The Endocrine System H1: Hormonal Control

Endocrine System: a system of glands that secrete hormones to regulate body function HORMONES: chemical messengers or regulators - they are released by cells in one part of the body and affect cells in other parts of the body to speed up or slow down processes. Endocrine Hormones – are produced in endocrine glands and secreted directly in the blood and distributed by the circulatory system.

Makes hormones and regulates the pituitary gland Pineal gland (makes serotonin which regulates sleep patterns)

Endocrine Gland

How do Hormones Signal Cells? Note: Hormones do not affect ALL cells Depends on whether or not that cell has a receptor for the particular hormone. (TARGET CELLS are the cells hormones act on) There are 2 types of hormones: 1. Steroid Hormones 2. Protein Hormones

Steroid Hormones made from cholesterol (lipid); Complex ring of C, H, and O Soluble in fat but NOT water – so can dissolve through cell membrane Inside the cell they bind to receptor in the cytoplasm or nucleus to form the hormone- receptor complex

Steroid Hormones The receptor-hormone complex can then switch certain genes on or off by promoting or inhibiting the transcription of genes ex: sex hormones ex: cortisol (stimulates the conversion of amino acids to glucose by the liver and decreases expression of insulin)

Steroid Hormones

Steroid Hormones SECRETORY CELL HORMONE TARGET CELL RECEPTOR

Protein Hormones Made of chains of amino acids or modified amino acids Soluble in water but insoluble in fats (can’t dissolve through cell membrane) Ex: insulin, growth hormone

Protein Hormones The protein hormones attach to receptor sites on the cell membrane The hormone-receptor complex leads to the release of a secondary messenger in the cell that can spread throughout the cell and relay messages Ex of secondary messengers: Ca2+ and cyclic adenosine monophosphate (cyclic AMP) Secondary messengers then activate enzymes in the cell.

Protein Hormones

Animations http://highered.mheducation.com/sites/007 2437316/student_view0/chapter47/animatio ns.html#

Control Systems The body relies on the nervous system and the endocrine system for control of organs and tissues The nervous system allows the body to adjust quickly to environmental changes The endocrine system is designed to maintain control over longer durations

Hypothalamus The hypothalamus in the brain is part of both the nervous system and the endocrine system As an endocrine gland it creates hormones that either a) are stored in the (posterior) pituitary gland b) control the release of hormones from the (anterior) pituitary gland

Pituitary Gland (The Master Gland) “master gland” because it controls the other endocrine glands (However, it is controlled by the hypothalamus) Located at the base of the brain; connected to the hypothalamus by a stalk The pituitary produces and stores hormones The hypothalamus stimulates their release when necessary

Posterior Lobe Stores and releases hormones that are actually made by the neurosecretory cells of the hypothalamus The hormones travel from the hypothalamus to the pituitary via specialized nerve cells They are stored in the pituitary and released into the blood when necessary (The hypothalamus will send a nerve response to have the hormones released) Ex: ADH (antidiuretic hormone), oxytocin

Posterior Lobe Ex: ADH release Hypothalamus creates ADH and stores it in pituitary gland Osmoreceptors in hypothalamus recognize osmotic pressure (solute concentration of blood) Impulses are sent to pituitary to increase or inhibit the release of ADH into blood stream accordingly

Anterior Lobe Produces its own hormones However, the hypothalamus regulate their release with inhibiting or releasing hormones made by the hypothalamus The inhibiting and releasing hormones are transported to the anterior lobe of the pituitary via specialized nerve cells This stimulates the release of pituitary hormones which will travel through the blood to target cells

Anterior Lobe Ex: TSH and TRH The anterior lobe produces and stores TSH (thyroid stimulating hormone) TSH is released by the anterior lobe when the hypothalamus releases TRH (thyroid releasing hormone)

Ie cortisol

Thyroid Stimulating Hormone (TSH) Thyroid Gland Target Organ Primary Function   Thyroid Stimulating Hormone (TSH) Thyroid Gland Releases hormones made in the thyroid (such as thyroxine) Adrenocorticotropic Hormone (ACTH) Adrenal Cortex Stimulates the release of hormones involved in the stress response (such as cortisol) Somatotropin (STH) also known as Growth Hormone (GH) Most body cells Promotes growth Follicle Stimulating Hormone (FSH) Gonads (ovaries and testes) Females: stimulates follicle development in the ovaries Males: Promotes the development of sperm cells in the testes Luteinizing Hormone (LH) Females: stimulates ovulation and the formation of the corpus luteum Males: stimulates the production of testosterone Prolactin Mammary Glands Maintains milk production in lactating females

Posterior Pituitary Hormones Target Organ Primary Function Antidiuretic Hormone (ADH) kidneys Increases water reabsorption in the kidney Oxytocin Uterus, mammary glands Initiates strong uterine contractions Triggers milk release in lactating females