Endocrine System Flashcards
(28 cards)
Hormones
Signaling molecules secreted into bloodstream
Travel to nearby and distant cells
Part of Endocrine system
how are hormones different than paracrine factors and
neurotransmitters
Paracrine factors and neurotransmitters travel
through extracellular fluid (ECF) to nearby cells
What is the Endocrine System?
Endocrine system: glands, tissues, and cells that secrete hormones
Endocrine glands: Organs that produce hormones.
The “classic” endocrine glands: Hypothalamus, Pituitary gland, Pineal gland, Thyroid gland, Parathyroid glands, Thymus, Adrenal gland, Pancreas, and Gonads (Ovaries/Testes)
Endocrine vs. Nervous System (Speed, Adaptation to long-term stimuli, and area of effect)
Nervous System:
quick response (milliseconds) and quick to stop
adapts quickly to long-term stimuli
area of effect is targeted/specific
Endocrine System:
slow response (seconds-days) and Persistent effect
adapts very slowly to long-term stimuli
Area of effect: Some hormones are very general and some hormones are more specific
Hormone Classes
There are three classes
Steroids- derived from fat (cholesterol)
Monoamines- derived from amino acid
Peptides- derived from multiple amino acids
Hormone Transport
Monoamines and Peptide hormones are Hydrophilic and travel in blood plasma
Steroids are Hydrophobic so they bind to transport proteins likealbumin to travel through blood
Hormone Receptors
Hormones bind to receptors on or in target cells to exert their effects
Specificity:
Hormones only stimulate cells with receptors for that specific hormone and each receptor typically only binds to one hormone
Sensitivity:
Target cells have several thousand receptors for a hormone. Sensitivity increased with more receptors- causes a greater response to hormone. Long-term exposure to high hormone concentrations causes cells to express less receptors and become less sensitive
By type of hormone:
Peptide and monoamine hormones bind to
membrane receptors and Steroids bind to intracellular receptors- inside the cell (inside the nucleus, in fact!)
Hormone Actions
Signal amplification:
Hormones very potent
Receptor binding leads to activation of many second messengers
Steroids directly affect gene transcription- extremely powerful, don’t need second messengers
Hormone interactions:
Most cells have receptors for multiple
hormones
Synergistic effects, Permissive effects, and Antagonistic effects
Synergistic effects
Multiple hormones acting to amplify effect
Ex: FSH and Testosterone cause sperm production
Permissive effects
One hormone enhances/allows cell’s response to another
Ex: estrogen makes uterus cells more sensitive to progesterone
Antagonistic effects
Hormones have opposite effect on cell
Ex: insulin and glucagon
Anterior Pituitary Hormones
Gonadotropin hormones (FSH & LH), TSH, ACTH, PRL, and GH
Gonadotropin hormones
Both FSH and LH: Target gonads and are named for effects on female gonads
FSH: Follicle-Stimulating Hormone
Female: Stimulates development of ovarian follicles
Male: stimulates sperm production
LH: Luteinizing Hormone
Female: stimulates ovulation, formation of corpus luteum
Male: stimulates testosterone secretion from testes
TSH
Thyroid Stimulating Hormone
Stimulates thyroid to secrete Thyroid Hormone
ACTH
Adrenocorticotropic Hormone
Stimulates adrenal cortex to secrete glucocorticoids
Glucocorticoids are anti-stress steroids (cortisol)
PRL
Prolactin
Stimulates mammary glands to make milk
GH
Growth Hormone
Causes growth in many tissues and organs
Stimulates mitosis and cellular differentiation
Hypothalamus Hormones (two classes)
Anterior Pituitary-Regulating Hormones: Secreted into hypophysial portal vessels
Posterior Pituitary Hormones: Transported via axons from hypothalamus to posterior pituitary
Hypothalamus Hormones: Anterior Pituitary-Regulating Hormones
TRH, CRH, GnRH, GHRH, PIH, and Somatostatin
TRH
Thyrotropin Releasing Hormone
Causes release of TSH & PRL
Anterior Pituitary-Regulating Hormone
CRH
Corticotrophin Releasing Hormone
Causes release of ACTH
Anterior Pituitary-Regulating Hormone
GnRH
Gonadotropin Releasing Hormone
Causes release of FSH & LH
Anterior Pituitary-Regulating Hormone
GHRH
Growth Hormone Releasing Hormone
Causes release of Growth Hormone
Anterior Pituitary-Regulating Hormone
PIH
Prolactin Inhibiting Hormone
Inhibits release of Prolactin
Anterior Pituitary-Regulating Hormone
