Cardio 8 Flashcards
Describe pulse pressure.
-amplitude of pressure pulsations in an artery
-each cardiac ejection = pressure increases
[pulse pressure = systolic pressure - diastolic pressure]
indicator of SV because the magnitude of pulse pressure reflects the volume of blood ejected from LV for each beat
Describe pulmonary circulation VS systemic circulation.
-pulmonary circulation = low pressure
-systemic circulation = high pressure
Describe systolic pressure.
-pressure at the top of each pressure pulsation
-highest arterial pressure during a cardiac cycle
-pressure in arteries after blood is ejected from LV
Describe diastolic pressure.
-pressure at the lowest point of each pulse
-lowest arterial pressure during a cardiac cycle
-pressure in arteries during ventricular relaxation
Describe compliance.
[compliance = volume/pressure]
-if arterial compliance is constant = arterial pressure depends on volume of blood the artery contains at any time (systole/diastole)
Describe MAP.
[MAP = diastolic pressure + 1/3 pulse pressure]
-the pressure that drives blood into tissues during cardiac cycle
-monitored & regulated by BP reflexes
Describe dumping of the pressure pulses.
-compliance & resistance of arterial system = imp in reducing pressure pulsations
-blood doesn’t need to flow to peripheral vessels only during cardiac systole
-blood flows continuously & reaches capillaries with no pulsation
-degree of dumping is directly proportional to the product of resistance x compliance
Describe how pressure pulses waves travel.
- from high compliance (elastic arteries) to high resistance arteries (muscular arteries)
- intensity of pulsations become less in smaller arteries, arterioles, & capillaries
Describe elastic arteries.
-high compliance
-elastin
-pulse smoothing
-EX: aorta & carotid artery
Describe muscular arteries.
-high resistance
-smooth muscle
-capable to vasoconstriction/dilation
-EX: femoral & mesenteric arteries
Describe the TPR.
‘total peripheral resistance’
-resistance of systemic circulation (pressure difference)
[MAP = CO X TPR]
if MAP is increased, its due to CO or TPR increasing (or both)
Describe venous pressure VS arterial pressure.
-venous pressure in systemic circulation is lower than arterial pressure
-close to 0
-the resistance & compliance is due to the fall in pressure
Describe the CVP.
‘Central venous pressure’
REGULATED BY:
-ability of heart to pump blood out of RA & ventricle into the lungs
-tendency for blood to flow from peripheral veins into RA
*right heart pumps strong = RA pressure decreases
*weakness of heart rises RA pressure
What are the factors that increase venous return & RA pressure (CVP)?
- Increase in blood volume
- Increase in large vessel tone in body
-increase peripheral venous pressure - Dilation of arterioles
-decreased peripheral resistance
-allows rapid flow of blood from arteries into veins
*the factors that regulate RA pressure also regulate CO
Describe pulmonary circulation VS systemic circulation.
-pressure in pulmonary circulation is lower than systemic circulation
-pulmonary vascular resistance is lower
>1/12 resistance of systemic circulation
>pulmonary blood vessels are compliant & distend to increase blood flow
-blood flow through lungs match amount of air delivered to alveoli = ventilation-perfusion matching
Describe the PVR.
‘Pulmonary vascular resistance’
[PVR = mean pulmonary artery pressure - mean pulmonary venous pressure/CO]
Describe what MAP is regulated by.
- Baroreceptor reflex
-fast, neurally mediated reflex
-keeps arterial pressure constant via changes in the output of sympathetic & parasympathetic systems - Renin-angiotensin-aldosterone-system
-hormonal system
-regulates MAP by regulating blood volume
Describe the baroreceptor reflex.
-located in walls of carotid sinus & aortic arch
-mechanoreceptors
-sensitive to pressure/stretch
-relay info about BP to cardiovascular vasomotor centers in medulla oblongata
>travel via carotid sinus nerve (joins CN IX) & sensory division of vagus nerve CN X
>increase arterial-pressure, stretch & firing rate in afferent nerves (vice versa)
Describe the reflex arc of the baroreceptor.
- Receptor for BP
-baroreceptor - Afferent neurons
-carry info to medulla oblongata - Brain stem centers (medulla)
-process info & coordinate response - Efferent neurons
-direct changes in heart & blood vessels
What are the 3 cardiovascular centers located in the medulla?
- Vasoconstrictor center
- Cardiac accelerator center
- Cardiac decelerator center
Describe the vasoconstrictor center.
-vasomotor center
-efferent neurons
-sympathetic NS (synapse in spinal cord & then in sympathetic ganglia & then on target organ)
-causes vasoconstriction in arterioles & venules
(A1 & A2 = release NE)
Describe the cardiac accelerator center.
-efferent neurons
-sympathetic NS (synapse in spinal cord then sympathetic ganglia then heart)
-causes increase in firing rate of SA node (increase HR) & increase conduction velocity through AV node & increase contractility
B1
Describe the cardiac decelerator center.
-efferent neurons
-parasympathetic NS
-travel in motor division of vagus nerve & synapse in SA node
-causes decrease in HR
M2 = releases AcH
Describe the baroreceptor reflex steps from high BP to low.
strongest stimulus = rapid change in MAP
1. Increase in MAP detected & increase firing rate of afferent nerves
2. Afferent nerves synapse at medulla & coordinate responses comes from medullary cardiovascular centers
3. Increase in parasympathetic activity to SA node = decrease HR
4. Decrease in sympathetic activity to SA node also decreases cardiac contractility = decrease in CO
5. Decrease in sympathetic activity dilates arterioles (a receptor) & decrease TPR
6. Lead to decrease in MAP
Describe the response of baroreceptor reflex to hemorrhage.
Low BP to high BP.
Describe the receptor accommodation of the baroreceptor reflex.
-sensitivity of baroreceptors altered by disease
>less sensitive to a sustained stimulus over time
-if BP rises slowly or stable at high levels = receptors adjust response to accept new pressure as normal
>chronic hypertension = hypertension remained (rather than corrected by baroreceptor reflex)
