HEART PHYSIOLOGY II Flashcards
why does we need mean arterial pressure (MAP)?
blood pressure is high and oscillatory in major arteries –> MAP is important in determine blood flow
how does blood pressure change across arterioles –> capillaries –> venules
fall steeply
where can we detect the lowest blood pressure?
veins
because there is a ____1_____ difference in pressure between ___2___ and _____3______, there for a ____4_____ for bloodflow is created
1: large
2: arteries
3: veins
4: driving force
formula for blood flow?
Flow (Q) = Pressure difference / Resistance (R)
However, pressure difference = MAP since the pressure downstream is so low it counts as zero
==> Flow = MAP / Resistance <=> MAP = Q x R
how do we determine blood flow “in” and “out”
- “in” = how much volume blood/time unit the heart puts into the arteries system
- “out” = resistance
formula for MAP?
MAP = cardiac output (CO) x total peripheral resistance (TPR)
formula for CO (cardiac output)
CO = SV (stroke volume) x HR (heart rate)
unit of CO, SV and HR
- CO = L/min
- SV = L/beat
- HR = beat/min
what does stroke volume and heart rate related to a maintain cardiac output and heart condition?
cardiac output needs to be maintained the same, therefore:
- healthy heart has a large stroke volume with low heart rate
- failing heart on the other hand has a low stroke volume with high heart rate
what are baroreceptors? where are they primarily located and what afferent signal do they send to the brain?
- stretch receptors
- embedded in artery walls: aortic arch and carotid arteries
- send signal when the wall is stretching –> tell brain the heart beat and the blood pressure
difference between sympathetic and parasympathetic signaling?
- parasympathetic = brake effect: signaling through vagus nerve, then to AV (slow down) and SA node to slow down the HR
- sympathetic = accelerate effect: signaling through sympathetic trunk ganglion to wall of ventricles (to increase stroke volume) and to AV (hold impulse faster) and SA (more HR)
how do we increase cardiac output during exercise?
increase HR and SV
how is homeostasis of blood (arterial) pressure is maintain
afferent to brain and efferent output
what happen when MAP increase?
- baroreceptor in aortic arch and carotid sinus detect the increase in MAP
- information being fed to medulla obloganta
- form the integration centre, the signal is being sent and effect to reduce TPR, SV and/or HR
how is a sudden stand up would increase your heart rate?
- standing up reduce the filling –> decrease the end-diastolic-volume (EDV)
- lower EDV means less force for contraction
- less force –> reduce SV –> reduce CO
- CO decrease = MAP decrease
==> increase HR to maintain the homeostasis
what is the approximate total blood volume
5L
what are the blood distribution percentage of the major organs?
- brain: 14% –> 700mL
- coronary: 4.5%
- kidney: 20% –> 1000mL
- GI: 25%
- skeletal muscle: 29% –> 1450mL
- skin: 7.5%
define compliant and rigid, then relates to the wall of vessels
- compliance = the extent to which a vessel allows deformation in response to an applied force
- compliant = stretchy
- rigid = not flexible
–> veins wall are thinner and more compliant while arteries have thicker wall therefore more rigid
formula of compliance?
compliance = volume difference / pressure difference
relate the formula of compliance to the vessels to explain the difference in compliance betwwen arteries and veins:
- arteries: small volume, large pressure
- veins: large volume, small pressure
how do veins store more blood at low pressure?
thin tunica media –> more compliant
define survival value of veins
an extra volume of blood being stored in the systemic veins
why is it dangerous if the artery was cut/being leaked
loss of arterial blood and fall in arterial pressure –> life-threatening
what is blood pooling?
accumulation of blood in the vein due to high volume of blood in veins, gravity and the stretchiness of vein, as well as venous volume below heart increase while above the heart decrease
what are the 2 mechanisms to prevent venous pooling?
- valves: maintain anti-gravitational unidirectional blood flow
- muscle tone: stiffen the veins –> make them less compliant
how the venous muscle being affect?
- skeletal muscle pump affects the venous return to the heart
- muscle contractions increase venous blood flow
state the Starling’s Law of The Heart
the more stretched muscle fibres are before a contraction, the stronger the contraction would be
valves superior/inferior to the contracting muscle are forced to open/close to do what?
- superior valves open to allow venous return
- inferior valves close to ensure unidirectional blood flow
one of the ways to increase stroke volume is
increase venous return
why increase venous return would directly affect the stroke volume
- based on Starling’s law, more stretch –> more force of contract
- more venous return = more volume
- more volume = ventricles stretch more –> sarcomeres larger –> max contraction
what does it means by saying isovolumetric contraction?
is when the heart chambers contract but no corresponding volume change (meaning no fillings or pumping)
define trabeculae carnae and reflects their function
the twisting arrangement of cardiomyocytes as they contract to get efficient ejection
what happens to the blood distribution at different times/activities?
cardiac output being divided and tend to bias over the organs that are high-consumer of blood e.e. muscle for muscle, skin for regulation, heart
what happen to the distribution of cardiac output during exercise?
- increase blood flow to: muscle, heart, skin
- decrease blood flow to: GI, kidneys
- constant blood flow to brain
what is the rule of 16?
if the blood vessel radius double in size due to vasodilation, the blood flow through the vessel would increase 16-fold
define vasodilation and vasoconstriction
- vasodilation = vessels dilate
- vasoconstriction = vessels constrict –> decrease in radius
