Lecture 5: Cardiac Muscle Mechanics

Question 1

Increases in heart rate alone inc/dec the duration of diastole

Answer 1

decrease duration of diastole

Question 2

Increases in heart rate alone inc/dec the stroke volume

Answer 2

increase SV

Question 3

3 factors contribute to stroke volume:

Answer 3

preload, contractility, afterload

Question 4

The greater the volume of blood at end-diastolic pressure, the less/greater volume of blood ejected during systolic contraction

Answer 4

GREATER the volume of blood ejected during systolic contraction

Question 5

what causes an immediate rise in contractile force in resting cardiac fiber in the very next contraction?

Answer 5

stretching

Question 6

with stretch, the sarcomere increase in length causes an inc/dec in cross-bridge formation

Answer 6

increase

Question 7

At longer sarcomere lengths results in a inc/dec in Ca++ activated thin filaments at physiological concentrations

Answer 7

increase!

Question 8

The ejected volume will change to give the same _____

Answer 8

ESV (end systolic volume)

Question 9

Because preload affects cardiac function by changing the sarcomere length, this type of regulation is called ___________

Answer 9

heterometric regulation

Question 10

the load against which the heart must contract to eject the blood:

Answer 10

afterload

Question 11

what is the physical afterload of the heart?

Answer 11

aortic pressure

Question 12

what is the physical preload of the heart?

Answer 12

volume in a ventricle just before the start of systole

Question 13

as afterload increases, stroke volume will _______

Answer 13

decrease

afterload and SV are indirectly proportional

Question 14

if the afterload (aortic pressure) increases, the heart must develop a less/greater pressure to open the aortic valve

Answer 14

greater

Question 15

if the afterload (aortic pressure) increases, the shortening velocity will _________

Answer 15

decrease

afterload indirect proportional to shortening velocity

Question 16

An increase in afterload will cause a dec/inc stroke volume at any preload

Answer 16

dec

preload indirect proportional to SV

Question 17

a dec in afterload will cause a inc/dec of SV at any preload

Answer 17

inc

Question 18

An increase in preload will inc/dec the force generated during shortening (velocity during shortening)

Answer 18

inc

Question 19

An decrease in preload will inc/dec the force generated during shortening (velocity during shortening)

Answer 19

decrease

Question 20

t/f: Changes in preload do not alter Vmax

Answer 20

trueeee

Question 21

t/f: Contractility (or inotropy) is dependent on preload and afterload

Answer 21

false

Question 22

this factor on stroke volume it is related to the** rate of force development during ejection (DP/Dt):**

Answer 22

contractility (iontropy)

Question 23

the inotropic state is increased by WHAT stimulation to the heart

Answer 23

SYMPATHETIC

Question 24

the inotropic state is decreased by _______ stimulation to the heart

Answer 24

PARASYMP

Question 25

1. IONOTROPY is direct/indirect proportional to **contractile force (stroke volume) **at any preload?
2. IONOTROPY is direct/indirect to the **velocity of shortening SV **at any preload
   3.

check this slide*

Answer 25

• 1 & 2 both indirectly proportional
• 3 &4

Question 26

t/f: changes in inotropy will alter Vmax

Answer 26

true

Question 27

Positive inotropic effects result from 3 things:

Answer 27

1. Increased rate of delivery of Ca++ to the myofibrils
2. Increased binding of Ca++ to troponin C
3. Increased rate of cross-bridge cycling

Question 28

Negantive inotropic effects result from 3 things:

Answer 28

heart failure

cardiomyopathy

ischemia