WEEK-1_ENDOCRINE-SYSTEM-1 PDF

13/11/2024 Because learning changes everything.® Chara...

13/11/2024 Because learning changes everything.® Characteristics 1 The endocrine system is composed of endocrine glands and specialized endocrine cells located throughout the body. Chapter 10 Endocrine glands and cells secrete minute amounts of Endocrine System chemical messengers called hormones into the Lecture Outline bloodstream, rather than into a duct. Seeley’s ESSENTIALS OF Hormones then travel through the general blood circulation ANATOMY & PHYSIOLOGY Eleventh Edition to target tissues or effectors. Cinnamon VanPutte Jennifer Regan Andrew Russo Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 2 Characteristics 2 Endocrine System Glands The target tissues have receptors for a specific hormone. Hormones produce a particular response in the target tissues. Figure 10.1 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 3 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 4 Classes of Chemical Messengers 1 Classes of Chemical Messengers 2 Autocrine: Neurotransmitter and neuromodulators: released by cells and a have local effect on same cell type secreted by nerve cells Example - eicosanoids Example - nervous system function Paracrine: Hormones and neurohormones: released by cells that affect other cell types in close secreted into blood and bind to receptors on target tissues proximity Example - epinephrine and insulin Example - somatostatin Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 5 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 6 1  13/11/2024 Endocrine System Functions 1 Endocrine System Functions 2 1. Regulation of metabolism 6. Regulation of cardiovascular function 2. Control of food intake and digestion 7. Control of blood glucose and other nutrients 3. Modulation of tissue development 8. Control of reproductive functions 4. Regulation of ion levels 9. Stimulation of uterine contraction and milk release 5. Control of water balance 10. Modulation of immune system function Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 7 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 8 Types of Hormones Effects of Binding Proteins Water-soluble hormones: include proteins, peptides, amino acids most common type of hormone Examples - growth hormone, antidiuretic, prolactin Lipid-soluble hormones: include steroids and eicosanoids Examples - Luteinizing hormone, androgens Figure 10.2 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 9 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 10 Control of Hormone Secretion 1 Control of Hormone Secretion 2 Blood-borne chemicals can directly stimulate the release Hormone release can also be controlled by other of some hormones. hormones. These chemicals are referred to as humoral stimuli It occurs when a hormone is secreted that, in turn, because they circulate in the blood, stimulates the secretion of other hormones. Humoral refers to body fluids, including blood. The same three types of stimuli (humoral, neural, and hormonal) can stimulate or inhibit hormone release. Hormone release can also be under neural control. Following action potentials, neurons release a neurotransmitter into the synapse with the cells that produce the hormone. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 11 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 12 2  13/11/2024 Control by Humoral Stimuli Control by Neural Stimuli Figure 10.3 Figure 10.4 Access the text alternative for slide images. Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 13 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 14 Control by Hormonal Stimuli Inhibition of Hormone Release 1 Humoral inhibition of hormone release generally involves the actions of companion hormones. Usually each of the companion hormones performs an opposite function. For example, to raise blood pressure, the adrenal cortex secretes the hormone aldosterone in response to low blood pressure, but to lower it the heart atria secrete atrial natriuretic peptide. They work together to maintain homeostasis of blood pressure. Figure 10.5 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 15 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 16 Inhibition of Hormone Release 2 Regulation of Blood Hormone Levels Neurons inhibit targets just as often as they stimulate Two major mechanisms maintain hormone levels in the targets. blood within a homeostatic range: negative feedback and positive feedback If the neurotransmitter is inhibitory, the target endocrine gland does not secrete its hormone. Most hormones are regulated by a negative-feedback mechanism, whereby the hormone’s secretion is inhibited In control of hormone release by other hormones, some by the hormone itself once blood levels have reached a hormones are inhibitory hormones, that reduce the release certain point. of the hormone being controlled. Some hormones are regulation by positive feedback, as For example, thyroid hormones can control their own exemplified by tropic hormone action. blood levels by inhibiting their anterior pituitary tropic hormone. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 17 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 18 3  13/11/2024 Negative and Positive Feedback Hormone Receptors and Mechanisms of Action 1 A hormone can stimulate only the cells that have the receptor for that hormone. The portion of each receptor molecule where a hormone binds is called a receptor site. The receptor site has specificity, allowing only one hormone to bind to it. Some hormones, such as epinephrine, can bind to a “family” of receptors that are structurally similar. This specificity is due to molecular shape and chemical characteristics. Figure 10.6 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 19 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 20 Hormone Receptors and Mechanisms of Action 2 Lipid-Soluble Hormone Receptors Lipid-soluble and water-soluble hormones bind to their Nuclear receptors can also be located in the cytoplasm, own classes of receptors. but then move to the nucleus when activated. Lipid-soluble hormones bind to nuclear receptors due to When hormones bind to nuclear receptors, the hormone- their lipid solubility and small molecular size allowing to receptor complex interacts with nuclear DNA to regulate easily pass through the cell membrane. specific gene transcription. Water-soluble hormones bind to membrane-bound receptors. Water-soluble hormones are polar molecules and cannot pass through the cell membrane. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 21 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 22 Water-Soluble Receptors Target Tissue Specificity and Response Water-soluble hormones, such as protein and peptide types, cannot pass through the cell membrane. Interactions are with membrane-bound receptors, that are proteins that extend across the cell membrane, with their hormone-binding sites exposed on the cell membrane’s outer surface. When the hormone binds to the receptor, it turns on intracellular enzymes that ultimately cause the response dictated by the hormone-receptor interaction. Figure 10.7 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 23 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 24 4  13/11/2024 Nuclear and Membrane-Bound Receptors Action of Nuclear Receptors Lipid-soluble hormones stimulate protein synthesis. Lipid-soluble hormones diffuse across the cell membrane and bind to their receptors, with the complex now binding to hormone-response elements on DNA. This action regulates the transcription of specific messenger ribonucleic acid (mRNA) molecules and protein synthesis occurs. Figure 10.8 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 25 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 26 Nuclear Receptor Model Membrane Bound Receptor Actions 1 Membrane bound receptors act in two ways, either altering the activity of G proteins on the inner surface of the cell membrane or directly altering the activity of intracellular enzymes. Activation of G proteins, or intracellular enzymes, elicits specific responses in cells, including the production of molecules called, second messengers. Figure 10.9 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 27 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 28 Membrane Bound Receptor Actions 2 G-Protein Activation 1 A second messenger molecule is produced inside a cell Many membrane-bound receptors produce responses once a ligand binds to its membrane-bound receptor. through the action of G proteins, which consist of 3 subunits. A second messenger, such as cyclic adenosine monophosphate (cAMP), then activates specific cellular The G proteins are so named because one of the subunits processes inside the cell in response to the hormone. binds to guanine nucleotides. G-proteins, after several sequential actions, interact with adenylate cyclase, an enzyme that converts ATP to cAMP. cAMP binds to protein kinases and activates them. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 29 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 30 5  13/11/2024 G-Protein Activation 2 Cyclic AMP Synthesis Protein kinases are enzymes that, in turn, regulate the activity of other enzymes. Depending on the other enzyme, protein kinases can increase or decrease its activity. Phosphodiesterase, an intracellular enzyme, breaks down cAMP and thus results in no further cell stimulation. Figure 10.10 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 31 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 32 Signal Amplification 1 Signal Amplification 2 Hormones that stimulate the synthesis of second With amplification, a single hormone activates many messengers act quickly and have an amplification effect. second messengers, each of which activates enzymes that produce an enormous amount of final product. Each receptor produces thousands of second messengers, leading to a cascade effect and ultimately The efficiency of this second-messenger amplification is amplification of the hormonal signal. virtually unparalleled in the body. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 33 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 34 Cascade Effect Pituitary Gland 1 Small gland in brain Controlled by hypothalamus Divided into 2 regions: anterior and posterior Secretes at least 6 hormones Figure 10.11 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 35 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 36 6  13/11/2024 Pituitary Gland 2 Hypothalamic Control of the Anterior Pituitary Gland The anterior pituitary gland synthesizes hormones under the control of the hypothalamus. Neurons of the hypothalamus secrete releasing hormones that stimulate the production and secretion of a specific hormone. Inhibiting hormones decrease the secretion of a specific anterior pituitary hormone Figure 10.12 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 37 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 38 Hypothalamic Control of the Posterior Pituitary Hypothalamus and Anterior Pituitary The posterior pituitary gland stores and releases hormones produced by neuroendocrine cells in the hypothalamus. The two hormones released from the posterior pituitary are antidiuretic hormone (ADH) and oxytocin. Figure 10.13 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 39 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 40 Anterior Pituitary Hormones 1 Anterior Pituitary Hormones 2 Growth Hormone: Thyroid-Stimulating Hormone (TSH): Target tissues: most tissues Target tissues: thyroid gland Functions: stimulates growth of bones, muscles, and Functions: regulates thyroid gland secretions organs Abnormalities: Abnormalities: Too much TSH, thyroid gland enlarges (goiter) Too much GH causes giantism Too little TSH, thyroid gland shrinks Too little GH causes pituitary dwarfism Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 41 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 42 7  13/11/2024 Anterior Pituitary Hormones 3 Anterior Pituitary Hormones 4 Gonadotropin Hormone Gonadotropin Hormone Luteinizing Hormone (LH) for females: Follicle-Stimulating Hormone (FSH) for females: Target tissue: ovaries Target tissue: follicles in ovaries Function: promotes ovulation and progesterone production Function: follicle maturation and estrogen secretion LH for males: FSH for males: Target tissue: testes Target tissue: seminiferous tubules (testes) Function: production of sperm and testosterone Function: sperm production Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 43 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 44 Anterior Pituitary Hormones 5 Anterior Pituitary Hormones 6 Prolactin: Melanocyte Stimulating Hormone (MSH): Target tissues: mammary glands and ovaries Target tissues: melanocytes in the skin Functions: milk production Functions: stimulate melanin production in melanocytes Adrenocorticotrophic Hormone (ACTH): Target tissues: cells of adrenal cortex Functions: stimulate production of certain corticosteroids Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 45 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 46 Hormones of the Posterior Pituitary 1 Hormones of the Posterior Pituitary 2 Antidiuretic Hormone (ADH): Oxytocin: Target tissues: kidneys Target tissues: uterus Functions: conserve water Functions: increases uterine contractions during labor Abnormalities: Diabetes insipidus low ADH kidneys to produce large amounts of dilute (watery) urine can lead to dehydration and thirst Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 47 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 48 8  13/11/2024 Hypothalamus and Posterior Pituitary Thyroid Gland One of largest glands Requires iodine to function Secretes thyroid hormone and calcitonin Thyroid hormones secreted by follicular cells: Target tissues: most tissues Functions: regulates metabolic rates and is needed for growth Calcitonin secreted by parafollicular cells: Target tissues: bone and some other tissues Figure 10.14 Function: reduces blood calcium level when high Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 49 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 50 Thyroid Gland and Parathyroid Glands Regulation of Thyroid Hormone Secretion (d) ©Victor Eroschenko Figure 10.15 Figure 10.16 Access the text alternative for slide images. Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 51 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 52 Thyroid Hormone Disorders Parathyroid Gland Hypothyroidism: Hyperthyroidism: Parathyroid hormone (PTH): Decreased metabolism Increased metabolism Target tissues: bones and kidneys Weight gain, reduced Weight loss, increased Functions: regulates blood Ca2+ levels (more than appetite, fatigue appetite, nervousness calcitonin) Low temp. and pulse Higher temp. and pulse If Ca2+ is low, then osteoclasts break down bone matrix and Dry, cold skin Warm, flushed skin less Ca2+ is lost in urine. Myxedema in adults Graves’ disease (leads to If Ca2+ is high, then osteoclasts don’t break down bone goiter) matrix and more Ca2+ is lost in urine. Cretinism in infants Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 53 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 54 9  13/11/2024 Regulation of Blood Calcium Levels Adrenal Gland Actions The adrenal glands are two small glands located superior to each kidney Each adrenal gland has an inner part, called the adrenal medulla, and an outer part, called the adrenal cortex. The adrenal medulla and the adrenal cortex function as separate endocrine glands. Figure 10.17 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 55 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 56 Adrenal Glands Adrenal Medulla Hormones 1 Epinephrine/Norepinephrine: Target tissues: heart, blood vessels, liver, fat cells Functions: released as part of fight or flight response (c) ©Victor Eroschenko Figure 10.18 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 57 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 58 Regulation of Adrenal Medullary Secretions Adrenal Cortex Hormones 1 Aldosterone: Type of mineralocorticoid Target tissues: kidneys Functions: regulate ion balance, causes Na+ and H2O to be retained and K+ to be secreted, indirectly involved with blood pressure and blood volume Figure 10.19 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 59 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 60 10  13/11/2024 Adrenal Cortex Hormones 2 Regulation of Cortisol Secretion Cortisol: Type of glucocorticoid Target tissues: most Functions: increases breakdown of fat and protein for energy uses reduces inflammatory and immune responses Figure 10.20 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 61 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 62 Adrenal Cortex Hormones 3 Pancreas Actions 1 Androgens: The pancreas is a mixed gland, with an exocrine portion and an endocrine portion. Target tissues: most tissues The exocrine portion of the pancreas secretes digestive Functions: enzymes. Males: secondary sexual characteristics The endocrine part of the pancreas consists of pancreatic Females: sex drive islets (Islets of Langerhans), which are dispersed throughout the exocrine portion of the pancreas. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 63 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 64 Pancreas Actions 2 Pancreas Structure The islets consist of three cell types, each of which secretes a separate hormone. Alpha cells secrete glucagon, beta cells secrete insulin, and delta cells secrete somatostatin. These three hormones regulate the blood levels of nutrients, especially glucose. ©Biophoto Associates/Science Source Figure 10.21 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 65 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 66 11  13/11/2024 Pancreas Hormones 1 Insulin Abnormalities Insulin: Diabetes mellitus: Target tissues: liver, skeletal muscle, adipose tissue Causes: too little insulin or faulty insulin receptors Functions: Symptoms: hyperglycemia, exaggerated appetite, excess urine, dehydration, thirst, fatigue regulates blood glucose levels after a meal glucose levels are high and insulin is secreted Type I: insulin dependent (daily injections required) extra glucose is stored in form of glycogen Type II: insulin independent, often found in obese people, can be treated with diet but can turn into type I Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 67 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 68 Pancreas Hormones 2 Regulation of Blood Glucose Levels Glucagon: Target tissues: liver Function: regulates blood glucose levels between meals glucose levels drop and glucagon is secreted glucagon allows glycogen to be broken down into glucose Figure 10.22 Access the text alternative for slide images. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 69 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 70 Testes Hormone Ovarian Hormones Testosterone: Estrogen/Progesterone: Target tissues: most tissues Target tissues: most tissues Functions: aids in sperm and reproductive organ Functions: involved in uterine and mammary gland development and function development and menstrual cycle Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 71 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 72 12  13/11/2024 Thymus Gland Hormone Pineal Gland Hormone Thymosin: Melatonin: Target tissues: immune system tissues Target tissues: hypothalamus Functions: promotes immune system development and Functions: plays a role in onset of puberty and controls function circadian rhythms. Light affects its function. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 73 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 74 Because learning changes everything. ® www.mheducation.com Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 13