Lecture 5: Cardiac Muscle Mechanics Flashcards
Increases in heart rate alone inc/dec the duration of diastole
decrease duration of diastole
Increases in heart rate alone inc/dec the stroke volume
increase SV
3 factors contribute to stroke volume:
preload, contractility, afterload
The greater the volume of blood at end-diastolic pressure, the less/greater volume of blood ejected during systolic contraction
GREATER the volume of blood ejected during systolic contraction
what causes an immediate rise in contractile force in resting cardiac fiber in the very next contraction?
stretching
with stretch, the sarcomere increase in length causes an inc/dec in cross-bridge formation
increase
At longer sarcomere lengths results in a inc/dec in Ca++ activated thin filaments at physiological concentrations
increase!
The ejected volume will change to give the same _____
ESV (end systolic volume)
Because preload affects cardiac function by changing the sarcomere length, this type of regulation is called ___________
heterometric regulation
the load against which the heart must contract to eject the blood:
afterload
what is the physical afterload of the heart?
aortic pressure
what is the physical preload of the heart?
volume in a ventricle just before the start of systole
as afterload increases, stroke volume will _______
decrease
afterload and SV are indirectly proportional
if the afterload (aortic pressure) increases, the heart must develop a less/greater pressure to open the aortic valve
greater
if the afterload (aortic pressure) increases, the shortening velocity will _________
decrease
afterload indirect proportional to shortening velocity
An increase in afterload will cause a dec/inc stroke volume at any preload
dec
preload indirect proportional to SV
a dec in afterload will cause a inc/dec of SV at any preload
inc
An increase in preload will inc/dec the force generated during shortening (velocity during shortening)
inc
An decrease in preload will inc/dec the force generated during shortening (velocity during shortening)
decrease
t/f: Changes in preload do not alter Vmax
trueeee
t/f: Contractility (or inotropy) is dependent on preload and afterload
false
this factor on stroke volume it is related to the** rate of force development during ejection (DP/Dt):**
contractility (iontropy)
the inotropic state is increased by WHAT stimulation to the heart
SYMPATHETIC
the inotropic state is decreased by _______ stimulation to the heart
PARASYMP
- IONOTROPY is direct/indirect proportional to **contractile force (stroke volume) **at any preload?
- IONOTROPY is direct/indirect to the **velocity of shortening SV **at any preload
3.
check this slide*
- 1 & 2 both indirectly proportional
- 3 &4
t/f: changes in inotropy will alter Vmax
true
Positive inotropic effects result from 3 things:
- Increased rate of delivery of Ca++ to the myofibrils
- Increased binding of Ca++ to troponin C
- Increased rate of cross-bridge cycling
Negantive inotropic effects result from 3 things:
heart failure
cardiomyopathy
ischemia
