Excitation of the Heart

Question 1

The atria conduct ___ seconds faster than the ventricles

Answer 1

0.16s (1/6 of a second)

Question 2

The excitatory conductive system is located in the superior posterolateral wall of the ______

Answer 2

right atrium

Question 3

Fibers of the excitatory conductive system have almost no what?

Answer 3

contractile muscle filaments

Question 4

Fibers of the excitatory conductive system connect directly with what type of muscle fibers?

Answer 4

atrial

Question 5

The AV node is located on the posterior wall of the right ____ behind the ____ valve

Answer 5

atrium; tricuspid

Question 6

The AV node causes ___ conduction and delay, which contribute to both physiology and function

Answer 6

slow

Question 7

AV node causes rapid transmission in which system?

Answer 7

Ventricular purkinje system

Question 8

The velocity of the AV node action potential is ____x of the ventricular fibers and ____x that of AV nodal fibers

Answer 8

6x; 150x

Question 9

Action potentials are not able to travel which direction from the ventricles to the atria?

Answer 9

backwards

Question 10

Action potentials are not able to travel backwards from the ventricles to the atria in order to prevent re-entry of what?

Answer 10

cardiac impulses

Question 11

Re-entry of cardiac impulses from the atria to the ventricles can cause serious what?

Answer 11

arrhythmias

Question 12

Impulse spreads at a moderate velocity through the ____ and is delayed more than 0.1s in the ___ nodal region

Answer 12

atria; AV

Question 13

Impulses then spread very rapidly through the ____ fibers to the ___ surfaces. They spread less rapidly through the ventricular muscle to the ___ surfaces

Answer 13

purkinje
endocardial
epicardial

Question 14

The purkinje system has ___ conduction and ____ contraction

Answer 14

rapid; synchronous

Question 15

Which node is considered the normal pacemaker of the heart?

Answer 15

SA node

Question 16

Which fibers discharge at an intrinsic rhythmical rate rate of 40-60x per minute (when not stimulated by an outside source)?

Answer 16

AV nodal fibers

Question 17

Which fibers discharge at a rate somewhere between 15-40x per minute?

Answer 17

purkinje fibers

Question 18

Which abnormal pacemaker will cause fainting after 4-5 seconds due to a sudden AV block?

Answer 18

Stokes-Adam syndrome

Question 19

Which abnormal pacemaker causes an abnormal sequence of contraction of the different parts of the heart causing significant heart pump debility?

Answer 19

Ectopic pacemaker

Question 20

The effect of Acetylcholine on the heart ____ the rate of rhythm in the sinus node and ____ excitability of the AC junctional fibers

Answer 20

decreases; decreases

Question 21

Decreasing the excitability of the AV junctional fibers between the atrial musculature and the AV node will cause what?

Answer 21

slowing transmission of the cardiac impulse in the ventricles

Question 22

Acetylcholine increases the permeability of what?

Answer 22

fiber membranes to K+ ions

Question 23

Acetylcholine allows for rapid leakage of what?

Answer 23

K+ ions out of conductive fibers

Question 24

Acetylcholine increases the ___ inside the fiber

Answer 24

negativity

Question 25

Hyperpolarization is caused by

Answer 25

mechanisms of vagal effects (acetylcholine)

Question 26

The tissue is ___ excitable in mechanisms of vagal effects (acetylcholine)

Answer 26

less

Question 27

Ventricular Escape is when a strong vagal stimulation can stop rhythmical excitation by 2 things, which are what?

Answer 27

1. Blocking the sinus node

2. Blocking the transmission of the cardiac impulse from the atria into the ventricles via AV-node

Question 28

When the ventricles stop beating for 5-20 seconds and the purkinje fibers develop a rhythm of its own, causing ventricular contraction of 15-40bpm, what is this called?

Answer 28

Ventricular Escape

Question 29

Sympathetic stimulation increases the rate of _____ discharge, the rate of ____, the level of _____ in all portions of the heart and the force of contraction of all cardiac musculature, both in ____ and ____

Answer 29

sinus nodal
conduction
excitability
atrial and ventricular

Question 30

What are the mechanisms of sympathetic effects (5)?

Answer 30

1. Norepinephrine (NE)
2. NE stimulates B-1 andrenergic receptors
3. Increases permeability of fiber membrane to sodium and calcium ions
4. More positive membrane potential
5. Tissue is more excitable

Question 31

Norepinephrine stimulates what kind of receptors in the sympathetic system?

Answer 31

B-1 andrenergic receptors

Question 32

Norepinephrine increases the permeability of fiber membrane to what 2 ions?

Answer 32

sodium and calcium

Question 33

NE causes a more ____ membrane potential

Answer 33

positive

Question 34

NE causes the tissue to be more ____

Answer 34

excitable

Question 35

Where are normal rhythmical impulses generated?

Answer 35

SA node

Question 36

A decrease in gap junctions causes what delay?

Answer 36

AV delay

Question 37

An AV delay allows for the atria to empty their blood into the ventricles before what begins?

Answer 37

ventricular contraction

Question 38

What allows for rapid conduction for full/synchronous contraction of the ventricles?

Answer 38

purkinje fibers

Question 39

Parasympathetic activity releases what neurotransmitter?

Answer 39

Acetylcholine

Question 40

Parasympathetic activity decreases the rate of what node?

Answer 40

SA node

Question 41

Parasympathetic activity decreases the excitability of the AV junctional fibers between what 2 structures?

Answer 41

Atria and AV node

Question 42

Sympathetic activity releases what neurotransmitter?

Answer 42

Norepinphrine

Question 43

Sympathetic activity increases the rate of what node?

Answer 43

SA node

Question 44

Sympathetic activity increases the contractile strength of the cardiac muscle through increased permeability of what ion?

Answer 44

calcium