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Introduction
 The nervous system and endocrine system work together to
monitor and adjust physiological activities.
 In general, the nervous system performs short- term “crisis
management,” and the endocrine system regulates longer-term,
ongoing metabolic processes.
An Overview of the Endocrine System
 Endocrine system includes all of the endocrine cells and tissues of the
body.
 Endocrine cells are glandular secretory cells that release hormones.
 Hormones are organized into four groups based on chemical structure:
 Amino acid derivatives
 Peptide hormones
 Steroid hormones
 Eicosanoids
 Endocrine activity is controlled by endocrine reflexes that are triggered
by:
 Humoral stimuli
 Hormonal stimuli
 Neural stimuli
The Pituitary Gland
 The pituitary gland, or hypophysis
 Neurohypophysis (posterior lobe)
 ADH
 Oxytocin
 Adenohypophysis (anterior lobe)
 ACTH — adrenocorticotropic hormone
 TSH — thyroid-stimulating hormone
 GH — growth hormone
 PRL — prolactin
 FSH — follicle-stimulating hormone
 LH — luteinizing hormone
The Thyroid Gland
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Sits on thyroid cartilage of larynx
Butterfly-like appearance
Consists of two main lobes connected by the isthmus
Controls metabolism
Thyroxine (T4)
 Triiodothyronine (T3)
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 Involved in calcium homeostasis
 Calcitonin
The Parathyroid Glands
 Located on the back of the thyroid gland
 Two types of cells:
 Parathyroid cells, or principal cells— glandular cells that produce the hormone
PTH
 Oxyphil cells and transitional cells— likely immature or inactive principal cells
 Regulates calcium homeostasis
 PTH— parathyroid hormone
Located on top of the heart
 Secretes many chemicals that help T cells of the immune
system develop
 Thymosins
 Atrophies as one ages
The Suprarenal Glands
 Located on top of kidneys
 Manages stress levels
 Can be divided into two regions:
 Suprarenal cortex
 The Zona Glomerulosa produces mineralocorticoids.
 The Zona Fasciculata produces glucocorticoids.
 The Zona Reticularis produces androgens.
 Suprarenal medulla
 Chromaffin cells produce epinephrine (adrenaline) and norephinephrine
(noradrenaline).
Endocrine Functions of the Kidneys and Heart
 The kidneys
 Renin, an enzyme
 Erythropoietin, a peptide hormone
 Calcitriol, a steroid hormone
 The heart
 Atrial natriuretic peptide (ANP)
 Brain natriuretic peptide (BNP)
 Both produce hormones involved with the regulation of blood
pressure and blood volume
The Pancreas and Other Endocrine Tissues of the Digestive
System
 The Pancreas — located under stomach
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Alpha cells — glucagon
Beta cells — insulin
Delta cells — somatostatin (growth-hormone inhibiting hormone)
F cells — pancreatic polypeptide (PP)
 Other digestive hormones discussed in digestive chapter
Endocrine Tissues of the Reproductive System
 Testes
 Interstitial cells produce androgens (testosterone)
 Promotes production of functional sperms, maintains secretory glands,
influences secondary sexual characteristics, and stimultes muscle growth
 Nurse cells (or sustentabular cells) secrete inhibin
 Ovaries
 Follicular cells produce estrogens and secrete inhibin
 Corpus luteum releases progestins and relaxin
The Pineal Gland
 Part of the epithalamus
 Contains neurons, glial cells, and special secretary cells called
pinealocytes
 Pinealocytes synthesizes the hormone, melatonin
 Melatonin
 Slows the maturation of sperm, oocytes, and reproductive organs
 Production rate rises at night and declines during the day
Hormones and Aging
Exhibits relatively few changes with advancing age
One can expect
 The changes in reproduction hormone levels at puberty
 The decline in the concentration of reproductive hormones at
menopause in women
Clinical Note