cardiac muslce heart pump and contraction ch 9

Question 1

Name the 2 heart pumps and where they pump

Answer 1

right pump- pulmonary circulation,

left pump- peripheral circulation

Question 2

What is Cardiac rhythmicity?

Answer 2

sequence of cardiac contractions

Question 3

name the muslce types in the heart

Answer 3

atrial, ventricular, specialized excitatory and conductive fibers

Question 4

whats special about the atrial and ventricular muslce fibers?

Answer 4

they contract longer than skeletal muslce

Question 5

what are intercalated discs?

Answer 5

connections between heart muscle cells. they have gap junctions

Question 6

What does the AV bundle do?

Answer 6

transmits conduction from atrium synctium to ventricular. It allows the atria to contract before the ventricles

Question 7

Cardiac action potential

Answer 7

~105 millivolts, The intracellular potential rises from -85 to +20 mv during each beat. The membrane remains depolarized for about .2 seconds( plateau)

Question 8

Whats the reason for the plateau in action potential?

Answer 8

allows the ventricular contraction to be as much as 15 times longer than skeletal muscle

Question 9

what allows the cardiac fibers to have a prolonged AP plateau?

Answer 9

instead of just sodium channels opening they have calcium-sodium channels ( slow calcium channels) The slow channels maintain the depolarization period which causes the plateau

Question 10

what else allows the cardiac fibers to have a prolonged AP and plateau?

Answer 10

after the onset of the AP the permeability of cardiac fibers for potassium ions decreases about 5 fold which doesnt happen in skeletal muscle. This decreases the outflux of potassium ions which prevents early return.

Question 11

Conduction speed of Cardiac cells

Answer 11

.3-.5 seconds. This is slower than nerve fibers and skeletal fibers

Question 12

whats a problem with Tachycardia in regards to the atria?

Answer 12

the fast heart beat doesnt allow the atria to fill the ventricles quick enough.

Question 13

P wave

Answer 13

depolarization through the atria and followed by atrial contraction. This causes a slight rise in atrial pressure

Question 14

QRS waves-

Answer 14

depolarization of Ventricles and causes the ventricular pressure to begin rising

Question 15

T wave-

Answer 15

repolarizing of the Ventricles and ventricular muslce starts to relax

Question 16

Atria as primers

Answer 16

~80 % of blood flows directly through ventricles even before contraction. The Atria simply act as primers that increase ventricular pumping effectiveness as much as 20%.

Question 17

A wave-

Answer 17

Atrial contraction

Question 18

C wave

Answer 18

ventricles begin to contract and blood backflows into atria

Question 19

V wave

Answer 19

occurs toward the end of ventricular contraction. This is when blood is slowly filling the atria while the AV valves are closed

Question 20

Period of rapid filling of ventricles

Answer 20

blood pushes AV valves open and fills the ventricle during the first 1/3 of diastole. Middle 1/3 of diastole involves blood straight from the veins into the ventricles. Last 1/3 of diastole is when the atria contract accounting for an additional 20% of filling

Question 21

isovolumic contraction

Answer 21

period between when the AV valves close and the ventrilces contract and push the semilunar valves open.

Question 22

End diastolic volume

Answer 22

normal filling of ventricles. about 110-120 ml

Question 23

stroke volume output

Answer 23

when ventricles contract and empty to about 70ml

Question 24

end systolic volume

Answer 24

remaining volume in each ventricle after contraction. about 40-50 ml.

Question 25

ejection fraction

Answer 25

fraction of end diastolic volume that is ejected from the heart( jusually about 60%)

Question 26

in regards to end diastolic and end systolic volume, how can stroke volume increase?

Answer 26

increase end diastolic and decrease end systolic volume

Question 27

Semilunar valves functions

Answer 27

Pressure from arteries close them rapidly.

Question 28

first heart sound

Answer 28

closure of AV valves. Low pitch and long lasting

Question 29

second heart sound

Answer 29

aortic and pulmonary valves closing. High pitch and fast

Question 30

stroke work output

Answer 30

amount of energy the heart converts to work during each heartbeat

Question 31

minute work output

Answer 31

total energy converted in one minute.

Question 32

work output of heart

Answer 32

spends energy on moving blood from low to high pressure. Also spends energy speeding blood to its velocity of ejection through the valves

Question 33

the problem with having high systolic pressure

Answer 33

it pushes the actin and myosin filaments far apart and they stop working optimally

Question 34

period of filing

Answer 34

volume increases as blood is pumped into ventricle

Question 35

period of isovolumic contraction

Answer 35

all valves are closed so volume doesnt change but pressure does increase because the ventricles are contracting

Question 36

period of ejection

Answer 36

systolic pressure rises even higher because of ventricular contraction . Volume is decreasing because the aortic valve is now open

Question 37

period of isovolumic relaxation

Answer 37

aortic valve closes and ventricles fall back to starting point which is about 50 mmHg

Question 38

How the heart gets energy

Answer 38

70-90 % is from metabolizing fatty acids. 10-30% from other nutrients like lactate and glucose

Question 39

external work of the heart

Answer 39

oxygen consumption and chemical energy expended during contraction

Question 40

potential energy of the heart

Answer 40

additional work that could be accomplished by contraction of the ventricle if the ventricle were completly emptied

Question 41

what is the maximum efficency of the normal heart?

Answer 41

20-25 % . heart failure can go as low as 5-10%

Question 42

Frank starling mechanism

Answer 42

The greater the heart muscle is stretched during filling, the greater the force of contraction it gives

Question 43

sympathetic mechanism on heart

Answer 43

cause the heart to double its output

Question 44

parasympathetic mechanism on heart

Answer 44

Vagus nerve, Can stop the heart for a couple seonds. Decrease pumping as much as 30% below normal

Question 45

potassium ion effect

Answer 45

excess extracellular ions cause the heart to dilate and become flacid which slows the rate. Also block conduction system through AV node

Question 46

Effect of calcium ions

Answer 46

spastic contractions!!!