Endocrine System

Hormones Hormones are chemicals that are secreted into the blood stream by the endocrine glands Hormones are received by target cells throughout the body Target cells have receptor proteins that help determine the response to the hormone Different hormone/receptor combinations cause different responses

Types of Hormones Hormones Steroid Hormones Diffuse directly into target cell Lipid soluble Made in SER of secreting cell Peptide and Amine Hormones Cannot directly enter target cell Large polypeptide molecules Insoluble in lipid

Steroid Hormone

Target Cell Creates Response

Chemical Structure of Steroids Steroid hormones are created by modifying cholesterol molecules

Peptide and Amine Hormones Peptide and Amine hormones are large molecules that are not lipid soluble and cannot enter target cells directly.

Glands of the Endocrine System Hypothalamus Connection between the Nervous System and the Endocrine System Secretes Antidiuretic Hormone (ADH) to help maintain kidney functions Secretes hormones into the pituitary gland to stimulate the production of other hormones

Pituitary Gland Sometimes called the “Master Gland” Controls many other glands in the body Directly connected to the Hypothalamus through neural connections

Pituitary Gland Hormone Effect Somatotropin (Growth Hormone) Affects growth and development; stimulates protein production Prolactin Stimulates milk let down during lactation Thyroid-stimulating hormone (TSH) Stimulates the production and secretion of thyroid hormones Luteinizing hormone (LH) In females this LH acts on the ovary to stimulate the production of estrogens and induce ovulation. In males this LH acts on the testis to stimulate the production of testosterone.

Pineal Gland Located in the center of the brain behind the Hypothalamus Produces Melatonin which helps regulate sleep and waking cycle Sometimes called the “Biological Clock”

Thyroid Located in front of the trachea Responsible for maintaining Metabolism

Thyroid Hormone Effect Triiodothyronine (T3) Body temperature, growth and heart rate Thyroxine (T4) Controls the metabolic processes in the body Calcitonin Stimulates calcium deposits to bones

Parathyroid Four small glands located on the back of the Thyroid Help to maintain the amount of calcium in the blood to maintain muscle and nervous function

Parathyroid Releases Parathyroid Hormone when calcium levels are low This causes bone break down and increased calcium absorption

Thymus Essential in the development of immune functions Very large in childhood Tissue is replaced by fat into adulthood Produces humoral which stimulates the development of the lymphoid system

Adrenal Glands Located on each of the Kidneys Divided into two sections Cortex Produces hormones essential to life Medulla Produces hormones not essential to life

Adrenal Glands Hormone Effect Cortisol Immune suppression and stress response Adrenaline (Epinephrine) *** Also a neurotransmitter Variety of reactions depending on the tissue. Heart – Increases heart rate Lungs – Increases respiration rate Liver - Glycogenolysis Noradrenaline (Norepinephrine) *** Also a neurotrasmitter Similar to Adrenaline

Pancreas Main control of the blood sugar in the body Secretes Insulin or Glucagon as required to maintain blood sugar levels Endocrine portion is called the Islets of Langerhans

Blood Sugar Homeostasis

Testes/Ovaries Development and maintenance of sex traits Become more active at puberty Produce steroid hormones

Testes/Ovaries Hormone Effect Estrogen Maintaining female sex characteristics Testosterone Maintaining male sex characteristics Progesterone Stimulates the lining of the uterus and prepares the body for milk production Inhibin Inhibits the production of Follicle Stimulating Hormone (FSH) in the Pituitary gland