The document summarizes various reflexes and reflex actions related to the cardiovascular and respiratory systems. It describes the Valsalva maneuver and how intrathoracic pressure changes affect blood pressure and heart rate. It also discusses idiopathic orthostatic hypotension caused by autonomic defects, baroreceptor resetting in hypertension, and the effects of standing vs. lying down on blood pressure. Additional reflexes examined include the Bainbridge reflex related to low pressure receptors, the Bezold-Jarisch reflex causing bradycardia and hypotension, and the Cushing reflex increasing blood pressure during cerebral ischemia.

1. Author(s): Louis D’Alecy, 2009
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3. Other Reflexes and Reflex
Actions
M1 – Cardiovascular/Respiratory
Sequence
Louis D’Alecy, Ph.D.
Fall 2008
3

4. Wednesday 11/05/08, 10:00
Other Reflexes & Reflex Actions
22 slides, 50 minutes
1. Valsalva maneuver
2. Idiopathic Orthostatic Hypotension
• (autonomic nervous system defect)
3. Baroreceptor reset in hypertension
4. Gravity (standing)
5. Low pressure -volume (Bainbridge Reflex)
6. Cardioinhibitory (Bezold-Jarisch Reflex)
7. Cerebral ischemic (Cushing Reflex)
4

5. Valsalva Maneuver: forced expiration
against a closed glottis
Intrathorasic
Pressure
or
2 4
1 3
Source Undetermined
5

6. Valsalva Maneuver:
1 Increased MAP due to increased intrathorasic pressure(ITP)
2 MAP & PP decrease due to decreased VR
3 Baro-R increase in HR & VC (little effect)
STOP FORCED EXPIRATION
4 Decrease ITP, Increase VR &PP, Baro-R, decrease HR
6

7. Image of arterial
baroreceptor
removed
Please see: http://mor.phe.us/jtw/
Gateway/Projects/Vertebrates/
images/EvolutionOfTheHeart/
ArterialBaroreceptors.gif
McGraw-Hill
7

8. Hypertension resets baroreceptors to
Regulate pressure at a higher set point.
Frequency of
Action
Potentials
Source Undetermined
8

9. No Baro-Reflex
Source Undetermined
Idiopathic Orthostatic Hypotension (autonomic defect)
Deep anesthesia and over inflation of lungs
Restricts VR and decreases preload. 9

10. M&H Fig. 10.2
Pattern of pressures in recumbent individual
90 mmHg
Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
10

11. Pattern of pressures upon standing
No Baro-R
Hydrostatic YET !
column
Pooling
5 + 90= 95 In
veins
95 + 90=185
Mohrman and Heller. Cardiovascular Physiology. McGraw-
Hill, 2006. 6th ed.
11

12. VC
VC
Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
VC = vasoconstriction or
venoconstriction 12

13. One-way
valves
Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
13

14. Contraction of skeletal leg muscles
breaks the Hydrostatic Column
Leg muscles relaxed: Image of man’s Leg muscles
Pressure due to body with leg contracted: Pressure
muscles
gravity=80 mmHg contracted due to gravity=14
removed mmHg
14

15. M&H 10.2
Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
15

16. Bainbridge Reflex: Increase stretch of low pressure receptors
causes a reflex increase in heart rate and cardiac output.
Source Undetermined
In a normally hydrated
individual the “excess”
volume is sensed by
venous side low pressure
receptors and reflexly
increases HR
and CO (Bainbridge reflex)
favoring removal of excess
fluid on the arterial side by
renal mechanisms.
16

17. Arterial baroreceptor reflex: A increase stretch (pressure) causes
a reflex decrease in heart rate (negative chronotropic effect) .
Source Undetermined
In a dehydrated (patient)
individual the volume
replacement increases
CO and produces
increased
MAP and a reflex
bradycardia.
Used as test of “How
dry?”
17

18. Volume status determines the heart rate response to “volume expansion”.
“NORMAL”
“NORMAL”
Source Undetermined
18

19. Other Cardiovascular Reflexes
(Resetting of Set Point ? Pathophysiology ? )
Bezold-Jarisch Reflex
-respond to chemostimulation in myocardium
by veratrum alkaloids
-may be “pharmacological curiosity”
BUT
-***bradycardia with hypotension***
-over rides arterial baroreceptor reflex !!
-vagal afferents
-atropine blockable
-may have role in posterior-inferior infarcts
Anesthesiology 2003; 98:1250-1260
19

20. Other Cardiovascular Reflexes
(Resetting of Set Point ? )
Cushing (Cerebral Ischemic Reflex)
-response to compressive ischemia in CNS
-marked increase in arterial blood pressure
-over rides arterial baroreceptor reflex !!
-may involve central chemoreceptors
-presumed to be “protective” of ischemic CNS
20

21. When intracranial pressure approaches arterial
pressure the Cushing reflex produces a sustained
Increase in arterial blood pressure.
Cerebral Ischemic
Reflex
Normal CSF Pressure
Source Undetermined
21

22. If time permits
And not to be tested
Cardiovascular Response to Exercise
22

23. McGraw-Hill 23

24. Strenuous Exercise
Skeletal
Muscle
Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
M&H 10.4 24

25. 25
McGraw-Hill

26. Additional Source Information
for more information see: http://open.umich.edu/wiki/CitationPolicy
Slide 5: Source Undetermined
Slide 7: McGraw-Hill
Slide 8: Source Undetermined
Slide 9: Source Undetermined
Slide 10: Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
Slide 11: Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
Slide 12: Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
Slide 13: Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
Slide 15: Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
Slide 16: Source Undetermined
Slide 17: Source Undetermined
Slide 18: Source Undetermined
Slide 21: Source Undetermined
Slide 23: McGraw-Hill
Slide 24: Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
Slide 25: McGraw-Hill