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BIOM20002 - HSF > Lecture 53 - Cardiovascular Function 1 > Flashcards

Lecture 53 - Cardiovascular Function 1 Flashcards

1
Q

How is the cardiovascular system controlled?

A

Rapid: Nervous system
Slow: Hormonal (kidneys)

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2
Q

Why have a cardiovascular system?

A
  1. Maintain steady flow to tissue beds
  2. Protect vital organs (brain, heart, kidney)
  3. Adjust for changes in posture and metabolic demand
  4. Responding to physiological conditions
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3
Q

How much blood does the brain receive?

A

13% of cardiac output

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4
Q

Describe Giraffe’s BP

A

The brain is very high above the heart

Has a very high BP to account for this

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5
Q

Voltage =

A

I x R

Current x Resistance

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6
Q

BP =

A

CO x TPR

Cardiac output x Total peripheral resistance

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7
Q

What are the determinants of Cardiac output?

A

Stroke volume

Force of contraction

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8
Q

Where does most of the resistance in circulation come from?

A

Arterioles

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9
Q

What does the Hagen-Poiseuille equation tell us?

A

Pressure difference between two ends of a tube is:

viscosity x length x Flow / radius

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10
Q

What is pressure proportional to?

A
  • Viscosity of liquid
  • Length of tube
  • Flow through the tube
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11
Q

What is pressure inversely proportional to?

A

Radius of the tube

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12
Q

A small decrease in radius …

A

leads to a large increase in pressure

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13
Q

Is the cross sectional area in blood vessels large?

A

The sum total is very large, because there are so many vessels in the body

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14
Q

Describe a practical application of Poiseuille’s equation

A

Two type of cannula.

When the diameter is doubled, the flow increases by more than double

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15
Q

What are the different pressures?

A

Systolic: left ventricular contraction
• around 120 mmHg

Diastolic: left ventricular relaxtion
• around 80 mmHg

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16
Q

What is pulse pressure?

A

systolic - diastolic

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17
Q

What is MAP?

A

1/3(systolic - diastolic) + diastolic

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18
Q

What are the sensors in the fast control system of the cardiovascular system?

A

Stretch receptors (baroreceptors) in the aorta and carotid arteries

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19
Q

What are the effectors in the fast control system of the cardiovascular system?

A 
Cardiac output
Vasomotor tone (TPR)
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20
Q

What are the sensors in the slow control system of the cardiovascular system?

A

Sensory cells in the kidneys

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21
Q

What are the effectors in the slow control system of the cardiovascular system?

A

Hormones influence:
• vasomotor tone
• electrolyte balance

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22
Q

Where are the baroreceptors?

Draw this

A
  • Aortic arch sinus

* Carotid sinuses (Internal carotid arteries)

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23
Q

Which nerve innervates the internal carotids?

How about the aortic arch baroreceptors?

A

Internal carotids:
• IX - Glossopharyngeal nerve

Aortic arch:
• X - Vagus nerve

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24
Q

Describe what happens when there is elevated BP

A

Fast:

  1. Elevated BP
  2. Stretch of blood vessel cells
  3. Detection of the stretch by baroreceptors
  4. Sensory nerve brings this information to the vasomotor area in the brain
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25
Q

What is the role of the carotid bodies?

A

These are secondary receptors

  1. Significant drop in BP
  2. Less flow to carotid bodies
  3. Fall in O2 in carotid bodies
  4. Stimulation of carotid bodies
  5. Stimulation of area in brain
26
Q

Which is the area of the brain where we control blood pressure?

A

Vasomotor area

In the brain stem

27
Q

What are the inputs to the vasomotor area?

A
  • Baroreceptors
  • Chemoreceptors (carotid bodies)
  • Skeletal muscle proprioceptors
  • hypothalamus: thermoregulation
  • Cortical: fear etc.
28
Q

Why does the vasomotor area receive proprioceptor information?

A

The area know we are running

Before we accumulate an oxygen dept, it sends more blood to the lower limbs

29
Q

What are the outputs from the vasomotor area?

A

1/ Vagus nerve

2/ Sympathetic nervous system

30
Q

Describe the function of the vagus nerve

A

Normally, there is Inhibition the acceleration of heart rate etc.

The role of the vagus nerve is to inhibit cardiac function

31
Q

What are the targets of the sympathetic nervous system in the cardiovascular system?

A
  • Heart; increased stroke volume and rate
  • Constriction of resistance vessels
  • Capactance vessels (veins); change in diameter
  • Adrenaline secretion from adrenal gland
32
Q

What are the effectors of the fast control system?

A
  • Heart
  • Arterioles: change in PR
  • Veins: draining of blood from gut
  • Adrenal glands: adrenaline release
33
Q

Describe how septicaemia affects the cardiovascular system

A

Endotoxin → shock
Widespread vasodilation
Insufficient pressure to supply the vital organs

34
Q

Describe Harlequin syndrome

A

Genetic disorder whereby there is abnormal sympathetic innervation of one side of the face

Vasodilation on one side of the face

35
Q

What happens to blood flow in anaesthesia?

A

Paralysed: no muscle pump

No sympathetic nervous system to control flow

36
Q

What are the sensory cells in the kidney?

A

Macula densa

37
Q

Describe the slow control system when there is a drop in BP

A
  1. Drop in BP
  2. Detection by the juxtaglomerular cells
  3. Release of Renin
  4. Renin converted to angiotensin
  5. Angiotensin brings about:
    a. vasoconstriction
    b. aldosterone release
  6. Aldosterone causes Na+ and water retention
  7. Permeability decreased → conservation of fluid
  8. Less water excreted
38
Q

What two things do the sensory cells in the kidney detect?

A

Filtering of blood

Arterial stretch

39
Q

What does angiotensin bring about?

A

a. increase in BP via vasoconstriction
b. release of aldosterone
c. thirst
d. ADH release
e. increased sympathetic activity
f. constriction of efferent arteriole in nephron
g. increase reabsorption

40
Q

What happens sometimes when there is too much fluid retention?

A

Pulmonary oedema

Wound dehiscence

41
Q

What do we do when the kidneys fail?

A

Dialysis:
external cleaning of the blood

Can be permanent or temporary

42
Q

What are the local responses to exercise?

A
  • 30 x increase of muscle blood flow
  • CO2 rise, O2 fall
  • local vasodilation
  • Temperature rise (due to vasodilation)
  • capillaries open
43
Q

Describe, quickly, muscle flow at rest

A

Low blood flow to the muscles at rest

44
Q

When does blood flow into muscle?

A

During muscle relaxtion

45
Q

Describe the muscle pump

A

Muscle relaxtion: venous pooling in sinuses in muscle

Muscle contraction: blood expelled from the muscles

46
Q

What are the systemic responses to exercise?

A 
1. Temporary fall in BP
(TPR is reduced)
2. Fall in pressure detected by baroreceptors
3. Vasomotor area 
4. Increase in BP
47
Q

What happens to blood flow to the brain during exercise?

A

Blow flow remains constant

The percentage of blood it gets falls

48
Q

What happens to blood flow to the heart during exercise?

A

Increased blood flow to heart

Percentage remains the same

49
Q

What happens to blood flow to the skin during exercise?

A

Increase in flow

50
Q

What happens to blood flow to the skin during exercise?

A

Remains roughly constant
• need blood flow here to thermoregulate

Percentage of the blood it gets falls

51
Q

What happens to blood flow to the GIT and kidneys during exercise?

A

Blood flow decreases

Percentage decreases

52
Q

Why do kidneys receive less blood during exercise?

A

Inconvenient to urinate when exercising

Losing fluid through sweating

53
Q

Describe orthostatic hypertension

A

When we quickly stand up, there is a drop in BP because our body isn’t actively pumping blood back to the heart

Overcome by the baroreceptor reflex

54
Q

Describe the baroreceptor reflex

A
  1. Baroreceptor receptors detect a drop in stretch
  2. Vasomotor area
  3. Effectors:
    • HR increases
    • TPR increases
    • CO increases
55
Q

When standing up, what are the challenges faced?

How is this overcome?

A

Blood must be pumped all the way back up to the heart against gravity.

The muscle pumps in the legs are heavily relied on.

Standing still (soldiers) can faint because they are not using their muscle pumps

56
Q

Describe the response after significant blood loss

A
  1. Decrease in blood volume and blood return to heart
  2. Reduced ventricular stroke volume
  3. Fall in cardiac output and BP
  4. Reduced stretch of baroreceptors
  5. Reduced inhibition of vasomotor area
  6. Removal of inhibition of the vagus nerve
  7. Increased HR etc.

Sympathetic stimulation:
• increased HR and SV
→ increased CO

• Constriction of vessels in the splanchnic circulation

Kidneys

  1. Reduced BP and filtering
  2. Stimulation of juxtaglomerular apparatus
  3. RAAS activated
  4. Normal BP restored
57
Q

What are the outcomes of the response to significant blood loss?

A

Increased BP
Stroke volume improved
Blood directed to vital organs

58
Q

When are the carotid bodies stimulated?

A

Severe reduction in cardiac output

59
Q

What happens over the next few days after significant loss of blood?

A

RAAS persists

Behaviour:
• drinking
• transfusion

60
Q

Describe the physical features of cardiovascular shock

A
  • Pale skin: vasoconstriction
  • Cold: vasoconstriction
  • Blue blood at skin: cyanosis, oxygen extracted from blood
  • Fast pulse: increased heart rate
  • Weak pulse: low stroke volume
  • Confusion, restlessness: reduce in blood flow to the brain
  • Reduced urination
  • Nausea: reduced blood flow to gut
  • Loss of consciousness

BIOM20002 - HSF (60 decks)

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