Endocrine System

ENDOCRINE SYSTEM The endocrine system is made up of the cells, tissues, and organs that secrete hormones into body fluids such as the blood stream.

Hormones diffuse into the bloodstream, and eventually act on cells called target cells.

General Characteristics of the Endocrine System Glandular cells of the endocrine system release hormones into the bloodstream, which carries these messenger molecules everywhere. The endocrine system is precise because only target cells can respond to a hormone. Target cells have specific receptors that other cells do not have.

The endocrine system helps regulate metabolic processes by: Controlling the rates of certain chemical reactions Aid in the transport of substances across membranes Help regulate water and electrolyte balances Playing a vital role in reproduction, development, and growth

Major Endocrine Glands Pituitary gland Thyroid gland Parathyroid gland Adrenal gland Pancreas Pineal gland Reproductive glands Kidneys Thymus

Pituitary Gland Located at the base of the brain, where a pituitary stalk attaches it to the hypothalamus.

Growth hormone (GH) Stimulates cells to increase in size and divide more frequently Pituitary dwarfism insufficient secretion of growth hormone; body parts normally proportioned, mental development is normal

Gigantism oversecretion during childhood; usually a result of a tumor which can cause oversecretion of other pituitary hormones; often has several metabolic disturbances

Acromegaly oversecretion during adulthood; enlarged heart, bones, thyroid gland, facial features, etc

Prolactin (PRL) Milk production in lactating women

Thyroid stimulating hormone (TSH) Controls thyroid gland secretions

Adrenocorticotropic hormone (ACTH) Controls the hormones of the adrenal gland

Follicle stimulating hormone (FSH)/ Luteinizing hormone (LH) Exert their actions on the gonads

Antidiuretic hormone (ADH) Decreases urine formation. Regulates the water concentration of body fluids.

Diabetes insipidus (too little ADH) person may produce as much as 25-30 liters of very dilute urine per day, and solute concentrations in body fluids rise.

Oxytocin (OT) Causes contraction of the uterine walls during childbirth Contracts specialized cells associated with the milk- producing glands and their ducts. May be given to ‘induce’ labor (Pitocin) and/or following childbirth to minimize risk of hemorrhage

Thyroid Gland Located below the larynx, anterior to the trachea Consists of two broad lobes connected by an isthmus Made of many secretory parts called follicles.  

Thyroxine (T4) & Triiodothyronine (T3) Regulate metabolism of carbohydrates, proteins, and lipids Basal metabolic rate how many calories the body must consume at rest in order to maintain life Required for normal growth and development Essential to nervous system maturation

Calcitonin Lowers blood calcium and phosphate ion concentration Inhibits release of calcium and phosphate ions from the bones Increases excretion of calcium and phosphate ions by kidneys

HYPOthyroidism Common among older adults Fatigue and weight gain  

HYPERthyroidism Elevated metabolic rate, restlessness, and overeating Eyes protrude because of swelling behind them Produces a bulge in the neck because the thyroid gland enlarges

11.9 Pancreas Endocrine (secretes hormones) and exocrine (digestive juices) gland Located posterior the stomach  

Hormones of the Pancreatic Islets Glucagon Stimulates the liver to break down glycogen and convert certain noncarbohydrates, such as amino acids, into glucose Raises blood sugar concentration

Insulin Stimulates the liver to form glycofen from glucose and inhibits conversion of noncarbohydrates Decreases blood glucose (sugar) concentration

11.10 Other Endocrine Glands Pineal Gland Located deep between the cerebral hemispheres, attached to the thalamus Produces Melatonin: Produced in response to light conditions received by the retinas of the eyes. Involved in regulation of circadian rhythms of the body Thymus Located posterior to the sternum between the lungs Thymosin- important in immunity   Reproductive Glands Testes  produces testosterone Ovaries  produces estrogen & progesterone Placenta produces estrogen, progesterone & gonadotropin

11.11 Stress and Health Physical factors include extreme heat or cold, decreased oxygen, infections, injuries, prolonged heavy exercise, and loud noises.   Psychological factors include thoughts about real or imagined dangers, personal losses, and unpleasant social interactions or feelings of anger, fear, grief, anxiety, depression, and guilt. Responses to Stress USE FIGURE 11.18 Hypothalamus helps prepare the body for “fight or flight” by triggering sympathetic impulses to various organs stimulates epinephrine release, intensifying the sympathetic responses secretes corticotropin-releasing hormones, which sets into motion more lasting responses to stress