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Cardiovascular System > CVS Physiology > Flashcards

CVS Physiology Flashcards

1
Q

Define the word “cardiovascular”

A 
Cardio = heart pump
Vascular = vessels
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2
Q

Role of the cardiovascular system

A 
Bulk flow system transporting:
o	O2 and CO2
o	Nutrients
o	Metabolites
o	Hormones
o	Heat
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3
Q

Which circulations do the left and right side of the heart pump out to?

A

Right side = pulmonary circulation

Left side = systemic circulation

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4
Q

Are the heart pumps in parallel or series? Significance of this

A

Series.
All the blood that flows from right side of heart must then flow through left side of heart.
Output of R and L sides must be equal, if not over time all the blood would end up in one or the other circulations

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5
Q

Are vascular beds in parallel or series? Significance of this

A

MOST are in parallel.
Ensures blood goes to all the areas of the body at the same time, ensuring all tissues get oxygenated blood. Allows for regional redirection of blood (some regions require more blood)

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6
Q

What is the total cardiac output (ml/min)

A

5000ml/min

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7
Q

Which vascular beds are in series? And why?

A

Between the gut and liver. Nutrients are picked up in the gut and moved to the liver

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8
Q

What is mean arterial pressure?

A

The high pressure blood coming out of the left side of the heart

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9
Q

What is central venous pressure?

A

The low pressure blood coming back into the right side of the heart

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10
Q

How is the resistance controlled?

A

By the radius of the vessels (arterioles) going to the vascular beds

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11
Q

Explain the features and functions of elastic arteries

A

Features: wide lumen, elastic wall
Function: absorb increase pressure during the ejection phase. The absorbed energy used to push back on blood during relaxation phase to maintain pressure and keep blood moving forward

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12
Q

Which arteries are elastic?

A

Aorta

Pulmonary trunk

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13
Q

Features and function of arteries

A

Features:

  • Wide lumen
  • Muscular walls (NOT elastic)
  • Very low resistance

Function: get blood out as easily as possible

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14
Q

Features and functions of arterioles

A

Features:

  • narrow lumen
  • thick muscular wall

Function:
- control resistance therefore allowing regional redirection of blood

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15
Q

Features of venules and veins

A

Features:

  • wide lumen
  • distensible wall (capable of being swollen or dilated)
  • low resistance

Function:
- capacitance vessels - able to store a lot of blood

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16
Q

Volume of blood in veins and venules

A

2/3 of blood volume in veins and venules moving very slowly back to heart

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17
Q

Features and function of capillaries

A

Features:

  • narrow lumen
  • thin wall

Function:
- exchange vessels

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18
Q

What seperates the two pumps in the heart?

A

Interventricular septum

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19
Q

What is the wall of the heart called? Which side is thicker & why?

A

Myocardium

Left side thicker as has to have higher pressure to push blood through systemic circulation

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20
Q

Which artery pumps to systemic circulation

A

Left side of the heart through the aorta

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21
Q

By which vein does deoxygenated blood return to the heart & which compartment?

A

Right sided atrium
Superior vena cava = blood from the top of the body
Inferior vena cava = blood from bottom of the body

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22
Q

Where does the deoxygenated blood from the right atrium go?

A

Enters right ventricle and pumped through pulmonary circulation via pulmonary trunk.
L and R pulmonary trunk taking blood to each lung

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23
Q

How does the oxygenated blood from lungs return to heart?

A

By 2 pulmonary veins into the left atrium

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24
Q

Which valves prevent back flow into the ventricles?

A

Aortic valve between L ventricle and aorta

Pulmonary valve between R ventricle and pulmonary artery

25
Q

Structure of the aortic and pulmonary valve

A

Semi-lunar (allows blood to go out the heart but not back)

26
Q

Which valves separate the L atrium from L ventricle and R atrium from R ventricle?

A

L atrium and L ventricle = mitral valve
- 2 cusps

R atrium and R ventricle = tricuspid valve
- 3 cusps

27
Q

What prevents valves inverting when ventricles contract?

A

Cordae tendineae
+ papillary muscles which contract at same time as heart (heart shortens when it contracts so papillary muscles keep tendons at appropriate length)

28
Q

What is the cardiac functional syncytium?

A

Syncytium is formed by fusion of individual cells. In cardiac muscle the cells are individual (don’t fuse) but act as if the the cardiac muscle is one big muscle.

Both electrically and physically connected

29
Q

How are cardiac muscle cells connected? What does this allow?

A

By gap junctions (protein channels connecting cytoplasms of 2 cells together)

  • Allows electrical current and small signalling molecules to pass through
  • If one cell depolarises the neighbouring cell will to = both contract

By desmosomes = physical connections preventing cells from pulling apart when they contract

30
Q

How does the cardiac action potential differ from the skeletal muscle action potential

A

Cardiac muscle = 200-250milliseconds

Skeletal muscle = 1-2milliseconds

31
Q

What are the 2 consequences of the longer action potential in cardiac muscle

A
  1. During plateau phase calcium comes into cell contributing to excitation, contraction and coupling. Also triggers cross bridge formation
    • more calcium = more cross bridges
    • calcium gated channels allow amount of calcium to be regulated
    • regulates contraction strength
  2. Long refractory period
    • cardiac muscle cant stay contracted
    • needs to contract, relax, contract to allow heart to fill with blood
32
Q

Compare action potential difference between between non-pacemaker tissue and packemaker tissue

A

Non-pacemaker sits at -90mV and doesn’t do anything until instructed by neighbours (gap junctions)
- rapid depolarisation, long plateau, repolarisation

Pacemaker potential spontaneously depolarises towards threshold
- action potential evoked (depolarises), then spontaneously depolarises again

33
Q

List the elements of the heart involved in conduction

A 
Sinoatrial node
Annulus fibrosus 
Atrioventricular node (AV node)
Bundle of His 
Purkinje fibres
34
Q

Role of the sinoatrial node

A

Fastest pacemaker (by definition the pacemaker as reach threshold soonest)
Spreads from cell-cell creating wave of depolarisation (0.5m/sec)
Found in the right atrium

35
Q

Role of annulus fibrosus

A

Separates the atria and ventricles
Only non-conducting part of the heart - in healthy heart depolarisation evoked in ventricles can’t get through and forced to go through AV node

36
Q

Role of atrioventricular node

A

Conducts VERY slowly (0.05m/sec) - the delay box of heart

Allows atria time to depolarise and contract to expel blood into ventricles before ventricles contract and expel blood

37
Q

Role of the Bundle of His

A

Bundle of His travels down interventricular septum splitting into purkinje fibres
Ensure depolarisation spreads through whole ventricle at same time to evoke sharp contraction = big pressure to eject blood

38
Q

Role of Purkinje fibres

A 
Conduct rapidly (5m/sec)
Depolarisation spread to all parts of heart at same time to ensure coordination of contraction
39
Q

Correlate the P wave, QRS complex, and T wave with electrical events in heart

A

P wave: wave of depolarisation across the atria
QRS complex: wave of depolarisation across ventricles
T wave: repolarisation of ventricles

40
Q

What information does the ECG give us (3)?

A

Information on spread of depolarisation
Disorders of conduction
Whether the heart rhythm is correct

41
Q

How many seconds does each large square on ECG correlate to?

A

0.2 seconds

42
Q

What is Heart block?

A

Depolarisation doesn’t spread from atria through AV node therefore ventricles aren’t depolarised

43
Q

What is 1st degree heart block?

A

Abnormal delay between atrial depolarisation and ventricular depolarisation
Most likely in AV node
P, QRS and T visible delay between P and QRS

44
Q

What is 2nd degree heart block

A

Some of depolarisation don’t get through at all
E.g. P wave which isn’t followed by any QRS, T
Gradually longer interval between P and QRS complex

45
Q

What is 3rd degree block

A

No transmission between atria and ventricle
P waves occurring as they should but not followed by QRS
Another pacemaker in ventricles has taken over and makes ventricles depolarise from different place
Upside down T from repolarisation

46
Q

What is atrial flutter (supra ventricular tachycardia)

A

Normal P, QRS, T but compressed so P wave occurs on back of previous T wave
Each depolarisation occurs much faster than it should

47
Q

What is atrial fibrillation

A

No coordination of P wave
Individual cells depolarising at different times across the atria
Uncoordinated depolarisation and contraction
Occasionally depolarisation gets through AV node to ventricles evoking QRS, T wave

48
Q

What is ventricle fibrillation

A

Very dangerous
Ventricular muscle quivers not producing any coordination
Defibrillator required - resets the pacemaker system by stopping the heart

49
Q

What does the PR interval on an ECG indicate?

A

Time from start of P wave to start of the QRS complex
Time from start of atrial depolarisation to start of ventricle
depolarisation (major time here is time taken for transmission through AV node)

0.12-0.2 seconds

50
Q

What does QRS complex on ECG indicate?

A

Time for whole ventricle to depolarise (first cells of ventricles until last)
Determined by Purkinje fibres in bundle of His

0.08seconds

51
Q

What does the QT interval on ECG indicate?

A

Time from start of QRS complex until end of T wave
Measures time when ventricles are depolarised

Varies with heart rate (0.42 at 60bpm)

52
Q

How to measure heart rate from ECG?

A

Count the R waves in 30 large squares (6 seconds) and multiply by 10

53
Q

What is normal bpm, bradycardia and tachycardia?

A 
Normal = 60-100bpm
Bradycardia = <60bpm
tachycardia = >100bpm
54
Q

What is the ST segment?

A

the gap between the QRS complex and the T-wave

55
Q

What is STEMI vs. NSTEMI? Which is worse?

A 
STEMI = ST elevated myocardial infarction 
NSTEMI = non-ST elevated myocardial infarction

STEMI is worse than NSTEMI

56
Q

What causes the 4 heart sounds?

A

1st - closure of the AV (mitral and tricuspid valves)
2nd - closure of the semi-lunar (aortic and pulmonary valves)
3rd - rapid filling phase
4th - active filling phase

57
Q

What does the period between the 1st and 2nd heart sounds represent?

A

Systole

58
Q

What fraction of the cardiac cycle do systole and diastole take up

A

Systole 1/3

Diastole 2/3

Cardiovascular System (37 decks)

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