Endocrine System
Overview
Functions of Hormones
O 1) Control, regulation, and maintenance of
a. Growth and development
b. Reproduction
O 2) Maintenance of internal environment
ie. Homeostasis
Hormones
O Cellular signals that signals to a cell to alter
its metabolism or function
Brain-Gut hormone connection
Two types of Hormones
O Peptide Hormones – hormones are composed of amino acids.
A peptide hormone binds to a cell-surface receptor, it does not enter
the cell.
Results: Enzymes are activate causing a chemical reaction
O Steroid Hormones – Steroid hormones enter the cell and bind to
receptors in the cytoplasm.
Ex. The hormone-receptor complex enters the nucleus where it
binds with chromatin and activates specific genes. Genes (DNA)
contain information to produce protein.
Results: When genes are active, protein is produced.
Peptide Hormones
O How Peptide Hormones Work
Steroid Hormone
How do hormones bind?
O Receptor- site on the surface or interior of a cell that binds
with substances such as hormones, antigens, drugs, or
neurotransmitters.
O Ligand- An ion or molecule that bind to another
chemical/molecule forming a complex with different
properties.
O Substrate- The substance acted upon by an enzyme.
O Enzyme- acts as a catalyst in living organisms, regulating the
rate at which chemical and biochemical reactions occur.
How hormones bind?
Types of Glands
Exocrine vs. Endocrine
O
Exocrine - A secretion deposited into a
body cavity through a duct
O
Endocrine – A secretion sent directly
into the bloodstream
Endocrine vs. Exocrine Glands
Ten Endocrine Glands
Types of feedback loops
Negative Feedback Loop- controls the rate of a
process to avoid accumulation of a product.
Positive Feedback Loop - occurs when the rate
of a process increases as the concentration of
the product increases ie. Will continue to
accelerate as long as substrate is available.
Menstrual cycle
Hormone Replacement
Therapy
O Hormone Replacement Therapy
Some physician’s are skeptical about efficiency of
using oral medications to replace hormones.
Mixed results
Experimental results are mixed and vary for the
individual, however many women had fewer
reproductive tract problems and decrease in
osteoporosis.
Concept Check
1. Since hormones travel through the
bloodstream why don’t all cells react?
2. What is the differences between positive
and negative feedback loops?
3. What is the difference in end result
between peptide and steroid hormones?