Lecture 18 - Autonomic Regulation

Question 1

What is the difference between Basal Tone & Resting Sympathetic Tone? In which case is resistance higher?

Answer 1

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

Question 2

Mechanisms that induce a change AWAY from basal arterial tone are called what? Mechanisms that induce a change back TOWARD basal arterial resistance are?

Answer 2

1. ACTIVE

2. Passive

Question 3

Withdrawing sympathetics results in what?

Answer 3

Passive Vasodilation

Question 4

What is the affect of sympathetic CHOLINERGICS? (muscarinic) What occurs when this is removed?

Answer 4

ACTIVE vasodilation

• passive vasoconstriction

Question 5

What are 3 effects of Sympathetic cholinergics?

Answer 5

1. Piloerection
2. Sweat glands
3. Vascular Smooth muscle VASODILATION

Question 6

Name 3things that stimulate Adrenergic receptors:

Answer 6

1. Isoprotenerol
2. Norepinephrine
3. Epinephrine (hormone from adrenal cortex)

Question 7

What is the function of the following receptors:

1. Alpha
2. Beta -1 Cardiac
3. Beta - 2 cardiac
4. Beta - 2 - smooth muscle

Answer 7

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:
   VASODILATION

Question 8

What type of receptors are Sympathetic Cholinergic? What do they cause?

Answer 8

MUSCARINIC- post-ganglionic sympathetic fibers that release acetylcholine

VASODILATION
ex: sweat glands, piloerection, smooth muscle

Question 9

What are the affects of Parasympathetic Cholinergics on the heart?

Answer 9

VASODILATE:

1. Cerebral
2. VIscera - splanchnic, genitalia, blader, large bowel

• skeletal & cutaneous vessels not innervated

Question 10

What are two ways that the sympathetic system works to increase diastolic pressure? What is one way to increase systolic pressure?

Answer 10

1. Peripheral Vasoconstriction
2. increase HR
3. Increase CONTRACTILITY - systolic

Question 11

Where are baroreceptor and chemoreceptor nerve terminals located?

Answer 11

Carotid Sinus & Aortic Arch

Question 12

How do baroreceptors respond to changes in BP?

Answer 12

• they feel VASCULAR stretch (mechanoreceptors)

- increase firing of parasympathetics to decrease BP

Question 13

When does baroreceptor firing increase?

Answer 13

When there is an INCREASE in arterial pressure

& decrease firing when arterial pressure decreases

Question 14

What is stimulated & inhibited during decreased BP?

Answer 14

Sympathetics increased, parasympathetics inhibited

1. Vasoconstriction
2. HR
3. Contractility

Question 15

What counteracts an increase in Mean Arterial Pressure?

Decrease?

Answer 15

Bradycardia & Vasodilation

• Vasoconstriction, HR, Contractility

Question 16

Baroreceptors respond more to which of the two changes:

Phasic (Pulsatile) or COnstant (static) Changes in Pressure?

Answer 16

Phasic!

• activated in early systole at normal MAP
• fewer impulses during late systole when pressure is still high and changing less

Question 17

When are there more/fewer baroreceptor firing:

1. Early Systole
2. Late systole?

Answer 17

EARLY 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)

Question 18

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?

Answer 18

1. it DECREASES
   - less firing from Carotid sinus
2. SYSTEMIC ARTERIAL PRESSURE INCREASES
3. due to less inhibition of sympathetic activity!!!

Question 19

If you restore pulse pressure, how does the systemic MAP change & the frequency of sinus nerve discharge change?

Answer 19

1. MAP decreases to control

2. Frequency INCREASES

Question 20

How does the sensitivity of baroreceptors change during HYPERTENSION?

Answer 20

• become LESS SENSITIVE to high pressures (lower frequency nerve response & smaller decrease in MAP)
• but still sensitive to changes to BP

Question 21

When are chemoreceptors activated?

Answer 21

• low pO2
• high CO2
• low pH (acidic)
• mor involved with respiratory system than cardiovascular

Question 22

When do chemoreceptors play a role in the CARDIOVASCULAR system?

Answer 22

• during severe HYPOXIA

not to normal changes in pO2

Question 23

What response do chemoreceptors stimulate in sympathetic & parasympathetic systems?

Answer 23

1. Vasoconstriction

2. Bradycardia

Question 24

What does HYPOXIA induce in real life? WHY?

Answer 24

TACHYCARDIA!

• increase in ventilation acts = via stretch receptors in the lung to INHIBIT EFFERENT VAGAL activity

Question 25

Because ventilation INCREASES during hypoxia, what happens to the HR?

Answer 25

- INCREASES | - vagal activity is inhibited so HR increases

Question 26

What has the highest blood flow per gram of body? (BOARDS QUESTION)

Answer 26

Carotid Sinus - designed to sense oxygen in the blood

Question 27

As oxygen content decreases, which direction does the curve shift? Why?

Answer 27

RIGHT & Up - makes it more sensitive to drops in CO2 - so as oxygen content decreases the RESPONSE INCREASES

Question 28

What is the result of Hyperventilation & Hypoventilation?

Answer 28

1. Hyperventilation - blow off a lot of CO2 = ALKALOSIS | 2. Hypoventilation - a lot of CO2 remains: ACIDOSIS

Question 29

What happens as the system attempts to respond to acidosis due to a drop in O2?

Answer 29

(ischemic & acidic) 1.inhibit parasympathetics 2. Stimulate SYMPATHETICS - cause vasoconstriction to raise BP & bring more O2 to the ischemic area

Question 30

What happens to BP and HR during hypoxia?

Answer 30

1. BP increases 2. HR increases - sympathetics increased & parasympathetics inhibited because of the RESPIRATORY AFFECT (increased ventilation)

Question 31

What is the purpose of the Renin-Angiotensin-Aldosterone Mechanism?

Answer 31

Mitigate Dehydration | not hemorrhage because this is not due to an ACUTE change - hem. doesn't last long enough to activate this

Question 32

What does renin do?

Answer 32

Convert Angiotensinogen to Angiotensinogen I

Question 33

What does ACE do?

Answer 33

Angiotensinogen Converting Enzyme - Convert Angio. I to ANgio II

Question 34

What are the 3 actions that result with the production of Angiotensinogen II?

Answer 34

1. Vasoconstriction of Renal & Systemic vessels 2. ALDOSTERONE release - increase Na reabsorption (water follows) 3. Hypothalamus: increase thirst & secrete ADH - which increases permeability of collecting duct to reabsorb WATER as well

Question 35

What is the final result of the Renin-Angiotensin-Aldosterone pathway?

Answer 35

INCREASE IN BP & Blood volume - stimulated during hypovolemia (dehydration)

Question 36

Why is the Renin-Angiotensin-Aldosterone System stimulated during CHF? What is the TX to prevent this from happening?

Answer 36

- 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)

Question 37

What is the function of aldosterone? ADH?

Answer 37

Aldosterone - increase Na reabsorption which increases water uptake ADH: (anti-DIuretic Hormone) - makes the collecting duct more permeable and REABSORBS water