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PHYL2066 Content > Module 3 - Cardiovascular System > Flashcards

Module 3 - Cardiovascular System Flashcards

1
Q

List 4 reasons why the cardiovascular system is important

A
  1. Transports oxygen and nutrients to the cells
  2. Removes waste products from the body
  3. Transports hormones around the body
  4. Helps maintain body temperature
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2
Q

How many circuits does the cardiovascular system have?

A
  1. Pulmonary Circuit

2. Systemic Circuit

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3
Q

Which system has the highest pressure?

A

= systemic; because it pumps blood to the whole body; whereas pulmonary pumps just to lungs

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4
Q

How many chambers does the heart have?

A

4 in total
2 x atria
2 x ventricles

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5
Q

Which chamber is the most muscular?

A

= left ventricle (ventricle pumping blood through systemic circuit)

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6
Q

How many valves does the heart have?

A

2 x atrioventricular valves (tricuspid and bicuspid)

2 x semilunar valves (pulmonary and aortic)

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7
Q

What is the role of valves?

A

= to prevent back flow of blood

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8
Q

Describe the 3 layer histology of the heart wall

A
  1. Epicardium
    - outer layer = visceral pericardium
    - simple squamous epithelium + loose connective tissue + adipose layer
  2. Myocardium
    - cardiac muscle layer
  3. Endocardium
    - simple squamous epithelium
    - smooth layer to minimise friction
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9
Q

Describe cardiac muscle cells

A
  • myocardium = the cardiac muscle
  • cardiac muscle cells:
  • branched cells
  • interconnected
  • joined at intercalated discs
  • striated
  • 99% contractile muscle cells
  • 1% auto rhythmic cells
  • non-contractile
  • generate APs
  • intercalated discs
    *junction between cardiac cells
    *desmosomes
    + mechanical anchor
  • gap junctions
    + tunnels connecting cells
    + allows the passage of ions; transmission of APs
    *cardiac cells contract simultaneously
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10
Q

Describe electrical activity of the heart

A
  • 1% of cardiac muscle cells are auto rhythmic
  • spontaneous depolarisation
  • pacemaker potential
  • increase in sodium ion and calcium ion influx, and decrease in potassium ion efflux
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11
Q

Describe the cardiac conduction system

A
  • controls the route and timing of cardiac APs
  • coordinated contraction of heart chambers
  • consists of auto rhythmic cells
  • sinoatrial node
  • atrioventricular node
  • Bundle of His
  • Bundle branches
  • Purkinje fibres
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12
Q

Describe how the spread of excitation through the heart must meet 3 criteria

A
  1. Each heart chamber must pump as a unit
  2. Atria should contract together; ventricles should contract together
  3. Atrial excitation and contraction must complete before ventricular contraction
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13
Q

Describe electrical conduction through the heart

A
  • APs start in the SA node
    *spread through atria
  • APs must travel through the AV node to reach ventricles
    *AV nodal delay (allows time for atria to contract and start to relax before the ventricles contract)
    (AV nodal delay occurs via the electrically non-conductive fibrous tissue; between atria and ventricle)
  • ventricular conduction
    *AV bundle; bundle branches
    *Purkinje fibres
  • non conductive tissue between the atria and ventricles prevents APs travelling directly from atria to ventricles
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14
Q

Describe the cardiac cycle

A
  • period between one heart beat and the next
  • periods of contraction and relaxation
  • systole = contraction
  • diastole = relaxation
    PROCESS:
    1. Atrial and ventricular diastole (atrioventricular valves open, semilunar closed) -> 0.4 seconds
    2. Atrial systole/ventricular diastole -> 0.1 seconds
    3. Ventricular systole/atrial diastole -> 0.3 seconds
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15
Q

Describe Heart Sounds

A
  • closing of valves (Lub dub [pause])
  • first sound (S1)
  • Closure of the AV valve
  • Beginning of Ventricular Systole
  • second sound (S2)
  • Closure of semilunar valves
  • ventricular diastole

-> Lub dub sound = when the valves hit each other
1st= AV -> into other components of the heart
2nd= SL -> bigger; out of the body

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16
Q

Describe pressure changes in fluid

A
  • fluid pressure= force exerted on a container by the fluid
  • units= mmHg
  • decreasing the size of a fluid-filled container will increase fluid pressure
  • Ventricular contraction
  • Constriction of Vessels
  • increasing the size of a fluid-filled container will decrease fluid pressure
  • Ventricular relaxation
  • Dilation of vessels
  • inverse relationship between pressure and size of container
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17
Q

Describe the cardiac cycle

A
  • > The flow of blood between chambers is determined by the pressure changes in the heart
    a) Ventricular and atrial diastole
  • blood entering atrium. Atrial pressure > ventricular pressure = AV valve open (passive flow of blood into the ventricles)
    b) Atrial contraction
  • atrial pressure increases and ventricular volume increases until ADV
    c) Isovolumetric Ventricular Contraction
  • ventricular pressure > atrial pressure = AV closes (1st heart sound)
  • ventricular pressure < aortic pressure = SL closed
    d) Ventricular Ejection
  • ventricular pressure > aortic pressure = SL open
  • ventricular volume decreases until ESV
    e) Isovolumetric Ventricular Relaxation
  • ventricular pressure < aortic pressure = SL close (2nd heart sound)
  • ventricular pressure > atrial pressure = AV closes
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18
Q

Describe Cardiac Output

A
  • volume of blood pumped by each ventricle per minute

- indicates blood flow through peripheral tissues

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19
Q

Give the equation for Cardiac Output

A

Cardiac Output (CO) = Heart Rate (beats/min) x Stroke Volume (ml/beat)

Heart Rate = how fast the heart is beating
Stroke Volume = volume of blood pumped out of ventricle during each contraction

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20
Q

Describe Resting Heart Rate

A
  • SA Node sets the pace because it depolarises the quickest (the pacemaker of the heart)
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21
Q

Describe how the ANS can change the heart rate

A
  • the heart is innervated by sympathetic and parasympathetic neurons
  • ANS can change the rate of depolarisation in the SA node (heart beat changes)
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22
Q

Describe influence of the parasympathetic nervous system

A
  • reduces the rate of APs in SA node
  • decreases heart rate
  • reduces rate of AP production
  • causes hyperpolarisation, so increases time to reach threshold
  • slower depolarisation
  • PNS is dominant in resting individual
  • heart rate is normally slower than SA node speed
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23
Q

Describe the influence of the sympathetic nervous system

A
  • increases the rate of APs in SA node

- increases heart rate (causes rapid depolarisation)

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24
Q

Describe Stroke Volume

A
  • volume of blood pumped out of the ventricle during contraction
  • is the difference between:
  • End Diastolic Volume (EDV) = volume of blood in the ventricle during relaxation
  • End Systolic Volume (ESV) = volume of blood in the ventricle after systole
  • amount of blood left in ventricle before and after contraction
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25
Q

Give the equation for Stroke Volume

A

Stroke Volume = EDV - ESV

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26
Q

Describe Venous Return

A
  • volume of blood returning back to the heart each minute
  • increasing venous return will:
  • increase EDV
  • cause heart muscle to stretch
  • as cardiac muscle stretches, the next contraction will be stronger
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27
Q

Describe the Frank Starling Law of the Heart

A
  • the greater the EDV/venous return, the greater the force of contraction during systole (within limits)
  • if increase in EDV, stroke volume also increases. At rest, heart muscle is not at optimal length to produce contraction. When increase EDV, muscle and cell stretches, creating more optimal overlap between actin and myosin, therefore, creating a stronger contraction
28
Q

Describe the influence of Veins on venous return

A
  • complete the circuit from tissues to the heart
  • at any given moment, the majority of blood is travelling through veins (64%)
  • veins can act as a blood reservoir
  • stretchable (due to weak muscle)
  • little elastic recoil
  • veins are compliant (able to stretch and hold a greater volume)
29
Q

Describe pressure in the veins

A
  • blood flows from high pressure to low pressure
  • veins are a low pressure system (17 mmHg at beginning of venous system)
  • pressure in atrium (0mmHg)
  • pressure gradient is small, but diffident to return to the heart
30
Q

List 5 factors that affect venous return

A
  1. Cardiac Suction
  2. Skeletal Muscle Pump
  3. Venous Valves
  4. Respiratory Pump
  5. Sympathetic Nervous System
31
Q

Describe Cardiac Suction

A
  • heart acting as a suction pump
  • cardiac suction occurs in both systole and diastole
  • contraction (systole) of ventricles
  • AV valves drawn downward
  • increased volume in atria; decreased pressure in atria
  • sucks blood from veins into atria
  • relaxation (diastole) of ventricles:
  • increased volume of ventricles; decreased pressure in ventricles
  • sucks blood from veins and atria into ventricles
32
Q

Describe skeletal muscle pump

A
  • large veins lie between skeletal muscle/run through muscle
  • muscle action compresses the vein:
  • push blood through vein
  • similar to how lymph travels due to movement of skeletal muscle
  • this process only works due to veins having valves to prevent back-flow
  • inactivity -> can lead to swollen joint towards feet/ankles
33
Q

Describe venous valves

A
  • valves control the direction of blood flow

* prevents back-flow

34
Q

Describe the respiratory pump

A

INSPIRATION: Expansion of thoracic cavity and decreased pressure in thoracic cavity

  • right atria and venae cavea expand
  • increase pressure gradient between venous system and atria
  • increase venous return

EXPIRATION: Compression of thoracic cavity and increased pressure in thoracic cavity

  • right atria and venae cavea compressed
  • decrease pressure gradient between venous system and atria
  • decrease venous return
35
Q

Describe Sympathetic stimulation

A
  • causes vasoconstriction of veins (venoconstriction)
  • reduces storage space in veins
  • mobilises blood
  • increase venous return
  • increase EDV
  • increase stroke volume
  • increase cardiac output
36
Q

Describe the effect of gravity

A
  • lying down: gravity applied uniformly
  • standing: vessels in lower limbs experience more pressure; veins pumping blood ‘uphill’
  • compensation: skeletal muscle pump; sympathetic nervous system
37
Q

Describe Fainting

A
  1. Standing at attention
  2. Decrease venous return
  3. Decrease cardiac output
  4. Decrease blood to brain
  5. Fainting - loss of consciousness
  6. Fall over - VR and CO return to normal
38
Q

Describe how blood pressure is different in each vessel

A
  • blood pressure is the force exerted on the walls of the blood vessels
  • during systole (contraction) the pressure in the ventricles is high, during diastole (relaxation) the pressure in the ventricle is low (essentially zero)
  • the ventricle then pumps blood to arteries, there is the fluctuation of the systolic and diastolic blood pressure; however, the pressure in the arteries never gets to zero
  • pressure drops as we go from ventricles to venules and veins
39
Q

Describe Measuring Blood Pressure

A
  • can be measured indirectly using a sphygmomanometer
  • inflatable cuff with pressure gauge
  • cuff compresses the brachial artery
  • measures systolic and diastolic pressure
40
Q

Describe the 5 step process of the sphygmomanometer

A

When cuff pressure is greater than 120 mmHg and exceeds blood pressure throughout the cardiac cycle
No blood flows through the vessel
1. No sound is heard because no blood is flowing

When cuff pressure is between 120 and 80 mmHg
Blood flow through the vessel is turbulent whenever blood pressure exceeds cuff pressure
2. The first sound is heard at peak systolic pressure
3. Intermittent sounds are produced by turbulent spurts of flow as blood pressure cyclically exceeds cuff pressure

When cuff pressure is less than 80 mmHg and below blood pressure throughout the cardiac cycle
Blood flows through the vessel in smooth, laminar fashion
4. The last sound is heard at minimum diastolic pressure
5. No sound is heard thereafter because of uninterrupted, smooth laminar flow

41
Q

Describe other measures of pressure

A
  • Pulse pressure
  • difference between systolic and diastolic pressure
  • e.g. 120 - 80 = 40 mmHg
  • Mean arterial pressure
  • average blood pressure in the arteries
  • closer to diastole because heart spends longer in diastole
42
Q

Describe Mean Arterial Pressure

A

Mean Arterial Pressure = diastolic pressure + 1/3 pulse pressure

Mean Arterial Pressure is used by the body to regulate blood pressure, not systolic or diastolic pressure

43
Q

Describe Blood Flow

A
  • the rate at which blood flows through the circulatory system is dependent on:
  • the activity of the heart (cardiac output)
  • the resistance to blood flow (vessel diameter)
  • the heart has to generate enough pressure to overcome resistance to blood flow
44
Q

Describe blood pressure when exercising

A

When exercising:
Increase flow to skeletal muscle
Decrease blood flow to kidneys and GI tract

45
Q

Describe Flow, Pressure and Resistance

A
  • blood flow is directly proportional to the pressure gradient
  • increased pressure gradient = increase in flow
  • blood flow is inversely proportional to cardiovascular resistance
  • increase in resistance = decrease in flow

F=change in P/R

46
Q

Describe Flow and Resistance

A
  • friction between the blood and the vessel causes resistance
  • resistance to blood flow is controlled by:
  • blood viscosity (constant)
  • vessel length (constant)
  • vessel diameter (only factor we can regulate)
  • it is easier for blood to flow through a large vessel than a small one
  • cardiovascular resistance is controlled by vessel radius
  • double the radius, increased blood flow by 16 times
  • vessel diameter is a powerful way to control bloody flow
47
Q

Give the equation for Total Peripheral Resistance

A

Total Peripheral Resistance = R arteries + R arterioles + R capillaries + R venules + R veins

48
Q

Describe Flow and Pressure

A
  • pressure gradient = difference in pressure between beginning and end of a vessel
  • contraction of heart gives pressure to the blood
  • pressure in cardiovascular system decreases from arteries to veins
  • blood flows from high pressure to low pressure
  • blood flow is directly proportional to the pressure gradient
49
Q

Give the equation for Pressure Gradient

A

Pressure Gradient = mean arterial pressure (MAP) - central venous pressure (CVP)

50
Q

Describe Arteriolar Radius

A
  • total peripheral resistance is controlled by blood vessel radius
  • radius of the arterioles can be increased (dilated) or decreased (constricted)
  • arterioles are the major resistance vessels
51
Q

Describe how arteriolar radius can be controlled by extrinsic and local factors

A

Local = changes at the level of the muscle/vessel
- metabolic changes in oxygen and other metabolites; important in matching blood flow with metabolic needs

  • local metabolic changes in a tissue (e.g. skeletal muscle) control arteriolar diameter and allow blood flow to meet the needs of the tissue
  • for example; during exercise an increase in metabolism stimulates the dilation of local arterioles

Extrinsic = from nervous and endocrine systems
- sympathetic activity; exerts generalised vasoconstrictor effect

  • extrinsic factor help to regulate blood pressure
    *SNS=generalised vasoconstriction through alpha 1 receptors
    *Hormones:
    >antidiuretic hormone and angiotensin 11 (important for water balance) cause vasoconstriction
    >adrenal medulla: norepinephrine reinforces sympathetic nervous system response, epinephrine causes dilated through beta 2 receptors (heart and skeletal muscle)
52
Q

List the 6 step process of how local metabolic changes influence arteriole radius when exercising

A
  1. Exercise
  2. Increase in tissue metabolism
  3. Decrease in oxygen, increase in carbon dioxide and hydrogen ions
  4. Arterioles dilate
  5. Decreased resistance = increased blood flow
  6. Increase oxygen and nutrients supplied to metabolising tissue
53
Q

Describe Capillaries

A
  • site of exchange between blood and tissue
  • gases (oxygen and carbon dioxide)
  • nutrients
  • wastes
  • exchange occurs primarily by diffusion
  • capillaries are so small that red blood cells pass through in a single file
54
Q

Describe blood flow through capillaries

A
  • capillaries are arranged into capillary beds
  • blood supply to a capillary bed can be controlled by a precapillary sphincter
  • blood still flows through metarteriole
55
Q

Describe how precapillary sphincters and arterioles act together to regulate blood flow

A
  • on average, only 25% of the capillaries are open
  • opening is controlled by local metabolic changes
  • precapillary sphincters open when we needs them to

for example:
When exercising as more oxygen is needed in the muscle and carbon dioxide is needed to be expelled from the muscle at a faster pace; therefore to match this pace, more precapillary sphincters open

56
Q

Give 3 reasons why capillaries are good for diffusion

A
  1. Small diffusion distance
    * thin capillary walls
    * small capillary diameter
    * large network of capillaries
  2. Large surface area available for exchange
  3. Slow blood flow
57
Q

Describe bulk flow

A
  • continuous flow of fluid and solutes between capillaries and interstitial fluid
  • interstitial fluid = plasma minus plasma proteins
  • fluid mouvement is controlled by:
  • hydrostatic pressure
  • osmotic pressure
  • filtration= pushing fluid out of capillary
  • reabsorption= drawing fluid back into capillary
58
Q

Describe the 2 forces driving bulk flow

A
  1. Capillary hydrostatic pressure (CHP)
    - hydrostatic pressure of blood flowing into capillaries
    - pushes fluid out of capillaries
    - higher at arteriolar end than venular end
  2. Blood colloid osmotic pressure (BCOP)
    - plasma proteins too large to exit capillary
    - more solutes in the capillary than the interstitial fluid
    - osmosis draws the fluid back into the capillary
59
Q

Describe Net Filtration Pressure

A
  • NFP is the difference between the capillary hydrostatic pressure and blood colloid osmotic pressure
  • positive NFP favours filtration
  • negative NFP favours reabsorption
60
Q

Describe regulation of blood pressure

A

Neural Mechanisms = short term control of blood pressure

Endocrine Mechanisms = long tern control of blood pressure and volume

61
Q

Describe the cardiovascular control centre

A
  • located in the medulla oblongata
  • receives sensory information about blood pressure (baroreceptors)
  • regulates sympathetic and parasympathetic activity to heart and vessels
62
Q

Describe baroreceptors

A
  • baroreceptors: mechanoreceptors that respond to stretch
  • carotid sinuses: monitor blood flow to the brain
  • aortic arch: monitor blood flow to systematic circulation
63
Q

Describe the 8 step Baroreceptor Reflex when there is decreased blood pressure

A
  1. When blood pressure falls below normal
  2. Decrease in carotid sinus and aortic arch receptor potential
  3. Decrease in rate of firing in afferent nerves
  4. Cardiovascular centre
  5. Increase in sympathetic cardiac nerve activity, increase in sympathetic vasoconstrictor nerve activity and decrease in parasympathetic nerve activity
  6. Increase in heart rate, increase in stroke volume and arteriolar and venous vasoconstriction
  7. Increase in cardiac output and increase in total peripheral resistance
  8. Blood pressure increased towards normal
64
Q

Describe the 8 step Baroreceptor Reflex when there is increased blood pressure

A
  1. When blood pressure becomes elevated above normal
  2. Increase in carotid sinus and aortic arch receptor potential
  3. Increase in rate of firing in afferent nerves
  4. Cardiovascular centre
  5. Decrease in sympathetic cardiac nerve activity, decrease in sympathetic vasoconstrictor nerve activity and increase in parasympathetic nerve activity
  6. Decrease in heart rate, decrease in stroke volume and arteriolar and venous vasoconstriction
  7. Decrease in cardiac output and decrease in total peripheral resistance
  8. Blood pressure decreased towards normal
65
Q

Draw a diagram showing the process of a Haemorrhage: Short-term: Baroreceptor Reflex

A

see notebook for diagram

66
Q

Draw a diagram showing the process of a Haemorrhage: Long-term: Endocrine Response

A

see notebook for diagram

PHYL2066 Content (8 decks)

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