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Veterinary physiology > Cardiac physiology > Flashcards

Cardiac physiology Flashcards

1
Q

difference between diffusion and faciliatated diffusion?

A

Simple diffusion is the direct transport of molecules across the cell membrane

Facilitated diffusion occurs through the action of transmembrane proteins such as carrier proteins, channel proteins, and aquaporins.

these are both passive transport

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2
Q

describe active transport

A

the movement of molecules or ions against their concentration gradien

requires energy, usually ATP

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3
Q

time its takes for diffusion across myocardium

A

15h

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4
Q

what is Convection (bulk flow) in the context of cardio physiology

A

Convection is the transport of a substance by bulk flow over longer distances, where bulk flow is the movement of fluid down a pressure gradient (like blood vessels).

e.g. Lung capillaries
Systemic capillaries

This is in opposition to diffusion which is across cell membranes etc.

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5
Q

Name Primary cardiovascular disturbances (6)

A

Heart muscle diseases

Diseases of heart valves
Diseases of heart rhythm – generation or conduction
Diseases of vessels (PHT/Pulmonary hypertension, parasites, etc)

Haemorrhage
Diseases of blood

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6
Q

which circulation has high resistance to flow and which, low?

A

systemic circ. has high

pulmonary circ. low

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7
Q

define CO

A

cardiac output CO – volume ejected in one minute

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8
Q

define SV

A

Stroke volume SV – volume ejected in one heartbeat

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9
Q

define HR

A

Heart rate HR – number of heartbeats in minute

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10
Q

How is cadiac output calculated?

A

CO = SV*HR

cardiac output = stroke volume * heart rate

CO – volume ejected in one minute
SV – volume ejected in one heartbeat

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11
Q

Name 4 functions of elastic arteries

A

Accommodate stroke volume
Smooth the flow
Temporary blood storage
Maintain blood pressure

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12
Q

Function of Conduit (muscular) arteries

A

Regulate flow volume depending on the need

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13
Q

What are Capacitance vessels/ where is the most blood found?

A

systemic circulation – venous system, blood reservoir

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14
Q

What initiates the shortening of sarcomeres?

A

Ca2+

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15
Q

sarcomere fibers

A

myosin and actin
thick & thin

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16
Q

name the primary pace maker

A

Sinus node, also know as sinoatrial node

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17
Q

where does delay of conduction occur?

A

atrioventricular node

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18
Q

rapid conduction to ventricular myocardium happens via

A

Bundle of His

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19
Q

Bundle of His continues as?

A

Bundle branches: Left and right

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20
Q

conduction to myocardial cells via?

A

Purkinje fibres

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21
Q

define EDV

A

end-diastolic volume

is the volume of blood in a ventricle at the end of filling (diastole).

EDV is often used synonymously with preload

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22
Q

define ESV

A

end-systolic volume

is the volume of blood in a ventricle at the end of systole, and the beginning of diastole.

ESV is the lowest volume of blood in the ventricle at any point in the cardiac cycle.

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23
Q

how is SV calculated

A

SV = EDV - ESV

end-diastolic volume - end-systolic volume = stroke volume

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24
Q

define EF

A

Ejection fraction is the volumetric fraction of fluid ejected from a chamber with each contraction.

In other words:
Fraction of the blood pumped out of the ventricle

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25
Q

How is EF calculated?

A

EF=SV/EDV

Ejection fraction = Stroke volume / end-diastolic volume

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26
Q

What is isovolumetric contraction and whic valves are open/closed during it?

A

isometric contraction is an event occurring in early systole during which the ventricles contract with no corresponding volume change.

This short-lasting portion of the cardiac cycle takes place while all heart valves are closed.

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27
Q

What portion of an ecg represents Atrial systole

A

the P wave

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28
Q

What ion initiates shortening of cardiac myocytes?

A

Ca++

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29
Q

Cause of S1?

A

atrioventricular valves closing

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30
Q

What does the onset of the T wave of an ecg represent?

A

ventricular repolarization

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31
Q

What is Isovolumetric ventricular relaxation

A

interval in cardiac cycle:
Ventricular volume remains constant – all valves are closed

from S2 to onset of filling by opening of the mitral valve

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32
Q

Cause of S2?

A

aortic valve closure (+followed by pulmonary valves)

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33
Q

What does the end of T wave represent?

A

Ventricular repolarisation is complete

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34
Q

What valves are opened/closed during ventricular mid-diastole?

A

Atrioventricular valves are open, pulmonic and aortic valves closed

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35
Q

define diastasis

A

or Reduced ventricular filling

Longest phase of cardiac cycle and includes the final portion of ventricular filling, which occurs at a slower rate than in the previous phase.

Diastasis duration depends on heart rate

the rest phase of cardiac diastole occurring between filling of the ventricle and the start of atrial contraction.

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36
Q

define preload

A

end diastolic volume or
filling pressure

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37
Q

define Afterload

A

Total resistance to blood flow out of the heart

is the pressure that the heart must work against to eject blood during systole

Afterload is proportional to the average arterial pressure.

38
Q

define Contractility

A

an intrinsic feature of the myocardium

Myocardial contractility represents the innate ability of the heart muscle to contract.

39
Q

What is Starling’s Law of heart

A

The more the heart fills
🡪 the stronger the contraction
🡪 the bigger the stroke volume

(the bigger the EDV; the bigger the preload)

40
Q

what common substance will increase myocardial contractility

A

noradrenaline or adrenaline

41
Q

define inotropy

A

Inotropy is the strengthening/weakening function of the cardiac tissue.

An inotrope is an agent that alters the force or energy of muscular contractions

42
Q

What might happen to EDV and SV when preload is raised?

A

Increases EDV
Increases SV

43
Q

What changes about ESV and SV when contractility is raised?

A

Decreases ESV
Increases SV

44
Q

What changes may occur to ESV and SV when after load is raised?

A

Increases ESV
Decreases SV

45
Q

A lowered preload will do what to EDV and SV?

A

Decreases EDV
Decreases SV

46
Q

How does lowered contractility affect ESV and SV?

A

Increases ESV
Decreases SV

47
Q

How does a lower afterload affect ESV and SV?

A

Decreases ESV
Increases SV

48
Q

What intrinsic system controls myocardial contractility?
what stimulates an increase and what a decrease?

A

Autonomous nervous system
Sympathetic stimulates,
parasympathetic reduces

49
Q

Name 2 factors to affect afterload

A

vasoconstriction
total peripheral resistance

50
Q

EDV is determined by (3)

A

Preload
Ventricular compliance (distensibility)
Diastolic filling time

51
Q

ESV depends on? (2)

A

ESV depends on ventricular contractility
and resistance to flow

52
Q

name 2 types of hypertrophy

A

concentric: thickens walls

& eccentric: widens or dilates

53
Q

define hypertrophy

A

increased number of sarcomeres

54
Q

Concentric hypertrophy happens in response to

A

increased resistance

55
Q

Eccentric hypertrophy happens in response to

A

increased volume

56
Q

What happens during T wave of ECG?

A

Ventricular repolarization (so ventricular relaxation)

57
Q

Which hormone is released from the ventricles?

A

the ventricles secrete brain natriuretic peptide (BNP).

58
Q

What is ANP and where is it produced?

A

Atrial natriuretic peptide
secreted from the cardiac atria

59
Q

What triggers ANP and what is its function?

A

in response to increased stretching of the atrial wall due to increased atrial blood volume.

Reduction of blood volume
The collecting duct is the main site of ANP regulation of sodium excretion.

ANP effects sodium channels at both the apical and basolateral sides. ANP inhibits ENaC on the apical side and the Sodium Potassium ATPase pump on the basolateral side resulting in less sodium re-absorption and more sodium excretion.

60
Q

What is BNP and where is it produced?

A

Brain natriuretic peptide

secreted by cardiomyocytes in the heart ventricles in response to stretching caused by increased ventricular blood volume.

causes the kidneys to excrete more salt and water

61
Q

How much cardiac output does the myodarcidum itself receive?

A

approximately 5%

62
Q

What is the Treppe phenomenon

A

also known as the Bowditch effect or staircase phenomenon, or frequency-dependent activation.

It refers to the idea that an increase in heart rate increases the force of contraction generated by the myocardial cells with each heartbeat despite accounting for all other influences.

Inotropy (so increased strength of contracion) increases with increased heart rate.

63
Q

definition of Resting membrane potential

A

the potential difference in voltage across a cell membrane at rest

It is negative inside with respect to outside.

64
Q

resting membrane potential in cardiac muscle

A

approx. -85 mV

65
Q

resting membrane potential in sinoatrial node

A

approx. -55mV

66
Q

which ions generate resting membrane potential

A

Potassium ions K+

67
Q

which ion channels are closed at negative potentials

A

Na+ and Ca++ channels are closed at negative potentials

68
Q

are Cl- concentrations higher or lower intra- and extracellularly?

A

intracellularly lower
extracellularly higher

69
Q

are K+ concentrations higher or lower intra- and extracellularly?

A

intracellularly higher
extracellularly lower

70
Q

role of the Na+-K+ pump

A

Preserves intracellular ion levels

71
Q

role of Ca++ transporters

A

Regulates diastolic Ca++ and the Ca++ store

72
Q

definition of action potential

A

the change in electrical potential associated with the passage of an impulse along the membrane or muscle cell or nerve cell

73
Q

describe the steps of Cardiac action potentials for non-pacemaker cells (5)

A

Phases
0 – influx of Na+
1 – efflux of K+ from transient opening of K+ -channels
2 – influx of Ca++ (1+2 equal the plateau)
3 – repolarisation by continuous efflux of K+, clearance of Ca++
4 – resting potential

74
Q

describe the steps of Cardiac action potentials for pacemaker cells (3)

A

Phases
0 – rapid influx of Ca++
3 – efflux of K+, clearance of Ca++
4 – “funny current” – slow influx of Na+

75
Q

define Excitability

A

the ability of cardiac muscle to respond to a stimulus of adequate strength and duration by generating an AP

76
Q

define Syncytium

A

a single cell or cytoplasmic mass containing several nuclei, formed by fusion of cells or by division of nuclei.

77
Q

define cardiac excitation-contraction coupling

A

The process where an action potential triggers a myocyte to contract.
or
The series of events that link the action potential (excitation) of the muscle cell membrane (the sarcolemma) to muscular contraction.

78
Q

what does the P wave itself represent?

A

atrial depolarization

79
Q

what does the QRS complex represent?

A

ventricular depolarization

80
Q

where is an ecg can you find atrial repolarization?

A

is masked within the QRS complex

81
Q

what is Einthowen’s triangle

A

is an imaginary formation of three limb leads in a triangle used in electrocardiography, formed by the two shoulders and the pubis.

The shape forms an inverted equilateral triangle with the heart at the center.

82
Q

What are the first 2 steps to ecg interpretation?

A

1) what is the rate? (Bradycardia, normal, tachycardia)
2) what is the rhythm? (regular, rhytmicly irregular, chaotic)

83
Q

What are steps 3 and 4 to ecg interpretation?

A

3) is there a QRS complex for every P wave?
4) is there a P wave for every QRS complex?

84
Q

What are steps 5 and 6 to ecg interpretation?

A

5) are the QRS complexes consistently and reasonably related?
6) what is the QRS morphology? (narrow, wide & bizarre)

85
Q

What are steps 7 and 8 to ecg interpretation?

A

7) what is the mean electrical axis? (reflects the average direction of ventricular depolarization during ventricular contraction)

8) what are the complex and interval measurements?

86
Q

difference between atrial fibrillation and atrial flutter?

A

In atrial fibrillation, the atria beat irregularly.

In atrial flutter, the atria beat regularly, but faster than usual and more often than the ventricles, so you may have four atrial beats to every one ventricular beat.

Atrial Flutter is a less severe heart condition than Afib.

87
Q

name 3 normal rhythms

A

sinus rhythm
Respiratory sinus arrhythmia
wandering pacemaker rhythm

88
Q

What does the PR segmen express in an ecg curve

A

the delayed conduction in the AV-node.

89
Q

what is a Pressure-volume loop

A

A graphic representation of changing ventricular pressure and volume during a cardiac cycle.

90
Q

What are Ryanodine receptors

A

Ryanodine receptors (RyR for short) form a class of intracellular calcium channels in various forms of excitable animal tissue like muscles and neurons.

Veterinary physiology (10 decks)

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