Exam 1 flashcards by MATI (endocrine system)

long-distance chemical signals of the endocrine system; travel in blood to reach target cells

locally acting chemicals that affect neighboring cells (talking to a neighbor)

chemicals that exert effects on same cells that secrete them (auto = its own self)

1. amino based

2. steroids

1. Amino acid derivatives, peptides, and proteins

2. Water soluble (except thyroxine), cannot cross plasma membrane

1. Synthesized from cholesterol

2. Lipid soluble, can cross plasma membrane

3. Includes gonadal and adrenocortical hormones

eicosanoids, are considered hormones by some scientists, but most classify them as paracrine and autocrine given their highly localized effects

Target cells

1. Alter plasma membrane permeability and/or membrane potential by opening or closing ion channels

2. Stimulate synthesis of enzymes or other protein

3. Activate or deactivate enzyme

4. Induce secretory activity

5. Stimulate mitosis (cell division)

1. Act on plasma membrane receptors

2. Cannot cross plasma membrane to enter cell (water-soluble)

3. Most are coupled via G proteins to second messengers

1. Act on intracellular receptors that directly activate genes

2. Can diffuse across plasma membrane to enter cell (lipid-soluble)

1. Cyclic AMP

2. PIP2- Calcium

1. Hormone binds receptor

2. Receptor activates G protein

3. G protein activates/inhibits adenylate cyclase

4. ATP → cAMP

5. cAMP activates kinases that phosphorylate proteins

6. Cascade amplifies signal

7. Proteins activated/inactivated

8. Phosphodiesterase degrades cAMP, ending cascade

1. G protein activates phospholipase C

2. PLC splits PIP2 into DAG + IP3

3. DAG activates protein kinases

4. IP3 triggers Ca²⁺ release from storage

5. Ca²⁺ alters enzymes/channels or binds calmodulin

6. Ca²⁺-calmodulin activates enzymes, amplifying response

1. cGMP (cyclic guanosine monophosphate) is a second messenger for some hormones

2. Other hormones work w/o second messenger system

   1. insulin receptor is a tyrosine kinase enzyme that auto phosphorylates upon insulin binding

      1. It provides docking sites for relay proteins that trigger cell responses

an extracellular signaling molecule that binds to a cell surface receptor to initiate a cellular response

a small molecule inside a cell that relays and amplifies a signal from a hormone outside the cell with a message stuck on the outside of the cell's surface.

a molecular switch inside a cell that transmits chemical signals from the outside of the cell to the inside, it sits next to a receptor in cell membrane (binds to GTP)

a cell enzyme that turns cellular energy (ATP) into a chemical messenger called cyclic AMP (cAMP) (second messenger)

a type of enzyme that breaks down (degrades) specific chemical bonds inside cells

an enzyme that breaks down (degrades) phospholipids

a minor phospholipid component of cell membranes (molecular switch located on the inner surface of the cell membrane that helps transmit signals from outside the cell to the inside)

a type of fat molecule made of a glycerol (helps pass chemical signals inside the body's cells)

a water-soluble second messenger molecule that helps cells respond to outside signals like hormones

1. a small, specialized protein found in all eukaryotic cells (cells with a nucleus).

2. It acts as a calcium sensor and messenger. Because it cannot function without calcium (binds to it)

3. Calmodulin acts like an on/off switch for other proteins in the body

1. humoral

2. neural

3. hormonal

Changing blood levels of ions and nutrients directly stimulate release of hormones

1. a drop in blood calcium levels stimulates the parathyroid gland to secrete Parathyroid Hormone (PTH)

2. PTH causes calcium causes calcium to rise and stimulus ends

Nerve fibers cause hormone release

1. stressors activate neurons in hypothalamus

2. signals down spinal cord

3. to preganglionic fibers

4. stimulate adrenal medulla to secrete catecholamines such as norepinephrine and epinephrine (happens when there's trauma to the body) (fight or flight from sympathetic system)

Hormones stimulate other endocrine organs to release their hormones

1. Hypothalamic hormones stimulate the anterior pituitary gland to releases hormones

2. anterior pituitary hormones cause release of hormones of other endocrine organs such as adrenal cortex, thyroid gland and gonads

3. these target organs inhibit hormonal release from anterior pituitary and hypothalamus

1. Blood levels of hormone

2. Relative number of target cell receptors

3. Affinity (strength) of binding between hormone and receptor

1. target cells add receptors in response to persistently low levels

   1. Allows target cell to become more sensitive to less hormone

1. cells remove receptors in response to persistently high levels

   1. Desensitizes the target cells to prevent them from being over stimulated

1. time required for level of hormone in blood to decrease by half

Note: Varies from a fraction of a minute to a week, depending on hormone

one hormone cannot exert its effects without another hormone being present

more than one hormone produces same effects at target cell and combined effects are amplified

glucagon and epinephrine both cause liver to release glucose

one or more hormones oppose(s) action of another hormone

glucagon raises blood glucose while insulin lowers it

Infundibulum

1. posterior pituitary (neurohypophysis)

2. anterior pituitary (adenohypophysis)

neurohormones

1. oxytocin

2. ADH

Antidiuretic Hormone

6 (GH, TSH, ACTH, FSH, LH, PRL)

Growth Hormone

Thyroid Stimulating Hormone

Adrenal Corticotropic Hormone

Follicle Stimulating Hormone

Luteinizing Hormone

Prolactin

hypothalamic-hypophyseal tract

paraventricular and supraoptic nuclei of hypothalamus and runs through the infundibulum

1. Primary capillary plexus

2. Hypophyseal portal veins

3. Secondary capillary plexus

1. the releasing and inhibiting hormones from hypothalamus travel through hypophyseal portal system to anterior pituitary to regulate secretion of its 6 hormones

2. in other words, the hypophyseal portal system controls the release of anterior pituitary hormones

1. Paraventricular nuclei mostly produce oxytocin

2. Supraoptic nuclei mostly produce antidiuretic hormone (ADH)

small peptides (nine amino acids each)

Growth Hormone (GH)

1. Prolactin (PRL)

2. Growth Hormone (GH)

a butterfly shaped gland (largest pure endocrine gland) located on the anterior trachea, just inferior to larynx

(colloid-filled) spheres of epithelial follicular cells that produce glycoprotein thyroglobulin

a thick fluid containing thyroglobulin proteins with attached iodine, from which thyroid hormone is produced

1. a hormone produced by the parafollicular (C cells) in your thyroid gland that helps lower calcium and phosphate levels in your blood

2. Inhibits osteoclast activity and prevents release of calcium from bone matrix

3. Stimulates calcium uptake and incorporation into bone matrix

Thyroid Hormone (TH)

1. T4 (tetraiodothyronine or thyroxine)

   1. consists of two tyrosine molecules with four bound iodine atoms

2. T 3 (triiodothyronine)

   1. consists of two tyrosine molecules with three bound iodine atoms

the Increase of basal metabolic rate and heat production by TH

1. Stimulate osteoclasts to digest bone matrix and release calcium to blood

2. Enhances reabsorption of calcium and secretion of phosphate by kidneys

3. Promotes activation of vitamin D by kidneys, which leads to increased absorption of calcium by intestinal mucosa

Contain oxyphil cells (function unclear) and parathyroid cells that secrete the protein parathyroid hormone (PTH), or parathormone

1. (excess PTH) usually due to parathyroid gland tumor

   1. Calcium leaches from bones (into blood), they soften and deform

      1. Osteitis fibrosa cystica: form of disorder, bones spontaneously fractured

   2. Elevated blood calcium (hypercalcemia) depresses nervous system and contributes to formation of kidney stones

1. (insufficient PTH) may follow parathyroid gland trauma or removal

   1. Resulting hypocalcemia can increase excitability of neurons, causing: Tingling sensations, tetany (twitching muscle), and even convulsions

1. adrenal cortex

2. adrenal medulla

three outer layers of glandular tissue that synthesize and secrete several different steroid hormones

1. Zona glomerulosa produces mineralocorticoids

2. Zona fasciculata produces glucocorticoids

3. Zona reticularis produces gonadocorticoids

1. Regulate blood electrolyte (mineral salt) concentrations (primarily sodium and potassium)

   1. Water follows sodium, so sodium levels affect blood volume and pressure

   2. potassium sets the resting membrane potential of cells which finds how easily action potentials are generated in neurons and muscle cells

1. Aldosterone stimulates synthesis and activation of Na K+ +−ATPase transport pumps (which exchange Na for K )+ +in the kidney tubules, resulting in:

   1. Increased+ reabsorption by kidneys, increases blood volume and pressure (as water follows Na )+–

   2. Increased K+ secretion (and thus excretion) by kidneys

1. Renin-angiotensin-aldosterone system

2. Plasma concentration of K+

3. ACTH

4. Atrial natriuretic peptide (ANP)

1. Cortisol (hydrocortisone)

   1. Only glucocorticoid secreted in significant amounts Inhumans

2. Cortisone

3. Corticosterone

1. Influence nutrient (energy) metabolism of most cells and help us resist stressors

   1. Help regulate blood glucose levels

   2. Help maintain blood pressure by increasing action of vasoconstrictors

1. Cortisol increases blood levels of amino acids and fatty acids by triggering protein breakdown and signaling adipose tissue to breakdown stored fat

   1. It encourages other cells to use fatty acids for fuel, so glucose is “saved” for brain

1. Cortisol’s main metabolic role is to increase blood glucose by signaling liver to increase glucose synthesis from amino and fatty acids (gluconeogenesis)

2. Cortisol enhances vasoconstriction by the sympathetic nervous system during times of stress or low blood pressure (hypotension)

1. excess of glucocorticoids

   1. ACTH-releasing tumor of the lungs, pancreas, or kidneys

      1. Called Cushing’s disease is caused by ACTH-releasing pituitary tumor▪ Cortisol-releasing tumor of the adrenal cortex

1. High blood glucose (steroid diabetes)

2. Dramatic loss of muscle and bone proteins▪

3. Salt and water retention leading to high blood pressure and edema

4. Easy bruising, poor wound healing, and higher risk of serious infections (from suppression of immune system)

5. buffalo hump on back (fat on upper back)

1. hyposecretion of corticosteroids

   1. Usually involves deficits in both glucocorticoids and mineralocorticoids

1. Weight loss

2. Decrease in blood glucose and Na+ levels

3. increase in blood K+ levels

4. Severe dehydration and low blood pressure are common

1. Weak androgens (male sex hormones) such as androstenedione and dehydroepiandrosterone (DHEA)

   1. Most converted to stronger male hormones like testosterone in target tissues

   2. some converted to estrogens

1. Contribute to appearance of secondary sex characteristics

2. Thought to contribute to sex drive in women

3. Main source of estrogens in postmenopausal women

1. masculinization of females

   1. masculinization via hypersecretion of gonadocorticoids

1. Medullary chromaffin cells

   1. Synthesize the catecholamines epinephrine (80%) and norepinephrine (20%) from tyrosine

   2. Stimulated to secrete catecholamines (by preganglionic sympathetic neurons) during the fight-or-flight (stress) response

1. Blood pressure increases via vasoconstriction and increased heart rate

2. Blood diverted from nonessential organs to heart and skeletal muscle

3. Blood glucose levels rise

1. anything that creates stress (whether physiological or psychological), triggering the stress response, or general adaptation syndrome

   1. Coordinated by the hypothalamus

triggers the fight-or-flight response mediated by the sympathetic nervous system and adrenal catecholamines

triggers the slower resistance reaction mediated by adrenal corticosteroids

occurs if long-term stress is too long, causing the stress hormones themselves to disrupt homeostasis

1. its Pinealocytes secrete melatonin

   1. Synthesized from serotonin (which is derived from tryptophan)

   2. Blood levels rise and fall in a diurnal (daily) cycle

      1. Peak levels at night make us sleepy; lowest levels around noon

1. A major role is prevention of oxidative damage within cells (as an antioxidant)

2. May have antigonadotropic effect in children to prevent early sexual maturation

3. Targets “biological clock” in hypothalamus (suprachiasmatic nucleus) in physiological processes like body temperature, sleep, and appetite

a tadpole-shaped organ located partially behind stomach

1. Acinar (exocrine) cells produce enzyme-rich fluid for digestion

2. Pancreatic islets (islets of Langerhans) consist of endocrine cells

1. glucagon

2. insulin

1. it is a hyperglycemic hormone

2. released by the less numerous alpha cells in response to:

   1. Falling blood glucose levels and rising amino acid levels

   2. Release of norepinephrine from sympathetic nerve fibers

Increases release of glucose from the liver by stimulating it to:

1. Breakdown glycogen into glucose (glycogenolysis)

2. Synthesize glucose from lactic acid and noncarbohydrates (gluconeogenesis)

1. it is a hypoglycemic hormone

2. released by the more abundant beta cells in response to:

   1. Elevated blood glucose levels (primary stimulus)

   2. Rising blood levels of amino acids and fatty acids

   3. Release of acetylcholine by parasympathetic nerve fibers

3. Sympathetic nervous system inhibits insulin release

1. betters' protein synthesis and fat storage

2. Main effect is to lower BG levels after we eat

   1. better membrane transport of glucose into fat and muscle cells to be used for glycolysis (to make ATP) or stored as glycogen

      1. Inhibiting breakdown- glycogen to glucose

      2. conversion of amino acids/fats to glucose

1. Hyposecretion of insulin- Type 1

2. Hypoactivity of insulin- Type 2

1. Huge urine output results in excess water loss

   1. Excess glucose in kidney filtrate acts as an osmotic diuretic (water follows glucose into the urine)

   2. Leads to excessive thirst

2. Excessive hunger and food consumption

   1. Cells cannot take up glucose and are “starving”

Huge urine output

excessive thirst

excessive hunger

ketones or ketone bodies

drop in blood pH

Excessive blood levels of ketones

abnormally high levels of ketones in urine

high levels of fatty acids in blood

1. Excessive insulin secretion

2. Causes hypoglycemia (low blood glucose levels)

3. Symptoms include:

   1. Anxiety, nervousness, tremors, and weakness

1. As fat stores increase, adipocytes secrete

   1. More leptin, which promotes a feeling of satiety (not hungry) and stimulates increased energy expenditure

      1. More resistin, which reduces sensitivity of cells to insulin (insulin antagonist)

      2. Less adiponectin, which enhances sensitivity of cells to insulin

1. Enteroendocrine cells found throughout mucosa of gastrointestinal tract

   1. Hormones from stomach include gastrin and ghrelin

   2. Hormones from intestine include secretin and cholecystokinin (C CK)

   3. These and other gastrointestinal peptide hormones help regulate digestive functions

1. Secretes two natriuretic peptides in response to high blood volume and pressure: atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP)

   1. ANP ten times more potent than BNP

   2. Both increase excretion of Na+ (therefore water) in urine, causing decrease in blood volume and pressure

1. Secrete erythropoietin in response to low blood oxygen levels

   1. Erythropoietin stimulates production of red blood cells

   2. Secrete enzyme renin in response to low blood pressure

      1. Activates the renin-angiotensin-aldosterone system

1. Osteoblasts in bone secrete osteocalcin

   1. Prods pancreas to secrete more insulin; restricts fat storage; improves glucose handling; reduces body fat

   2. Activated by insulin

   3. Low levels of osteocalcin are present in type 2 diabetes

1. produces cholecalciferol (inactive form of vitamin3D), the precursor to steroid hormone calcitriol

   1. Converted to active vitamin 3D (calcitriol) by liver and kidneys

   2. Calcitriol increases intestinal absorption of calcium

      1. modulates immune functions, reduces inflammation, may act as anticancer agent

1. Large in infants and children; shrinks with age

2. Secretes peptide hormones including thymosins, thymulin, and thymopoietins

   1. Appear to be involved in normal development of T lymphocytes in thymus

   2. May have mostly paracrine functions