The Endocrine System

1. The Endocrine System Chapter 18

2. Endocrine System • Endocrine cells: glandular secretory cells that release hormones • Hypothalamus • Pituitary Gland • Thyroid Gland • Thymus • Adrenal Gland • Pineal gland • Parathyroid gland • Heart • Kidney • Digestive • Pancreas • Gonads

3. Endocrine System • Styles of Communication • Gap Junctions • Direct communication; cell to cell of same type • Locations: Smooth muscle, cardiac muscle, neurons • Paracrine • Cells that are not in direct contact • Use chemicals known as paracrine factors to communicate • Cytokines or hormones (chemical messengers released in 1 tissue and transported to reach another specific tissue) • Enter the blood stream

4. Hormones • Hormones • Each have a target cell; specific cell that responds to its presence • Have special receptor binding proteins to “read” the hormone message • Each cell has certain binding proteins so they will not all react to each hormone • Use the bloodstream to travel • Nervous tissues uses these messengers with neurons won’t send the right message through a synapse • Often times share chemicals but differ by how they are used (remember what a neurotransmitter is)

5. Hormone Structure • 3 groups based off chemical structure • Amino Acid derivatives • Chemicals that are small, similar to aa structure • Ex: epinephrine, norepinephrine, dopamine, • Peptide hormones • All hormones secreted by the hypothalamus, posterior pituitary gland, heart, thymus, digestive tract, and pancreas. • Ex: growth hormone, prolactin • Lipid derivatives • Remain in the blood stream the longest • Help to coordinate cellular activites

6. Pituitary Gland • Small, oval gland that lies in a depression of the sphenoid bone • Hangs inferior to the hypothalamus and connected to the infundibulum • Divided into anterior/posterior regions • 9 important peptide hormones are released from this region • Filled with capillaries, direct transmission is possible

7. Hormones of the Pituitary Gland • Adrenocorticotropic Hormone (ACTH) • Affects glucose metabolism • Gonadotropins • Abnormally low amounts = lack of sexual maturation or ability to produce viable sperm/oocytes • Growth Hormone (GH) • Stimulates cell growth and replication of muscular and skeletal tissue • After the epiphyseal plate is sealed and GH is released causes abnormally large hands, feet, skull, jaw, etc. • At a young age, deficiency causes individual to have a short stature and larger-than-normal adipose reserve

8. Thyroid and Parathyroid Gland • Found the anterior surface of the trachea • 2 lobes • Parathyroid glands are embedded in the posterior surface of the thyroid • Extensive blood supply gives it the dark appearance

9. Effects of Hormones of the Thyroid Gland • Establishes rate of cellular metabolism • Hypothyroidism: inadequate production of hormones = inadequate skeletal and nervous development, metabolic rate 40% below normal • Hyperthyroidism: excess production of hormones = metabolic rate climbs, blood pressure/rate increases

10. Effects of Hormones of the Parathyroid • Regulates the concentration of calcium in body fluids • Hypoparathyroidism: prolonged muscle spasms because of less calcium concentration • Hyperparathyroidism: abnormally high amounts of calcium in body fluids causing brittle bons, weak skeletal muscles

11. The Adrenal Gland • Found the anterior surface of the trachea • 2 lobes • Parathyroid glands are embedded in the posterior surface of the thyroid • Extensive blood supply gives it the dark appearance