Overview: Purpose, Basic Structures

• To coordinate body functions by facilitating communication between cells in response to environmental and cellular signals.

• Control development and growth (childhood and adolescence)
• Regulates blood pressure, heart rate
• Responds to danger, stress
• Regulates metabolism
• Helps fight infection
• Control human reproduction

• Group of cells that manufacture secretions
• 2 types of glandular secretions
• Exocrine – deposited into body cavities, surface of skin through ducts
• Endocrine – sent directly into bloodstream
• Coordinate body functions

• Intracellular communication
• Endocrine glands: respond to signals from the environment, other cells
• Signals vary…
• Environmental (gases, gravity, nutrients, sunlight, temp)
• Cellular (hormones) originate inside the body

• Almost any organ can produce endocrine secretions
• Endocrine system composed of 10 endocrine glands

• Secretions enter blood directly through capillaries
• Don’t direct secretions to any particular part of the body…
• Yet not every cell of the body responds to these secretions…

• Receptors!
• Special surface molecules (often proteins) that permit cell to detect various types of stimuli
• Cells with receptors sensitive to endocrine secretions are called target cells

• Genetically programmed to modify their metabolism when they detect a specific endocrine secretion.
• So…
Only target cells will respond to the particular secretion

1.
What glands comprise the endocrine system? What do they produce?
2.
Once endocrine secretions are released, where are they deposited? How does this differ from exocrine secretions?
3.
Endocrine secretions are what type of signals?

1.
What is the function of a ligand?
2.
How do hormones work?
3.
What is an effector?
4.
What is the function of carrier proteins?

• Ligand: general name for a group of chemicals that attach to receptors.
• Hormones are a type of ligand
• For a ligand to propagate a chemical change, it must have the proper shape to fit into the receptor
• When bound to the receptor it causes many chemical reactions within the cell.

• Hormones are released from a gland. They bind to a receptor either on the inside or the outside of the target cell depending on the location of the receptor.
• Activates one of several chemical reactions in the cell.
• Receptors that are on the surface of the cell
= surface receptor
• Receptors that are located within the cell = internal receptors

• The target cell—the cell a hormone attaches to initiate a biological change

To bring hormones that use internal receptors to the target cell
OR
Once inside the cell, to bring hormones to the receptor

1.
How are endocrine glands different from exocrine glands?
2.
How do endocrine secretions “know” where to go once they’re secreted?
3.
How are autocrine secretions different from paracrine secretions?
4.
Do endocrine secretions usually target cells that are close to the point of origin of the secretion or far from it?
5.
What type of feedback loop does the endocrine system “use” to control the body? Give an example of one.

• Exocrine: secretions are deposited into body cavities or onto the surface of the skin via ducts
• Endocrine: secretions are sent directly to the bloodstream

• Secretions travel to every part of the body, but only target cells
(cells with the correct receptor for the secretion) react.

• Autocrine: interact with the cells that created it. Cells control their own activity. They do not travel in the blood
• Paracrine: secretions travel short distances to target cells.
• Most important function: coordinate cells within an organ.
• Pheromones: leave the body and signal the cells of other organisms.

• Both—it depends on the function of the secretion.

• Negative feedback loop
• A signal that inhibits an endocrine gland by preventing further secretion of a particular hormone.
• Similar to temperature control in a building

• Signals a cell to alter its metabolism… but must be programmed to do so
• Hormones can be many things…
• Agonists – chemicals that act as hormones (phytoestrogens from food that act like certain hormones)
• Antagonists – chemicals that block the actions of hormones
• A.k.a. mimics/hormone disruptors

1.
What is the function of a hormone?
2.
What is an agonist? What is its function?
3.
What is an antagonist? What is its function?
4.
What are the two types of hormones? What are their functions?

• Peptide – biological molecule made of amino acid chains
(named for the peptide bond in proteins)
• Produced “on-demand”
• Signaled by internal/external cues
• Lipid – made from existing lipids in body, taken in through diet
• Body converts cholesterol to a particular hormone
• Can be interconverted, too

• 1  many amino acids (polypeptide)
• Effects usually rapid
• Often involved in immediate changes in metabolism, but some permanent
• Ex. Growth hormone
• Bind to surface receptors (can’t enter cell through membrane)
• Broken down by enzymes to prevent accumulation in blood
• Some taken in, where they bind to internal receptors

• Fluid regulation, sexual reproduction
• 2 types:
• Hormone-like lipids
• Single chain of fatty acids (ex. prostaglandins, a signaling hormone)
• Steroids
• More complex
• Specific signaling
• Not water soluble; carried via carrier molecules
• Can move across cell membrane easily, interacting w/ DNA
• Broken down by enzymes to prevent accumulation
• Can cause metabolic problems, cancer if levels too high

Hormone-like Lipids: single chain of fatty acid
• Prostaglandins
• Produced by any cell
• Immune system control and blood pressure regulation
Steroids: made from cholesterol molecules

1.
How many distinct endocrine glands are there?
2.
Which gland is the “master gland?”
3.
Describe the anatomy, and the location, of the pituitary gland.
4.
What are releasers and how do they function?
5.
How is the posterior pituitary controlled?
6.
Where is the pineal gland located, and what hormones does it produce?

7.
Describe the anatomy of the adrenal gland and name its parts.
8.
Describe the location and the function of the adrenal gland.
9.
Where is the thyroid located? How does it control metabolic rate?
10.
Is the pancreas an endocrine gland and/or an exocrine gland?
11.
Describe the cellular organization of the pancreas. What cells are responsible for the endocrine role of the pancreas? What endocrine secretions do these cells produce, and what is the purpose of those secretions?
12.
Where is the pancreas located?

13.
Where is the thymus gland? What does it secrete? What does the thymus gland control?
14.
What are gonads? What do they do?
15.
Identify the female gonads, their location, and what they produce.
16.
Identify the male gonads, their location, and what they produce.
17.
Describe the function of testosterone, estrogen, and progesterone.

“Master endocrine gland”
• Its hormones control most of the other endocrine glands
• intimately linked to the overall coordination of the body’s organ systems.
The pineal gland is responsible for producing melatonin and serotonin.

• Controlled by releasing hormones, produced by hypothalamus
• Responds to various signals from parts of the body
• External and internal
• Releasing hormones travel from
hypothalamus to anterior pituitary via capillaries

• Gets information from nerve cells of the hypothalamus
• Carry information from brain directly

• Small structure
• Above and behind hypothalamus
• Produces melatonin (regulates body rhythms)
• Related to day length, mood/depression (SAD)
• and serotonin
• Involved in appetite, emotions, mood, sleep

The adrenal glands are made up of an outer cortex and an inner
medulla.
The adrenal cortex produces
corticosteroids and androgens. The adrenal medulla produces
adrenaline and noradrenaline.

The pancreas produces hormones and digestive enzymes.
The thymus gland produces secretions that stimulate the immune system.
pancreas

Endocrine: Pathology of the Endocrine System
1. How would one know if the endocrine system is affected by disease?
Endocrine: Aging of the Endocrine System
1. What happens to hormones as a person ages?
2. What can people do to counteract the effects of an aging endocrine system?

• Disorders result from the overproduction or underproduction of one or more hormones.
• Not always a simple answer
• A decrease in hormone production might be due to an inability to detect signals, lack of signals, diminished blood flow to the gland, or diseased endocrine cells, or tumors.

Diabetes insipidus
Diabetes mellitus
Description
Inadequate production of antidiuretic hormone, caused by a malfunction of the posterior pituitary gland
Type I: Caused by decreased insulin production
Type II: Body’s inability to detect insulin signals
Can be caused by viral infections, high carbohydrate diets, and obesity
Effects
Produces extreme water loss resulting in frequent urination. The person has to drink a lot of water to prevent dehydration and to fight the constant feeling of thirst.
Results in high blood sugar and other disorders due to abnormal glucose levels.
Glycosylation –extra sugars stick to tissues and the immune system destroys them. Can lead to blindness, blood vessel destruction, and kidney failure

• Inflammation of thyroid gland due to elevated thyroid hormone production (hyperthyroidism)
• Caused by an autoimmune disease.
• Results:
• Elevated metabolic rate
• Feelings of nervousness or tension
• Feeling tired throughout the day

• Thyroid gland doesn’t produce enough thyroxine
• Children: genetic defect
• Adults: thyroid or pituitary gland malfunction
• Results
• Children: mental retardation and short stature
• Adults: lethargy, weight gain, dry hair and skin, sensitivity to cold

• 13 weeks of development
• Sex hormones assist in the formation of sex characteristics
• Puberty
• Sex hormones at highest levels
• Adults
• Taper off after age 30 in men and age 40 in women

• Children
• Growth hormone, insulin, and thyroxine are important in growth.
• Thymus starts out very small and grows until a person reaches puberty, then it becomes smaller & less active as a person ages.
• Highly sensitive to small amts of chemicals that act like sex hormones
• Causes defects in genitalia (males) and causes females to enter puberty sooner, may be more susceptible to breast cancer.
• If blood vessels are defective and prevent blood flow to a certain body part then that part may not reach normal size and function

• HRT-hormone replacement therapy
• Estrogen=most common
• Natural (phytoestrogens) or prescriptions
• Many physicians believe its difficult to regulate hormone levels using oral supplements.

• Decrease in size of endocrine glands and decrease in hormone production
• can be accelerated in people with cardiovascular problems and diabetes
• Diminished blood flow through capillaries
• Reduce atmospheric gases, hormones and nutrients needed for hormone production
• Uptake of nutrients
• Each gland ages individually