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A & P > objective 3 pt 2 > Flashcards

objective 3 pt 2 Flashcards

1
Q

The intrinsic cardiac conduction system consists of
noncontractile cardiac cells specialized to initiate and
distribute impulses throughout the heart.
Although the heart depolarizes and contracts without
nervous system stimulation, the rhythm can be altered by
autonomic nervous system.

A

electrical events of the heart

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2
Q

what is the sequence of excitation?

A

Cardiac pacemaker cells pass impulses across heart in ∼0.22 seconds
◦ Coordinates depolarization of the heart
◦ Ensures heart beats as a unit

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3
Q

what is the order in which impulses pass across the heart?

A
  1. Sinoatrial (SA) node →
  2. Atrioventricular (AV) node →
  3. Atrioventricular (AV) bundle →
  4. Right and left bundle branches →
  5. Sub-endocardial conducting network
    (Purkinje fibers)
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4
Q

sets the pace of the heart as it depolarizes faster than
rest of myocardium

A

pacemaker

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5
Q

Located in right atrial wall
◦ Generates impulses about 75×/minute (sinus rhythm)
◦ Innate rate of 100×/minute tempered by extrinsic factors
◦ Impulse spreads across atria, and to AV node

A

sinoatrial node

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6
Q

Located in inferior interatrial septum
◦ Delays impulses approximately 0.1 second
◦ Allows atrial contraction to occur before ventricular contraction
◦ Inherent rate of 50x/minute in absence of SA node input
◦ From the AV node the impulse sweeps to the AV bundle

A

atrioventricular node

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7
Q

Located in superior interventricular septum
◦ Only electrical connection between atria and ventricles
◦ Atria and ventricles not connected via gap junctions
◦ The AV bundle splits into the rt. and lt. bundle branches

A

antrioventricular bundle

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8
Q

Found in interventricular septum
◦ Carry impulses toward apex of heart

A

right and left bundle branches

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9
Q

Extends from interventricular septum into apex and ventricular walls
◦ More elaborate on left side of heart due to size of LV
◦ Process from initiation at SA node to complete contraction takes
~0.22 seconds
◦ Ventricular contraction immediately follows the depolarization wave

A

sub-endocardial conducting network

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10
Q

sends signals
through sympathetic nervous system to
increase both rate and force of contraction
◦ Stimulates SA and AV nodes, heart muscle,
and coronary arteries

A

cardio-acceleratory center

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11
Q

sends
parasympathetic signals via vagus nerve to
decrease heart rate
◦ Inhibits SA and AV nodes via vagus nerves

A

cardio-inhibitory center

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12
Q

is a device that
can detect electrical currents
generated by heart

A

electrocardiograph

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13
Q

is
a graphic recording of electrical
activity
◦ Combination of all action
potentials at given time; not a
tracing of a single AP
◦ Electrodes are placed at various
points on body to measure
voltage differences
◦ 12 lead ECG is most typical

A

electrocardiogram

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14
Q

what are the main features of electrocardiography?

A

P wave
QRS complex
T wave
P-R interval
S-T segment
Q-T interval

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15
Q

depolarization of atria

A

P wave

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16
Q

ventricular depolarization

A

QRS complex

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17
Q

ventricular repolarization

A

T wave

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18
Q

beginning of atrial excitation to beginning of ventricular excitation

A

P-R interval

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19
Q

entire ventricular myocardium depolarization

A

S-T segment

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20
Q

beginning of ventricular depolarization through ventricular repolarization

A

Q-T interval

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21
Q

may be due to enlarged ventricles

A

enlarged R wave

22
Q

could be cardia ischemia

A

elevated or depressed ST segment

23
Q

could be repolarization abnormality that increases risk of ventricular arrhythmias

A

prolonged QT interval

24
Q

period of heart contraction

A

systole

25
Q

period of heart relaxation

A

diastole

26
Q

blood flow through heart during one heartbeat
Atrial systole and diastole are followed by ventricular
systole and diastole
◦ Cycle represents series of pressure and blood volume
changes
◦ Mechanical events follow electrical events seen on ECG
◦ Cycle lasts ~ 0.8 secs

A

cardiac cycle

27
Q

marked by a succession of pressure and blood volume changes in the heart

A

cardiac cycle

28
Q

what are the phases of the cardiac cycle?

A
  1. Ventricular filling (atrial systole)
  2. Isovolumetric contraction
  3. Ventricular ejection
  4. Isovolumetric relaxation
29
Q

Contraction of atria completes emptying blood
out of the atria into the ventricles
o AV valves are open; SL valves are closed
o Ventricles are relaxed (diastole) and filling with
blood
o Cycle begins with P wave of ECG
o Takes ~ 0.1 sec

A

atrial systole

30
Q

As the atria relax, the ventricles begin contracting
◦ Begins with QRS complex
◦ AV and SL valves are closed
◦ Pressure increases rapidly but volume remains
same
◦ For a split second, the ventricles are completely
closed chambers and the blood volume remains
constant as the ventricles contract

A

isovolumetric ventricular contraction

31
Q

Onset coincides with R wave and appearance of 1st heart
sound
◦ AV valves closed
◦ SL valves open
◦ Blood forcefully ejected into pulmonary artery and aorta
◦ T wave occurs just before ventricles relax
◦ Residual volume
◦ End-systolic volume
◦ Takes ~ 0.3 secs

A

ventricular systole

32
Q

SL valves close (2nd heart sound)
o AV valves are closed
o All chamber relax simultaneously for ~ 0.4 sec
o Atria passively fill with blood

A

isovolumetric ventricular relaxation

33
Q

what are the 2 sounds of the heart?

A

lub
dub

34
Q

first sound is the closing of AV valves at beginning of ventricular systole

A

Lub

35
Q

second sound is closing of SL valves at beginning of ventricular diastole

A

Dub

36
Q

the volume of blood pumped by each ventricle in 1 min

A

cardiac output

37
Q

number of beats per min

A

HR

38
Q

amount of blood pumped out by one ventricle with each beat

A

SV

39
Q

factors increase heart rate

A

positive chronotropic factors

40
Q

factors decrease heart rate

A

negative chronotropic factors

41
Q

what can HR be regulated by?

A

autonomic nervous system
chemicals
other factors

42
Q

can be activated by emotional or physical stressors. upon activation norepinephrine is released

A

sympathetic nervous system

43
Q

increases HR
increased contractility

A

norepinephrine

44
Q

opposes sympathetic effects. upon activation acetylcholine is released

A

parasympathetic nervous system

45
Q

slows HR but has little to no effect on contractility

A

AcH

46
Q

The hormones Epinephrine and Thyroxine influence heart rate.
o Epinephrine increases heart rate and contractility
o Thyroxine increases heart rate and enhances effects of epinephrine
and NE
o Intracellular and extracellular ions influence normal heart function

A

chemical regulation of heart rate

47
Q

fetus has fastest HR; declines with age

A

age

48
Q

females have faster HR than males

A

gender

49
Q

increases HR
trained athletes can have slow HR

A

exercise

50
Q

HR increases with increased body temp

A

body temp

A & P (21 decks)

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