Blood pressure Flashcards
What is systolic pressure?
pressure in system when heart contracts- area of high pressure
What is diastolic pressure?
pressure when heart relaxed- blood vessel pressure drops
What do you measure blood pressure in?
mmHg - millimetres of mercury
What is blood pressure described as
Pressure of blood in major blood vessels of heart
How do you measure blood pressure in dogs?
Take a chorotid artery
Put a canula ( tube) in it
When the heart contracts it will push blood against the column of mercury- makes the column of mercury go up
When the heart relaxes- the column of mercury goes down
Read off column of mercury high and low pressure point
What do you use to measure humans blood pressure
Sphygmomanometer
How do you measure blood pressure in humans?
- Wrap a cuff around arm which is attached to the bulb
that can inflate the cuff , putting pressure on the brachial artery. - apply enough pressure to collapse that artery - means you are above the systolic pressure
- Slowly release pressure from cuff, until that point where some blood starts to flow = applying a little less pressure= systolic pressure
- The more air you let out the bag, more blood flows through, until you are not constricting blood flow or collapsing artery= diastolic pressure
- Determing the pressure when blood vessel first starts opening which is systolic pressure, and the pressure when the blood vessel is not collapsed at all= diastolic pressure.
What is brachial artery
a superficial blood vessel in the upper arm
What happens when normal blood flow in vessel
No noise = flowing smoothly = can hear turbulant blood flow
What are the sounds of Korotkoff?
When sounds dies away.(diastolic)
No turbulant blood flow = not restricting vessels at all =
What does a stethoscope do when you measure blood pressure?
put just below the cuff on breakel artery,
normal blood flow of muscle makes no noise- as it flows smoothly
Decrease pressure in cuff, some blood is starting to flow through, you will hear a soft tapping= systolic pressure
Decrease pressure even more, more and more blood starts to flow, makes a continuous rushing sound, then the sound dies when there is no turbulent blood flow and no constricting vessel which means you are at the Diastolic pressure.put just below the cuff on breakel artery, normal blood flow of muscle makes no noise- as it flows smoothly
Decrease pressure in cuff, some blood is starting to flow through, you will hear a soft tapping= systolic pressure
Decrease pressure even more, more and more blood starts to flow, makes a continuous rushing sound, then the sound dies.
How do you determine blood flowing?
Using a stethoscope- from its sounds that it makes
How do you write the blood pressure?
systolic/diastolic
What is the average blood pressure?
120/80
Why does the measured blood pressure vary throughout the circulatory system
As its highest and its greatest variation is in the major arteries near the heart such as the arota larfe and small arteries and arterioles
However then by the time the blood returns to the heart via the vena cava, the pressure is almost 0(drops) and variation gets less due to being so far from the pump and heart and the elastic nature of veins and blood vessels which will even out the blood flow.
What happens to blood pressure throughout the circulatory system
Varies
When is bp highest and variation is greatest
In major arteries nearest heart
Less in capillaries and veins
When is pressure almost 0
by the time the blood returns to the heart via the vena cava
What happens by the time the blood returns to heart via vena cava
variation gets less due to being so far from the pump and heart and the elastic nature of veins and blood vessels which will even out the blood flow
What happens if you cut artery
A lot of blood spurt out
What happens if you cut vein
Hardly any blood spurts out
How does blood pressure vary?
- From person to person (inter-individual)
- With age ( increases with age )
- Depend on what you are doing or feeling (intra-individual )
What to make sure when taking bp
- Px relaxed
- Take it same time every day as it varies according to time of day
What happens if you take b.p and its not 120/80, should you refer straight away
No, dont refer to health service, need to investigate - factors, repeats
What is white coat syndrome
People scared coming to see doctors which increases bp = variable
What is the bp formula?
bp = cardiac output x peripheral resistance
What are the 2 main things blood pressure depends on?
- How hard the heart is contracting
- How wide the blood vessels are
What is cardiac output
How hard contracts, force of cardiac contraction
Peripheral resistance
Diameter of blood vessels
What happens when blood pressure increases?
Blood vessels constricting- Heart contracts harder- cardiac output increases
What happens when blood pressure decreases?
Blood vessels dilate- cardiac output decreases
What causes rise in mean bp with age
Loss of elasticity - (arteriosclerosis), resulting in raised peripheral resistance = blood vessels narrow, dont dilate much
What are the mechanisms which regulate arterial blood pressure?
- Rapid - baroreceptors ( nervous ), Renin/angiotensin ( humoral)
- Long-term - Kidney - Pressure diuresis
How long are baroreceptors active for
1 day
What are baroreceptors and example of and what are they
Fast nervous mechanism of controlling bp
Relies on nerve
Stretch receptors located in walls of arteries, in particular cartoid and aortic arch
What are these stretch receptors?
free nerve endings which are stretched when blood vessels dilate ( mechanoreceptors )
What happens when there is a rise in blood pressure?
When blood pressure goes up, our arteries stretch so it activates stretch/baroreceptors - this sends impulses to medulla which causes vasodilation or decreased cardiac output
What are the 2 ways that the medulla reduces blood pressure?
- the medulla sends a.p down towards peripheral blood vessels and causes vasodialation, which increases diameter of blood vessels, and blood pressure will fall
- Via vagus nerve ( which is the parasympathetic stimulation of the heart), decreases cardiac output, blood pressure falls and barorecpetors no longer stimulated.
When are baroreceptors no longer stimulated
Lowered bp due to decreased peripheral resistance and decreased cardiac output
What do recordings from Herrings nerve show
comes from the carotid baroreceptors which show they respond to blood pressure
-Show as you increase blood pressure , the baroreceptors fire more a.p and are sensitive to blood pressure
What happens if baroreceptors are inactivated
Cant control bp i.e. pressure varies a great deal throughout day
How does the rapid, humoral, renin/antigotensin mechanism regulate arterial bp
Responds to FALL in bp
What does renin/antigotensin mechanism rely on
Hormones
When does the renin/antigotensin mechanism kick in
After about 30s and stops after about 1/2 days
What happens in the renin/angiotensin system?
Arterial Blood pressure drops
Kidney ( RENIN GLOMERULAR COMPLEX - bit of kidney ) senses bp drops = releases renin which acts on a plasma protein = production of angiotensin 1 = converted to angiotensin 2 by an enzyme called angiotensin converting enzyme (ACE)
What is angiotensin II
Vasoconstrictor which causes blood vessels get smaller and blood pressure rises.
What does angiotensin converting enzyme do
angiotensin 1 converted to angiotensin 2
What are smooth muscles made to contract by
Hormones
What can abnormal ACE levels lead to
It is a genetic defect and causes high bp = Increased risk of heart attack
What do ACE inhibitors do
Possible therapy - inhibits ACE enzyme - turns system off which decreases bp
Which mechanism is long term control of bp
Kidney - pressure diuresis
What happens in Pressure Diuresis?
Kidney- produces urine so controls body fluid levels
-If the blood pressure rises , it stays high , the kidney produces more urine which lowers plasma/ blood volume and lowers blood pressure.
Bp increases = pee more
Why is Pressure Diuresis a good mechanism
Control bp over longer term due to kidney - regulate urine output
What is hypertension?
a prolonged period of high blood pressure
What is then meant by ‘high blood pressure’ in hypertension?
-As in World Health Organisation- if the systolic pressure above 140 to 160 and diastolic is above 90
What is a normal blood pressure?
if systolic pressure below 140
diastolic blood pressure is below 90
Systolic is more prone?
it has much more variation, as more things can affect it such as being tired, our activities etc
Why is diastolic pressure is less prone to short term fluctuations
less subject to systemic influences and is therefore a more useful guide to blood pressure.
What does the american heart association show?
Normal bp- is less than 120 and less than 80
Elevated bp- 120-129 and less than 90
Hypertension- is 130-139 or 80-89
Hypertension stage 2- 140 or higher or 90 or higher
What is the classification of systemic hypertension?
In most cases 85% of the causes of hypertension are not known.- This is known as idiopathic, primary or essential hypertension.
15% of hypertension is secondary to some other diseases (usually renal or adrenal in origin)
Benign and Malignant - see below
What are the risk factors for primary hypertension ?
genetic predisposition
stress/emotion
obesity
excessive alcohol (small amounts may be benefical)
sodium( in 50% of cases hypertension is salt resistant)
this is the aetiology of the disease
What are the long term effects of hypertension ?
kidney damage
increased bulk of heart leading to angina pectoris
damaged arteries leading to atherosclerosis - renal failiure - due to kidney failure
What is border line bp
Systolic between 150 and 140
Diastolic between 90 and 95
Whats the difference between benign and malignant hypertension
Benign = slow onset (symptomless then sudden) = chronic
malignant (fast onset) = (symptoms occur quick and bp can suddenly shoot up- causing death quick) - more dangerous
What happens if you dont normalise bp
In retina blood vessels bursting in fundus = hemerage and papilledema
Tumour of adrenal gland increases cardiac output
