Brainscape's Knowledge GenomeTM

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


See full index

CRRAB 1 Week 1 > Cardiac Muscle > Flashcards

Cardiac Muscle Flashcards

1
Q

What are the three ways cardiac muscle APs differ from skeletal muscle APs?

A

they’re self generating
they conduct directly from cell to cell
they have a long duration

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

What are the three most important ions for cardiac APs?

A

sodium, calcium, potassium

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

On what side of the membrane is sodium concentration higher? calcium? potassium?

A

sodium and calcium are higher in the interstitial fluid (so they want to move into the cell)

Potassium is high in th eintracellular fluid, so it wants to move out

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

What structures in the membrane are responsible for the resting membrane potential and rapid changes?

A

ion channels

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

What are the three possible states of ion channels?

A

open, closed, inactivated

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

What is the resting membrane potential for cardiac cells? Closes to what ion equilibrium?

A

-90 mV - which is potassium’s equilibirum

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

What are the two types of myocardial cells?

A

myocardial contractile cells

myocardial autorhythmic cells = pacemaker cells

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

Contractile cell APs are similar to neurons exept for what important difference?

A

much longer AP due to extended Ca2+ entry

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

How can pacemakers spontaneously generate APs?

A

their membrane potential is inherently unstable

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

Which cells produce the “slow response” and which produce the “fast response”

A

pacemaker cells = slow response

contractile cells = fast response

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

How many phases are there in a contractile cell AP?

A

5, but they’re numbered 0-4

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

For contractile cells, what is the first step in firing an AP?

A

the Na channels open and the K+ channels close. THis means K+ can’t leave the cell and Na+ rushes in. This causes a rapid depolarization.

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

For contractile cells, what happens at the peak - the overshoot?

A

the Na+ channels close and FAST K+ channels open. K+ is now wanting to enter the cell based on the electrochemical gradient - this is what makes the initial repolarization happen briefly.

It doesn’t last long though - the K+ channels close

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

After the fast K+ channels close, what opens?

A

the slow inward Ca2+ channels open. Ca 2+ enters the cell very slowly, halting the repolarization and causing the characteristic plateau

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

What causes the repolarization after the plateau?

A

the Ca2+ channels close and the delayed rectifier slow K+ channels open, allowing K+ to rush out of the cell causing the rapid repolarization

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

What slows the rapid repolarization such that the resting membrane is reached and maintained?

A

the slow K+ channels close and the inward rectifier channels open when you reach the K+ resting membrane potential

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

What current characterizes the pacemaker cells

A

the funny current

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

what are the phases of the apcemaker cell AP/

A

three phases: 0, 3, and 4 to coincide with the contractile

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

What makes the funny current funny?

A

both Na and K are going in and out

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

What causes the potential to gradually rise?

A

a gradual influx of Na

21
Q

When the potential reaches a threshold, what happens?

A

you have a transient opening of the Ca2+ channels and you get an influx of Ca2+ to further depolarize

22
Q

How does the influx of Ca2+ essentially sustain itself?

A

It triggers long-lasting Ca2+ channels to open

23
Q

What causes the depolarization to stop and then result in repolarization?

A

opening of the K+ channels so K leaves the cell

24
Q

So what ion primarily mediates phase 0 in contractile cells/ in pacemaker cells?

A

Na in contractile

Ca in pacemaker

25
Q

What keeps the contractile cells from going into summation or tetanus?

A

they have a really long refractory period

26
Q

What are the structures that connect the ends of two adjacent cardiac contractile cells?

A

intercalated disks

27
Q

In the intercalated disks, what forms the firm mechanical attachments?

A

desmosomes with adherens proteins

28
Q

In the intercalated disks, what causes the electrical connection between the cells?

A

gap junctions with channels formed by connexin proteins

29
Q

What do the gap junctions allow for?

A

THey allow positive charged ions to flow away from the depolarized membrane of the first cell over to the hyperpolarized membrane of the adjacent cell.

This triggers a depolarization in the adjacent cell, leading to an AP

30
Q

How do we measure electrical events of the cardiac cycle/

A

electrocardiogram

31
Q

What is happening during the P wave?

A

atrial depolarization

32
Q

What does the PR interval represent?

A

the conduction time through the atria and the AV node

33
Q

What is the QRS complex?

A

ventricular depolarization

34
Q

What is the QT interval?

A

the duration of ventricular systole, or contraction

35
Q

What does the ST segment signify?

A

duration of the plateau phase in the contractile cells

36
Q

What does the T wave represent?

A

ventricular repolarization

37
Q

Why can’t you see repolarization on an EKG?

A

Because is occurs during ventricular depolarization, which has the enormous QRS segment

38
Q

THe parasympathetic fibers from the vagus nerve release what NT? To what effect?

A

ACh
It increases the permeability of the resting membrane to K+, leading to a hyperpolarization - this means you have a slower rate of spontaneous depolarization - a negative chronotropic effect; heart slows down

39
Q

What do sympathetic fibers release? to what effect?

A

NE

it increases the spotnaneous depolarization of the membrane - a positive chronotropic effect; the heart speeds up

40
Q

What is the ion that really drives the actual contraction?

A

Ca2+

41
Q

What happens when you have an action potential in a contractile cell?

A

you get an opening of a voltage-gated Ca2+ channel, which allows Ca2+ to enter the cell

42
Q

What does the Ca2+ do in the cell?

A

It binds to ryanodine receptors on the sarcoplasmic reticulum, which triggers more Ca2+ channels to open, allowing stored Ca2+ to flow out of the SR into the cell further increasing Ca2+ concentration

43
Q

What does this high Ca2+ concentration cause in the cell?

A

It binds to troponin and allows actin and myosin to interact, leading to a cotnraction

44
Q

Why does relaxation occur?

A

Because Ca2+ will be pumped back into the SR and out of the cell after about 200 ms

45
Q

What’s the difference between isometric and isotonic contraction?

A

isometric is when the length is fixed by having the ends of hte muscle held rigidly - means it can develop tension but not shorten

Isotonic is when the tension is fixed - an unrestrained muscle causes it to shorten without force development

46
Q

Active tension developed during isometric contraction depens on what?

A

the muscle length at which contraction occurs

too short - no contraction
too long - no contraction
appropriate length is the most myosin-actin interactions possible = contraction

47
Q

What is an inotrope? Example?

A

something that influences the amount of tension the muscle can develop, or the amount of shortening a muscle can achieve

NE is a positive inotrope because it increases isometric tension

48
Q

Mechanical response of the myocyte depends upon what?

A

preload, afterload, and contractility

49
Q

Cardiac myocyte length-tension relationshipsa re correlated with what?

A

changes in volume and pressure in the intact ventricle

CRRAB 1 Week 1 (9 decks)

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