Endocrine System Flashcards
Endocrine system
-Produces hormones to help maintain homeostasis, regulate reproduction and development
hormone
Chemical messenger produced in one part of the body that affect target cells in another part of the body
how are hormones released?
-Endocrine glands have no ducts- they
Secrete hormones directly into blood or interstitial fluid–fluid that surrounds cells
-Hormones belong to one of four groups:
oFatty acid derivatives
Ex- prostaglandins
oSteroids
Ex- cortisol, testosterone, estrogen, progesterone
oPeptides–chains of amino acids
Ex- oxytocin, ADH
oModified amino acids
Ex- thyroid hormone, epinephrine/adrenaline
target cells
-Hormones only has affect once it reaches the target cells-
Contain receptors that recognize and bind hormones.
how do hormones trigger target cells?
Hormone can pass through cell membrane and bind to a receptor protein on the nucleus (Usually steroid hormones, which are lipid soluble)
or
Hormones can bind to the receptor on the cell membrane and cause formation of second messenger, like cAMP, which activates intracellular events (Usually peptide hormones, which cannot pass through the membrane)
-Hormones usually act by negative feedback, in which hormone triggers a response that counteracts the changed condition, restoring homeostasis
Hypothalamus
oLocated in forebrain
oCenter of homeostatic control of the internal environment- monitors external and internal conditions
oDetermines what actions are necessary to maintain homeostasis
oSecretes hormones that are releasers or inhibitors of hormones from the pituitary
Pituitary gland
- is connected to hypothalamus at the base
oNeurosecretory cells link pituitary to hypothalamus- structured like neurons but release hormones into blood instead of neurotransmitters
oKnown as “master gland” because some of its hormones control the production of hormones in other glands
o2 halves, or lobes: anterior and posterior lobe
Posterior pituitary
secretes hormones produced by the hypothalamus
Produce ADH (antidiuretic hormone), which acts in the kidneys, helping absorb more water in the body
Produces oxytocin, which triggers uterine contraction and milk production
Anterior pituitary
secretes its own hormones, including tropic hormones
tropic hormones-
target other endocrine glands
Adrenocorticotropic Hormone (ACTH)-
Anterior pituitary, stimulates secretions from adrenal glands
Thyroid stimulating hormone (TSH)-
Anterior pituitary, stimulates thyroid gland to release hormones
Follicle-stimulating hormone (FSH)-
Anterior pituitary, role in gamete formation
Luteinizing Hormone (LH)-
Anterior pituitary, role in gamete formation
Prolactin (PRL)-
Anterior pituitary, stimulates milk production in mammary glands
Growth Hormone (GH)-
Anterior pituitary, stimulates growth of bones and muscles
Thyroid
oLocated in neck region, in front of trachea and below larynx
oSecretes T4 (thyroxin) and T3 (triiodothyronine)
oEssential for normal growth and development
oRegulated by negative feedback system:
negative feedback system–thyroid
When conc of thyroid hormones rise above normal, anterior pituitary secretes less thyroid stimulating hormone
When conc of thyroid hormones are low, anterior pituitary secretes more thyroid stimulating hormone
oMalfunctions of thyroid gland:
Hypothyroidism
Hyperthyroidism
Goiter
Hypothyroidism
reduced thyroid function, results in little energy, slow, confused, tired
Hyperthyroidism
increased thyroid function, results in increased thyroid function, nervous, irritable
Goiter
abnormally enlarged thyroid gland, either due to hyposecretion of hormones (can be caused by iodine deficiency) or hypersecretion of hormones . remove w radioactive iodine or surgery
-Parathyroid glands:
Located in connective tissue surrounding the thyroid gland
Secretes parathyroid hormone (PTH)- helps regulate calcium levels in blood
Stimulates calcium release from bones when calcium levels in blood are low
Calcitonin
Calcitonin, which is release from thyroid gland, works antagonistically to parathyroid hormone
Inhibits removal of calcium from bones when calcium levels in blood are high
-Pancreas:
oClusters of cells called Islets of Langerhans are composed of 2 types of cells:
Beta cells- secrete insulin
Alpha cells- secrete gluacagon
Insulin
Stimulates cells of liver and other organs to take up glucose from blood when blood glucose levels are high
Ex- after eating
Glucose is either used right away as fuel or stored as glycogen
This lowers the blood glucose level
Glucagon
Stimulates liver cells to convert glycogen into glucose when blood glucose levels are low
Ex- a few hours after eating
This raises the blood glucose level
oDiabetes:
Characterized by high glucose conc
Type I- antibodies destroy beta cells, leading to insulin deficiency
Type II- develops gradually, insulin receptors on target cells do not bind insulin (can be caused by obesity)
-Adrenal glands:
oPaired gland that lie on upper ends of kidneys
oConsist of two portions-
Adrenal medulla (center)
Adrenal cortex (outer)
Adrenal cortex
Glucocorticoid, ex- Cortisol- stimulates increase in blood glucose level
Mineralcorticoid, ex- Aldosterone- stimulates kidney to take in more salt, increasing blood volume
Sex hormone precursors, ex- Androgens- converts into testosterone or estradiol
Adrenal medulla
Secretes epinephrine (adrenaline) and norepinephrine (noradrenaline)
During stress or anxiety, sympathetic nervous system stimulates secretion of both hormones
Ovary
secretes estrogens,(targets gen and uterus, stimulates development of uterine lining + develop and maintain sex characteristics in female)
progesterone, (uterus and breast, stimulates development of uterine lining)
Testis
Testosterone–general, reproductive structures, develop and maintain sex characteristics in male and promotes spermatogenesis
10 glands
hypothalamus, pituitary, pineal, thyroid, parathyroids, thymus,adrenal, pancreas, ovary/testis
