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Flashcards in Cardiac contraction Deck (17):
1

What does the SA node do?

spontaneously generates electrical potentials

2

Explain the pattern of conductance

SA node starts, activity goes rapidly to AV node, slow depolarization across the atria (conduction slows across the AV node), Rapid depolarization across the ventricle via the AV bundle. Depolarization spreads upward from the apex via the purkinjee fibers.

3

In health, do ventricles spontaneously depolarize?

No

4

Phases of ventricular action potential

know

5

What are the effects of the parasympathetic nervous system on the heart?

Decrease HR, Decrease conduction velocity, Decrease the excitability of latent
pacemakers.
Ex: Acetylcholine

6

Symapthetic activity effects on the heart?

Increase HR, Increase conduction velocity, Decrease the threshold of Calcium channels
Ex: Norepinephrine

7

What is the sequence of events regarding action potentials, intracellular calcium levels, and contraction

An action potential occurs, Intracellular calcium levels rise, contraction occurs

8

Strength of contraction is regulated by what?

Intracellular calcium levels during action potential
Initial strength of cardiac finbers which determines sensitivity to calcium

9

Intracellular calcium regulation

Cacium influx into cells
Calcium release from SR
Calcium uptake by SR
Calcium efflux

10

Catecholamines do what>

Accelerate the rate of cardiac contraction
Intracellular calcium decline
Cardiac relaxation

11

The greater the sarcomere length, the greater the contraction

true

12

Increased pre-load equals

inc stroke volume

13

How does the inc in length lead to increased cardiac force

A fast response to stretch, involving increased calcium sensitivity of myofibrils generated by stretch
A slow response to stretch involving activation of calcium channels by stretch

Basically, increasing length increases calcium sensitivity

14

What does the vagus nerve deliver to the heart?

parasympathetic innervation

15

What determines preload

End diastolic volume

16

Does changing afterload do anything to the contractility curve?

Nope

17

How do you compensate for increased afterload?

Increased contractilty or increased preload