Endocrine System

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Chapter 14

• Endocrine System

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Outline

• Endocrine Glands
• Hypothalamus and Pituitary
• Posterior vs. Anterior
• Thyroid Gland
• Parathyroid Glands
• Adrenal Glands
• Pancreas
• Other Endocrine Glands
• Homeostasis

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Endocrine Glands

• Endocrine glands are ductless glands and tissues
  that secrete hormones directly into the
  bloodstream.
• Hormone secretion by an endocrine gland is often
  controlled by negative feedback.
• Actions of a hormone can also be controlled by
  the presence of an antagonistic hormone.

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Endocrine System
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Hypothalamus and Pituitary Gland

• Hypothalamus regulates the internal environment
  through the autonomic system.
• Also controls glandular secretions of the
  pituitary gland.

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Posterior Pituitary

• Posterior pituitary releases two hormones
  produced by the hypothalamus.
• Antidiuretic hormone (ADH).
• Causes water to be reabsorbed into kidney
  capillaries.
• Negative feedback control.
• Oxytocin.
• Causes uterine contraction during childbirth and
  milk letdown.
• Positive feedback control.

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Anterior Pituitary

• Hypothalamus controls the anterior pituitary by
  producing hypothalamic-releasing and
  -inhibiting hormones.
• Anterior pituitary also produces
• Thyroid Stimulating Hormone (TSH).
• Adrenocorticotropic Hormone (ACTH).
• Gonadotropic Hormones (FSH and LH).
• Prolactin (PRL).
• Growth Hormone (GH).

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Effects of Growth Hormone

• Growth hormone is produced in greater quantities
  during childhood and adolescence.
• Too little GH produced during childhood may lead
  to pituitary dwarfism.
• Too much GH produced during childhood may lead to
  giantism.
• Too much GH produced as an adult may lead to
  acromegaly.

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Thyroid Gland

• The thyroid gland actively acquires iodine to
  produce triiodothyronine and thyroxine.
• A diet lacking iodine cannot produce thyroid
  hormones, and the thyroid may enlarge resulting
  in a simple goiter.
• Cretinism may result if the thyroid fails to
  develop properly.

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Thyroid Gland

• Hypothyroidism in adults produces the condition
  of myxedema.
• Hyperthyroidism (Graves Disease) may cause an
  exophthalmic goiter to form due to an overactive
  thyroid.
• Blood calcium level is regulated in part by
  calcitonin.
• Hormone secreted by the thyroid gland when the
  blood calcium level rises.

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Parathyroid Glands

• Parathyroid hormone is produced by the
  parathyroid glands and causes the blood phosphate
  level to decrease and the blood calcium to
  increase.
• Antagonistic action of calcitonin and parathyroid
  hormone maintain blood calcium levels within
  normal limits.

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Adrenal Glands

• Each adrenal gland consists of an adrenal medulla
  and an adrenal cortex.
• Epinephrine and norepinephrine are produced by
  the adrenal medulla and rapidly bring about
  bodily changes when an individual reacts to an
  emergency.
• Mineralocorticoids regulate salt and water
  balance and glucocorticoids regulate metabolism.

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Malfunction of the Adrenal Cortex

• When the level of the adrenal cortex hormones is
  low due to hyposecretion, a person develops
  Addison disease.
• When the level is high due to hypersecretion, a
  person develops Cushing syndrome.

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Addison Disease and Cushing Syndrome
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Pancreas

• The pancreas is composed of two tissue types.
• Exocrine tissue produces and secretes digestive
  juices.
• Endocrine tissue, pancreatic islets, produces and
  secretes insulin and glucagon directly into the
  blood.
• Antagonistic.

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Diabetes Mellitus

• Diabetes mellitus is a hormonal disease in which
  liver cells and other body cells are unable to
  take up and/or metabolize glucose.
• Type I - Pancreas is not producing insulin.
• Type II - Pancreas produces insulin, but the
  liver and muscle cells do not respond in the
  normal fashion.

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Other Endocrine Glands

• Testes and Ovaries.
• The testes produce androgens (testosterone) and
  the ovaries produce estrogens and progesterone.
• Puberty.
• Secondary sexual characteristics.

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Other Endocrine Glands

• Thymus Gland.
• Secretes thymosins that aid in the
  differentiation of lymphocytes inside the lobules
  of the thymus.
• Pineal Gland.
• Secretes melatonin that is involved in regulating
  daily sleep-wake cycle.

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Hormones from Other Tissues

• Growth Factors.
• Stimulate cell division and mitosis.
• Prostaglandins.
• Chemical signals produced within cells from fatty
  acid.
• Act locally.

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Homeostasis

• Hypothalamus produces ADH and thus regulates
  blood water balance.
• Endocrine system controls secretion of
  epinephrine and norepinephrine and thus controls
  fight or flight responses.
• Controls blood calcium levels.
• Muscle contraction.
• Insulin encourages uptake of glucose by cells and
  storage of glucose as glycogen in the liver and
  muscles.

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Review

• Endocrine Glands
• Hypothalamus and Pituitary
• Posterior vs. Anterior
• Thyroid Gland
• Parathyroid Glands
• Adrenal Glands
• Pancreas
• Other Endocrine Glands
• Homeostasis

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