Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

The Cardiovascular System > Electrophysiology Of The Heart > Flashcards

Electrophysiology Of The Heart Flashcards

1
Q

Initiation of a heart beat - the process:

A
  • the cardiac muscle must be stimulated to contract
  • left and right atriums contract first
  • delay
  • left and right ventricles contract
  • order = important for efficient blood transit
  • the heart generates an action potential = electrical impulse
  • which stimulates the contraction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How is a membrane potential generated:

A
  • due to a difference in internal and external ion concentrations
  • potassium ion concentration is higher inside than outside
  • potassium ions move out
  • sodium ion concentration is higher outside than inside
  • sodium ions move in
  • this equilibrates the concentration
  • this can be used to generate an action potential
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How is an action potential generated?

A
  • some ion channels open
  • leak, ligand or voltage dependent
  • cell membrane becomes depolarised
  • action potential spreads throughout the membrane
  • other ion channels open
  • in order to repolarise the membrane
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How does nerve transmission work?

A
  • signal spreads along the neuron like a wave
  • membrane needs to repolarise before the next signal
  • some ion channels stay inactive, until the membrane is repolarised
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How does the membrane become repolarised?

A
  • sodium ion channels open
  • depolarise the cell membrane
  • more sodium ion channels open
  • potassium ion channels open
  • sodium ions channels close
  • the membrane is repolarised
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How can the concentration gradients of the ions be restored?

A

The Na+ / K+ -ATPase pump system

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

How many phases does cardiac action potential have?

A

Graph:
- 0
- 1
- 2
- 3
-4

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

Phase 0 of action potential:

A
  • immediate depolarisation caused by the opening of fast sodium channels
  • allowing rapid entry of sodium ions
  • fast potassium channels close
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Phase 1 of action potential:

A
  • the sodium channels close
  • slow potassium channels open
  • slow exit of potassium ions
  • depolarisation triggers slow calcium channels to open
  • which allow slow entry of calcium ions move
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Phase 2 of action potential:

A
  • plateau
  • membrane potential reaches a steady point
  • due to the slow exit of potassium ions and the slow entry of calcium ions
  • due to calcium ion influx
  • delays repolarisation, which is important
  • stops the heart muscle resetting too fast
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Phase 3 of action potential:

A
  • calcium channels close
  • fast potassium channels open
  • causing a rapid exit of potassium ions
  • the membrane is repolarised
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Phase 4 of action potential:

A
  • the voltage decreases to its original value
  • remains steady, potassium channels remain open
  • until the next action potential is generated
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Are extrinsic nerves necessary to initiate the first contraction of the heart, and if not why not?

A
  • not necessary
  • heartbeat is controlled by the cardiac electrical system
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the nodes of the heart? (Pacemakers)

A
  • sinoatrial (SA) node
  • atrioventricular (AV) node
  • discharge spontaneously to initiate the heartbeat
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the conduction fibres of the heart?

A
  • bundle of His
  • left and right bundle branches
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the function of the SA node?

A
  • main pacemaker & initiator of heartbeat
  • discharges once every second
  • discharge rate is changed by the nerves innervating the heart
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the function of the AV node?

A
  • only electrical connection between the atria and the ventricles
  • delays conduction of action potential by 0.1s
  • allows the atria to contract and the ventricles to fill
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the function of the bundle of His and left and right bundle branches & fibres of purkinje?

A
  • to excite the ventricular mass as simultaneously as possible
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the pacemaker potential?

A
  • many cells in the heart have an unstable membrane potential
  • which decays slowly
  • when the potential reaches a threshold, it triggers an action potential
  • the slope of the pacemaker potential determines the time taken to reach the threshold
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

When is the pacemaker slope the steepest?

A

SA node cells

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

Why is it the steepest in SA node cells?

A
  • fastest firing rate
  • initiates the heartbeat before the others get there
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What causes the decay of the SA node slope and pacemaker potential?

A
  • sodium ions flow into the cell
  • depolarisation
  • membranes are less permeable to potassium ions
  • sudden acceleration in depolarisation, due to influx of calcium ions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

SA node contraction phases:

A
  • 4
  • 0
  • 3
  • 4
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Phase 4 of SA node:

A
  • after previous repolarisation of the SA node,
  • ion channels open & allow slow entry of sodium ions
  • funny currents
  • they cause the membrane to spontaneously depolarise
  • transient t-type calcium channels open
  • calcium ions slowly start to enter the node
  • more depolarisation
  • l-type calcium channels open
  • more calcium ions enter the cell
  • more depolarisation
  • until a threshold is reached
25
Phase 0 of the SA node:
- at the threshold, L-type calcium channels open - allow rapid entry of calcium ions to fully depolarise the membrane
26
Phase 3 of SA node contraction:
- L-type calcium channels close - fast potassium channels open - rapid exit of potassium ions - membrane is repolarised
27
Phase 4 of SA node again:
- ready to start again - SA node firing causes contraction of the atrium - AV node delays the signal to the Bundle of His and Fibres of Purkinje - this causes contraction of the ventricles = the signal does - heart cells are electrically linked, so the action potential spreads simultaneously
28
Why are the atrium and ventricles insulated from each other?
- special links - these are intercalated disks
29
Cardiac output can be controlled in two ways:
- internal - external
30
What is the external control of cardiac output?
- nervous - humoral
31
What are the two sections of the autonomic nervous system that are connected to the heart?
- sympathetic - parasympathetic
32
What do sympathetic nerves do?
Release noradrenaline
33
What do left nerves do?
Supply atrial & ventricular muscle
34
What do right nerves do?
Supply pacemaker and conduction system
35
What does the positive inotropic (strengthening) effect do?
- increases contractility of muscle
36
What does the positive chronotropic effect do?
Increases rate of rise of pacemaker potential
37
What does shortening the conduction delay in the AV node do?
Increases the rate of relaxation
38
How is the inotropic effect strengthening?
- increases the amount of calcium ions stored in the sarcoplasmic reticulum - causes a rise of calcium ion current during the plateau of cardiac action potential - uptakes back into sarcoplasmic reticulum, muscle relaxes faster, preserves the diastolic filling period
39
What are three mechanisms that regulate contractile force?
- the size of the calcium ion current - affinity of contractile proteins for calcium ions = depends on the stretch - degree of actin-myosin overlap = depends on stretch
40
What is parasympathetic innervation of the heart controlled by?
Vagal nerves
41
What is the function of vagal nerves?
Releases acetylcholine
42
How does vagal stimulation produce bradycardia?
- rate of upward drift of the pacemaker potential is slowed - initial pacemaker potential becomes negative, it is hyperpolarised
43
How heart muscle contraction works via parasympathetic nervous system:
- action potential raises calcium ion levels within the cardiac muscle - due to an uptake & release from the sarcoplasmic reticulum - some calcium ions bind to troponin c - which is bound to thin actin filaments - this exposes binding sites on actin filaments - for the thick myosin heads - myosin cross-bridge attaches to the actin filaments - myosin head pivots and bends as it pulls on the actin filaments, slides it towards the M line - thick myosin filaments have heads that can flip, via ATP - new ATP attaches to myosin head, the cross bridge detaches - it causes myosin & actin filaments to slide over one another - heart muscle contracts
44
At resting heart beat, what is not at maximum?
- calcium ion release
45
What does increasing the calcium ion release do?
Increase the force of contraction
46
What is the Frank-Starling mechanism?
- as blood enters the heart, it stretches the cardiac muscle - in exercise, more blood enters, so it stretches even more - this produces extra force - expels a larger volume of blood - this allows us to handle an increased blood volume - unique to cardiac muscle - to have increased force on demand - it balances the outputs of the left and right ventricles
47
What happens if the output of the right ventricle exceeds the left ventricle?
- pulmonary volume increases - increased pressure in the pulmonary veins - left ventricular filling pressure increases - left ventricle becomes more distended - increased stroke volume
48
How does increased filling pressure increase contraction?
- myosin heads on myosin filaments pull actin filaments - each end pulls in the opposite direction - if the sarcomere length is below 2 micrometers, it causes mechanical interferenc - due to an overlap in actin onto the opposite side - it needs to stretch more to get a better contraction - as the muscles stretch, sensitivity to calcium increases
49
What does an ECG do?
- measures the electrical current the heart generates, measured on the skin surface
50
At rest - current flow:
- mV is constant - no current flowing - no flow of ions to generate an action potential and an electrical impulse
51
What happens mV during depolarisation?
- mV is not constant - some positive potential - current is flowing - due to the flow of ions into the cell - action potential & electrical impulse is generated - which can be measured by the ECG
52
What happens when it is completely depolarised?
- mV is constant - no current flowing - no flow of ions to generate an electrical impulse - OmV
53
What happens when the cardiac muscle repolarises?
- mV is not constant - current flows - negative voltage reading - due to a flow of ions out of the cell - electrical impulse produced is of opposite polarity - due to depolarisation
54
The magnitude and polarity of the signal depends on:
- what the heart is doing electrically = depolarising or repolarising - the position and orientation of the recording electrodes
55
Where is a normal ECG done?
- right arm - left leg
56
P wave =
Atrial muscle depolarisation
57
QRS =
Ventricular muscle depolarisation
58
T wave =
Ventricular muscle repolarisation

The Cardiovascular System (5 decks)

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