Regulation of arterial BP Flashcards
What are the anatomical components of the baroreceptor reflex?
The baroreceptors are a simple autonomic reflex loop including pressure receptors that monitor arterial pressure, an integrator and an effector pathway.
What is the sequence of events in the baroreflex that occur after a decrease in mean arterial pressure?
A drop in MAP will signal to the baroreceptors which signal to the afferent pathways to the medulla sending a signal to the efferent pathways effecting the heart and vessels to cause vasoconstriction to increase MAP
What are the high pressure (arterial baroreceptors)
They have exposed nerve endings located in the blood vessel walls in the carotid sinus and aortic
-carotid sinus receptros have a higher sensitivity
What are the cardiopulmonary receptors and what do they sense?
A receptors - sense atrial wall tension during contraction, report on hR
B reeptors - sense atrial stretch during filling; report on atrial volume
What occurs when the low pressure baroreceptors sense a drop in venous return?
Preload will drop therefore the brain will need to act to maintain preload and CO
Where is the chemoreceptors located?
Carotid force and arch of the aorta
How do baroreceptors initiate a signal to the brain?
Via the IX and X cranial nerves. This causes an AP taht are all or none. Thus rate or freq of AP is directly proportional to pressure
What are the two clusters of cells controlling HR, contractility and vessel tone?
Vasomotor center - activates vasoconstrictor and positive chronotropic/inotropic response (INHIBITORY SIGNALS)
Cardioinhibitory center - activates vagal outputs resulting in reducted heart rate (EXCITATORY INPUTS)
What are the various effectors?
Blood vessels, SA/AV nodes, myocardium, adrenal medulla
What is the effect of hypertension on the baroreceptor reflex?
Prolonged high BP –> NT depletion, recetor desensetization, –> Resets baroreceptors allowing for sensitivity over a higher range
What are the two main classes of humoral control?
Vasoactive substances and nonvasoactive substances
What is the purpose of vasoactive substances?
Affect vascular smooth muscle cell contraction and relaxation
What is the purpose of nonvasoactive substances?
Target organs outside the CV system
How does epinephrine affect the system?
Binds alpha1 causing vasoconstriction, and Beta2 causing vasodilation
What does serotonin do?
causes vasoconstriction
what does histamine do?
vasodilation
What does angII do?
potent vasoconstrictor - synthesis and release regulated by RAS
What is atrial natriuretic peptid?
a vasodilator released by atrial myocytes in repsonse to stretch
What does arginine vasopressin due?
AKA ADH, vasoconstrictor at high concentrations
What does ET cause?
Endothelins - vasoconstrictor
What is the RAS/RAAS?
Renin-angiotensin system or renin-angiotensin-aldosterone system
What happens when RAAS senses a decrease in pressure?
There is a signal via the SNS to release Renin which digests angiotensinagen, releasing angiotensin I then becomes ang II a potent vasoconstrictor
Which peptide regulates the synthesis and secretion of aldosterone?
Ang II
What is the role of AVP in regulating water volume and how mOSM and BP regulate ADH/AVP secretion?
AVP regulates how much water is retained by the kidney by stimulating renal collecting ducts to insert more H2o channels –> more water into the blood stream. AVP is synthesized in hypothalamus and rel from Post pit, the choroid plexus contains osmoreceptors which sense the osmolarity of the blood signaling release
How is Ang II formed?
Atrial myocytes synthesize and store ANP.
What stimulates release of ANP and what are the functions of ANp?
Stimulation for ANP release is myocardial stretch sensed by cardiopulmonary receptors.
Anp relaxes smooth muscle, relaxes arterioles to kidney, inhibits aldosterone secretion, inhibits NA reabsorption, inhibits secretion of ADH
What is the function of aldosterone?
Aldosterone - produced in glomerulosa
-released in response to increased Ang II, acts on distal tubules of kidney to retain water by absorbing Na back into the blood stream increasing blood volume
What is the function of NO?
More important regulators of CV function. Bradykinin and acetylecholine stimulate NO syn thase making NO from arginine. Short half life, activates a soluble cGMP inhibits MLCK and activates SERCA Ca++ pump, leading to vasodilation
What is the cliical relevance of NO?
Septic shock - bodywide huge drop in TPR and BP
Nitrates and angina - chest pain associated with myocardial ischemia
What is the effects of increases sympathetic activity on blood volume, CO and arterial pressure?
BV increases, CO increases, Arterial pressure increases
What is the effects of increased vagal activity on blood volume, CO and arterial pressure?
no change on BC, CO decreases, arterial pressure decreases
What is the effects of increased circulating epi on blood volume, CO and arterial pressure?
increased BV
increased co
either increase or decrease art pressure
What is the effects of increased Ang II on blood volume, CO and arterial pressure?
increased BV
increased CO
increased arterial pressure
What is the effects of increased aldosterone on blood volume, CO and arterial pressure?
increased BV
increased CO
increased arterial pressure
What is the effects of increased ANP on blood volume, CO and arterial pressure?
decreased blood vol
decreased CO
decreased arterial pressure
What is the effects of increased Arginine vasopressin on blood volume, CO and arterial pressure?
increased BV
increased CO
increased arterial pressure
