Endocrine System

• ENDOCRINE SYSTEM- Where hormones are made.
• A gland is an organ whose cells secrete materials into other regions of the body.
• Hormones are the chemical substances secreted by endocrine glands directly into the bloodstream.
• Target cell is a specific cell a hormone binds to and acts on (carries a message to).
• Receptors are found on the surface of their membranes of the target cells, they are protein molecules that recognize specific hormones only.
• Neurosecretory cell is a specialized nerve cell that, when stimulated, releases hormones directly into the bloodstream for delivery to its target cells.
• Feedback System operates as a cycle in which the last step affects the first step.
• Negative Feedback System- an endocrine gland decreases its activity in response to an increased concentration of the substance it regulates.
• Positive Feedback System- operates when an endocrine gland increases its rate of hormonal secretion in response to a rising concentration of the substance the hormone regulates.
• Endocrine Glands (endo means “within”; krinein means “secrete”) Has hormone-containing vesicles which then transport these chemicals to the target cells in other parts of the body.
• Exocrine Glands ( exo means “outwards”; krinein means “secrete”)- Contain ducts that lead to the target cell.Examples of exocrine glands are sweat glands, mucus glands and salivary glands.
• Hypothalamus

  - Main regulator of homeostasis.

  - Found at the base of your brain.

  - Produces hormones that help turn on and off the other endocrine glands in your body. Like, oxytocin and the antidiuretic hormone (ADH).
• Pituitary Gland (Hyphosis)- Is a pea-sized gland found in the center of the skin, right behind the bridge of the nose, below the hypothalamus of the brain.
• Pituitary gland divided into Anterior Pituitary and Posterior Pituitary Gland, each secretes different hormones.
• when conditions within the body call growth, the hypothalamus secretes the releasing hormone that will cause the anterior pituitary to release the  growth hormone (GH), also known as somatotropin.
• Thyroid Gland- Located in the neck region and produces two hormones- thyroxine and calcitonin.
• Thyroxine promotes growth and development, and Calcitonin which controls calcium level in the blood.
• Parathyroid Glands- Four tiny glands embedded on the surface of the thyroid.
• Calcium is a mineral that keeps your nerves and muscles working properly.
• Pancreas 

  — Is an organ with both endocrine and exocrine cells.

  — Exocrine cells enzymes that aid in digestion in the small intestine. Endocrine cells, which are arranged in bunches called Pancreatic Islets, secrete insulin and glucagon.
• Insulin- plays an important role in keeping the levels of sugar (glucose) in the bloodstream under control.
• Glucagon- on the other hand, does exactly the opposite. It increases the level of sugar in the body by speeding up the conversion of glycogen to sugar in the liver.
• Adrenal Glands- Each of the two adrenal glands is found on the top of a kidney. It consists of two parts- the inner layer called the adrenal medulla and the outer layer called the adrenal cortex. 
• Epinephrine (also called adrenaline)- increases heart rate, stimulates faster breathing, and enlarges the pupils of the eyes.
• Nonrepinephrine- together with epinephrine it makes more fuel available to the body cells.
• Corticosteroids- are steroid hormones that promote glucose synthesis and break down fats and proteins. 
• Pineal Glands- Located near the thalamus of the brain.- Produces melatonin which regulates body rhythms and sleep patterns.
• Gonads- The human reproductive organs.- The female reproductive organs (ovaries) and the male reproductive organs (testes) are produce sex hormones responsible for the secondary sexual characteristics.