1. Unit Four: The Circulation
Chapter 18: Nervous Regulation of the Circulation, and Rapid Control of Arterial Pressure
Guyton and Hall, Textbook of Medical Physiology, 12 edition

2. Autonomic Nervous System
Sympathetic Nervous System
Sympathetic innervation of the blood vessels
Sympathetic nerve fibers to the heart
Sympathetic vasoconstrictor system
Parasympathetic Control of Heart Function

3. Autonomic Nervous System
Sympathetic Nervous System
Fig. 18.1

4. Autonomic Nervous System
Sympathetic Nervous System
Fig Sympathetic innervation of the systemic circulation

5. ANS (cont.)
Vasomotor Center in the Brain and its
Control of the Vasoconstrictor System
Located bilaterally in the reticular substance of
the medulla and lower third of the pons; contains
1. vasoconstrictor area
2. vasodilator area
3. sensory area

6. Fig. 18.3 Areas of the brain that play important roles in the nervous regulation
of the circulation. Dashed lines represent inhibitory pathways.

7. ANS (cont.)
Continuous partial constriction of the blood
vessels is normally caused by sympathetic
vasoconstriction (Fig. 18.4)
Control of heart activity by the vasomotor center
Control of the vasomotor center by higher nerve
centers (Fig. 18.3)
Norepinephrine-the vasoconstrictor substance

8. Fig. 18.4 Effect of total spinal anesthesia on the arterial pressure, showing marked decrease in
pressure resulting from loss of “vasomotor” tone

9. Role of the Nervous System in Rapid Control of Arterial Pressure
Most arterioles of the systemic circulation are
constricted
The veins are especially strongly constricted
The heart is directly stimulated by the ANS,
further enhancing cardiac pumping

10. Role of the Nervous System in Rapid Control of Arterial Pressure
Rapidity of Nervous Control of Arterial Pressure
Increase in arterial pressure during muscle exercise
and other types of stress
Reflex Mechanism for Maintaining Normal
Arterial Pressure
Baroreceptor Reflexes

11. Baroreceptor Reflexes
Physiological Anatomy and Innervation
Fig. 18.5

12. Baroreceptor Reflexes (cont.)
Response to Arterial Pressure
Fig. 18.6

13. Baroreceptor Reflexes (cont.)
Circulatory Reflex Initiated by Baroreceptors
Vasodilation of the veins and arterioles
Decreased heart rate and strength of contraction
Fig Typical carotid sinus reflex effect on aortic arterial pressure
by clamping both common carotid arteries

14. Baroreceptor Reflexes (cont.)
Functions of the Baroreceptors During Changes in
Body Posture
Pressure “Buffer” Function of the Baroreceptor
Control System

15. Baroreceptor Reflexes (cont.)
Fig Two hour records of arterial pressure in a normal
dog and in the same dog several weeks after the
baroreceptors have been denerved

16. Baroreceptor Reflexes (cont.)
Fig Frequency distribution curves of the arterial pressure
for a 24 hr period in a normal dog and in the same dog
several weeks after the baroreceptors have been denerved

17. Baroreceptors (cont.)
Control of Arterial Pressure by the Carotid and
Aortic Chemoreceptors
Effect of the lack of oxygen on arterial pressure
Atrial and Pulmonary Artery Reflexes Regulate
Arterial Pressure
Atrial Reflexes That Activate the Kidneys- the
volume reflex
Atrial Reflex Control of Heart Rate- the
Bainbridge Reflex

18. CNS Ischemic Response
Control of Arterial Pressure by the Brain’s
Vasomotor Center in Response to Diminished
Brain Blood Flow
Importance of the CNS ischemic response as a
regulator of arterial pressure
Cushing Reaction to increased pressure around
the brain

19. Nervous Control of Arterial Pressure
Abdominal Compression Reflex
Increased Cardiac Output and Arterial Pressure
Caused by Skeletal Muscle Contraction
During Exercise
Respiratory Waves in the Arterial Pressure
Arterial Pressure “Vasomotor” Waves
Oscillation of the baroreceptor and chemoreceptor
reflexes
b. Oscillation of the CNS ischemic response