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Introduction to physiology with pharmacology > Cardiovascular system > Flashcards

Cardiovascular system Flashcards

1
Q

Why do we have a circulatory system?

A

Only unicellular organisms can meet their metabolic needs by simple diffusion and convection
Evolutionary consequence of increasing in size and complexity
Maintenance of steep concentration gradients to deliver nutrients and remove waste

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2
Q

What are the primary functions of the circulatory system?

A

Distribution of gases and other molecules for nutrition, growth and repair

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3
Q

What are secondary functions of the circulatory system?

A

Fast chemical signalling of hormones
Dissipation of heat
Mediates inflammatory and host defence responses to invading microbes

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4
Q

How is the heart a dual pump?

A

Pumps blood in two circuits:

The left heart pumps to the systemic circulation and the right right heart pumps to the pulmonary circulation

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5
Q

What are the functions of the arteries, veins and microcirculation?

A

Arteries- the distribution system
Veins- collection system (resevoir)
Microcirculation- diffusion and filtration systems

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6
Q

What are the 4 building blocks of blood vessels?

A

Endothelial cells
Elastic fibres
Collagen fibres
Smooth muscle cells

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7
Q

What are the 3 layers of blood vessel walls?

A

Tunica interna
Tunica media
Tunica externa

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8
Q

Elastic arteries

A

Large arteries
High compliance- walls stretch easily without tearing in response to pressure increases
Enables vessels to cope with peak ejection pressures
Recoil of elastic fibres forces blood to move through even when the ventricles are relaxed

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9
Q

Muscular arteries

A

Medium sized arteries
Smooth muscle cells are arranged circumferentially
Capable of greater vasoconstriction and vasodilation to adjust rate of blood flow
Vascular tone- state of partial contraction maintains vessel pressure and efficient flow

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10
Q

Arterioles

A

Smooth muscle to regulate rate of blood flow into capillary networks- regulated microcirculation
Terminal regions of arterioles are known as metarterioles
Precapillary sphincters monitor blood flow into capillaries

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11
Q

Venules

A

Postcapillary venules are porous as they act as exchange sites for nutrients and waste
Muscular venules have a thin smooth muscle layer, less muscular than arterioles
Thin walls allow expansion which makes them excellent reservoirs for blood

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12
Q

Veins

A

Less muscular and elastic but distensible enough to adapt to variations in volume and pressure of blood
Like venules veins can ‘store’ blood

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13
Q

Large veins

A

More muscular than venules and small veins
Possess valves to prevent backflow
Defective leaky valves allow backflow and can lead to varicose

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14
Q

Other than being a principle exchange site, what other additional needs do capillaries serve?

A

Glomerular filtrate
Skin temperature regulation
Hormone delivery
Platelet delivery

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15
Q

What are the three kinds of capillaries in order from least to most leaky?

A

Continous
Fenestrated
Discontinuous/sinusoidal

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16
Q

What is the function of the lymphatic system?

A

Drains excess interstitial fluid and maintains circulating volume of blood
Transport of dietary lipids
Lymph nodes/organs important for immunology

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17
Q

What is blood made up of?

A

Plasma- ECF that is rich in protein
Erythrocytes
Leukocytes
Platelets

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18
Q

What are the principle proteins of blood plasma?

A

Albumin
Fibrinogen
Globulin
Other coagulation factors

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19
Q

What are the 3 major functions of erythrocytes?

A

Carrying oxygen from the lungs to the systemic circuit
Carrying carbon dioxide from tissues to the lungs
Buffering of acids and bases

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20
Q

What is unique about the shape of erythrocytes? How is this maintained?

A

Non-nucleated bioconcave discs to maximise SA:V

Cytoskeleton anchored to the membrane by glycophorin and band 3 Cl-/HCO3 exchanger

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21
Q

What are the 3 types of granular white blood cells (granulocytes) and what are their specific functions?

A

Neutrophils- phagocytose bacteria
Eosinophils- combat paracites and viruses
Basophils- release IL-4, histamine, heparin and peroxidase

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22
Q

What are the 3 types of non-granular white blood cells and what are their specific functions?

A

Lymphocytes- mature into T cells and B cells (plasma cells)

Monocytes- macrophages and dendritic cells

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23
Q

Where do platelets come from?

A

Bud off from megakaryocytes in the bone marrow

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24
Q

What structures are found in platelets?

A

Mitochondria, lysosomes, peroxizomes, alpha granules and dense core granules

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25
What is haematocrit? What relationship does it have with blood flow?
A test that determines the proportion of red blood cells in your blood Blood flow decreases with increasing haematocrit
26
What is viscosity in terms of blood flow?
Viscosity measures resistance to sliding of shearing fluid layers
27
What is the viscosity of blood dependent on?
``` Haematocrit Fibrinogen plasma concentration Vessel radius Linear velocity Temperature ```
28
What is haemostasis? How is it usually maintained?
Prevention of haemorrhaging Vasoconstriction- thromboxane A, serotonin, thrombin, endothelin-1 Increased tissue pressure which decreases transmural pressure Platelet plugs which are small breaches in vascular endothelium
29
How is blood cotting usually prevented?
Homeostatic mechanisms prevent haemostasis | Endothelial cells maintain normal blood fluidity through paracrine fators and anticoagulant factors
30
What is a thrombus?
An intravascular clot
31
What are the two pathways for blood clotting?
Intrinsic- surface contact activation on membrane of activated platelets Extrinsic- membrane bound tissue factor activation, activated when blood contacts material from damaged cell membranes
32
How can a thrombus form in pathological situations?
CV system- balance between pathological states of inadequate and overactive clotting DVT risk factors- venous stasis, vascular injury and hypercoagubility Arterial thrombosis can occur following erosion or rupture atherosclerotic plaque
33
What functions do the two atria of the heart perform?
Right- receives deoxygenated systemic venous return | Left- receives oxygenated blood from pulmonary circulation
34
What functions do the two ventricles of the heart perform?
Right- pushes blood to pulmonary circulation for oxygenation | Left- pumps oxygenated blood under high pressure to the head and body
35
How is back flow prevented?
Atrioventricular valves are connected to the cardiac wall by chordae tendinae and papillary muscles Semilunar valves have small fibrous nodules which come together to fill the triangular opening
36
What are the three layers of the heart wall from the outside inwards?
Epicardium Myocardium Endocardium
37
Where are the conducting cells of the heart found?
SAN Atrial internodal tracts AVN Bundle of His, purkinje system
38
What is the function of T tubules in myocyte contraction?
They enable current to be relayed to cell core to release calcium
39
What role does the sino-atrial node play in the cardiac cycle?
Cells of the SAN spontaneously depolarise to fire action potentials at a regular intrinsic rate of 60-100 times per minute
40
Depolarisation sequence after SAN AP firing
Cardiac cells electrically coupled through gap junctions conduct cell to cell through right and left atrial muscle- causes atrial systole 0.1 sec later signal arrives at atrioventricular node Signal spread is prevented by fibrous atrioventricular ring Resultant route is from AVN to the His-purkinje fibre system within ventricular muscl- causing ventricular systole
41
Atrial systole
Depolarisation of the atria following stimulation from the SAN Contraction of atrium increases atrial pressure As ventricles are relaxed and tricuspid valves open the ventricles further fill with blood from atria
42
Isovolumetric ventricular contraction
Following electrical activation by purkinje fibres, ventricles contract and ventricular pressure increases When ventricular pressure exceeds atrial pressure tricuspid valves close- first heart sound Pressure increases but volume remains the same
43
Rapid ventricular ejection
Pressure continues to rise until it exceeds aortic pressure Semilunar valves open, rapid ejection of blood driven by pressure gradient between ventricle and artery Most of stroke volume is ejected in this phase Ventricular volume falls dramatically and arterial pressure rises
44
Reduced ventricular ejection
Ventricles begin to repolarise and pressure falls as they are no longer contracting Semilunar valves are still open so ejection continues at a reduced rate and ventricular volume falls Arterial volume also falls as the blood moves into the 'arterial tree' Arterial pressure continues to increase as blood returns to the heart
45
Isovolumetric ventricular relaxation
Begins after ventricles have been fully repolarised Ventricles are relaxed and pressure decreases When below arterial pressure the semilunar valves close- second heart sound All valves are closed and ventricular volumes constant
46
Rapid ventricular filling
Ventricular pressure falls below arterial pressure so tricuspid valves open Ventricles begin to fill from atria so volume increases rapidly but pressure remains low
47
Reduced ventricular filling
Longest phase of the cardiac cycle and is includes the last portion of ventricular filling
48
What is an electrocardiogram?
Depolarisation and repoalrisation events of the cardiac cycle detected by electrodes on the body's surface The display of electrical activity is used to identify pathology of aberrant traces
49
P wave
Depolarisation of the atria | Duration of the P wave = atrial conduction time
50
PR interval
AV node conduction as it relfects initial depolarisation of the atria to that of the ventricles
51
QRS complex
Depolarisation of the ventricles | Masks the repolarisation of the atria
52
T wave
Repolarisation of the ventricles
53
Where is the highest resistance to blood flow found? When is this reduced?
Arterioles- have extensive tonically active smooth muscles so they are always contracted In response to sympathetic nerves, circulating catecholamines and other vasoactive substances
54
How do alpha adrenergic receptors respond when activated in arterioles?
Cause contraction and constriction of smooth muscle | Decreases diameter of blood vessels, increases resistance to blood flow
55
How do beta adrenergic receptors respond when activated in arterioles?
The opposite of alpha receptors- dilate and relax blood vessels These are less common
56
What is the relationship between resistance, vessel length and blood viscosity?
Resistance to flow is directly proportional to vessel length and blood viscosity (haematocrit) but inversely proportional to the fourth power of the radius
57
What is total peripheral resistance?
Resistance of entire systemic vasculature
58
What are the factors involved in resistance to blood flow?
Blood vessel diameter Vessel length Series or parallel arrangement Blood viscosity
59
What is blood flow determined by?
The pressure difference between the vessel inlet and outlet and the resistance of the vessel to blood flow
60
Why does pressure decrease as blood flows through the circulatory system?
As energy consumed overcomes frictional resistance
61
Pressure in the aorta
High cardiac output and low compliance
62
Pressure in the arteries
Remains high due to high elastic recoil
63
Pressure in arterioles
Dramatic fall due to high resistance to flow
64
Pressure in capillaries
Frictional resistance to flow and filtration
65
Pressure in veins and venules
High capacitance and low pressure
66
What is diastolic pressure?
Lowest arterial pressure during ventricular relaxation
67
What is systolic pressure?
Highest arterial pressure after blood is ejected from the ventricles during systole
68
How do you calculate pulse pressure?
Systolic pressure - diastolic pressure
69
How do you calculate mean arterial pressure?
Diastolic pressure + 1/3 pulse pressure
70
How does blood pressure change throughout the day?
Normally higher during the day and lower at night during sleep Regulated to meet needs of body and activity levels
71
What are baroreceptors?
Detect blood pressure | Carotid and aortic sinuses within arteries
72
What parts of the CNS are involved in the regulation of blood pressure? What do they do?
Solitary nucleus- receives information and detects changes in output of sympathetic and parasympathetic NS via the cardiovascular centres Brainstem cardiovascular centres in reticular formations of the medulla and lower pons
73
Parasympathetic control of blood pressure
Outflow via the vagus nerve to the SAN decreases heart rate and blood pressure
74
How does sympathetic control of blood pressure change the different parts of the circulatory system?
SAN increases heart rate Cardiac muscle increases contractility and stroke volume Arterioles vasoconstrict and increase TPR Veins vasoconstrict and decrease unstressed volume
75
What happens when arterial pressure is decreased?
Decrease in renal perfusion pressure is detected by kidney afferent arteriole mechanoreceptors Prorenin is converted to renin Angiotensinogen is converted to angiontensin I, then angiotensin II
76
How does angiotensin II increase blood pressure long term?
Acts on the adrenal cortex to synthesise and secrete aldosterone Increases Na+ reabsorption Stimulated Na+/H+ exchange in kidney Acts on hypothalamus to increase thirst and ADH secretion Vasoconstriction of arterioles to increase TPR
77
What are other regulatory mechanisms for blood pressure?
ADH Chemoreceptors for oxygen in carotid and aortic sinus bodies Atrial natriuretic peptide (ANP)
78
What are the effects of chronic hypertension?
Carotid sinus baroreceptors that carry info to the brainstem are densensitised and reset so hypertension is maintained instead of corrected
79
Symptoms of hypertension
Don't experience night time dip in BP Increased of morbidity and mortality- serious and life threatening conditions more likely Extra strain on organs and blood vessels
80
Hypertension treatments
Angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers Diuretics Beta blockers, alpha blockers, alpha agonists Calcium channel blockers Renin antagonists

Introduction to physiology with pharmacology (10 decks)

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