Endocrine System

Characteristics of Endocrine System

• Produce/Secrete hormones

• Target cells in body with a receptor

• Slow reaction time

• Have no ducts

• Have systemic effects by releasing hormones into bloodstream

Endocrine Functions

• Maintain homeostasis in blood composition (Ca, K, Na, Cl) in blood, blood volume and hematocrit

• Regulates division & differentiation of cells during development

Types of Signals for Hormonal Secretion

• Hormonal stimulation: trigger by another hormone

• Humoral stimulation: nutrients and ions in the blood

• Nervous stimulation: in response to nerve signals

Circulating Hormones

• Steroid hormones: lipid-soluble

• Protein hormones: water-soluble

• Biogenic amines: water-soluble

Eicosanoids

• Signaling molecules that regulates body processes, inflammation, and blood clotting

• Form by fatty acids that are part of phospholipids in the cell’s plasma membrane

Lipid-Soluble Hormones

• Not readily dissolve in blood plasma and require carrier proteins

• It’s readily diffuse through cell membrane. Once inside the cell, hormone receptor complex form when hormone binds to specific receptor

Mechanic of Hormones Interaction

• Interact only with target cells that have receptors for that hormone

• The more target cells there are, the greater influence the hormone can have

Water-Soluble Hormone

• Readily dissolve in the blood plasma

• Cannot cross the cell membrane, it must bind to plasma receptor which triggers series of events called signal transduction pathway

Nutrients

• Organic molecules derived from foods that generate APT

• Glucose, fatty acids, and amino acids

Endocrine Glands

• Lack ducts, rather the hormones are released into the blood and dispersed throughout the body

• Extensive blood supply

Parathyroid Glands

Produce parathyroid hormone in response to low blood calcium levels

Pineal Gland

Cells that secrete melatonin, helps regulate circadian rhythm (drowsiness)

Hypothalamus

Directly control pituitary gland and many other endocrine gland

Posterior Pituitary Gland

Does not produce hormones, but stores two hormones synthesized by hypothalamus

• Oxytocin

• Antidiuretic hormone (ADH)

Antidiuretic Hormone-ADH (Function)

• Constrict arterioles to raise blood pressure

• Hypersecretion of ___ causes water retention and concentration of urine

• Hyposecretion of ___ causes body to lose its ability to retain water

• Stimulates cortisol release

• Causes reabsorption of water from kidney tubules

• Released from the Posterior pituitary

Anterior Pituitary Gland

• Regulatory hormones produced in the hypothalamus trigger the release of hormones in the ___

• 5 of the 6 hormones are tropic hormones (stimulate secretion of other other hormones)

  1. Growth hormone

  2. Thyroid-stimulating hormone

  3. Follicle-stimulating hormone & luteinizing hormone

  4. Adrenocorticotropic hormone

  5. Melanocyte-stimulating hormone

  6. Prolactin

Growth Hormone & Insulin-Like Growth Factor (GH & IGF)

• All cells in the body have receptors for GH & IGF

• Increase blood glucose levels

• Increase levels of glycerol & fatty acids in the blood

• As blood glucose & fatty acid levels rise, amount of ATP increase which leads to growth

Thyroid Gland

Release thyroid hormone

• Increases metabolic rate & body temperature

• Increase lipolysis

• Increase breathing rate

• Increase heart rate & blood pressure

Follicle-Stimulating Hormone

• In females, stimulates development of oocytes and production of estrogen

• In males, stimulates production of sperm

Luteninzing Hormone

• In females, stimulates ovaries to produce estrogen and progesterone (pregnancy), ovulation, and testosterone

• In males, stimulates testes to produce testosterone

Adrenal Gland

Adrenal cortex synthesize more than two different corticosteroids, primarily cortisol

Cortisol

Increase nutrient levels (glucose, fatty acids, amino acids) in the blood to resist stress or repair damaged tissues

Prolactin

Acts on the estrogen-primed mammary glands of breast to cause milk production

Pancreas

Function is to maintain concentration of glucose in the blood

Insulin

• Released from pancreas in response to an increase in blood glucose levels

• Decrease all nutrients in the blood & increase storage in body tissues

Glucagon

• Released from pancreas in response to low blood glucose levels

• Results in an increase in levels of glucose

Type 1 Diabestes

• Insulin-dependent

• Absent or diminished production of insulin

Type 2 Diabetes

• Non-insulin dependent

• Decreased insulin release from pancreas or decreased effect on tissues

Biogenic Amines

• 3 catecholamines

  • Dopamine

  • Norepinephrine: alertness, focus

  • Epinephrine (Adrenaline): stress response, body energy

• Serotonin: mood, sleep, appetite

• Histamine: immune response

Serotonin vs Melatonin

• Serotonin governs mood, appetite, wakefulness

• Melatonin dictates circadian rhythms and causes drowsiness

Estrogen

• Class of steroid hormones

• Regulate reproductive system

• Slowdown bone resorption (breakdown)