ENDOCRINE SYSTEM

3 methods of communication - Direct - Cells have direct connections to other cells and can send messenger molecules - Alternatively cells can communicate with themselves (autocrine) - Paracrine - Signal is sent to nearby cells - Ex. Neurons communicating with each other via neurotransmitters. - Response to signal is typically very quick and short-term. - Endocrine - Hormones produced in glands communicate with cells throughout the body. - Response to hormones can be relatively slow, but long-lasting

Endocrine communication Two main types of hormone molecules Peptides Steroids Produced by glands which secrete them into the bloodstream

Peptide hormones Communicate with other cells by binding to receptors on the surface of the cell This initiates processes inside the cell Example: Insulin is a hormone Binds to surface of cells Causes glucose transporters to move to the plasma membrane Glucose is taken in by cells

Steroid Hormones Enter cells and find receptors inside target cells End result is a change in regulation of certain genes Remember genes are responsible for making proteins (the functional molecules in our cells) Slower response than peptide hormones Example: Testosterone Causes sex cells to differentiate into the male reproductive system during development

Hypothalamus The thalamus receives sensory information, relays some to the hypothalamus. Hypothalamus monitors the body for temperature, pH, other conditions. Hypothalamus signals pituitary gland if conditions need to be corrected.

Pituitary gland The pituitary is the “master gland” that signals other glands to produce their hormones when needed. The pituitary receives signals from the hypothalamus, and responds by sending out the appropriate hormone to other endocrine glands.

Pituitary gland Pituitary HormoneFunctions Follicle-stimulating hormone Stimulates egg maturation in the ovary and release of sex hormones. Lutenizing hormone Stimulates maturation of egg and of the corpus luteum surrounding the egg, which affects female sex hormones and the menstrual cycle. Thyroid-stimulating hormoneStimulates the thyroid to release thyroxine. Adrenocorticotropic hormoneCauses the adrenal gland to release cortisol. Melanocyte-stimulating hormoneStimulates synthesis of skin pigments. Growth hormoneStimulates growth during infancy and puberty. Antidiuretic hormoneSignals the kidney to conserve more water. OxytocinAffects childbirth, lactation, and some behaviors.

Other hormones Many other organs besides the endocrine glands produce hormones. Kidneys produce several hormones that regulate blood pressure, which is essential for kidney function. The digestive system produces several hormones that regulate appetite.

Disorders Type II diabetes (remember Type I from autoimmune diseases?) Instead of not producing enough insulin cells develop insulin resistance. Insulin essentially doesn’t work as well as it should The pancreas produces more insulin to compensate but can’t keep up Glucose builds up in the blood Complications: Higher risk of cardiovascular disease Nerve damage – excess sugar damages nerve cells Kidney damage And many manymore

Hypothyroidism – low thyroid activity Symptoms Tired Weight gain Depression Cold sensitivity Dry skin and hair Muscle aches Causes Typically an autoimmune disorder (Autoimmune – self immunity, the body attacks itself) Also cancer or treatment for overactive thyroid

Hypothyroidism Diagnosis Blood test measuring hormone levels Compares the levels of two hormones, thyroid- stimulating hormone and thyroxine High levels of thyroid-stimulating hormone and low thyroxine is a sign of underactive thyroid

Hypothyroidism Treatment Hormone replacement pills Typically for the rest of your life Complications Heart disease Fertility problems