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63 Cards in this Set
- Front
- Back
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In contrast to local regulation how can blood flow be regulated in a more global way?
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By humoral mechanisms - substances secreted or absorbed into body fluids.
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3 categories of humoral agent mechanisms:
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1. Endocrine
2. Autocrine 3. Paracrine |
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What is the general mechanism of humoral bloodflow regulators?
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1. Ligand carried in bloodstream
2. Ligand diffuses into ISF thru endothelial cells 3. Ligand binds receptor on vascular smooth muscle 4. Modifies G protein inside smooth muscle cell 5. Gprotein alters enzyme cascade to produce effect |
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What happens when Gprotein activates PLC?
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PLC acts to produce IP3 + DAG
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What does DAG do?
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Activates PKC - protein kinase C which stimulates smooth muscle contraction.
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What does IP3 do?
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Stimulates release of Calcium for smooth muscle contraction.
VASOCONSTRICTION |
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What can Gprotein activate other than PLC?
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PLA2
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What is the action of PLA2?
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VASODILATION
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What is Norepinephrine's effect on blood flow?
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It is a vasoconstrictor
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How does NE cause vasoconstriction?
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It binds a GPCR to stim Gq, which activates PLC to split DAG + IP3 to release calcium stores from SR and activate PKC
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What does calcium release from the SR accomplish?
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Activation of MLCK - constriction of blood vessels
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What inhibits MLCK?
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Epinephrine
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What does Nitric Oxide do?
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Vasodilates - inhibits constriction by inhibiting PMCA from allowing calcium influx.
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What is Endothelin 1?
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A hormone that affects vessels
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What are the 2 receptors for ET-1 and what happens when either is bound?
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ACBD
ETA receptor Constrict ETB receptor Dilate |
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How is ET-1 secretion regulated?
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By transcription of its genes - there are many stimulators and inhibitors.
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What types of molecules stimulate ET1 secretion?
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Constrictors
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What types of molecules inhibit ET-1 secretion?
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Dilators
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What is the main effect of endothelin?
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Constriction
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Where is norepinephrine made?
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In noradrenergic cells
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Where is epinephrine made?
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In adrenal medullary cells
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What are norepi/epi made from?
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Phe -> Tyrosine -> Dopa -> Dopamine -> NE -> Epi
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4 types of Adrenergic receptors:
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alpha1
alpha2 beta1 beta2 |
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How do you remember what binds what?
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ABEN
Alpha binds Norepi Beta binds Epi |
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Where are Alpha 1 adrenergic receptors?
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In vascular smooth muscle
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What happens when NE binds a1 receptors?
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Constriction
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Where are A2 receptors located?
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In Sympathetic nerve varicosities
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What happens when NE binds A2 receptors?
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These are autoreceptors - it inhibits NE release
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Where are B1 receptors located?
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Heart SA Node
Atrial/ventricular muscle AV node/Purkinje fibers |
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What happens when Epi binds B1 receptors?
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Increases HR, Contraction, Conduction, and Velocity
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Where are B2 receptors?
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Vascular smooth muscle
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What happens when Epi binds B2 receptors?
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Relaxation - opposite of NE on alpha1
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What are the 3 important enzymes of the RAS?
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-Renin
-Angiotensin Converting enzyme -Aminopeptidase |
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Where is Renin produced?
What does Renin do? |
In the kidney - it converts Antiotensinogen into Angiotensin I
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What does Angiotensin I do?
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Nothing
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What does Angiotensin converting enzyme do?
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Converts Angiotensin I into Angiotensin II - the main active protein here.
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How many amino acids are in AT2?
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8
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What is ACE?
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Another name for angiotensin II converting enzyme.
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What does AT2 bind?
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At1 receptors or AT2 receptors
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What happens when Angiotensin II binds AT1 receptors? AT2?
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AT1: vasoconstriction/angiogen.
AT2: vasodilates/vessel rarefact |
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What is the major function of Angiotensin II?
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A negative feedback controller of acute hemorrhage changes in arterial pressure.
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How does AT2 respond to an acute hemorrhage?
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As arterial pressure decreases from 100 to 40, the Kidney releases Renin; AT2 is produced to raise BP up to 80.
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What is the gain in the previous example?
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Gain = correction/error remain
Gain = -2.0 (40/20) |
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What are ACE inhibitors prescribed for?
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BP medicine
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What is an annoying side effect of ACE inhibitors and why?
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Coughing - because it prevents Bradykinin break down and Bradykinin induces coughing.
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What is Vasopressin?
Where is it made/produced? |
ADH - a potent vasocontrictor.
Made in hypothalamus, released from posterior pituitary. |
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What is the main role of Vasopressin?
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Renal function controller - antidiuretic so it makes you retain salt - sodium.
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What acts oppositely to ADH?
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ANP - atrial natiuretic peptide
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How do you know ANP makes you excrete sodium?
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Because its name tells you thats what it does.
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How does ANP affect blood pressure?
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It lowers it.
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How do ADH and RAS affect BP?
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They raise it. Thats why you give ACE inhibitors.
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What is ANP approved to use to treat?
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Congestive heart failure
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3 Actions of ANP:
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-Natriuresis
-Reduces aldosterone secretion -Vasodilates |
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What ions/molecules cause constriction of blood vessels?
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-oxygen
-Calcium |
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What ions/molecules cause dilation of blood vessels?
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-CO2/H+
-K+ |
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Where is Angiotensin II made?
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In the brain and heart
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What does serotonin do?
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Vasodilates
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5 Humoral Vasoconstrictors:
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AVENT
Angiotensin II Vasopressin Endothelin Norepinephrine Thromboxanes |
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5 Humoral Vasodilators
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BEAPH
Bradykinin Epinephrine ANP Prostaglandin Histamine |
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1 Local vasoconstrictor
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Myogenic response
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7 Local vasodilators:
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-PO2 reduction
-Increased K, CO2, H+ -Osmolality -Nitric oxide -Adenosine |
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Neural vasoconstrictor
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Sympathetic nerves
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Neural vasodilator
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Neurons releasing NO
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