CVS 2 Flashcards
Stress volume
The blood contained in arteries
Site of highest resistance in CVS
Arterioles
Have the largest ‘total’ cross-sectional and surface area
Capillaries
Formed from merged capillaries
Venules
Unstressed volume
The blood contained in veins
Contains the highest proportion of blood in CVS (? %) (reservoir function)
Veins; 65%
Percentage of blood that is cells
Hematocrit
Velocity is directly proportional to _______ and inversely proportional to _______
Blood flow; cross-sectional area
Turbulence is increased by ______ blood viscosity & ______ blood velocity
Decreased; increased
Describes the distensibility of the blood vessels
Capacitance (compliance)
Capacitance is _______ related to elastance or stiffness
Inversely
Poiseuille’s Law
R = (8 x viscosity x length) / (radius to the 4th x pie)
-10mmHg venous pressure poses high risk of?
VAE in Sagittal sinus
Atrial contraction.
Enlarged in pulmonary HTN
A wave
RV contraction (tricuspid valve bulging into atrium)
‘C’ wave
Increased atrial pressure d/t filling against closed tricuspid valve. Enlarged in tricuspid regurgitation.
‘V’ wave
Atrial relaxation + RV contraction (pulls atrium downward)
‘X’ descent
Emptying of right atrium after tricuspid valve opens
‘Y’ descent
Large wave not corresponding to a, v, or c wave. D/t complete heart block or junctional arrhythmias
Cannon wave
Important in transport of nutrients to tissues.
Site of wast product removal.
Blood flow through capillaries is regulated by contraction & relaxation of arterioles and precapillary sphincters
The microcirculation
Solute and water move across capillary wall via ________
Intercellular cleft (space b/w cells)
Most important means by which substances are transferred b/w plasma and interstitial fluid is by _______
Simple diffusion
Capillaries in the liver and intestines where the clefts are exceptionally wide and allow passage of protein
Sinusoids
2 major types of solid structures in interstitium are ______ & _______
Collagen fibers & proteoglycan filaments
Produced by endothelial cells & causes relaxation of vascular smooth muscles by cGMP such as nitric oxide
Endothelium-derived relaxing factor (EDRF)
ACh causes vasodilation by stimulating the production of _____ in vascular smooth muscles. Autoregulation
NO
Order for autoregulation
NO-dependent vasodilators on receptors > Ca > Nitric oxide synthase > L-arginine > NO > gaunylyl cyclase > GTP > cGMP > relaxation
What enzyme converts L-arg to NO?
Nitric oxide synthase
What is precursor of NO?
L-arg
How does NO act/ cause relaxation?
cGMP
Ability of a tissue to maintain blood flow relatively constant over a wide range of arterial pressures
Autoregulation
Factors determining autoregulation in Heart
Local metabolites, decreased O2, adenosine, NO
Factors determining autoregulation in Brain
Local metabolites, changes in CO2 (pH)
Factors determining autoregulation in kidneys
Myotonic and tubuloglomerular feedback
factors determining autoregulation in lungs
Hypoxia causes vasoconstriction
Factors determining autoregulation of skeletal muscle
Local metabolites, lactate, adenosine, K
An increase in blood flow to an organ that occurs after a period of occlusion of flow
Reactive hyperemia
BF to an organ is proportional to its metabolic activity (more blood flow to exercising muscles)
Active hyperemia
Vascular smooth muscle contracts when it is stretch is explained by ________ hypothesis
Myogenic
Tissue supply of O2 is matched to tissue demand for O2
Metabolic hypothesis
Degradation of ATP produces _________, a vasodilator substance that acts directly on vascular smooth muscle to increase intracellular cAMP and induce vasodilation
Adenosine
Histamine causes _______ dilation and _______ constriction > increased capillary hydrostatic pressure and increased filtration out of the capillaries, resulting in local edema
Arteriolar; venous
Causes arteriolar constriction; help to prevent blood loss. Implicated in the vascular spasm of migraine headache
Serotonin (5HT)
Prostacyclin is a _______ and thromboxane A2 is a ________
Vasodilator; vasoconstrictor
Where is the vasomotor center (VMC) located?
Bilaterally in reticular substance of medulla & lower third of pons
Hering’s nerve
Carotid sinus nerve
Responsible for the minute-to-minute regulation of arterial BP
Baroreceptor reflex
Steps in baroreceptor reflex
- Decrease in arterial pressure decreases stretch on the walls of the carotid sinus;
- Decrease stretch decreases firing rate of carotid sinus nerve (hering’s nerve/ CN IX) which stimulates VMC in brain;
- The VMC decreases parasympathetic (vagal) outflow to heart and increases sympathetic outflow
Valsalva maneuver MOA
Increases intrathoracic pressure which decreases venous return/CO/Pa > increase in HR.
Afterwards, rebound increase in venous return/ CO/ Pa > decrease in HR
Where is angiotensin I converted to angiotensin II?
Lungs
4 effects of Angiotensin II:
- Stimulates secretion of aldosterone by adrenal cortex (increases Na reabsorption);
- Increases Na-H exchange > contraction alkalosis;
- Increases thirst;
- Causes vasoconstriction of the arterioles
How does cerebral ischemia regulate arterial pressure?
When brain is ischemic the conc. of CO2 & H in brain tissue increase > chemoreceptor in VMC increases sympathetic flow > vasoconstriction
______ receptors respond to decrease in BP & cause release of ADH form _______
Atrial; posterior pituitary
2 effects of ADH:
V1 receptor- potent vasoconstrictor that increases TPR;
V2 receptor- increases water reabsorption by renal distal tubules & collecting ducts
ANP & BNP inhibit what?
Renin (causing increased excretion of Na & water and causes relaxation of vascular smooth muscle via cGMP)
Increase in atrial pressure increases HR.
Stretch of atria sends signals to VMC via vagal afferents to increase HR & contractility.
Prevents damming of blood in veins, atria, & pulm.
Bainbridge Reflex
_____ supplies the SA and AV node
RCA
CAD most common;y involves ______
LAD
Increased BP increased PCWP
Increased afterload & O2 consumption > increase depth of anesthesia to dilate & nitro
Ischemia with increased HR
Increased O2 consumption, decreased coronary BF. > beta blocker
Ischemia with decreased BP & decreased or normal PCWP
Decrease depth of anesthesia, FLUIDS, Neo
Ischemia with decreased BP increased PCWP
Heart is failing give inotropes (dopamine), NG (to decrease venous return), Neo (to increase BP and coronary perfusion)
Ischemia with normal hemodynamics
NG & CCB
