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BVetMed 1 > CVRS - Heart > Flashcards

CVRS - Heart Flashcards

1
Q

What is the primary functions of the heart?

A
  • Transport O2 and substrates to cells (e.g. Glucose, fatty acids, amino acids, drugs etc.)
    -Transport CO2 and metabolites from cells (e..g. urea and creatinine)
  • Distribution of hormones (e.g. adrenaline)
  • Defence (e.g. immune cells called leukocytes aka WBCs)
  • Haemostasis (platelets stopping bleeding)
  • Thermoregulation (heat from deep organs is dissipated)
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2
Q

What is systole and diastole?

A

Systole - contraction
Diastole - relaxation

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3
Q

What is fish circulation like?

A

Single circulatory system with 1 atrium and 1 ventricle

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4
Q

What is an amphibian circulation like?

A

Double circulatory system with 2 atriums and 1 ventricle and spiral valves

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5
Q

What are mammal/bird/crocodilian systems like?

A

Fully developed double system with 2 atriums and 2 ventricles.

Complete septums:
-Right atrium - septum secundum
-Left atrium - septum primum

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6
Q

What changes in the foetus to baby? 1/2

A

The foramen ovale connecting the atria to the umbilical vein becomes the fossa ovalis very quickly after birth.

Foremen ovale is a hole between the left and right atria as the pulmonary system is required yet.

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7
Q

What changes in the foetus to baby? 2/2

A

The ductus arteriosus (vessel between pulmonary trunk and aorta) becomes ligamentum arteriosum (attaches aorta to pulmonary artery).

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8
Q

What are the two types of circulation in a double circulatory system?

A

Systemic circulation (from the heart to the body and back again)

LV >Aorta>Body>Tissues>VC>RA

Pulomnary circulation (from the heart to the lungs and back)
RV>Pulomary artery>lungs>pulomary vein>LV

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9
Q

What are the pressures of the two systems?

A

Vena cava to right atrium - 3mmHg
Right ventricle to Pulmonary artery - 12mmHg
Pulmonary vein to Left Atrium - 7mmHg
Left Ventricle to Aorta - 100mmHg

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10
Q

What is the thicker side of the heart?

A

The left ventricle as it pumps to aorta to rest of body

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11
Q

What are the three layers of the heart?

A

Endocardium - internal layer, continuous with the rest of the CVS
Myocardium - muscle tissue in the middle
Epicardium - part of the pericardial sac

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12
Q

What are the AV valves?

A

Atrioventricular valves - tricuspid/right and mitral/left

Papillary muscles attach to the cusps via the chorea tendinae and contract during systole to prevent collapsing of the valves

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13
Q

What are the semi-lunar valves?

A

In the outlets of the ventricles (pulmonary artery and aorta) to stop backflow into the heart at the end of systole.

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14
Q

What is the flesh between the atria called?

A

Septum secundum - right atrium
Septum primum - left atrium

The fossa ovalis is what the foramen ovale is in foetus, and this joins the two septum.

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15
Q

What is the cardiac skeleton?

A

It is the non-conductive connective tissue where the heart sits. It structurally supports and acts as an electrical dampener, electrically isolates each chamber.

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16
Q

What is the blood supply to the heart?

A

This is the coronary circulation. The first two branches of the aorta supply the myocardium. 5% of the cardiac output is sent here to meet high metabolic demand, with extensive capillarisation.

This blood drains into the coronary sinus where it pools. The thesbian veins despoit into the heart.

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17
Q

What are the types of blood vessels?

A

Large Arteries
Medium/Small Arteries
Arterioles
Capillaries
Venules/Veins

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18
Q

Describe large arteries

A

They are elastic vessels.

These accommodate a high stroke olumes and convert intermittent ejection into continuous flow

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19
Q

Describe medium/small arteries

A

These are feed vessels.

Conduct blood flow to organs

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20
Q

Describe arterioles

A

These are resistance vessels

These control arterial blood pressure and local blood flow by controlling diameter.

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21
Q

Describe capillaries

A

These are exchange vessels.

Important for nutrient delivery, lymph formation and removal of metabolic waste.

These can be fenestrated (with holes)

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22
Q

Describe venules/veins

A

These are capactiance vessels.

These control cardiac filling pressure and act as a reservoir of blood (holds 64% of blood).

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23
Q

What are the three layers of the vessels?

A

Tunica intima (inner wall)
Tunica media (middle wall)
Tunica externa/adventicia (external wall)

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24
Q

Differences in the three layers with artery and veins

A

Inner wall
ARTERY - rippled with an internal external membrane
VEIN - smooth without elastic

Middle wall
ARTERY - thick with smooth muscle and elastic fibres
VEIN - thin, smooth muscle and collagen, no external elastic fibres

External wall
ARTERY - collagen and elastic fibres, nerve terminals and vasa vasorum
VEIN - collagen and elastic fibres, smooth muscle and nerve terminals

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25
Q

What is an arteriole like?

A

It has a thick muscular wall and a narrow lumen to help with the resistance of blood flow

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26
Q

What is Poiseuilles equation?

A

It is the resistance to flow

R = n to the power of L / r to the power 4

Where
R = resistance
r = radius (double = 16x flow)
n = viscosity
L = length

27
Q

What is blood flow equation?

A

F = P / R

Where P is pressure and R is the resistance

28
Q

What are capillaries made up of?

A

1 layer of endothelium sitting on a basement membrane. Many have pericytes, which are contractile cells which secrete proteins.

29
Q

What moves fluid across capillaries?

A

Starlings forces are two opposing forces to move fluids:
-Oncotic pressure is exerted by protein concentration in the plasma
-Hydrostatic pressure is exerted by the blood

At the arterial end the pressure is higher than at the venous end.

30
Q

What is the lymphatic system?

A

It carries interstitial fluid to the cardiovascular system and works along side it.

31
Q

What causes abnormal fluid build up?

A

It is an oedema. Caused by:
Increased capillary permeability
Increased capillary pressure
Decrease plasma protein
Decrease lymphatic drainage

32
Q

What are the cells of the heart and how are they arranged?

A

The heart is made up of myocytes, arranged as intercalated disks held together with desmosomes and tight adhereing junctions. Electrically coupled by gap junctions.

33
Q

How does the heart contract?

A

In syncytium, it is highly vascularised with a lot of mitochondria to contract a lot..

34
Q

What are the nodes of the heart?

A
  1. SAN
  2. AVN
  3. His bundle
  4. Left posterior/right bundle
  5. Purkinje fibres
35
Q

Which is the dominant node?

A

The sinoatrial node acts as primary pace maker and is regulated by the autonomic nervous system. The other nodes do depolarise but are overwritted by SAN

36
Q

Whats the heart rate formula?

A

HR=241 x body mass to power of -1/4

37
Q

How does it depolarise/repolarise?

A

4 - slow depolarisation. Moves from -60mV slowly to resting membrane potential. This is due to small Na+ movements into cell via HCN channels. K+ are closed.

0 - rapid depolarisation when hits -40mV. Fast Na+ channels open and ions flood in.

1 - action potential hits +20mV and fast Na+ channels close

2- plataeu, where Ca2+ enters via voltage sensitive channels

3 - repolarisation with max influx of Ca2+, leads to K+ channels openning.

38
Q

What happens during contraction/systole?

A

During phase 2, the action potential comes across the myocyte and travels down the T-tubule system. This opens the DHPR channels allowing Ca2+ to enter the cell. This influx leads to SR to release Ca2+ via ryanodine receptor channels. These Ca2+ binds to troponin C and allows contraction.

39
Q

What happens during relaxation/diastole?

A

Ca2+ is removedvia facilitated transport (Na+/Ca2+) and pumps (Ca2+ATPase on SR)

There is refractory period and allows time for ventricles to empty and then refill.

40
Q

What are the 7 events of the cycle?

A
  1. Atrial contraction - blood fills atria and blood pushed to ventricle
  2. Isovolumetric contraction - ventricle contracts but AV closed so high pressure
  3. Rapid ejection - SL valves open and ventricles eject to aorta/pulmonary artery
  4. Reduced ejection - SL valves remain open, and ventricles stop contracting
  5. Isovolumetric relaxation - ventricles are relaxed, and all valves are closed
  6. Rapid filling - AV valves open, blood fills ventricles slowly again
  7. Reduced filling - ventricles continue to fill as venous pressure is greater than ventricular pressure
41
Q

What are the heart sounds?

A

4 normal sounds S1=S4

S1 - AV valves and longer low frequency
S2 - SL valves with a shorter higher frequency

S3-S4 not usually heard

Listen between ribs 3 & 6. Follow PAM (pumonic, aortic and mitral valves)

42
Q

What are the points of an ECG?

A

P wave - atrial depolarisation
QRS complex - ventricular depolarisation
T wave - repolarisation of ventricles
PR interval - AV conduction time
ST segment - isoelectric period with both ventricles depolarised
QT interval - both ventricle de-/re-polarisation
RR interval - mostly regular

43
Q

What details do the ECG give?

A

Info on the heart rate, rhythm and origin of excitation, the sizes of the heart chambers, spread of impulse, decay of excitation and orientation of heart

Not on pumping action or potentials from the points of excitation.

44
Q

What are the types of cardiac block?

A

1st degree - prolonged PR intervals (AV conduction time)
2nd degree - AVN fails to transmit all atrial impulse. More P waves than QRS (atrial not ventricle)
3rd degree - Atrial to ventricular transmission fails

45
Q

What is the terminology with heart rates?

A

Normocardia - normal heart rate
Tachycardia - excessive heart rate. Sinus tachycardia seen in fever, also in hypothyroidism and low atrial pressure
Bradycardia - lower heart rate, sinus bradycarcia seen in very fit individuals but could be abnormal

46
Q

What is the cardiac output?

A

The measure of cardaic work and the volume pumped into the aorta per time.

Equals the venous return (volume back in right atrium per time)

CO = stroke volume x heart rate

47
Q

What influences heart rate?

A

Parasympathetic - Vagus nerve
Sympathetic - Adrenergic fibres

48
Q

What happens in parasympathetic innervation of the heart?

A

The vagus nerve innervates the SA/AV node to decrease the heart rate.

SA node - releases ACh which opens fewer Na+ for If. The muscarinic receptor antagonist to increase heart rate

AV node - increases refractory period and decreases conduction

49
Q

What happens in the sympathetic innervation of the heart?

A

Innervates the SA/AV nodes, atria and ventricles. Works to increase heart rate.

SA node - releases noradrenaline to open more Na+ channels for If. Beta-adrenoceptor antagonists slow HR.

AV node - decreases refractory period and increases conduction.

50
Q

What is stroke volume?

A

The amount of blood put out by the left ventricle in one contraction

51
Q

What is myocardial contractility?

A

The inotropic status.

A measure of the force generated by the myocytes and influenced by the innervation.

Atrial myocytes respond to ACh (M2 parasympathetic) and NAd (B1 sympathetic). Ventricular is only responsive to NAd.

Parasympathetic controls the ventricles via control of the pre-synaptic symp nerve attenuating noradrenaline release.

52
Q

What is preload?

A

The filling pressure of the heart, indicated by the central venous pressure/the degree of stretch of ventricular mypcardium/

53
Q

What affects venous return?

A

Volume of blood in the system - displacement of blood in veins (vasoconstructor) increases return

Skeletal muscle activity - in lower extremity massages blood back to heart

Thoracic pump - when breathing the intrathoracic pressure falls, leading to reduction in central venous pressure. If pools in leg, can lead to fainting.

54
Q

What is the Frank-Starling method?

A

Reservoir raises
Pressure causing ventricle filling increases
More blood enters ventricles
Ventricle muscles stretch
Responds with stronger contraction

55
Q

What is afterload?

A

The pressure which the heart ejects. An increase in arterial pressure leads to increase resistance to flow from left ventricle.

To maintain stroke volume at an increased afterload, the heart has to contract more forcefully.

This is influenced by NAd which produces an inotropic effect (improving force of contraction)

56
Q

What is perfusion pressure?

A

Adequate peripheral pressure allows the perfusion of tissues. Failure of this results in circulatory shock leading to hypoxia and necrosis. Excessive leads to fluid exudation from capillary damage.

57
Q

What is systemic arterial pressure?

A

Mean arterial pressure = diastolic pressure + systolic arterial pressure - DAP / 3

SAP - peak pressure in arteries when LV is ejecting bloody during systole

DAP - residule pressure in arteries when LV is filling.

58
Q

What is short term regulation of the heart rate?

A

Baroreceptors are fast acting non-encapsulating nerve endings in adventicia of the arteries. They terminate in the medulla oblongata. When stretch they increase firing leading to increase BP

59
Q

What is another equation for mean aterial pressure?

A

MAP = (SV x HR) x Total peripheral resistance

60
Q

What is the long term regulation of heart rate?

A

Fluid control with the RAAS.

Low blood pressure leads to decrease renal prefusion and renin is released from renular cells.

61
Q

What happens when something haemorrhages?

A

Blood loss leads to:
-decrease in aterial pressure and baroreceptor reflex firing increases cardiac output, HR and SV
-decrease in benous return decreases discharge in atrial volume receptors leading to anti diuretic hormone release. This constricts renal vasculature and intitiates RAAS
- All this increases BV and arterial pressure
- Shock in the system leads to faint BP.

Patient cool, pale with moist skin]

62
Q

What happens when something haemorrhages?

A

Blood loss leads to:
-decrease in aterial pressure and baroreceptor reflex firing increases cardiac output, HR and SV
-decrease in benous return decreases discharge in atrial volume receptors leading to anti diuretic hormone release. This constricts renal vasculature and intitiates RAAS
- All this increases BV and arterial pressure
- Shock in the system leads to faint BP.

Patient cool, pale with moist skin

63
Q

What happens during exercise?

A

Large sympathetic discharge, and generalised vasoconstriction leading to increased venous return and cardiac output (SV and HR)

Blood is released from venous reservoirs
Vasodilation in cardiac muscle and skin and vasoconstriction in inactive tissues
Increase muscle blood flow and capillary recruitment for nutrient delivery and metabolite removal
Metaboreceptors in skeletal muscles, k+ and Lactate sensors

BVetMed 1 (53 decks)

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