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Endocrine system

The endocrine system is a system of organs and their hormones, used to regulate our metabolism.

Endocrine organs in one location secrete hormones directly into the blood.

Hormones are chemicals which act as a messenger.

When these hormones are received at some other part of the body, they have an effect there.

Here we see hormones being released from the brain reaching the adrenal glands (located in top of your kidneys)

Hypothalamus Pituitary ACTH Adrenal glands

image from HOPES Huntington’s Outreach Project, Stanford Univ

What are hormones made of?

There are several types

1. Peptide or Protein hormones

Amino acids into Proteins

2. Amine hormones: A modified form of tyrosine (an amino acid)

Amine hormone tyrosine to epinephrine

3. Steroid hormones: Made from modified cholesterol


Are steroid hormones safe?

Many students think that “steroids” are bad. That is incorrect. Steroids occur naturally in all animals and plants. They are absolutely necessary for the organism to survive.

What is bad is adding extra hormones, unless they are necessary for some specific medical reason. Taking added steroids without a specific reason indeed is dangerous.

Endocrine organs


Most organs have 2 or more jobs

For example, in the brain, the hypothalamus has both nervous and endocrine functions.


Example of a hormone system

Pituitary gland Adrenal gland Kidney Endocrine hormone

from Mar Vista Animal Medical Center, marvistavet.com


Learning Standards

Massachusetts Curriculum Framework

HS-LS1-1. Construct a model of transcription and translation to explain the roles of DNA and RNA that code for proteins that regulate and carry out essential functions of life… include enzymes (which speed up chemical reactions), structural proteins (which provide structure and enable movement), and hormones and receptors (which send and receive signals).

College Board Standards for College Success: Science

Objective LS.5.5. Nongenetic Information Transmission. Students understand that nongenetic transmission of information within and among organisms involves specialized molecules, cell structures and cell systems.

LSH-PE.5.5.1 Construct a model that represents the molecular communication that takes place between cells that are in direct cell-to-cell contact, and a model that represents the molecular communication among cells in which molecules are released from one cell
and target other cells in the vicinity of the emitting cell (e.g., neurotransmitters, local hormones, growth factors).

LSH-PE.5.5.2 Construct a model to describe the communication between distant cells (e.g., hormones, pheromones, chemotaxis) and the process by which molecular communication between distant cells leads to particular outcomes.

LSH-PE.5.5.5 Construct a representation of the interaction of the endocrine and nervous systems (e.g., hormones and electrochemical impulses) as they interact with other body systems to respond to a change in the environment.

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