Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key


Play button


Play button




Click to flip

52 Cards in this Set

  • Front
  • Back
What does the heart really consist of?
2 Separate pumps that are coupled together in series.
How does the heart maintain a state of mass balance so the same volume of blood that enters the right heart gets pumped out of the left heart?
By nature of the length tension diagram of the heart - Starling's Law of the Heart.
What are 2 ways that the right and left heart are separate from each other?
1. Mechanical isolation
2. Electrical isolation
What are the structures that are the basis of mechanical isolation?
1. Septa
2. Valves
What do the AV and semilunar valves do?
Prevent backflow
What do Papillary muscles do?
Prevent prolapse of valves during ventricular contraction.
What connects the papillary muscles to the valves?
Chordae tendineae
Which side of the heart has a bigger wall? Why?
The left heart - because it has to pump blood through the entire systemic circulation.
How are Cardiac and Skeletal muscle similar?
They are both striated and contain fairly uniform arrangements of their sarcomeres.
How are Cardiac and Skeletal muscle different?
-Skeletal myocytes contract independently
-Cardiac myocytes contract as a syncytium
What allows cardiac myocytes to contract all together as a syncytium?
Intercalated disks which are gap junctions.
What features of gap junctions allow syncytial contractions of cardiac muscle?
-Low electrical resistance
-Free diffusion of ions between cells
-Spread of APs from cell to cell
So what happens when one area of the heart depolarizes?
It spreads throughout the entire heart and induces contraction.
So what SEPARATES cardiac myocytes? What connects them?
-Intercalated discs separate
-Gap junctions connect
Is the entire heart all one syncytium?
No; it is separated into Atrial and Ventricular Synctia
What is the thing that separates the Atrial syncytia from Ventricular?
The AV Bundle
What is the AV bundle?
A fibrous ring that prevents Action potentials from passing from the atrial muscles to the ventricles without passing through a specific bundle of conductive fibers
What is the result of the AV bundle's regulation of APs passing from the atrium to ventricle?
It allows the atria to contract ahead of the ventricles.
What is the fundamental difference in Cardiac muscle action potentials compared to skeletal muscle?
It has a very long plateau at the top of the action potential
Why do Cardiac muscle action potentials have such a long plateau?
To prevent repeated contractions of the muscle - tetany of the heart is very bad.
What allows for cardiac muscle to not contract during the plateau?
It is refratory to repeated stimulation.
What is the rate of propagation of action potentials around the heart?
Relatively slow
What is the amplitude of a cardiac muscle action potential? What is its range of magnitude?
Amplitude = 105 mV
Magnitude: from -85 to +20
How long is the plateau of a cardiac muscle AP compared to skeletal muscle?
15X longer
How long does atrial muscle remain depolarized? Ventricular? Skeletal muscle?
Atrial: 0.2 sec
Ventricle: 0.3 sec
Skeletal: much shorter time
How does the length-tension relationship for cardiac muscle affect its function?
At optimal sarcomere lengths caused by degree of filling of the ventricles, the muscle will contract with more force.
How does crossbridge cycling occur in cardiac muscle?
By the same mechanism as in skeletal muscle - the sliding filament mechanism.
What does the degree of filling of the heart ventricles determine?
The amount of passive force that is in the muscle prior to contraction.
What limits cardiac muscle from stretching beyond its normal physiologic lengths at which active force would drop off?
The pericardium
What is the nature of the slope of the length tension curve for cardiac muscle within the normal physiologic range?
Steep - so slight changes in length (heart filling) have pretty significant effects in the force generated during contraction.
What is the major portion of work that is done by the heart?
Stroke work output - Volume-Pressure work.
What is the minor portion of work that is done by the heart?
The work of acceleration of blood to its velocity of ejection.
What is Preload?
End diastolic pressure
What is Afterload?
Systolic pressure
What is meant by the term Preload?
The amount of blood that is coming into the heart - the "prestretch" of blood returning to the heart
What is meant by the term Afterload?
The force that the heart is pumping into.
What is generated when you allow the heart to fill, clamp the aorta, and measure the pressure in the left ventricle with subsequent cycles of filling and isovolumic contraction?
The left ventricular isovolumic pressure-volume curve
What does the isovolumic pressure volume curve demonstrate?
That increasing preload enables the heart to generate more force
What does increasing afterload at a fixed preload do to the heart?
Decreases stroke volume
What will increasing preload do to the heart? What is this called?
Increase stroke volume - called the Frank Starling mechanism.
What will increasing contractility do to the heart? What accomplishes this?
Increase stroke volume, but NOT preload - just pumps more out.
Accomplished via Epi/NE and the sympathetic nervous system.
What is the relationship between compliance and distensibility?
As compliance increases, distensibility does as well.
How does increasing compliance affect the heart?
It makes it easier for the ventricles to fill so volume increases more.
what is the detrimental effect of decreased compliance?
The heart can't fill up with volume; hence it can't generate force to pump out either.
What are the 2 main types of regulation of heart pumping?
1. Intrinsic regulation
2. Autonomic neural regulation
What does Intrinsic regulation refer to?
The frank-starling mechanism
What is the Frank Starling Mechanism?
Within physiological limits the heart pumps all of the blood that comes into it without allowing excessive damming of blood in the vein.
What is Autonomic neural regulation composed of? (3 things)
-Sympathetic innervation
-Vagal innervation
-Circulating epinephrine
What happens to CO as BP increases to about 160 mm Hg?
CO remains constant
Above 160 mm Hg what happens to CO?
It decreases - afterload is just too much.
Which side of the heart does more work? How much more?
The left ventricle - does 10X more work than the right ventricle.
Why does the left Ventricle do 10X more work than right?
Because it's pumping agains MAP which is 100 mm Hg, compared to pulmonary pressure which is like 15 mm Hg.