Heart Facts Flashcards
Two types of valves in heart
Atrio-ventricular and semilunar
Location of Mitral valve
Between left atrium and left ventricle
Name the two semilunar valves
Aortic, Pulmonary
Location of Tricuspid valve
From right atrium to right ventricle
Which type of heart valve is attached by chordae tendinae to the papillary muscles?
Atrio-ventricular (Tricuspid - right, Mitral - left)
Location of semi-lunar valves
Leading out of heart (ventricles), to aorta and pulmonary artery
Name the two atrio-ventricular valves
Tricuspid (right), Mitral (left)
Pressure difference required to open tricuspid valve
Right atrium > right ventricle
Pressure difference required to open pulmonary valve
right ventricle > pulmonary artery
Pressure difference required to open aortic valve
left ventricle > aorta
Pressure difference required to open mitral valve
Left atrium > left ventricle
Valve that opens when:
right atrial pressure > right ventricular pressure
Tricuspid valve (atrio-ventricular)
Valve that opens when:
right ventricular pressure > pulmonary arterial pressure
Pulmonary valve (semilunar)
Valve that opens when:
left ventricular pressure > aortic pressure
Aortic valve (semilunar)
Valve that opens when:
left atrial pressure > left ventricular pressure
Mitral valve (atrio-ventricular)
Effect of noradrenaline on nodal cells
Incr. Phase 4 (slow depol.) slope -> Incr HR
Dominant ion in pacemaker cell AP repolarization
K+ out (slow)
Receptors on smooth muscle cells for adrenaline
ß2
Result of isovolumetric relaxation
Sharp decrease in ventricular pressure
Signal path of low coronary artery blood flow
Low O2 (ischemia)
Afferent nerve ending signal to brain
“Pain” signal, localized in chest
Effect of noradrenaline on vascular smooth muscle cells
Incr. intracellular [Ca++] -> Vasoconstriction
Mechanism of blood flow from atrium to ventricle
First: passive flow based on pressure difference
Second: atrial contraction (‘bump’ in atrial & ventricular pressure, increase in ventricular blood volume)
Frank-Starling Law
Increase muscle stretch -> Increase contraction strength (within reason)
Mechanism of hormones causing vasodilation
- Activate G protein (GI)
- Convert GTP -> cGMP
- Phosphorylate (inhibit) MLCK
- –> VASODILATION
Effect/mechanism of vasopressin on BP
- Incr SVR
- Incr. kidney water retention -> Incr blood volume
- –> Incr BP
Effect of noradrenaline on ventricular muscle cells
Incr intracellular [Ca++] -> Incr Stroke Volume
What causes the sounds in the cardiac cycle?
Closing of valves:
S1 - atrio-ventricular
S2 - semilunar
Cause of heart attack
Plaque (cholesterol core, fibrous exterior) narrows artery
During exertion, coronary artery blood flow does not meed tissue oxygen demands
PAIN
Effect of adrenaline on nodal cells
Incr. Phase 4 (slow depol) slope -> Incr HR
Dominant ion in cardiac contractile cell AP downstroke
K+ out (fast)
Relation of Frank-Starling law to Cardiac Output
Muscle stretch = End-diastolic volume (pre-load)
Contraction = Stroke Volume
-> Incr. EDV, Incr SV (and CO)
When in the cardiac cycle does S1 occur?
Early ventricular systole
ECG pen deflection from repolarization, from + to - end of lead
Up (T wave)
Direction of depolarization across heart
Top to bottom
Mechanism to correct high blood pressure (nervous system)
- Incr baroreceptor stretch
- Incr AP firing
- Incr stimulation of PSNS, incr inhibition of SNS
- Decr HR, SV, SVR
- Restore BP
Role of chordae tendinae & papillary muscles
hold atrio-ventricular valves closed during ventricular contraction
Primary regulatory method for coronary arteries
Metabolic regulation
Where are renin & angiotensin II released from?
kidney; stimulated by SNS
Location of pacemaker cells
Sinoatrial (SA) node: where superior vena cava meets right atrium
Atrioventricular (AV) node: where right atrium meets right ventricle
Cause of low coronary artery blood flow
Coronary artery spasm (drugs/alcohol) Artery narrowing (plaques)
Receptors on nodal cells for acetylcholine
muscarinic
Hormones causing vasodilation in vascular smooth muscle
Atrial Natriuretic Peptide (ANP) -> from heart
Result of isovolumetric contraction
Large increase in ventricular pressure
Cause of athletic bradycardia
Left ventricular hypertrophy increases SV
Vagal tone increases to lower HR, maintaining CO
ECG pen deflection from depolarization, from + to - end of lead
Down
Describe coronary blood flow
Always high, but lower during systole, particularly in the left ventricle
Dominant ion in cardiac contractile cell AP plateau
Ca++ in (slow) counteracts K+ out (fast)
Physiological response to heart attack
Diaphoresis & dyspneia - from exertion or anxiety
Tachycardia - to compensate for narrowed artery