Nervous System vs Endocrine System Nervous SystemEndocrine System Nt’s act on a specific cell right next to it Hormone can act on nearby cell or cell in another part of body Nt’s have their effects within milliseconds Hormones have effects in minutes or days Effects of Nt’s are short- lived Effects of Nt’s can last hours, days or years

Endocrine vs Exocrine Glands Exocrine GlandsEndocrine Glands Secrete products into ducts Secrete products into extracellular fluid Secretions go into body cavities, lumen of organ or body’s surface Secretions (hormones) act on nearby cell or more commonly go into blood vessels to act on cell in another part of body E.g. sweat glands, lacrimal glands, sebaceous glands, etc E.g. pituitary gland, thyroid gland, pancreas, etc.

Endocrine Glands Ductless Produce chemical messenger Hormone released into blood stream

Exocrine Glands Have ducts Produce a variety of substances (sweat, oil, enzymes) Release chemicals through ducts

What makes a hormone a hormone? 1. Secreted by endocrine gland 2. Released into circulatory system 3. Travels to and acts on specific target cells.

Major Endocrine Glands

Classification of Hormones Steroid Hormones – fat soluble, made from cholesterol. Ex. Sex hormones Non-Steroidal Hormones Protein Hormones – made from amino acids, usually from tyrosine, smaller than steroid hormones. Peptide Hormones- chains of amino acids Very diverse group

The major categories of non- steroid hormones are protein hormones, glycoprotein hormones, peptide hormones, and amino acid derivative hormones.

Classification of Hormones 3 major types of hormones: 1. Amino Acid Derivatives 2. Peptide Hormones 3. Lipid Derivatives

Protein Hormones Much faster action than steroid hormones Do not enter the target cell Ex. Adrenalin

Mechanisms of Action (How Hormones Work) Second Messengers: Genes:

Hypothalamus Location: Diencephalon Structure: Neurons and neuroglia Hormones: Releasing hormones, ADH, oxytocin, Direct action on adrenal medulla

Hypothalamic Control of Hormone Secretion from the Adenohypophysis Hypothalamus regulates secretion of hormones Secretes releasing factors to release hormones Secretes inhibiting hormones to turn off secretion of hormones

Hypothalamus Relationship to Anterior & Posterior Pituitary

Hypothalamus Summary

The Pituitary Gland (Hypophysis) Secretes nine major hormones Attached to the hypothalamus by the infundibulum Two basic divisions of the pituitary gland Anterior pituitary gland Posterior pituitary gland

The Pituitary Gland Figure 25.3a-c

Anterior Pituitary Gland Location: Attached to hypothalamus by infundibulum Structure: endocrine- secreting cells Hormones: Tropic Hormones (ACTH, TSH, FSH, LH) and GH, PRL, MSH

Posterior Pituitary Gland Location: Attached to hypothalamus by infundibulum Structure: Axons that extend from the hypothalamus Releases (does not make) two hormones Antidiuretic hormone (ADH) Oxytocin

The Thyroid Gland Location: anterior neck Structure: Follicles and areolar connective tissue Hormones: thyroid hormone (TH) and calcitonin

The Thyroid Gland

The Parathyroid Gland Location: Posterior surface of the thyroid gland Structure: endocrine cells Hormones: Parathyroid hormone

The parathyroid hormone helps maintain calcium homeostasis. It acts on bone, kidney, and intestinal cells to increase the release of calcium into the blood.

The Adrenal Gland

The Adrenal Glands Location: Superior surface of the kidneys Structure: Inner adrenal medulla and outer adrenal cortex Nerve supply is almost exclusively sympathetic fibers Hormones in Adrenal Cortex: Glucocorticoids (e.g. cortisol, corticosterone, and cortixon), Mineralocorticoids (e.g. aldosterone), and androgens Hormones in Adrenal Medulla: Epinephrine and norepinephrine

The Adrenal Cortex Figure 25.9a

Antidiuretic hormone acts to reduce the volume of urine. It does this by causing water to be reabsorbed from the tubules of the kidney and returned to the blood. This increases the water content of the blood and reduces the volume of urine.

The Pancreas Location: Posterior abdominal wall along duodenum Structure: Both endocrine and exocrine cells (secrete digestive enzymes) Hormones: Glucagon and insulin

Alpha cells in the pancreatic islets produce glucagon. Beta cells produce insulin. Delta cells produce somatostatin, and pancreatic polypeptide cells produce pancreatic polypeptide.

Glucagon and Insulin

Diabetes Mellitus This is a disease caused by elevated glucose levels 2 Types of diabetes: Type I diabetes (10% of cases) Type II diabetes (90% of cases)

Type I Diabetes (10% of cases) Develops suddenly, usually before age 15 Caused by inadequate production of insulin because T cell-mediated autoimmune response destroys beta cells Controlled by insulin injections

Type II diabetes (90% of cases) Usually occurs after age 40 and in obese individuals Insulin levels are normal or elevated but there is either a decrease in number of insulin receptors or the cells cannot take it up. Controlled by dietary changes and regular exercise

Pituitary Disorders Gigantism – hypersecretion of GH in children Pituitary dwarfism – hyposecretion of GH Diabetes insipidus – pars nervosa does not make enough ADH

Disorders of the Thyroid Gland Grave’s disease – most common type of hyperthyroidism Immune system makes abnormal antibodies Stimulates the oversecretion of TH by follicle cells Leads to nervousness, weight loss, sweating, and rapid heart rate

Disorders of the Thyroid Gland Myxedema – adult hypothyroidism Antibodies attack and destroy thyroid tissue Low metabolic rate and weight gain are common symptoms Endemic goiter – due to lack of iodine in the diet Cretinism – hypothyroidism in children Short, disproportionate body, thick tongue and mental retardation

Disorders of the Adrenal Cortex Cushing’s syndrome – caused by hypersecretion of glucocorticoid hormones Addison’s disease – hyposecretory disorder of the adrenal cortex Deficiencies of both mineralocorticoids and glucocorticoids

Control of Hormones Release: Three Mechanisms Figure 25.2a-c

Oxytocin has two positive feedback mechanisms associated with it. The first is the release of milk. The mechanical and psychological stimulation of the baby's suckling triggers the release of oxytocin. This provides more milk, which allows the baby to continue to suckle, which in turn stimulates the release of more oxytocin. The other feedback mechanism is the stimulation of uterine contractions. Once uterine contractions begin, they push down on receptors in the pelvis, which triggers the release of more oxytocin, which causes more uterine contractions.