Chapter 10

Regulating Body Function Working closely with your nervous system is the endocrine system, a chemical communication system that regulate many body functions.

Exocrine vs Endocrine Exocrine Glands Endocrine secrete their products into ducts that empty onto a surface or into a cavity. Ex: Sweat glands and salivary glands Ductless glands. They secrete chemicals (hormones) into intracellular spaces.

Regulating Body Function A gland is a group of cells, or an organ, that secretes a chemical substance. The endocrine glands secrete chemicals called hormones directly into the bloodstream. The blood carries the hormones directly to the tissue they are targeted to affect. Some hormones are produced continuously, while others are produced only at certain times.

Regulation of Hormone Secretion Negative Feedback Positive Feedback Homeostatic control mechanism that reverses what is happening in the body More common than positive feedback. Ex: Insulin, Body Temperature, Blood Pressure Amplifies changes rather than reverses them. Ex: Labor – amplified contractions.

Mechanisms of Hormone Action Nonsteroid Hormones Steroid Hormones Second messenger mechanism: nonsteroid hormones serve as 1 st messenger between gland and cells; Another molecule will then act as a 2 nd messenger providing communication within the target cell Lipid-soluble Can pass through cell membrane of target cell Bind with receptors on the nucleus and act on DNA

Endocrine System

Pituitary The pituitary gland at the base of the brain is a gland that signals other endocrine glands to produce hormones when needed. It is also known as the “Master Gland” and is located at the base of the brain. It secretes several hormones. These regulate the thyroid gland, adrenal glands, and kidneys- plus your growth and development. It produces growth hormones.

Pituitary Anterior Posterior TSH Thyroid stimulating ACTH Adrenocorticotropic FSH Follicle-stimulating LH luteinizing GH growth Prolactin ADH Anti-duretic Oxytocin

Hypothalamus The hypothalamus is a vital neuroendocrine and autonomic control center beneath the thalamus. Secretes: Releasing hormones Anterior pituitary Inhibiting hormones Posterior pituitary

Parathyroid The parathyroid glands direct the distribution of certain minerals in your body. Increase Ca + in blood Secretes Parathyroid hormone or PTH

Pancreas The pancreas is part of two body systems- the digestive system and the endocrine system. It is located behind the stomach and supplies the small intestine with digestive juice. It produces insulin and contains small clusters of cells called the islets of Langerhans, which control blood sugar levels. It produces insulin.

Pancreas

Thymus The thymus gland is located in the mediastinum. It is a vital part of the body’s immune system. Produces thymosin

Pineal Gland The pineal gland is located in the third ventricle of the brain. It produces melantonin.

Thyroid The thyroid gland is located where the larynx and trachea meet. It regulates the chemical reactions of nutrients in the cells. It produces thyroxine.

Adrenal The adrenal glands are located on your kidneys. They secrete hormones that help the body maintain its levels of sodium and water, aid the digestive process, and control your body’s response to emergencies. It produces adrenaline.

Adrenal

The Body’s Response to Stress When your brain recognizes a stressful situation, your adrenal glands responds by releasing the hormone adrenaline. This hormone prepares your body to respond to stress.

Reproductive During adolescence, the endocrine system plays an important role in growth and development.

Ovaries The ovaries are the female reproductive glands. They control the development of secondary sex characteristics during adolescence. It produces estrogen.

Placenta The placenta anchors the developing fetus to the uterus and provides a “bridge” for the the exchange of nutrients and waste products between the mother and the developing baby.

Testes The testes are the male reproductive glands. They control the development of secondary sex characteristics during adolescence. It produces testosterone.

Endocrine System

Secretions of Hormones Hyposecretion Hypersecretion Production of too little hormone by a diseased gland Production of too much hormone by a diseased gland

Diabetes Diabetes mellitus is a disease that may be caused by inadequate insulin production by the pancreas. Symptoms include: lack of energy weight loss extreme thirst frequent urination

THYROID HYPOTHRYOIDISM HYPERTHYROIDISM Underactive thyroid gland can cause a dull facial expression, hoarse voice, facial puffiness, coarse, dry skin and hair, and weight gain. Goiter- caused by low dietary iodine intake Cretinsim- when hyposecretion occurs in infants/toddlers Overactive thyroid gland produces symptoms that may include protrusion of eyeballs, warm, moist skin, trembling hands, nervousness, increased sweating, disturbed sleep, and weight loss.

Growth Hormone hyposecretion hypersecretion Dwarfisim Gigantism Acromegaly results when GH is secreted too much after adolescents.

Parathyroid Parathyroid hormone (PTH) and vitamin D help manage calcium balance in the body Calcium is important to many body functions, including: Bone formation Hormone release Muscle contraction Nerve and brain function

Parathyroid and Nerve Cells

Parathyroid hypersecretion hyposecretion Results in hypercalcemia Causes several abdominal, muscle, kidney and psychological symptoms Results in hypocalcemia Symptoms include: Petechiae (red spots on skin) Strong muscle contractions of the hand (cramping) Life threatening ECG changes