MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Ya.I. Fedoniuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

CHAPTER 5. BLOOD AND LYMPH CIRCULATION PROCESSES AND THEIR PATHOLOGY

PHYSIOLOGY OF BLOOD VESSELS

5. REGULATION OF BLOOD CIRCULATION

5.1. VASCULAR INNERVATION

Changes in vessel lumen diameter are governed by The Nervous system. There are two Types of Nerve fibers: vasodilators, which widen the vessels, and vasoconstrictors, which narrow them.

In 1852, Claude Bernard performed a classic experiment: he transected the sympathetic nerve in a rabbit's neck. This led to vasodilation on the operated side of the neck, evidenced by reddening and warming of the ear. When the nerve was stimulated, the ear became pale and cold. This established the vasoconstrictive action of sympathetic nerves and their role in increasing ARTERIAL Blood PRESSURE.

However, cerebral, Skeletal Muscle, and coronary vessels dilate under sympathetic nerve stimulation. In contrast to sympathetic nerves, parasympathetic nerve activity generally leads to vasodilation in most Blood Vessels. Stimulation of the peripheral ends of the Spinal Cord dorsal roots, which contain afferent sensory fibers, also results in vasodilation.



Last update: 08/08/2026

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