Lecture 20 Cardiovascular system 1: Heart Flashcards
3 components of the cardiovascular system
heart, blood, blood vessels
Overview of Cardio system
Heart-> arteries -> arterioles-> capillaries -> venules -> veins (-> return to heart)
Right heart
pumps deoxygenated blood to lungs
pulmonary circulation
lower pressure
Left heart
pumps oxygenated blood to entire body
systemic circulation
higher pressure
atria
receiving chambers
ventricles
pumping chambers
Chamber matched to correct Great Vessel
RA Pulmonary trunk (artery)
LA aorta
Pulmonary circulation
RV -> Pulmonary trunk -> LUNGS -> pulmonary veins -> LA
Systemic circulation
LV -> aorta -> BODY -> vena cavae -> RA
Atrioventricular valves
AV valves
prevent backflow from ventricles to atria
tricuspid valve - RA } RV
Bicuspid (mitral) valve - LA } LV
Role of Chordae tendineae
attached to papillary muscles prevent prolapse of AV valves
Semilunar valves
prevent backflow from arteries to ventricles
pulmonary valve - RV } Pulmonary trunk
aortic valve - LV } aorta
Autorhythmic cells
cardiac muscle cell
spontaneously initiate APs
Intercalated discs
allow AP to spread between cardiac muscle cells
SA node
Sinoatrial node
primary peacemaker
Excitation-Contraction Coupling in Cardiac cells
similar to skeletal muscle
AP -> T tubules -> SR -> releases Ca2+
Ca2+ -> troponin -> tropomyosin -> uncovers myosin binding sites -> uncovers myosin binding sites -> contraction
Roles of Ca2+
Excitation-Contraction Coupling in Cardiac cells
Ca2+ also enters from the ECF through Ca channels during contraction
Ca2+ is pumped back to SR by Ca2+ ATPase during relaxation phase
Ca2+ is also transported back out to ECF by a Na-Ca exchanger
Peacemaker potential in Autorhythmic cells
- Slow depolarization toward threshold = peacemaker potential, “funny channels” permeable to NA+ and K+
- Rapid AP depolarization - due to Ca2+ inflow
- Repolarization
Autonomic NS control
sympathetic - faster depolarization -> increase heart rate
parasympathetic - slower depolarization -> decrease heart rate
Myocardial Action Potential in Contractile Cells
(0) initial AP depolarization - similar to other APs (voltage-gated Na+ channels)
(1) slight repolarization
(2) Plateau Phase (100-200 ms) - due to slow, inward Ca2+ flow (L-type Ca channels) results in long AP duration and long refractory period (200-300ms)
(3) repolarization - due to delayed opening of voltage-gated K channels
autorhythmic cells are
“peacemakers”
Conduction fibers
specialized to spread AP rapidly though ventricles Sinoatrial node (SA) -> atrial depolarization -> atrioventricular (AV) node (0.1 second delay) -> AV bundle (of his) -> R & L bundle branches -> Purkinje fibers -> ventricular depolarization
Electrocardiogram (ECG)
P wave - atrial depolarization
QRS complex- ventricular depolarization
T wave- ventricular repolarization
At the plateau phase
the S-T segment
all cardiac cells are depolarized
