CVS Flashcards
What is the trajectory of AP in the heart?
Normally it starts in the SA node, then it is transmitted to the AV node where there is a delay(so ventricle can be filled) and then it spreads in the ventricles via purkinje fibers
What is phase 0 of the AP?
When fast Na channels open and there is depolarization
What is phase 1 of the AP?
When there is a brief repolarization due to efflux of K
What is phase 2 of the AP?
The plateau due to Ca influx and K outflux
What is phase 3 of the AP?
When there is repolarization due to closing of the Ca channels and K efflux
What is phase 4 of the AP?
The membrane resting potential, there is some K leakage
How does the sympathetic NS affect the heart?
It secretes norepinephrine that has positive ionotropic effect, it causes phosphorylation of Ca channels in the sarcolemma (increasing the Ca in IC, increasing force) and phospholamban (stimulates SERCA, causing quicker relaxation, increasing rate). also glycosides inhibit Na-K pump, increasing IC Ca
How does the parasympathetic NS affect the heart?
It releases acetylcholine that binds to muscarinic receptors and decreasing the influx of Ca and Na and increases K channels, decreasing rate and force
_____ Side of the heart is thinner
right
Frank starling law refers to:
the increased pressure in the heart causes higher output, and increase pressure depends on the venous return
What is preload and after load?
preload refers to the amount of blood in left ventricle in the end of diastole, and afterload is the amount of pressure that the heart needs to exert to eject the blood during ventricular contraction.
What is the first sound Lub ?
closing of the mitral valve in the left during ventricular systole (while the aortic valve is open)
What is the second sound dub?
The closing of the aortic valve during diastole of the ventricle (while the mitral valve opens to fill the left ventricle)
Why is the SA node the normal pacemaker?
because its resting membrane potential is unstable due to leaking of Na, causing spontaneous depolarization
Where does the plateau last longest?
in the ventricle
What are 4 unique characteristics of the SA node AP?
unstable resting membrane potential due to Na leakage, AP (phase 0) is caused by Ca influx, the AP has the shortest duration, there is no plateau or brief repolarization (phases 1 and 2)
What are the latent pacemakers?
AV node, AV bundle and purkinje fibers
What are the waves in an ECG?
P is the depolarization of the atria, then there is depolarization of the ventricles (QRS) (while atria repolarization is not shown) then there is repolarization of the ventricles (T)
Duration of P waves indicates:
conduction of the depolarization through the atria
Longer PR interval indicates:
Longer conduction time through AV node indicates slow transmission of impulses and first degree heart block
Longer QT interval indicates:
means longer time for repolarization that can lead to arrhythmias, is the time from ventricular depolarization to repolarization
A R-R interval of 0.8 give how many bpm?
1/0.8*60= 75bpm
What are the types of heart block?
First degree from longer PR interval, 2nd from AV node failure (P waves are slower than QRS), 3rd when AV node fails completely and latent pacemakers takeover (no correlation between P waves and QRS)
How are molecules absorbed in capilaries?
gases are soluble in lipid bilayer and cross by simple diffusion, water soluble substances go through water channels, glucose and aa are carried by facilitated diffusion, proteins and plasma proteins are too large and are retained in vascular compartments which causes resistance (called colloidal pressure)
What is acute control?
is short term control, caused by increase in CO2 and H or hihg temperature, when the availability of O2 is low there is vasodilation of arterioles and precapillary sphincters
How can endothelial cells regulate blood flow?
forming Nitric oxide that is a vasodilator to balance the vasoconstriction caused by angiotensin II, that stimulates NO. or producing endothelin that is a vasoconstrictor stimulated by injury
How do diuretic affect blood pressure?
they increase the excretion of urine and decrease absorption of Na and water, decreasing blood volume and pressure
What is humoral control?
secretion of antidiuretic hormone (ADH) AKA vasopressin, that is a vasoconstrictor secreted during hemorrage it increases water reabsorption to increase blood volume.
Or secretion of angiotensin I or II that is a powerful vasoconstrictor.
Or secretion of bradykinin and histamine that are vasodilators
How is angiotensin II formed?
Liver produces angiotensinogen that is converted to Angiotensin I by renin in the kidneys, then in the lungs there is the angiotensin converting enzyme (ACE) that converts it to angiotensin II
How does the sympathetic NS affects pressure?
Norepinephrine stimulates cardiac output and vasoconstriction (decreasing blood flow, increasing TPR)
What are baroreceptors?
Are mechanoreceptors that sense pressure in arteries, can cause inhibition or stimulation of sympathetic or parasymphatetic NS
Where are the hormones secreted from?
aldosterone is from adrenal cortex (increases Na and water absorption), angiotensins II production is stimulated by renin it is a vasoconstrictor. ADH is secreted by pituitary gland that responds to increase in osmolality or low pressure, also increases water reabsorption
What is the integrative system?
responses of the CVS to exercise, hemorrhage and posture
What are fast acting NS responses?
baroreceptor reflexes to increase pressure and response from sympathetic NS to increase pressure (constriction of arterioles and veins, heart rate)
What are NS responses that take minutes?
o Renin-angiostensin II constrictor mechanism
o Relaxation of vasculature
o Shifting of fluid in and out of capillaries
What is long term regulation?
Regulation of renal body fluid mechanism, low pressure causes secretion of aldosterone (vasoconstrictor) from adrenal cortex, it increases Na and water absorption to increase volume while angiotensin II constrict arterioles. Then the increase in pressure causes kidney to increase excretion of salt and water
What are CVS function during exercise?
increase sympathetic outflow, redirect blood where it is needed by constriction of some arterioles and splanchnic organs, vasoconstriction to increase TPR and venous return and decrease unstressed volume. Metabolites in skeletal muscle act as vasodilators
How is hemorrhage felt?
chemoreceptors in carotid and aortic bodies sense low PO2 and increase sympathetic outflow.
ADH is secreted (increase blood volume and vasoconstriction V1)
Person moving from lying to standing position causes
venous pooling from increased capillary pressure in veins of legs which increase filtration of fluid into interstitial fluid, resulting in loss of blood volume and decreased Pa
Standing for extended period causes
filtration of fluid out of the capillaries to exceed the capacity of the lymphatics to return fluid to circulation causing edema in lower extremities. Increased filtration decreases venous return and Pa, which may cause low blood pressure in brain and fainting
Renin angiotensin system regulate pressure when there is Increase in salt intake (increase pressure) by:
- reduce rate of secretion of Renin
- decrease angiotensin II formation
- decrease secretion of aldosterone
- decrease renal retention of salt and water and increase secretion in the urine
- until ECF and Pa are normal
Renin angiotensin system respond to low pressure by:
- Kidney releases renin, that acts on angiotensinogen to form angiotensin I, taht is converted to II in the lungs that causes vasoconstriction and increase absorption of salt and water by stimulating secretion of aldosterone
How does angiotensin II act on kidneys?
Angiotensin II acts directly on the kidneys by constricting the arterioles of the kidneys to increase the reabsorption of salt and water and decrease urine and acts indirectly on the kidneys by acting on adrenal cortex to secrete aldosterone that increase sodium reabsorption and increase ECF
Blood type O has both _________ and no _______
anti A and B agglutinins (antibodies), no agglutinogens (antigens) while AB is the opposite
norepinephrine responding receptor Alfa 1 adrenergic are in _____. Beta 1 receptors in _____.
veins, heart
decreasing venous compliance(decreasing unstressed volume) means
constriction of veins
