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SGUL - Physiology 1 > Introduction to the Cardiovascular System > Flashcards

Introduction to the Cardiovascular System Flashcards

1
Q

Why do we need the cardiovascular system?

A
  • Delivery and transport of oxygen and nutrients to cells and tissues e.g glucose
  • Removal of waste products from cells and tissues e.g urea, CO2
  • Thermoregulation - control heat distribution by vasoconstriction
  • Work alongside several organ systems
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2
Q

Give examples of organ systems that the CVS operates alongside

A
  • ENDOCRINE - transport of hormones towards target cells
  • IMMUNE - transport of inflammatory modulators to site of infection
  • LYMPHATIC - transport nutrients and white blood cells
  • REPRODUCTIVE - transport of oxygen and nutrients to foetus
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3
Q

What is passive diffusion and how is time needed for diffusion related to distance?

A
  • Random, undirected thermal motion of molecules
    time ∝ distance squared
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4
Q

Give examples of when passive diffusion is useful in organisms.

A
  • Movement of neurotransmitters across synapse
  • Diffusion of substance out of capillaries and into surrounding tissue

Low distance covered by molecule - low time taken and therefore motion is very quick

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5
Q

Why is passive diffusion not useful over larger distances?

A
  • As distance increases, the time taken for diffusion increases
  • Motion is very slow - not good for transport of essential nutrients (for these transport facilitated by systems such as CVS)
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6
Q

Describe the differences in pressure within the heart.

A
  • Energy used for ejection of blood under pressure
  • High pressure at LHS - blood leaving the heart through aorta/greater pressure for ejection from aorta into systemic circulation - around 100 mmHg. Pressure when blood arrives back at RHS is around 5 mmHg - pressure gradient drives transport of blood
  • Low pressure at RHS - blood being moved to the lungs - close to the heart/low pressures are more favourable for gas exchange (around 18-25 mmHg).
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7
Q

Describe pulmonary circulation.

A
  • Blood travels back to the heart through the venae cavae and is pumped into the right atrium followed by the right ventricle.
  • It travels up the pulmonary arteries to the lungs. Here gas exchange occurs and the blood becomes oxygenated. Oxygenated blood then travels, from the lungs, down the pulmonary vein into the heart via the left atrium.
  • Oxygen moves down a concentration gradient from the alveoli to the blood within the vessels (DISTANCE is short so time taken to diffuse is low - diffusion occurs passively)
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8
Q

Describe systemic circulation

A
  • Atria contract forcing oxygenated blood into the left ventricle. This also contracts, allowing blood to be ejected into systemic circulation via the aorta.
  • Aorta pumps oxygenated blood to the capillary beds in all tissues.
  • Gas exchange can occur due to concentration gradients and short diffusion distances (allows passive diffusion since exchange can occur rapidly). Blood becomes deoxygenated.
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9
Q

Describe the simultaneous relaxation and contraction of the chambers of the heart.

A
  • When both atria contract simultaneously, blood enters the relaxed ventricles
  • When both atria relax, the ventricles will contract simultaneously to eject blood from the heart
  • Relaxation and contraction is simultaneous and coordinated
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10
Q

How does venous structure differ from arterial structure?

A
  • Less muscle
  • Fewer elastic fibres
  • Fewer innervating sympathetic nerves
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11
Q

Outline a purpose of the endothelium.

A
  • Releases nitric oxide which acts as a relaxing factor and mediates vasodilation
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12
Q

Name the three layers found in all blood vessels

A

Tunica intima
Tunica media
Tunica adventitia

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13
Q

Outline the general structure of the tunica media

A

Contains circularly-orientated vascular smooth muscle
- Middle layer

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14
Q

What is the significance of the smooth muscle in the tunica media being orientated circularly?

A
  • Upon contraction, can reduce the size of the lumen (reverse for relaxation)
  • Allows extent of resistance to blood flow to be influenced
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15
Q

Outline the general structure of the tunica adventitia

A
  • Contains nerve fibres and smaller blood vessels that supply the smooth muscle
  • Outermost layer of the blood vessel
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16
Q

Outline what occurs upon sympathetic innervation of the tunica adventitia

A
  • Releases noradrenaline
  • Diffuses passively towards the α1-adrenoreceptors and activates them
  • Upon stimulation, vasoconstriction occurs
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17
Q

Outline the general structure of the tunica intima

A
  • Innermost layer of blood vessel
  • Consists of an endothelium which lines the inside of the vessel - underlined by a sub endothelial layer containing connective tissue
  • Elastic fibres orientated longitudinally under this layer
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18
Q

Briefly describe where and when the velocity of the blood changes during circulation

A

HEART AND ARTERIES - Velocity is high
ARTERIOLES - Velocity reduces
CAPILLARIES (DOWNSTREAM OF ARTERIOLES) - Further reduction in velocity
VENULES AND VEINS LEADING TO HEART - Gradual increase in velocity

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19
Q

What is blood velocity equal to?

A

Blood flow/total cross sectional area of vessels

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20
Q

Why is there a reduction in velocity at the capillaries?

A

Allows more time for exchange of gases and nutrients

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21
Q

Why is blood velocity at the aorta high?

A
  • Only one aorta through which cardiac output passes
  • This aorta has a relatively low cross sectional area ∴ velocity is high
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22
Q

As the blood spreads out into other arteries from the aorta, there is a reduction in velocity. Suggest why.

A
  • Greater total cross sectional area (lots of arteries will have a greater collective area than a single aorta)
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23
Q

Why is there a further reduction in blood velocity through the arterioles and capillaries?

A
  • Individually, each arteriole and capillary has a low cross sectional area.Collectively, total cross sectional area is high ∴ blood velocity is low
  • Cardiac output is transferred into the high number of arterioles and capillaries. The arterioles can also influence resistance to blood flow.
24
Q

Why is blood velocity in the venous system high?

A
  • Blood funnelled back into the venous system which has fewer vessels compared to capillaries
  • Lower total cross sectional area - blood returns to heart in a reasonable timeframe
25
Q

Where is most of the blood volume distributed?

A

VEINS

26
Q

How can blood volume be redistributed during exercise?

A
  • Veins contract and blood is transferred to the arteries to provide greater oxygen carrying capacity - needed for respiration
27
Q

Outline the path of blood flow after the blood is ejected into systemic circulation by the aorta

A

ARTERIES
ARTERIOLES
CAPILLARIES
VENULES
VEINS
VENAE CAVAE

28
Q

Describe the pressure profile at the arteries

A
  • Pressure at aorta usually begins with fluctuations between 120 mmHg (systolic pressure) and 80 mmHg (diastolic pressure)
  • These systolic and diastolic pressure differences decrease over time due to stretch and recoil action of the elastic arteries
  • Decrease in pressure ∴ reduced pressure differences
29
Q

Describe the pressure profile of the arterioles when approaching the capillaries

A
  • Pressure decreases - arterioles act as primary resistance vessels
  • Regulate resistance to flow under sympathetic and hormonal control ∴ total peripheral resistance is influenced ∴ blood pressure is influenced
  • Contract or relax to divert blood flow to specific organs and tissues depending on requirements and needs of organism
30
Q

Describe the pressure profile at the capillaries

A
  • Very low pressure - cannot control pressure
  • Walls of capillary are low ∴ short diffusion distance for gas and nutrient exchange
  • Pressure lower in venules and veins
31
Q

What does it mean for an organ to be under perfused?

A
  • High oxygen consumption and requirements at rest but not receiving proportionately high blood flow
    EXAMPLES - myocardium and brain
32
Q

What is the clinical significance of ensuring that cardiac output and blood flow to under perfused areas is controlled?

A
  • Brain and myocardium are already relatively under perfused compared to other organs
  • May be more vulnerable when moderate decreases in perfusion occur e.g in angina, myocardial infarction or stroke
33
Q

What are the four main groups of blood vessels?

A

LARGE ARTERIES
RESISTANCE ARTERIOLES
CAPILLARIES
VEINS AND VENULES

34
Q

Outline the function of large arteries.

A
  • Elastic vessels so stretch and recoil under pressure
  • Intermittent ejection pressure converted to constant pressure ∴ continuous blood flow
35
Q

Outline the function of arterioles

A
  • Resistance vessels
  • Small diameter - provide resistance to blood flow
  • Regulate local blood flow into organs and control arterial blood pressure(by determining TPR)
36
Q

Outline the function of capillaries

A
  • Exchange vessels
  • Involved in gas exchange, nutrient delivery to cells
  • Involved in motion of water in and out of interstitial fluid
37
Q

Outline the function of venules and veins

A
  • Capacitance vessels
  • Provide a mass reservoir of blood
  • When blood required at heart, they can contract and increase the volume of blood arriving at the heart
38
Q

How is blood flow related to blood vessel resistance?

A

INVERSE PROPORTION (as one increases, the other decreases)

39
Q

How is blood flow related to pressure across the blood vessel?

A

PROPORTIONAL (as one increases, the other also increases)

40
Q

If a vessel is constricted, how is blood flow influenced?

A
  • Increased resistance to blood flow
    ∴ Blood flow is reduced
41
Q

If a vessel is constricted at a certain point, describe what occurs upstream of the point of constriction?

A
  • Increased pressure
  • Reduced blood flow
42
Q

If a vessel is constricted at a certain point, describe what occurs downstream of the point of constriction?

A

Reduced pressure

43
Q

Suggest a possible cause for chronic hypertension and how this might cause blood pressure to rise

A

Blood vessels may constrict
- Greater resistance to blood flow ∴ reduced blood flow to end organs. May cause organ damage of the kidneys, liver and brain

44
Q

Describe a potential mechanism of action for antihypertensives

A
  • Cause dilation of vessels
  • Reduced resistance to blood flow and increased blood flow
  • Causes reduction in blood pressure
45
Q

Why is it essential for blood pressure to not drop to 0?

A
  • Blood pressure is needed to maintain blood flow at all times - linked with proper distribution of blood e.g poor perfusion of kidney can cause renal failure
  • 0 BP means that blood flow to essential organs would stop and start i.e occur discontinuously
46
Q

Why does the right ventricle have thinner walls than the left ventricle?

A
  • Less force needed to eject blood for pulmonary circulation ∴ high pressures and forces are not necessary
  • Lungs close to the heart - high pressures not needed for transport of blood
  • Low pressures provide better arrangements for gas exchange
47
Q

Define cardiac output

A

Volume of blood pumped by the heart in a given time
= heart rate x stroke volume

48
Q

Define heart rate

A

Number of heartbeats in a given time (usually per minute)

49
Q

Define stroke volume

A

Volume of blood ejected from the heart with each heartbeat

50
Q

Outline the three ways in which cardiac output is controlled

A
  • Starling’s Law
  • Autonomic nervous system
  • Chemical and hormonal factors
51
Q

Describe Starling’s Law

A
  • As volume of blood entering heart increases, the ventricular walls will contract and stretch
  • Walls will naturally contract harder causing greater ejection of blood to tissues where needed e.g the brain and skeletal muscle (STROKE VOLUME INCREASES)
52
Q

Outline the role of the autonomic nervous system in the control of cardiac output

A
  • Parasympathetic nervous system reduces heart rate ∴ reduced force of contraction ∴ reduced cardiac output
  • Sympathetic nervous system does the opposite
53
Q

Give an example of a hormone that can control cardiac output

A

ADRENALINE
- binds to β1-adrenoreceptors
- cause increase in heart rate ∴ cause force of contraction to increase ∴ increased cardiac output

54
Q

What is systole?

A

CONTRACTION
e.g in ejection of blood from the heart

55
Q

What is diastole?

A

RELAXATION
- ensures proper refilling so there is a sufficient volume of blood for ejection

56
Q

As people age, heart tissue stiffens and therefore does not relax as much. Suggest the possible consequences of this.

A
  • Reduced filling of the ventricles
  • Reduced volume of blood ejected upon ventricular contraction
  • Reduced cardiac output
57
Q

Describe the generalised process of blood ejection from the heart.

A
  • Blood arrives back at the heart at the right atria
  • Blood is forced into the right ventricle and pumped out through the pulmonary artery to the lungs and becomes oxygenated
  • Upon returning to the heart, blood moves from the left atrium to the left ventricle - ejected into systemic circulation by the aorta.

SGUL - Physiology 1 (68 decks)

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