Brainscape's Knowledge GenomeTM

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


See full index

CVS Physiology > Electrical Activity of the Heart > Flashcards

Electrical Activity of the Heart Flashcards

1
Q

How does skeletal muscle contract?

A

Sarcoplasmic reticulum big calcium store and the calcium causes coupling
Calcium binds to triponomyosin which is bound to troponin. When calcium binds it breaks that bond
Calcium release causes skeletal muscle to contract
This is caused by an AP due to a motor neurone releasing ACh for the nicotinic receptors

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

How does cardiac muscle contract?

A

Cells connected by gap junctions
Desmosomes do the physical joining together
If one cell depolarises then fires an AP then it is more likely that the next cell will also
Allows calcium to come in from the outside
Cardiac muscle produces a sub maximal contraction so can regulate how much can come from the outside which regulates the strength of contraction

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

What are a gap junction and a desmosome together known as?

A

Intercalated disc

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

Site of AP cardiac muscle (CM) vs skeletal muscle (SM)

A

CM - 200 miliseconds (longer)

SM - 2 miliseconds

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

Calcium CM vs SM

A

CM - calcium comes from outside

SM - calcium comes from inside

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

Types of contraction CM vs SM

A

CM - Sub maximal contraction

SM - Maximum contraction

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

Refractory period CM vs SM

A

CM - Very long due to stimulation on different parts of the graph
SM - very short due to twitch contractions summing to make a sustained contraction

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

What does the very long refractory period in cardiac muscle result in?

A

The muscle has to relax before it can contract again

This stops it doing a tetanus

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

Describe the cardiac muscle functional syncytium

A

Electrically connected by GAP JUNCTIONS
Physically connected by desmosomes
Forming intercalated discs

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

Action potential length of cardiac muscle

A

Long

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

What makes sure that cardiac muscle cannot exhibit tetanic contraction?

A

Long refractory period

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

What kind of muscle has an unstable resting potential? What do these act as?

A

Cardiac muscle

Act as pacemakers

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

Features of non pacemaker cells

A

Sit at a certain voltage until told to depolarise by the gap junctions

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

Features of pacemaker cells

A

Will spontaneously depolarise to threshold and fire an AP

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

Permeability of non pacemaker cells at resting membrane potential

A

Sodium and calcium low

High potassium

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

Non pacemaker action potential

A
  1. Resting membrane potential
    - High resting Pk+
  2. Initial depolarisation
    - increase in PNa
    - voltage gated sodium channels opening when there is depolarisation from neighbouring cells leads to an increase in sodium permeability and massive depolarisation
    - this DOES NOT repolarise - it stays in plateu phase
  3. Plateau
    - increase in PCa2+ (L-type) and decrease in PK+
    - stays in plateau phase because of voltage gated calcium channels slowly letting calcium flow in, therefore the plateau is due to calcium constantly flowing in and also a decrease in permeability to potassium by blocking the channels
  4. Repolarising
    - reverse
    - decrease in PCa2+ and increase PK+ so sodium and calcium channels shut and leaky potassium opens
17
Q

What causes the pacemaker AP?

A

Just calcium channels

18
Q

Pacemaker action potential

A
  1. AP
    - increase in PCa2+ (L-type)
  2. Pacemaker potential (pre potential)
    - gradual decrease in PK+ by closing the leaky potassium channels
    - early increase in PNa+ (=PF) - if a bit of sodium is let in at the early bit of pacemaker
    - late increase in PCa2+ (T-type) as they are tiny calcium channels so only a wee bit of Ca is let in but pushes the cell the last wee bit towards threshold
19
Q

Modulators of electrical activity

A 
Sympathetic and parasympathetic systems 
Drugs 
- Ca2+ channel blockers 
- cardiac glycosides 
Temperature
Hyperkalaemia 
Hypokalamia 
Hypercalcaemia
Hypocalcaemia
20
Q

Effects of CCBs on contraction

A

Decreases

21
Q

Effects of cardiac glycosides on contraction

A

Increases

22
Q

Effects of temp on contraction

A

Increases approx. 10 beats / min / degree centigrade

23
Q

Effects of hyperkalaemia

A

Fibrillation and heart block

High K outside the cell decreases the concentration gradient for K and so depolarises the cell

24
Q

Definition of fibrillation

A

APs are spontaneously fired in an uncoordinated fashion

25
Q

Effects of hypokalaemia

A

Fibrillation and heart block (anomalous)

Lose K and then cells start to hyperpolarise and then loads of channels open and the cells depolarises

26
Q

Effects of hypercalcaemia

A

Increased HR and force of contraction

27
Q

Effects of hypocalcaemia

A

Decreased HR and force of contraction

28
Q

Features of the sinoatrial node

A

Pacemaker
Approx 0.5m/sec
Where the fastest pacemakers are

29
Q

Where is the sinoatrial node found?

A

Right atrium

30
Q

Features of the annulus fibrosis

A

Non conducting
AP gets stuck here and does not pass into the ventricle
Only way AP can pass through is the AV node

31
Q

Where is the annulus fibrosis found?

A

Between atrium and ventricles

32
Q

Features of atrioventricular node

A

Delay box
Approx. 0.05m/sec
Atrium has time to get the blood to the ventricle before the ventricle starts pumping, because the node slows it down

33
Q

What is the nerve fibres at the ventricles which makes them contract?

A

Bundle of His

34
Q

What does the Bundle of His break down into?

A

Purkinje fibres

35
Q

Features of purkinje fibres

A

Rapid conduction system

Approx. 5m/sec

36
Q

Does an ECG tell you about how the heart pumps?

A

No

37
Q

What kind of disorders does an ECG tell you about?

A

Disorders of rhythm

Disorders of conduction

38
Q

Examples of disorders of conduction

A

Degree blocks

39
Q

How does a defibrillator work?

A

Depolarises all of the cells to their refractory cells and so this stops the heart, so they are ready to receive action potentials again

CVS Physiology (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions