The Endocrine System Flashcards
Endocrine Glands
Pituitary gland, Hypothalamus, Thymus, Pineal gland, Testes, Ovaries, Thyroid, Adrenal glands, Parathyroid, Pancreas
Endocrine System
The collection of glands of an organism that secrete hormones directly into the circulatory system to be carried towards distant target organs.
Adrenal Glands
Situated on top of the kidneys and consist of the adrenal cortex and medulla. Helps to control blood sugar in addition to:
- promoting proper cardiovascular function
- properly utilizing carbohydrates and fats
- distribution of fat storage
- promotes healthy gastrointestinal functions
Adrenal Cortex
Located along the perimeter of the adrenal gland, the adrenal cortex mediates the stress response through production of:
- cortisol and cortisone (glucocorticoids)
- aldosterone (mineralcorticoids)
- androgens (cortical sex hormones)
Glucocorticoids (e.g. Cortisol and Cortisone)
Stimulus: ACTH
Site: Adrenal Cortex
Involved in glucose regulation and protein metabolism. Raise blood glucose levels by promoting protein breakdown and using the products of gluconeogenesis.
Mineralcorticoids (e.g. Aldosterone)
Stimulus: ACTH
Site: Adrenal cortex
Regulation of plasma levels of Na and K as well as the total extracellular water volume. Causes active reabsorption of Na and passive reabsorption of H2O in the nephrons.
Cortical Sex Hormones (e.g. Androgens)
Stimulus: ACTH
Site: Adrenal cortex (secondary site)
Stimulates or controls the development and maintenance of male characteristics by acting as a precursor to production of testosterone in the Leydig cells of the seminiferous tubules of the testes.
Adrenal Medulla
Located in the innermost part of the adrenal gland and surrounded by the adrenal cortex, the adrenal medulla mediates the ANS through production of:
-epinephrine; norepinephrine (catecholamines)
Catecholamines (e.g. Epinephrine and Norepinephrine)
Stimulus: Sympathetic Preganglionic Neurons
Site: Adrenal medulla
Increase the rate and strength of the heartbeat as well as dilate and constrict blood vessels to increase blood supply to skeletal muscle, the heart and brain while decreasing blood supply to the kidneys, skin, and digestive tract. Responsible for “fight-flight” response
“Fight-or-Flight” Hormones
Epinephrine and Norepinephrine
Pituitary Gland
Situated at the base of the brain and consist of the anterior and posterior pituitary
Anterior Pituitary Gland
Located in the anterior portion of the pituitary gland, the anterior pituitary mediates stress, growth, reproduction, and lactation through production of:
-FSH; LH; ACTH; TSH; Prolactin; Endorphins; GH
Mnemonic: FLAT PEG
Direct Hormones
Directly stimulate their target hormones. Have major effects in mon-endocrine tissue.
Tropic Hormones
Stimulate other endocrine glands to release hormones. Have major effects in other endocrine tissues.
Gonadotropes (e.g. FSH and LH)
Stimulus: GnRH
Site: Anterior Pituitary
FSH: stimulates follicle maturation in females; spermatogenesis in males
LH: stimulates ovulation and formation of corpus luteum in females; testosterone synthesis in males
Corticotropes (e.g. ACTH)
Stimulus: CRH/CRF
Site: Anterior pituitary gland
Stimulates the adrenal cortex to synthesize and secrete glucocorticoids, mineralocorticoids and cortical sex hormones.
Thyrotropes (e.g. TSH)
Stimulus: TRH
Site: Anterior pituitary gland
Stimulates the thyroid gland to synthesize and release thyroxine (T4) and triiodothyronine (T3), which maintain the body’s metabolic rate, heart and digestive functions, muscle control, brain development, and bone maintenance.
Luteotropin (e.g. Prolactin)
Stimulus: TRH
Site: Anterior pituitary gland
Stimulates milk production and secretion in female mammary glands.
Endorphins
Stimulus: none
Site: Anterior pituitary gland
Neurotransmitters that behave like opioids, providing internal mechanism for pain relief and producing pleasurable sensations.
Somatotropin (e.g. GH)
Stimulus: GHRH, ghrelin, androgen, estrogen
Site: Anterior pituitary gland
Promotes bone and muscle growth
Posterior Pituitary Gland
Located in the posterior portion of the pituitary gland, the posterior pituitary gland stores and releases the peptide hormones:
- oxytocin
- ADH
Note: the posterior pituitary gland does not synthesize hormones; it only stores and releases them
Oxytocin
Stimulus:
Site: Posterior pituitary gland
Produced in the hypothalamus and stored in the posterior pituitary gland until it is secreted during childbirth to increase the strength and frequency of uterine muscle contractions. Secretion is also induced by suckling, as it also stimulates milk secretion in the mammary glands.
Antidiuretic Hormone (ADH)
Stimulus: CCK, plasma volume reduction, plasma osmolarity increase
Site: Posterior pituitary gland
Increases the permeability of the collecting duct in the nephron to water, thereby promoting water reabsorption and decreasing blood osmolarity by increasing blood volume.
Hypothalamus
Controls pituitary hormones by releasing:
- Thyrotrophic-releasing Hormone (TRH)
- Growth-hormone-releasing Hormone (GHRH)
- Corticotrophin-releasing Hormone (CRH)
- Gonadotropin-releasing Hormone (GnRH)
Peptide Hormones
Composed of amino acids and are derived from larger precursors that are cleaved during posttranslational modification. Characteristics include:
- polar and cannot pass through the plasma membrane
- bind to extracellular receptors
- rapid onset but are short lived
- travel freely in the bloodstream
Steroid Hormones
Derived from cholesterol. Characteristics include:
- minimally polar and can pass through the plasma membrane
- bind to intracellular and intranuclear receptors
- slow onset but are long-lived
- dissolve in bloodstream and carried by specific proteins
Amino-acid Derivative Hormones
Modified amino acids. Share features similar to both peptide and steroid hormones. Common examples include:
- epinephrine
- norepinephrine
- triiodothyronine
- thyroxine
Thymus
Responsible for the development of a healthy immune system through synthesis and secretion of peptide hormones including Thymosin and Thymopoietin, commonly referred to as humoral factors and are important during puberty.
Pineal Gland
Release melatonin, which helps the body to adapt to circadian cycles, such as when to go to sleep.
Testes
Responsible for healthy male sexual reproduction and development of secondary sex characteristics through synthesis and secretion of steroid hormones including testosterone.
Note: testosterone is secreted by the interstitial cells of the testes
Ovaries
Responsible for healthy female sexual reproduction and development of secondary sex characteristics through synthesis and secretion of steroid hormones including estrogen and progesterone.
Thyroid
Located In the front of the neck and is responsible for controlling metabolic activity through synthesis and secretion of amino acid derivative hormones including triiodothyronine (T3) and thyroxine (T4).
Parathyroid Gland
Group of four small glands located behind the thyroid gland responsible for proper bone development through synthesis and secretion of peptide hormones including the parathyroid hormone (PTH).
Pancreas
Large gland located behind the stomach and is responsible for maintains healthy blood sugar levels through synthesis and secretion of peptide hormones including glucagon, insulin, and somatostatin.
