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)
what is growth hormones main function
to regulate growth of target tissues (skeletal and cardiac muscle, adipose, liver, cartilage, bone)
what are the short term effects of growth hormone
the short term effects are metabolic:
- fat breakdown
- new glucose made in the liver
- inhibit glucose uptake in skeletal muscle
GOAL: make glucose and fatty acids available for use for fuel and building blocks for growth
what are the long term effects of growth hormone
long term effects: GH triggers the release of another hormone: insulin like growth factor (IGF)
- affects most cells in the body
- protein synthesis
- cell division
- increased glucose uptake by cells
GOAL: growth (during developmental years)
where are the thyroid and parathyroid glands located
the thyroid gland is located in the anterior neck, superficial to the trachea
the parathyroid glands are within the posterior surface of the thyroid
what are the hormones of the thyroid gland
T3 (triiodothyronine) and T4 (thyroxine)
these hormones:
- regulate metabolism
- set the basal metabolic rate of the body
- regulate the rate of both catabolic and anabolic metabolic processes
- regulate body temperature through metabolism
REVIEW NEGATIVE FEEDBACK LOOP FOR THYROID HORMONE SECRETION –>
slide 16 jan 11
what does the parathyroid gland secrete
parathyroid hormone
- important in the regulation of blood [Ca2+]
PTH is secreted in response to low blood [Ca2+]
effect: increased blood [Ca2+] levels
- stimulates osteoclasts -> increased [Ca2+] release
-> increased absorption of Ca2+ by small intestine
-> increased reabsorption of Ca2+ in the kidneys
what else is secreted by the thyroid gland?
calcitonin - it responds to high blood [Ca2+] and it inhibits osteoclasts and also decreases blood [Ca2+]
what hormones does the adrenal medulla secrete
the adrenal medulla secretes epinephrine and norepinephrine
what hormones does the adrenal cortex secrete?
the adrenal cortex secretes steroid hormones
- aldosterone
- important for the regulation of fluid, electrolyte and pH balance in the blood
- cortisol
- promotes catabolic reactions in order to provide FUEL for stress response
- glucose production in the liver (glucogenesis)
- protein breakdown in muscle
- fat breakdown in adipose tissue
- inhibits inflammatory response
- promotes catabolic reactions in order to provide FUEL for stress response
REVIEW CORTISOL SECRETION slide 20 jan 11
what are the cells that make up the pancreatic islets
pancreatic islets consist of alpha and beta cells
- insulin is produced and secreted from beta cells
- secreted in response to increased blood glucose
- glucagon is produced and secreted from alpha cells
- secreted in response to decreased blood glucose
