Chapter 9 The Endocrine System Lecture Presentation by Patty Bostwick-Taylor Florence-Darlington Technical College
Intro to the Endocrine System Chief Complaint:8-year-old girl with excessive thirst, frequent urination, and weight loss. History: Cindy Mallon, an 8-year-old girl in previously good health, has noticed that, in the past month, she is increasingly thirsty. She gets up several times a night to urinate, and finds herself gulping down glass-fulls of water. At the dinner table, she seems to be eating twice as much as she used to, yet she has lost 5 pounds in the past month. In the past three days, she has become nauseated, vomiting on three occasions, prompting a visit to her pediatrician.
Lab Results At the doctor's office, blood and urine samples are taken. The following lab results are noted: blood glucose level = 545 mg/dl (normal = 50-170 mg/dl) blood ph level = 7.23 (normal = 7.35-7.45) urine = tested positive for glucose and for acetone / acetoacetate (i.e. ketone bodies) (normally urine is free of glucose and ketone bodies) Why is her blood-glucose level elevated? Why is she always thirsty?
The Endocrine System Second controlling system of the body after N.S. Uses chemical messengers (hormones) that are released into the blood Hormones control several major processes: Reproduction Growth and development Mobilization of body defenses Maintenance of much of homeostasis Regulation of metabolism
Hormone Overview Hormones are produced by specialized cells Cells secrete hormones into extracellular fluids Blood transfers hormones to target sites These hormones regulate the activity of other cells
Control of Hormone Release Hormone levels in the blood are maintained mostly by negative feedback A stimulus or low hormone levels in the blood triggers the release of more hormone Hormone release stops once an appropriate level in the blood is reached
Feedback System Blood Glucose https://www.fastday.com/wp-content/uploads/2014/04/insulin1.jpg
Hormone Action Hormones affect only certain tissues or organs (target cells or target organs) Target cells must have specific protein receptors Hormone binding alters cellular activity
The Chemistry of Hormones Hormones are classified chemically as Amino acid based, which includes: Proteins Peptides Amines Steroids made from cholesterol (lipid) Prostaglandins made from highly active lipids that act as local hormones
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Hormone Action Hormones arouse cells, or alter cellular activity. Typically, one or more of the following occurs: 1. Changes in plasma membrane permeability or electrical state 2. Synthesis of proteins, such as enzymes 3. Activation or inactivation of enzymes 4. Stimulation of mitosis 5. Promotion of secretory activity
The Chemistry of Hormones Hormones act by two mechanisms: 1. Direct gene activation 2. Second-messenger system
Direct Gene Activation (Steroid Hormone Action) 1. Steroid hormones diffuse through the plasma membrane of target cells 2. Steroid hormones enter the nucleus 3. Steroid hormones bind to a specific protein within the nucleus 4. Hormone-receptor complex binds to specific sites on the cell s DNA 5. Certain genes are activated that result in 6. Synthesis of new proteins
Figure 9.1a Mechanisms of hormone action. Slide 1 Steroid hormone Cytoplasm 1 2 Nucleus Receptor protein 3 Hormone-receptor complex 4 New protein DNA mrna 5 Plasma membrane of target cell 6 (a) Steroid hormone action
Figure 9.1a Mechanisms of hormone action. Steroid hormone Cytoplasm 1 Nucleus Slide 2 (a) Steroid hormone action
Figure 9.1a Mechanisms of hormone action. Slide 3 Steroid hormone Cytoplasm 1 2 Nucleus Receptor protein (a) Steroid hormone action
Figure 9.1a Mechanisms of hormone action. Slide 4 Steroid hormone Cytoplasm 1 2 Nucleus Receptor protein 3 Hormone-receptor complex (a) Steroid hormone action
Figure 9.1a Mechanisms of hormone action. Slide 5 Steroid hormone Cytoplasm 1 2 Nucleus Receptor protein 3 Hormone-receptor complex 4 DNA (a) Steroid hormone action
Figure 9.1a Mechanisms of hormone action. Slide 6 Steroid hormone Cytoplasm 1 2 Nucleus Receptor protein 3 Hormone-receptor complex 4 DNA mrna 5 (a) Steroid hormone action
Figure 9.1a Mechanisms of hormone action. Slide 7 Steroid hormone Cytoplasm 1 2 Nucleus Receptor protein 3 Hormone-receptor complex 4 New protein DNA mrna 5 Plasma membrane of target cell 6 (a) Steroid hormone action
Second-Messenger System (Nonsteroid Hormone Action) 1. Hormone (first messenger) binds to a membrane receptor 2. Activated receptor sets off a series of reactions that activates an enzyme 3. Enzyme catalyzes a reaction that produces a second-messenger molecule (such as cyclic AMP, or camp) 4. Oversees additional intracellular changes to promote a specific response in the target cell
Figure 9.1b Mechanisms of hormone action. Slide 1 Nonsteroid hormone (first messenger) Enzyme Cytoplasm ATP 1 2 3 camp Second messenger Receptor protein Plasma membrane of target cell 4 Effect on cellular function, such as glycogen breakdown (b) Nonsteroid hormone action
Figure 9.1b Mechanisms of hormone action. Slide 2 Nonsteroid hormone (first messenger) Cytoplasm 1 Receptor protein (b) Nonsteroid hormone action
Figure 9.1b Mechanisms of hormone action. Slide 3 Nonsteroid hormone (first messenger) Enzyme Cytoplasm 1 2 Receptor protein (b) Nonsteroid hormone action
Figure 9.1b Mechanisms of hormone action. Slide 4 Nonsteroid hormone (first messenger) Enzyme Cytoplasm ATP 1 2 3 camp Second messenger Receptor protein (b) Nonsteroid hormone action
Figure 9.1b Mechanisms of hormone action. Slide 5 Nonsteroid hormone (first messenger) Enzyme Cytoplasm ATP 1 2 3 camp Second messenger Receptor protein Plasma membrane of target cell 4 Effect on cellular function, such as glycogen breakdown (b) Nonsteroid hormone action
Endocrine Gland Stimuli The stimuli that activate endocrine glands fall into three major categories: 1. Hormonal 2. Humoral 3. Neural
Hormonal Stimuli of Endocrine Glands Most common stimulus Endocrine organs are activated by other hormones Example: Anterior pituitary hormones travel to target glands, such as the thyroid gland, to prompt the release of a particular hormone, such as thyroid hormone
Figure 9.2a Endocrine gland stimuli. (a) Hormonal stimulus 1 The hypothalamus secretes hormones that Hypothalamus 2 stimulate the anterior pituitary gland to secrete hormones that Anterior pituitary gland Thyroid gland Adrenal cortex Gonad (testis) 3 stimulate other endocrine glands to secrete hormones
Humoral Stimuli of Endocrine Glands Changing blood levels of certain ions and nutrients stimulate hormone release Humoral indicates various body fluids, such as blood and bile Examples: Parathyroid hormone and calcitonin are produced in response to changing levels of blood calcium levels Insulin is produced in response to changing levels of blood glucose levels
Figure 9.2b Endocrine gland stimuli. (b) Humoral stimulus 1 Capillary blood contains low concentration of Ca 2+, which stimulates Capillary (low Ca 2+ in blood) Thyroid gland (posterior view) Parathyroid glands PTH Parathyroid glands 2 secretion of parathyroid hormone (PTH) by parathyroid glands)
Neural Stimuli of Endocrine Glands Nerve impulses stimulate hormone release Most are under the control of the sympathetic nervous system Examples: The release of norepinephrine and epinephrine by the adrenal medulla
Figure 9.2c Endocrine gland stimuli. (c) Neural stimulus 1 Preganglionic sympathetic fiber stimulates adrenal medulla cells CNS (spinal cord) Preganglionic sympathetic fibers Medulla of adrenal gland Capillary 2 to secrete catecholamines (epinephrine and norepinephrine)