week 1 Flashcards
what is a hormone?
a hormone is a chemical signalling molecule that is secreted by a cell or group of cells from an endocrine organ (or neuron).
it is secreted into the blood and transported to specific target cells that recognize the specific hormone.
it must bind to its receptor in order to exert its action
hormones remain ready for action in the bloodstream for a given period of time (they each have their own half life)
what is the difference between a hormone and a neurotransmitter
hormones travel in the bloodstream
- endocrine cell to blood to target cell
- more widespread and long-term
neurotransmitters travel across the synaptic cleft
- neuron to target cell
- quick release and action
what are the two main classes of hormones
amino acid based and lipid based
what are the two sub-categories of amino acid based hormones
- amine hormones (epinephrine, norepinephrine, dopamine, thyroid hormone)
- peptide hormones (insulin, growth hormone)
describe amino acid-based hormones
most are large and hydrophilic. they bind to a receptor on the plasma membrane of their target cells
describe steroid hormones
they are hydrophobic. most can pass through the plasma membrane. they bind to receptors in the cytosol or even within the nucleus of their target cells
define half-life
the amount of time it takes for the concentration of a hormone to reduce by half in the blood
hydrophobic hormones have the longest half-lives because they are bound to a carrier protein in the blood
what regulates hormone secretion
- other hormones
- other molecules
- neurotransmitters
what are the two hormones stored in the posterior pituitary that the hypothalamus produces
- anti-diuretic hormone - in the kidneys - increased water reabsorption back into the blood
- oxytocin - in the uterus and the mammary gland - increased uterine contraction as well as milk release
what is a tropic hormone
a hormone that triggers the release of another hormone
describe the path of the tropic hormone: thyroid releasing hormone
released from the hypothalamus, thyroid-releasing hormone triggers the release of thyroid-stimulating hormone from the anterior pituitary which targets the thyroid gland and causes increased thyroid hormone synthesis and secretion
describe the path of the tropic hormone: corticotropin releasing hormone
the hypothalamus releases corticotropin-releasing hormone which triggers the release of adrenocorticotropic hormone from the anterior pituitary which targets the adrenal cortex and results in increased secretion of cortisol and aldosterone
describe the path of the tropic hormone: prolactin-releasing hormone
the hypothalamus releases prolactin releasing hormone which triggers the release of prolactin from the anterior pituitary. this hormone then targets the mammary gland which results in increased milk production
describe the path of the tropic hormone: gonadotropin-releasing hormone
the hypothalamus releases gonadotropin-releasing hormone which triggers the release of luteinizing hormone and follicle stimulating hormone from the anterior pituitary. Luteinizing hormone targets the female gonads which results in:
- increased synthesis and secretion of estrogen/progesterone
- increased follicle maturation
- ovulation
follicle-stimulating hormone targets the male gonads and results in increased synthesis, prep and secretion of testosterone
describe the path of the tropic hormone: growth hormone releasing hormone
the hypothalamus releases growth hormone releasing hormone which triggers the release of growth hormone from the anterior pituitary. Growth hormone targets the liver, adipose tissue, muscle tissue, bone, and cartilage and results in increased metabolic processes that release energy reserve for fuel production, increase blood glucose, and promote growth (via insulin-like growth factor)
