Endocrine System

By Debra Kuhn & Katrine Viscaya

What is the endocrine system?

• The word Endocrine derives from Greek origin• The endocrine system is the collection of

glands in which each gland secretes a different type of hormone that regulates:

• Metabolism • Growth & Development• Tissue Function• Sexual Function• Reproduction• Sleep & Mood • Ect.

What are hormones? What do they influence?

Hormones: They are substances secreted by endocrine glands into the internal environment.

Influences: They diffuse from the interstitial fluid into the bloodstream and then act on target cells. They regulate physical and chemical processes. They may act on several organs throughout the body.

Exocrine vs. EndocrineExocrine

• These glands secrete products into ducts that

open onto surfaces (outside environment)

• They have ducts to carry hormones

• Sub-classifications: Multicellular and Unicellular• Multicellular glands

include:• Holocrine Glands• Apocrine Glands• Merocrine Glands

Endocrine• Glands from this system

secrete their products into tissue or blood (Inside the Body).

• These glands are ductless• The response is slower

because hormones travel through blood

• The duration of the response in motion is

longer because kidneys filter blood.

What makes up the Endocrine System

• Hypothalamus• Pituitary Gland• Thyroid• Parathyroid• Adrenal Glands• Pineal Body• Reproductive (Ovaries and Testes)• Pancreas• Thymus

Regulation of Hormone Secretion

Every time a Hormone is secreted, it is due to Negative Feedback Mechanisms. These mechanisms include

1.1. The Hypothalamus: The Hypothalamus: The Hypothalamus regulates anterior pituitary glands release of hormones that tell other Endocrine glands to release their hormones.

2.2. The Nervous SystemThe Nervous System

3.3. The Changing level of substance in plasma: The Changing level of substance in plasma: Another group of glands responds directly to changes of the composition of the internal environment

Nervous System Explained

• The Nervous System stimulates some glands directly which then release hormones to the target cells that cause the action of hormone response.

Steroid vs. Non-steroidSteroid

• Soluable (Soluable to Lipids so they can diffuse into cells easily)

• The Steroid Hormone binds a specific Hormone Molecule which is the receptor for that Hormone

• Hormone Receptor Complex binds within the Nucleus to particular regions of the target cells DNA

• This activate Transcription • RNA molecules leave the Nucleus and enter cytoplasm• mRNA associate with Ribosomes to direct the synthesis

of specific proteins

Steroid Vs. Non-SteroidNon-Steroid

• A hormone binds its receptor• This hormone receptor complex activates a protein

called “G” Protein• The “G” Protein activates the enzyme Adenylate

Cyclase • Activated Adenylate Cyclase catalyses the

circularization if ATP in the Cytoplasm into cAMP• cAMP activates another set of enzymes called Protein

Kinases which transfer Phosphate group from the ATP to their substrate molecule

1. The Hypothalamus

• Location: Above the brain stem• Controls the release of the 8 major hormones• Controls body temperature, Food and Water

intake, hunger, thirst, sexual behavior, daily cycles in psychological state, and the meditation of emotional responses

2. Pituitary Gland

• Location: Beneath the Hypothalamus• “Master Gland” – Most important gland of the

Endocrine System• Hormone production• Divided into two parts (Anterior and

Posterior)• Controls secretion of Endorphins• Also controls Ovulation & Menstrual Cycle for

women

3. Thyroid Gland

• Location: Frontal part of Lower neck (Butterfly Shape)

• Produces Thyroxine & Triiodothyronine = controls rate of cell burning of food (energy)• Metabolism

• Helps kids/teens bone grow and develop• Develops the brain and nervous system in

kids

4. Parathyroid Gland

• Location: Attached to Thyroid • Releases Parathyroid Hormones =

regulates level of calcium in blood with help of calcitonin (produced in Thyroid)

5. Adrenal Gland (Two Parts)

Outer (Adrenal Cortex)

• Produces Corticosteroids = Regulates salt and water balance in the body, its response to stress, metabolism, immune system, and sexual development and function

Inner (Adrenal Medulla)

• Produces Catecholamines = (Adrenaline), this increases blood pressure and heart rate when the body experiences stress

Location: On top of each Kidney

6. Pineal Gland

• Location: Middle of the Brain• Secretes Melatonin = Regulates sleeping

Schedule (when you sleep at night and when you wake up in the morning)• Involved in daily biological cycles

7. Reproductive Glands

Males• Gonads are main

source of sex hormones

• Location: Testes in Scrotum

• Secrete hormones called androgen

Females• Gonads are main

source of sex hormones

• Location: Ovaries in the Pelvis

• Secrete hormones estrogen and progesterone

8. Thymus

• Location: Behind Sternum & Between lungs• This Gland is only active until puberty, and

after puberty it starts to shrink and is replaced by fat

• This gland stimulates the development of T cells =

• T cells are a type of white blood cells which helps protect the body from infection and viruses

9. The Pancreas

• Location: Behind the Stomach• Two main functions: • exocrine function - helps in

digestion • endocrine function - regulates

blood sugar

Hormones Released by Glands

Regulation of Hormone Secretion

• Hypothalamus regulates the anterior pituitary gland’s release of hormones that stimulate other glands to release.

• Nervous system stimulates some glands directly (i.e. the adrenal medulla which secretes hormones in response to sympathetic nerve impulses)

• Other glands respond directly to changes in the internal environment (i.e. blood glucose level so pancreas secretes insulin or glucagon)

Negative Feedback Mechanisms

Cycle:1. Stimulus (ex. Blood

Glucose)2. Receptors (ex. Beta

Cells)3. Control Center (Nerve

cells in Brain)4. Effector (Insulin)5. Response (Blood

Drops)

Diseases• Diabetes

• Body does not process glucose properly, due to lack of insulin or the body is not working effectively with the insulin

• Hypothyroidism• Thyroid gland doesn’t produce enough thyroid hormone,

which may cause many body functions to slow or shut down completely

• Hypoglycemia• Low blood glucose or low blood sugar, occurs when blood

glucose drops below normal. Typically happens as result to diabetes treatment because too much insulin is taken

• Hormones can also impact bones, in diseases such as osteoporosis and osteomalacia (rickets) in which bones soften