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51 Cards in this Set
- Front
- Back
What are the two types of physiological signals? |
Chemical and electrical |
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Electrical signals |
Changes in a cell's membrane potential |
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Chemical signals |
Molecules secreted by cells into the extracellular fluid. Can act as ligands that bind to proteins to create a response. |
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Target cells |
RESPOND TO ELECTRICAL OR CHEMICAL SIGNALS |
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4 methods of cell-to-cell communication/ Local communication |
-gap junctions
-contact dependent signals -Chemicals diffused through the ECF to act on the target cell(s) -long distance communication (combination of chemical and electrical signals) |
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Gap junctions |
-Direct cytoplasmic transfer of electrical and chemical signals between adjacent cells. -simplest form of communication. -protein channels that create cytoplasmic bridges. -ions and small molecules can go through these. -This is the only way electrical signals can be passed directly through. |
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Contact-Dependent Signals |
-Surface molecules in the immune system and during growth and development. -Cell adhesion molecules (CAMs) are used as receptors and can transport signals in both directions by their connections with the cytoskeleton and intracellular enzymes. |
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Paracrine signal |
Chemical that acts on cells in the immediate vicinity of the cell that secreted it. ie. Histamine |
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autocrine signals |
chemical signal that acts on the cell that secreted it. |
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What system(s) is long distance communication typically through? |
Nervous and endocrine |
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Hormones |
-Endocrine chemical signals released into the blood and are taken all over the body. Only cells with receptors for that hormone can be targets. -The most common ones in the body are peptides. |
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neurocrine molecules |
chemicals secreted by neurons. |
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neurotransmitter |
neurocrine molecule that diffuses across a narrow extracellular space to the target. Rapid onset effect. |
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neuromodulator |
neurocrine molecule that acts slower, like a paracrine or autocrine signal. |
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neurohormone |
neurocrine molecule diffuses into the blood for body distribution. Is part of both the nervous system and the endocrine in a way. |
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Receptor proteins |
A cell can bind to a particular chemical signal only if it has the right receptor protein to bind to the signal. |
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Signal pathway for receptor proteins: |
1) Ligand (1st messenger) is the signal molecule and will bind to the protein receptor 2) Ligand-receptor binding activated receptor 3) Receptor activates one or more intracellular signal molecules (2nd messengers) 4) Signal molecule creates a response by modifying existing proteins or synthesizes new proteins |
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Lipophilic signal molecules |
(non polar) Enter through simple diffusion and bind to cystolic receptors or nuclear receptors. Typically directs cell to make new mRNA, and new proteins. Can sometimes repress gene activity. ie. hormones |
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Lipophobic signal molecules |
(Polar) Unable to enter through cell membrane, so they stay in the extracellular fluid and bind to the receptor proteins on the cell membrane. Rapid response time |
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What are the 4 categories of membrane receptors? |
Receptor channel G-Protein Coupled Receptor (GPCR) Receptor-enzyme Integrin receptor |
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Signal transduction |
transmission of info from one side of the cell membrane to the other side. Signal from extracellular to intracellular will alter intercellular molecules. Transducer changes a signal from one form to another |
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What can 2nd messenger molecules do? |
- Alter gating on ion channels - Increase intracellular calcium (changes protein function creating a new response) - Changes enzyme activity (especially protein kinases and protein phosphatases, either phosphorylating or de-phosphorylating proteins, changing shape and creating a response) |
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What is responsible for a cell's response to a signal? |
Proteins modified by calcium binding and phosphorylation. |
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Protein Kinases |
Phosphorylate proteins |
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Amplification |
signal is made larger. One signal molecule turns into multiple second molecules by an amplification enzyme. |
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Receptor Channels |
Simplest membrane receptor Most rapid effect. An increase or decrease in the permeability of ions will change the membrane potential almost right away. Found in nerves and muscles ie.Acetylcholine-gated monovalent cation channel of skeletal muscle. ACh bings to the ACh receptors and opens the channel. Then Na and K flow through, K leaving the cell and Na coming in (along the electrochemical gradient). This depolarizes the cell leading to muscle contraction. |
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G-Protein Coupled Receptors (GPCR) (1/2) |
G Protein: 3 part membrane transducer connected to cytoplasmic tail. Hormones, growth factors, olfactory molecules, visual pigments, and neurotransmitters can attach to G proteins. Phosphorylating GDP to GTP activated the protein This receptor can open or close ion channels or alter enzyme activity on the cytoplasmic side of the membrane. Linked to amplifier enzymes |
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G-Protein Coupled Receptors (GPCR) (2/2) |
Many lipophobic hormones use GPRC-cAMP pathways. When this pathway is activated phospholipase C (PLC) converts membrane phospholipids into 2 lipid derived 2nd messengers: (1)Diaglycerol: DAG. non polar. Remains in lipid portion of mem. Ca activated enzyme associated with cytoplasmic side, used for a cnts 2nd messenger cascade.(2)Inositol triphosphate: IP3. H2O soluble messenger leaves membrane and enters the cytoplasm. Binds to Ca channel on endoplasmic reticulum, letting Ca diffuse out of ER |
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Receptor-Enzyme |
2 regions: -Receptor on extracellular side. Catalytic receptors -enzyme on intracellular side Sometimes they are part of the same protein and sometimes different proteins.Activated from a ligand binding to receptor enzymes are either protein kinases or guanylyl cyclase (converts GTP to cyclic GMP [cGMP]) ie.Tyrosine kinase receptor |
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Tyrosine Kinase receptor |
Receptor-Enzyme process 1) Signal molecule (ligand) binds to the surface receptor 2) Transfers a signal to the Tyrosine Kinase on the cytoplasmic side of the membrane 3) A tyrosine molecule then binds to Tyrosine Kinase and it transfers a phosphate from ATP to the tyrosine molecule. -This is also how insulin works |
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Integrin receptors |
Membrane spanning proteins Attach to the inside of the cell via anchor proteins Activate intracellular enzymes or alter organization of cytoskeleton. Catalytic receptors |
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What are the 4 groups of modified proteins due to a cell response? |
- Motor Proteins - Enzyme activity - gene regulation and protein synthesis - Membrane transport and receptor proteins |
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GPCR-adenyl Cyclase Signal Transduction and Amplification |
1) Signal molecule binds to GPCR, activating the G-Protein. 2) G-Protein turns on adenylyl cyclase (the amplifier enzyme to create a cascade of proteins) 3) Adenylyl cyclase converts ATP into cyclic AMP (2nd messenger) 4) cAMP activates Protein Kinase A 5) Protein Kinase A phosphorylates other proteins, leading to a cell response. |
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Signal transduction using ion channels |
1a) some channels may be directly linked to G-Protein Coupled Receptors which create intracellular signal molecules to signal the opening of ion channels. b) Receptor channels open/close in response to a signal molecule binding 2) Change in permeability of K+, Na+, and Cl- 3) Creates and electrical signal 4) Voltage sensitive protein senses the electrical signal 5) Cell response |
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Calcium as a Intracellular signal |
A) 1)Ca2+ enters the cell via a channel (mechanical, voltage, or chemical gates) 2) Ca levels increase in the cytosol 3) Ca binds to proteins (either Calmodulin or other) 4) Calmodulin alters protein activity. Other binding molecules start exocytosis and movement in the cell B) 1)Electrical signal causes the release of Ca from intracellular stores 2-4) Same as above |
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Calmodulin |
alters enzyme or transporter activity, or gating ions |
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What do target responses rely on? |
Target response rely on TARGET TISSUES. (Whether they have receptors or not and the reaction of the receptor) ie. Epinephrine can bind to different receptors ultimately dilating or contracting blood vessels. (alpha receptors =constricts, Beta receptors= dilate) |
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Down-regulation |
decrease in the number of receptor on a cell. Can be done via: -Physical removal via endocytosis -Desensitization: easily reversible. Achieved by binding a chemical modulator to a receptor protein. ie. competitive inhibitor |
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up regulation |
target cell inserts more receptors into membrane. This is used during development and allows cells to be very responsive to growth factors and other signals. |
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How can cells terminate signal pathways? |
-ligand can be broken down via enzymes -removed from the ECF into neighboring cells (neurotransmitters) -Endocytosis of receptor (ligand and complex) |
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Reflex control pathway |
Complex information must be transmitted through the body via chemical signals, electrical signals, or both. ie the process of the release of T4 and T3. |
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Cannon's 4 postulates |
1. The nervous system has a role in preserving the parameters of the internal environment. 2. Some systems of the bode are under tonic control. 3. Some systems of the body are under antagonistic control. (ie. glucagon and insulin) 4.One chemical signal can have different effects in different tissues. |
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What controls long distance pathways? |
Nervous and endocrine systems |
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Response loops |
Stimulus--> Sensor/Receptor --> Input (afferent) signal --> Integrating Center (compares input to set point) --> Output (efferent) signal --> target --> response |
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Central receptors |
In the brain and closely linked to the brain |
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Peripheral receptors |
elsewhere in body that is away from brain. ie. Skin receptors and internal receptors |
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Threshold |
All sensors have this minimum stimulus needed to start a reflex response. |
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Why do control systems vary? |
Specificity, nature of the signal (fast/slow acting), duration of action, and the coding for stimulus intensity (frequency or amount released). |
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Simple endocrine reflex |
Only has one integrating center, receptor, and hormone |
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Complex neuro-endocrine reflex |
Multiple receptors, integrating centers, and hormones |
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What do disease and drugs do to pathways? |
Modulate signal pathways |