Blood pressure and its regulation

Question 1

What is arterial blood pressure defined as?

Answer 1

Pressure exerted by blood flow on blood vessel walls

Question 2

What is arterial BP equation?

Answer 2

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

Question 3

What does TPR tell us about?

Answer 3

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

Question 4

Why is BP important?

Answer 4

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

Question 5

What is considered normal BP?

Answer 5

120/80 mmHg

Question 6

What does the 120 mmHg mean in BP?

Answer 6

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

Question 7

What does the 80 mmHg mean in BP?

Answer 7

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

Question 8

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

Answer 8

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

Question 9

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

Answer 9

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

Question 10

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

Answer 10

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

Question 11

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

Answer 11

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

Question 12

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

Answer 12

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

Question 13

What does a BP too low cause?

Answer 13

Low drive for convection transport, insufficient O2 transport

Question 14

What does a BP too high cause?

Answer 14

Risk for cardiovascular disease

Question 15

What systems increase or respond to low BP?

Answer 15

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

Question 16

What systems reduce or respond to raised BP?

Answer 16

Cardiac Natriuretic Peptides

Question 17

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

Answer 17

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

Question 18

How does the RAAS system work?

Answer 18

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

Question 19

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

Answer 19

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

Question 20

What is the secretion of ADH stimulated by?

Answer 20

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

Question 21

What is ADH also called?

Answer 21

Vasopressin

Question 22

What are the direct actions of ADH?

Answer 22

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

Question 23

What are ANP and BNP released from?

Answer 23

Released from specialised cells in atria of the heart

Question 24

What causes the release of ANP/BNP?

Answer 24

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

Question 25

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

Answer 25

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