Mean Arterial Pressure: Lecture 9 Flashcards
What determines mean arterial pressure?
rearrange cardiac output equation
MAP = cardiac output x total peripheral resistance
Why is the MAP so important? What is it’s purpose?
- Contributes to Hearts workload
- Provides driving forces to move blood
- The number 1 regulated thing in our body
- otherwise impaired nutrients and oxygen
What does hypotension refer to?
low blood pressure
What is our systolic bp and diastolic bp for hypotension?
90/60 mm Hg
What are the 4 main symptoms of hypotension?
- Dizziness
- Fainting
- Blurred vision
- Fatigue
What causes these symptoms of hypotension
- insufficient blood flow to the brain, muscles
- insufficient oxygen distribution
What are the causes of hypotension?
- dehydration
- pregnancy
- heart failure
- anemia
What are the risk factors for hypotension?
- age
- medication
- certain diseases
Why would Parkinson’s disease lead to low blood pressure?
it affects the autonomic nervous system, aka PNS and SNS to regulate blood pressure
Is Hypotension or Hypertension known as the silent killer?
Hypertension
What does hypertension refer to?
High blood pressure
What are the ranges of systolic and diastolic bp in stage 1 of hypertension?
130-139/80-89 mm Hg
What are the ranges of systolic and diastolic bp in stage 2 of hypertension?
> =140/>=90
What are the ranges of systolic and diastolic bp in stage 3 (Hypertensive crisis) of hypertension?
> 180/>120 EMERGENCY
What are the severe symptoms of hypertension?
- stroke
- heart attack (myocardial ischemia)
- kidney failure
- blindness
- dementia
- sexual dysfunction
What are the causes of hypertension?
- atherosclerosis
- kidney disease
- sleep apnea
- thyroid issues
What are the risk factors for hypertension?
(most are modifiable)
- age
- genetics
- obesity
- inactivity
- smoking
- high sodium intake
- stress
- alcohol consumption
Conduit vessels refer to what?
Arteries
What is the function of an artery?
takes blood from the heart and distributes it to the various organs/tissues
How do we have blood flow move efficiently?
- Minimize the resistance
- via larger diameter
- low contractility, smooth muscle
- high compliance, elasticity - Artery walls need to be STRONG
In a rested state how much blood do we have in the aorta during systole? and how long does it last?
75 ml, 0.3 seconds
Is the stretch of the aorta when blood comes into it passive or active?
passive
During systole, the aorta and heart will do what?
aorta = expands passively
heart = contracting and emptying
During diastole, the aorta and heart will do what?
aorta = recoil passively
heart = relaxing and filling
*aortic valve is shut meaning blood has to move forward
What are the Major benefits of compliance?
- Lowers systolic blood pressure
- via stretching, more volume more space to go - Converts intermittent flow into continuous blood flow
- aka Windkessel effect
What is the Windkessel effect?
helps to dampen the fluctuations in blood pressure over a cardiac cycle and maintains continuous blood flow when ventricular ejection ends (diastole)
What allows aortic compliance?
elastin
What is elastin?
matrix protein that increases compliance
Where can elastin be found?
- arteries
- tissues
What is the equation for compliance?
compliance = volume/pressure
If we want high compliance what would need to increase the volume or the pressure?
volume
If we want low compliance what would need to increase the volume or the pressure?
pressure
What is pulse pressure?
it is the pressure that dictates the movement of blood flow through the systemic circulation
How do we calculate pulse pressure?
systolic pressure - diastolic pressure
What does the Aortic valve closure refer to?
dicrotic notch
How do we calculate Mean arterial pressure with knowing systolic and diastolic pressures?
MAP = DP + 1/3 (SP-DP)
What are the factors that regulate Pulse Pressure?
- Stroke Volume
- Speed of blood ejection into the aorta
- Aortic compliance
How does stroke volume affect Pulse pressure?
- increased stroke volume will lead to increased systolic blood pressure
- more pressure more heart contractility which leads to increased pulse pressure
How does the speed of the blood ejection into the aorta affect Pulse pressure?
- if the heart is contracting more that will increase the speed as well as increase heart rate will all cause increased contractility
- Increased contractility will cause increases in systolic blood pressure which leads to increased pulse pressure
How does the aortic compliance affect the Pulse pressure?
- more compliant aorta will drop systolic blood pressure
- reduce systolic blood pressure which will decrease Pulse pressure
When we age which pressure will increase a bit more?
systolic blood pressure
Why would aging affect our pulse pressure?
- aorta becomes less compliant, elastin properties will deteriorate
What happens to our blood pressure during weightlifting?
- drastic increase in mean arterial pressure
- double or three times during resistance exercise
Why does our MAP, and systolic blood pressure increase as we weight lift?
exercise pressor reflex
What is the exercise pressure reflex?
- we generate lots of tension in our skeletal muscles
- High tension can activate mechanoreceptors inside our muscles as well as metabolite receptors
- The high tension generated in your fibres will accumulate lactate and that will detect muscle afferents
- that will generate an autonomic response to increase SNS and drop PNS aka increase stroke volume and increase vasoconstriction to other places that do not need lots of blood flow
- all increasing systolic blood pressure
