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Introduction to Physiology and Parmacology > The Circulatory System > Flashcards

The Circulatory System Flashcards

1
Q

Why do we have a circulatory system ?

A

A consequence of increase in animals size and complexity.

Larger SA:volume ratio

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2
Q

Whta is the primary function of the circulatory system ?

A

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

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3
Q

What re the secondary functions of the circulatory system?

A

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

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4
Q

What are the three functional parts of the circulatory system ?

A

Pump (heart)
Fluid (blood)
Set of containers (blood vessels)

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5
Q

What does the left side of the heart do ?

A

Heart os a dual pump
Left heart - Systemic circulation
Parallel pathways from left to right
Usually flows through a single (extensive) capillary bed
Can have two capillary beds in series e.g. kidneys
Can have capillary beds in parallel and series e.g. spleen, intestines and liver

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6
Q

What does the right side of the heart do ?

A

Right heart - Pulmonary circulation

Single pathway from right to left side of heart

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7
Q

What do Arteries, Veins and Microcirculation do ?

A

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

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8
Q

What are the 4 building blocks in a vascular wall ?

A

Endothelial cells
Elastic fibres
Collagen fibres
Smooth-muscle cells

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9
Q

What are the 3 layers of blood vessel walls ?

A

Innermost

intima (Tunica Interna)
media (Tunica Media)
adventitia (Tunica Externa)

Outermost

Capillaries - only intimal layer resting on a basement membrane

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10
Q

WHAT ARE THE FEATURES OF ELASTIC ARTERIES - LARGE ARTERIES ?

A

High compliance - walls stretch easily without tearing in response to pressure increase
Enables vessels (e.g. aorta) to cope with peak ejection pressures
Recoil of elastic fibres forces blood to move even when the ventricles are relaxed

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11
Q

What are the features of Muscular arteries - medium size ?

A

Smooth muscle cells are arranged circumferentially
Capable of greater vasoconstriction and vasodilation to adjust the rate of blood flow
Vascular tone – state of partial contraction maintains vessel pressure and efficient flow.

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12
Q

What re the features of arterioles ?

A

Arterioles have smooth muscle enabling regulation of blood flow into capillary networks regulated microcirculation. Site of high resistance to blood flow.

Walls have extensive tonically active smooth muscle (always contracted)

Terminal regions of arterioles are known as metarterioles

Precapillary sphincters monitor blood flow into the capillary

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13
Q

What are the features of Venules ?

A

Postcapillary venules are porous - act as exchange sites for nutrients and waste
Muscular venules have a thin smooth muscle cell layer (less muscular than arterioles)
Thin walls allow expansion - excellent reservoirs for blood

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14
Q

What are the features of 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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15
Q

What are the features of large veins?

A

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

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16
Q

What do capillaries exchange?

A

Gases
Water
Nutrients
Wste products

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17
Q

What other alternative functions do capillaries conduct ?

A

Glomerular filtrate
Skin temperature regulation
Hormone delivery
Platelet delivery

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18
Q

What is the function of capillaries ?

A

Small vessels composed only of endothelial cells and basement membrane
Exchange of substances between blood and interstitial fluid
Three groups based on their degree of ‘leakiness’
(Continuous, Fenestrated, Sinosoidal/ Discontinuous)

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19
Q

What is fluid transfer across capillary walls driven by ?

A

Sum of hydrostatic and osmotic pressure

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20
Q

What happens to capillary hydrostatic pressure along capillary length?

A

It declines

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21
Q

What does the lymphatic system do ?

A

Drains excess interstitial fluid with specialised valves and lymphatic capillaries, returns excessive fluid and protein filtrate to CVS

Maintains circulatory volume of blood

Returns lymph to CVS via subclavian veins

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22
Q

What happens when you block lymph capillaries?

A

Leads to Oedema

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23
Q

What are the other functions of the lymphatic system ?

A

Transports of dietary lipids

Lymph nodes (immunology)

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24
Q

What re the 4 chambers of the heart and what do they do?

A

Right atrium receives deoxygenated systemic venous return
Right ventricle pushes blood to pulmonary circulation for oxygenation

Left atrium receives oxygenated blood through pulmonary circulation
Left ventricle pumps oxygenated blood under high pressure to head and body

Atrium - acts as a reservoir for returning blood

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25
Q

What is the Heart?

A

Vital organ of cardiac muscle surrounded by a protectivefluid-filledsac called thepericardium

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26
Q

What is the Heart?

A

Vital organ of cardiac muscle surrounded by a protectivefluid-filledsac called thepericardium

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27
Q

What do Atrioventricular valves do?

A

Atrioventricular valves (mitral and tricuspid) connected to the cardiac wall by chordae tendinae and papillary muscles.

Connected by very inelesatic cords of fibrous connective tissue. Heartstrings. Attached underneath to the heart wall. Stops valves moving backwards, keeps integrity.

Prevents backflow

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28
Q

What do Semilunar valves do ?

A

(aortic and pulmonary) have small fibrous nodules which come closely together to fill the triangular opening.

Controls the unidirectional flow of blood, prevents back flow.

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29
Q

Describe the 3 layers of the heart wall

A

Epicardium – fat is part of this. In disease states it can increase. Comprised of loose connective tissues, elastic fibres. Helps produce the pericardial fluid. Helps in lubrication of heart. Visceral layer of the serous pericardium.

Myocardium - composed of involuntary striated muscle making up the main tissues of the heart wall. Cardiac muscle cells incased in collagen fibres and other components of the ECM.

Endocardium – internal, covers heart valves, valves are continuous with it. Smooth muscle and elastic fibres.

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30
Q

What are the two types of cells found in the heart?

Describe them

A

Contractile cells (majority of atrial and ventricular tissues), action potentials lead to contraction and generation of force/pressure.

Conducting cells (SAN, atrial internodal tracts, AVN, bundle of His, Purkinje system), rapidly spread action potentials

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31
Q

What does excitation of myocytes trigger ?

A

Triggers an excitation-contraction coupling. This triggers an AP

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32
Q

Why must propagation of APs be carefully timed?

A

To synchronise ventricular contraction and optimise vol of blood ejected.

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33
Q

What does a think myocardium contain ?

A

Contains muscle fibre cells extensively branched and connected to one another by intercalated discs. Allows fast AP propagation from cell to cell.

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34
Q

What is the Myocardial cell structure?

A

Intercalated discs - part of sarcolemma (excitable plasma membrane. Contain GAP junctions and desmosomes and Z lines.

Cardiac cells that are electrically coupled through GAP junctions, forming channels allowing depolarising current to flow from one cell to the next in a wave-like pattern (syncytium)

Desmosomes - anchor fibres together

35
Q

What do GAP junctions allow in the Myocardial cell structure ?

A

GAP junctions allow proporgation of AP.

They form the channels between adjacent cells and allows depolarising event to travel from one cell to its neighbour.

This electrical coupling allows that coordinated contraction

36
Q

What are T-tubules and what do they enable?

A

They are deep invaginations of the sarcolemma

Enables current to be relayed to cell core releasing Calcium

Simultaneously, larger instantaneous force is produced by Sarcoplasmic Reticulum to release calcium near all sarcomeres.

37
Q

What are the thick and thin filaments of sarcomeres ?

A

Thick filaments composed of myosin, whose globular heads have actin-binding sites and ATPase activity

Thin filaments:
Actin – globular protein
Tropomyosin – runs
along the groove
Troponin – globular 3 
subunits. C subunit binds 
with calcium
38
Q

What happens to the sarcomere after depolarisation ?

A
  1. Cross-bride=ges form between myosin and actin and break, thin and thick filaments move past each other.
  2. This uses ATP and results in tension
  3. Distance between Z line shortens
  4. The cumulative effect of all the small contractions makes the organ contract.
39
Q

List the steps of the Cardiac depolarisation sequence in detail

A
  1. Cells of Sino atrial (SA) node (first pacemaker) spontaneously depolarise to fire action potentials at regular intrinsic rate 60-100 times per minute
  2. Cardiac cells electrically coupled through gap junctions conduct cell to cell through right and left atrial muscle (atrial systole)
  3. 0.1 second later signal arrives at Atrioventricular (AV) node (second pacemaker)
  4. Impulse spread prevented by fibrous atrioventricular ring
  5. Resultant route for impulse from AV node to His-Purkinje fibre system within muscle of ventricles (leading to ventricular systole)
40
Q

At what points of the Cardiac Cycle are certain valves opened and closed?

A

Mitral valve closes

Aortic valves open

Aortic valves close

Mitral Vavels open

41
Q

What is the first step of Cardiac depolarisation ?

A

Atrial systole - depolarisation of the atria (following stimulation from SAN) P wave on ECG

Contraction of atrium causes an increase in atrial pressure, Opening AV valves. Only a fraction of ventricular fill in, passive blood flow.

As ventricles are relaxed and mitral/tricuspid valves open the ventricles further fill with blood from atria

Closing AV valves marks first heart sound S1.

Electrical activation due to Purkinje Fibres

42
Q

What is the second step of Cardiac depolarisation?

A

Isovolumetric ventricular contraction

Following electrical activation via Purkinje fibres, ventricles contract (systole), pressure increases

When ventricular pressure exceeds atrial pressure, mitral and tricuspid valves close, producing the first heart sound (S1)

Pressure increases markedly but volume remains the same

Volume stays the same. S1 is the closing of AV valves.

43
Q

What is the third step of Cardiac depolarisation ?

A

Rapid ventricular ejection

Pressure continues to rise until it exceed aortic pressure

Semilunar valves open, rapid ejection of blood driven by pressure gradient between ventricle and artery

Most of stroke volume ejected in this phase

Ventricular volume falls dramatically and arterial pressure rises due to large volume received

Atrial filling begins and pressure slowly increases

44
Q

What is the 4th step of Cardiac depolarisation ?

A

Reduced ventricular ejection

Ventricles begin to repolarise and pressure falls as no longer contracting
As semilunar valves still open blood continues to be ejected but at reduced rate and ventricular volume falls
Arterial volume also falling as blood moves into ‘arterial tree’
Atrial pressure continues to increase as blood returns to the heart

45
Q

What is the 5th step of Cardiac Depolarisation ?

A

Isovolumetric ventricular relaxation

Begins after ventricles fully repolarised

Ventricles relaxed and pressure decreases

When below arterial pressure, semilunar valves close – second heart sound (S2)

All valves closed and ventricular volume constant

No change in volume. Diastole

Ventricular pressure when below arterial closes SL valves.

46
Q

What is the 7th step of Cardiac depolarisation ?

A

Longest phase of cardiac cycle and includes last portion of ventricular filling

47
Q

What is the 6th step of cardiac depolarisation ?

A

Ventricular pressure falls to below atrial pressure – mitral and tricuspid valves open
Ventricles begin to fill from atria, volume increases rapidly but pressure remains low (S3)

48
Q

Whta is an Electrocardiogram and how does it work ?

A

The depolarisation and repolarisation events of the cardiac cycle detected by electrodes on the body’s surface

This display of electrical activity (ECG) used clinically to identify pathology with aberrant trace

ECG records the summed electrical activity of the heart

Electrodes measure in planes around the heart

The direction of the electrical activity can cause a positive of negative deflection

49
Q

What is the order of the waves and intervals on an ECG ?

A 
P wave 
PR interval
Q
R
S
ST segment
T
50
Q

What happens during the P wave ?

A

P wave – depolarisation of atria
Duration of P wave = atrial conduction time
Repolarisation of atria masked by QRS wave

Duration of P is the atrial conduction time

51
Q

What is the PR interval of the ECG ?

A

PR interval – AV node conduction as it reflects initial depolarisation of atria to that of ventricles

52
Q

What is the QRS complex of an ECG ?

A

QRS complex – depolarisation of ventricles

Tissues depolarises and contract and then will repolaries before next contraction. Cannot see P repolarisation as it is masked by QRS wave

53
Q

What is the T wave ?

A

Repolarisation of Ventricles

54
Q

What do arterioles respond to when resistance changes ?

A

sympathetic nerves
circulating catecholeamines
other vasoactive substances

55
Q

What re the two receptors of Arterioles ?

A

Arterioles are innervated by sympathetic adrenergic fibres

α1- adrenergic receptors on arterioles of several vascular beds (e.g. skin and splanchnic vasculature)

Less common β2 adrenergic receptors in skeletal muscle arterioles dilate and relax

56
Q

What happens when activated arterioles cause contraction/constriction of vascular smooth muscle ?

A

Decreases diameter of arteriole

Increases resistance to blood flow

57
Q

What is the dilation/constriction of arterioles regulated by ?

A 
Regulated by sympathetic innervation of vascular smooth muscle and vasoactive metabolites produced in the tissue e.g.
Angiotensin
Bradykinin
Histamine
Nitric oxide
Vasoactive intestinal peptide (VIP)
58
Q

What are the 5 main features of Venules and veins ?

A

Walls contain much less elastic tissue than arteries

Large capacitance

Contain largest percentage of blood in CV system – ‘unstressed volume’

Smooth muscle in walls innervated by sympathetic nerve fibres

Increased activity via α1- adrenergic receptors – contraction to reduce capacitance - decrease in ‘unstressed volume’

58
Q

What are the 5 main features of Venules and veins ?

A

Walls contain much less elastic tissue than arteries

Large capacitance

Contain largest percentage of blood in CV system – ‘unstressed volume’

Smooth muscle in walls innervated by sympathetic nerve fibres

Increased activity via α1- adrenergic receptors – contraction to reduce capacitance - decrease in ‘unstressed volume’

59
Q

What happens in identical blood flow ?

A

In identical flow – inverse relationship between velocity and cross-sectional area

60
Q

What is Total Peripheral Resistance ?

A

Total peripheral resistance (TPR) – resistance of entire systemic vasculature

Resistance in a single organ can be calculated by substituting e.g. renal flow for flow

61
Q

What is Blood flow determined by ?

A

Pressure difference between vessel inlet and outlet

Resistance of vessel to blood flow

61
Q

What is Blood flow determined by ?

A

Pressure difference between vessel inlet and outlet

Resistance of vessel to blood flow

62
Q

List 4 factors of blood vessels involved in resistance to flow ?

A

Blood vessel diameter
Vessel length
Series/parallel arrangement
Blood viscosity

63
Q

What is resistance to flow directly proportional to and inversely proportional to ?

A

Vessel length and blood viscosity (haematocrit)

Inversely proportional to fourth power of the radius*

64
Q

Where is the largest decrease in pressure ?

A

Arterioles (largest resistance)

65
Q

Describe the different pressures in different blood vessel types

A

Aorta – high cardiac output and low compliance (highest of the arteries)
Arteries – remains high due to high elastic recoil
Arterioles – dramatic fall due to high resistance to flow R = 8ղl/πr4
Capillaries – frictional resistance to flow and filtration
Venules and veins – high capacitance and low pressure

66
Q

What do oscillations in arterial pressure reflect ?

A

Reflects pulsatile activity of the heart

67
Q

What is Diastolic and Systolic pressure ?

A

Diastolic pressure - lowest arterial pressure during ventricular relaxation

Systolic pressure – highest arterial pressure in arteries after blood ejected from ventricles during systole

68
Q

What is the Dicrotic notch ?

A

(Dicrotic notch (incisura) is the ‘blip’ produced when the aortic valve closes)

69
Q

What does Pulse pressure reflect ?

A

Reflects blood volume ejected from left ventricle (stroke volume)

70
Q

How does blood pressure change throughout the day?

A

Normally higher during the day and lower at night, during sleep

Regulated to meet needs of body and activity levels

71
Q

What organelles are involved in the rapid regulation of BP ?

A

Baroreceptors - Carotid and aortic sinuses within arteries

Nucleus tractus solitarius (solitary nucleus) receives information and directs changes in output of sympathetic and parasympathetic NS via the cardiovascular centres

Brainstem cardiovascular centres in reticular formations of the medulla and lower pons

72
Q

What are the 4 components used by Sympathetic control to elevate BP ?

A

SAN to increase heart rate

Cardiac muscle to increase contractility and stroke volume

Arterioles to produce vasoconstriction and increase TPR

Veins to produce vasoconstriction and decrease unstressed volume

73
Q

How does Parasympathetic outflow decrease BP ?

A

Parasympathetic outflow via vagus nerve on the SAN to decrease heart rate and reduce BP

73
Q

How does Parasympathetic outflow decrease BP ?

A

Parasympathetic outflow via vagus nerve on the SAN to decrease heart rate and reduce BP

74
Q

What do Chemoreceptors stimulate in terms of arterioles ?

A

Chemoreceptors for O2 in carotid and aortic sinus bodies – stimulates arteriole vasoconstriction
Chemoreceptors of CO2 in the brain - stimulates arteriole vasoconstriction

75
Q

What occurs during chronic hypertension ?

A

In chronic hypertension baroreceptors reset

Desensitises baroreceptors

75
Q

What occurs during chronic hypertension ?

A

In chronic hypertension baroreceptors reset

Desensitises baroreceptors

76
Q

What is Hypertension ?

A

Hypertension is a long term elevation of blood pressure leading to pathologies, drugs can act to block pathways.

Puts a large strain on blood vessels and other organs

77
Q

What diseases can Hypertension lead to ?

A 
heart disease
heart attacks
strokes
heart failure
aortic aneurysms 
peripheral arterial disease
kidney disease
vascular dementia
78
Q

What diseases can Hypertension lead to ?

A 
heart disease
heart attacks
strokes
heart failure
aortic aneurysms 
peripheral arterial disease
kidney disease
vascular dementia
79
Q

List Hypertension treatments ?

A 
Angiotensin-converting enzyme (ACE) inhibitors
Angiotensin II receptor blockers (ARBs)
Diuretics (Thiazide)
Beta-blockers.
Calcium channel blockers.
Alpha-blockers.
Alpha-agonists.
Renin inhibitors.
79
Q

List Hypertension treatments ?

A 
Angiotensin-converting enzyme (ACE) inhibitors
Angiotensin II receptor blockers (ARBs)
Diuretics (Thiazide)
Beta-blockers.
Calcium channel blockers.
Alpha-blockers.
Alpha-agonists.
Renin inhibitors.

Introduction to Physiology and Parmacology (7 decks)

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