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1. What does endo- mean?2. What is a hormone?3. What does the word negative mean?4. What does the word diffusion mean?5. What is mitosis?6. What is an enzyme?7. What does a mRNA molecule do?
Bell Work
A variety of organs that help coordinate and direct cellular activity by using hormones.
A hormone is chemical substance that are secreted by cells into the extracellular fluids and regulate the metabolic activity of other cells in the body.
Because hormones are being used and they have to diffuse, the results of the endocrine system are much slower than the nervous system.
What is the endocrine system?
Steroids – hormones that are made from cholesterol that includes the sex hormones and adrenal cortex hormones
Amino acid-based molecules – nonsteroidal hormones that are derived from amino acids, which have a amino group (-NH2)and a carboxyl group (-COOH). They include proteins, peptides, and amines
Prostaglandins – made from highly active lipids found in the cells’ plasma membranes
Hormone Classifications
Reproduction Growth and development Mobilizing body defenses against stressors Maintaining electrolyte, water, and nutrient
balance of the blood Regulating cellular metabolism and energy
balance.
The major processes of hormones
Hormones only affect certain cells or organs that are called target cells or target organs.
They affect the target by altering its cellular activity
Facts of hormones
Change the permeability or electrical state of the cell membrane
Cause the synthesis of proteins or certain regulatory molecules
Activate or inactivate enzymes Stimulate mitosis
Typically, it will…
The hormone1. Diffuses through the membrane of the
target cell2. Then it enters the nucleus3. It binds to a specific receptor protein there4. Hormone-receptor complex then binds to
specific sites on the cell’s DNA5. This activates certain genes to transcribe
mRNA molecules6. mRNA is translated in the cytoplasm, which
results in the synthesis of a new protein
Lipid-soluble Mechanism Steps (used by steroids and thyroid hormones)
These are unable to enter the cell so, they must bind to receptors on the target cell’s plasma membrane and utilize a second-messenger system
Nonsteroidal hormones
The hormone binds to the membrane receptor
This sets off a series of reactions that activates an enzyme
The enzyme catalyzes a reaction that produces a second messenger molecule (Examples: cyclic adenine monophosphate or cAMP, G proteins, calcium ions)
These molecules start making the changes inside the cell that produce the desired effect.
Steps in this mechanism
Negative feedback – a stimulus triggers the release of hormones, but the presence of the hormone inhibits further release of more hormones
Types of stimulus◦ Hormonal – endocrine organs are stimulated by
other hormones◦ Humoral – endocrine organs are stimulated by
changing blood levels of certain ions and nutrients
◦ Neural - endocrine organs are stimulated by nerve fibers
So, what prompts the endocrine glands to release hormones?