• The sympathetic nervous system starts the fight-or-flight
stage. The adrenal medulla secretes epinephrine and nor-
epinephrine, which increase blood flow and mobilize energy
sources.
• Activity of the hypothalamus and pituitary gland continue
during the resistance stage by stimulating secretion of
cortisol, growth hormone, and thyroid hormones. These
hormones mobilize energy sources (glucose, fatty acids,
amino acids) that tissues can use to make ATP. Resistance can
be sustained for a long period of time to combat a stressor.
• The exhaustion stage occurs when resistance can no longer
combat the stressor and body reserves are depleted.
5
Aging Alters the Endocrine System 278
■ The size or secretions
of many endocrine
glands, as shown here,
diminish with aging.
■ Secretions of growth
hormone, thyroid
hormones, cortisol,
aldosterone, estrogen,
and progesterone all
decrease with aging.
Components of the endocrine
system • Figure 9.1
Pineal
Gland
Adrenal
Glands
Pancreas
Parathyroid
Glands
Pituitary
Gland
Thyroid
Gland
Ovary
Testes
• TSH, PTH, LH, and FSH secretions increase with aging.
• As a body ages, the pancreas secretes insulin more slowly,
and tissues take longer to respond to insulin.
Key Terms
acromegaly 260
• follicle 262
• osteoclast 264
Addison's disease 272
• follicular cell 262
• oxytocin 260
adrenal gland 269
• general adaptation syndrome 275
• pancreatic islets or islets of Langerhans 266
aldosterone 270
• gestational diabetes 268
• parafollicular cell 262
androgen 272
• gigantism 260
• parathyroid gland 264
anterior pituitary lobe 258
• glucagon 267
• parathyroid hormone (PTH) 264
antidiuretic hormone (ADH) 261
• glucocorticoid 271
• pineal 274
calcitonin 262
• gonadotropin-releasing hormone (GnRH) 273
• pinealocyte 274
calcitriol 264
• Graves disease 264
• pituitary dwarfism 260
congenital hypothyroidism 264
• hormone 255
• pituitary gland 258
cortex 269
• hormone receptor 255
• posterior pituitary lobe 258
cortisol 271
• hyperglycemia 267
• progesterone 272
Cushing's syndrome 272
• hyperthyroidism 264
• resistance stage 277
cyclic AMP (cAMP) 256
• hypoglycemia 267
• seasonal affective disorder (SAD) 274
diabetes insipidus 261
• hypothyroidism 264
• second messenger 256
diabetes mellitus 267
• insulin 267
• steroid hormone 255
endocrine gland 254
• medulla 269
• stress response 275
endocrine system 254
• melatonin 274
• target cell 255
epinephrine 272
• mineralocorticoid 270
• testosterone 272
estrogen 272
• myxedema 264
• thyrotropin-releasing hormone (TRH) 263
exhaustion stage 277
• neurosecretory cell 259
• thyroxine 262
exophthalmos 264
• nonsteroid hormone 255
• triiodothyronine 262
fight-or-flight stage 277
• norepinephrine 272
282 CHAPTER 9
The Endocrine System
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