Regulation of circulatory system Flashcards
What is vascular tone?
The state of partial constriction.
What does the vascular tone establish?
A baseline of arteriolar resistance.
Of what is the vascular tone a net effect?
Of Arteriolar Vasodilation.
Arteriolar vasoconstriction.
What does the arteriolar vasodilation decrease?
Resistance.
What does the arteriolar vasodilation increase?
Blood flow through the vessel.
What does arteriole vasoconstriction increase?
Resistance.
What does arterioles vasoconstriction decrease?
Flow.
By what is arteriolar tone controlled?
By local/intrinsic controls and extrinsic controls.
What is vasoconstriction?
Increased contraction of circular smooth muscle in the arteriolar wall.
Where does vasoconstriction lead?
To increased resistance.
Decreased flow through the vessel.
Which factors cause vasoconstriction?
High myogenic activity. High oxygen. Low carbon dioxide. Low other metabolites. High endothelium. High sympathetic stimulation. Angiotensin 2. Cold.
What is vasodilation?
Decreased contraction of circular smooth muscle in the arteriolar wall.
Where does vasodilation lead?
To decreased resistance.
Increased flow through the vessel.
Which factors cause vasodilation?
Low myogenic activity. Low oxygen. High carbon dioxide. High other metabolites. High nitric oxide. Low sympathetic stimulation. Histamine release. Heat.
What are the local influences associated with increased metabolic activity/intrinsic control?
Decreased oxygen. Increased carbon dioxide. Increased acid. Increased K+. Increased osmolality. Adenosine release.
What does complementary action of precapillary sphincters and arterioles adjust?
Blood flow through a tissue.
Why does complementary action of precapillary sphincter and arterioles adjust blood flow through a tissue?
In response to changing metabolic needs.
In what is the extrinsic sympathetic control of arteriolar radius important?
In regulating blood pressure.
What does increased sympathetic activity produce?
Generalized arteriolar vasoconstriction.
Where does decreased sympathetic activity lead?
To generalized arteriolar vasodilation.
What do the changes in arteriolar resistance bring?
Changes in mean arterial pressure.
From where is NA released?
From sympathetic nerves.
What does NA released from sympathetic nerves cause?
Vasoconstriction.
What do skeletal and cardiac muscles have?
Local control mechanisms.
Why do skeletal and cardiac muscles have local control mechanisms?
To override sympathetic vasoconstriction during exercise.
Where is the cardiovascular control center?
In the medulla.
What does the cardiovascular control center in the medulla adjust?
Sympathetic output to the arterioles.
Which are the hormones that influence the blood pressure in the extrinsic control?
Adrenaline.
Noradrenaline.
Vasopressin.
Angiotensin 2.
What hormones are adrenaline and noradrenaline?
Adrenal medulla hormones.
What do adrenaline and noradrenaline hormones, influence?
Sympathetic tone.
In what are vasopressin and angiotensin 2 also important?
In controlling fluid balance.
What is the primary determinant of total peripheral resistance?
The adjustable arteriolar radius.
How many major categories of factors influence arteriolar radius?
2.
Which are the 2 major categories of factors that influence arteriolar radius?
- Local/intrinsic control.
2. Extrinsic control.
In what is intrinsic control important?
In matching blood flow through a tissue with the tissue’s metabolic needs.
By what is the intrinsic control mediated?
By local factors acting on the arteriolar smooth muscle.
In what is the extrinsic control important?
In regulating blood pressure.
By what is the extrinsic control mediated?
By sympathetic influence on arteriolar smooth muscle.
What do the venous valves prevent in their mechanical action?
Backflow of blood.
What is an example of a short term control measure?
The cardiac absorption effect from the empty atria.
What happens in the cardiac absorption effect from the empty atria?
The difference in pressure between the venae cavae and atria forces blood into fill the atria.
What does the action of the skeletal muscle pump increase?
Venous pressure.
What happens as we breathe in?
Our rib cage expands.
What does the rib cage increase, as it expands while we are breathing in?
The volume in our chest.
What does the expansion of our rib cage while we are breathing, decrease?
The pressure.
What effect does the decrease in pressure from expansion of our rib cage, while we are breathing, have?
The effect of increasing the pressure gradient between the chest and the rest of the body.
Why does the decreased pressure from our rib cage which expands while we are breathing, act?
To draw blood to the heart.
To what does the movement of interstitial fluid into the plasma contribute?
To the maintenance of the pressure.
What do longer term control measures include?
The actions of hormones.
What do hormones affect?
Kidney function.
Fluid retention = hold.
Through what must the vascular tone be achieved in order to maintain BP?
Through the physiological balance of vasoconstriction and vasodilation of arterioles.
How is the physiological balance of vasoconstriction and vasodilation of arterioles (vascular tone) achieved to maintain BP?
Through intrinsic/local and extrinsic/neuronal control of smooth muscle tone.
How is the venous return characterised?
Passive.
By what is the venous return driven?
By action of heart, lungs and skeletal muscle.
What do endothelial cells form?
A single cell layer.
What does the single cell layer formed by the endothelial cells, line?
All blood vessels.
What does the single cell layer formed by the endothelial cells regulate?
Exchanges between the blood stream and the surrounding tissues.
What do the signals from endothelial cells organize?
The growth and development of connective tissue cells.
What do the connective tissue cells form?
The surrounding layers of the blood-vessel wall.
What do endothelial cells prevent?
Coagulation = freeze.
What do endothelial cells control?
Blood flow.
Passage of proteins from blood into tissues.
What do endothelial cells inhibit?
Inflammation.
Where does the production of nitric oxide (NO) has a role?
In coagulation preventing.
Blood flow control.
Proteins passage from blood into tissues.
Inhibition of inflammation.
Of what is the insufficient NO production a major cause?
Of endothelial cell dysfunction.
Upon what does the basic mechanism involved in arteriole vasodilation rely?
Upon the production of NO.
How many enzymes utilise intracellular substrates to produce NO?
2.
Which are the 2 enzymes that utilise substrates to produce NO?
- Endothelium NOS.
2. Cytochrome P450 reductase.
Across where does NO diffuse?
Across the lipid bilayers.
Why does NO diffuse across the lipid bilayers?
To cause relaxation of the smooth muscle.
To what is the endothelium extremely sensitive?
To Ach.
From what do the flow-mediated endothelial calcium responses arise?
From the autocrine action of non-neuronal ACh.
By what id the non-neuronal ACh released?
By the endothelium.
What does the increase in the rate of blood flow stimulate?
The endothelial cells to release Ach.
To what does Ach bind, once released form the endothelial cells?
To its receptor on the plasma membrane.
What does the Ach binding to its receptors on the plasma membrane initiate?
A signal transduction cascade.
What does the signal transduction cascade caused by Ach binding to its receptors initiation, cause?
The production of inositol triphosphate.
What does inositol triphosphate trigger?
Calcium release from the endoplasmic reticulum.
Where does the calcium released from the endoplasmic reticulum bind?
To the protein calmodulin.
What does the protein calmodulin activate?
NOS.
What does NOS produce?
NO.
Where does NO diffuse?
To the smooth muscle cells.
What does the NO activate once it diffuses to the smooth muscle cell?
The enzyme guanylate cyclase.
What does the enzyme guanylate cyclase convert?
GTP –> cGMP.
What does the elevated cGMP activate?
PKG.
What does PKG phosphorylate?
myosin light chain phosphatase.
What does the myosin light chain phosphatase dephosphorylate?
Myosin.
Why does the myosin light chain phosphatase dephosphorylate myosin?
To cause relaxation.
On what does relaxation depend?
On an intact endothelium.
What does addition of Ach cause?
An increase in diameter.
What does Ach become in case of Ach removal?
A vasoconstrictor.
Why does Ach become a vasoconstrictor hen Ach is removed?
Because it can act directly on the smooth muscle cell.
Why does Ach become a vasoconstrictor to act directly on the smooth muscle cell?
To increase intracellular calcium.
To who is the Ach becoming a vasoconstrictor to act directly on the smooth muscle cell to increase intracellular calcium a major issue?
For people with artery disease and damaged endothelium.
By what is BP determined?
By the combined activity of many systems.
Of what is the vasculature diameter a balance?
Of vasorelaxant and constrictor inputs across the entire body.
What does the brain have?
Direct sympathetic and parasympathetic innervations to the vasculature and heart.
Why does the brain have direct sympathetic and parasympathetic innervations to the vasculature and heart?
To influence vessel diameter and heart rate and force.
What else does the brain release?
Vasopressin.
What is vasopressin?
A peptide hormone.
On what does vasopressin act?
On the kidney.
Why does vasopressin act on the kidney?
To increase water absorption.
To what are the kidneys essential?
To BP regulation.
Why are the kidneys essential to BP regulation?
Due to the constant monitoring of BP.
Production of aldosterone.
Of what is aldosterone part?
Of the very powerful vasoconstricting and retaining renin-aldosterone-angiotensin system.
By what is mean arterial pressure determined?
By cardiac output + total peripheral resistance.
By what is CO determined?
By heart rate + stroke volume.
By what are heart rate and stroke volume influenced?
By sympathetic activity.
By adrenaline level.
What does parasympathetic activity decrease?
Heart rate.
By what is ventricular stroke volume increased?
By increased EDV.
By what is EDV increased?
By elevated atrial pressure.
By what is an increase in atrial pressure caused?
By increased venous return.
By what is an increased venous return caused?
By increased venous pressure.
Increased blood volume.
What do angiotensin 2 and vasopressin increase?
Blood volume.
What does ANP decrease?
Blood volume.
By what is TPR determined?
By arteriole diameter.
By what is arteriole diameter determined?
By the balance of vasoconstrictor and vasodilator inputs.
What can vasoconstrictor and vasodilator inputs be in nature?
Extrinsic.
Intrinsic.
By what else is TPR determined?
By blood viscosity.
With is the blood viscosity altered?
With the level of haematocrit or RBC’s in the blood.
What do elevated RBCs increase?
Viscosity.
What system is the renin angiotensin aldosterone system?
A very powerful hormonal system.
What does the renin angiotensin aldosterone system provide?
Long term control of blood pressure.
For what is the renin angiotensin aldosterone system designed?
To respond when there is prolonged decrease in blood volume and/or osmolality.
What is osmolality?
The measure of solute concentration in the blood.
By what is Aof pressure sensed?
By baroreceptors in the carotid sinus.
By what else can the Aof pressure e activated?
By a decrease in the filtrate sodium chloride (NaCl) concentration.
By a decreased filtrate flow rate.
What does a decreased filtrate flow rate stimulate?
The macula densa in the nephron.
Why does the decreased filtrate flow rate stimulate the macula densa in the nephron?
To signal the adjacent juxtaglomerular cells –> release renin.
Where does renin act?
On the circulating peptide angiotensinogen.
By what is the circulating peptide angiotensinogen produced?
By the liver.
To what is the circulating peptide angiotensin converted?
To angiotensin 1.
To what is angiotensin 1 cleaved?
To angiotensin 2.
By what does angiotensin 1 cleave to angiotensin 2?
By ACE.
Where does ACE reside = κατοικεί?
On the apical/blood facing side of the epithelial cells in regions such as the lungs.
What are the actions of angiotensin 2 for?
To increase blood pressure.
What is an action of angiotensin 2 that increase blood pressure?
Action at the CNS.
Why does angiotensin 2 act at the CNS?
To increase sympathetic output.
To stimulate the posterior pituitary.
Why would angiotensin 2 stimulate the posterior pituitary?
To release ADH.
Where does ADH act?
At the collecting duct of nephrons.
Why does ADH act at the collecting duct of nephrons?
To increase water absorption.
How else can angiotensin 2 be characterised?
As a powerful vasoconstrictor.
What can angiotensin 2 as a powerful vasoconstrictor?
Increase arteriole constriction.
What else does ANG2 stimulate?
Release of aldosterone from the adrenal cortex.
Where does aldosterone act?
At the collecting duct.
Why does aldosterone act at the collecting duct?
To increase sodium absorption.
Why do vasopressin and aldosterone act in communication?
To elevate blood volume.
How can vasopressin and aldosterone elevate blood volume?
By increasing water and salt absorption.
What is endothelin?
A powerful vasoconstrictor of VSM.
By which factors is the release of endothelin stimulated?
By ANG2. ADH. Cytokines. Reactive oxygen specie. Shearing forces. --> acting on the vascular endothelium.
What does the release of endothelin cause?
The production of IP3.
Increased intracellular calcium release.
What do the production of IP3 and the increased intracellular calcium release cause?
The activation of clamodulin and myosin light chai kinase enzyme.
What does myosin light chain kinase enzyme phosphorylate?
Myosin.
What does myosin facilitate?
Myosin interaction with actin filaments.
Why does myosin interact with actin filaments?
To produce contractile activity.
Where do vasoconstrictor actions of endothelin happen?
In the guinea pig coronary artery in the presence and absence of the endothelial lining.
In what does the removal of the endothelium result?
In a stronger constrictor response to 10nM endothelin.
What does the stronger constrictor response to 10nM endothelin from the removal of endothelium highlight?
The potent actions of endothelium.
The effectiveness of the homeostatic actions of the endothelium.
What do the homeostatic actions of the endothelium release?
Basal levels of NO.
How are the affects of NO an endothelin on VSM tension and tone characterised?
Opposite effects.
What is the regulation of arterial BP?
A complex multi-system process.
What does the regulation of arterial BP process involve?
Acute and long-term regulators.
What is the RAAS system?
A hormone system.
What does the RAAS system regulate?
Blood pressure.
Fluid and electrolyte balance.
Systemic vascular resistance.
