Endocrine system

Hormones: Explain how they work, know the glands that produce which hormone, how hormones maintain homeostasis.

Endocrine disruptors: chemicals manufactured by humans that, when taken up by organisms, can mimic, block, or otherwise interfere with their hormones, leading to harmful effects.

Animals communicate through their nervous and endocrine systems.

The endocrine system sends messages via chemical signals secreted by endocrine cells into ECF, including often the bloodstream, and influencing target cells at a distance. Generally responsible for slower, longer-term regulation, such as growth and development as well as a variety of secretions.

Hormone à target cell à response (cell function changes)

Pheromones are transported to the outside of the body to cause a behavioral or physiological change in another individual of the same species. (Alarm pheromones, territorial pheromones, trail-marking pheromones, and sex pheromones)

Protein and steroid hormones

Protein: receptors are on the outside of the cells, protein hormones are faster than steroid hormones.

Steroid: can pass through the membrane, binds to the receptor in the cytoplasm or nucleus of the cell.

Dysfunctional receptors

Androgen insensitivity syndrome: genetically male but has external female sex characteristics, do not respond to the male hormone androgen because of dysfunctional receptors.

Endocrine glands: hypothalamus, pineal gland, pituitary gland, thyroid gland, parathyroid gland, thymus, adrenal glands, pancreas, ovary, testis.

Hypothalamus: receives input from neurons throughout the brain and the rest of the body; releases hormones that regulate nearly every aspect of an organism’s physiology.

Anterior pituitary: produces numerous hormones, many of which direct endocrine glands elsewhere to release hormones including thyroid stimulating hormone, follicle stimulating hormone, luteinizing hormone, prolactin, adrenocorticotropic hormone, growth hormone.

Posterior Pituitary: releases two important hormones produced within the hypothalamus: oxytocin (cuddle hormone) and antidiuretic hormone (maintains normal water concentration in the body, regulates the amount of urine produced).

Improper functioning of the pituitary can lead to anomalies in growth and development

Gigantism: excess growth hormone in childhood, excess growth.

Dwarfism: deficiency of growth hormone, less growth.

Acromegaly: excess growth hormone during adulthood, affects bones, joints, and makes hands larger.

Pineal gland: controls the secretions of the hormone melatonin and affects sleep patterns (circadian cycle). Also known as the darkness hormone.

Hormone regulation: hypothalamic hormone (releasing/inhibiting) à pituitary hormone (increase/decrease) à other glands release other hormones (uses negative feedback mechanism).

The thyroid gland releases the hormone thyroxine, it is made by the thyroid, requires iodine, controls the rate of metabolism, and is regulated by both the hypothalamus and the anterior pituitary gland.

Improper functioning of the thyroid gland can lead to metabolic anomalies.

Goiter (hypothyroidism): low levels of thyroxine, enlarged thyroid gland.

Graves disease (hyperthyroidism): excessive or high levels of thyroxine, fast metabolism, weight loss, irritability, high temperature, sweating, high BP, bulging eyes.

Again, this is a negative feedback mechanism.

Hormones help maintain homeostasis

-        Thyroid and parathyroid glands control calcium levels

Blood glucose regulation:

-        Pancreas releases insulin, which lowers blood glucose levels

-        Pancreas releases glucagon, which raises blood glucose levels

Two types of diabetes

1.     Insulin-dependent (autoimmune)

2.     Non-insulin-dependent (lack of response to insulin)

Calcium regulation:

-        Calcium: bones and teeth, nerve and muscle function

-        Thyroid gland releases calcitonin, causes bones to take up excess calcium from the blood

-        Parathyroid gland releases parathyroid hormone, which plays a central role in regulating calcium levels in adults.

Adrenal glands: cortisol (long term stress) and adrenaline (fight or flight)

Addisons disease: low cortisol level, autoimmune disorder, depression, dizziness, low blood glucose, low BP.

Chronic stress: excess cortisol, high blood glucose, obesity.

Pathway: hypothalamus (CRH) à pituitary (ACTH) à adrenal (cortisol). Negative feedback mechanism.

Gonads: ovaries and testes

Hypothalamus releases “releasing hormones” which increases the secretion of hormones by anterior pituitary gland and these hormones (FSH and LH) influence the sex organs (gonads: ovary in females and testes in males). LH promotes secretion of estrogen or testosterone. FSH influences sperm production and oogenesis

Hypothalamus (releasing hormones) à anterior pituitary (FSH or LH) à spermatogenesis oogenesis or sex hormones.