ventricles to fill
2 points on ECG where ventricular pressure increases?
- P wave = as atria pump blood into ventricles
2. QRS = as AV valves shut
what occurs during isovolumetric contraction?
AV valves shut; pressure in V increases
what occurs during isovolumetric relaxation?
AV valves open - due to pressure in aorta exceeding ventricles
when does ventricular volume decrease?
during ventricular ejection - ST segment
when does ventricular volume increase?
ventricular relaxation - after t wave
what does a lup sound indicate?
closing of AV valves
what does a dup sound indicate?
closing of semi-lunar valves
2 major contractile filaments in myofibrils?
actin + myosin
what makes up I band
thin actin
what makes up A band
thick myosin
describe the chains in myosin filament
2 heavy chains - each of which is attached to a light chain
which 2 proteins are coupled to actin? and how frequently
troponin & tropomyosin - every 7th molecule
which troponin complex binds to actin and which binds to tropomyosin?
T= tropomyosin I = actin
what occurs when Troponin C is added to actin?
- becomes Ca2+ sensitive
- 4 Ca2+ attach
- tropomyosin undergoes a conformational change in shape
- allows myosin to attach
how does heart muscle produce its own ATP?
Creatin kinase moves phosphate from creatin phosphate to ADP.
explain properties of elastic arteries
stretchy to propel blood
3 segments of tunica intima
- endothelium
- basement membrane
- internal elastic lamina
structure at the end of arterioles to capillary
metarterioles
what monitors the blood flow into the capillary?
precapillary sphincter
name for distal end of metarteriole?
thoroughfare channel
what is vasomotion?
contraction of SMC allowing pulsatile flow of blood from metarterioles
which blood vessels have thin walls and large lumens?
venules
what are the greatest capacitance vessels?
veins
2 factors for filtration
blood hydrostatic pressure
interstitial fliud osmotic pressure
2 factors for absorption
intersitital hydrostatic pressure
blood colloid pressure
what condition occurs when filtration > reabsorption?
oedema