Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

PHSL 232 > L3 > Flashcards

L3 Flashcards

1
Q

what are membranes highly permeable to

A

K+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is the membranes permeability for Na+ and Ca+

A

it has a low permeability to Na+ (about 10%) and a very low permeability to Ca+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is another name for conduction

A

depolerisation wave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

name the structures in the conduction system

A

sinoatrial node (SA) - origin of the action potential

atrioventricular node (AV)

bundle of hiss

purkinje fibers

cardiomyocytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

where is the AV node located

A

it boundaries the atria and the ventricles

this is where the fibrocartilaginous structure are in the heart (AV valves)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is the role of the AV node

A

it acts as an insulator

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

describe the conduction pathway

A

it starts in the SA node. it travels through the atria to the AV node

after it passes through the AV node it passes through the bundle of hiss into the left and right bundle branches

it then travels down the septum, into the purkinje fibers

the purkinje fibers wrap around the heart and going individual cardiomyocytes which all communicate with each other via gap junctions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is special about cardiomyocytes that allow them to conduct APs

A

they are interwoven and have branched ends.

the ends contain intercalated discs which allow for cell to cell communication (via gap junctions)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is a functional syncytium

A

cells that are very tightly bound together

this means that cardiomyocytes have an all or nothing contraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

at what rate does the SA node generate action potentials

A

100 min-1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is the speed of conduction through the atria

A

0.5m/s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what os the speed of conduction through the AV node

A

0.05m/s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

why is conduction through the AV node slower than it is through the atria

A

because the delay permits full depolerisation and contraction of the atria before depolerisation and contraction of the ventricles

it lets the ventricles fill with blood before it contracts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what does the contraction of the atria represent

A

atrial top up

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the speed of conduction in the bundle of hiss, bundle branches and purkinje fibers

A

5m/s

this is VERY quick for the distance that it is traveling meaning that the speed of ventricular contraction is mostly dependent on the contraction of the myocardium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is the speed of conduction in the ventricular myocardium

A

0.5m/s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what do all the different speeds of conduction allow for

A

synchronous depolerisation and contraction of all ventricular regions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

the speed of conduction spreads slowest in the……

A) SA node
B) Atria
C) AV node
D) Bundle of Hiss

A

C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is the difference in action potentials in pacemaker cells compeered to ventricular cells

A

pacemaker cells are the origin of action potentials. they are located in the SA node and are known as the leaders

ventricular cells (cardiomyocytes) are known as the flowers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what are the 3 phases of the pacemaker cell

A

phase 4
phase 0
phase 3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

explain phase 4 of a pacemaker cell

A

phase 4 is the equivalent of the cell being at RMP (-60 to -70mV) however the membrane is not resting as it is always becoming more up and down

this is because pacemaker cells have funny Na+ channels which cause a slow influx of Na+

the slow influx of Na into the cell causes T-type Ca2+ channels (TTCC) to open in the later end of phase 4 causing Ca2+ to enter the cell

the cell then reaches threshold which is about -50 to -40 mV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what happens when the pacemaker cell reaches threshold

A

L-type Ca2+ channels (LTCC) open

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what is phase 0 of a pacemaker cell

A

this phase is also known as the upstroke

L-type Ca2+ channels (LTCC) open

this causes a rapid influx of Ca2+ into the cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is phase 3 of a pacemaker cell

A

this is when the Ca2+ channels close (and the Na+ channels as much as they can) and repolarisation starts to happen SLOWLY because of K+ diffusing through the membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

why do pacemaker cells have weird phase names

A

because they are based of what the ventricular cells are doing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

how many phases do ventricular cells have

A

5

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what phase is at RMPin a ventricular cell

A

4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

describe phase 4 of a ventricular cell

A

unlike the pacemaker cells this phase is very stable with a very negative RMP of -90mV

this is because the membrane is VERY permeable to K+

29
Q

describe phase 0 of a ventricular cell

A

it is the fast and rapid depolerisation of the cell

this happens because of the opening of fast Na+ channels

30
Q

what is the threshold of ventricular cells

A

-65mV

31
Q

what is another name for phase 1 in a ventricular cell

A

early repolarization

32
Q

describe early repolarization of a ventricular cell

A

this is when the fast Na+ channels close because they become inactivated but the membrane is still very permeable to K+ therefore the cell get slightly more -ive

33
Q

what is another name for the plateau phase of a ventricular cell

A

phase 2

34
Q

what happens in phase 2 of a ventricular cell

A

this is when L-type or voltage operated Ca2+ channels open

this causes the plateau because of sustained depolerisation as the Ca2+ coming in balances the K+ Efflux

at the end of this phase the L-type channels close which causes phase 3

35
Q

what is phase 3 of a ventricular cell

A

it is the late repolarisation

the LTCC channels close and K+ Efflux which causes a fast repolerisation

36
Q

why does an ECG look the way it does

A

the ECG is the combination of all of the different action potentials in the conduction system that happen over the time leading up to the contraction

37
Q

in ventricular cells, slow depolerisation occurs through funny Na channels BECAUSE the resting membrane potential of ventricular cells is stable around -90mV

A

the first is false and the second is true

38
Q

what is the physiological basis for ECG

A

different APs at different locations in the hearts at different times

39
Q

what is an ECG

A

a recording of potential changes at the skin surface that result from depolarisation and repolarisation of the heart

40
Q

the scale of electrical recordings from inside the cells of the heart differ greatly from the scale of an ECG why is this

A

inside the cell is about 100mV and an ECG recording is about 1mv

this is because an ECG is taken from the body surface therefore most of the amplitude is lost

41
Q

what does an ECG allow you to measure

A

the electrical activity of the heart

and

the direction of relative size of potential changes

42
Q

where are the electrodes placed for an ECG

A

the right arm, left arm and left leg

43
Q

where are the charges on lead 1

A

-ive on the right and +ive on the left arm

44
Q

where are the charges on lead 2

A

-ive on right arm and + on left leg

45
Q

where are the charges on lead 3

A

+ on left leg and - ive on left arm

46
Q

the combination of 2 electrodes is called a what

A

bipolar lead

47
Q

what are Einthoven’s standard limb leads

A

leads 1, 2, and 3

48
Q

what is Einthoven’s triangle

A

leads 1, 2, and 3

49
Q

the ECG that gives you the picture that you always think about is taken from what lead

A

lead 2

50
Q

describe what causes the ECG to look the way it does when using lead 2

A

imagen a camera sitting at your left hip and it is looking down lead 2

when depolerisation is coming towards the camera which causes a positive deflection and when it is moving away from the camera it causes a negative deflection

repolarisation is the opposite

51
Q

what causes you to see the P wave in lead 2

A

SA cells depolarise which causes the right and left atria to depolarise towards the AV node

towards AV node = towards + electrode therefore you get positive deflection (the P wave)

52
Q

what causes you to see the Q wave in lead 2

A

in the ventricular septum the overall direction of the depolerisation is slightly away from the +ive electrode therefore you get a slight negative deflection

53
Q

what causes you to see the R wave in lead 2

A

ventricular depolarisation from ‘inside to outside’

the bottom of the ventricles contract before the top

therefore these is a large depolerisation towards the +ive electrode causing a large positive deflection

54
Q

what causes you to see the S wave in lead 2

A

this is late ventricular depolerisation. since now the top of the ventricles are contracting the depolerisation is away from the +ive electrode.

this is only small therefore it causes a small negative deflection

55
Q

what causes you to see the T wave in lead 2

A

repolerisation of the ventricles goes from outside to inside

therefore repolerisation is happening away from the +ive electrode causing a positive deflection

56
Q

why is atrial repolerisation not shown on the ECG

A

because atrial repolerisation is very small therefore it is hidden by the large ventricular depolerisation

57
Q

what are augmented limb leads

A

when you create 3 more views without adding any more leads on you

58
Q

what are the names of the augmented limb leads

A

aVR - augmented lead right
aVL - augmented ead left
aVF - augmented lead fount

59
Q

what does aV in the augmented leads stand for

A

augmented voltage (thats measured)

60
Q

are the augmented lead bipolar

A

no

they are unipolar

61
Q

what is aVR

A

it is lead 3 with another lead coming from the middle connected to a +ive electrode on the right hand

62
Q

what is aVL

A

it is lead 2 with another lead coming from the middle connected to a +ive electrode on the left hand

63
Q

what is aVF

A

it is lead 1 with another lead coming from the middle connected to a +ive electrode on the left foot

64
Q

the augmented leads plus the einthoven (standard) limb leads creates what kind of system

A

hexaxial reference system

65
Q

what does the hexaxial reference system allow you do to

A

to see the position of your heart as there is a large variance between each person

the position can range from the apex pointing at your left arm to your right hip

it also allows you to see APs at different location s in the heart at different times

66
Q

which is the only lead with a negative deflection

A

aVR

67
Q

what are chest leads

A

active electrodes in one of 6 positions on the chest

V1, V2, V3, V4, V5, V6

68
Q

what is a common characteristic between all of the chest leads

A

they all have large ECG deflections

69
Q

what plane do chest leads examine the plane in

A

the horizontal plane

PHSL 232 (30 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions