Cardiac - Peripheral Circulation Flashcards
WHat determines blood flow to the organs?
Arterial constriction and dilation
When radius doubles, volume flow…
increases 16-fold
What is the relationship between pressure, flow, and resistance?
Flow = (PA-PV)/R
What affect does autoregulation have on volume flow
It does not increase linearly like expected
What affect do metabolic by products have on blood flow?
They usually cause vasodiloation and increase blood flow
What affect does longer reduced blood flow on Reactive Hyperemia?
Longer RH
Increasing the longitudinal pressure gradient…
causes a difference in pressure between vessel ends
vasodilation
increased blood flow
What affect does rubbing have on vessels?
Before rubbing the endothielal layer is intack -> NE causes vasoconstriction and contraction -> ACh causes dose dependent vasodilation
After rubbing the endothelial layer is disrupted -> NE causes vasoconstriction and contraction -> ACh causes continued constraction becauses it binds directly to receptors on smooth muscle
Lack of endothelial cells on a vessel…
can turn a vasoconstrictor into qa vasodilater
ACh is a direct vaso…
vasoconstrictor
ACh is an indirect vaso…
vasodilator
How is a system able to monitor ESS?
Receptors on the surface of the endothelial cells can give info about ESS in environment
Receptors send information from surfac to nucleus
Vasodilators
Eisosanoids
ANP
Kinins
Adenosine
NO; EDHF
Histamine
Vasoconstrictors
Eisocanoids
Angiotensin II
Arginine Vasopressin
Endothelin
Adrenomedullary Hormones
What affect do vasodilators have on r^4?
increases 16-fold
What affect do vasoconstrictrs have on r^4?
Decrease
How are eicosanoid vasodilators and constricors created?
Arachadonic acid, found in all membranes, reacts with phospholipase to release arachadonic acid from cells -> free arachidonic acid acts on Cyclooxygenase and creates eicosanoids
What effects does NE have on heart cells?
Increases HR -> Increases contractility -> increases vasoconstriction -> increases resistance, pressure -> increases afterload
What affect does NE have on Alpha and Beta receptors?
Strongly activates Alpha1 and Beta1 receptors
activates Alpha2
and minimally effects Beta2
What affect does Epi have on Alpha and Beta receptors?
At high concentration in skeletal muscles it activates Alpha1
normally activates Alpha2
Strongly activates Beta1
At low cncentrations it activates Beta2
Alpha1 receptors in the arterials cause…
Vasoconstriction
Alpha2 receptors in the cardiovascular system inhibit…
NE released by SNS
What effect do Beta1 receptors have on the cardiovascular system?
Tachycardia
Icreased myocardial contractility
What affect do Beta2 receptors have on the cardiovasclar system?
Arterial vasodilation
How is angiotensin II formed?
Increase renin release from kidneys -> Renin cleaves Angiotensinogen -> creates Angiotensin I -> ACE converts Angiotensin I into Angiotensin II -> acts as a vasoconstrictor and regulates the release of aldosterone which regulates blood volume
Angiotensin II is a direct…
vasodilator
but is a potent vasoconstrictor
In high amounts, Angiotensin II __ the SNS
Enhances
How is Adenosince formed?
Metabolic acivity increases -> oxygen tension in tissues reduces -> ATP is hydrolyzed (decreases ATP) to ADP then to AMP -> AMP cant diffuse out of the cell -> 5’ Nucleotidase dephosphorylates AMP and catalyzes the hydrolysis of AMP to Adenosine -> Adenosine diffuses into interstitial space and causes vasodilation in arteriole -> blood flow increases -> oxygen delivery increases
Degree of constriction or dilation depends on…
the concentration of each present
What happens to the vasucular/arterial system when you decreaaes sympathetic innervation?
passive dlation -> increased HR -> decreases BP - SNS constricts to maintain BP
How do heart beats effect AP firing to the carotid sinus?
They stretch wit each beat
Increase __, decreases BP
What are the two parts of the baroeceptor relex?
Afferent and Efferent
What is the pathway of a barareceptor?
Baroreceptor -> Carotid Sinus Nerve -> Medulla -> Nerve groups that increase or decrease BP
What is the barorepctor response when you lose 2L of blood?
Reduced stretch in sensors -> decreased preload/EDV -> Decreases SV -> decreases stretch -> decreases firing of APs -> decreases inhibition -> increases SNS to SA node -> increases HR -> Increases SV -> Increases CO
Increases SNS -> increases NE -> binds alpha receptor -> constricts arterioles -> increases TPR -> Increases BP
Increases SNS -> increase NE -> venoconstriction -> decreased compliance -> increased pressure -> less blood stored in veins -> moves to active circulation -> eenhances veous return -> increases EDV/Preload -> Increases stretch -> increases SV -> increases CO -> increases BP
What happens when SNS is increased to the adrenalo medulla?
increase in EPI release
What happes whe SNS is increased to the kidneys?
Increased renin release -> increased angiotensin II - increased venoconstriction -> increases TPR
or increased angiotensin II promotes NA+ reabsorption and helps retain fluids
What do you want to do to increase BP?
Increase TPR and CO
What does increased firing in the medulla do to the SNS?
inhibits constriction of blood vesses and heart contractility
What does increased firing do in the PSNS?
Stimulates cardiac desecalation
What are baroreceptors important?
They sense BP and send signals out to the rest of the bodty
In response to a DECREASED in maBP the baroreceptor reflex mediates….
tachycardia and increased LVSV
Upon assuming an upright posture, afer lying quietly for severlal hours, the compensatory response of the baroreceptor control system regulation arterial BP involbes…
increased firing rate
Regional distribution of blood flow is primarily determined by…
arterial pressure and the radius of the arterioles supplying each organ (regulated by adjustment of vascular (arteriolar) resistances)
Flow to each organ can be based on…
Poiseuille’s law
the primary variable being vessel radius
Where does the greatest change in blood pressure occur in the circulatory system? Why?
In the arteriolar segment because it is the primary site of regulation of vascular resistance
Where does autoregulation usually occur? What influences it?
It can be influenced by neural and humoral factors
It is primarily intrinsic and occurs in denervated, isolated vasculature
What is the myogenic theory of autoregulation?
Distension or relaxaition of the smooth muscle in the vessel wall is the stimulus which regulates vessel radius
Mauy be related to the activation of membrane Ca2+ channels by increased TP
According to the myogenic hypothesis of autoregulation, what would increased perfusion pressure do?
Increased PP, Increases vessel wall stretch, stimulatres contraction, reduces flow
What is the metabolic theory of autoregulation?
Based on the observation that arterioles dilate and blood flow increases as metabolic activity increases
Why are endothelial cells important to the circulatory system?
Endothelial cells are necessary for ACh to relax the muscle
Endothelial cells are involved in ESS modulation of blood vessel diameter
The produce substances that can cause vasoconstriction or vasodilation
How do endothelial cells effect sheer stress?
When endothelium is intact, Vessel diameter increases as flow progressively increased
How do NE and EPI effect the circulatory system?
Activation of SNS releases NE and EPI into bloodstream - affect cardiac function when bound to B1 adrenergic receptors, cause vasodilation when bound to B2 adrenergic receptors, and cause vasoconstriction when bound to A1 receptors
What happens to adenosine when the oxygen supply is brought back into balance with metabolic demand?
Increased blood flow washes the adenosine from the IS -> adenosine can reenter the cell -> Adenosine Kinase rephosphorylates it into AMP or Adenosine Deaminase deaminates it to form isoeine
Adenosine can also diffuse into capillaries and leave the tissue by RBC
The regulation of the cardiovascular circulation is primarily under the control of the ___ division of the autonomic nervous system.
Sympathetic
Sympathetic fibers distributed to the lest side of the heart primarily affect…
The force of contraction (contractility)
Sympathetic fibers distributed to the right side of the heart primarily affect…
heart rate (SA Node)
What mediates the effect of NE on the heart?
B1-adrenergic receptors
What effect does parasympathetic srimulation have on the heart?
Reduces heart rate (negative chronotropic) and force of contraction (negative inotropic)
Negative chronotropic effect is more pronounced
Parasympathetic right vagus primarily innervates…
SA Node
Parasympathetic left vagues primarily innervates
AV Node
What mediates the effect of ACh on the heart?
Muscarinic receptors on cardiac cell membranes
Which system innervates the arterioles, areries, and veins?
Postganglionic Sympathetic
Which system innervates true capillaries?
None
What mediates the vasoconstrictor effects of NE on vascular smooth muscle cells?
A1 - adrengergic receptors
The degree of constriction caused by sympathetic innervation of vascular smooth muscle is…
proportional to the frquency of impulses (APs) conducted down the postganglionic sympathetic neuron and subsequent NE release
Parasympathetic innervation tends to ___ vascular resistance due to…
Decrease
ACh release
What causes venoconstriction?
Activation of SNS, release of NE, and binding of NE to A1 - adregergic receptors
What happens to cardiac output during venoconstriction?
Vessel Diameter and compliance decrease - blood volume decreases - Increase in venous return - increase in CO
How do baroreceptors function to effect blood pressure?
As the vessel walls stretch and condense the firing rate of APs to the sensory nerve changes alerting the body to begin sequences to raise or lower bp
What is the afferent baroreceptor pathway?
Afferent fibers from the carotid sinus make connections between the nucleus of tractus solitarius and the pressor/depressor regions of the medulla - increased firing in affernt nerves is caused by increased strtch (increased BP) in cartoid sinus - vasodilation of veins and arterioles - decreased HR and force of contraction - decreased BP
What is the baroreceptor reflex best suited for?
preventing rapid changes in BP
Efferent fibers from the pressor center are from the ___ nervous system supplying the heart and blood vessels
Sympathetic
Efferent fibers from the depressor center are from the ___ nervous system and are distributed to the heart
Parasympathetic
What is the relationship between pressor and depressor centers?
Reciprocal corss inhibition - Decreased pressor firing increases depressor firing
What is the function of cardiopulmonary receptors?
Activated by increased stretch - respond to changes in pressure or volume in atria and central venous pool - exert an inhibitory effect on SNS activity, and renin/vasopressin release
The primary cardiovascular effect of chemoreceptor stimulation is on…
the heart
What happens to heart rate if respiratory stimulation is mild?
Heart rate usually decreases
Carotid sinus massage is sometimes used to stop supra-ventricular tachycardia (rapid rhythms which originate above the ventricles). Which of the following is the most likely explanation for the effectiveness of this maneuver?
A. It increases sympathetic discharge to the SA Node
B. It decreases vagal discharge to the SA Node
C. It increases vagal discharge to the conducting tissue between the atria and the ventricles
D. It increases the refractory period of the ventricular myocardium
E. It reduces the conduction velocity around the reentry loop
C. It increases vagal discharge to the conducting tissue between the atria and the ventricles
Mitral valve stenosis would be associated with….
Elevated LA pressure and a diastolic murmur
The sino-atrial (SA) Node is the pacemaker for the heart because it:
has the highest rate of autonomic discharge
An increased afterload (i.e. increased aortic pressure) on the ventricle would be expected to have which of the following effects on the heart?
A. Increased HR
B. Decreased preload reserve
C. Decreased LVESV
D. Decreased LVEDV
E. All of the above
B. Decreased preload reserve
Which of the following is/are correct concerning the effect of catecholamines on myocardial cells?
A. They promote the phosphorylation of phosolamban, thereby enhancing the rate of relaxation of the myocardial cell
B. They inhibit the sarcolemmal NA-K pump resulting in a reduced Na-Ca exchange and an increased cystolic Ca concentration
C. They reduce the influx of extracellular Ca via voltage dependent Ca channels in the sarcolemma
D. They inhibit Ca reuptake into the SR resulting in an elevated cystolic Ca
E. two of the above
F. none of the above
A. They promote the phosphorylation of phosolamban, thereby enhancing the rate of relaxation of the myocardial cell
