BIO 202: Chapter 1.1 and 1.2 Endocrine System Anatomy and Physiology and Endocrine Organs and Hormones

endocrine system

uses hormones released into the bloodstream, produces slower but longer lasting effects, can affect many tissues and organs at once

exocrine glands

release their products through ducts to the surface of an organ or the body

• includes sweat, salivary, lacrimal, digestive, and mammary glands

endocrine glands

secrete hormones directly into the bloodstream to travel to target tissues throughout the body

nervous system

uses electrical impulses and neurotransmitters, produces immediate but short-term effects, acts on specific and localized targets

functions of hormones

stimulate production of enzymes or other hormones, changing a cell’s metabolic activity, and modifying permeability of the plasma membrane or receptor sensitivity

tropic hormones

target other endocrine glands to cause them to release additional hormones

• thyroid-stimulating hormone (TSH) stimulates thyroid gland to produce thyroid hormones

non-tropic hormones

act directly on non-endocrine tissues to trigger physiological changes

• insulin acting directly on liver and muscle cells to lower blood glucose

steroid hormones

derived from cholesterol, lipid-soluble so they can pass through cell membrane, bind to intracellular receptors, typically alter gene expression

• includes cortisol, aldosterone, estrogen, and testosterone

amine hormones

derived from amino acids, water soluble or lipid soluble depending on specific hormone

• includes epinephrine, norepinephrine, melatonin, thyroid hormones

water soluble hormones

dissolve easily in blood and do not need transport proteins but they cannot cross the lipid membrane so they bind receptors on outside of target cell membrane so activate a second messenger system

• includes insulin, epinephrine, and most peptide and protein hormones

lipid soluble hormones

require transport proteins to move through the blood because they do not dissolve in water but can pass directly through lipid bilayer and bind to receptors inside cell to work by changing gene expression

• includes cortisol, estrogen, thyroid hormones

secondary endocrine functions

organs perform other primary roles in the body but also secrete hormones

heart

secretes atrial natriuretic peptide (ANP) to help lower blood pressure by causing kidney to remove excess salt and water

adipose tissue

secrete leptin to signal brain to reduce hunger when enough fat is stored in the body

kidney

secrete erythropoietin (EPO) to stimulate production of red blood cells when oxygen levels are low

liver

secrete thrombopoietin to stimulate platelet production in bone marrow and angiotensinogen to help regulate blood pressure and fluid balance

hypothalamus

connects to the pituitary gland via the infundibulum

pituitary gland

sits in a depression called the hypophyseal fossa within the sella turcica of the sphenoid bone

anterior pituitary gland

composed of glandular epithelium and accounts for anterior ¾ of the pituitary gland

• produces and secretes several hormones

posterior pituitary gland

composed of nervous tissue and accounts for posterior ¼ of the pituitary gland

• does not produce hormones but stores and releases hormones made by hypothalamus

pineal gland

midline structure in posterior diencephalon and is tiny and pine cone-shaped

thyroid gland

butterfly-shaped and wraps around the trachea with two lobes connected by an isthmus

• largest endocrine gland

parathyroid gland

four small oval nodules on posterior surface of the thyroid

thymus gland

located in anterior mediastinum behind the sternum, large in children but small and fatty in adults

adrenal glands

sit atop each kidney, right is triangular and left is crescent-shaped

pancreas

elongated gland across the posterior abdomen

• has both endocrine and exocrine functions

ovaries

almond-shaped, lateral to uterus near uterine tube ends

• produce oocytes, the female gametes, and secrete sex hormones

testes

oval organs in the scrotum that contain coiled seminiferous tubules and interstitial cells

thyrotropin-releasing hormone (TRH)

released by hypothalamus and interacts with anterior pituitary gland to stimulate secretion of thyroid-stimulating hormone and prolactin

corticotropin-releasing hormone (CRH)

released by hypothalamus and interacts with anterior pituitary gland to stimulate secretion of adrenocorticotropic hormone

gonadotropin-releasing hormone

released by hypothalamus and interacts with anterior pituitary gland to stimulate secretion of follicle-stimulating hormone and luteinizing hormone

growth hormone-releasing hormone

released by hypothalamus and interacts with anterior pituitary gland to stimulate secretion of growth hormone

prolactin-inhibiting hormone

released by hypothalamus and interacts with anterior pituitary gland to inhibit secretion of prolactin

somatostatin

released by hypothalamus and interacts with anterior pituitary gland to inhibit secretion of growth hormone and thyroid-stimulating hormone

hypothalamic-hypophyseal portal system

specialized blood vessel in which the hypothalamus communicates with the anterior pituitary

1. releasing and inhibiting hormones synthesized by neurons in hypothalamus

2. hormones enter primary capillaries located in hypothalamus

3. hormones travel through small veins called portal venules in the infundibulum

4. hormones enter secondary capillaries in the anterior pituitary and exit blood to influence hormones-secreting cells

oxytocin

released by hypothalamus and interacts with posterior pituitary gland to trigger uterine contractions during childbirth and stimulates milk ejection

antidiuretic hormone

released by hypothalamus and interacts with posterior pituitary gland to promote water retention by the kidneys and helps regulate blood pressure

hypothalamo-hypophyseal tract

consists of neurons extending from the hypothalamus down through the infundibulum into the posterior pituitary and is the means by which hypothalamus hormones are transported

follicle-stimulating hormone

produced by anterior pituitary gland to stimulate the development of follicles in the ovaries and sustentacular cells for sperm production in the testes

luteinizing hormone

produced by anterior pituitary gland to trigger ovulation development in the ovaries and stimulate interstitial cells in the testes to produce testosterone

adrenocorticotropic hormone

produced by anterior pituitary gland to stimulate hormone secretion from the adrenal cortex during stress response

thyroid stimulating hormone

produced by anterior pituitary gland to stimulate thyroid gland to grow and secrete hormones that regulate metabolism and temperature

prolactin

produced by anterior pituitary gland to promote milk production

growth hormone

produced by anterior pituitary gland (also called somatotropin) to stimulate cells division and protein synthesis

true

true or false: the posterior pituitary gland does not synthesize any hormones but instead stores and releases oxytocin and antidiuretic hormone that are produced by the hypothalamus

melatonin

secreted by the pineal gland in response to decreased light levels to help trigger the onset of sleep

thyroid follicles

hollow spheres that compose the thyroid gland and are lined by simple cuboidal epithelial cells called follicle cells

colloid

gelatinous, iodine-rich substance inside each follicle that stores the raw materials needed for thyroid hormone synthesis

tetraiodothyronin (T4)

produced by thyroid gland, contains four iodine atoms, known as thyroxine

triiodothyronine (T3)

produced by thyroid gland, contains three iodine atoms, more active thyroid hormone

parafollicular cells

located between or at the periphery of follicle cells and secrete the hormone calcitonin

calcitonin

released when blood calcium levels are high and stimulate osteoblast activity to increases bone deposition and formation to decrease blood calcium levels

parathyroid hormone

secreted by parathyroid glands to maintain calcium ion homeostasis when blood calcium levels are low through …

• stimulating osteoclast activity to break down bone tissue

• increasing calcium ion absorption from the intestines

• increasing calcium ion reabsorption from the kidneys

antagonistic

parathyroid hormone and calcitonin are _____ hormones because they have opposite effects on blood calcium levels

endocrine, lymphatic, and immune systems

the thymus gland is unique as it functions in three systems which are the …

thymosin, thymulin, thymopoietin

hormones secreted by the thymus gland to stimulate development of other lymphatic organs and regulate development and activity of T lymphocytes

adrenal cortex

outer, yellowish region that surrounds the adrenal medulla on all sides, makes up about 80 to 90 percent of the adrenal gland, secretes steroid hormones derived from cholesterol, and is organized into 3 distinct layers

zona glomerulosa

thin outermost layer of the adrenal cortex of the adrenal gland

mineralocorticoids

hormone type secreted by zona glomerulosa to regulate electrolyte balance, fluid volume, blood pressure, and pH

• ex: aldosterone to stimulate kidneys to retain sodium and water, promote excretion of potassium, and regulate acid-bade homeostasis

hyperaldosteronism

overproduction of aldosterone which leads to high blood pressure and low potassium

addison’s disease

underproduction of aldosterone which causes dehydration, low blood pressure, and electrolyte imbalance

underproduction of cortisol which results in fatigue, low glucose, and poor stress response

zona fasciculata

thick middle layer that makes up ¾ of the adrenal cortex of the adrenal gland

glucocorticoids

hormone type secreted by zona fasciculate to regulate glucose metabolism, stress response, and inflammation

• ex: hydrocortisone to reduce inflammation, increase blood glucose, promote protein and fat breakdown, inhibit glucose uptake, and suppresses immune response

cushing’s syndrome

overproduction of cortisol which causes muscle wasting, extreme fatigue, hyperglycemia, insulin resistance, redistribution of fat, and obesity

zona reticularis

narrow innermost layer of the adrenal cortex of the adrenal gland

glucocorticoids and gonadocorticoids

hormone type secreted by zona reticularis to support reproductive development and secondary sex characteristics

• ex: androgens to promote pubic and axillary hair growth, skin oil production, and support muscle and bone mass

• ex: estradiol to maintain bone density

adrenal medulla

inner core of the adrenal gland, makes up 10 to 20 percent of its volume, secretes adrenal catecholamines directly into the bloodstream in response to stress

adrenal catecholamines

hormones secreted by adrenal medulla of the adrenal gland to trigger and sustain the fight of flight response

• ex: epinephrine and norepinephrine which increase heart rate and contractile strength, elevate blood pressure, dilate bronchioles and pupils, increase blood glucose, and suppress digestion and urination

pheochromocytoma

overproduction of epinephrine and norepinephrine which causes tumor of the adrenal medulla, anxiety, palpitations, and high blood pressure

exocrine function of the pancreas

pancreatic acini (cells) produce pancreatic juices that are secreted into pancreatic ducts and then released into the small intestine to neutralize hydrochloric acid and help digest proteins, lipids, and carbohydrates with enzymes

endocrine function of the pancreas

pancreatic islets (cells) responsible for the hormonal regulation of blood glucose which contain two types of hormone-secreting cells

beta cells

make up 70% of pancreatic islet cells and secrete insulin

insulin

triggers the uptake of glucose from the bloodstream into body cells, stimulates cells to store glucose as glycogen, promotes fat storage and protein synthesis

• overall effect of lowering blood glucose concentration

alpha cells

make up 20% of pancreatic islet cells, located towards the edges of a pancreatic islet, and secrete glucagon

glucagon

stimulates the liver to break down stored glycogen into glucose to promote gluconeogenesis which id the production of new glucose from non-carbohydrate sources

• overall efect of raising blood glucose concentration

diabetes mellitus

results from an imbalance or failure in insulin production or function

• type 1: immune system destroys beta cells → little to no insulin

• type 2: body resists effects of insulin or doesn’t produce enough

hypoglycemia

too much insulin is present or not enough glucose is available

testosterone

secreted by the interstitial cells of within the testes and is the principal male sex hormone

• stimulates spermatogenesis or the production of sperm

• promotes development of male secondary sex characteristics

estrogen

secreted by the ovaries to support the development and maturation of oocytes, promote female secondary sex characteristics, and regulate several reproductive processes like the menstrual cycle

progesterone

secreted by the ovaries to prepare the uterus for implantation of a fertilized egg, support pregnancy by maintaining the uterine lining, and regulate the menstrual cycle with estrogen