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BDS1 BAMS human systems > the cardiac cycle > Flashcards

the cardiac cycle Flashcards

1
Q

what makes up the cardiovascular system?

A

the heart, blood vessels and blood (circulation)

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2
Q

what are the functions of the cardiovascular system?

A
  • transport of oxygen and nutrients to meet the body’s metabolic demand
  • transport of metabolic waste eg CO2 for excretion
  • transport of hormones
  • maintain and transfer heat (body temperature)
  • aid response to infection and injury (by WBC and platelets in blood circulation)
  • assist regulation of fluid and pH within the body
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3
Q

what are the chambers of the heart?

A

right atrium, right ventricle, left atrium, left ventricle

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4
Q

which side of the heart contains deoxygenated blood?

A

the right

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5
Q

what is the function of valves in the heart?

A

permit/deny blood to flow

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6
Q

what are the atrioventricular valves?

A
  • tricuspid valve- right atria > ventricle
  • mitral (bicuspid valve)- left atria > ventricle
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7
Q

what are the semilunar valves?

A
  • pulmonary valve- right ventricle > pulmonary artery (RV outflow tract)
  • aortic valve- left ventricle > aorta
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8
Q

why is a little fat good surrounding heart valves?

A

acts as an insulator

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9
Q

what kind of process is the opening/closing of heart valves?

A

passive

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10
Q

how does the opening/closing of heart valves occur?

A

due to a difference in pressure

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11
Q

what is resistance to blood flow like when the heart valves are open?

A

very little resistance

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12
Q

when does an atrioventricular valve open?

A

when the pressure in the atrium exceeds the pressure in the ventricle, forced open and blood flows into the ventricle

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13
Q

when does an atrioventricular valve close?

A

when the contracting ventricle pressure exceeds the corresponding atrium pressure the valve closes- there’s normally no back flow of blood into the atrium and the blood is forced through the semilunar valves into the pulmonary artery (RHS) or aorta (LHS)

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14
Q

what is the word for ventricular contraction?

A

systole

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15
Q

what is the word for ventricular relaxation?

A

diastole

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16
Q

what are atrioventricular valves fastened to?

A

papillary muscles by fibrous chordae tendineae

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17
Q

what are papillary muscles and what is their function?

A
  • muscular projections of the ventricular wall
  • connected to valve cusps by fibrous chordae tendineae
  • function to prevent back-flow of blood by limiting cusp movements (DONT FUNCTION TO OPEN/CLOSE VALVES)
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18
Q

what are the two sounds of the heart?

A
  • first sound is the AV valves closing
  • second sound is the SL valves closing
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19
Q

when may a third heart sound be heard?

A

due to oscillation (back and forth movement) of blood flow into the ventricle or various disease states- heart valve defect

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20
Q

what are some heart valve defects?

A
  • valve regurgitation- blood leakage back into chamber caused by the valve not closing tightly
  • valve stenosis- thick/stiff valve cusp which prevents it from opening fully so not enough blood can flow through
  • congenital heart defect- pulmonary/aortic valves haven’t formed properly during development
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21
Q

describe the order of the cardiac cycle

A
  • left atrium
  • mitral valve
  • left ventricle
  • aortic valve
  • aorta
  • body tissues (not lungs)
  • superior/inferior vena cava
  • right atrium
  • tricuspid valve
  • right ventricle
  • pulmonary valve
  • pulmonary artery
  • lungs
  • pulmonary veins
    REPEAT
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22
Q

what direction does the inferior vena cava access the heart?

A

goes up into it

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23
Q

what direction does the superior vena cava enter the heart?

A

down into it

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24
Q

what are the differences between the left and right ventricle?

A
  • LV has thicker myocardium-
  • LV greater pressure
  • similar stroke volume (pump same amount of blood)
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25
Q

why does the LV have thicker myocardium and more pressure than the RV?

A

needs to overcome aortic resistance so blood can enter the systemic circulation (pumps blood around whole body)

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25
Q

why does the LV have thicker myocardium and more pressure than the RV?

A

needs to overcome aortic resistance so blood can enter the systemic circulation (pumps blood around whole body)

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26
Q

what kind of motion does the heart contract in?

A

a corkscrew motion

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27
Q

what are the two basic phases of the cardiac cycle?

A

systole and diastole

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28
Q

describe the systole phase of the cardiac cycle

A

contraction of myocardium
- atrial systole- eject blood into ventricles
- ventricular systole- eject blood into aorta (LV) and pulmonary vein (RV)

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29
Q

describe the diastole phase of the cardiac cycle

A

relaxation of myocardium
- atrial diastole- allow refilling
- ventricular diastole - allow refilling

30
Q

why is the atrial diastole often masked on an ECG?

A

masked by the ventricular systole

31
Q

describe ventricular filling

A
  • Atrioventricular valves open, allowing blood to flow from atria to ventricles.
  • Ventricles receive blood throughout diastole via passive flow and atrial contraction.
  • Mid-late diastole
32
Q

what is an early systole?

A
  • Ventricles contracting; however, all heart valves remain closed
  • Ventricular myocardium is developing tension and pressure on blood volume within ventricles is increasing.
  • Isovolumetric ventricular contraction (‘no change in volume’ contraction)
33
Q

what is a rapid ventricular ejection?

A
  • Pressure in the ventricles exceeds pressure in the aorta and pulmonary artery,
  • Semi – lunar valves open and blood is ejected from LV into aorta and from RV into pulmonary artery.
  • Volume of blood ejected from ventricle during systole = Stroke Volume (SV)
34
Q

what is an early diastole?

A
  • Ventricles begin to relax, semi-lunar valves close
  • As atrioventricular valves are also closed, no blood is entering or leaving ventricles
  • Isovolumetric ventricular relaxation (‘no change in volume’ relaxation)
34
Q

what is an early diastole?

A
  • Ventricles begin to relax, semi-lunar valves close
  • As atrioventricular valves are also closed, no blood is entering or leaving ventricles
  • Isovolumetric ventricular relaxation (‘no change in volume’ relaxation)
35
Q

what is the ejection fraction?

A

compares the volume of blood in the left ventricle to volume ejected with each contraction %

36
Q

what is a normal ejection fraction?

A

at least 55% (to 75%)

37
Q

what value of ejection fraction would be severely impaired?

A

less than 35%

38
Q

when does ventricular volume level off?

A

during isomeric contraction/relaxation - as valve is closed

39
Q

what is the myocardium?

A

cardiac muscle
- specialised striated muscle
- coordinated rhythmic contraction to pump blood around the body to make metabolic demand

40
Q

what are heart muscle cells called?

A

cardiomyocytes

41
Q

what determines heart rate?

A

the rate which the cardiac pacemaker (Sino-atrial node) fires action potentials which is determined by the ANS

42
Q

what is a normal resting heart rate?

A

60- 100 bpm

43
Q

what is the sympathetic nervous system mediated by?

A

beta- adrenoreceptors

44
Q

what is the parasympathetic nervous system mediated by?

A

muscarinic receptors

45
Q

what is noradrenaline?

A

a neurotransmitter released by sympathetic nerves

46
Q

what is circulating adrenaline?

A

a hormone released by adrenal glands

47
Q

describe sympathetic control of the CVS

A
  • binding of noradrenaline to beta1-adrenoceptors on the SA node
  • activates Gs-protein
  • activates Adenylyl Cyclase
  • increases cAMP
  • cAMP activates protein kinase
  • protein kinase phosphorylates and activates receptors and calcium-ion channels in cardiomyocytes
48
Q

what is positive chronotropy?

A

increased heart rate

49
Q

what is positive inotropy?

A

increased strength of myocardial contraction

50
Q

what is lusitropy

A

increases rate of myocardial relaxation

51
Q

what is positive dromotrophy?

A

increased conduction speed in AV node

52
Q

describe parasympathetic control of the CVS

A
  • Cholinergic nerves derived from the vagus nerve
  • Release neurotransmitter Acetylcholine (Ach)
  • Binds to M2 muscarinic receptors in cardiac muscle, particularly at the SA & AV nodes
  • Activates inhibitory G-protein
  • Blocking cAMP pathway and allows K+ infflux from cell
  • Decreasing Heart Rate (Negative Chronotropy)
  • Negative inotropy (decreasing force of myocardial contraction)
  • Negative lusitropy in atria (decreasing rate of myocardial relaxation)
  • Negative dromotropy (decreasing conduction speed in AV node)
53
Q

what triggers the heart to contract?

A

A wave of depolarisation, initiated at the cardiac pacemaker, the sinoatrial node travels through the Cardiac Conduction System innervating the myocardium and travels cell to cell within the myocardium.

54
Q

what does the sinoatrial node act as?

A

the pacemaker of the heart

55
Q

what is sarcolemma?

A

plasma membrane

56
Q

what is a membrane potential?

A
  • Potential difference between intracellular and extracellular sides of the cell membrane.
  • Generated by ion gradients across the cell membrane
  • Dependent on ionic gradients across membrane (intracellular vs extracellular) and ionic permeability
  • Ion channel proteins and transporters facilitate transport of ions across the Sarcolemmal membrane.
  • Channels/transporters are selective for various ions (L-type calcium channel: ICa-L)
57
Q

what are examples of cells with excitable membranes?

A

myocytes and neurons

58
Q

what is resting membrane potential (Vm)?

A

-80mV (inside cell is more negative than outside)

59
Q

what is depolarisation?

A

potential difference across the cell membrane becomes ‘less negative’

60
Q

what is repolarisation?

A

potential difference across sarcolemma returns to resting Vm following depolarisation (becomes ‘more negative’)

61
Q

what is an action potential?

A
  • Rapid rise and fall in voltage / membrane potential (Vm)
  • Voltage vs Time waveform
  • Characteristic pattern for specific cell types
  • Action potential shape changes in different cardiac regions
62
Q

what is excitation-contraction coupling?

A

Couples the electrical activity of the Cardiac Conduction System to the mechanical contraction of the myocardium.

63
Q

describe the steps of excitation-contraction coupling

A
  • Through myocytes of right atrium and left atrium initiating contraction
  • Propagation of depolarisation (by action potential) through RA to the AV node
  • Propagation of action potential through AV node is relatively slow allowing for completion of atrial contraction prior to initiation of ventricular excitation & contraction.
  • Action potential propagates from AV node along the interventricular septum via the Bundle of His
  • Bundle of His separates into the left and right bundle branches which innervate the walls of the myocardium
  • Rapid propagation of action potential along purkinje fibres initiates coordinated contraction of the cardiac myocytes of the left and right ventricles
64
Q

what is an echocardiogram? (ECG)

A
  • Type of ultrasound scan
  • Used to assess structure and function of heart
  • High temporal resolution (2D imaging)
65
Q

what can an echocardiogram aid the detection of?

A
  • Impaired function due to myocardial infarction (heart attack)
  • Congenital heart disease; birth defects that impact cardiac function
  • Cardiomyopathy: enlargement (thickening) of ventricular walls
  • Endocarditis: infection of endocardium that damages heart valves
  • Heart Failure: Heart is unable to adequately pump blood to meet metabolic demands of body
66
Q

what are the letters and meanings in an ECG?

A

P wave= Atrial depolarisation (small bump)

QRS complex= Ventricular depolarisation (large spike)

T wave= Ventricular repolarisation (bigger bump)

P – R Interval= Delay through AV node

S – T Interval= Plateau phase of ventricular action potential

R - R Interval= heartrate

66
Q

what are the letters and meanings in an ECG?

A

P wave= Atrial depolarisation (small bump)

QRS complex= Ventricular depolarisation (large spike)

T wave= Ventricular repolarisation (bigger bump)

P – R Interval= Delay through AV node

S – T Interval= Plateau phase of ventricular action potential

R - R Interval= heartrate

67
Q

what is the cardiac output?

A
  • Volume of blood pumped by the heart per minute
    = Stroke Volume (SR) x Heart Rate (HR)
68
Q

what is Starling’s Law?

A
  • The force of muscle contraction increases as the muscle is stretched in response to an increased filling of the heart’s chambers.
  • Heart muscle must respond to stretching in this way
  • As otherwise circulation of blood would fail.
  • This response is intrinsic to the heart
69
Q

what is cardiac preload?

A
  • Initial stretching of cardiac myocytes prior to contraction
  • Indicated by ventricular End – Diastolic Volume (pressure)
  • As stretching of cardiac myocytes cannot be determined in intact heart
70
Q

what is cardiac afterload?

A
  • Pressure heart must eject blood against
  • LV afterload related to aortic pressure

BDS1 BAMS human systems (47 decks)

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