Blood pressure and its regulation Flashcards

1
Q

What is arterial blood pressure defined as?

A

Pressure exerted by blood flow on blood vessel walls

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2
Q

What is arterial BP equation?

A

Arterial BP = Cardiac Output (CO) x Total Peripheral Resistance (TPR)

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3
Q

What does TPR tell us about?

A

TPR tells us about the resistance/radius of arteries and arterioles
e.g., More constricted the vessels the more blood flow exerts pressure,
as such blood flow exerts less pressure through more dilated vessels

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4
Q

Why is BP important?

A

This means measuring BP can tell us about:
Heart rate
Stroke volume,
Whether vessels are constricted/dilated
Blood flow to our tissues
Ultimately, informing you about whether tissues and organs
are receiving appropriate O2 transport

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5
Q

What is considered normal BP?

A

120/80 mmHg

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6
Q

What does the 120 mmHg mean in BP?

A

Blood pressure in the brachial artery during ejection of the left
ventricle = Systolic blood pressure (SBP)

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7
Q

What does the 80 mmHg mean in BP?

A

Blood pressure in the brachial artery during relaxation and filling
of left ventricle, non-ejecting phase of heart
= Diastole blood pressure (DBP)

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8
Q

What BP is too high and what can this lead to?

A

Chronic BP >140/90 mmHg becomes a risk factor for
cardiovascular disease e.g., myocardial infarction, heart failure

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9
Q

What BP is too low and what can this lead to?

A

Difficult to be absolute, but SBP <80 and/or DBP <60 would
be a concern – poor blood flow and O2 transport

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10
Q

An exercising student lifts heavy weights at gym
Their BP increases to 160/95 mmHg from a resting value of 118/83 mmHg, why?

A

Muscles need more O2
Increase blood flow by increasing CO through increasing HR and SV
Heart working faster + stronger contraction (Sym NS)
Increasing BP

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11
Q

An individual suffers haemorrhage in a road-traffic accident
Their blood pressure is 85/70 mmHg, why?

A

Blood volume is reduced, hypovolemia, less CO due to reduced SV
Decreased BP

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12
Q

A 65-year-old visits their GP for the first time in over 20 years, with symptoms
of low mood, the GP takes their BP several times with an average reading of
162/97 mmHg

A

Probable chronic high BP, hypertension
Why? Likely increased TPR, blood vessels are excessively vasoconstricted
Increased BP

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13
Q

What does a BP too low cause?

A

Low drive for convection transport, insufficient O2 transport

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14
Q

What does a BP too high cause?

A

Risk for cardiovascular disease

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15
Q

What systems increase or respond to low BP?

A

Sympathetic Nervous System
Renin-Angiotensin-Aldosterone System (RAAS)
Anti-diuretic hormone (ADH or called Vasopressin)

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16
Q

What systems reduce or respond to raised BP?

A

Cardiac Natriuretic Peptides

17
Q

What happens in the sympathetic nervous system to increase heart activity?

A
  1. Stimuli such as a Drop in blood pressure due to decrease in HR, SV or TPR e.g., hypovolemia, dehydration. This stimulates baroreceptor reflex. also the higher brain function involved in prep for fear/flight/ fight. Both these will activate sympathetic nervous system
  2. Sympathetic system will act on adrenal gland to secrete adrenaline. The system will also secrete noradrenaline and allow for the production of RAAS which will produce angiotensin 2.
  3. This will ultimately increase heart rate activity and increase heart rate and stroke volume. It will also result in vasoconstriction, which will increase TPR
18
Q

How does the RAAS system work?

A
  1. A drop in blood pressure/ blood flow to kidney will result in the sympathetic nervous being stimulated.
  2. This will result in renin substrate angiotensinogen being converted into angiotensin 1.
  3. ACE is found in lung epithelium which converts angiotensin 1 to angiotensin 2.
  4. Once AT1R is activated, blood vessels will be vasoconstricted resulting in an increase in TPR. In addition, aldosterone will be produced which will act on the kidneys causing less H20 to be excreted. This increase blood volume, SV and CO
19
Q

Where is the antidiuretic hormone produced, released and excreted into?

A

-Hormone produced by neurons in hypothalamus
-Released from terminals into posterior lobe of pituitary gland
-Excreted into bloodstream

20
Q

What is the secretion of ADH stimulated by?

A

Decrease in blood volume associated with decrease in blood pressure
Sensed by cardiac pressure receptors in left atrium
Send signals to hypothalamus

21
Q

What is ADH also called?

A

Vasopressin

22
Q

What are the direct actions of ADH?

A
  1. Direct action on blood vessels causing Vasoconstriction. this increases TPR
  2. Direct action on kidney. This results in an insertion of aquaporin ‘water’ channels in collecting duct of kidney
    -This increases H20 retention
    -This increases blood volume
    -This increases SV and CO
23
Q

What are ANP and BNP released from?

A

Released from specialised cells in atria of the heart

24
Q

What causes the release of ANP/BNP?

A

Sense increase in cardiac filling pressure due to increase in Blood volume and BP

25
Q

What are the direct actions of an increase in ANP/BNP secretion?

A
  1. Kindey. There’s an increase in excretion of H20. this leads to decrease in blood volume, SV and CO as well as BP
  2. Blood vessels. Causes vasodilation which decreases TPR and blood pressure