Exam 3 Kirk L5: Mechanisms of Global Regulation

Question 1

Define the following terms

________ is a theorhetical reference point… the amount of vascular contraction found under resting conditions without neural or hormonal (extrinsic) influences

_______ is vascular constriction under resting conditions as a result of tonic SNS activity. Resistance is higher than basal tone due to the presence of tonically released NE

Answer 1

Basal tone is a theorhetical reference point… amount of vascular contraction found under conditions with no extrinsic influences

Resting sympathetic tone: vascular constriction under resting conditions as a result of tonic SNS activity (presence of tonically released NE increases resistance)

Question 2

In your resting sympathetic tone, your resistance is _____ than that of theorhetical basal tone.

Explain why

Answer 2

In resting sympathetic tone, your resistance is higher than that of theorhetical basal tone.

This is because NE gets released tonically, increasing pressure via vasoconstriction and therefore increases resistance

Question 3

Define what active mechanisms vs passive mechanism due to change your vascular resistance

Answer 3

Active mechanisms induce a change in vascular resistance away from basal tone

Passive mechanisms induce a change in vascular resistance back toward basal tone

Question 4

Where are the alpha receptors located and what do they cause?

WHere is beta 1 receptors?

Beta 2 receptors?

Answer 4

Alpha receptors are located on the vascular smooth muscle and cause vasoconstriction

Beta 1 is on cardiac muscle and increases HR and contractility

Beta 2 are located on smooth muscle and cause vasodilation

Question 5

What two types of blood vessels have little sympathetic vasoconstriction innervation?

Answer 5

Coronary (heart) and cerebral (brain) have very little sympathetic vasoconstrictor innervation.

Question 6

Parasympathetic NS innervates ______ within circulatory system

Answer 6

PSNS innervates very few blood vessles

mainly affects the heart

Question 7

What is the sympathetic cholinergic pathway important for with regards to exercise?

Answer 7

Sympathetic cholinergic pathway release ACh onto sweat glands of skin, inducing vasodilation

important to regulate temp while exercise

Question 8

Which receptors cause vasoconstriction in blood vessels?

Which receptors cause vasodilation in blood vessels?

Answer 8

Vasoconstriction of blood vessels : ALPHA 1 (alpha two but only a little)

Vasodilation of blood vessels: beta 2

Question 9

The baroreceptor is what kind of receptor?

Important for short term or long term?

Answer 9

Baroreceptor is a mechanoreceptor, it responds to changes in stretch

If it gets stretched, aka high bp it increases its firing

If it does not get stretched aka small bp, it decreases its firing

SHORT TERM

Question 10

Baroreceptor is a ____ feedback loop

Answer 10

Baroreceptor is a negative feedback loop

Question 11

Baroreceptors are located in which two places?

Answer 11

Baroreceptors in the aortic arch and the carotid sinus

Question 12

Carotid sinus gets ennervated with which cranial nerve

What about aortic arch?

Answer 12

Carotid sinus —> IX

aortic arch : X

Question 13

A decrease in arterial pressure stimulates ____ and inhibits _____

What happens to peripheral vessels?

What happens to HR?

WHat happens to contractility?

Answer 13

Decrease in arterial pressure stimulates activation of SNS and inhibits PSNS.

Peripheral vasoconstriction

Increase in HR

Increase in contractility

Question 14

Baroreceptors are more responsive to _____ pressures than to constant ____ pressures

Blood pressure threshold for baroreceptors is ___ mmHG

What happens if you have hypertension?

Answer 14

Baroreceptors more responsive to pulsatile/phasic pressures than static/constant pressures

threshold is 50 mmHg

Your baroreceptors adapt and raise the threshold

Question 15

The ____ is the primary mechanism responsible for long term regulation of BP

It is responsible for mitigating the effects of fluid loss, dehydration (NOT HEMMORHAGE)

Answer 15

RAAS system: long term regulation

Question 16

RAAS system:

____ is where low blood pressure is detected

Thus, stimulating ____ release.

That then converts ____ into _____

ACE then converts ____ to ______

____ is a powerful vasoconstrictor

Answer 16

RAAS:

Kidneys is where the low bp is detected

Thus stimulating renin release

Renin converts angiotensinogen to angiotensin I

ACE then converts angiotensin I to angiotensin II
Angiotensin II is a powerful vasoconstrictor

Question 17

RAAS system:

Angiotensin II is a strong vasoconstrictor.

Explain the ways it increases blood volume:

aldosterone

ADH

hypothalamus

Answer 17

Angiotension II Mechanisms:

• stimulates aldosterone release, causing kidneys to reabsorb water
• stimulates hypothalamus to release ADH, increasing kidneys ability to retain water
• Hypothalamus: increases thirst

Question 18

Explain why the RAAS system is bad news for CHF patients

How do physicians remedy this?

Answer 18

In CHF, decreased contractility will result in low blood pressure, stimulating the RAAS pathway

Chronic stimulation of this system relults in hypertension, increased afterload, fluid retension, edema

Responses are maladaptive

TREAT by giving an ACE inhibitor (decreases angiotensin II)

Question 19

There are chemoreceptors in the same place as baroreceptors (aortic arch and carotid sinus).

Explain what happens when you have low O2 and high PCo2 levels.

(Explain what happens in the “intrinsic cardiovascular response” vs the integrated response)

Answer 19

Low O2…. the baroreceptors will send a signal to the brain, sending a signal to the heart that causes them to slow down and conserve more O2 (GREEDY) so the intrinsic cardiovascular response is bradycardia and vasoconstriction

However, the integrated response involves the pulmonary system, and more spefically the medulla vagal control center (sends signal for lungs to ventilate faster, that increase in respiration causes an increase in HR

In real life, hypoxia causes tachycardia becayse the increase in ventilation acts via stretch receptors in the lung to centrally inhibit efferent vagal nerve activity