Brainscape's Knowledge GenomeTM

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


See full index

Cardiovascular Pharmacology > Inherent Properties of Cardiac Muscle > Flashcards

Inherent Properties of Cardiac Muscle Flashcards

1
Q

What is excitation contraction coupling?

A

the linking of the electrical excitability of a cell to its ability to generate force

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

Why are the issues when disease occurs in the heart?

A

ventricular myocytes do not divide and are not replaced

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

What are the features of cardiac muscle?

A

cannot fatigue

is enriched with large mitochondria

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

What is the sarcomere?

A

the single basic unit that the muscle is made up of

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

What is the distance between two Z disks?

A

2 microns

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

What is attached to the Z disk?

A

actin

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

What is the m-line?

A

the point where myosin is attached

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

Where are t-tubules found?

A

along the surface membrane diving down around the z-disks

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

What shape are ventricular myocytes?

A

brick shaped

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

Why are cardiac muscle fibres branched?

A

allows them to make contact with numerous neighbours

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

Why is the refractory period important?

A

prevents cardiac muscle from tetanising

protects against re-entrant arrhythmias

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

What prevents the heart from filling with blood properly?

A

any excitation outside the regular beat prevents the heart from filling with blood

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

What the three general states of most ion channels?

A

open
closed
inactivated

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

transition to the inactivated state is dependent on what?

A

time - the ion channel will inactivate after a certain amount of time

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

transition to the closed state is dependent on what?

A

voltage - it will happen when the membrane repolarises

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

What is unique about cardiac muscle compared to skeletal muscle?

A

it requires calcium to initiate contraction

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

What is the calcium transient?

A

the rise in IC Ca that gives rise to contraction after a delay

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

What is the resting Ca level?

A

100nM

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

What is the peak of Ca during a transient?

A

1uM

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

What are some of the properties of each dyad?

A

10-25 L-Type Ca channels

100-200 RyRs

21
Q

What is a dyad?

A

the structure where the t-tubule meets the SR in the myocyte Z line

22
Q

How long does it take for Ca to rise in the cell?

A

30ms

23
Q

How is Ca removed from the cytoplasm?

A

SR CaATPase (SERCA) and the sarcolemmal Na/Ca exchanger - RELAXATION

24
Q

What aids the uniform and simultaneous release of Ca across the cell?

A

the t-tubule network

25
Q

What are the 3 accessory proteins of Actin?

A

tropomyosin I, TnT, TnC

26
Q

What is required to release the myosin head from actin?

A

ATP

27
Q

What happens in the absence of ATP?

A

myosin head remain attached and form rigor bonds

28
Q

What does Ca do to allow contraction?

A

binds TnC

29
Q

What does Ca binding TnC do?

A

changes the conformation pulling the tropomyosin out of the groove between actin filaments
exposes myosin binding site

30
Q

What does the continued cycle with ATP, Ca, Myosin and Actin do?

A

pulls the sarcomere together

31
Q

What is the state of TnI, TnC and Actin at rest?

A

TnC weakly interacts with TnI
TnI strongly interacts with Actin
troponin/Tropomyosin complex blocks myosin/actin interaction

32
Q

What is the state of TnI, TnC and Actin in the presence of Ca?

A

TnC interacts with TnI and destabilised interaction with actin
Removes steric hindrance to actin-myosin
activates the ATPase activity of myosin

33
Q

How far to the filaments slide per cross-bridge cycle?

A

5-10nm

34
Q

What is the length tension relationship?

A

the basis of the Frank-Starling Law of the Heart

  • amount of force generated depends on the how stretched the muscle is
  • the more stretched the muscle, the greater the force
35
Q

What does increasing sarcomere length initially do?

A

facilitates the overlap between thick and thin filaments and increases the no. of cross-bridges that can form

36
Q

What is the maximal length where the overlap between thick and thin filaments is facilitated?

A

2.25uM

37
Q

what do changes in overlap account for in cardiac muscle?

A

20% of the increase of force over the physiological range of sarcomere lengths

38
Q

what does increasing sarcomere length do?

A

increase Ca sensitivity and maximally activated force

39
Q

What is the effect on Ca sensitivity mediated by?

A

an increase in sensitivity of TnC for Ca

40
Q

What does increasing sarcomere length do?

A

increase cross-bridge overlap

increased Ca sensitivity of myofilaments

41
Q

When increased cardiac frequency, what happens?

A

the SR content increases and the force of contraction increases

42
Q

Why does the SR content increase with increased bpm?

A
  • L-type channels open more frequently and thus there is more Ca per second
  • some of the extra Ca is sequestered in the SR stores
  • bigger stores = bigger Ca release = increased force
43
Q

Why does the force-frequency relationship decrease in the failing heart?

A

down-regulation of SERCA

up-regulation of NcX

44
Q

What are the effects of down-regulating SERCA and upregulating NCX?

A

more calcium is extruded from the cell between beats and less Ca going into the SR

45
Q

What is isovolumic contraction?

A

where the volume is not changing but the pressure does not exceed that of the aorta so blood cannot move out the ventricles

46
Q

What are the stages of the cardiac cycle?

A
  • diastole - chambers fill with blood
  • atrial systole - atria contract - blood enters ventricles
  • isovolumic contraction
  • bicuspid valve closes - 1st heart sound
  • ventricular systole
  • isovolumic relaxation - 65mls left in heart - can increase output if needed
  • aortic valve closes - 2nd heart sound
47
Q

When does the 1st heart sound occur on the ECG?

A

with the QRS complex

48
Q

When does the 2nd heart sound occur on the ECG?

A

just after T wave

49
Q

What is the average Stroke Volume?

A

70mls

Cardiovascular Pharmacology (7 decks)

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