1. January 26, 2016 Journal: What is the function of hormones?
***Hand in your journals when you are done.

2. Endocrine System

3. Endocrine System
Made up of glands that secrete hormones into the circulatory system
Hormones are chemical messengers that are either proteins or lipids

4. Functions: Controls rate of metabolism and tissue maturation
Regulates ion concentrations in the blood
Water balance in the blood
Controls the production of immune cells
Controls blood glucose levels
Controls the development and functions of the reproductive system

5. General Endocrine Pathway
Hormone is produced in small amounts by a gland
Secreted into the interstitial fluid
Enters the circulatory system where it is transported around the body
Acts on specific target cells by binding to specific receptors either on the cell membrane or inside cells

6. Amplitude-Modulated Signals
The concentration of hormones determines the strength of the signal and the magnitude of the response
Small concentration = weak signal = small response
Large concentration = stronger signal = larger response

7. Endocrine vs. Nervous System
Neurotransmitters
Hormones
Chemical Messenger
Released at chemical synapse
Released into bloodstream
Intended for close target
Travels to distant targets
Effect happens quickly
Effect takes time
Effect wears off quickly
Effect lasts longer
Affects single cell
Affects many cells

8. Control of Secretion Rate
Regulated through negative feedback loops in one of three ways
Humeral Control
Ex: Insulin secretion is controlled by blood glucose levels
Neural Control
Ex: Epinephrine is released from the adrenal gland because of nervous system stimulation
Hormonal Control
Ex: Thyroid-stimulating hormone is released from the pituitary gland and stimulates the release of thyroid hormone

9. Binding of Hormones by Target Cells
When a hormone comes in contact with a target cell, it binds to receptors at a binding site
Specificity: Each hormone must have specific shape and chemical make up to bind to each receptor
Cells that do not have the specific receptors for a hormone will not bind or respond to the hormone

10. Regulation of the Response
The number of functional receptors affects the amplitude of the cell’s response to a hormone
More receptors produce a larger response
Controlled through:
Down-regulation : reducing the number of functional receptors
Up-regulation: increasing the number of functional receptors

11. Effect of Drugs on Receptors
Drugs with similar structures to specific hormones may compete with those hormones for their receptors
Agonists: drug that binds to a hormone receptor and activates it
Antagonist: drug that binds to a hormone receptor and inhibits it