circulation 4

Question 1

excitation-contraction coupling- skeletal vs cardiac muscle

Answer 1

skeletal: AP is very fast, which can tetanize skeletal muscle, aka maximal strong, steady contraction
cardiac muscle: all muscle of chamber contract together, chambers contract sequentially, due to ventricle AP being prolonged via Ca delivery delay
-cardiac muscle cannot tetatnize

Question 2

frank-starling mechanism

Answer 2

• stretching cardiac muscle increases tension (think elastic band)
• cardiac stretch intrinsically determines force of cardiac contraction, so when venous bp stretches atrial muscle, atrium responds by contracting proportionally

Question 3

stroke volume, venous pressure, and frank-starling mech

Answer 3

another way to think of it is the greater venous bp, the faster the atrium fills, causing myocytes to stretch, and in response contract harder

• this causes the chamber to PUMP OUT AS MUCH AS IT IS FILLED
• therefore stroke volume is proportional to venous filling pressure, unless it stretches too much and tears cells

Question 4

pacemaker and beta adrenoreceptors, and frank-starling mech evolution

Answer 4

present in all chordates

Question 5

importance of frank-starling mech

Answer 5

1. automatically empties blood entering heart
2. auto increases stroke volume if venous bp and filling increase
3. auto MATCHING OF CHAMBER OUTPUTS (birds and mammals must match ventricular outputs)
4. auto control of blood volume

Question 6

extrinsic stroke volume regulation

Answer 6

neurotransmitters and hormones alter sensitivity of cardiomyocytes to stretch

• +ve inotropic agent like (nor)adrenaline INCREASE STRETCH SENSITIVTY=empty more of chamber
• ve inotropic effect like blocked coronary artery DECREASE STRETCH SENSITIVITY, emptying less of chamber

Question 7

consequences +ve inotropic effect of adrenergnic stimulation

Answer 7

• supply more activator ca2+ for troponin C
• remove Ca2+ faster during relxation
• empties more per beat
• faster cycling at higher heart rate

Question 8

systole vs dystole

Answer 8

systole=cardiac contraction and ejection=end systolic volume (ESV)
-end diastolic volume (EDV)=cardiac relaxation and filling

Question 9

isometric and isotonic contratcion

Answer 9

metric=increases bp until valves open

isotonic generates blood flow after valves open

Question 10

simple principles of pulmonary cardiac cycle

Answer 10

rightside of heart: atrium and ventricle contract with low pressure, pulmonary atery pressure increases w/ right ventricle

Question 11

principles of left/systemic circulation

Answer 11

aortic pressure increases with ventricle pressure

-atrium pressure decreases as ventricle pressure rises

Question 12

cardiac cycle basics

Answer 12

P=sa node
P-Q=atrial depolarization
P-Q=AV node delayed
QRS=left ventricle pumps, ventricular depolarization
t=atrial/ventricular repolarization/relaxation

Question 13

cardiac stroke volume

Answer 13

venous bp fills chamber=EDV end diastolic volume

myocytes are streteched proprtionally to venous bp, determining contraction force, aka ESV end systolic volume

Question 14

increase venous bp

Answer 14

increases EDV, cardiac stretch and contraction force, decreases ESV, and increases cardiac stroke volume

Question 15

ECG=

Answer 15

sum of all cardiac electrical activity

PQRST

Question 16

contractions=

Answer 16

muscle tension>blood pressure>blood flow

Question 17

hearts generate bp

Answer 17

venous bp is low
arterial bp is high
bp is lost to VASCULAR RESISTANCE (bp=QVR; V=IR)

Question 18

Pressure gradients determine direction of flow

Answer 18

• blood flows from veins into heart due to energy left in venous blood
• flows from atrium to ventricle due to energy in atrial blood
• flows from arteries to veins due to arterial bp

Question 19

valves direct blood flow

Answer 19

stop blood from flowing from ventricle to atrium or arteries to heart
and blood is directed to heart when veins have valves