T/F: Nervous control of blood flow is primarily autonomic control and is mostly parasympathetic, which controls circulation (vasoconstriction primarily)
False
What does the parasympathetic do to the heart?
decrease HR and slight decrease in contractility
Sympathetic innervate all vessels except:
Capillaries, precapillary sphincters, and some metarterioles
T/F: Innervation of small arteries and arterioles allow sympathetic nerves to increase vascular compliance
False
T/F: Large veins and the heart are sympathetically innervated
True
Neurons from this area excite preganglionic vasoconstricot neurons in the SNS; CNS ischemic response
Vasoconstrictor area
Neurons from this area project upward and inhibit the vasoconstrictor area
Vasodilator area
Which area receives signals from the circulatory system and output signals control vasodilator and vasoconstrictor areas?
Sensory area
T/F: Heart control has sympathetic control via the cardioinhibitory area and parasympathetic control via the vasoconstrictor area
False
T/F: Higher nervous system control can excite or inhibit the vasomotor area
True
How does the baroreceptor reflex work?
Senses changes in BP and sends signal to CNS which initiates appropriate response to maintain nearly constant BP
Baroreceptors maintain MAP within ___-____ mm Hg
85-100 mm Hg
T/F: Baroreceptor reflex maintains moment to moment control of BP and is not related to tissue needs, similar to autoregulation.
False
Where are the nerve endings of baroreceptors located?
Arterial wall, in aortic arch and carotid sinus
Which bundle of baroreceptor nerve endings are more important for BP regulation because they are more sensitive?
Carotid sinus receptor
T/F: Baroreceptor activation inhibits the vasomotor center
True
What is the effect of inhibiting the vasomotor center?
Brain reduces sympathetic outflow in order to bring BP down
What does it mean for baroreceptors to reset?
If BP goes up and stays up, baroreceptors will establish a new baseline and maintain this higher average BP
Describe the pathway of baroreceptor activation due to high BP
- High BP stimulates baroreceptors in carotid sinus/aortic arch
- Cardioinhibitry center stimulated
- Decrease sympathetic impulses to heart
- Decrease rate of vasomotor impulses (allows vasodilation)
- Decrease CO and R
- BP returns to normal range
Describe the pathway of baroreceptor activation due to low BP
- Low BP inhibits baroreceptor
- decreased impulse from baroreceptor = cardioacceleratory center activated
- Increase sympathetic impulses to heart
- Vasomotor fibers stimulated (causes vasoconstriction)
- Increase CO and R = return BP to normal
What is the chemoreceptor reflex?
Sensing O2 lac, CO2 excess, or H+ ion excess and stimulate vasomotor center
T/F: Cerebral ischemia or impaired lung function can activate the baroreceptor reflex mechanism
False
Where are peripheral chemoreceptors located?
Carotid and aortic bodies
Where are central chemoreceptors located?
Medullary neurons
T/F: Chemoreceptor drive is significantly increased in HTN
True
Chemoreceptors are not stimulated until P falls below _____ mm Hg
80 mm Hg
T/F: Chemoreceptor activation increases sympathetic activity
True
What is the CNS ischemic response?
Reduced cerebral BF causes CO2 buildup which stimulates vasomotor center, thereby increasing atrial P
T/F: CNS ischemic response is one of the most powerful activators of the sympathetic vasoconstrictor system
True
CNS ischemic response is activated when P falls below ______, with greatest activation at ____-_____ mm Hg
60; 15-20 mm Hg
What does α1 innervate?
- Vascular smooth muscle
- Heart
- Liver
- intestinal smooth muscle
What does α2 innervate?
- Vascular smooth muscle
- Brain
- Pancreatic cells
What does β1 innervate?
- Heart
- JG cells in kidney
What does β2 innervate?
- Skeletal muscle
- Vascular and bronchial smooth muscle
- Uterus, liver, GI, urinary tract, ocular smooth muscle
When is epinephrine or norepinephrine released?
During fight/flight response
How do α1 receptors respond to E or NE?
Primary vasoconstriction of blood vessels
How do α2 receptors respond to E or NE?
- Minor vasoconstriction of blood vessels
- Inhibition of NE release (brain)
- Inhibition of renin release (kidney)
How do β1 receptors respond to E or NE?
- Cardiac stimulation (positive chrono., dromo., inotropic)
- Renin release (kidney)
How do β2 receptors respond to E or NE?
Smooth muscle relaxation causing vasodilation and bronchodilation
T/F: β2 activation increases Ca2+ resulting in vasoconstriction
False
T/F: Both the SA node and the AV node contain β2 receptors
False
Increased rate of SA and AV node firing = positive ___________ effect
Chronotropic
Which adrenergic receptor protects the heart from free-radical mediated damage by compensating for lost β1 contractility?
α1
List vasoconstricting agents
- NE and E
- Angiotensin
- Vasopressin
- Endothelin
List vasodilator agents
- Bradykinin
- Serotonin
- Histamine
- Prostaglandins
- NO
Describe the mechanism of bradykinin-mediated vasodilation (via β2)
β2 on endothelial cells --> PLC --> IP3 --> ↑Ca --> ↑NO -->cGMP/PKG in SMC -->↑MLCP --> Relaxation
Alternatively: ↑Ca --> PLA -cox-> PGI2 --> IP receptor on vascular SMC --> cAMP/PKA --> ↓MLCK --> Relaxation
Increased P causing excretion of water is known as:
P diuresis
Increased P causing excretion of salt is known as:
P natriuresis
T/F: RAAS ↑ water and sodium retention and ↓ vasoconstriction
False
Ang II binds to ________ receptors on vascular SMCs, causing vasoconstriction
AT 1 (Gq)
How does Ang II affect NE release and reuptake?
Increases release, decreases reuptake
What are the main functions of vasopressin?
- Enhances water reabsorption via V2 receptor (Gq)
- Moderate vasoconstriction via V1 receptor (Gq) on SMCs
What are the main functions of Aldosterone?
- Mineralocorticoid
- Causes Na retention and K excretion from kidney