Endocrine SystemJordan S.Kelsey G.Jena P.Sam P.

Endocrine System•A network of glands that secrete hormones, which travel in the bloodstream and affect the functioning of target cells

Function•Work alongside the nervous system•Maintaining homeostasis throughout the body through feedback mechanisms

Endocrine vs. Exocrine Endocrine

• Secrete hormones into the internal environment• Diffuse into the

interstitial fluid into the bloodstream and act on target cells

Exocrine• Secrete fluids out

of the body• Ex: Sweat and

oils

Hormones•Most are steroids synthesized from cholesterol• Or they are amines, peptides, proteins or glycoproteins produced from amino acids, or non-steroid hormones• Stimulate changes in target cells

Steroid Hormones• Cannot dissolve in water but can in

lipid • Thus allowing them to enter through

the target cell membrane• Steroid bonds to a receptor and

triggers transcription of specific regions of DNA resulting in mRNA • Weakly bound to plasma• Released in large quantities near

their target cells

Steroid Hormone Diagram

Steroid Video • https://www.youtube.com/watch?v=CaMKuXKZ70g

Non-Steroid Hormones• Usually bind receptors in target cell

membranes• Activates adenylate cylase• Then catalyzes conversion of ATP to cAMP• cAMP promotes a series of reactions

leading to cellular changes linked with the hormones action• These hormones do not penetrate the cell

membrane into the nucleus as steroid hormones do

Non-Steroid Hormone Diagram

Secretion• Nervous system works to control

secretion within the endocrine system• Nerve impulse is transmitted through

the neuron• Reaches the glandular cells to secrete a

hormone into the bloodstream or to stop the hormone• Hormone responds to target cells • Has no effect on other cells

Location• Endocrine glands are located in:oBrainoThroatoUpper abdominal regionoPelvic Region

• Secrete hormones internally

Pituitary Gland

Anterior Posterior

• Antidiuretic hormone

• Oxytocin

Located at the base of the brain where the pituitary stalks connect it to the hypothalamus

• Growth hormone• Prolactin• Thyroid

Stimulating hormone

• Adrenocorticotropic hormone

• Follicle stimulating hormone

• Luteinizing hormone

Hypothalamus• Attached to the pituitary gland by the

pituitary stalk• In charge of releasing the nerve

impulses to the posterior pituitary which then signals the hormone release• Controls the secretion of the anterior

pituitary • Thyrotropic releasing hormone• Corticotropin releasing hormone

Thyroid Gland• Located just below the larynx on either side and in front of the trachea

• Thyroxine• Triodothyronine• Calcitonin

Adrenal Glands

Adrenal Medulla

• Epinephrine• Norepinephrine

Adrenal Cortex

• Aldosterone• Cortisol• Sex hormones

• Consists of 2 parts: adrenal medulla and the adrenal cortex• The adrenal glad is located

right above the kidneys

Reproductive Glands

Ovaries

• Estrogen• Progesterone

Testes• Testosterone

• 2 Main reproductive organs that secrete important hormones are the ovaries and testes• Located in the pelvic region of

the body

Pancreas•Digestive juice secreting exocrine gland •A hormone secreting endocrine gland located posterior to the stomach and behind the parietal peritoneum

•Glucagon• Insulin

Pineal Gland •Located deep between the cerebral hemispheres •Attaches to the upper portion of the thalamus

•Melatonin

Parathyroid•Usually 4 parathyroid glands•Located on the posterior surface of the thyroid gland•Parathyroid hormone(PTH)

Thymus•Lies in the mediastinum posterior to the sternum and between the lungs•Large in young kids but shrinks after puberty and with age

• Thymosins

Negative Feedback Systems

• A way of controlling hormone secretion• An endocrine gland or system controlling it senses the concentration of the hormone the gland secretes, a process the hormone controls, or an action the hormone has on the internal environment

Negative Feedback Mechanism Example

Diseases• Diabetes: person has high blood

glucose• Insulin production in inadequate or the body’s cells do not respond properly to insulin, or both

• Adrenocortical Carcinoma: rare disease in which malignant(cancer) cells form in the outer layer of the adrenal gland

Diseases Continued• Growth Disorders•body produces too much growth hormone, gigantism or acromegaly can occur•Too little growth hormone results a condition called growth hormone deficiency•Can cause children to grow more slowly than normal