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ChemicalSignalingPt2
HormoneAndChemicalSignaling_Part2
| Question | Answer |
|---|---|
| How are signal pathways controlled? | 1. receptors 2. pathways are mechanisms under homeostasis guidelines, mostly controlled by negative feedback loops |
| Receptors are PROTEINS, and are subject to... | 1. specificity of binding 2. competition for binding site (agonist vs antagonist) 3. saturation of ligand (up/down regulation of receptors) |
| What is the definition of modulation pathways? | Definition: How are pathways controlled |
| Define the specificity of binding & competition | 1. receptors have SPECIFIC binding sites 2. competition: different compounds with similar molecular regions may bind to same site |
| Give an example of binding & competition | Epinephrine & norepinephrine have similar ligand structure and bind to a class of receptors called adrenergic receptors 1. adrenergic receptors exhibit SPECIFICITY 2. adrenergic receptors are influenced by competition |
| T/F Due to study of active sites and their properties, slightly changing the non-binding areas may change the DURATION of action | True |
| Define agonist | Agonists bind and CAUSE activation, they act the same way as ligands |
| Define antagonist | Antagonists bind and STOP or PREVENT activation |
| What are muscarinic receptors? | 1. Bind Acetylcholine (Ach) in the autonomic nervous system (ANS) 2. Binds Muscarine (mushroom toxin) that mimics Ach (AGONISTIC action) and can cause a severe parasympathomimetic to the point of death |
| What are nicotinic receptors? | 1. Bind Ach at neuromuscular junctions 2. Binds curare (poison arrow frog toxin) and blocks the receptor (ANTAGONISTIC action) - causes paralysis and very potentially death |
| What parts of the body gets affected the most when curare binds with nicotinic receptors? | 1. muscular system becomes paralyzed 2. Deadliest when hits diaphragm & intercostal muscles |
| What is the purpose of up-down regulation? | To allow the cells the ability to control extent of signal pathway effect depending on: 1. CONCENTRATION of signal in ECF 2. Needs of the cell |
| Which form of diabetes would result in up/down regulation of insulin receptors? | 1. Type I - up regulation 2. Type II - down regulation |
| What is up regulation also known as? | Amplification |
| What is overall function of down-regulation? | Getting rid of membrane protein receptors |
| What is overall function of desensitization? | Disabling receptors |
| Compare down-regulation vs desensitization | 1. Down-regulation is SLOWER as cell needs to REMOVE receptors from membrane 2. Desensitization is QUICKER as a bind agent can DEACTIVATE the receptor |
| What is an example of desensitization? | Adding a phosphate can deactivate a receptor (beta adrenergic receptors) |
| How does the cell get any process to stop? | 1. enzymatic degradation of ligand (enzyme denature ligand) 2. removal of ligand by re-uptake (via ACTIVE TRANSPORT) 3. Endocytosis of receptor-ligand complex (DOWN REGULATION) - receptors can be reinserted into membrane when needed |
| T/F Pathways are controlled by homeostatic mechanisms REGARDLESS of type of pathway and resulting in transduction of signal | TRUE |
| Describe similarities between neural and endocrine pathways in regards to SPECIFICITY | 1. Neu: each neuron terminates on a SINGLE target cell or on a limited number of adjacent target cells 2. End: most cells of the body are exposed to a hormone. The response depends on which cells have receptors for the hormone |
| Describe similarities between neural and endocrine pathways in regards to NATURE OF THE SIGNAL | 1. Neu: Elec. signal (action potential) pass thru neuron, then chemical neurotransmitters pass signal from cell-cell. In a FEW cases, signals pass via gap junctions. 2. End: chemical signals are secreted IN THE BLOOD for distribution thru-out body |
| Describe similarities between neural and endocrine pathways in regards to SPEED | 1. Neu: very RAPID 2. End: Distribution of signal and onset of action are much SLOWER than neural responses |
| Describe similarities between neural and endocrine pathways in regards to DURAION OF ACTION | 1. Neu: Usual very SHORT (millisecs). Responses of longer duration are mediated by neuromodulators 2. End: During of action is usually much LONGER than in neural responses |
| Describe similarities between neural and endocrine pathways in regards to CODING FOR STIMULUS INTENSITY | 1. Neu: Each signal IDENTICAL in strength. stimulius intensity correlated with increased freq. of signaling 2. End: Stimulius intensity is correlated with amount of hormone secreted (MORE hormone, LONGER effect) |
| Describe the homeostatic pathways of neural vs neuroendocrine vs endocrine in regards to SENSORS/RECEPTORS | 1. Neuro: special/somatic sensory receptors 2. NeuroEndo: special/somatic sensory receptors 3. Endo: endocrine cells |
| Describe the homeostatic pathways of neural vs neuroendocrine vs endocrine in regards to AFFERENT PATHWAY | 1. Neuro: afferent sensory neuron 2. NeuroEndo: afferent senseory neuron 3. Endo: NONE - pathways are fluids |
| Describe the homeostatic pathways of neural vs neuroendocrine vs endocrine in regards to INTEGRATING CENTER | 1. Neuro: Brain or spinal cord 2. NeuroEndo: Brain, spinal cord, autonomic nervous system 3. Endo: endocrine cell |
| Describe the homeostatic pathways of neural vs neuroendocrine vs endocrine in regards to EFFERENT PATHWAY | 1. Neuro: efferent neuron (electrical signal/action potential travelling and neurotransmitter) 2. NeuroEndo: efferent neuron (electrical signal and neurohormone) 3. Endo: Hormone |
| Describe the homeostatic pathways of neural vs neuroendocrine vs endocrine in regards to EFFECTORS | 1. Neuro: muscles and glands, some adipose tissue 2. NeuroEndo: Most cells of the body 3. Endo: Most cells of the body |
| Describe the homeostatic pathways of neural vs neuroendocrine vs endocrine in regards to RESPONSE | 1. Neuro: contration/secretion primarily. May have some metabolic effects 2. NeuroEndo: change in enzymatic reactions, membrane transport, cell proteins 3. Endo: Change in enzymatic reactions, membrane transport, cell proteins |
| What are HORMONES? | Chemical messenger sereted by specialized cells.. 1. from ISOLATED endocrine cells which makes up the diffuse endocrine sys 2. from NEURONS 3. from IMMUNE system cells producing cytokines |
| Where do HORMONES go in the body? | 1. mostly into BLOOD 2. into environment (ectohormones or pheromones - apocrine sweat: armpits) |
| What are hormones involved in? | All LONG-DURATION events: 1. Growth 2. Development 3. Metabolism 4. Reproduction |
| How do hormones act? | 1. By altering rates of enzyme mediated reactions 2. control movement of molecules across plasma membrane 3. regulate rate of gene expression (& therefore protein production) |
| How do hormones get from point A to point B? | 1. To be classifed as hormone & not a paracrine or autocrine hormone, TRAVEL IN BLOOD 3. some hormones need H2O soluble (protein) transport mech. if hormone's lipid soluble 4. lipophilic horm: don't like 2 travel thru blood, needs 2 attach 2 protein |
| T/F Hormones act by binding to receptor on target cells | True |
| Hormones have to have a mechanism for ending effect, but how? | 1. stop/reduce production of hormone 2. degrate hormones 3. enzymatic removal from receptor 4. endocytosis of receptor-hormone complex |
| How are hormones classified? | 1. source 2. structure |
| Where are the locations of hormones? (G = glands) | 1. pineal 2. hypothalamus 3. anterior/posterior pituitary 4. thyroid/parathyroid 5. thymus 6. heart/liver/stomach/small intestine/kidney/skin 7. pancreas 8. adrenal cortex/medulla 9. testes/ovary 10. adipose tissue 11. placenta: preggies on |
| What are the structures of hormones? | 1. peptide/protein hormones (bunch of amino acids) 2. steroid hormones - lipophilic, based on cholesterol 3. amino acid based |
| What are amino acid based hormones? | Derived from tyrosine and may be: 1. catecholamines - epinephrine/norepinephrine 2. thyroid hormones |
| Explain peptide/protein hormones | 1. classification that includes MOST hormones 2. if a hormone is NOT a steroid or amino acid derived hormone, then it's a protein/peptide hormone |
| What are the concerns about peptide/protein hormones? | 1. how they are made, stored, released 2. how they are transported in blood 3. the mechanism of action 4. how long they last |
| Describe steps 1-3 of how peptide/protein hormones are made, stored, released. | 1. mRNA on ribosome bind amino acid into peptide chain (PREPROHORMONE). Chain directed into ER lumen by signal sequence of amin. acid. 2. enzymes in ER chop off signal seq, create inactive PROHORMONE 3. PROHORMONE pass from ER thru Golgi complex |
| Describe steps 4-6 of how peptide/protein hormones are made, stored, released. | 4. Secretory vesicles w/enzymes & prohormone bud off Golgi. Enzymes chop proHormone into 1+ active peptides & addit'l peptide fragments 5. S.V. release contents (exocytosis) into extracellular space 6. Hormone move into circulation for transport-targ |
| What are some examples of peptide/protein hormones | 1. PreproTSH (thyrotropin releasing hormone) has 6 copies of 3-amino acide hormones TRH 2. Prohormones may contain several peptide sequences that have biol. activity 3. Peptide chain of insulin's prohormone folds back and cleave into insulin & C-pepti |
| Describe cellular action mechanism of peptide/protein hormones | 1. Lipophobic - must bind to receptors on membrane's ECF surface 2. Most work via cAMP messenger sys 3. Some via receptor-enzyme complexes |
| What are receptor-enzyme complexes? | Enzyme attached & activated by binding is tyrosine kinase (phosphorylates various substrates) 1. insulin binds, tyrosine kinase activated & PHOSPHORYLATES glucose to glucose 6-phosphate |
| What is the duration of peptide/protein hormones? | 1. depends on method of hormone action termination 2. depends on molecule (some synthetic hormones have been modified to last longer) 3. longer bound = longer effect 4. How much is in circulation? - MORE in blood = longer effect |
| Describe steroid hormones | 1. Lipophilic - creates problems (goes straight to CYTOSOL) a. no storage b. production is on "as needed" basis c. can have precursors in cytoplasm ready to go d. require protein transports in blood |
| What does protein transports in blood do? | 1. prolongs duration of hormone 2. blocks entrance into cell, it must disengage from carrier (this follows law of mass action) |
| What do lipids in blood aggregate to form? | Lipid droplets |
| Continue describing steroid hormones | 1. based on cholesterol 2. produced using SMOOTH ER in the a. adrenal cortex b. gonads c. placenta 3. secretion by simple diffusion |
| Describe steroid hormones' cellular mechanism of action | 1. diffuse into cytosol/into nucleus 2. act as transcription factor in nucleus to alter gene activity 3. transcription factor have DNA binding domain that tells them where to bind on the DNA |
| How is gene activity altered by steroid hormones in the nucleus? | 1. repressing or activating rates of transcription 2. lag peroid due to processes that have to occur |
| How many known human transcription factors with specific DNA binding domains are there? | Aprroximately 2000 |
| How are steroid hormones regulated? | 1. negative feedback loop - increase transcription factors cause decrease in production 2. phosphorylation - may stop transcription 3. Ligand binding to transcription (co)factors that regulate transcription factors |
| T/F New(er) research indicates that some steroid hormones have membrane receptors and signal transduction pathways similar in process to protein/peptide hormones | TRUE |
| What are Steps 1-2 to steroid hormone (S.H) action? | 1. Most hydrophobic steroids bind 2 plasma protein carriers. Only unbound hormones diffuse into target cell 2. S.H. receptors in cytoplasm/nucleus 2a. Some S.H. also bind 2 membrane recep.(use 2ndary messgr sys 2 create rapid cell response) |
| What are Steps 3-5 to steroid hormone (S.H) action? | 3. receptor-hormone complex binds to DNA & activates/repress 1+ genes 4. activated genes create new mRNA that move back to cytoplasm 5. translation produces new proteins for cell processes |
| Amino Acid Derived Hormones may be.... | 1. derived from tyrosine 2. Produces a. T3 & T4 b. Epinephrine & Norepinephrine 3. derived from tryptophan a. produces melatonin & serotonin |
| T/F Serotonin is classified as a neurohormone as it is synthesized & secreted by neurons of the GI tract for regulation of motility & CNS | TRUE |
| T/F Hormones are controlled by reflex pathways most utilizing NEGATIVE FEEDBACK LOOPS! | TRUE, may have multiple controls though |
Created by:
lophung
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