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eBMS2031 > CARDIOVASCULAR SYSTEM > Flashcards

CARDIOVASCULAR SYSTEM Flashcards

1
Q

What are the functions of the cardiovascular system

A

O2 and nutrients for our tissues

Removal of CO2 and waste

Hormone transport

Defence (antibodies, white blood cells)

Thermoregulation

Reproduction

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2
Q

Outline the purposes of the harts 4 chambers

A

right atrium where blood enters from superior and inferior vena cava.

right ventricle contracts blood into pulmonary artery to lungs

left atrium takes oxygenated blood from pulmonary veins

left ventricle pumps blood into aorta

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3
Q

Outline structure of the heart

A

4 chambers RA RV LA LV

separating sides is a septum.

aortic and pulmonary valves

atrioventricular valves (mitral, left tricuspid, right)

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4
Q

Outline electrical coupling of cardiac myocytes

A

gap junctions made from desmosomes in intercalated disks, allow ion to pass from one muscle to the next

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5
Q

outline electrical conduction pathway of the heart

A 
SA node 
atrial cells
AV node
bundle of his
purkinje fibres
ventricular cells
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6
Q

why can pacemaker cells spontaneously generate APs

A

the unstable resting potential easily tips past threshold mpot

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7
Q

describe pacemaker AP shape

A

No fast Na channels

Slow influx of Na starts

Ca influx responsible for upstroke/depolarisation

K efflux for repolarisation

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8
Q

how long does it take for atrial excitation from the SA node

A

0.09s

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9
Q

what causes the delay while passing through the AV node

A

These myocytes have less gap junctions, slowing the electrical signals.

This delay ensures all atrial cells are excited before ventricle cells are excited

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10
Q

How long does it take for ventricular excitation from the AV node

A

0.06s

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11
Q

describe ventricular AP shape

A

Na influx for depolarisation

at -40mV slow Ca channels open causing influx and plateau phase.

K efflux causes repolarisation

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12
Q

What is the purpose of the plateau phase

A

Ensures contraction by prolonging AP of ventricular cells.

Also prevents arrythmia.

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13
Q

Outline calcium induced calcium release

A

AP triggers L type voltage gated Ca channels to open.

external Ca binds to ryanodine receptor.

receptor opens allowing SR Ca to be released for cross bridge cycling.

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14
Q

Why is the extra SR concentration of Ca needed

A

extracellular Ca influx is not enough for efficient contraction from cross bridge cycling so extra SR stores are needed.

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15
Q

What does the P wave represent

A

excitation/depolarisation of atrial muscle cells

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16
Q

What does the QRS complex represent

A

little trough from atrial relaxation/repolarisation.

spike from ventricular excitation/depolarisation

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17
Q

Why is QRS complex much bigger than P wave

A

many more ventricular cells than atrial cells therefore depolarisation response (qrs complex) is bigger.

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18
Q

What does the T wave represent

A

ventricular relaxation/repolarisation

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19
Q

Why is the T wave positive on ECG

A

Repolarisation occurs from top to bottom of ventricular cells due to difference in K channels.

Repolarisation usually negative but moving in opposite direction means it is positive

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20
Q

What is a cardiac arrhythmia

A

irregular heartbeat

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21
Q

describe shift of pacemaking from SA node

A

normal sinus rhythm from SA node as they fire the fastest.

If SA node damage, leader shifts to next fastest, the AV node then purkinje fibres.

Break in middle of chain, atria of heart go by SA node and ventricles go by purkinje fibres

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22
Q

describe abnormal impulse formation of SA node

A

SA node rhythm is abnormal so therefore whole heart rate is abnormal.

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23
Q

describe blocking/delay of conduction of impulse through heart

A

block impulse travel through AV node

Ischaemia

compression of AV node by scar tissue

inflammation of AV node (fever)

extreme stimulation of heart by parasympathetic nerves

24
Q

describe spontaneous generation of abnormal impulses in any region of the heart

A

Ecotopic focus (the place of abnormal impulses) starts going faster than the SA node.

E.g: ventricular fibrillation where purkinje fibres are faster, excitation/contraction so quick that they quiver.
Shock from defibrillator resets.

25
Q

Why does blocking ANS innovation of heart increase heart rate

A

At rest, there is always some parasympathetic activation of the SA node. therefore without this parasympathetic (which slows HR) the HR increases

26
Q

how does HR increase during exercise

A

plasma epinephrine increases, increasing sympathetic activation on beta receptors, decrease in parasympathetic innovation

therefore increase in HR

27
Q

What is cardiac output

A

volume of blood pumped by each ventricle of the heart per minute.

CO = HR x SV (L/min)

28
Q

Are right and left CO equal

A

right CO = pulmonary circuit

left CO = systemic circuit

yes equal in a healthy person

29
Q

What is stroke volume

A

volume of blood ejected with each ventricular contraction (ml/beat)

30
Q

How is stroke volume calculated

A

EDV-ESV

31
Q

2 ways to increase SV to increase CO

A

lengthening ventricular muscle cells

increasing calcium available for contraction

32
Q

how does lengthening muscle cells increase SV to increase CO

A

Inc pressure, stretches cells out

more crossover between actin and myosin, more crosss bridging, stronger contraction

more blood ejected = increase SV and CO

33
Q

how does increasing Ca increase SV and CO

A

Sympathetic innervation

noradrenaline activates beta receptors

causes production of cAMP causing kinase production

change conformation of L type channels and ryanodine receptor

causes more Ca release, cross bridge cycling therefore more force and SV and CO.

34
Q

How do we increase heart rate to increase CO

A

increase sympathetic innervation of SA node = inc HR

decreases parasympathetic innervation of SA node = inc HR

35
Q

What is hypertension

A

consistently above 140/90

36
Q

What is hypotension

A

consistently below 100/60

37
Q

How do you calculate pulse pressure

A

PP = SBP - DBP

38
Q

How do you calculate MAP

A

DBP + 1/3(PP)

CO x TPR

39
Q

2 types of auto regulation of blood flow to parts of body

A

metabolic control

myogenic mechanism

40
Q

2 types of coordinated control of blood flow to parts of body

A

sympathetic innovation

hormones

41
Q

outline metabolic control of auto regulation of arterioles

A

dilation of arterioles caused by local chemical factors

increase in H CO2 adenosine during metabolic activity

42
Q

outline myogenic mechanism of auto regulation of arterioles

A

pressure autoregulation

stretch is detected by stretch receptors in smooth muscle causing contraction

allows for constant blood flow as contraction cancels out increase in arterial pressure

43
Q

outline sympathetic innovation coordinated control of arterioles

A

sympathetic nerves release noradrenaline on alpha receptors causes contraction

44
Q

outline hormones coordinated control of arterioles

A

adrenaline - dilation

angiotensin, vasopressin - constriction

atrial naturietic peptide - dilation

45
Q

Outline baroreceptor reflex

A

Decrease in MAP detected by baroreceptors in aortic arch, carotid sinus. fire less with decrease

project afferently to medullary cardiovascular centre in brain stem

initiates ANS to increase MAP

46
Q

In the baroreceptor reflex how is CO, HR, SV increased

A

reducing parasympathetic, decrease SA node decrease HR

increase sympathetic, increase SA node increase HR

increase sympathetic in ventricles, increase force/contraction, increase SV CO

increase sympathetic in veins, increase venous pressure, venous return, increase EDV, SV, CO

ULTIMATELY ALL INCREASE CO WITH INCREASES MAP

47
Q

In the baroreceptor reflex how does increase TPR increase MAP

A

sympathetic activation of arterioles, increase constriction, increase TPR, increase MAP

48
Q

Types of diffusion in capillaries

A

direct diffusion: lipid soluble and gases

diffusion through pores: lipid insoluble glucose, ions and aa

bulk flow: water

vesicular transport of large molecules: some hormones

49
Q

2 forces driving and opposing capillary filtration

A

higher hydrostatic pressure = filtration of fluid out of capillaries

higher plasma osmotic (colloidal oncotic) pressure = absorption of fluid into capillaries

50
Q

where does the filtered fluid from plasma in the interstitial space go

A

taken up into the lymphatic system then referred to as lymph

empty into subclanion vein

51
Q

what is oedema

A

excess fluid accumulation in interstitial fluid

caused by

  • increase capillary blood pressure
  • decrease osmotic pressure
  • poor lymphatic drainage
52
Q

3 ways venous return is regulated

A

pressure gradient

skeletal muscle pump

respiratory pump

53
Q

explain pressure gradient of venous return

A

sympathetic venous contraction, increase venous pressure, increases flow into atrium

54
Q

explain skeletal muscle pump in venous return

A

skeletal muscles in legs contraction, constricts veins, aids flow up to heart

55
Q

explain respiratory pump in venous return

A

inspiration occurs, diaphragm pushes down decreasing intrathoracic pressure and increasing in abdomen. squeezes abdominal veins, increasing venous pressure and venous return

eBMS2031 (6 decks)

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