Understanding the Endocrine System and Hormones

1. Chapter 15 The Endocrine System

2. secrete into bloodstream to hormones target tissues Introduction • The endocrine system includes the organs of the body that secrete hormones directly into body fluids such as blood • Regulates chemical reaction in cells and therefore control functions of the organs, tissues, and other cells Glands

3. Hormones • Endocrine glands • Ductless • Release hormones • Directly into target tissues • Into bloodstream to be carried to target tissues • Hormones – chemicals secreted by a cell that affect the functions of other cells

4. hormones Hormones (cont.) • Many are derived from steroidsthat easily cross the cell membrane • Examples of steroid hormones • Estrogen • Progesterone • Testosterone • Cortisol

5. Negative and Positive Feedback Loops • Control hormone levels • Negative feedback loop • Hormone release stops in response to decrease in stimulus • A person becomes dehydrated • Brain signals the release of Antidiuretic Hormone (ADH) • Kidneys retain water. • Kidneys excrete more urine until the concentration of fluids returns to normal.

6. Negative and Positive Feedback Loops(cont.) • Positive feedback loop • As long as stimulus is present, action of hormone continues • Infant nursing at mother’s breast  stimulates hypothalamus  stimulates posterior pituitary • Oxytocin released  stimulates milk production and ejection from mammary glands • Milk release continues as long as infant continues to nurse

7. Glands Hypothalamus • Hormones • Oxytocin – Stimulates contractions of uterus during labor • Antidiuretic hormone (ADH) – stimulates conservation of water during dehydration. • Hormones transported to the posterior pituitary for storage • Directs posterior pituitary to release hormones

8. Glands Pituitary Gland • Controlled by the hypothalamus • Located at the base of the brain • Anterior lobe secretes many hormones, including: • Growth hormone (GH) – controls cellular reproduction and regulates use of carbs and fats. • Thyroid-stimulating hormone (TSH) – stimulates the metabolism of ALL tissues in the body. • Folicle-stimulating hormone (FSH) – production of reproductive cells • Prolactin (PRL) – production of milk in mammals

9. Pituitary Gland(cont.) Oxytocin Posterior Lobe Females: causes contraction of the uterus and ejection of breast milk Males: stimulates contraction of the prostate and vas deferens during sexual arousal Antidiuretic hormone (ADH) Stimulates the kidneys to conserve water

10. Thyroid Gland and Parathyroid Glands Thyroid hormones Calcitonin T3 T4 Glands Thyroid Gland • Located below the larynx (houses vocal cords) • Divided into follicles that store some of the hormones Major hormones Stimulate protein synthesis and increase cellular energy production Lowers blood calcium levels by activating osteoblasts that build new bone tissue

11. Glands Thyroid Gland and Parathyroid Glands (cont.) • Parathyroid glands • Four located on the posterior surface of the thyroid gland • Secrete parathyroid hormone (PTH) • Raises blood calcium levels through activation of osetoclasts (dissolve bone) • As bone dissolves, calcium levels in blood increase

12. Glands Adrenal Glands • Located on top of each kidney • Divided into the adrenal medulla and adrenal cortex • Adrenal medulla • Central portion • Hormones • Epinephrine – Adrenaline, response to stress • Norepinephrine – works with epinephrine during stress events to bring the body back to homeostasis

13. Glands Pancreas • Located behind the stomach • Both exocrine gland and endocrine gland • Exocrine – secretes digestive enzymes into a duct leading to the small intestine • Endocrine – secretes hormones into bloodstream

14. Insulin Protein hormone secreted by the pancreas that stimulates cells to take up glucose • Glucose – primary source of cellular energy • Gives the brain energy for psychological processes. • Body converts the glucose into glycogen for long term storage of energy. What happens after you eat a large meal? • Pancreas secretes insulin, which results in a decrease in blood levels of glucose.

15. What is Diabetes?

16. Pineal body Small gland in the center of the brain Located between cerebral hemispheres Known by some cultures/religions as the “third eye”. Melatonin Regulates circadian rhythms May play a role in onset of puberty Glands Other Hormone-Producing Organs

17. The gonads - a Ovaries (female) Estrogen – stimulates secondary sex characteristics (breasts, hips, etc.) Progesterone – controls menstrual cycles and supports pregnancy. Both of these hormones are responsible for menstruation! Testes (male) Testosterone – responsible for development of primary and secondary sex characteristics (primary – reproductive organs; secondary – body hair, lower voice, etc.) Glands Other Hormone-Producing Organs(cont.)

18. The Stress Response • Stressor • Any stimulus that produces stress • Types • Physical factors • Psychological factors • Positive stimuli

19. The Stress Response (cont.) • Physiologic response to stress caused by hormone release • Hypothalamus acts as a connector from the nervous system to the endocrine system. • Hypothalamus senses the “stress” stimulus • The adrenal gland secretes epinephrine and norepinephrine • The “fight or “flight” response is generated • The body returns to homeostasis