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FHB Exam 1 - Cardiovascular Physiology > Lecture 11 - Cardiac Function > Flashcards

Lecture 11 - Cardiac Function Flashcards

1
Q

What are the 4 determinants of Cardiac Output?

A
  1. Heart Rate
  2. Contractility
  3. Preload
  4. Afterload
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2
Q

What is isometric contraction?

A

contraction WITHOUT change in length (shortening)

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3
Q

What is the load on the muscle BEFORE contraction is initiated?

A

PRELOAD

  • stretches the muscle length and creates PASSIVE tension
  • same as END-DIASTOLIC VOLUME
    (volume before the LV contracts - exerts wall pressure)
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4
Q

What is the load on the muscle AFTER contraction is initiated?

A

Afterload

  • load on the muscle AFTER contraction is initiated
  • ex: arterial pressure reisting LV contraction
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5
Q

What is any force that resists muscle shortening?

A

AFTERLOAD

  • based on arterial BP, heart size, aortic valve)
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6
Q

What is contractility? What is it based on? What is it INDEPENDENT of?

A
  1. ability of actin & myosin cross-bridges to form & generate contractile force
  2. Based on intracellular Ca
  3. Independent of PRELOAD and AFTERLOAD
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7
Q

If a muscle is unable to create enough FORCE to overcome after load (ex: push aortic valve open) then the contraction is:

  1. Isometric
  2. Isotonic
A

ISOMETRIC (no muscle shortening)

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8
Q

What is ISOTONIC contraction?

A

contraction WITH muscle shortening but with CONSTANT FORCE (no change)

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9
Q

If a muscle IS able to generate enough force to meet the after load, the contraction is:

  1. Isotonic
  2. Isometric?
A

ISOTONIC

  • muscle shortening occurs
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10
Q

During a normal cardiac cycle, what comes first? Isometric or Isotonic contractions?

A

1st = ISOMETRIC (increasing force, but muscle has not shortened yet)

2nd = ISOTONIC
(muscle shortens at a constant max force)

ex: lifting a 10 lb weight
- first isometric (muscle shortens) then isotonic

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11
Q

An increase in cardiac muscle length will increase or decrease contraction strength?

A

Increase contraction strength

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12
Q

If you increase the amount of tension that develops passively by stretching the muscle, how does this affect PRELOAD?

A

Increases preload

ventricular filling volume or end-diastolic volume

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13
Q

The slope of the Resting (Diastolic) Tension graph is determined primarily by what?

A

COMPLIANCE

change in volume/ change in pressure

(change in length/ change in tension)

  • increase tension = LESS compliant
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14
Q

A decrease in cardiac muscle compliance, increases or decreases the slope of the Resting Tension(Diastolic)?

A

INCREASES the slope (pressure on y-axis & length on bottom)

  • Compliance inversely related to pressure
  • so once compliance decreases, greater tension/pressure is felt during PRELOAD
  • as the tension increases
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15
Q

How can compliance be explained in terms of a bike tire/water ballon analogy?

A

the bike tire has greater tension and is thus less compliant

  • water balloon has less tension and is MORE compliant
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16
Q

Name the term for the following:

The amount of isometric tension that is developed by muscle contraction at a particular muscle length (preload).

A

AFTERLOAD

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17
Q

In the systolic tension curve, what represents the slope?

A

CONTRACTILITY
- as contractility increases the line moves UP and to the left

i.e. sympathetics

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18
Q

What has higher compliance, skeletal or cardiac muscle?

A

SKELETAL

  • cardiac is less compliant and developed tension at shorter muscle lengths than skeletal
  • higher pressure at a given volume/length
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19
Q

Why do cardiac cells primarily work on the ASCENDING limb of the LENGTH-TENSION graph?

A
  • because they have relatively LOW compliance
20
Q

In the heart, what does SYSTOLIC tension curve represent?

A

STROKE VOLUME

21
Q

BOARDS QUESTION:

How does the infusion of fluid into the venous system increase cardiac output?

A
  • INCREASES THE SARCOMERE LENGTH of the muscle cell
  • increases preload and thus contraction & cardiac output
  • increases BP
22
Q

Determine which statement determines Systole & Diastole

  1. Passive Increase in force
  2. Actin & Myosin interaction
A
  1. Diastole

2. Systole

23
Q

What is a component in a sarcomere that generates RESISTANCE upon lengthening of the sarcomere ?

A

TITIN!!

  • think of a sarcomere like a rubber band
24
Q

if you increase end-diastolic volume, is contraction increased or decreased?

A

INCREASED

25
Q

What is the inherent ability of actin & myosin to generate tension? This is determined by what?

A

CONTRACTILITY (inotropy)

intracellular Ca!

(increase Ca = increase contractility)

26
Q

A positive inotropic affect will shift the length-tension graph where?

A

UP and LEFT

ex: w/ sympathetics
- able to contract more

27
Q

How does an increase in preload cause an increase in tension development?

A
  1. Increase in Actin-Myosin overlap

2. increase Ca sensitivity of myofilaments

28
Q

How does one change the slope of the Diastolic tension? Systolic?

A
  1. change Compliance
    - increase slope by DEcreasing compliance
  2. Change Contractility
    - increase slope by increasing compliance
29
Q

Changing preload on isotonic contractions, changes what?

A

MUSCLE length

30
Q

Describe the affects of increasing and decreasing preload on muscle shortening in isotonic contractions.

A

Increasing preload INCREASES muscle shortening

decreasing preload decreases shortening
less passive force

31
Q

Describe the affects of increasing and decreasing AFTERLOAD on muscle shortening in ISOTONIC contractions.

A

INCREASING after load, DECREASES muscle contraction

-as arterial pressure goes up = less shortening, less STROKE VOLUME

decreasing after load, decreases muscle contraction

32
Q

Increasing contractility does what to the PEAK ISOMETRIC tension and rate of relaxation? How can this affect be achieved?

A
  1. Increases BOTh the isometric tension & the rate of relaxation (shifts graph up and left)
    - oppostive occurs when contractility is reduced –> graphed pushed further RIGHT and relaxation is slower –> wider curve)
  2. Sympathetic stimulation! (positive inotropic)
33
Q

At constant after load & preload, does increasing contractility increase or decrease muscle shortening?

A

INCREASES (greater change in length)

  • think of water balloon vs. bike tire
34
Q

What affect would INCREASING contractility have on the following:

  1. Muscle shortening
  2. Velocity of shortening
  3. Rate of relaxation
A
  1. INCREASE shortening
  2. Increase Velocity
  3. Increase rate of relaxation
    (sympathetic stimulation via SERCA activation & Ca uptake)
35
Q

Increasing the after load, increases or decreases the velocity of ISOTONIC (same force) contraction?

A

DECREASES the after load

36
Q

What is Vmax?

A

max velocity of shortening with no load

37
Q

What is the term for when a muscle cannot meet the after load?WHat value does it equal?

A

MAXIMUM VELOCITY OF SHORTENING

= zero

38
Q

How does Increasing the preload affect the force-velocity curve in terms of afterload?

A

Increasing preload increases the velocity
- shifts the line RIGHT

  • line is longer –> more force and greater velocity

(at any after load)

39
Q

Is Vmax changed when preload is changed? What changes Vmax?

A

NO!

contractility changes max (it increases the maximum velocity!!)

40
Q

How does increasing CONTRACTILITY affect the force velocity curve?

A

SHIFTS it UP and and to the right

- increases Vmax

41
Q

Changes in contractility and preload change what value ultimately?

A

the MAXIMUM ISOMETRIC FORCE

at zero

42
Q

Increasing afterload causes what changes to

  1. Velocity of muscle shortening
  2. Amount of muscle shortening
A

DECREASES velocity & amount of shortening

  • think of something pushing against a saloon door on 1 side, but you don’t have enough force to push against them and open the door (so velocity and shortening is decreased)
43
Q

At any given after load
Decreasing:
1. Preload
2. Contractility

changes the velocity of shortening how?

A

DECREASES the velocity of shortening

44
Q

When an infarct occurs, is compliance of the tissue increased or decreased?

A

DECREASED

  • slope on length-tension graph is increased
  • pressure goes up abnormally & prevents normal filling of blood
45
Q

What are two mechanisms for rapid relaxation?

A
  1. Phospholamban inhibition - therefore SERCA is active

2. lower affinity of Troponin C to Calcium

46
Q

How is stroke volume affected if velocity of shortening is reduced?

A

LESS STROKE VOLUME!

  • imagine a water balloon squeeze quickly = water shoots up
    squeeze slowly = water just flops over (not enough pressure)
47
Q

What is a clinical case we heard about that the after load is increased so aortic valve is not opening and a “thump” is heard?

A

PVC

FHB Exam 1 - Cardiovascular Physiology (26 decks)

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