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MedSci142 > Lecture 12 and 13: Blood Pressure > Flashcards

Lecture 12 and 13: Blood Pressure Flashcards

1
Q

What are the numbers for the blood distribution in the Cardiovascular system?

A 
7% Heart
7% Systemic Capillaries
9% Pulmonary Vessels
13% Systemic Arteries and Arterioles
64% Systemic Veins and venules (blood reservoirs)
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2
Q

What can be the difference between Cardiac Output?

A

5L - 20L

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3
Q

When is maximum pressure derived?

A

During systole

120mmHg

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4
Q

Where is the largest percentage of blood volume and why?

A

Systemic Veins and Venules contain the largest percentage of blood volume

  • they function as Blood Reservoirs from which blood an be diverted quickly if the need arises
  • can achieve this diversion through Vasodilation and Vasoconstriction
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5
Q

What is blood pressure like in Arterioles?

A

there is the Greatest Drop of blood Pressure in the Arterioles
120-80mmHg
- arterioles are Only 1mm thick and contains Smooth muscle
-Major Resistance Vessel and this resistance of flow Dampens Pressure
-biggest pressure resistance- yet flow is the same
(small- only 1-2mm in diameter
don’t have much CT but LOTS of Sooth muscle
Flexible- change in diameter
under Tonic Vasoconstriction (“tone”) - has a degree of tension/tone
Buffer/Shock absorbers= pressure fallsto 30-40 mmHg (BIG FALL IN PRESSURE))

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6
Q

What is blood pressure like in Capillaries?

A

Pressure is the driving force of Filtration
Capillaries are the Site of Exchange and therefore has a Huge SA to Facilitate this
-Thin walled so Highly permeable and substance can leak out

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7
Q

When we talk about “ Blood Pressure” what are we talking about?

A

Pressure in the Arteries

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8
Q

When do you hear sound through a stethoscope?

A

Smooth running blood is silent (Laminar flow)

Blood makes sound when there is Turbulence, could be caused by Blockage, Atherosclerotic Plaque

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9
Q

What is the mean Arterial Blood Pressure?

A

1/3 between diastolic/systolic BPs = dBP +1/2 GBP-dBP

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10
Q

What is special about blood pressure?

A

Highly variable

constantly being adjusted

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11
Q

What is TPR?

A

The Total Peripheral Summation of all the resistances around the body
Resistance which is opposing blood flow
Veins, capillaries, arterioles, arteries
Which as a results gives rise to the value of Blood Pressure(which we measure)

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12
Q

How can you measure Blood Pressure?

A

CO x TPR

Therefore you can modify BP by changes CO, or could change TPR

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13
Q

What are some specific features of arteries?

A

made out of smooth muscle with lots of CT
Pulse, but less flexible due to CT, therefore cannot change diameter by much
Conjugate pipes
Pulsatile pressure with each heart beat

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14
Q

What are some special features of arterioles?

A

small- only 1-2mm in diameter
don’t have much CT but LOTS of Sooth muscle
Flexible- change in diameter
under Tonic Vasoconstriction (“tone”) - has a degree of tension/tone
Buffer/Shock absorbers= pressure fallsto 30-40 mmHg (BIG FALL IN PRESSURE)

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15
Q

Are pressure and volume the same ting?

A

No
We have Very low pressure in the veins
and High volume of blood in the veins

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16
Q

What is the fall form arteries to capillaries?

A

60 mmHg

Pulsatile –> continuous flow/hardly pulsatile/pretty small pressure/RBC line up to feed through different cappilaires

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17
Q

What percentage of the population suffer from hypertension?

A

11-14%

another 10% are undiagnosed

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18
Q

What is the average blood pressure?

A

sustained blood pressure over a period of time

if

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19
Q

What can sustainably high blood pressure lead to?

A

A following of other Cardiovascular events later in life, due to greater Preload
Compensation in the heart, in heart tissues, in the brain
Blood pressure does increase with age

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20
Q

What is the Net Filtration at the arteriole end of capillaries?

A

20L per day

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21
Q

What is the Net Reabsorption at the venous end of capillaries?

A

17L per day

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22
Q

How do you calculate Net Filtration Pressure (NFP)?

A

NFP = (BHP + IPOP) - (BCOP + IPHP)

= Pressure promoting filtration - pressure promoting reabsorption

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23
Q

What with the NFP at the Arterial end of capillaries?

A

(BHP + IPOP) - (BCOP + IPHP)
= (35 + 1) - (26 + 0)
=10 mmHg
= Net Filtration

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24
Q

What is the NFP at the Venous end of capillaries?

A

(BHP + IPOP) - (BCOP + IPHP)
= (16 + 1) - (26 + 0)
= -9 mmHg
= Net Reabsorption

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25
Q

What are the methods of capillary exchange?

A
  1. Diffusion
  2. Transcytosis
  3. Bulk Flow
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26
Q

What does the Diffusion method of capillary exchange involve?

A

Simple diffusion of 02, CO2, glucose, amino acids etc
Concentration and Electrochemical gradient
Down Conc. gradients b/w capillary and interstitial fluid and H2O soluble

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27
Q

What does the Transcytosis Method of capillary exchange?

A

Substances enclosed in pinocytosis vesicles and (large or lip insoluble) transported across endothelium via ex/endocytosis

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28
Q

What is the Bulk Flow method of Capillary exchange?

A

Filtration and reabsorption fo fluid and solutes
(NOT of proteins as they are too large)
Pressure Gradient

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29
Q

What is Bulk Flow?

A

the passive process in which Large numbers of ions and molecules move together in the same direction
they move at a greater rate than can be accounted for by diffusion alone
Occurs from high pressure –> Low pressure
Important for regulation of relative blood volume and interstitial volume

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30
Q

What is the Filtration component of Bulk Flow?

A

Filtration sit he pressure driven movement of fluid and solutes FROM blood capillaries –> INTO interstitial fluid

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31
Q

What is BHP?

A

Blood Hydrostatic Pressure
The pressure against BV walls
pressure generated by the pumping action of the heart
main driving force pushing fluid out of the capillary

32
Q

What is IFOP?

A

Interstitial Fluid Osmotic Pressure
proteins in Interstitial Fluid
Pressure which promotes filtration pulls fluid FROM capillaries and –> INTO Fluid
IFOP is only small as there is only a little protein in the interstitial fluid due to lymph

33
Q

What is the Reabsorption component of Bulk Flow?

A

Pressure driven movement of fluid FROLM Interstitial Fluid INTO –> the capillary

34
Q

What is the BCOP?

A

Blood Colloid Osmotic Pressure
Plasma proteins
Pressure generated by RBC, large blood plasma proteins which are too large to pass through fenestrations and gap between the endothelial cells
This si the force caused by colloidal suspension of these large proteins in plasma, the effect of BCOP is to “pull” fluid from interstitial spaces into capillaries
IFOP opposes BCOP as it “pulls” fluid from the capillaries into the interstitial fluid

35
Q

What is osmotic pressure?

A

the pressure developed by solutes dissolved in water and generated by all dissolved solutes

36
Q

What is oncotic pressure?

A

Oncotic pressure = BCOP

as it refers to the part of the osmotic pressure generate by larger colloidal solute components

37
Q

What is IFHP?

A

Interstitial Fluid Hydrostatic Pressure
Fluid in the interstitial spaces
Pressure promoting reabsoprtion - pushes fluid from interstitial fluid –> to cappilaries
(close to 0, difficult to measure)

38
Q

What does the Balance of pressure determine?

A

Whether fluid leaves or enters capillaries depends on the balance of pressures
This balance determines whether the volumes of blood and interstitial fluid remain steady or change
Overall the volume of fluid and solutes reabsorbed normally is almost as large as the volume filtered
This near equilibrium is Starlings Law of the Capillaries

39
Q

What is the NFP?

A

Net Filtration PRessure
Indicated the direction of Fluid movement
NFP = (BHP + IFOP) - (BCOP + IFHP)
= pressure that promotes filtration - pressure that promotes reabsorption

40
Q

What occurs are the Arterial end of the capillary?

A

FILTRATION
NFP is positive
Occurs when the pressures that push fluid out of the capillaries exceeds the pressures that pull fluid into capillaries
Fluid will love from capillaries –> into interstitial fluid

41
Q

What occurs at the Venous end of the capillary?

A

REABSORPTION
NFP is Negative
Occurs when the pressures that push fluid out of the interstitial spaces into capillaries exceed pressures, pulling fluid out of capillaries
Fluid will move from interstitial spaces –> into capillaries

42
Q

What is blood flow?

A

The volume of blood that flows through any tissue in a greater time period
total blood flow = CO

43
Q

What does the CO distributed to the body depend on?

A
  1. Pressure difference: driving blood flow high –>low. Larger gradient, greater blood flow
  2. Resistance: to blood flow in vessels
    Higher resistance –> smaller blood flow
    Organs are arranged in parallel, and this decreases TOTAL resistance
44
Q

What is Blood pressure?

A

contraction of the ventricles generates blood pressure (BP)
The hydrostatic pressure exerted by blood or walls of a blood vessels
BP=CO x TPR

45
Q

How is Blood Flow Stability regulated?

A

Stability of blood flow is regulated by CO and TPR and maintain homeostasis of BP - keep in a small range for exchange

46
Q

What if TPR?

A

Total Peripheral Resistance
The resistance from arterioles is a major determining factor (so has greatest effect on blood pressure)
Primarily smooth muscle and only little connective tissue - under degree of force/tension and it can adjust its radius –> vasoconstriction and vasodilation
Blood pressure never falls to 0 due to TPR and resistance in vasculature –> offered by systemic blood vessels
Resistance in veins and arteries is small, as they’re large vessels
However smaller vessels such as venules, capillaries and especially arterioles contribute most resistance

47
Q

What causes a change in resistance?

A

Smal changes in diameter of blood vessels causes a large change in resistance
Resistance is proportional to 1/r^4
inversely proportional relationship

48
Q

What are the factors affecting Vascular Resistance?

A

Total peripheral resistance = systemic vascular resistance
Factor 1: Radius or size of the Lumen changes according to need
Factor 2: Blood Viscosity
Factor 3: Total blood vessel length

49
Q

How does Radius/size of the lumen affect Vascular Resistance?

A

Factor 1: Radius or size of the Lumen changes according to need
small change in diameter causes a big change in resistance
a. Vasodilation: increasing size of blood vessel lumen, decreases blood pressure. decreases resistance
b. Vasoconstriction: decreasing size of blood vessel lumen, increases blood pressure, increases resistance

50
Q

How does Blood Viscosity affect Vascular Resistance?

A

Thickness of blood
Depends mostly on the radio of RBC : Plasma (fluid) volume and to a smaller extent on the concentration of proteins in the plasma
Directly proportional relationship: higher blood viscosity –> high blood pressure (increased resistance)

51
Q

How does the Total Blood vessel Length affect Vascular Resistance?

A

Resistance to blood flow is directly proportional to the length of the blood vessel
the longer the blood vessel –> the higher the resistance
Poiseuilles Equation describes how the flow is related to pressure, radius, length and viscosity
F proportional to (change P x r^4) / (n x L)
= governs flow through the true

52
Q

What is the key part of filtration?

A

That its key driving force is pressure

53
Q

What are colloids?

A

Things which cannot be filtered out
Big proteins etc.
Act as a drag

54
Q

How are organs arranged?

A

In parallel
Means that the profusion pressure for every organ is about the same
Results in even pressure across the different beds
Major advantage

55
Q

What are the main pre-cappilary resistance vessels?

A 
Arterioles
much smaller than arteries
a little CT
a lot of smooth muscle
small change in radius, leads to large change in resistance, alter the perfusion to a organ
56
Q

What happens if you regulate total arteriole pressure?

A

you regulate total arteriole pressure –> regulates TPR –> regulates blood pressure

57
Q

What happens to blood pressure as it goes through the system?

A

Blood pressure falls

100 mean

58
Q

How do you control blood pressure?

A

Vasoconstriction

vasodilation

59
Q

What are the factors which affect Vascular Tone?

A

sympathetic nervous activity
hormonal factors
metabolites
intrinsic factors

60
Q

What could be an example of regulation of blood pressure?

A

CO= 4L/minutes, 4x organis, therefore 1L/min each
1Lmin each at rest, during exercise CO increases, SV increases, supply increases
Causes vasodilation, supply to organ A increases
-redistributes blood flow to exercising muscle over specific organs
Kidney and gut –> vasoconstrictor 1Lmin –> 100mL/min take blood flow from these areas and redistribute elsewhere (e.g. only 20-25% blood flow going to kidney to very little volume
Based on NEED –> NEED can REGULATE BLOOD FLOW

61
Q

How does Sympathetic Nervous Activity affect Arteriolar Resistance/ Vascular Tone?

A

Co-ordinated by the brain
Sympathetic nerves come down and form varicosities (vasomotor nerves in arterioles)
EVERY SINGLE ARTERIOLE has sympathetic nerve innervation
Constant activity –> not flight/fight –> degree of tone
Increase in Sympathetic Nervous Activity = increase HR, increase CO, increase Contractility
-More epinephrine released from the adrenal medulla
-Vaso-constriction –> decrease in radius
-Resistance increases
increases blood flow to the heart and muscles during exercise, –> Less in reservoir, e.g. veins, i.e the periphery
(vasodilation when decreasing sympathetic nervous activity)

62
Q

How do Hormonal Factors affect Arteriolar Resistance/ Vascular Tone?

A

Circulating factor - control by brain and organs
There are many hormones circulating
Within blood supply the combination determines the effect
e.g. Angiotensin II
produced in the enzymatic process of the kidney(conversion from A1 –> AII
is a powerful vasoconstrictor, increases BP, increases resistance,
If patient has high blood pressure(hyper tension), drug therapy is used to decrease Angiotensin II in blood, via targeting decrease of the converting enzyme, vasodilation, lower BP

63
Q

How do Metabolites affect Arteriolar Resistance/ Vascular Tone?

A

O2, CO2, Na+, K+, Ca2+
important in regulating vasoconstricted states and tones
CO2 is a powerful vasodilator
O2 is a powerful vasoconstrictor

64
Q

How do intrinsic factors affect Arteriolar Resistance/ Vascular Tone?

A

A Local factor
Factors which relate to blood vessels themselves which is being perfused right then
pressure/during force changes
Causes Local response, wall stretches smooth muscle, and vascular decreases in O2, system responds with vasoconstriction auto regulation (e.g. warming –> vasodilation) (protective measure)
NO –> nitric oxide is released in endothelial cells and for a short half life –> causes vasodilation
If lots of pressure of turbulent flow into blood vessels, stress occurring on vessel, endothelial lining will cause release of NO, therefore vasodilation –> decrease in BP
(myogenic - stretched contracts forcefully)
Counteracts vasodilation
Used in hair growth –> stimulate follicles
Now Viagra

65
Q

How do you control Blood Pressure?

A

Several interconnect Negative Feedback mechanisms control blood pressure by adjusting - HR, SV, Systemic Vascular Resistance, Blood Volume
Allows it to have a rapid response
Body wants to achieve stable blood pressure
If not stable would affect blood hydrostatic pressure, and therefore would rapidly change exchange in capillary beds
-many control systems to manipulate CO and TPR and restore Homeostasis so that there is a Stable BP for exchange

66
Q

What is the Cardiovascular Centre?

A

Vasomotor Control centre, medullary

controls neutral, hormonal and local negative feed back systems regulating BP

67
Q

What are Baroceptors?

A

Pressure sensitive receptors in the Aortic Arch (2x carotid sinuses) and Carotid Arteries (internal and external)
Baroceptors in Carotis Sinus initiate Carotid Sinus Reflex –> helps regulate BP in brain
- BP stretches wall of carotid sinus –> stimulates baroreceptors
-Afferent Neurons –> medulla Response
Like a Thresholding system- Provide BP Every single Heart Beat
Fires most at beginning of cycle
Acts as a buffer/stabiliser of BP, meaning HR will be changing up and down constantly - BP is constantly being sensed and constantly being adjusted

68
Q

What happens when there is a decrease in blood pressure?

A

Can occur in 1x Heart Beat (Rapid Response)
1. in response to stimulus which DISRUPTS HOMEOSTASIS a. hot –> skin vasodilates b. alcohol= vasodilator c. moving from prone (horizontal column of fluid) to erect position (Vertical column of fluid) –> hydrostatic effect of gravity can Decrease BP and decrease blood flow to head and upper body
2. Decreases Blood pressure – a. Feeling of Dizziness. 100mmHg –> 90mmHg change (10-20mmHg)
3. Baroceptors sense fall in blood pressure - blood stretched less, they send nerve impulses out at a slower rate to the cardiovascular centre (decreasing firing)
4. CARDIOVASCULAR CENTRE INPUT
5. CARDIOVASCULAR CENTRE OUTPUT
6. Decreased Paraympathetic stimulation/vagal activity - motor axons of vagus nerve
7. Increased sympathetic Stimulation - results in 2x consequences
a. Cardiac accelerator nerve : can increase HR
b. Secretion of epinephrine and norepinephrine by the adrenal medulla (heart beats forcefully)
8. Increased CO –> increase SV and Increased HR
9. Increased TPR –> constriction of blood vessels, increases systemic vascular resistance
10. Blood pressure increases as homeostasis is re-established/stabilised/restored (to mean 100mmHg)
11. Overall: Blood pressure being buffered/stabilised by arteriole baroceptors –> means HR is constantly being moved up and down
Vasoconstriction: arterioles and veins in skin and abdominal organs –> periphery
Notes: input Cardiovascular Centre measures O2 level, CO2 level, Blood Volume etc. Many inputs so CO must integrate
Output time lag or response different. Vagal action fast –> 1x Heart Beat, Cardiac Sympathetic –> 5-6 Heart beats, Arterioles –> 1-2 sec

69
Q

What happens when there is an increase in blood pressure?

A
  1. When an increase in pressure is detected a. Baroceptosr stretched more
    b. send impulses at a faster rate to CV centre
  2. CV CENTRE INPUT
  3. CV CENTRE OUTPUT
  4. increases parasympathetic
  5. decreases sympathetic
  6. CO decreases , decrease HR, decreases SV
  7. TPR decreases a. CV centre decreases rate at which it sends sympathetic impulses along vasomotor neurons that normally cause vasoconstriction. b. the resulting vasodilation lowers systemic vascular resistance c. lowers systemic arterial blood pressure to a normal level
70
Q

What happens when there is a decrease in venous return?

A 
Respiratory Sinus Arrhythmia
a normal physiological response due to changes in venous return 
1. Very small decrease in BP
2. results in an increase in HR - caused by baroceptors who notices small decrease in BP
3. Expiration
4. increases Venous Return
5. Increases VP
6. Decrease in HR
71
Q

What happens where there is an increase in blood volume?

A

Blood pressure and blood volume are interlinked
wate retention in body: EDV decrease as less volume returning to heart = decreased SV
1. Drink 500 mL of water, increasing Blood volume, goes rapidly into cardiovascular system –> big change
2. Leads to increase in blood pressure - small change = about 5mmHg. bigger change in volume but not all goes out to arterial system –> veins have a greater increase - increase in venous pressure
Cardio pulmonary receptors sense change in pressure
2-3 mmHg –> 5-6 mmHg –> INPUT –> CNS-hypothalamus –> OUTPUT
Renal response: much closer acting response compared to cardiovascular
Kidney needs to get rid go extra fluid as it dilutes the osmolarity of plasma
- signal is sympathetic nerve activity and hormonal influences:
ADH produced by hypothalamus and secreted by posterior pituitary : increase BV, increase BP, less ADH released
Causes Vasodilation –> decreases blood pressure allowing excretion so decrease in BV

72
Q

What happens when there is a decrease in Blood volume?

A

Decrease in blood volume can be due to hyporolemic shock. Negative Feedback mechanism restores BP - prevents damage
Compensatory mechanism can maintain adequate blood flow and blood pressure despite blood loss of around 10% of total volume - acute haemorrhage e.g. pregnancy, trauma, aneurysm, excessive sweating, diarrhoea, vomiting, diabetes, Na+ deficiency
1. Secretion of ADH
a. decreased blood pressure
b. posterior pituitary release more ADH
c. ADH enhances water reabsorption - conserves remaining blood volume
d. causes vasoconstriction, increasing systemic vascular resistance
2. Activation of the sympathetic division of the ANS:
a. decreased BP, aortic and carotid baroreceptors initiate sympathetic response
b. vasoconstriction in arteriole and veins in skin, kidneys, abdominal viscera –> No vasoconstriction in brain and heart
c. increases systemic vascular resistance, constriction of veins = increase venous return
d. maintains BP –> also increases HR and Increases contractility, increases Norepinephrine by adrenal medulla, which intensifies vasoconstriction –> increase in BP

73
Q

Where do you always painting blood flow?

A

Heart, Coronary vessels, and to the brain

74
Q

Why system enable redistribution of blood?

A

Sympathetic nervous system

75
Q

Why is the cardiovascular system co-ordinated?

A

To allow supply of O2 to tissues that require it
redistribution is controlled by regulation of CO on one side, and by regulation of blood flow to different organs by nerves on the other side

MedSci142 (20 decks)

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