Cardiovascular Physiology Flashcards
3 organs that receive the most percentage of cardiac output:
Renal (25%), Gastrointestinal (25%), Skeletal muscle (25%)
Others: Brain 15%, Coronary 5%, Skin 5%
2 arteries that carry deoxygenated blood:
Pulmonary artery
Umbilical artery
The veins are called the reservoir of blood. How much of systemic blood is found in veins?
64%
What is the normal right atrial pressure?
0 - 4 mmHg
What is the normal pressure in the systemic capillaries?
17 mmHg
Blood flow velocity is fastest in the:
Aorta
Control conduits for blood flow, mainly under sympathetic control:
Arterioles
Blood flow velocity is slowest in the:
Capillaries
The capillaries cannot constrict or dilate because they lack:
Tunica media (only composed of a single layer of endothelial cells)
These structures allow capillary beds to be open or closed
Meta-arterioles and pre-capillary sphincter
What happens when systemic arterioles vasoconstrict?
TPR/SVR: increases
Blood flow: decreases
What happens when systemic arterioles vasodilate?
TPR/SVR: decreases
Blood flow: increases
What happens to blood pressure when TPR increases?
BP increases
What happens when veins vasoconstrict?
Venous return increases
Flow that is streamlined, highest at the center and lowest at the walls
Laminar flow
Flow that is disorderly, associated with high Reynold’s number; seen in anemia (dec blood viscosity) and vessel narrowing (inc blood velocity)
Turbulent flow
Normal pressure in the pulmonary arteries:
25/8 mmHg
Normal pressure in the pulmonary capillaries:
7 mmHg
3 organs that receive the most percentage of cardiac output:
Renal (25%), Gastrointestinal (25%), Skeletal muscle (25%)
Others: Brain 15%, Coronary 5%, Skin 5%
Reynold’s number for laminar flow
Reynold’s number for turbulent flow
> 2000
A strain in the structure of a substance produced by pressure, when its layers are laterally shifted in relation to each other
Shear
Shear is highest in:
walls of the blood vessel
Shear is lowest in:
center of the blood vessel
What is the consequence of shear?
Decreased blood viscosity
Compliance of veins vs arteries
24x higher compliance
Effects of aging on the compliance of arteries
Decreases compliance
Highest arterial blood pressure
Systolic pressure
Lowest arterial blood pressure
Diastolic pressure
____ = systolic pressure - diastolic pressure
Pulse pressure
____ = stroke volume/arterial compliance
Pulse pressure
____ = 2/3 (diastole) + 1/3 (systole)
Mean arterial pressure
Estimates left atrial pressure
Pulmonary capillary wedge pressure
Estimates left atrial pressure
Pulmonary capillary wedge pressure
2 arteries that carry deoxygenated blood:
Pulmonary artery
Umbilical artery
The veins are called the reservoir of blood. How much of systemic blood is found in veins?
64%
What is the normal right atrial pressure?
0 - 4 mmHg
What is the normal pressure in the systemic capillaries?
17 mmHg
Blood flow velocity is fastest in the:
Aorta
Control conduits for blood flow, mainly under sympathetic control:
Arterioles
Blood flow velocity is slowest in the:
Capillaries
The capillaries cannot constrict or dilate because they lack:
Tunica media (only composed of a single layer of endothelial cells)
These structures allow capillary beds to be open or closed
Meta-arterioles and pre-capillary sphincter
What happens when systemic arterioles vasoconstrict?
TPR/SVR: increases
Blood flow: decreases
What happens when systemic arterioles vasodilate?
TPR/SVR: decreases
Blood flow: increases
What happens to blood pressure when TPR increases?
BP increases
What happens when veins vasoconstrict?
Venous return increases
Flow that is streamlined, highest at the center and lowest at the walls
Laminar flow
Flow that is disorderly, associated with high Reynold’s number; seen in anemia (dec blood viscosity) and vessel narrowing (inc blood velocity)
Turbulent flow
Normal pressure in the pulmonary arteries:
25/8 mmHg
Normal pressure in the pulmonary capillaries:
7 mmHg
Reynold’s number for laminar flow
Reynold’s number for turbulent flow
> 2000
A strain in the structure of a substance produced by pressure, when its layers are laterally shifted in relation to each other
Shear
Shear is highest in:
walls of the blood vessel
Shear is lowest in:
center of the blood vessel
What is the consequence of shear?
Decreased blood viscosity
Compliance of veins vs arteries
24x higher compliance
Effects of aging on the compliance of arteries
Decreases compliance
Highest arterial blood pressure
Systolic pressure
Lowest arterial blood pressure
Diastolic pressure
____ = systolic pressure - diastolic pressure
Pulse pressure
____ = stroke volume/arterial compliance
Pulse pressure
____ = 2/3 (diastole) + 1/3 (systole)
Mean arterial pressure
Synonym of right atrial pressure
Central venous pressure
Estimates left atrial pressure
Pulmonary capillary wedge pressure
ECG: atrial depolarization
P wave
ECG: AV node conduction
PR segment
ECG: correlates with conduction time/velocity through the AV node
PR interval
ECG: ventricular depolarization
QRS complex
Causes of circus movements:
long conduction pathway, decreased conduction velocity, short refractory period
ECG: period of depolarization + repolarization of ventricles
QT interval
ECG: correlates with plateau of ventricular action potential
ST segment
What happens when sympathetic NS stimulates the AV node?
Increase in conduction velocity, decrease in PR interval
What happens when parasympathetic NS stimulates the AV node?
Decrease in conduction velocity, increase in PR interval
ECG: hypokalemia
flat/inverted T waves
ECG: hyperkalemia
low P waves, tall T waves
ECG: hypocalcemia
prolonged QT interval
ECG: hypercalcemia
shortened QT interval
ECG: STEMI
ST segment elevation
ECG: NSTEMI
ST segment depression
Ventricular action potential: Na influx (depolarization)
Phase 0
Ventricular action potential: K efflux (complete repolarization)
Phase 3
Ventricular action potential:
RMP
Phase 4
Ventricular action potential:
Ca++ influx (plateau)
Phase 2
Ventricular action potential: K efflux (partial repolarization)
Phase 1
SA node action potential:
Slow Na influx towards threshold
Phase 4
SA node action potential: Ca influx (depolarization)
Phase 0
SA node action potential: K efflux (repolarization)
Phase 3
Why is the SA node capable of authorhythmicity?
Opening of the K channels always triggers the opening of the Na channels (phase 3 is always followed by phase 4)
What happens to the slope of phase 4, action potential and heart rate when you stimulate the B1 receptors of the heart?
Slope: more steep
AP: shorter
HR: increase
What happens to the slope of phase 4, action potential and heart rate when you stimulate the M2 receptors of the heart?
Slope: more flat
AP: longer
HR: decrease
The SA node is called the master pacemaker. The AV node, bundle of His and Purkinje cells are called?
Latent pacemaker
Which node has the slowest conduction velocity?
AV node
Which node has the fastest conduction velocity?
Bundle of His, Purkinje fibers, ventricles
What is the basis for AV nodal delay (0.13secs)?
Decreased gap junctions in that area
Which Na channel accounts for SA node automaticity?
If channels (slow “funny” Na channels)
Isovolumic contraction: Preceded by \_\_\_\_\_\_ in the ECG \_\_\_\_\_\_ of atrial pressure is seen Semilunar valves are: \_\_\_\_\_ Ventricular pressure: \_\_\_\_\_\_ Ventricular volume: \_\_\_\_\_\_
QRS complex c-wave SL valves are closed VP: increases VV: remains the same
Inhibition of “pacemaking” of latent pacemakes by the SA node
Overdrive suppression
AV block that causes fainting in patients due to initially suppressed state of Purkinje fibers
Stokes-Adams syndrome
Condition when latent pacemaker assume pacemaking activity
Ectopic pacemaker
Reduced ventricular ejection:
_____ occurs in the ECG
Ventricular pressure: _____
Ventricular volume: _____
T wave
VP: decrease
VV: decrease
Occurs when, in the propagation of AP around the ventricles, the signal never reaches an area with absolute refractory period; basis for Vfib
Circus movements
Causes of circus movements:
long conduction pathway, decreased conduction velocity, short refractory period
All Na inactivation gates close, AP cannot be generated
Absolute refractory period
Some Na inactivation channels start to open, AP cannot be conducted
Effective refractory period
AP can be conducted and generated but higher than normal stimulus is required
Relative refractory period
All Na inactivation gates are open and membrane potential is higher than RMP; cell is more excitable than normal
Supranormal period
Produces changes in contractility
Inotropic effect
Produces changes in rate of relaxation
Lusitrophic effect
Produces changes in heart rate
Chronotrophic effect
Produces changes in conduction velocity
Dromotrophic effect
Inotropes affect the:
Stroke volume
Chronotropes affect the:
SA node
Dromotropes affect the:
AV node
Beta 1 stimulation of the heart would cause:
Stronger (positive inotrope), Briefer (positive lusitrope) and more frequent (positive chronotrope) contractions
An increase in preload will increase stroke volume within certain physiologic limits
Frank-Starling mechanism
Left ventricular end diastolic volume is directly proportional to what?
Venous return, right atrial pressure
What happens to SV and CO when preload increases?
Both increase
What happens to SV and CO, and velocity of sarcomere shortening when afterload increases?
All decrease
Blood ejected by the ventricle per heart beat; Equal to EDV-ESV
Stroke volume (Normal: 70mL)
Percentage of EDV that is actually ejected by the ventricle; Equal to SV/EDV
Ejection fraction (Normal: 55%)
Total blood volume ejected per unit of time; Equal to HR x SV
Cardiac output (Normal resting: 5L/min)
How long can the brain, heart and skeletal muscles last without O2?
Brain: 4 minutes
Heart and skeletal muscles: 6 hours
Primary source of energy for stroke work:
Fatty acids
Work per unit of time; Equal to CO x Aortic pressure
Cardiac minute work
2 components: volume work (cardiac output) and pressure work (aortic pressure)
Ratio of work output to total chemical energy expenditure
Maximum efficiency of cardiac contraction
Normal: 20 - 25%; most of energy is converted to heat
Cardiac events that occur in a single heartbeat
Cardiac cycle
Atrial contraction:
Occurs during the _______
Preceded by ______ in the ECG
______ of atrial pressure is seen
distal third of diastole
p wave
a-wave
What is the cause of the 4th heart sound?
Due to atria contracting against stiff ventricles, as seen in LV hypertrophy
Isovolumic contraction: Preceded by \_\_\_\_\_\_ in the ECG \_\_\_\_\_\_ of atrial pressure is seen Ventricular pressure: \_\_\_\_\_\_ Ventricular volume: \_\_\_\_\_\_
QRS complex
c-wave
VP: increases
VV: remains the same
The first heart sound is heard during:
Closure of AV valves during isovolumic contraction
Rapid ventricular ejection:
Ventricular pressure: _____
Ventricular volume: _____
VP: rapidly increase
VV: decrease
Phase of the cardiac cycle wherein semilunar valves open and blood flows from LV to aorta; atrial filling also begin
Rapid ventricular ejection
Reduced ventricular ejection:
_____ occurs in the ECG
Ventricular pressure: _____
Ventricular volume: _____
T wave
VP: decrease
VV: decrease
Isovolumic relaxation: \_\_\_\_\_ of aortic pressure is seen \_\_\_\_\_ of atrial pressure is seen AV valves are: \_\_\_\_\_\_ Ventricular pressure: \_\_\_\_\_ Ventricular volume: \_\_\_\_\_
Incisura v wave AV valves are closed VP: decreases VV: remains the same
The second heart sound is heard during:
Closure of the semilunar valves during isovolumic relaxation
Rapid ventricular filling:
occurs during _________
_____ heart sound may be heard
first 1/3 of diastole
3rd heart sound
Reduced ventricular filling (diastasis)
occurs during _________
middle 1/3 of diastole
What is the longest phase of the cardiac cycle?
Diastasis
Where are murmurs best heard?
Aortic: 2nd ICS RPSB
Pulmonic: 2nd ICS LPSB
Tricuspid: 4th ICS LPSB
Mitral: 5th ICS LMCL
Physiologic murmurs occur only during systole or diastole?
Systole
What is the murmur that is heard both on systole and diastole?
Continuous machinery murmur of PDA
Center responsbile for regulation of HR and BP
Vasomotor area of the medulla
Lateral: Excitatory
Medial: Inhibitory
What is the 1st line in maintaining blood pressure and buffers minute-to-minute changes in BP?
Baroreceptors (stretch receptors)
Where are the baroreceptors found?
Carotid sinus (respond to increase/decrease in pressure from 50-180 mmHg) Aortic arch (respond to increase in pressure >80mmHg)
Responds to low O2 or high CO2 concentration whenever BP is
Chemoreceptors
Where are the chemoreceptors found?
Carotid and aortic bodies
Low pressure receptors (cardiopulmonary receptors) detect fullness of vascular system. In response to increased intravascular volume, these 4 mechanisms are activated:
- Increase ANP (increase Na and H2O excretion)
- Decrease ADH (increase UO)
- Renal vasodilation (increase UO)
- Increase HR (Bainbridge reflex)
Differentiate Frank-Starling mechanism from Bainbridge reflex
Frank Starling: Increased VR –> Increase SV –> Increase CO
Bainbridge: Increased VR –> Increased HR –> Increase CO
The vasomotor center itself responds directly to ischemia during low BP; all systemic arterioles vasoconstrict severely except coronary and cerebral vessels
CNS ischemic response
Occurs in response to increased intracranial pressure
Cushing reaction or Cushing reflex
What is the triad of Cushing reflex?
Hypertension, Bradycardia, Irregular respirations
What is the mechanism of hypertension seen in Cushing reflex?
Activation of the CNS ischemic response causes massive vasoconstriction of all systemic arterioles
What is the mechanism of bradycardia seen in Cushing reflex?
Activation of the baroreceptor reflex due to the high BP activates the parasympathetic system to decrease HR
What is the mechanism of irregular respirations seen in Cushing reflex?
Compression of the brainstem where the respiratory centers are found
How long can the brain, heart and skeletal muscles last without O2?
Brain: 4 minutes
Heart and skeletal muscles: 6 hours
What is the normal net filtration?
2mL/min
Lymphatic system produces how much lymph per day?
2-3 L
What is the function of the lymphatic system?
Reabsorbs proteins and excess fluid back to the circulatory system
Special lymphatics used to absorb fat
Lacteals
Why should there be local control of blood flow?
For the tissues to get their proper amounts of oxygen and nutrients
For thermoregulation
For homeostasis
Organ with the highest blood flow under basal conditions:
Liver
Theory which states that when vascular smooth muscle are stretched, there’s a reflex contraction and vice versa
Myogenic theory
Theory which states that vasodilator metabolites are produced as a result of metabolic activity
Metabolic theory
Theory which states that certain substances increase blood flow during deoxygenation such as adenosine
Vasodilator theory
Theory which states O2 is needed during vascular muscle contraction, thus lack of O2 would lead to vasodilation
Oxygen lack theory
Theory which state that nutrients such as thiamine are needed for ATP formation thus vascular muscle contraction, thus lack of nutrients would lead to vasodilation
Nutrient lack theory
Increase in blood flow in response to brief period of decreased blood flow
Reactive hyperemia (blood flow increased 4-7x the normal)
Blood flow increases to meet increased metabolic demand
Active hyperemia
Most potent vasoconstrictor:
Vasopressin
Released as a result of blood vessel damage and causes arteriolar vasoconstriction; implicated in migraine
Serotonin
Released by damaged endothelium
Endothelin
Substance that causes platelet aggregation and vasoconstriction
Thromboxane A2
Counteracts the effects of TXA2
PGI2
Vasodilates upstream blood vessels
Nitric oxide (EDRF)
Causes arteriolar dilation and venous constriction leading to increased filtration (local edema)
Bradykinin and Histamine