Page 656 - Fundamentals of anatomy physiology

Figure 18–4 Effects of Intracellular Hormone Binding. Chapter 18 The Endocrine System 643

a Steroid hormones diffuse through the plasma membrane and b Thyroid hormones enter the cytoplasm and bind to receptors in
bind to receptors in the cytoplasm or nucleus. The complex the nucleus to activate specific genes. They also bind to
then binds to DNA in the nucleus, activating specific genes. receptors on mitochondria and accelerate ATP production.

1 1
Diffusion through
membrane lipids Transport across
plasma membrane
CYTOPLASM
Target cell response Target cell response
Alteration of cellular
structure or activity Increased Alteration of cellular
ATP structure or activity

production

6 Receptor 6

Translation and 2 Translation and
protein synthesis Binding of receptors protein synthesis
at mitochondria and
Receptor nucleus 18
2

Binding of hormone
to cytoplasmic or
nuclear receptors

5 5
Transcription and
Transcription and mRNA production
mRNA production
4
Receptor Gene activation

Receptor 4
Gene activation

Nuclear 3 3
pore
Binding of Binding of
Nuclear hormone –receptor hormone –receptor
envelope complex to DNA complex to DNA

pituitary gland, where they are released into the circula- anterior lobe control the activities of endocrine cells in the
tion. We introduced two of these hormones, antidiuretic thyroid, adrenal cortex, and reproductive organs.
hormone (ADH) and oxytocin (OXT), in Chapter 14.
3. The hypothalamus contains autonomic centers that exert
p. 504 direct neural control over the endocrine cells of the adrenal
medullae. When the sympathetic division is activated, the
2. The hypothalamus secretes regulatory hormones, spe- adrenal medullae release the hormones epinephrine (E)
cial hormones that control endocrine cells in the pituitary and norepinephrine (NE) into the bloodstream.
gland. The hypothalamic regulatory hormones control the
secretory activities of endocrine cells in the anterior lobe The hypothalamus secretes regulatory hormones and ADH
of the pituitary gland. In turn, the hormones from the in response to changes in the composition of the circulating