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Human Physiology > Cardiovascular System > Flashcards

Cardiovascular System Flashcards

1
Q

Name the 2 circuits of the cardiovascular system

A

Pulmonary Circuit

Systemic Circuit

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2
Q

Name the 3 components of the cardiovascular system

A

Blood

Blood Vessels

Heart

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3
Q

What is the role of the cardiovascular system?

A

Carrying mineral - O2 and CO2, Nutrients and Hormones

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4
Q

Briefly explain how the cardiovascular system works

A

Electrical - Action potential to cardiac muscle which causes them to contract

Pressure change causes blood flow (pump)

Valves prevent blood backflow

Material exchange

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5
Q

Explain the structure of the heart

A

A small muscular organ

Located between the lungs in the thoracic cavity

Within pericardium - pericardium sac containing fluid

Coronary arteries - branching off the base of the aorta

4 chambers - right atrium and ventricles, left atrium and ventricles

Valves - Atrioventricular valve and semilunar valve

Septum and Apex

Blood vessels connected to the heart - by convection, oxygenated vessels in red and deoxygenated vessels in blue

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6
Q

What are the 2 AV valves called and where are they located?

A

Right AV - tricuspid valve

Left AV - bicuspid valve

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7
Q

What are the 2 Semilunar valves called and where are they located?

A

Right - Pulmonary Semilunar Valve

Left - Aortic Semilunar Valve

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8
Q

Explain the action of AV valves

A

Papillary muscle (contracted)

Cusps down, valve open

Cusps up, valve closed

Papillary muscle (relaxed)

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9
Q

Explain the action of semilunar valves

A

Cusps up, valves open

Cusps down, valve closed

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10
Q

Explain the structure of the heart and where it transports blood to or where blood comes from

A

Superior vena cava - from the upper body

Pulmonary Veins - from right lungs

Inferior vena cava - from the lower body

Aorta - to systemic organs

Pulmonary trunk

Descending aorta - to lower body

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11
Q

Expian the term myocardium

A

The whole cardiac muscle mass

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12
Q

Explain how cardiac action potentials are generated

A

Action potentials initiated within the heart - not from a nerve

Autorhythmicity - triggers its contraction on a periodic basis

Autorhythmic cells - specialized muscle cells that spontaneously generate action potentials 2 types: pacemaker cells and conducting fibers - known as the conduction system

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13
Q

Name the 5 components of the conduction system of the heart

A

SA node

AV node

Right and left bundle branches

Internodal pathway

AV bundle (bundle of HIS)

Purkinje fibers

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14
Q

Explain how action potentials are spread

A

An action potential is initiated in the SA node

Action potentials are conducted from the SA node to the atrial muscle

Action potentials spread through the atria to the Av node where conduction slows

Action potentials travel rapidly through the conduction system to the apex of the heart

Action potentials spread upwards through the ventricular muscle

Eventually, the entire heart returns to the resting state, remaining there until another action potential is generated in the SA node

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15
Q

Name and explain the phases in cardiac action potential in the ventricular muscle cells

A

Phase 0 - Depolarization

Phase 1 - Small repolarization

Phase 2 - Plateau

Phase 3 - Repolarization

Phase 4 - Resting potential

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16
Q

Explain the role of ECG’s in measuring electrical activity

A

A non-invasive means for monitoring the electrical activity of the heart

Using electrodes placed on the skin - synchronized activity conducted by body fluids

To detect problems that exist in the electrical activity of the heart e.g. myocardial infarction, but not mechanical problems e.g. malfunction of a valve

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17
Q

Explain the waves in ECGs

A

P wave - an upwards deflection; atrial depolarization

QRS complex - a series of sharp upwards and downwards deflections; ventricular depolarization

T wave - an upwards deflection; ventricular repolarization

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18
Q

Explain ECG intervals and segments between the waves

A

P-Q (or P-R) interval: An estimate of the time of conduction through the AV node

Q-T interval: Ventricular contraction (ventricular systole)

T-Q segment: Ventricular relaxation (ventricular diastole)

R-R interval: Time between heartbeats (HR)

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19
Q

What are the names of ECGs you get

A

Normal Sinus Rhythm

Arrhythmia

Tachycardia

Bradycardia

Ventricular Fibrillation

Atrial Fibrillation

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20
Q

How are ECG diagnostics made?

A

In practice, a number of connections are made to the chest to give a 12-lead ECG

This gives a clinician a complete overview of the electrical activity of the heart

This can make a diagnosis of heart rhythm disorders more accurate

Interpretation of these is highly specialized

21
Q

Explain what the cardiac cycle is

A

Involves a coupling between electrical (action potential) and mechanical (contractile) events

It begins with atrial depolarization

The 2 atria contract followed by the 2 ventricles

The contraction creates changes in pressure which enables blood to move from one chamber to another and out in the corresponding blood vessel

22
Q

What do SP and DP stand for?

How do we calculate pulse pressure and mean arterial pressure?

A

SP - Systolic Pressure

DP - DIstolic Pressure

Pulse pressure (PP) = SP - DP

Mean Arterial Pressure (MAP) = DP + 1/3 PP

23
Q

In ventricular volume explain what EDV, ESV, and SV are

A

EDV = end-diastolic volume = volume of blood in the ventricle at the end of diastole = when the heart is relaxed

ESV = end-systolic volume = volume of blood in the ventricle at the end of systole when the heart is contracted

SV = stroke volume = blood ejected from the heart each cycle. How much blood the heart pumps out with each pump

SV = EDV - ESV

24
Q

Explain what ejection fraction is and how it is calculated

A

Fraction of end-diastolic volume ejected during a heartbeat = stroke volume / end-diastolic volume

Tyoical value of ejection fraction = 70 ML / 130 ML = 0.54 ML

25
Q

How is the typical value of stroke volume calculated?

A

EDV - ESV = 130 ML - 60 ML = 70 ML

26
Q

What does ejection fraction tell us about blood pumping?

A

How efficient the heart is at pumping blood

27
Q

Explain what cardiac output is and how to calculate it

A

the rate at which a ventricle pumps blood; usually expressed as L/min

Heart rate: the number of contractions (heartbeats) per minute (normally 72/min)

Stroke volume: the volume of blood that is pumped from each ventricle with every beat ( approximately 70 ml)

Cardiac output = heart rate x stroke volume

CO = HR X SV

28
Q

What determines stroke volume?

A

The size of the left ventricle and the degree of myocardial fiber shortening

29
Q

What 2 factors determine the extent of myocardial shortening and explain what they are

A

Preload - volume which enters the ventricles

Afterload - resistance that the left ventricle must overcome to circulate blood

30
Q

Explain what load is

A

Load is the force acting on, or generated by the heart muscle. In the heart, we usually talk about preload and afterload

Preload is the force acting on the muscle before the start of contraction, i.e. the force stretching the muscle before contraction, and thus determines the passive tension of the muscle, as well as the initial length which again is related to the tension development

But the preload is also the part of the total load the muscle must overcome in order to shorten

31
Q

Explain what the Total Load is

A

Afterload is the force added to the preload that offers resistance to the muscle shortening

The total load is preload + afterload. This is the force the muscles must overcome (e.g. the tension the muscle must develop) in order to shorten. contractility may be seen as the ability to overcome load

32
Q

Explain what Cardiac output: Preload

A

This is the degree of stretching of myocardial fibers during ventricular diastole and is proportional to the EDV

Preload is significant because it determines the ability of the muscle fibers to shorten- ie developed tension

Thus the higher the preload the huger the tension developed and the greater the stroke volume ie more in = more out

33
Q

Explain what EDV and ESV are

A

EDV - the amount of blood in ventricles at the end of ventricular diastole

ESV - amount of blood in the ventricles at the end of the ventricular systole

34
Q

Explain Starling’s law of the heart

A

The stroke volume of the heart increases in response to an increase in the volume of blood filling the heart (the end-diastolic volume) when all other factors remain constant

35
Q

Explain what cardiac output: afterload is

A

This is the amount of tension developed by the ventricles during contraction to open the semilunar valves

The greater the afterload the shorter the duration of ventricular ejection and the larger the end-systolic volume ie stroke volume decreases with increased afterload

AFterload is increased by factors that increase peripheral resistance

High afterload may lead to myocardial damage and heart failure

36
Q

Explain what series flow is

A

Pulmonary and systemic circuits are in series with each other (must pass through the 2 circuits in sequence)

37
Q

Explain what parallel flow is

A

Systemic organs are in parallel with one another

Coronary arteries: blood supply to heart muscle

The liver and intestine are in a series, called ‘portal circulation’

Advantage: each organ receives fully oxygenated blood; blood flow is regulated independently

38
Q

Explain the structure of Arterioles

A

Smooth muscle - resistance regualted

Neutral control

Can respond to local conditions - active hyperemia - higher blood flow due to changes in O2, CO2, K+, and H+

39
Q

Explain the structure of capillaries

A

Smallest and thinnest

A single layer of endothelial cells and basement membrane

The primary site for material exchange

Continuous capillaries - smaller size and lipid permeable substances; not protein

Fenetrated capillaries - protein and large molecules ( kidneys, liver, intestines, and bone marrow)

40
Q

Explain the terms blood flow, blood pressure, and resistance

A

Blood flow – volume of blood flowing through a vessel, an organ, or the entire circulation in a given period (ml/min)

Blood pressure – the force per unit area exerted on a vessel wall by the contained blood, is expressed in mmHg

Resistance – a measure of the degree to which the tube hinders or resists the flow of liquid through it (radius & length of blood vessel; viscosity of blood)

41
Q

Explain the structure of venules

A

Capillaries join up from venules

Smaller in size than arterioles about 20um diameter

Walls thinner; little smooth muscle

Some materials exchange between blood and interstitial fluid (tissue fluid)

42
Q

Explain the structure of veins

A

Venules join up from veins

Same size as arteries, but bugger internal diameter of about 5mm, and wall thickness is only 0.5 um

Contains smooth muscle and elastic fibers

Valves present in peripheral veins - outside the thoracic cavity; not in central veins (inside the thoracic cavity) - related to ‘repiratory pump’

Volume reservoir - high compliance

43
Q

how does blood return to the heart?

A

Veins have valves

Pressure gradient (still exists byt small and against gravity)

Skeletal muscle pump - exercise helps

Respiratory pump - vigorous respiration helps

44
Q

How does a respiratory pump work?

A

During inspiration, the diaphragm pulls down and the rib cage expands –pressure in the thoracic cavity  & abdominal pressure 

Creates a pressure gradient that promotes blood flow from the abdominal veins to the central veins

During expiration, the pressure gradient is reversed, but backward flow of blood is prevented by valves located in the abdominal veins

Blood flow towards the heart

45
Q

Explain the components of the sympathetic system and the effect it has on the heart

A

SA node, conducting tissue, and myocardium are innervated by sympathetic nerves

Effects are mediated mostly via the actions of noradrenaline

Increased force of contraction and increased heart rate

46
Q

Explain the components of the parasympathetic nervous system and the effect it has on the heart

A

SA node and Av node are innervated by parasympathetic nerves

Parasympathetic effects are mediated via the actions of acetylcholine

heart rate decreases

47
Q

Explain how blood pressure is regulated

A

Determinants of mean arterial pressure: heart rate, stroke volume, and total peripheral resistance

Regulation of mean arterial pressure - neutral control, hormonal control

Control by low-pressure baroreceptors (volume receptors)

48
Q

Explain what total peripheral resistance is and how it is calculated

A

Combined resistance of all blood vessels within the systematic circuit

TPR depends on the resistance of all vessels

flow through the network varies with resistance

Vasoconstriction increases resistance and decreases flow

Vasodilation decreases resistance and increases flow

49
Q

Explain what baroreceptors are

A

Sensory receptor neuron

Located in aortic arch and carotid sinuses

Respond to changes in blood pressure (sensitive to distending pressure of the arterial wall) by modified frequency of action potentials

Human Physiology (9 decks)

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