The Endocrine System
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The Endocrine System --the OTHER sensing and response system The Endocrine System Controls: • • • • • The Endocrine System Controls: • Reproduction • Growth & development • Homeostasis • Metabolism • Immune response Definitions • Gland • Endocrine • Hormone Definitions • Gland—an organ designed to secrete • Endocrine—secreting inside the body • Hormone—the secretion of an endocrine gland Endocrine vs Exocrine Endocrine vs Exocrine Exocrine glands have a duct Endocrine glands do not Endocrine glands secrete their products into the bloodstream For example: • Exocrine glands include… Gland Duct leads to: • Sweat glands • Sebaceous glands • Pancreas • Mammary glands For example: • Exocrine glands include… Gland Duct leads to: • Sweat glands surface of skin • Sebaceous glands base of follicle • Pancreas small intestine • Mammary glands nipple For example: • Endocrine glands include… Gland Duct leads to: • Anterior pituitary • Parathyroids • Adrenal Cortex For example: • Endocrine glands include… Gland Duct leads to: • Anterior pituitary --No duct-• Parathyroids --No duct-• Adrenal Cortex --No duct-- These glands secrete hormones directly to the bloodstream Negative feedback • Homeostasis is maintained in the body by negative feedback— When anything changes, the response is to undo that change • The elements of the system are: stimulus, sensor, effector and response. In general: Effector Response lowers it If the stimulus is too high Sensor Response raises it Effector If the stimulus is too low Review • Body temperature is maintained by a negative feedback system. --The sensor is in the hypothalamus. --The effectors are blood vessels and sweat glands in the skin. For body temperature: Blood vessels dilate, sweat is produced Blood vessels constrict, sweat is not produced Skin Hypothalamus Skin If the temperature is too high If the temperature is too low For blood sugar: Insulin causes body cells to take in glucose Pancreas If the blood glucose level is too high Pancreas Glucagon causes the liver to release glucose If the blood glucose level is too low Pancreas For blood sugar: • The sensor and effector cells are in the pancreas • The pancreas releases insulin into the bloodstream to lower blood sugar or • The pancreas releases glucagon into the bloodstream to raise blood sugar Types of hormones Types of hormones • Peptide hormones • Steroid hormones Types of hormones • Peptide hormones —proteins and related molecules • Steroid hormones —lipid molecules Types of hormones • Peptide hormones —proteins and related molecules Receptors are on target cell surfaces • Steroid hormones —lipid molecules Receptors are in target cell nuclei Nonsteroid hormone (first messenger) Nonsteroid hormone (first messenger) Cytoplasm Enzyme ATP cAMP Receptor protein Plasma membrane of target cell Second messenger Effect on cellular function, such as glycogen breakdown Figure 9.1b Second-Messenger System (Non-steroid Hormone Action) A non-steroid hormone will: • Bind to a membrane receptor (without entering cell) • (Series of reactions) activates an enzyme • Enzyme catalyzes a reaction to form the second-messenger (us. cAMP) • Second-messenger molecule a specific response Steroid hormone Steroid hormone Nucleus Receptor protein Cytoplasm Hormone-receptor complex DNA mRNA New protein Plasma membrane of target cell Figure 9.1a Direct Gene Activation (Steroid Hormone Action) • • • • • • A steroid hormone will: Diffuse through membrane of target cells Enter the nucleus Bind to a specific protein in the nucleus Bind to specific sites on the cell’s DNA Activate genes synthesis of new proteins Endocrine Glands • • • • • • • • Hypothalamus Anterior pituitary Posterior pituitary Thyroid Parathyroids Adrenal Medulla Adrenal Cortex Pancreas Location of Endocrine Glands • • • • • • • • Hypothalamus Anterior pituitary Posterior pituitary Thyroid Parathyroids Adrenal Medulla Adrenal Cortex Pancreas in the brain base of the brain base of the brain front of the neck sides of the neck above the kidney above the kidney behind stomach Location of Major Endrocrine Organs Figure 9.3 Hormones of each Endocrine Gland • Hypothalamus • Anterior pituitary • • • • • • Posterior pituitary Thyroid Parathyroids Adrenal Medulla Adrenal Cortex Pancreas RF’s ACTH, FSH, GH ,LH, PRL,TSH ADH, OT Cal,T3-4 PTH EPI, NE Cor, Ald Ins, Glu, SS For example: Blood sugar Insulin causes body cells to take in glucose Pancreas If the blood glucose level is too high Pancreas Glucagon causes the liver to release glucose If the blood glucose level is too low Pancreas For example: Metabolism T3-4Less RfLess TSHless T3-4 Ant. Pit. & Thyroid If the metabolism level is too high Hypothalamus RFanterior pituitary. TSH causes the thyroid to make T3-4 to increase metabolism If the metabolism level is too low Ant. Pit. & Thyroid Hypothalamus • --Part of the brain • --Closely associated with pituitary (blood vessel and nerve connection) • --Makes releasing factors (RF’s) to affect pituitary Hormones of the Anterior Pituitary Figure 9.4 Pituitary • --Part of the brain, sits in the sella turcica • --Controlled by hypothalamus, controls other glands • --Has two (very different) parts- anterior and posterior Anterior Pituitary • --Controls other glands --ACTHadrenal cortex --PRLmammary glands --FSHovaries --LHovaries • --GH is the only hormone with wider effects—causes growth of bone and muscle For the reproductive system Ant. Pit Progesterone and estrogen stimulate the hypothalamus to make RFs FSH and LH stimulate the ovary Ovaries Posterior pituitary • --Direct nervous control from hypothalamus • (Hormones are made in hypothalamus, stored for release) --OT-causes smooth muscle contraction in childbirth, nursing, erections, etc. --ADH—(next slide) For water Shuts off ADH—kidneys reabsorb less water ADH causes kidneys to reabsorb more water Hyp/Post.Pit Too much water in the blood Hypothalamus Too little water in the blood Post. Pit Thyroid • --Controlled by TSH (from ant. pit.) • Makes --T3-4— triiodothyronine and thyroxine, --stimulates most cells to use energy and make proteins (higher metabolism). --Contain iodine atoms. --Calcitonin (not quite the next slide) Thyroid Gland Figure 9.7a For metabolism: T3-4Less Rf Less TSH less T3-4 Ant. Pit. & Thyroid If the metabolism level is too high Hypothalamus RFanterior pituitary. TSH causes the thyroid to make T3-4 to increase metabolism If the metabolism level is too low Ant. Pit. & Thyroid For calcium Calcitonin causes bones to store calcium Parathyroid hormone causes bones to release calcium, kidneys and intestines to absorb Ca++ Thyroid Thyroid/ Parathyroid Parathyroid If the blood calcium level is too high If the blood calcium level is too low Parathyroids • --Four of them! Near the thyroid • --Makes PTH only (previous slide)— (antagonistic to calcitonin) • —affects bones, kidneys and intestines to increase Ca++ levels Pancreas • --Endocrine (islets of Langerhans) and exocrine (in digestive system) • Makes— --glucagon in a (alpha) cells (next slide) --insulin in b (beta) cells (next slide) --somatostatin in d (delta) cells --antagonist to GH For Blood Sugar: Insulin causes body cells to take in glucose Pancreas If the blood glucose level is too high Pancreas Glucagon causes the liver to release glucose If the blood glucose level is too low Pancreas Adrenal glands • Has two parts– the adrenal cortex (outside) and adrenal medulla (inside) --Cortex and gonads make the only steroid hormones --Medulla makes neurotransmitters as hormones Adrenal cortex • Outside layer • Stimulated by ACTH from ant. pit. • Makes steroids --aldosterone—causes kidneys to reabsorb sodium and water --cortisol—causes tissues to increase blood nutrients, allows damaged tissues to heal. Hormones of the Adrenal Cortex Figure 9.11 Adrenal Medulla • Center of the gland • Derived from nerve tissue, directly controlled by sympathetic NS • Hormones are used in NS as neurotransmitters --norepinephrine-(aka. adrenalin) fight-or-flight --epinephrine (similar to norepinephrine) For emergency use only Norepinephrine (adrenalin) stimulates fight-or-flight responses Hypothalamus Adrenal medulla Direct sympathetic nerve impulses! Which hormones and glands are stimulated by: 1) Other hormones and glands? 2) Blood chemistry? 3) Neurons? Hormonal Stimuli of Endocrine Glands Most common Endocrine glands are activated by other hormones Ex: Anterior pituitary hormones Figure 9.2a Humoral Stimuli of Endocrine Glands Changing blood levels of certain ions stimulate hormone release Ex: Humoral indicates various body fluids such as blood and bile Calcitonin Insulin Parathyroid hormone Figure 9.2b Neural Stimuli of Endocrine Glands Nerve impulses stimulate hormone release Most are under the control of the sympathetic nervous system Ex: norepinephrine epinephrine by adrenal medulla Figure 9.2c Major Endocrine Organs • • • • • • • • • Pituitary gland Thyroid gland Parathyroid glands Adrenal glands Pineal gland Thymus gland Pancreas Gonads (Ovaries and Testes) Hypothalamus
