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Human Physiology H4a
Handout 4 Part 1 Cell Communication
| Question | Answer |
|---|---|
| Cells primarily communicate vai CHEMICAL MSGERS | Life depends on the ability of cells to communicate w/each other and Intercellualr communication occurs wither directly or indirectly (see below) |
| For normal functtion of an animals, cells need to coordinate to grow and develop | for Cell environment signaling as a guide; himeostasis; sensation, and immune funx, primarily with a chemical messenger. Short, med or long distances is by indirectly using the chemical msgers |
| Direct Cellular Communication | via GAP JUNX AND TRANSIENT CELL-CELL contact |
| Gap Junctions | 1/2 owned and maintainaed by each cell (usually 20 forming an open chnl to communicate; some gated so not always open; only communicate if teh gate is open; small things are passable only-like electrical charges, ions, Ca and ATP,NOT proteins or macromols |
| Transient Cell-Cell contact | transient cells are moving thru the body at least once during GROWTH and DEVELOPMENT as a new cell and possibly again as an ADULT as migratory IMMUNE CELLS. T lymphocytes asking if its okay? if yes, than okay to pass, if no then IMMUNE RESPONSE kick in |
| Indirect intercellular communication | Most common meand of cell to cell comm is via CHEM MSGERS and there are 4 types of signal molecules |
| Most common because... | cells have many receptors; a ell makes adn releases a chemical intothe ISF; the target cell has a receptor that binds to and is activated by the chem msgr; the target cell responds (often by signal transduction) |
| 4 types of signal transduction | Paracrines, neurotransmitters, hormones |
| if chemical is released into ISF... | moves a dist. to bind to a receptr, receptr activts a response, determining response receptiveness is pres. of specific receptr so isa targetcell and how chem msgr moves.If by blood every cell inbody willbe effected by exposure, only cells w/receptors wil |
| If cell released in ISF only.... | Chemical may disperse a short distance so only effects within the area and within the presence of a target receptor |
| Chemical Messengers Functional classification | paracrines, neurotransmitters, hormones |
| paracrine-general | local, not released into blood, in ISF by diffusion to neighbors |
| Neurotransmitters-general | used by neurons, chem signal travel, short/local distance to a synapse, part of long distance but rapid |
| Hormones-general | released into blood, travel long distances |
| Chemical Messengers Structural (chemical) classification | Amino acids, Amines, Peptide/Proteins, steroids adn eicosanoids |
| 1. Paracrines: Short- distance intercellular communication | effect exerted only on IMMEDIATE NEIGHBORS, spread by SIMPLE DIFFUSION thru ISF, may have AUTOCRINE activity |
| Autocrine Activity | cell releasing signal also having the receptor, cell secreting signal is also responding tothe signal b/c it has a receptor.Why?1. turning signal on/off like a light switch upon activation(auto regulation) 2.Viral defense mechanism activated WITHIN ITSELF |
| Paracrines function as... | GROWTH factors, CLOTTING factors adn CYTOKINES (regualting hormones involved in development and immune funx-chem signals) |
| 2. Neurotransmitters: Short-distance intercellular communication | presynaptic cell moves via diffusion across a synaptic cleft and binds to receptors in potsynaptic cel; Rapid local and long distance comm. system; HIGHLY LOCALIZED to the synapse (synaptic signal) |
| Serotonin and Doapmine both are released by... | used as a neurotransmitter by neurons in the brain and have activity as a hormone releaseed by cells |
| 3. Hormones: Long- distance intercellular communication | secreted INTOthe BLOOD by ENDOCRINE cells, act on TARGET cells, specific receptor for that signal. Hormones are seprate from other signals b/s unique cells like: thyroid, pituitary, or gonads secrete chemicals released into blood |
| a subtype of hormones are known as NEUROHORMONES | produced by a neuron but secreted into the blood by specialized neurosecretory cells, act on targets Ex. in hypothalamus are endocrine funx |
| Chemical Classification: Amino Acids | all funx as neurotransmitters: glutamate, aspartate, GABA and glycien; synthesizes in CYTOSOL, transported and stored in VESICLES; ALL ARE LIPOPHOBIC |
| #1 Glutamate | excitatory neuron in brain-increaases nervous system activity; MOST ABUNDANT |
| #2 GABA | inhibitory. slows doen nervous system activity |
| Lipophobic (Amino acids) | FAT HATING; Funx:CANNOT cross cell membrane so receptors are at the cell membrane on outside face b/c it CAN'T GET INTO THE CELL;DO NOT CROSS MEMBRANES |
| Chemical Classification: Amines | funx as paracrines, neurotransmitters and hormones; derived from amino acids and contain an amine group: #1 is Catecholamines:dopamine, NorE and Epinephrine; serotonin, histamine and thyroid hormones; ALL AMINES ARE LIPOPHOBIC EXCEPT THYROID HORMONE |
| Thyroid hormones | ARE LIPOPHILIC; |
| Lipophilic | CAN cross cell membrane, membrane has receptors INSIDE the cell in the nucleus of the cell |
| Enzymatic pthwy to make Catecholamines | L-tyrosine makes L-Dopa makes Dopamine make NorE makes Epine |
| Chemical Messengers Structural (chemical) classification | Amino acids, Amines, Peptide/Proteins, steroids adn eicosanoids |
| 1. Paracrines: Short- distance intercellular communication | effect exerted only on IMMEDIATE NEIGHBORS, spread by SIMPLE DIFFUSION thru ISF, may have AUTOCRINE activity |
| Autocrine Activity | cell releasing signal also having the receptor, cell secreting signal is also responding tothe signal b/c it has a receptor.Why?1. turning signal on/off like a light switch upon activation(auto regulation) 2.Viral defense mechanism activated WITHIN ITSELF |
| Paracrines function as... | GROWTH factors, CLOTTING factors adn CYTOKINES (regualting hormones involved in development and immune funx-chem signals) |
| 2. Neurotransmitters: Short-distance intercellular communication | presynaptic cell moves via diffusion across a synaptic cleft and binds to receptors in potsynaptic cel; Rapid local and long distance comm. system; HIGHLY LOCALIZED to the synapse (synaptic signal) |
| Serotonin and Doapmine both are released by... | used as a neurotransmitter by neurons in the brain and have activity as a hormone releaseed by cells |
| 3. Hormones: Long- distance intercellular communication | secreted INTOthe BLOOD by ENDOCRINE cells, act on TARGET cells, specific receptor for that signal. Hormones are seprate from other signals b/s unique cells like: thyroid, pituitary, or gonads secrete chemicals released into blood |
| a subtype of hormones are known as NEUROHORMONES | produced by a neuron but secreted into the blood by specialized neurosecretory cells, act on targets Ex. in hypothalamus are endocrine funx |
| Chemical Classification: Amino Acids | all funx as neurotransmitters: glutamate, aspartate, GABA and glycien; synthesizes in CYTOSOL, transported and stored in VESICLES; ALL ARE LIPOPHOBIC |
| #1 Glutamate | excitatory neuron in brain-increaases nervous system activity; MOST ABUNDANT |
| #2 GABA | inhibitory. slows doen nervous system activity |
| Lipophobic (Amino acids) | FAT HATING; Funx:CANNOT cross cell membrane so receptors are at the cell membrane on outside face b/c it CAN'T GET INTO THE CELL;DO NOT CROSS MEMBRANES; CAN BE STORED |
| Chemical Classification: Amines | funx as paracrines, neurotransmitters and hormones; derived from amino acids and contain an amine group: #1 is Catecholamines:dopamine, NorE and Epinephrine; serotonin, histamine and thyroid hormones; ALL AMINES ARE LIPOPHOBIC EXCEPT THYROID HORMONE |
| Thyroid hormones | ARE LIPOPHILIC; |
| Lipophilic | CAN cross cell membrane, membrane has receptors INSIDE the cell in the nucleus of the cell |
| Enzymatic pthwy to make Catecholamines | L-tyrosine makes L-Dopa makes Dopamine make NorE makes Epinephrine |
| Chemical Classification: Peptides/Proteins | Most common tyoe of Chemical Messenger, funxs in all 3 classes: paracrines, neurotransmitters and hormones; less tha 100 is a peptide so is a not so long peptide. +100 = protein; synthesis via RER, golgi apparatus and secretory vesicle: ALL ARE LIPOPHOBIC |
| LIPOPHOBIC CAN STORE | Can make ahead of time and store in vesicles-FASTER RELEASE |
| LIPOPHILIC CANNOT BE STORED | Must make ON DEMAND-SLOWER RELEASE |
| Lipophobic Chemical Messengers | Amino Acids, Amines, Peptides/Proteins; can be stored so fast |
| Chemical Classification: Steroids | Function entirely as HORMONES; al are derived from CHOLESTEROL in SER (Smooth Endoplasmic Reticulum); ALL ARE LIPOPHILIC |
| Cholesterol | Dietary allowance for cholesterol is ZERO b/c the body can make allt he cholesterol it needs to sustain life |
| Chemical Classification: Eicosanoids | Function as PASACRINES;most are derived from ARACHIDONIC ACID (a 20 C fatty acid); ALL ARE LIPOPHILIC; cannot be stored ahead of time |
| ARACHIDONIC ACIDS are a precursor for EICOSANOIDS | Like: Prostaglandins, leukotrienes, thromboxanes, and prostacyclins |
| Prostoglandins | inflammitory response and pain signaling |
| Thromboxanes | blood clotting roles EX> baby aspirin blocks activity of this enzyme |
| LIPOPHILIC Chemical Messengers | Steroids and eicosanoids; cannot be stored so made on demand so slow |
| Transport of Messengers | paracrines and neutrotransmitters disperse by simple diffusion; Hormones are transported either dissolved in plasma or bound to a carrier protein; The time that a hormone persists int he blood is measured in half life |
| Paracrines and Neurotrans dispersed by Simple diffusion to nearby neighbors (check notes w/Jurney) | b/c they are degrades (absorbed and reused rapidly), so only avail for a short time |
| Hormones are transported either dissolves in plasma or bound to a carrier | if hydrohilic, dissolves in water-plasma if, hydrophobic, will have a carrier protein to carry Ex. steroid hormones |
| Variability of presence in blood measurable by HALF_LIFE | Time it takes for concentration of a chemical to be reduced from original concentration |
| Lipophobic/hydrophilic messengers | Have SHORT half-lives; can be stores in vesicles; immed response; short lifespan; RAPID and transient, shorter durations to extend it if needed; continually secrete-active secretion |
| Lipophilic/hydrophobic messengers | Have longer half-lives; typically bond to a carrier protei which protects the life so has a longer half-life BUT are SLOW, present longer in blood, delayed, more steady response to drive; NOT GOOD in an emergency |
| What's the point? | Chemical signals produce responses in their target cells |
| First messenger | The signal molecule (or ligund); CHEM SIGNAL OUTSIDE CELL; 1st messenger to receptor binding activates teh target cell, the receptor activates one or more intracellualr signal molecules and last response signal exerts a cellular response |
| Second Messenger | signal activated INSIDE cell; cell division, contraction |
| Receptors | define how the target cell will respond; Lipophilic or lipophobic responses/receptors |
| Lipophilic receptors | lipophilic 1st msgrs bind to cytosolic or nuclear receptors, turning genes on and off, making new proteins and INSTALLING THE LIGHT SWITCH;BINDS INSIDE CELL EX.Steroid |
| Lipophobic receptors | LIPOPHOBIC:1st msgrs bind to membrane receptors, fast response turning on /off a switch that is already there, EX. Amines, Peptides/Proteins |
| Signal transduction | for membrane bound receptors;process of target cell response to signal depends on where receptor is located;an EXTRACELLULAR MSG CONVERTED TO A INTRACELLULAR MSG that activates a response-depends on type of receptor that 1st msger activates Ex.Radio Waves |
| signal transduction pathways | all the many ways that signal transduction occurs |
| What does the 1st msgr usually do? | The 3 responses to an Extracellular messenger and most signal pathwys (receptor enzyme G-protein coupled)involve protein kinases |
| The 3 main cell responses to an Extracellualr messenger | 1. Open or close a gated receptor chnl 2. activate a receptor enzyme 3. activate 2nd msgr thway via a G-Protein coupled receptor Ex. vascular, renal or cardiovascular response |
| Protein Kinase | an enzyme that phosphoralates a target protein; phosphorylation is a common on/off switch; a signaling event combining receptro enzyme and G protein which invole protein kinases which encouage phosph by attaching a phos to change shape of target protein |
| Dephosphorylation in cells | always going |
| What directly does the receptor do? | 1st msgr binds to a receptor, binds to a gated chnl so it opens the gate. Ex. Nervous system-"gated-receptor chnl"-some may have enzyme funx, so enzyme turned on to catalyze a rxn.Most common response is to activate a 2nd msgr pthwy thru a G-protein coupd |
| Membrane receptors (4) | Ligund-gated channels, receptor=enzyme, G-protein coupled receptor, integrin receptors |
| 1. Ligund gated channels | Ligund binds to receptor to open/close the channel |
| 2. Receptor-enzyme | Activation of intracellular enzyme with binding; ligund binds to a receptor enzyme activating an intercellular enzyme |
| 3. G-protein coupled receptor MOST COMMON | Ligund binding to a G-protein coupled receptor, OPENS AN ION CHANNEL OR ALTERS ENZYME activity |
| 4. Integrin recpetors | cell to cell, cell matrix functioning; Ligund binds to integrin receptors, ALTERS the CYTOSKELETON |
| Signal Amplification | typically only a few 1st messengers are req'd to initiate a sig. cellular response-due to amp.;activated receptors turn ON ampfing enzymes which generate 2nd messengers;allows chemical signals to funx at VERY LOW CONC. to produce massive changes in cells |
| 2nd Messenger in amplification | is an intermediary step in signal amplification; not an ending response just apart of; part of signal transduction response WITHIN in a cell |
| Modulation of signal pathways (4) | because they are so powerful so cells need to control response to receptivity; cells are capable of regualting their signal pathwys, down regualtion, up-regulation adn signal termination |
| 1. reguation of signal pthwys | receptors are the maintargets, receptors exhibit specificity, saturation and competition |
| 2. down-regualtion | decrease in receptors and receptor function: DEPHOSPHORYLATION |
| 3. up-regulation | increase in receptors: PHOSPHORYLATION |
| 4. signal termination | to turn off signaling thru brkdwn of chem msgr or endoytose: bring in and turn off; can PHOSPHORYLATE to increase or DEPHOSPHORYLATE to decrease receptors |
Created by:
Lkellyfly
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