Week 8: Reflex control of circulation

Question 1

What results in the elimination of the sympathetic nerve activity?

Answer 1

drop in the mean aterial pressure

Question 2

Sympathetic nerves innervate what elements of the cardiovascular system?

Answer 2

• blood vessels
• heart

Question 3

Sympathetic nerves innervate which type of vessels?

Answer 3

• resistance vessels (arteries)
• capacitanec vessels (veins)

Question 4

What innervation does the heart recieve?

Answer 4

• sympathetic (SA, AV node + cardiac muscle)
• parasympathetic ( only SA and AV nodes)

Question 5

What is the pathway of the negative feedback regulation?

Answer 5

Setpoint → discriminator → forward signal → effector/s → regulated paramter → feedback signal

Question 6

What are the three different types of receptors?

Answer 6

1. high pressure receptors
2. low pressure receptors
3. chemoreceptors

Question 7

What are the high pressure receptors and where are they located?

Answer 7

baroreceptors

located in the carotid sinus and in the aorta

Question 8

Describe the baroreceptors in the carotid sinus

Answer 8

• predominantly elastic fibers (no collagen, no smooth muscle)
• sensitive to ↑ transmural pressure
• distention → stretch receptors

Question 9

What is the graph displaying the relationship between arterial pressure and sinus nerve activity? What is significant?

Answer 9

The slope is largest at normal physiological range therefore the firing rate is very susceptible to change.

Question 10

What is the major difference between the carotid baroreceptors and the aortic baroreceptors?

Answer 10

The dynamic range of the carotid baroreceptors is higher than the aoritc baroreceptors

Question 11

Explain the graph displaying that the receptor potential ch changes in response to the elevation of arterial blood pressure

Answer 11

Question 12

What are the receptor potential changes converted to?

Answer 12

action potential frequencies

Question 13

Explain the graph

Answer 13

if the carotid is clamped the pressure in the carotid sinus is reduced due to the lack of blood flow

Question 14

What is the graph representing the relationship between the isolated carotid sinus and systemic pressure?

Answer 14

Question 15

Schematic scheme of the feed back regulation in response to ↑ mean arterial pressure

Answer 15

Question 16

What is the response to sustained hyper tension in regards to the firing of the baroreceptors?

Answer 16

Question 17

Where are the signals “passed to” when the receptors receive a high pressure signal?

Answer 17

aortic baroreceptors → vagus nerve

carotid sinus baroreceptors → herings nerve → glossopharingeal nerve

Question 18

What makes up the cardioinhibitory area?

Answer 18

• dorsal motor nucleus of vagus (CN X)
• nucleus ambiguss (CN X and part of CN IX)

Question 19

What is the pressure response in upright position?

Answer 19

correcting reflex activated within seconds

• venomotor activity (heterometric heart regulation)
• increased heart rate
• vasoconstriction

Question 20

What is the pressure response when there is severe heamorhage?

Answer 20

• vasoconstriction
  
  • splanchnic area
  • kidney

Question 21

What is the pressure response when there is heart stress?

Answer 21

skin vasodilation

Question 22

What is the pressor response ?

Answer 22

the reduction of blood pressure in the high pressure system

Question 23

Arterial blood pressure is normally kept in a relatively narrow range, what happens in the absence of high pressure baroreceptors?

Answer 23

large fluctuations

Question 24

Where are baroreceptors in the low pressure system located? what do they do?

Answer 24

in the right atrium

sense primarily blood volume changes

Question 25

What is the end result of intravenous infusion?

Answer 25

intravenous infusion ↓ increased right atrial pressure ↓ atrial receptors stimulated ↓ bainbrige reflex ↓ **increased heart rate** **End result:** ↑ANP, ↓RAS does NOT cause vasoconstriction **dilates** renal arteries prevents "stall blood" in veins

Question 26

What happens in the situation of simultaneous pressure change in the arteries ?

Answer 26

vasoconstriction

Question 27

What happens to low pressure receptors during volume depletion?

Answer 27

(fill gap with ↓ atrial receptor activity)

Question 28

What happens during **inspiration**?

Answer 28

​1. ↑ tension of the right atrium "bainbridge like effect" 2. ↓ stroke volume 3. respiratory center activity ↑ tension of lung mechanoreceptors ↑ 3 composes the "crosstalk" (b/w respiratory and cardiac center)

Question 29

What happens during **sinus arrythmia**?

Answer 29

Question 30

What higher neural centers can modify medullary regulation?

Answer 30

motor cortex cingulate

Question 31

What role do **chemoreceptors** play?

Answer 31

**dedicated to the regulation of the respiration** stimulate respiratory center ↑ ventillatory drive

Question 32

Graph displaying the differencein sensitivities of **chemoreceptors** and **baroreceptors**

Answer 32

chemoreceptors operate only in times of emergency

Question 33

What are the two classifications of chemoreceptors?

Answer 33

1. central chemoreceptors (in medulla) 2. peripheral chemoreceptors (aortic bodies, carotid bodies)

Question 34

Draw the relation of intrinsic cardiovascular response to **hypoxia, acidosis, and hypercapnia**

Answer 34

Question 35

Draw the cardiovascular/ respiratory response to **hypoxia, acidosis, and hypercapnia**

Answer 35

Question 36

What is the **cushings reflex**?

Answer 36

↑ intracranial pressure causes ischemic response of the central baroreceptor area

Question 37

What does increaed intracranial pressure cause?

Answer 37

* strongly reduced blood flow in the medullary region * activation of the vasomotor mechanism and cardioinhibitory area (vagus) * bradycardia and very strong vasocontstriction "at any cost" * kidneys could even ceise urine production due to how intense the vasoconstriction is

Question 38

What happens in the Bezold-Jarish reflex?

Answer 38

the receptors in the left ventricular wall are effected (mechano and chemosensitive) * **bradycardia** and **hypotension** (↑ parasymp and ↓ symp vasomotor activity) * cardioprotective can be activated e.g in myocardial ischemia/ infarction

Question 39

What happens in moderate pain?

Answer 39

activation of vasomotor center ↑ heart rate and ↑ blood pressure

Question 40

What happens in the occurence of strong pain and visceral pain?

Answer 40

parasympathetic activation hypotension, bradycardia