Chapter 6 Chemical Regulation PowerPoint Lectures for Biology: Concepts and Connections, Fifth Edition Campbell, Reece, Taylor, and Simon Testosterone and Male Aggression: Is There a Link? Among male animals, the primary role of testosterone and other androgens Is to promote the development and maintenance of male reproductive anatomy and secondary sexual characteristics Does testosterone also promote aggressive behavior? Lectures by Chris Romero Research on cichlid fish Has shown that androgen levels in males increase during displays of territorial behavior Establishing links between androgens and human male aggression Has been found to be problematic Does testosterone play a role in aggressive behavior? THE NATURE OF CHEMICAL REGULATION 6. Chemical signals coordinate body functions Hormones are secreted by Hormones are chemical signals, usually carried in the blood That cause specific changes in target s Secretory vesicles Endocrine glands and neurosecretory s Neurosecretory Endocrine Hormone Hormone Figure 6.A, B
All hormone-secreting s make up the endocrine system Which works with the nervous system in regulating body activities A few chemicals serve both as hormones in the endocrine system And as chemical signals in the nervous system signals Neurotransmitter Figure 6.C 6. Hormones affect target s by two main signaling mechanisms Water-soluble hormones such as proteins and amines Bind to plasmamembrane receptors on target s Water-soluble hormone (epinephrine) Relay 3 Glycogen Receptor protein Plasma membrane Signal transduction pathway Glucose Cellular response (in this example, glycogen breakdown) Steroid hormones, such as the sex hormones estrogen and testosterone Diffuse through the plasma membrane of target s and bind to intraular receptors Lipid-soluble hormone (testosterone) 3 Nucleus DNA 4 mrna Receptor protein Hormonereceptor complex Transcription New protein Figure 6.A Figure 6.B Cellular response: activation of a gene and synthesis of new protein THE VERTEBRATE ENDOCRINE SYSTEM 6.3 Overview: The vertebrate endocrine system The vertebrate endocrine system Consists of more than a dozen glands secreting more than 50 hormones Some glands are specialized for hormone secretion only While others also do other jobs Pineal gland Thyroid gland Parathyroid glands Thymus Adrenal glands (atop kidneys) Pituitary gland Pancreas Ovary (female) Figure 6.3 Testes (male)
Some hormones have a very narrow range of targets and effects While others have numerous effects on many kinds of target s 6.4 The hypothalamus, closely tied to the, connects the nervous and endocrine systems The hypothalamus exerts master control over the endocrine system By using the gland to relay directives to other glands Brain Posterior Anterior Figure 6.4A Bone Releasing and inhibiting hormones from the hypothalamus Control the secretion of several other hormones The posterior Secretes oxytocin and antidiuretic hormone (ADH) Hormone Neurosecretory Posterior Anterior Oxytocin ADH Figure 6.4B Uterine muscles Mammary glands Kidney tubules The anterior Secretes TSH, ACTH, FSH and LH, growth hormone, prolactin, and endorphins Neurosecretory Secretion of thyroxine by the thyroid gland Is controlled by a negative-feedback mechanism Inhibition Releasing hormones from hypothalamus TRH Anterior Inhibition Endocrine s of the anterior TSH Pituitary hormones Thyroid TSH ACTH FSH and LH Growth hormone (GH) Prolactin (PRL) Endorphins Figure 6.4C Thyroid Adrenal Testes or Entire Mammary Pain cortex ovaries body glands receptors (in mammals) in the brain Figure 6.4D Thyroxine 3
HORMONES AND HOMEOSTASIS 6.5 The thyroid regulates development and metabolism Thyroid imbalance Can cause disease Two hormones from the thyroid gland, T 4 and T 3 Regulate an animal s development and metabolism Figure 6.5A Negative feedback Maintains homeostatic levels of T 4 and T 3 in the blood Anterior TRH No inhibition No inhibition 6.6 Hormones from the thyroid and parathyroids maintain calcium homeostasis calcium level is regulated by a tightly balanced antagonism Between calcitonin from the thyroid and parathyroid hormone from the parathyroid glands TSH Thyroid No iodine Insufficient T 4 and T 3 produced Figure 6.5B Thyroid grows to form goiter Calcium homeostasis Calcitonin Thyroid gland releases Stimulates Reduces calcitonin Ca + deposition Ca + uptake in bones in kidneys Ca + falls Rising blood Ca + level Homeostasis: Normal blood (imbalance) calcium level (about 0 mg/00ml) Falling blood Ca + level (imbalance) 6.7 Pancreatic hormones regulate blood glucose levels The pancreas secretes two hormones, insulin and glucagon That control blood glucose Ca + rises Active vitamin D Parathyroid glands release parathyroid hormone (PTH) Stimulates Ca + release from bones Increases Ca + uptake in kidneys Increases Ca + uptake in intestines PTH Parathyroid gland Figure 6.6 4
glucose (mg/00ml) Insulin Signals s to use and store glucose Glucagon Causes s to release stored glucose into the blood Glucose homeostasis Insulin Beta s of pancreas stimulated to release insulin into the blood High blood glucose level Rising blood glucose level (e.g., after eating a carbohydrate-rich meal) Body s take up more glucose Liver takes up glucose and stores it as glycogen Homeostasis: Normal blood glucose level (about 90 mg/00ml) glucose level declines to a set point; stimulus for insulin release diminishes Declining blood glucose level (e.g., after skipping a meal) Figure 6.7 glucose level rises to set point; stimulus for glucagon release diminishes Liver breaks down glycogen and releases glucose to the blood Glucagon Alpha s of pancreas stimulated to release glucagon into the blood CONNECTION 6.8 Diabetes is a common endocrine disorder Diabetes mellitus Results from a lack of insulin or a failure of s to respond to it Diabetes can be detected By a test called a glucose tolerance test 400 350 300 50 Diabetic 00 50 00 Normal 50 0 Figure 6.8 0 3 4 5 Hours after glucose ingestion 6.9 The adrenal glands mobilize responses to stress Hormones from the adrenal glands Help maintain homeostasis when the body is stressed signals from the hypothalamus Stimulate the adrenal medulla to secrete epinephrine and norepinephrine, which quickly trigger the fight-or-flight responses 5
ACTH from the causes the adrenal cortex to secrete glucocorticoids and mineralocorticoids Which boost blood pressure and energy in response to long-term stress How the adrenal glands control our responses to stress Kidney Adrenal gland Adrenal medulla Adrenal cortex Spinal cord (cross section) signals ACTH Stress Releasing hormone Anterior Adrenal medulla ACTH Adrenal cortex Epinephrine and norepinephrine Mineralocorticoids Glucocorticoids Short-term stress response Long-term stress response Figure 6.9. Glycogen broken down to glucose; increased blood glucose. Increased blood pressure 3. Increased breathing rate 4. Increased metabolic rate 5. Change in blood-flow patterns, leading to increased alertness and decreased digestive and kidney activity Mineralocorticoids. Retention of sodium ions and water by kidneys. Increased blood volume and blood pressure Glucocorticoids. Proteins and fats broken down and converted to glucose, leading to increased blood glucose. Immune system may be suppressed CONNECTION 6.0 Glucocorticoids offer relief from pain, but not without serious risks Glucocorticoids relieve inflammation and pain But they can mask injury and suppress immunity 6. The gonads secrete sex hormones Estrogens, progestins, and androgens are steroid sex hormones Produced by the gonads in response to signals from the hypothalamus and Figure 6.0 Estrogens and progestins Stimulate the development of female characteristics and maintain the female reproductive system Androgens, such as testosterone Trigger the development of male characteristics 6