Lecture 20 Cardiovascular system 1: Heart

Question 1

3 components of the cardiovascular system

Answer 1

heart, blood, blood vessels

Question 2

Overview of Cardio system

Answer 2

Heart-> arteries -> arterioles-> capillaries -> venules -> veins (-> return to heart)

Question 3

Right heart

Answer 3

pumps deoxygenated blood to lungs
pulmonary circulation
lower pressure

Question 4

Left heart

Answer 4

pumps oxygenated blood to entire body
systemic circulation
higher pressure

Question 5

atria

Answer 5

receiving chambers

Question 6

ventricles

Answer 6

pumping chambers

Question 7

Chamber matched to correct Great Vessel

Answer 7

RA Pulmonary trunk (artery)

LA aorta

Question 8

Pulmonary circulation

Answer 8

RV -> Pulmonary trunk -> LUNGS -> pulmonary veins -> LA

Question 9

Systemic circulation

Answer 9

LV -> aorta -> BODY -> vena cavae -> RA

Question 10

Atrioventricular valves

Answer 10

AV valves
prevent backflow from ventricles to atria
tricuspid valve - RA } RV
Bicuspid (mitral) valve - LA } LV

Question 11

Role of Chordae tendineae

Answer 11

attached to papillary muscles prevent prolapse of AV valves

Question 12

Semilunar valves

Answer 12

prevent backflow from arteries to ventricles
pulmonary valve - RV } Pulmonary trunk
aortic valve - LV } aorta

Question 13

Autorhythmic cells

Answer 13

cardiac muscle cell

spontaneously initiate APs

Question 14

Intercalated discs

Answer 14

allow AP to spread between cardiac muscle cells

Question 15

SA node

Answer 15

Sinoatrial node

primary peacemaker

Question 16

Excitation-Contraction Coupling in Cardiac cells

Answer 16

similar to skeletal muscle
AP -> T tubules -> SR -> releases Ca2+
Ca2+ -> troponin -> tropomyosin -> uncovers myosin binding sites -> uncovers myosin binding sites -> contraction

Question 17

Roles of Ca2+

Excitation-Contraction Coupling in Cardiac cells

Answer 17

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

Question 18

Peacemaker potential in Autorhythmic cells

Answer 18

1. Slow depolarization toward threshold = peacemaker potential, “funny channels” permeable to NA+ and K+
2. Rapid AP depolarization - due to Ca2+ inflow
3. Repolarization

Question 19

Autonomic NS control

Answer 19

sympathetic - faster depolarization -> increase heart rate

parasympathetic - slower depolarization -> decrease heart rate

Question 20

Myocardial Action Potential in Contractile Cells

Answer 20

(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

Question 21

autorhythmic cells are

Answer 21

“peacemakers”

Question 22

Conduction fibers

Answer 22

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

Question 23

Electrocardiogram (ECG)

Answer 23

P wave - atrial depolarization
QRS complex- ventricular depolarization
T wave- ventricular repolarization

Question 24

At the plateau phase

Answer 24

the S-T segment

all cardiac cells are depolarized

Question 25

The P-R segment

Answer 25

period of delay at AV node