BIOL 1361 1nd Edition Lecture 24Outline of Last Lecture I. Neuron StructureII. Fig 37.2III. Real NeuronsIV. Resting PotentialV. Figure 37.6VI. Description of Ion MovementVII. Electrochemical EquilibriumVIII. Action PotentialIX. GraphOutline of Current LectureI. SynapseII. At Chemical SynapseIII. Cell Communications and HormonesIV. HormonesV. Signaling ModesVI. PheromonesVII. Protein SecretionVIII. Hormonal Regulation of Target CellsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.IX. Water Soluble (hydrophilic) HormonesX. Signaling Pathway XI. Figure 5.25XII. Signal TransductionCurrent LectureI. Synapsea. Step 1: Axon goes down the axonb. Step 2: The voltage gated Ca channel opens when the action potential arrives. It enters the cell and attaches to the vesicles to make them fuse with the plasma membrane releasing the neurotransmittersc. Step 3: The ligand gated Na channels open when the neurotransmitter attaches to themd. Step 4: The Na/K pumpII. At Chemical Synapsea. The electrical signal crosses the synaptic clef =gap between neuronsb. How? i. Action Potential reaches end of neuronii. Voltage changes in the neuron membraneiii. Voltage-gated Ca2+ channels openiv. Ca2+ binds to vesicles containing neurotransmitterv. Vesicles fuse with neuron membranevi. Neurotransmitter is released by exocytosis into the synaptic clefvii. Neurotransmitter binds to receptors on next neuronviii. Receptors are ligand-gated Na channels = Na channels that open when the right molecule (ligand) attaches1. Ligand – a small molecule that attaches to a receptor2. Ligand is a general termix. Neurotransmitter detaches from receptors and is degraded by enzymes tostop signalIII. Why Do Cells Communicate?a. Unicellular Organismsi. Foodii. Safetyiii. Matesb. Multicellular Organismsi. Coordinate ActivitiesIV. Hormonesa. Def: Chemical signals produced by endocrine cellsi. Endocrine cells secrete hormones into the interstitial fluid or into capillariesb. Secreted into body fluid to act on target cells – any cell with a receptori. Receptor is always a protein that binds a specific hormoneV. Signaling Modesa. Two Basic Modesi. Local Signaling1. Gap Junctions – allow ions to move between cells carrying an electrical signal2. Paracrine – chemical secreted from one cell signals a neighboring cellii. Long Distance Signaling1. Hormone is secreted2. Enters bloodstream3. Travels to target cell in another part of the body4. Example: a. Pancreas secretes insulinb. Insulin travels in blood to signal muscle and fat cellsVI. Pheromonesa. Def: molecules secreted by cells in one individual to act on cells in another individual of the same speciesVII. Protein Secretiona. Video: ***Know this for the test!VIII. Hormonal Regulation of Target Cellsa. Cells have 2 ways to detect and respond to hormones:i. Receptors at the surface of the cellii. Receptors inside the cellb. Detection method depends on type of hormone moleculei. Hydrophilic molecule – detected at cell surfaceii. Hydrophobic molecule – detected afer enters cellIX. Water Soluble (hydrophilic) Hormonesa. Structurei. Peptide or amineX. Signaling Pathwaya. Plasma Membrane Receptori. Receptor Protein = integral protein 1. This means its embedded in the membraneii. Hormone attaches to extracellular side receptoriii. Receptor changes shapeXI. Figure 5.25a. First Messenger (hormone) interacts with the receptor and sparks chain reactionb. The G protein coupled receptor can bind GTP c. The G protein can active an enzyme, Adenylyl Cyclased. ATP turns into cAMP (second messenger) then activates other enzymes inside the cell such as protein kinase then lead to cellular response.XII. Signal Transductiona. Intracellular 2nd messengers and cytosolic enzymes amplify the signalb. Second Messengersi. Intracellular moleculesii. Activate enzymes that initiate cellular responseiii. Examples: 1. Cyclic AMP2. Ca2+c. Enzymesi. Kinases1. Enzymes that add PO4 groups2. Activate other intracellular enzymes in a cascade of
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