273

CHAPTER

18

Hypothalamic Regulation

of Hormonal Functions

OBJECTIVES

After reading this chapter you should be able to:

■

Describe the anatomic connections between the hypothalamus and the pituitary

gland and the functional significance of each connection.

■

List the factors that control water intake, and outline the way they exert their effects.

■

Describe the synthesis, processing, storage, and secretion of the hormones of the

posterior pituitary.

■

Discuss the effects of vasopressin, the receptors on which it acts, and how its secre-

tion is regulated.

■

Discuss the effects of oxytocin, the receptors on which it acts, and how its secretion

is regulated.

■

Name the hypophysiotropic hormones, and outline the effects that each has on

anterior pituitary function.

■

List the mechanisms by which heat is produced in and lost from the body, and

comment on the differences in temperature in the hypothalamus, rectum, oral

cavity, and skin.

■

List the temperature-regulating mechanisms, and describe the way in which they

are integrated under hypothalamic control to maintain normal body temperature.

■

Discuss the pathophysiology of fever.

INTRODUCTION

Many of the complex autonomic mechanisms that maintain the

chemical constancy and temperature of the internal environ-

ment are integrated in the hypothalamus. The hypothalamus

also functions with the limbic system as a unit that regulates

emotional and instinctual behavior.

HYPOTHALAMUS: ANATOMIC

CONSIDERATIONS

The hypothalamus (Figure 18–1) is the portion of the anterior
end of the diencephalon that lies below the hypothalamic sul-
cus and in front of the interpeduncular nuclei. It is divided
into a variety of nuclei and nuclear areas.

AFFERENT & EFFERENT CONNECTIONS

OF THE HYPOTHALAMUS

The principal afferent and efferent neural pathways to and

from the hypothalamus are mostly unmyelinated. Many con-

nect the hypothalamus to the limbic system. Important con-

nections also exist between the hypothalamus and nuclei in

the midbrain tegmentum, pons, and hindbrain.

Norepinephrine-secreting neurons with their cell bodies in

the hindbrain end in many different parts of the hypothalamus