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Year 1 MBChB Cardiology > Physiology > Flashcards

Physiology Flashcards

1
Q

Intercalated discs contain what 2 things + function?

A

Desmosomes (tension) and gap junctions (electrical spread of signal)

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2
Q

AVN has …. cells, is …. conducting and is the only point …..?

A

Smaller, slow and of electrical activity between atria and ventricles

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3
Q

What does sympathetic vs parasympathetic innervation do to HR and AVN delay?

A

Speeds up and decreases vs slows down and increases

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4
Q

What dominates the HR under resting conditions?

A

Vagal tone

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5
Q

What area of the heart does the vagus nerve not supply that the sympathetic does?

A

Myocardium

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6
Q

Which neurotransmitter acts on which receptor in parasympathetic vs sympathetic control of the heart?

A

ACh on M2 receptors vs NA on beta 1 receptor

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7
Q

Name a competitive inhibitor (muscarinic antagonist) of ACh that is used in bradycardia?

A

Atropine

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8
Q

Effect of sympathetic and parasympathetic innervation on the pacemaker potential slope?

A

Parsympathetic decreases and sympathetic increases

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9
Q

Which blood vessel supplies the SAN?

A

Right coronary artery

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10
Q

What creates the striated appearance of cardiac muscle?

A

Myofibrils of actin and myosin in sarcomeres

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11
Q

Shape and colour of actin + myosin filaments?

A

Actin (thin and pale) + myosin (thick and dark)

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12
Q

Which way does actin and myosin slide?

A

Actin slides over myosin

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13
Q

What 2 things is required to allow cross bridge formation?

A

ATP

Calcium

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14
Q

What is the role of calcium in sliding of filaments?

A

Forms cross bridge by binding to troponin and shifting tropomyosin out of the actin cleft

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15
Q

What is meant by the refractory period?

A

Period following action potential where it is not possible to generate another action potential

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16
Q

What are the 2 phases where a new action potential cannot be generated?

A

Phase 2 and 3

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17
Q

What is the clinical benefit of the refractory period?

A

Prevents tetanic contractions of the heart

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18
Q

Define stroke volume + normal value + how to calculate?

A

Volume of blood ejected by each ventricle per heart beat + 70 ml + EDV-ESV

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19
Q

EDV/pre-load is determined by ….. which is determined by which 3 things?

A

Venous return + skeletal, respiratory pump and venoconstriction

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20
Q

Describe the Frank-Starling Law of the Heart + sympathetic effect?

A

Greater EDV the greater the SV + shift curve left

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21
Q

Other effect of stretching the heart fibers to increase SV?

A

Stretch increases affinity of troponin C for Ca

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22
Q

ESV/afterload is determined by?

A

The resistance against which the heart has to pump into

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23
Q

How does the Frank-Starling law compensate partially for decreased stroke volume?

A

EDV increases (due to failure to pump full SV) so force of contraction increases

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24
Q

What does chronotropic mean + can this be affected by sympathetic or parasympathetic innervation?

A

Speed of the heart + both

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25
What does ionotropic mean + can this be affected by sympathetic or parasympathetic innervation?
Force of contraction + only sympathetic (para does not supply myocardium)
26
What is meant by cardiac output + how to calculate?
Volume of blood pumped out by each ventricle per minute + SV x HR
27
How much blood fills the ventricles in passive filling?
80%
28
Pressure in the atria and ventricles + aorta is normally?
Close to zero + 80 mm Hg
29
Duration of diastole and systole?
0.5 seconds and 0.3 seconds
30
Are the ventricles filled in isovolumetic contraction and relaxation + explain the state of the ventricles?
Filled in contraction and empty in relaxation + in a closed box (all valves shut)
31
What produces the dicrotic notch in the aortic pressure curve?
Aortic valve closing
32
Cause of S1, S2, S3 and S4?
Systole, diastole, pathologic in younger people but CHF in older, stiff ventricles e.g. LVH
33
Splitting of S2 is heard on ... and is caused by + why?
Inspiration and pulmonary valve closing later than aortic + intrapulmonary pressure decreases so venous return increases
34
Cp needs to be around .... to stop blood flow and below .... to allow blood flow?
120 and 80 mm Hg
35
Which sort of blood flow can be heard through a stethoscope?
Turbulent
36
What is the 1st Korotkoff sound?
Peak systolic pressure
37
What are the 2nd and 3rd Korotkoff sounds?
Intermittent sounds of turbulent flow
38
What is the 4th Korotkoff sound?
Muffled sound
39
What is the 5th Korotkoff sound?
No sound (minimum diastolic)
40
What are the 4 formula for calculating MAP?
2 x diastolic + systolic]/3 1/3 pp + diastolic CO x SVR SV x HR x SVR
41
What is the normal range for MAP?
70-100 mm Hg
42
What MAP is needed to perfuse organs?
At least 60 mm Hg is needed
43
How to calculate pulse pressure?
Systolic - diastolic pressure
44
What regulates long term vs short term control of MAP?
Blood volume vs baroreceptors
45
Increased MAP causes baroreceptors to .... firing?
Increase
46
Which nerves innervate the carotid vs aortic baroreceptors fire through?
CN IX (glossopharyngeal) + CN X (vagus)
47
Decreased MAP baroreceptor summary?
Decreased firing, decreased vagal tone, increased sympathetic tone (increases HR) and increased veno/vasoconstrictor tone
48
What causes postural hypertension + drug that can cause it (+ example) + key value for postural hypertension
Failure of baroreceptors + alpha 1 antagonist (doxazosin) drop of 20 mm Hg
49
How much of the body fluid is extracellular vs intracellular fluid + what 2 things make up the ECFV?
1/3 vs 2/3rds + PV and IFV
50
What is the function of renin in the RAAS + where is it released from + 2 stimuli?
Stimulates conversion of angiotensinogen to angiotensin I + kidneys + low plasma volume and low Na
51
What is the function of ACE + where is it released from?
Converts angiotensin I to angiotensin II + pulmonary vascular endothelium
52
4 effects of angiotensin II?
Aldosterone release, vasoconstriction, increased ADH and thirst
53
What is the function of aldosterone in the RAAS + where is it released from?
Na+ and water retention + adrenal cortex (above the kidneys)
54
Where is ANP + BNP stored + what stimulates release?
Atria + ventricle + distension of the heart
55
Molecule that opposes the RAAS + 3 effects?
ANP + increases Na and water retention and decreases renin release
56
What does osmolality mean?
The amount of solute in a liquid
57
What 2 things trigger ADH release + where is it normally produced and stored?
Low plasma volume and increased osmolality + produced in hypothalamus and stored in pituitary
58
ADH causes which 2 things?
Na and water retention and vasoconstriction
59
ADH effect is most important in?
Hypovolaemic shock
60
Blood flow is proportional to .... and .... and inversely proportional to the ...?
Blood viscosity and length of blood vessel and radius of blood vessel
61
What is SVR determined by?
Radius of the arterioles
62
What is meant by vasomotor tone + what causes it?
Vascular smooth muscle being partially constricted + tonic discharge of the sympathetic system
63
Only place of parasympathetic innervation of vascular smooth muscle?
Penis and clitoris
64
Alpha receptors are predominant in?
Skin, gut and kidney
65
What is the effect of angiotensin II on vascular smooth muscle?
Vasoconstriction
66
How does metabolic hyperaemia override vasomotor tone?
Metabolic waste products cause local vasodilation
67
Explain the effect of sheer stress on endothelium?
Causes calcium release which activates NOS to synthesise NO from L-arginine L-arginine causes cGMP which facilitates relaxation
68
Describe myogenic response to stretch?
Increased MAP causes vasodilation and decreased MAP causes vasoconstriction
69
Blood flow to the kidney and gut is .... during exercise and .... to the heart and muscles?
Decreased and increased
70
How does shock cause cell death?
Decreased tissue perfusion causes anaerobic metabolism and cell death
71
How does hypovolaemic shock arise?
Loss of blood volume leads to decreased SV
72
How does cardiogenic shock arise + Frank-Starling curve shape?
Decreased myocardial contractility leads to decreased SV + rainbow shape
73
How does tension pneumothorax lead to obstructive shock?
Increased intrathoracic pressure leads to decreased venous return
74
How does neurogenic shock arise?
Loss of sympathetic innervation causes vasodilation and decreased HR
75
How does vasoactive shock arise?
Release of vasoactive mediators leads to increased vasodilation
76
Compensatory blood volume loss mechanisms compensate until?
30% volume is lost
77
General treatment of shock + exception?
ABCDE and fluids (except cardiogenic)
78
Which organ has the greatest oxygen demand?
The heart
79
How does the heart increase oxygen supply + 2 ways?
Increases coronary blood flow + metabolic hyperaemia or NA on beta 2 receptors
80
Beta 2 receptors are mainly found where in the heart?
The small coronary arteries
81
When does peak coronary flow occur?
Diastole
82
Which brain matter - grey or white - is very sensitive to hypoxia?
Grey matter
83
If MAP rises, cerebral vessels ....?
Constrict
84
When does autoregulation of cerebral blood flow fail + cause fainting?
MAP less than 60 or greater than 160 mm Hg + below 50
85
Decreased PCO2 results in cerebral vasodilation or vasoconstriction + clinical relevance?
Vasoconstriction + hyperventilation causes fainting
86
Normal intracranial pressure?
5-15 mm Hg
87
Increasing intracranial pressure does what to cerebral blood flow?
Decreases it

Year 1 MBChB Cardiology (15 decks)

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