Nervous System vs Endocrine System

Nervous System Endocrine 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 Glands Endocrine 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 hormonesNon-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 Secretionfrom 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.