Hormones II Flashcards
Humoral stimuli
Stimuli, like metabolites adn other molecules, that stimulate the release of some hormones through circulation in the blood
Neural stimuli
Neurons release a neurotransmitter to synapse with a hormone-producing cell thus stimulating the cell to secrete their hormone.
Releasing hormones
A neuropeptied that stimulates hormone secretion from other endocrine cells, usually reserved for hormones from the hypothalamus
Hormonal stimuli
When hormones stimulate the secretion of other hormones
Tropic hormones
hormones from the anterior pituitary gland, and are examples of hormonal stimuli
Hormonal stimuli can be either stimulatory or inhibitory
How does humoral and neuronal stimuli work to inhibit hormone release?
Inhibition of hormones released by humoral stimuli - companion hormone inhibitied by same stimuli
Inhibition of hormone release by neural stimuli - neurons can inhibit targets
Inhibiting hormones
Hormonal stimuli that prevent teh secretion of other hormones
What are the two mechanisms for maintaining hormone levels in the blood?
Negative feedback > self-limiting system
Positive feedback > self-propogating system
Hormone receptors
target cell proteins where hormones can bind to exert their actions
Specificity
the tendancy for each tyep of hromone to bidn to one type of receptor, and not to others
Desensitization
the response of some target tissues can decrease over time due to cells’ deficiency in nutrients and energy, causing the cell to lose the ability to respond to the hormone.
Down-regulation
the number of receptors decreases after exposure to certain hormones, causing desensitization
Up-regulation
increase in sensitivity when teh rate of receptor sythesis in the target cells increases, thus increasing the total number of receptor molecules in a cell.
Nucelar receptors
bind to lipid-soluble hormones bc they can easily seep through the cell wall
found in the cell nucleus
Membrane-bound receptors
bind to water-soluble hormones
Proteins that extend across teh plasma membrane.
Was is the action of nucelar receptors?
Lipid soluble hormones stimulate synthesis of new proteins. They bind to DNA to produce a response
Hormone-response elements
Fingerlike projection receptors that bind to specific nucleotide sequences in DNA
Transcription factor
The combination of the hormone and its receptor which will activate teh transcription of mRNA
2 ways membrane bound receptors can activate a response
1) alter the activity of G proteins at inner surface of plasma membrane
2) alter the activity of intracellular enzymes
Intracellular mediators
Second messengers system - chemicals produced inside a cell from the membrane-bound hormone that activates cellular processes inside the cell
3 ways G proteins can alter the activity of enzymes insdie the cell
1) Activate or inhibit adenylate cyclase - the enzyme that converts ATP to cAMP
2) G proteins scan activate otehr intracellurlar mediators
3) G proteins can open ion channels
Which 3 subunit bind to guanine?
alpha
beta
gamma
Cyclic Guanine Monophosphate cGMP
an intracellular mediator that is sythesized in response to a hormone binding to a membrane-bound receptor, eventually activating specific enzymes in cytoplasm of a cell
Amplification
“an army of molecules” that enable a hormone to produce final products within a few seconds.
when receptors produce thousands of second messengers, which leads to a cascading effect of the hormonal signal
