A&P II Module 1: Endocrine System (Part 1, 2, 3) & Module 2: Blood (Part 1, 2)

Module 1: Endocrine System Part I

In-class Activity #1

• What are hormones?

  • Hormones are chemicals the body uses to communicate processes and functions to other organs

Overview of the Endocrine System

• The endocrine system works in conjunction with the nervous system to coordinate and integrate activities of body cells.

• Composed of multiple tissues, organs, and hormones.

• Endocrinology: The study of hormones and endocrine organs.

Learning Outcomes

1. Differentiate between hormonal and neural controls of body functioning.

2. Identify major endocrine organs and their locations.

3. Distinguish hormones, paracrines, and autocrines.

4. Explain chemical classification of hormones.

5. Describe major mechanisms of hormone action on target tissues.

6. Discuss the regulation of hormone release.

Nervous vs. Endocrine System

• Both systems transmit messages that yield body responses.

  • Nervous System: Utilizes chemical/electrical signals and primarily neurotransmitters for short distances, with quick response times targeting both internal and external environments.

  • Endocrine System: Uses chemical signals (hormones) that may travel long distances; responses can be slow.

Major Endocrine Organs and Glands

• Pineal gland

• Hypothalamus

• Pituitary gland

• Thyroid gland

• Parathyroid glands (located dorsal to thyroid gland)

• Thymus

• Adrenal glands

• Pancreas

• Gonads

  • Ovaries (female)

  • Testes (male)

• The endocrine system contains glands such as the pituitary, thyroid, parathyroid, adrenal, and pineal glands, all responsible for hormone production.

• The hypothalamus serves as a neuroendocrine organ producing and releasing hormones.

Types of Chemical Signaling

• Hormones: Long-distance signals; circulate in blood or lymph.

• Autocrines: Chemicals acting on the same cell that secretes them.

• Paracrines: Local chemicals affecting neighboring cells.

• Autocrines and paracrines are not classified as part of the endocrine system.

In-Class Activity #2 (Examples of Signaling Types)

1. TSH from the anterior pituitary stimulating thyroid hormone release?

   Endocrine signaling.

2. IL-1 from an endothelial cell binding to its own receptor?

   Autocrine signaling.

3. IL-1 from an endothelial cell interacting with a macrophage receptor?

   Paracrine signaling.

Chemical Classification of Hormones

• Hormones are classified into two main groups based on their chemical structure:

  1. Amino acid-derived hormones: Includes amines, peptides, or proteins.

  2. Lipid-derived hormones: Primarily steroids.

Pathways of Hormone Action

• Hormones circulate throughout the body but only affect target cells possessing specific receptors.

• Target cells: Tissues with receptors for a particular hormone.

Pathways of Hormone Action

1. Membrane Hormone Receptor Pathway (for water-soluble hormones):

   • Water-soluble hormones bind to membrane receptors, activating a G protein.

   • G protein activates adenylyl cyclase, converting ATP to cAMP.

   • cAMP activates protein kinases that phosphorylate proteins, altering cellular activity.

2. Intracellular Hormone Receptor Pathway (for lipid-soluble hormones):

   • Lipid-soluble hormones diffuse through the plasma membrane.

   • Hormone binds with a receptor in the cytoplasm, forming a receptor-hormone complex.

   • The complex enters the nucleus and triggers gene transcription, leading to protein synthesis that modifies cell activity.

Cell Membrane Hormone Receptor Pathway :

Intracellular Hormone Receptor :

In-class Activities #3

• What type of hormone uses the cell membrane receptor pathway?

  • Amino Acid Derived

Regulation of Hormone Secretion

• Hormone secretion is regulated by feedback loops:

  • Positive feedback loop: Presence of a hormone enhances further production of that hormone.

  

  • Negative feedback loop: Presence of a hormone inhibits further hormone production.

Take Home Points

1. The endocrine system comprises glands, organs, and tissues across the body.

2. It generates specific responses by releasing hormones that act on receptors of target cells.

3. Hormones are classified chemically as either amino acid-based or lipid-based.

4. Hormonal actions occur via two main pathways: cell membrane and intracellular hormone receptor pathways.

5. Hormone secretion follows feedback loops, which can be either positive or negative.

Module Assignment 1 (Part 1)

1. In your own words, define the endocrine system.

2. The body has 2 main ways of coordinating the activity of body cells. What are these 2 systems?

3. Compare and contrast the 2 systems that your body uses to coordinate the activity of body cells.
Please summarize the similarities and differences between these systems in your own words rather than replicating the table in the notes/book.

4. What is the major difference between an endocrine gland and an exocrine gland?

5. What are the 5 major endocrine glands in the body?

6. For each of the 5 endocrine glands, state the relative location of each gland using the
anatomical directional terms, superior and inferior.

7. TSH released by the anterior pituitary gland stimulates the release of thyroid hormone from the thyroid gland. Would this be endocrine signaling, autocrine signaling or paracrine signaling?

8. IL1 released by an endothelial cell binds to the IL1 receptor on the same endothelial cell. Would this be endocrine signaling, autocrine signaling or paracrine signaling?

9. IL1 released by an endothelial cell binds to the IL1 receptor on a macrophage. Would this be endocrine signaling, autocrine signaling or paracrine signaling?

10. What chemical classification would you use to describe the hormone estrogen?