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Human Physiology > Lecture 14 > Flashcards

Lecture 14 Flashcards

1
Q
A
  1. SA node (Sinoatrial)
  2. AV node (Atrial Ventricular)
  3. Bundle of HIS
  4. Right and left bundle branches
  5. Purkinje system
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2
Q

a bundle of cardiac muscles is called _______ and connect to each other by __________

A

myocytes
intercalated discs

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3
Q

each disc has _____ connecting the cells

this allows ________ facilitating spread of the action potential from one cell to the next allowing rapid ________ depolarization

A

gap junctions

diffusion of ions
synchronous

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4
Q

in the conduction system cardiac muscle responds to the electrical impulses generated by the pacemaker cells (_______).

Cardiac action potentials can:
Be ____- generating
Be conducted ___________
Have ____ duration

A

SA node

self generating
directly from cell to cell
long

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5
Q

normally the heart rate systole is ___ percent and diastole is ____%

A

40%
60%

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6
Q

when heart rate is increased, the cardiac cycle is ______ and systole become ____%

A

decreased
65%

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7
Q

two bad things that can happen from increased heart rate

A

reduced ventricular filling time
reduced cardiac perfusion

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8
Q

Ischemia of a major coronary vessel can cause damage to the conducting system of the heart, called a _______.

Impulses from SA node are partially or completely obstructed at the _______ of his level

A

heart block

AV note/ bundle

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9
Q

Primary electrical event of the heart
Myocardial cell loses internal negativity
Transmit electrical impulse resulting in myocardial contraction

A

depolarization

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10
Q

“Membrane pumps” reverse flow of ions restoring polarity
Relaxation, recovery phase
The muscle returns to steady state

A

Repolarization

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11
Q

Excess internal negativity more negative than baseline.

A

Hyper-polarization

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12
Q

The ability of cardiac pacemaker cells to generate their own electrical impulses

A

automaticity

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13
Q

Irritability, the ability of the cardiac cell to respond to an electrical stimulus

A

excitability

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14
Q

ability of conducting system fibers to produce an automatic rhythmical discharge and contraction

A

Self-excitation

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15
Q

The ability of cardiac cells to receive an electrical stimulus and then transmit it to other cardiac cells

A

Conductivity

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16
Q

The ability of cardiac muscle to contract in response to an electrical stimulus

A

Contractility

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17
Q

The period during the action potential when a normal cardiac impulse cannot re-excite an already excited area

A

Refractory Period

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18
Q

Normal refractory period of ventricle:________

A

0.25 to 0.3s

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19
Q

normal baseline is around____

A

-70 mV

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20
Q

At resting state myocardial cell is __________
Electronegative inside (_____mV)

A

polarized
-85 mV

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21
Q

Three most important ions/channels in cardiac membrane potential

A

Sodium (Na+)
Calcium (Ca++)
Potassium (K+)

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22
Q

At rest, Sodium (Na+) Channels are…

A

greater outside cell
fast and slow sodium channels

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23
Q

At rest, Calcium (Ca++) Channels are…

A

greater outside cell
slow calcium channels

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24
Q

At rest, Potassium (K+) Channels are…

A

greater inside cell
potassium channels

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25
Q

all channels at rest are _____

A

closed

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26
Q

what opens first

then what happens

A

sodium and calcium

they close and potassium opens

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27
Q

“Muscle contraction” facilitating _____ function
At rest, regulatory proteins ______________ interfere with cross bridging of _____________

As cell depolarizes, _____ enters the cell and couples with ________
Promotes cross bridging resulting in cell contraction

A

pump
troponin/tropomyosin
actin and myosin

Ca++
troponin C

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28
Q

What has highest frequency of spontaneous firing?
how much per minute?

A

SA node
72/min

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29
Q

AV node fires at _______

Ventricles at _____

A

40/min

30/min

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30
Q

the conducting system consists of _____ and _______

A

nodal tissue
conducting fibers

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31
Q

initiates the heart beat and coordinates contractions of the four chambers

A

nodal tissue

32
Q

conduct impulses rapidly to different areas of the heart

A

conducting fibers

33
Q

what has very slow conduction velocities?
what has fastest?

A

SA and AV node

purkinje system

34
Q

Sinoatrial (SA) Node is a strip of conductive tissue at __________
SA node initiates and regulates the impulse for contractions of the heart
The impulse spreads through the ______________ via the ________________

Rate __________

A

right atrium

musculature of both atria
interatrial bundle toward the AV node

60-100 bpm

35
Q

Atrioventricular (AV) Node is located along the ___________

______ transmission by _____ from ____ to _______ due to the reduction of gap junctions and passes them to the ____________

Intrinsic rate _______

A

posterior inferior wall of Right Atrium

delays
0.13 seconds
atria
ventricles
AV bundle of HIS

40-60 bpm

36
Q

Why is it important for the AV node to slow the Action Potential?

A

so that both ventricles can fill up before the blood is forced out

37
Q

What causes the slowing of signal?

A

less gap junctions

Increases resistance to conduction of one fiber to the next

38
Q

What is the bundle of HIS

A

Group of modified muscle fibers that conduct impulses

39
Q

bundle of HIS arises in ________ and continues in the ________ as a single bundle

Splits into __________ that branch into ______

A

AV node
interventricular septum

right and left branches
terminal conducting fibers (Purkinje fibers)

40
Q

Purkinje fibers spread out into the ________
- _______ depolarizes first, then ______, _______, ______.

A

ventricle walls

septum
apex
left ventricle
right ventricle

41
Q

perking system is terminal ventricular conducting fibers on the __________ surface of the _______

A

endocardial surface

ventricles

42
Q

perking system has intrinsic rate of _______ and is _______ and ______.

A

15-40bpm
“idioventricular”
Non-perfusing

43
Q

How do these purkinje fibers have a faster conduction?

A

larger fibers
believed to have a higher permeability of the gap junctions

44
Q

Why does the SA node control the heart?

A

Fires the fastest

Override AV node and Purkinje fiber by depolarizing them before self depolarization

AV node and Purkinje fibers act as back up generators when SA node fails

45
Q

Pattern of Ventricular Conduction

A

Starts with initial septal depolarization

Impulse travels to apex

Impulse is distributed to both ventricles - left then right

Total time it takes 0.03 sec (very short)

Almost simultaneous contraction!!

46
Q

action potentials are a result of transient changes in ionic permeability of cell membrane, triggered by initial ___________

Typical nerve: ____
Skeletal muscle cell: _____
Cardiac cell: ______

A

depolarization

1 ms
2-5 ms
200 to 400 ms

47
Q

what are the 2 types of action potentials

A

fast response
slow response

48
Q

what has fast response

A

ventricular
atrial muscles
purkinje fibers

(more of a spike)

49
Q

what has a slo response

A

SA
AV

50
Q
A

nodal type

51
Q
A

atrial type

52
Q
A

ventricular type

53
Q

Ventricular Action Potential
- Phase 0 is _________

what occurs?

A

ventricular depolarization

Mediated by sodium (Na+) entry into the cells due to an increase in the number of open fast sodium channels in the cell membrane
Inside of the cell becomes less negative and the difference of the charge decreases

54
Q

ventricular action potential
- Phase 1 is ______

what occurs?

A

partial ventricular repolarization (spike in graph)

Potassium (K+) exits from the cells as the sodium channels are closed and the potassium channels open

55
Q

Phase 2 of ventricular action potential is the _____

what occurs?

A

plateau

slow entry of calcium into cells
counteract effects of potassium
- levels out charge

56
Q

phase 3 of ventricular action potential is ________

what occurs?

A

rapid ventricular repolarization (downhill)

potassium permeability is highest

potassium exits from the cells as the sodium channels are closed and the potassium channels open

57
Q

phase 4 of ventricular action potential is _____

what occurs?

A

recovery

sodium leaves and potassium re-enters the cell

58
Q

atrial action potential
- average velocity of conduction through the atrial muscle is ______
- Similar to ventricular
- Phase 2 (Plateau) is ____________
- Phase 3 (Repolarization) is more ______

A

0.3m/sec

narrower due to smaller Ca++ influx
gradual

59
Q

what is the source of the pacemaker?

A

hyperpolarization (SA node)

60
Q

In hyper-polarization, between heartbeats, ____ ions slowly leak into the cell causing a slow ____ in resting membrane potential toward the _______ direction. When it reaches _______ the _____ channels become activated and cause AP

The channels then become rapidly inactivated while simultaneous___ diffuses out-both of these _______ intracellular potential back to _____.
Resting membrane potential reaches __________

A

sodium
rise
positive (slow Na+ channel stays open)

-40mvs
calcium

K
reduce
negative
-55 to -60mvs

61
Q

the reason there is a flat line is because ?

A

calcium movement

62
Q

75 percent of parasympathetic comes from ______

A

vagus nerve

63
Q

the sympathetic system with the heart has signal and it moves through the _____, particularly the _____. This is sent to the ______ and ___________ rate of rate.

A

ganglia
T1 and T5
SA, AV, atrial and ventricular myocardium
increase

64
Q

parasympathetic innervation signal is sent to ____ and ____

A

SA and AV nodes
and atrial myocardium

65
Q

Sympathetic Nervous system
- signals come from spinal cord between _____ levels
- stimulates _____________________________
- supplies_______ sensory fibers which are sensitive to _____

Epi: stimulates alpha-, beta1-, and beta2-adrenergic receptors resulting in:
Cardiac stimulation
Increases heart rate (+chronotropic effect)
Increases force of contraction (+Inotropic effect)
Stimulation can increase CO 100%

A

T1-T5
SA and AV nodal tissue, atrial and ventricular myocardium
visceral
ischemia (makes it more sensitive to pain)

66
Q

epinephrine stimulates ____, _____, and ____ adrenergic receptors resulting in cardiac ______, _____ in heart rate, _____ in force of contraction, and can _____ CO 100%.

A

alpha
beta1
beta2

cardiac stimulation
increase heart rate
increase force
increase CO

67
Q

Parasympathetic NS

75 % of pre-ganglionic vagal fibers originating in the __________

____ binds to _________ receptors of SA node, AV node, and specialized conducting tissues atrial myocardium

Myocardial depressant
- ________ rate
- ________ force of contraction

A

medulla oblongata
Ach
muscarinic

decreases
reduces

68
Q

order of a heart pound on an EKG

A

PQRST

69
Q

P=___________
T=____________
QRS=__________

A

atrial contraction
ventricular repolarization
ventricular contraction

70
Q
A
  1. P
  2. Q
  3. R
  4. S
  5. T
  6. PR segment
  7. ST segment
  8. PR interval
  9. QT interval
  10. QRS complex
71
Q

EKG records ______________

A

atrial and ventricular depolarization and repolarization

72
Q

EKG baseline is called _______

A

isoelectric baseline

73
Q

interval area on EKG that includes a waveform and connecting straight line (_________) is the _________________.

A

isoelectric line

PR interval
QT interval

74
Q

line between to waves is _______ and includes ______________

A

segment

ST segment
PR segment

75
Q

Atrial depolarization is the ______ on the EKG and measures what two pathways?

A

P wave

Internodal
- anterior, middle posterior pathway

interatrial pathways
- Bachman’s bundle

76
Q

what is not seen on EKG

A

atrial depolarization

77
Q

During Ventricular Depolarization a conduction system consists of large fibers transmitting impulses at __________

current goes to ______, which divides into two bundles. then ______ deliver current into myocardium

A

1.5-4 m/sec

bundle of HIS
purkinje fibers

Human Physiology (24 decks)

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