Lecture 16/17: Cardiovascular system (part 2) Flashcards
What is the driving force of blood flow?
changes in pressure
How can blood flow be calculated
- flow= cardiac output (CO)
- pressure= mean arterial pressure (MAP)
- resistance= total peripheral resistance (TRP)
CO=MAP/TPR
MAP=COxTPR
(pressure=output x resistance)
What is systolic and diastolic blood pressure?
- systolic: maximum pressure, when ventricles contract sending blood back to arteries
- diastolic: minimum pressure, when heart relaxes between beats (not zero) due to elastic recoil of arterial wall.
- note blood never fully gone so there is pressure during diastole
How is average BP determined
- average of systolic and diastolic
- must take into consideration the time body spend in each
- 1/3
SP and 2/3 resting (if exercising would inc)
What controls blood pressure?
arterioles
- metabolic, neural and endocrine factors trigger changes
What is Vasoconstriction?
- smooth muscle contraction
- dec in radius/diameter increasing resistance
What is Vasodilation?
- smooth muscle relaxation
- inc radius/diameter
- decrease resistance
How does metabolic activity effect blood pressure
- increased metabolic activity= local vasodilation
- levels of : CO2, H+, K adensoine (from breakdown of atp) increase
- decreased metabolic activity= local vasoconstriction
- ince in O2 levels
How does neural control influence arteriolar diameter?
- vasoconstriction:
- norephinephrine binds to a2 adrenergic receptors
- epinephrine bind to A2 receptors
- both inc TRP and MAP
- Vasodilation:
- in skeletal and cardiac muscle beds due to B2 adrenergic receptors
- decrease TRP and MAP
How does the endocrine system control arteriolar diameter?
- Antidiuretic hormone (vasopressin): posterior pituitary
- inc water reabsorption by kidneys to retain water
- vasoconstriction at high concentrations: inc in TRP
- Angiotensin II
- angiotensinogen- (renin)-> angiotensin I-(ACE)-> angiotensin II
- vasoconstriction, Inc TRP
What is ACE?
Where is it produced?
What is an application?
Angiotensin converting enzyme (converts from I to II)
- produced by lung
- if inhibited it a bommon medication to treat hyper tension
What are Baroreceptors?
- respond to stretch
- communicates with cardiovascular control centre (medula oblongata) to decrease SNS/increase PNS output
- when bp inc, increases firing rate
- opp when bp drops
If there was a hemorrhage, how would BP be regulated
- EXAM
- blood volume is decreasing
- cardiac output dec
- dec in MAP (pressure)
- Baroreceptors: dec firing of action potentials
- Cardiovascular control centre: PNS activity and Ach dec which inc HR
- Cardiovascular control centre: inc SNS activity and NE which inc HR and contraction strength, vasoconstriction and blood volume
- note what would happen in opp situation
- would not be effective if blood is continuously lost
Why do people faint?
- blood flow to brain decreases
- Heart rate
How can exercise (aerobic) regulate blood low?
- increases cardiac output by 5-8x
- recall MAP=CO x TRP
- MAP (BP) does not increase during exercise because TPR levels decrease
- distribution of blood is diverted to areas it is needed (working muscles)
- dilation of vessels to skeletal muscle and heart inc blood flow to muscles due to B2 receptors & local metabolites
- Constriction of vessels to GI tract and kidneys decrease blood flow to these organs (a2 receptors)
