Endocrine System Flashcards by Courtney T

Humoral stimuli

Changing blood levels of critical ions or nutrients that cause endocrine glands to secrete hormones

e.g. cells of the parathyroid glands monitor the body’s crucial calcium blood levels and release parathyroid hormone as needed

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Neural stimuli

Nerves stimulate hormone release

e.g. response to stress in which the sympathetic nervous system stimulates the adrenal medulla to release norepinephrine and epinephrine

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Hormonal stimuli

Endocrine glands release their hormones in response to hormones produced by other endocrine organs

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True/False: The nervous system can override normal endocrine controls

True

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When a hormone binds to a target cell receptor, what 3 factors does the degree of target cell activation depend on?

Blood levels of the hormone
Relative numbers of receptors for that hormone on or in the target cells
Affinity (strength) of the binding between the hormone and the receptor

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Up-regulation

Persistently low levels of a hormone can cause its target cells to form additional receptors for that hormone

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Down-regulation

Prolonged exposure to high hormone concentrations can decrease the number of receptors for that hormone

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Half-life

The length of time for a hormone’s blood level to decrease by half. Varies from a fraction of a minute to a week

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Water soluble hormones

Dissolve in water
Can travel freely in bloodstream
Cannot pass through cell’s lipid membrane
Consist of all amino-acid based hormones except for thyroid

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Lipid soluble hormones

Dissolve in fats
Easily pass through the cell membrane of target cells and bind to receptors inside the cell

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Thyroxine (T4)

Principal hormone stimulatling cellular metabolism, produced by the thyroid gland.

Nearly all cells have thyroxine receptors

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Permissiveness (hormone interaction)

Situation in which one hormone cannot exert its full effects without another hormone being present.

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Synergism (hormone interaction)

Occurs when more than one hormone produces the same effects at the target cell and their combined effects are amplified

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Antagonism (hormone interaction)

Occurs when one hormone opposes the action of another

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Oxytocin

Released by: Posterior pituitary gland

Target organ(s): Uterus, Breast

Effects: Stimulates contractions, initiates labor, initiates milk ejection

Stimulated by: Stretching cervix, infant suckling at breast

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Antidiuretic hormone (ADH)

Released by: Posterior pituitary gland

Target organ(s): Kidneys

Effects: Stimulate kidney tubule cells to reabsorb water from forming urine back into blood

Stimulated by: Increased blood solute concentration, low BP, pain, some drugs

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Growth Hormone (GH)

Released by: Anterior pituitary gland

Target organ(s): Liver, muscle, bone, cartilage, other tissue

Effects: Direct actions on metabolism (increase blood glucose and fat breakdown/release), indirect actions on growth

Stimulated by: Growth Hormone Release Hormone (GHRH) release

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Thyroid Stimuating Hormone (TSH)

Released by: Anterior pituitary gland

Target organ(s): Thyroid gland

Effects: Stimulates release of thyroid hormones

Stimulated by: Thyrotropin Releasing Hormone (TRH)

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Adrenocorticotropic Hormone (ACTH)

Released by: Anterior pituitary gland

Target organ(s): Adrenal cortex

Effects: Promotes release of glucocorticoids and gonadocorticoids

Stimulated by: Corticotropin Releasing Hormone (CRH)

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Follicle Stimulating Hormone (FSH)

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Released by: Anterior pituitary gland

Target organ(s): Ovaries, Testes

Effects: Stimulates ovarian follicle maturation and production of estrogens, stimulates sperm production

Stimulated by: Gonadotropin-Releasing Hormone (GnRH)

Luteinizing Hormone (LH)

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Released by: Anterior pituitary gland

Target organ(s): Ovaries, Testes

Effects: Triggers ovulation and stimulates production of estrogen and progesterone, promotes testosterone production

Stimulated by: Gonadotropin-Releasing Hormone (GnRH)

Prolactin

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Released by: Anterior pituitary gland

Target organ(s): Breast secretory tissue

Effects: Promotes lactation

Stimulated by: Decreased Prolactin Inhibiting Hormone (PIH), estrogens, infant suckling at breast

Diabetes insipidus

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Caused by inadequate release of antidiuretic hormone (ADH), characterized by intense thirst, dehydration, and huge urine output

Tropic hormones

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Hormones that stiumlate hormone secretion by other endocrine glands

Gigantism

Caused by hypersecretion of growth hormone in children. Person becomes extremely tall but has relatively normal proportions

Acromegaly

Caused by hypersecretion of growth hormone in adults. Characterized by overgrowth of bones of the hands, feet, and face

Pituitary dwarfism

Caused by hyposecretion of growth hormone in children. Results in an individual having normal proportions but short stature due to decreased growth of long bones

Thyrotropin Releasing Hormone (TRH)

Hypothalamic hormone that triggers the release of TSH from anterior lobe of the pituitary gland

Corticotropin-releasing hormone (CRH)

Hypothalamic hormone that stimulates the corticotropic cells of the anterior lobe of the pituitary gland to produce and release adrenocorticotropic hormone (ACTH)

Gonadotropin-releasing hormone (GRH)

Hypothalamic hormone that stimulates the gonadotropic cells of the anterior lobe of the pituitary gland to produce and release the gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

Prolactin-inhibiting hormone (PIH)

Hypothalamic hormone that inhibits the prolactin cells of the anterior lobe of the pituitary gland from secreting prolactin; also known as dopamine.

Thyroid Hormone (TH)

The body's major metabolic hormone

Thyroxine (T4)

Less active form of thyroid hormone, gets converted into T3 in cells to perform metabolic functions

Triodothyronine (T3)

More active form of thyroid hormone, formed at target tissue by conversion of T4

Grave's disease

An autoimmune condition that causes hyperthyroidism. Symptoms: elevated metabolic rate; sweating; rapid, irregular heartbeat; nervousness; bulging eyes; and weight loss despite adequate food

Calcitonin

Released by: Parafollicular cells of the thyroid Effects: Decreases blood calcium level by inhibiting osteoclast activity, which inhibits bone resorption and release of calcium from the bony matrix Stimulated by: A rise in blood calcium levels

Parathyroid glands

Small endocrine glands located on the posterior aspect of the thyroid gland.

Parathyroid Hormone (PTH)

The single most important hormone controlling calcium balance in the blood Stimulated by: Falling blood calcium levels Target organs: Skeleton, kidneys, intestines

Corticosteroids

Steroid hormones released by the adrenal cortex.

Zona glomerulosa

Most superficial layer of adrenal cortex. Produces mineralocorticoids, hormones (such as aldosterone) that help control the balance of Na+, K+, and water in the blood

Zona Fasciculata

Middle layer of adrenal cortex. Produces the metabolic hormones called glucocorticoids (such as cortisol).

Zona reticularis

Innermost layer of adrenal cortex. Produces small amounts of adrenal sex hormones, or gonadocorticoid

Mineralocorticoids

Regulate the electrolyte (mineral salt) concentrations in extracellular fluids

Aldosterone

Hormone produced by the adrenal cortex that regulates Na+ reabsorption and K+ secretion by the kidneys

Glucocorticoids

Influence the energy metabolism of most body cells and help us resist stressors. Cortisol is most abundant in humans

What is cortisol's prime metabolic function?

To provoke glucogenesis—the formation of glucose from fats and proteins, in order to "save" glucose for the brain

Alpha cells

Cells of pancreatic islets that produce the hormone glucagon

Beta cells

Cells of pancreatic islets that produce the hormone insulin.

Endocrine System Flashcards

(49 cards)