Unit 1 Lecture 4

Question 1

What is ventricular systole?

Answer 1

DEPOLARIZATION (contraction) of ventricular cardiac muscle fibers

• when the ventricles contract, PRESSURE in ventricles INCREASES -> ejects blood

Question 2

What is ventricular diastole?

Answer 2

REPOLARIZATION (relaxation) of ventricular cardiac muscle fibers

• when ventricles eject blood, PRESSURE in ventricles DECREASES -> AV valves loosen up -> Passive filling of the ventricles

Question 3

What does passive filling of the ventricles means?

Answer 3

Immediately after the ventricles eject blood, the atria fills with blood but the WEAK muscle around the AV valve causes some blood to slowly leak through BEFORE atrial contraction

Question 4

What is atrial systole?

Answer 4

Contraction of the atria -> remainder of blood (that hasn’t drained into ventricle) is pumped into the ventricle

Question 5

How is the majority of blood pumped into the ventricles?

Answer 5

“passive filling”

Question 6

Once the atria has pumped all of its blood into the ventricles, what is that blood called?

Answer 6

End diastolic volume

Question 7

Define end diastolic volume

Answer 7

the amount of blood pumped into the ventricles by the atria during ventricle diastole

Question 8

True of false,

The ventricles pump out all of their blood during ventricular contraction?

Answer 8

FALSE

*some blood is left over in the ventricles

Question 9

What is the blood leftover in the ventricle after contraction called?

Answer 9

End systolic volume

Question 10

Define end systolic volume

Answer 10

The amount of blood leftover in the ventricle that was not pumped out

Question 11

Define stroke volume

Answer 11

The volume of blood pumped out of the heart per beat

Question 12

Formula for stroke volume (SV)

Answer 12

(SV) = End diastolic volume - end systolic volume

Question 13

What is the average stroke volume at rest?

Answer 13

0.07 L/beat

Question 14

What are the 3 factors that determine stroke volume?

Answer 14

1. Afterload
2. Preload
3. Contraction of ventricles (active or passive)

Question 15

Define preload

Answer 15

END DIASTOLIC VOLUME

How much blood is in the ventricle before contraction

Question 16

Define afterload

Answer 16

the (ventricular) pressure required to open the aortic valve

*there’s blood already in the aorta so afterload is the amount of pressure that the ventricle must exert to eject its blood out

Question 17

What are the 2 types of ventricular contraction that effects stroke volume?

Answer 17

• active contraction

- passive contraction

Question 18

Define active contraction

Answer 18

Requires energy to contract (cardiac muscle)

Question 19

Define passive contraction

Answer 19

Does not require energy to contract (cardiac muscle)

Question 20

What does contractility mean?

Answer 20

refers to the STRENGTH of cardiac muscle contraction

Question 21

What does active contraction involve?

Answer 21

Stimulation of the sympathetic nerves to the heart

Question 22

What does passive contraction involve?

Answer 22

Changing the length of cardiac muscle fibers (“Frank-Starling Mechanism”)

Question 23

During ACTIVE contraction, what stimulates the sympathetic nerves?

Answer 23

NE (or epinephrine)

Question 24

What does NE do to the heart in active contraction?

Answer 24

• Increases Ca channels to open -> influx into heart
• Increases pacemaker activity
• increases force of contraction

Question 25

What is the Frank-Starling Mechanism?

Answer 25

A law that states-

INCREASING preload (the amount of blood in ventricles before contraction) ->

INCREASING contractility (strength of contraction/ how much cardiac muscle is stretched) ->

INCREASES stroke volume (volume pumped out of the heart)

Question 26

What is the optimal length of a sarcomere during contraction?

Answer 26

2.2 micrometers

Question 27

What is the resting length of a sarcomere?

Answer 27

1.8 micrometers (understretched)