Unit III -the Heart

Question 1

Where can we find intecalated discs?

Answer 1

Between cardiac muscle cells

Question 2

What is the resting membrane potential of cardiac muscle?

Answer 2

Ca. -85 to -95 millivolts

Question 3

What is the action potential of cardiac muscle?

Answer 3

105 millivolts

Question 4

For how long is the membrane depolarized in atria?

Answer 4

0.2 seconds

Question 5

For how long is the membrane depolarized in the ventricle?

Answer 5

0.3 seconds

Question 6

Striated muscles

Answer 6

• Cardiac muscle

- Skeletal muscle

Question 7

Which muscles have fast sodium channels?

Answer 7

Skeletal muscles

Question 8

Which muscle has slow calcium channels?

Answer 8

Cardiac muscle

Calcium that enters these channels also promotes cardiac muscle contraction

Question 9

What promotes muscle contraction?

Answer 9

Diffusion of calcium into the myofibrils

Question 10

Isovolemic relaxation

Answer 10

Is caused by ventricular relaxation

Question 11

Period of ejection

Answer 11

Is when ventricular outflow occur

Question 12

Most ejection occurs during this period

Answer 12

Period of rapid ejection

Question 13

Ejection fraction

Answer 13

The fraction of end-diastolic volume that is ejected

Question 14

End-diastolic volume

Answer 14

The volume of each ventricle (110-120 milliliters) atthe end of diastol

Question 15

The stroke volume

Answer 15

• 70 milliliters

- Is the amount of the blood ejected with each beat

Question 16

The end-systolic volume

Answer 16

• 40-50 milliliters

- Is the remaining volume in th ventricle at the end of systole

Question 17

Incisura

Answer 17

A slight increase in aortic pressure. It is caused by a slights backflow of blood followed by a sudden cessation of flow

Question 18

Diastolic pressure

Answer 18

80mm Hg

Question 19

The A-V valves are:

Answer 19

• Triquspid valve

- Mitral valve

Question 20

Semilunar valves are:

Answer 20

• Aortic valve

- Pulmonar valve

Question 21

The stroke work output of the ventricles

Answer 21

Is the output of energy by the heart during each heartbeat

Question 22

Cardiac output

Answer 22

Is the sum of all the local tissue blood flows

Question 23

Poiseuille’s law

Answer 23

• vessle diameter has a marked effect on resistance to blood flow
• vascular resistan ce is directly propotional to the viscosity of blood and the length of the blood vessles and inversily propotional to the radius of the vessles raised to the fourth power

Question 24

Conductance

Answer 24

Is a measure of ease of which blood can flow through a vessle and is the resiprocal of resistance

Question 25

Hematocrit

Answer 25

• The precentage of blood comprising the cells

- Normally about 40% -> 40% of the blood is cells the rest is plasma

Question 26

Vascular compliance (capacitance)

Answer 26

Is the total quantity of blood that can be stored in a given part of the circulation for each millimeter mercury of pressure

Question 27

What three muscles is the heart composed of?

Answer 27

• atrial muscle
• ventricular muscle
• excitatory and conductive muscle fibers

Question 28

What type of junction is in the intercalated discs?

Answer 28

They form permeable junctions (gap junctions)

Question 29

What three muscles is the heart composed of?

Answer 29

• atrial muscle
• ventricular muscle
• excitatory and conductive muscle fibers

Question 30

What type of junction is in the intercalated discs?

Answer 30

They form permeable junctions (gap junctions)

Question 31

What is the normal refractory period of the ventricle?

Answer 31

0.25-0.30 seconds, which is about the duration of the prolonged plateau action potential

Question 32

Relative refractory period is about……. Seconds

Answer 32

0.05

Question 33

What does the term “exitation-contraction coupling” refer to?

Answer 33

It refers to the mechanism by which the action potential causes the myofibrils of muscle to contract.