ch. 18 - Endocrine System

Endocrine System

Regulates cells using hormones, with wide effects and targets all cells

Endocrine Gland

Specialized organ making hormones, secreting into blood, without ducts

Exocrine Gland

Secretes products into ducts and into the body surface, not part of endocrine system

What are examples of exocrine glands?

- Saliva (salivary glands)
- Skin oil (sebaceous glands)
- Tears (lacrimal glands)
- Digestive enzymes (digestive glands of the stomach)

What is an example of a gland that had both exocrine & endocrine functions?

pancreatic gland

What are some organs that are not specialized endocrine glands, but produce hormones?

- kidneys
- heart
- stomach
- liver
- placenta

Paracrine hormones

hormones with local effects, affecting only some tissues

Endocrine hormones

hormones that secrete into the blood and affect cells at other locations in the body

Antagonistic Effect

Hormones producing opposite effects, e.g., insulin and glucagon

Synergistic Effect

Two different hormones that produce the same effect, e.g., testosterone and growth hormone

Permissive Effect

One hormone required for another to have an effect, e.g., thyroid hormone for GH

What is an example of negative feedback involving hormones?

Cortisol secretion stimulated by ACTH, which then suppresses CRH production

What is an example of positive feedback involving hormones?

Uterine stretch stimulates oxytocin release, causing contractions and more stretching

Target Cell

Cell with receptors for a particular hormone

What are 2 physiological processes examples regulated primarily by the endocrine system?

growth & metabolism

What hormones control growth?

GH (growth hormone), testosterone, & thyroxin

What hormones control metabolism?

insulin & leptin

Water-Soluble Hormones

Hydrophilic (they cannot pass through the cell), bind to receptors on the outside of cell membrane, e.g., insulin & GH

Lipid-Soluble Hormones

Hydrophobic, pass through cell membrane, bind to receptors inside the cell, e.g., steroid hormones, thyroid hormones

Hormone Receptor

Binds to a hormone for an action/response to take effect.
- located outside for water-soluble hormones and located inside the cell for lipid-soluble hormones

Protein hormone are made by

ribosomes on the rough ER

Steroid hormone are synthesized by

special enzymes, most located on the smooth ER

Second Messengers

special molecules made inside cells in response to hormone binding to its receptor, activating enzymes or membrane channels

Hypothalamus in relation to the endocrine system

Is the main link between nervous and endocrine system, controls the pituitary by secreting "release hormones" that are produced by special hypothalamic neurons called neuro-endocrine cells

Which hormones does hypothalamus produce?

- Antidiuretic Hormone (ADH)
- Oxytocin
- Gonadotropin-Releasing Hormone (GnRH)
- Thyrotropin-Releasing Hormone (TRH)
- Corticotropin-Releasing Hormone (CRH)
- Prolactin-Inhibiting Hormone (PIH)
- Prolactin-Releasing Hormone (PRH)
- Growth Hormone-Releasing Hormone (GHRH)
- Growth Hormone-Inhibiting Hormone (GHIH)

Antidiuretic Hormone (ADH)

controls water excretion

Oxytocin

controls milk ejection and stimulates birthing contractions

Gonadotropin-Releasing Hormone (GnRH)

stimulates secretion of Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH)

Thyrotropin-Releasing Hormone (TRH)

stimulates secretion of thyroid-stimulating hormone (TSH)

Corticotropin-Releasing Hormone (CRH)

stimulates secretion of adrenocorticotropic hormone (ACTH)

Prolactin-Inhibiting Hormone (PIH)

is dopamine, suppresses secretion of prolactin

Prolactin-Releasing Hormone (PRH)

stimulates secretion of prolactin

Growth Hormone-Releasing Hormone (GHRH)

also known as somatocrinin, stimulates secretion of growth hormone (GH)

Growth Hormone-Inhibiting Hormone (GHIH)

also known as somatostatin, suppresses secretion of growth hormone (GH)

Pituitary Gland

Releases hormones, with anterior and posterior parts

Anterior pituitary

secretes hormones that regulate a wide range of body activities, from growth to reproduction

Posterior pituitary

store and release hormones, does not synthesize

What are the pituitary hormones?

- Growth hormone (GH)
- Prolactin
- Adrenocorticotropic Hormone (ACTH)
- Thyroid-Stimulating Hormone (TSH)
- Luteinizing Hormone (LH)
- Follicle-Stimulating Hormone (FSH)
- Antidiuretic Hormone (ADH)
- Oxytocin

Growth Hormone (GH)

promotes growth throughout the body

Prolactin

Controls milk production

Adrenocorticotropic Hormone (ACTH)

controls secretion of adrenocorticoid hormones

Thyroid-Stimulating Hormone (TSH)

Controls secretion of thyroid hormones

Follicle-Stimulating Hormone (FSH) & Luteinizing Hormone (LH)

controls ovaries and testes functions

The posterior pituitary secretes 2 hormones. Which structure are these hormones synthesized?

Oxytocin and Antidiuretic Hormone (ADH) are synthesized in the hypothalamus, then stored and released from the posterior pituitary gland.

Which 2 hormones is lactation regulated by?

prolactin & oxytocin

Which hormones play a role in stress response?

- Adrenalin (epinephrin) & Noradrenalin (norepinephrine): released during stress and enhance effects of sympathetic responses
- Glucocorticoids = Cortisol: controls glucose metabolism and long-term stress response

Produced in the adrenal gland

Thyroid hormones (T3, T4, Calcitonin)

regulate oxygen use and metabolic rate, cellular metabolisms, and growth and development

Thyroxin (T4)

has 4 iodines; regulates metabolisms, growth and development, and the activity of the nervous system

Triiodothyronine (T3)

a little stronger than T4, has 3 iodines; regulates metabolisms, growth and development, and the activity of the nervous system

Calcitonin

lowers blood calcium and stimulates osteoblasts

What are some common pathologies associated with the thyroid gland?

- Goiter: iodine sufficiency (swelling of the thyroid gland)
- Cretinism: thyroid insufficiency in babies
- Hypothyroidism: decrease of thyroid hormones production
- Hyperthyroidism: excessive thyroid hormones

Which 2 hormones are important for the regulation of calcium level

Calcitonin & Parathyroid Hormone (PTH)

Parathyroid Hormone (PTH)

raises blood calcium and stimulates osteoclasts-bone resorption

Which endocrine hormones does the pancreatic gland make, and what are their roles?

Makes the endocrine hormones glucagon and insulin
- Glucagon: increases blood glucose levels
- Insulin: lowers blood glucose levels

Which hormone release is controlled directly by the sympathetic nervous system?

Epinephrine & Norepinephrine

Melatonin

Produced in the pineal gland, causes sleep and regulates circadian cycle

Which endocrine hormones are produced by gonads - testes and ovaries?

- Female=Ovaries
o Estrogen: development of oocytes, maintenance of female genital structures, and promote of secondary sex characteristics. Affects fluid and electrolyte balance and protein anabolism. Regulation of menstrual cycle.
- Male=Testes
o Testosterone: development of sperm; controls the growth and development of male genital organs, secondary sex characteristics, and body growth

What are all the major steroid hormones?

- Testosterone
- Estrogen
- Cortisol
- Aldosterone
- Androgen
- Progesterone
- Calcitriol

Testosterone

Develops sperm, controls growth & development of male genital organs, secondary sex characteristics, and body growth

Estrogen

Develops oocytes, maintains female genital structures, and promotes secondary sex characteristics. Regulation of menstrual cycle

Cortisol

Increases glucose levels in the blood, breaks down proteins, mobilizes fat, and suppresses inflammation

Aldosterone

retains Na+ ions in the body, excretes excess K+ ions into urine and retains water which increases blood pressure

Progesterone

helps prepare endometrium of the uterus for implantation of a fertilized ovum and the mammary glands for milk secretion

Calcitriol

regulates calcium and bone mineralization, activates vitamin D

Anabolic effect

energy-requiring reactions where small molecules are built into larger ones

Which hormones have anabolic effect?

- GH
- Testosterone
- Estrogen
- Insulin

Insufficient insulin results in

Diabetes Mellitus

Insufficient growth hormone results in

Pituitary Dwarfism

Too much growth hormone results in

Gigantism (adolescence) or Acromegaly (adult)

Insufficient ADH results in

Diabetes Insipidus

Diabetes Mellitus

- "sugar diabetes" insulin deficiency or insulin resistance (cells not responding to normal amount of insulin.
o 2 Types of Diabetes Mellitus:
- Type 1 & Type 2: have different causes and different progression but have the same final result

Diabetes Insipidus

lack of antidiuretic hormone (ADH)
o Common symptom is increased thirst

Goiter

Enlarged thyroid gland; a large lump on the neck due to iodine insufficiency

Myxedema

Hypothyroidism (decrease of thyroid hormone production) in adults, causing symptoms of slow heart rate, low body temperature, and weight gain, sensitivity to cold, muscle weakness, dry hair and skin, etc..

Gigantism

Excess growth hormone in childhood/adolescence, causing extreme height but proportionately build

Acromegaly

Excessive growth hormone production in adults, causing bone and tissue overgrowth. - A person will have crude facial features, large jaws, heavy forehead, large nose, lips and ears.