Physio Ch 13

Question 1

Abnormalities in the rhythmicity-conduction system of the heart;

Answer 1

1. abnormal rhythmicity of the pacemaker
2. shift of the pacemaker from the sinus node to another place in the heart
3. blocks at different points in the spread of the impulse through the heart
4. abnormal pathways of impulse transmission through the heart
5. spontaneous generation of spurious impulses in almost any part of the heart

Question 2

means fast heart rate, that usually defined in an adult person as faster than 100 beats/min

Answer 2

Tachycardia

Question 3

Causes of Tachycardia

Answer 3

✓ increased body temperature
✓ stimulation of the heart by the sympathetic nerves
✓ toxic conditions of the heart

Question 4

it causes tachycardia because increased temperature increases the rate of metabolism of the sinus node, which in turn directly increases its excitability and rate of rhythm

Answer 4

Fever

Question 5

simple weakening of ___________ usually increases the heart rate because the weakened heart does not pump blood into the arterial tree to a normal extent

Answer 5

myocardium

Question 6

means a slow heart rate, usually defined as fewer than 60 beats/min

Answer 6

Bradycardia

Question 7

the most striking example of any circulatory reflex that stimulates the vagus nerves causes release of acetylcholine at the vagal endings in the heart, thus giving a parasympathetic effect

Answer 7

carotid sinus syndrome

Question 8

is an instrument that records by the height of successive spikes the duration of the interval between the successive QRS complexes in the electrocardiogram

Answer 8

cardiotachometer

Question 9

during ______________, the heart rate increased and decreased with each respiratory cycle by as much as 30 percent

Answer 9

deep respiration

Question 10

can result from any one of many circulatory conditions that alter the strengths of the sympathetic and parasympathetic nerve signals to the heart sinus node

Answer 10

sinus arrhythmia

Question 11

cause alternate increase and decrease in the number of impulses transmitted through the sympathetic and vagus nerves to the heart

Answer 11

spillover signals

Question 12

The only means by which impulses ordinarily can pass from the atria into the ventricles is through the?

Answer 12

A-V bundle

Question 13

A-V bundle also known as?

Answer 13

bundle of His

Question 14

Conditions that can either decrease the rate of impulse conduction in this bundle or block the impulse entirely are as follows;

Answer 14

1. Ischemia of the A-V node or A-V bundle fibers
2. Compress of the A-V bundle
3. Inflammation of the A-V mode or A-V bundle
4. Extreme stimulation of the heart by the vagus nerves

Question 15

often delays or blocks conduction from the atria to the ventricles

Answer 15

Ischemia of the A-V node

Question 16

by scar tissue or by calcified portions of the heart can depress or block conduction from the atria to the ventricles

Answer 16

Compression of the A-V bundle

Question 17

can depress conductivity from the atria to the ventricles.

Answer 17

Inflammation of the A-V node

Question 18

rare instances block impulse conduction through the A-V node.

Answer 18

Extreme stimulation of the heart by the vagus nerve

Question 19

usually decreases in length with faster heartbeat and increases with slower heartbeat

Answer 19

P-R interval

Question 20

In general, when the P-R interval increases to greater than 0.20 second, the P-R interval is said to be prolonged and the patient is said to have?

Answer 20

first-degree incomplete heart block

Question 21

period fainting spells are known as?

Answer 21

Stokes-Adams syndrome

Question 22

a small battery-operated electrical stimulator planted beneath the skin, with electrodes usually connected to the right ventricle

Answer 22

artificial pacemaker

Question 23

this means that ventricular excitability is at first in a suppressed state because the ventricles have been driven by the atria at a rate greater than their natural rate of rhythm

Answer 23

overdrive suppression

Question 24

results from partial intraventricular block every other heartbeat

Answer 24

electrical alternans

Question 25

A premature contraction is a contraction of the heart before the time that normal contraction would have been expected. This condition is called?

Answer 25

extrasystole, premature beat or ectopic beat

Question 26

Most premature contractions result from ___________ in the heart, which emit abnormal impulses at odd times during the cardiac rhythm

Answer 26

ectopic foci

Question 27

Possible causes of ectopic foci;

Answer 27

1. local areas of ischemia
2. small calcified plaques
3. toxic irritation of the A-V node, purkinje system or myocardium

Question 28

the interval between the premature contraction and the next succeeding contraction is slightly prolonged

Answer 28

compensatory pause

Question 29

disorders that delay depolarization of ventricular muscle following the action potentials and therefore excessively long Q-T intervals on the electrocardiogram

Answer 29

long Q-T syndrome (LQTS)

Question 30

The major reason that the long QT syndrome is of concern is that delayed repolarization of ventricular muscle increases a person’s susceptibility to develop ventricular arrhythmias called?

Answer 30

torsades de pointes

Question 31

literally means “twisting of the points”

Answer 31

torsades de pointes