Controls body functions by using chemicals that are made by endocrine cells.
A gland = is a group of cells that make special chemicals for your body
A hormone = is a chemical messenger made in one cell or tissue that causes a change in another cell or tissue in another part of the body.
• Chemical messengers
• Produced in endocrine glands
• Travel through blood
• Affect the target tissues
Types of Hormones
Composed of short chains of amino acids
B/C amino acids cannot freely diffuse across cell membranes, peptide hormones must be secreted through special vesicles and bind to specific receptors on the outside of the cell.
This causes a reaction that trigger the change of enzymes inside the cell.
Usually act fairly quickly
Exs: Insulin and ADH (anti-diuretic hormone)
Ring-shaped lipids made from cholesterol
Pass directly into cells because they are “hydrophobic”
Receptors for these hormones are on the inside of the cell
These hormone can affect the function of genes within the nucleus.
Act much more slowly b/c of this
Exs. Testosterone , estrogen and cortisol
Pass straight through the plasma membrane. Combine with a receptor molecule in the cell cytoplasm..
(b) Attachment to plasma membrane receptor
(c) stimulates a secondary messenger
(d) Secondary messenger alter the action of the cell.
Hormones Mode of Action
Small region of the brain.
It controls the release of hormones by the pituitary gland.
Considered to be a major link between the nervous system and the endocrine system.
(2) Pituitary Gland
Located at the base of the brain. Composed of two parts and called the “master gland” because it controls the activities of other glands.
Posterior pituitary is part of the Hypothalamus and does not secrete its own hormones. They are released by the storage facility in the posterior pituitary are:
Antidiuretic hormone (ADH) regulates the kidneys to reduce water loss in the urine.
Oxytocin stimulates uterine contraction during childbirth.
released after pregnancy, stimulates milk
production in females
2. Growth Hormone (GH)
This hormone controls the growth of the body by stimulating the elongation of bones .
3. Luteinizing Hormone (LH) triggers ovulation and the development of the “ corpus luteum” In females. In males it stimulates the release of testosterone by the testes. B. A nterior pituitary releases 6 major hormones
4. Follicle Stimulating Hormone (FSH)
Stimulates the activities of the ovaries and testes.
6. Adrenocorticotropin hormone (ACTH) stimulates the adrenal cortex to release corticoid hormones. 5. Thyroid Stimulating Hormone (TSH)
stimulates the thyroid to release thyroxine
How to remember the 6
Please Get Lunch For Their Aunt
(3) Thyroid Gland
Located in the neck below the larynx and in front of the trachea.
This gland secretes thyroxin which contains iodine.
Increases the rate at which you use energy = Metabolism
Secretion of thyroxin is regulated by TSH, which is secreted by the pituitary gland.
Regulates the rate of metabolism in the body and is essential for normal physical and mental development.
A person who suffers from hypothyroidism has a lower metabolic rate, which can cause obesity and sluggishness.
The opposite condition, known as hyperthyroidism, occurs when the thyroid produces too much thyroxine. It can lead to excessive perspiration, high body temperature, loss of weight, and a faster heart rate
Lack of iodine in the diet will lead to lack of thyroxin secretion. This produces enlargement of the thyroid gland and is called Goiter.
Goiter - is the result of iodine deficiency in the diet.
Goiter = an overly enlarged thyroid, due to a diet deficient in iodide
(4) Thymus Gland
Regulates the immune response, which helps your body fight disease
(5) Parathyroid Gland
Are tiny oval glands embedded in the walls of the thyroid gland.
Parathormone controls calcium metabolism.
Calcium is necessary for proper growth of teeth and bones, blood clotting, and nerve function.
(6) Adrenal Gland
Located on the top of each kidney.
Each gland consists of two layers:
Secrete steroid hormones that:
a) regulate water balance and blood pressure by controlling the reabsorption of sodium salt into the blood from the kidneys.
b) stimulate the conversion of fat and protein into glucose.
Secretes adrenalin .
Adrenalin increases the blood sugar level and accelerates the heart and breathing rate.
(7) Pancreas Islets of Langerhans
Both an exocrine gland and an endocrine gland.
The exocrine portion secretes digestive juices into the small intestine.
The endocrine portion consists of small clusters or “islands” of hormone-secreting cells called the Islets of Langerhans.
The Islet of Langerhans secrete insulin and glucagon.
Pancreas Islets of Langerhans
Facilitates the entrance of glucose into the cells.
Insulin lowers blood sugar levels by promoting the movement of sugar out of the blood and into the liver where it is stored as glycogen.
Stimulates the release of sugar from the liver and into the blood.
insulin lowers sugar level in blood
glucagon raises sugar level in blood
Diabetes Mellitus = disorder that inhibits cells from obtaining glucose
leads to dangerously high blood glucose levels
can lead to comas or even death
Type I ( hereditary autoimmune disease ) “childhood diabetes” which attacks Islets of Langerhans
Type II ( non-insulin dependent )
“ adult diabetes”due to low numbers of insulin receptors; often a result of obesity and inactivity
(8) Gonads Ovaries & Testes
Produce gametes and secrete
Ovaries produce estrogen and
Testes produce testosterone
Control sexual behavior and development
Estrogen helps maintain and develop female secondary sex characteristics, and stimulates the growth of the uterine lining for pregnancy.
Progesterone prepares the uterus for implantation.
Testosterone is necessary for sperm production and is responsible for secondary sex characteristics in males.
(9) Pineal Gland
Located in the brain, & secretes melatonin
Believed to be involved with daily biorhythms, such as sleep cycles
Possibly responsible for mood disorders, such as “ winter depression ” or “ seasonal affective disorder syndrome ”
How Hormones Work: Feedback Mechanism
Feedback mechanisms is a mechanism that maintain homeostasis .
A feedback mechanism occurs when the level of one substance influences the level of another substance or activity of another organ.
There are two types…
1. Negative Feedback
Is a type of self-regulation associated with endocrine regulation.
It operates on the principle that the level of one hormone in the blood stimulates or inhibits the production of another hormone.
Ex : TSH regulates the secretion of thyroxin by the thyroid gland.
Room temp. rises Thermostat Room Temperature Drops Signals Section 35-1 Examples of Feedback Inhibition Maintaining Homeostasis Negative feedback – your body’s response results in decreasing the effect of the stimulus (e.g. body temperature) Sensed by Heater to turn on
When a hormone is released, the increased levels of that hormone cause the body to send another chemical back to the cell that produced it to tell it make more
2. Positive Feedback
Positive feedback – your body’s response results in an increase in the effect of the stimulus, (example flight-fight response/or the greenhouse effect)
Body temperature first stimulates
TRF (thyrotropin-releasing factor) is a hormone released by the hypothalamus that passes to the anterior pituitary via the portal vein .
TSH (Thyroid stimulating Hormone) is a hormone produced by anterior pituitary which is carried to the thyroid gland at the base of the neck. This stimulated the release of thyroxin.
Thyroxin the final hormone is released into the blood and stimulates the metabolic rate of the cells
Blood Sugar Regulation
The pancreas is an endocrine gland which produces hormones which regulate blood glucose (sugar) levels
An increase in blood sugar level triggers the release of the hormone insulin by the pancreas
The hormone insulin lowers blood sugar level restoring the body to its original blood glucose level in two major ways :
It increases the ability of body cells to take in glucose from the blood.
It converts blood glucose to the compound glycogen -- this compound is also called animal starch and is stored in our liver and muscles.