Endocrine System Part 5B

© 2018 Pearson Education, Inc. Adrenal Glands Hormones of the adrenal cortex (continued) Glucocorticoids (including cortisone and cortisol) Produced by middle layer of adrenal cortex Promote normal cell metabolism Help resist long-term stressors by increasing blood glucose levels (hyperglycemic hormone) Anti-inflammatory properties Released in response to increased blood levels of ACTH © 2018 Pearson Education, Inc.

© 2018 Pearson Education, Inc. Adrenal Glands Hormones of the adrenal cortex (continued) Sex hormones Produced in the inner layer of the adrenal cortex Small amounts are made throughout life Most of the hormones produced are androgens (male sex hormones), but some estrogens (female sex hormones) are also formed © 2018 Pearson Education, Inc.

© 2018 Pearson Education, Inc. Adrenal Glands Adrenal medulla Produces two similar hormones (catecholamines) Epinephrine (adrenaline) Norepinephrine (noradrenaline) These hormones prepare the body to deal with short-term stress (“fight or flight”) by: Increasing heart rate, blood pressure, blood glucose levels Dilating small passageways of lungs © 2018 Pearson Education, Inc.

Figure 9.8 Microscopic structure of the adrenal gland. Capsule Mineralocorticoid- secreting area Kidney Glucocorticoid- secreting area Cortex Adrenal gland Adrenal cortex Medulla Cortex Sex hormone- secreting area Kidney Medulla Adrenal medulla

Figure 9.10 Roles of the hypothalamus, adrenal medulla, and adrenal cortex in the stress response. Short term More prolonged Stress Hypothalamus Releasing hormones Nerve impulses Spinal cord Corticotropic cells of anterior pituitary ACTH Adrenal cortex Preganglionic sympathetic fibers Adrenal medulla Mineralocorticoids Glucocorticoids Short-term stress response Long-term stress response Catecholamines (epinephrine and norepinephrine) Increased heart rate Increased blood pressure Liver converts glycogen to glucose and releases glucose to blood Dilation of bronchioles Changes in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity Increased metabolic rate Retention of sodium and water by kidneys Increased blood volume and blood pressure Proteins and fats converted to glucose or broken down for energy Increased blood sugar Suppression of immune system

© 2018 Pearson Education, Inc. Pancreatic Islets Pancreas Located in the abdomen, close to stomach Mixed gland, with both endocrine and exocrine functions The pancreatic islets (islets of Langerhans) produce hormones Insulin—produced by beta cells Glucagon—produced by alpha cells These hormones are antagonists that maintain blood sugar homeostasis © 2018 Pearson Education, Inc.

Figure 9.11a Pancreatic tissue. Stomach Pancreas (a)

Figure 9.11b Pancreatic tissue. Exocrine cells of pancreas Pancreatic islets (b)

Figure 9.11c Pancreatic tissue. Exocrine cells of pancreas Alpha () cells Figure 9.11c Pancreatic tissue. Capillaries Cord of beta () cells secreting insulin into capillaries (c)

© 2018 Pearson Education, Inc. Pancreatic Islets Insulin Released when blood glucose levels are high Increases the rate of glucose uptake and metabolism by body cells Effects are hypoglycemic Glucagon Released when blood glucose levels are low Stimulates the liver to release glucose to blood, thus increasing blood glucose levels © 2018 Pearson Education, Inc.

Uptake of glucose from blood is enhanced in most body cells. Figure 9.12 Regulation of the blood glucose level by a negative feedback mechanism involving pancreatic hormones. Tissue cells Insulin-secreting cells of the pancreas activated; release insulin into the blood. Insulin Pancreas Glucose Glycogen Blood glucose falls to homeostatic set point; stimulus for insulin release diminishes. Elevated blood sugar level Liver takes up glucose and stores as glycogen. IMBALANCE Stimulus Blood glucose level (e.g., after eating four jelly doughnuts) BALANCE: Normal blood glucose level (about 90 mg/100 ml) Stimulus Blood glucose level (e.g., after skipping a meal) IMBALANCE Blood glucose rises to homeostatic set point; stimulus for glucagon release diminishes. Low blood sugar level Glucagon-releasing cells of pancreas activated; release glucagon into blood. Glucose Glycogen Liver breaks down glycogen stores and releases glucose to the blood. Liver Glucagon

© 2018 Pearson Education, Inc. Gonads Gonads Produce sex cells Produce sex hormones © 2018 Pearson Education, Inc.

© 2018 Pearson Education, Inc. Gonads Ovaries Female gonads located in the pelvic cavity Produce eggs Produce two groups of steroid hormones Estrogens Progesterone Testes Male gonads suspended outside the pelvic cavity Produce sperm Produce androgens, such as testosterone © 2018 Pearson Education, Inc.

Figure 9.3 Location of the major endocrine organs of the body. Pineal gland Hypothalamus Pituitary gland Thyroid gland Parathyroid glands Thymus Adrenal glands Pancreas Ovary (female) Testis (male)

© 2018 Pearson Education, Inc. Gonads Estrogens Stimulate the development of secondary female characteristics Mature the female reproductive organs With progesterone, estrogens also: Promote breast development Regulate menstrual cycle © 2018 Pearson Education, Inc.

© 2018 Pearson Education, Inc. Gonads Progesterone Acts with estrogen to bring about the menstrual cycle Helps in the implantation of an embryo in the uterus Helps prepare breasts for lactation © 2018 Pearson Education, Inc.

© 2018 Pearson Education, Inc. Gonads Testes Produce several androgens Testosterone is the most important androgen Responsible for adult male secondary sex characteristics Promotes growth and maturation of male reproductive system Required for sperm cell production © 2018 Pearson Education, Inc.