Heart,Blood

Question 1

bundle of His

Answer 1

special conducting tract within the interventricular septum of the mammalian heart running from the atrioventricular (AV) node toward the poles of the ventricles

Question 2

compensatory pause

Answer 2

longer than normal pause between two heart beats following an extrasystole

Question 3

extrasystole

Answer 3

excitation and contraction of the heart not corresponding to the normal sinus rhythm

Question 4

pulse volume

Answer 4

volume of blood pumped by the heart into the circulation during one systole

Question 5

diastole

Answer 5

the phase in the heartbeat during which the myocardium is relaxed and the ventricles are filling with blood


Question 6

mean electrical axis

Answer 6

direction of the electrical vector of the heart at the peak of the R-wave


Question 7

scalar electrocardiogram

Answer 7

signal measured in any of the Einthoven leads, corresponding to the projection of the electrical vector of the heart onto a line connecting two electrodes, thus transforming the vector into a scalar variable

Question 8

Einthoven leads

Answer 8

standard way of electrode positioning for recording ECG in humans

Question 9

atrium

Answer 9

chamber of the heart into which venous blood is returning


Question 10

isometric (isovolumic) contraction (in the heart)

Answer 10

contraction of the ventricles while valves are closed and volume is constant

Question 11

isometric (isovolumic) relaxation

Answer 11

contraction of the ventricles while valves are closed and volume is constant

Question 12

isometric (isovolumic) relaxation

Answer 12

relaxation of the ventricles while valves are closed and volume is constant

Question 13

maximal ejection

Answer 13

part of the heart cycle following the opening of the semilunar valves during systole

Question 14

output of the heart

Answer 14

blood volume pumped by the heart into the circulation in one minute

Question 15

baroceptor reflex

Answer 15

reflex mechanism starting from baroceptors in the sinus and in the aortic arch and regulating blood pressure


Question 16

carotid sinus

Answer 16

dilatation of the internal carotid artery at its origin, containing many baroreceptors

Question 17

colloid osmotic pressure

Answer 17

osmotic pressure generated by blood proteins unable to penetrate through the capillary wall


Question 18

depressor area (center)

Answer 18

collection of neurons located caudally and medially from the pressor area in the medulla decreasing blood pressure by the inhibition of the pressor area and by the excitation of the vagal efferents running to the heart

Question 19

Evans blue

Answer 19

blue stain that cannot penetrate the capillary wall; used for measuring the blood volume

Question 20

hematocrit

Answer 20

percentage of total blood volume occupied by (mostly red) blood cells, in humans it is normally between 40-50%


Question 21

precapillary sphincter

Answer 21

muscular ring at the origin of capillaries regulating blood flow in the capillary

Question 22

pressor area (center)

Answer 22

area in the dorsolateral reticular formation of the medulla; its excitation increase heart rate, constrict vessels, thus increases blood pressure through sympathetic fibers

Question 23

arteriovenous oxygen difference

Answer 23

difference between the partial pressure of oxygen in the arterial and venous blood flowing to and from an organ

Question 24

Starling’s hypothesis

Answer 24

theory to explain the production and absorption of interstitial