Flashcards in Lecture 18 - Autonomic Regulation Deck (37):
What is the difference between Basal Tone & Resting Sympathetic Tone? In which case is resistance higher?
Basal tone: amount of stimulation under RESTING conditions w/o extrinsic influences
Resting Sympathetic Tone:
- amount of vascular CONSTRICTION resulting to tonic sympathetic stimulation
- resistance is higher under RESTING SYMPATHETIC Tone due to tonically released NE
Mechanisms that induce a change AWAY from basal arterial tone are called what? Mechanisms that induce a change back TOWARD basal arterial resistance are?
Withdrawing sympathetics results in what?
What is the affect of sympathetic CHOLINERGICS? (muscarinic) What occurs when this is removed?
- passive vasoconstriction
What are 3 effects of Sympathetic cholinergics?
2. Sweat glands
3. Vascular Smooth muscle VASODILATION
Name 3things that stimulate Adrenergic receptors:
3. Epinephrine (hormone from adrenal cortex)
What is the function of the following receptors:
2. Beta -1 Cardiac
3. Beta - 2 cardiac
3. Beta - 2 - smooth muscle
1. VASOCONSTRICTION (except coronary & cerebral)
-on smooth muscle
2. HR & Contractility stimulated
- on cardiac muscle
3. Beta 2: secondary - HR & contractility
4. Beta 2 - Smooth muscle:
What type of receptors are Sympathetic Cholinergic? What do they cause?
MUSCARINIC- post-ganglionic sympathetic fibers that release acetylcholine
ex: sweat glands, piloerection, smooth muscle
What are the affects of Parasympathetic Cholinergics on the heart?
2. VIscera - splanchnic, genitalia, blader, large bowel
- skeletal & cutaneous vessels not innervated
What are two ways that the sympathetic system works to increase diastolic pressure? What is one way to increase systolic pressure?
1. Peripheral Vasoconstriction
2. increase HR
1. Increase CONTRACTILITY - systolic
Where are baroreceptor and chemoreceptor nerve terminals located?
Carotid Sinus & Aortic Arch
How do baroreceptors respond to changes in BP?
- they feel VASCULAR stretch (mechanoreceptors)
- increase firing of parasympathetics to decrease BP
When does baroreceptor firing increase?
When there is an INCREASE in arterial pressure
& decrease firing when arterial pressure decreases
What is stimulated & inhibited during decreased BP?
Sympathetics increased, parasympathetics inhibited
What counteracts an increase in Mean Arterial Pressure?
Bradycardia & Vasodilation
- Vasoconstriction, HR, Contractility
Baroreceptors respond more to which of the two changes:
Phasic (Pulsatile) or COnstant (static) Changes in Pressure?
- activated in early systole at normal MAP
- fewer impulses during late systole when pressure is still high and changing less
When are there more/fewer baroreceptor firing:
1. Early Systole
2. Late systole?
- there are fewer impulses during late systole because PRESSURE IS STILL HIGH & changing less
- when pressure falls during diastole, the receptors reduce firing rate even if pressure is above threshold
(RATE OF CHANGE MORE IMPORTANT THAN ABSOLUTE PRESSURE)
How does the neural activity recorded from carotid sinus change when the Pulse Pressure is DAMPENED & MAP is held constant? What happens to the MAP? WHY?
1. it DECREASES
- less firing from Carotid sinus
2. SYSTEMIC ARTERIAL PRESSURE INCREASES
3. due to less inhibition of sympathetic activity!!!
If you restore pulse pressure, how does the systemic MAP change & the frequency of sinus nerve discharge change?
1. MAP decreases to control
2. Frequency INCREASES
How does the sensitivity of baroreceptors change during HYPERTENSION?
- become LESS SENSITIVE to high pressures (lower frequency nerve response & smaller decrease in MAP)
- but still sensitive to changes to BP
When are chemoreceptors activated?
- low pO2
- low pH (acidic)
- mor involved with respiratory system than cardiovascular
When do chemoreceptors play a role in the CARDIOVASCULAR system?
- during severe HYPOXIA
(not to normal changes in pO2)
What response do chemoreceptors stimulate in sympathetic & parasympathetic systems?
What does HYPOXIA induce in real life? WHY?
- increase in ventilation acts = via stretch receptors in the lung to INHIBIT EFFERENT VAGAL activity
Because ventilation INCREASES during hypoxia, what happens to the HR?
- vagal activity is inhibited so HR increases
What has the highest blood flow per gram of body? (BOARDS QUESTION)
- designed to sense oxygen in the blood
As oxygen content decreases, which direction does the curve shift? Why?
RIGHT & Up
- makes it more sensitive to drops in CO2
- so as oxygen content decreases the RESPONSE INCREASES
What is the result of Hyperventilation & Hypoventilation?
1. Hyperventilation - blow off a lot of CO2 = ALKALOSIS
2. Hypoventilation - a lot of CO2 remains: ACIDOSIS
What happens as the system attempts to respond to acidosis due to a drop in O2?
(ischemic & acidic)
2. Stimulate SYMPATHETICS
- cause vasoconstriction
to raise BP & bring more O2 to the ischemic area
What happens to BP and HR during hypoxia?
1. BP increases
2. HR increases
- sympathetics increased & parasympathetics inhibited because of the RESPIRATORY AFFECT
What is the purpose of the Renin-Angiotensin-Aldosterone Mechanism?
(not hemorrhage because this is not due to an ACUTE change)
- hem. doesn't last long enough to activate this
What does renin do?
Convert Angiotensinogen to Angiotensinogen I
What does ACE do?
Angiotensinogen Converting Enzyme
- Convert Angio. I to ANgio II
What are the 3 actions that result with the production of Angiotensinogen II?
1. Vasoconstriction of Renal & Systemic vessels
2. ALDOSTERONE release
- increase Na reabsorption
3. Hypothalamus: increase thirst & secrete ADH
- which increases permeability of collecting duct to reabsorb WATER as well
What is the final result of the Renin-Angiotensin-Aldosterone pathway?
INCREASE IN BP & Blood volume
- stimulated during hypovolemia (dehydration)
Why is the Renin-Angiotensin-Aldosterone System stimulated during CHF? What is the TX to prevent this from happening?
- body senses decrease in cardiac output (heart is congested with blood)
SO it stimulates this pathway to increase Blood volume
- BAD: only worsens the issue
TX: ACE Inhibitors to lower blood volume
(also given for hypertension)