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Transcript
Anatomy & Physiology Endocrine System 1 Pg. 131 2 General Characteristics of Endocrine System • The endocrine system assists the nervous system with communication and control of the body • The cells, tissues, and organs are called endocrine glands • They are ductless • They use the bloodstream • They secrete hormones • There are also similar glands called paracrine and autocrine glands that are quasi-endocrine • Other glands that secrete substances are the exocrine glands • They have ducts • They deliver their products directly to a specific site 3 Nerve impulse Neuron transmits nerve impulse Glandular cells secrete hormone into bloodstream Neurotransmitter released into synapse Bloodstream Postsynaptic cell responds Target cells (cells with hormone receptors) respond to hormone Hormones have no effect on other cells (b) 4 5 Hormone Action •Hormone – a very powerful substance (chemical messenger) secreted by a endocrine gland into the bloodstream, that affects the function of another cell or “target cell” -needed in very small amounts (very potent) -produce long-lasting effects in the target cells -regulate metabolic processes (homeostatic) -regulated by negative feedback mechanisms Hypothalamus Pituitary gland Parathyroid gland Pineal gland Thyroid gland Thymus Adrenal gland Kidney Pancreas Ovary (in female) Testis (in male) 6 Chemistry of Hormones Chemically, hormones are either: • Steroid or steroid-like hormones such as: • Sex hormones • Adrenal cortex hormones • Non-steroid hormones such as: • Amines • Proteins • Peptides • Glycoproteins 7 8 Control of Hormonal Secretions • Primarily controlled by negative feedback mechanism • Hormones can be short-lived or may last for days • Hormone secretions are precisely regulated 9 Control Sources Control center Endocrine gland inhibited. Receptors Hormone control mechanism senses change. Stimulus Hormone levels rise or controlled process increases. Effectors Hormone secretion decreased. Response Hormone levels return toward normal. too high Normal hormone levels too low Stimulus Hormone levels drop or controlled process decreases. Receptors Hormone control mechanism senses change. Response Hormone levels return toward normal. Effectors Hormone secretion increased. Control center Endocrine gland stimulated. 10 Control Sources – – Hypothalamus – Nervous system Changing level of substance in plasma – Anterior pituitary gland (a) Peripheral endocrine gland Endocrine gland Endocrine gland Target cells Target cells Target cells Action Action Action (b) (c) 11 12 Pg. 133 13 Hypothalamus • During hormonal control, endocrine organs are stimulated by hormones from other endocrine organs, starting with the hypothalamus • Directs activities of the pituitary gland by secreting hypothalamic releasing hormones and hypothalamic nonreleasing hormones to stimulate or inhibit release of hormones from the pituitary gland • Very small gland buried deep in the brain below the thalamus • Plays an important role in regulating everyday functions such as metabolism, heart rate, energy level, body temperature, thirst, nutrient intake, blood pressure, and blood composition. 14 Hypothalamus 15 16 Pituitary Gland • Lies at the base of the brain in the sella turcica, small depression in the sphenoid bone of the skull • Known as the “master gland” because of its major influence on body’s activities (but still controlled by the hypothalamus) • Size of a grape • Connected to hypothalamus by a stalk called infundibulum • Consists of two distinct portions: • Anterior pituitary (adenohypophysis) – hormonally controlled • Posterior pituitary (neurohypophysis)- neurally controlled 17 Anterior Pituitary Hormones • Hypothalamic releasing hormones stimulate cells of anterior pituitary to release hormones •Produces 6 hormones: • Growth hormone (GH)-growth and development; helps fat be used for energy, saving glucose to maintain blood sugar levels Third ventricle • Prolactin hormone (PR)-aka LTH, develops breast tissue and stimulates production of milk after childbirth • Thyroid-stimulating hormone (TSH)-stimulates growth and secretion of thyroid • Adrenocorticotropic hormone (ACTH)-stimulates growth and secretion of adrenal cortex • Follicle-stimulating hormone (FSH)-production of estrogen in females; production of sperm in males • Luteinizing hormone (LH)-production of estrogen and 18 progesterone in females; production of testosterone in males Anterior lobe of pituitary gland Posterior lobe of pituitary gland 19 20 Hormones from Hypothalamus GHRH SS Growth Somatostatin hormonereleasing hormone PRF Prolactinreleasing factor PIH Prolactinrelease inhibiting hormone TRH Thyrotropinreleasing hormone CRH Corticotropinreleasing hormone GnRH Gonadotropinreleasing hormone Hormones from Anterior Pituitary GH Growth hormone Bone Muscle Adipose tissue PRL Prolactin Mammary gland TSH Thyroidstimulating hormone Thyroid ACTH Adrenocorticotropic hormone Adrenal cortex LH Luteinizing hormone Ovary FSH Folliclestimulating hormone Testis 21 Posterior Pituitary Hormones • Structurally consists of nerve fibers and neuroglia v. glandular epithelial cells of the anterior pituitary gland • The nerve fibers originate in the hypothalamus •Nerve impulses from hypothalamus stimulate nerve endings in the posterior pituitary gland to release hormones • Two hormones are stored here: • Antidiuretic hormone (vasopressin): maintains water balance by increasing absorption of water in kidney tubules • Oxytocin: released during childbirth causing strong contractions when a mother breastfeeds; synthetic form known as Pitocin 22 23 24 25