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ESA 2 - RJS > CVS > Flashcards

CVS Flashcards

0
Q

What affects the rate of diffusion?

A

Area
Diffusion resistance - Nature of barrier, molecules and distance
Concentration gradient

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1
Q

What do we have a cardiovascular system?

A

Supplies cells in the body with metabolic needs because simple diffusion would be too slow

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2
Q

What must be kept at an appropriate rate to ensure concentration gradients during diffusion?

A

Flow of blood else gradients driving exchange will dissipate

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3
Q

How much blood does the cardiovascular system have to deliver?

A

Between 5 and 25 L/min

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4
Q

Which organs must the blood flow be maintained at a constant rate?

A

Brain and kidneys

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5
Q

What is the blood flow required to the brain and kidneys?

A

Brain - 0.75 L/min

Kidneys - 1.2 L/min

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6
Q

What are the components of the circulation?

A

Pump - heart
Distribution vessels - arteries
Flow control - resistance vessels (arteriolar, pre-capillary sphincters)
Capacitance - store of blood (veins)

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7
Q

What is the role of resistance vessels in the circulation?

A

Allows for restricted flow to parts of the body that are easily perfused and drives blood to parts that are not easily perfused
E.g. Arteriolar, pre-capillary sphincters

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8
Q

What is the role of capacitance vessels in circulation?

A

Ability to cope with changes in cardiac output. Stores blood which can be called upon to cope with temporary imbalances
E.g. Veins

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9
Q

What is the difference between elastic arteries and muscular arteries?

A

Elastic arteries - expand slightly with each heart beat (greater amount of elastic fibres)
Muscular arteries - regulate amount of blood reaching an organ/tissue, regulates blood pressure, branch into arterioles

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10
Q

Describe the flow of structures in the circulation system from heart to capillaries
I.e. The order in which they occur

A

Large elastic/conducting arteries —> medium muscular/distributing arteries —> arterioles —> metarterioles —> capillaries

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11
Q

Describe the flow of structures in the circulation system from capillaries to heart
I.e. The order in which they occur

A

Capillaries —> post capillary venules —> venules —> medium veins —> large veins

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12
Q

How is the diameter of arteries and arterioles controlled?

A

By autonomic nervous system

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13
Q

What are the two types of capillary walls?

A

Continuous & fenestrated

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14
Q

What can capillaries be surrounded by?

A

Pericytes - contractile cells

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15
Q

What are sinusoids and where are they found?

A

Capillaries that have a larger diameter and may contain special lining cells and incomplete basal lamina - increase permeability
Found in liver, spleen, bone marrow

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16
Q

What is the difference in restructure between vein and artery?

A

Similar structure except that wall is thinner and lumen wider and irregular
Veins contain semilunar paired valves - blood flow in 1 direction

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17
Q

What occurs to the veins if blood pressure is not maintained?

A

They collapse

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18
Q

What are the two factors that most effect blood flow in veins?

A

‘Muscle-pump’ action in the leg and pressure factors in the abdominal and thoracic cavities

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19
Q

What are the valves located in the left ventricle?

A

Tricuspid and pulmonary

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20
Q

What are the two values located in the right ventricle?

A

Mitral and aortic

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21
Q

What are the six properties of cardiac muscle allow heart to operate as a pump?

A 
Striations
Branching
Centrally positioned nuclei
Intercalated discs - electrical and mechanical coupling with adjacent cells
Gap junctions
T tubules inline with Z bands
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22
Q

How are action potentials generated in the heart?

A

Pacemaker cells (SA node) generate electrical activity which leads to activity in other cells

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23
Q

How long is cardiac contraction (systole)?

A

280ms

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24
What is systole?
Period in which the myocardium is contracting
25
What is diastole?
Relaxation in-between contractions
26
How long does diastole last?
700ms
27
How does atrial systole occur?
SA node fibres an action potential - spreads over atria - atrial systole
28
What happens at the AV node?
Action potential is delayed for 120ms before spreading down septum
29
What causes the movement of blood from atrium to ventricle?
Intraventricular pressure falls below atrial pressure - rapid filling phase
30
How do the atrioventricular valves close?
Build of pressure exerted in ventricles causes slight back flow but blood seeps behind the valve flaps slamming them shut with pressure
31
How is the muscle in the ventricles organised to facilitate pumping of blood?
Organised into figure of 8 bands
32
What is the difference between the right and left side of the heart?
Left side has thicker myocardium | Right side has pacemaker cells
33
Describe isovolumetric contraction
When ventricles contract but there are no values open
34
What is isovolumetric relaxation?
When ventricles relax before atrioventricular valves open
35
When do the pulmonary/aortic valves open and close?
Open - when ventricular pressure exceeds diastolic pressure in pulmonary/aortic arteries - systole Close - when arterial pressure is greater than ventricular pressure, slight back flow - end of systole
36
When do the tricuspid/mitral valves open and close
Open - atrial pressure greater than ventricular pressure - early diastole Close - when ventricular pressure exceeds atrial pressure, slight back flow - ventricular systole
37
What are the origins of the heart sounds?
First sound - AV valves closing - lup | Second sound - semi-lunar valves closing (ventricular-arterial valves) - dup
38
What are the left coronary arteries?
Left anterior decending Left marginal Circumflex
39
What are the right coronary arteries?
Right marginal | Right anterior ventricular
40
In an ECG what signal does a depolarisation towards an electrode cause?
Upward signal
41
In an ECG what signal does a depolarisation moving away from an electrode cause?
Downward signal
42
In an ECG what signal does a repolarisation moving away from an electrode cause?
Upward signal
43
In an ECG what signal does a repolarisation moving towards an electrode cause?
Downward signal
44
What does the amplitude of an ECG signal depend on?
How much muscle is depolarising | How directly towards the electrode the excitation moves
45
When reading an ECG what do you look at?
Rate, rhythm, axis, P-wave, P-R segment, QRS complex, Q-T interval, T wave
46
What is the P-wave of an ECG?
Atrial depolarisation
47
What is the Q peak in an ECG?
Excitation spreads down halfway down septum and across axis of heart
48
What is the R peak of ECG?
Depolarisation spreads through ventricular muscle
49
What is the S peak of the ECG?
Depolarisation spreads upwards through ventricles
50
What is the T wave of an ECG?
Repolarisation on epicardium surface of ventricles
51
What are amplifiers in terms of an ECG?
One positive and one negative electrode - negative electrode takes signal and inverts it, adding it to positive input
52
What are the ECG changes of atrium fibrillation?
No P waves | Irregularly spaced QRS complex
53
What are the ECG changes consistent with first, second and third degree heart blocks?
First degree - prolonged P-R interval Second degree - erratic P-R interval Third degree - no relationship between P wave and QRS complex
54
What is the cause of axial deviation and what are the consistent ECG changes?
Caused by changes in amount of muscle | Moves normal rhythm out of lead II - alters axis
55
What are the changes consistent with bundle branch block?
Lengthens and changes shape of QRS complex Rabbit ears Damage to conducting pathways
56
What are the ECG changes consistent with myocardial infarction?
ST elevation Inverted T waves Pathological Q waves - caused by scar tissue
57
In which vessels is blood flow fastest?
Where total cross sectional area is least, e.g. aorta | Slowest in capillary beds
57
What are the layers of an artery?
``` Tunica intima Internal elastic lamina Tunica media External elastic lamina Tunica externa ```
58
What are the layers of a vein?
Tunica intima Tunica media Tunica externa
59
What are the layers of the pericardium?
Fibrous layer | Serous layer - divided into parietal and visceral layers
62
What is the sensory nerve supply to the pericardium?
Phrenic nerve (C3-C5)
63
What is valve stenosis?
Narrowing of the valve
64
What is valve incompetence and what does it result in?
Valve not closing properly causing regurgitation
65
What occurs during an ventricular action potential?
Opening of voltage gated Na channels - Na influx Transient outflow of K+ Plateaux caused by opening of VOCC (L-type) - Ca influx Ca channels inactive, voltage gated K+ open - K efflux
66
What occurs during an SA node action potential?
Gradual influx of Na through HCN channels (cAMP-dependent) - Funny current (If) Opening of t-type voltage operated Ca channels - become inactive Opening of voltage operated K channels cause depolarisation
67
Describe the mechanism by which the tone of blood vessels controlled?
Ca binds to calmodulin which binds to myosin light chain kinase (MLCK) which phosphorylates myosin head through conversion of ATP to ADP
68
How does sympathetic activity change the SA node action potential?
Increase cAMP causes increased gradient of If due to more channels open and more Na influx
69
Which nerve provides parasympathetic innervation of the SA node?
Vagus nerve
70
Where do sympathetic pre-ganglionic nerves synapse?
Paravertebral chain
71
What are the two exceptions to the usual ANS innervation?
Sweat glands - sympathetic innervation but release ACh to muscarinic receptors Chromaffin cells in adrenal medulla - specialised postganglionic sympathetic neurones that release adrenaline into the bloodstream
72
Describe the mechanism of parasympathetic innervation of the SA node
M2 receptors - inhibit adenylyl cyclase - decreased cAMP - decreased opening of HCN channels, not main effect Beta-gamma subunit increases open probability of K channels so causes hyperpolarisation so takes longer to reach threshold
73
Describe the mechanism of sympathetically led positive inotropy
Noradrenaline - B1 receptors - + adenylyl cyclase - increased cAMP - increased PKA PKA phosphorylates L-type VOCC channels to increase open probability - increased Ca entry Increased Ca induced Ca release from SR (ryanodine receptors) Increased force of contraction
74
Describe the sympathetic drive of vasculature
Increased sympathetic drive - vasconstriction Normal - vasomotor tone Decreased sympathetic drive - vasodilation
75
Which receptors are involved in sympathetic innervation of vasculature?
Alpha 1 adrenoceptors
76
Describe the effect of metabolites on vasculature
Produced by active tissue (e.g. adenosine, K, H) | Strong vasodilatory effect
77
What controls sympathetic and parasympathetic drive of the heart?
Baroreceptors - sensitive to stretch therefore detect arterial pressure Located in carotid sinus and aortic arch
78
Flow is determined by resistance but what is resistance determined by?
Nature of fluid and vessel
79
What is flow?
Volume of fluid passing a given point per unit of time
80
What is velocity?
Rate of movement of fluid particles along tube
81
At a given flow, velocity is inversely proportional to what?
Cross sectional area
82
Describe in laminar flow
Concentric rings of gradient of velocity (from middle to edge), highest in centre
83
What causes turbulent flow?
Increased mean velocity or narrowed Increases flow resistance Generates sound
84
What is viscocity of blood?
The extent to which adjacent layers resist sliding over one another due to laminar flow
85
What does Poiseulles law state?
Decreasing the radius by 1/2 will increase vessel resistance by 16 times F proprotional to r4
86
What is special about the distensible tubes?
As vessel stretches, resistance falls | But as pressure drops, walls will eventually collapse - flow ceases before pressure falls to zero
87
What is the pressure and resistance of arteries?
Low resistance High pressure - due to high resistance of arterioles Distensible walls make flow less pusitile
88
What is TPR?
Total peripheral resistance - sum of all resistance from all vessels
89
What are the factors affecting systolic pressure?
How heart the heart pumps Total peripheral resistance Stretchiness of arteries
90
What are the factors affecting diastolic pressure?
Systolic pressure | TPR
91
What is TPR proportional too?
Inversely proportional to body's need for blood
92
What does Starling's Law of the Heart state?
The more the muscle is stretched the more is will contract (the bigger the stroke volume) Therefore increased venous pressure will equal increased stroke volume
93
What occurs during ventricular filling?
Ventricle will fill until intra-ventricular pressure = venous pressure *Ventricular compliance curve (venous pressure vs volume)
94
What does the Starling Curve show?
Stroke volume vs venous pressure (slope = contractility - ability of muscle to generate force for any given fibre length, caused by increased Ca) Curve tapers off at high venous pressure because heart stretch is limited by pericardial sac and it will impinge on coronary arteries
95
What determines the force of contraction?
End diastolic volume (starling's law) | Contractility (increase sympathetic activity)

ESA 2 - RJS (6 decks)

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