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Neuronal structure and communication. Class 3. NEURON STRUCTURE & FUNCTION. The Neuron’s Structure. The Cell Membrane: Barrier and Gatekeeper. Concentration of dissolved substances in the extracellular and intracellular fluid is different. What do Membrane Proteins Do?. - PowerPoint PPT Presentation
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The Cell Membrane: Barrier and Gatekeeper
• Concentration of dissolved substances in the extracellular and intracellular fluid is different
How the Movement of Ions Creates Electrical Charges
– Cations - Positively charged ions; Na+, K+– Anions - Negatively charged ions; Cl-, protein anions
(A-)– Ions move from areas of high charge to areas of low
charge and substances move from areas of high concentration to low concentration.
– Cell-Membrane Structure is impermeable to salty solutions
– Protein molecules in the membrane allow certain ions to pass
Resting Potential
• Neurons at rest– Unequal distribution of ions – Intracellular fluid has a negative charge
relative to the extracellular fluid– Difference in charge is about -70mV (Resting
Potential)
The Action Potential
• Action Potential– Brief but extremely large flip in the polarity of
an axon’s membrane– Voltage across the membrane reverses
• The inside becomes positive relative to the outside
– Occurs when depolarization of the membrane occurs
– Membrane must reach Threshold Potential at about -50mV
Classifying Neurotransmitters
• Three classes of neurotransmitters– Small-Molecule Transmitters– Peptide Transmitters– Transmitter Gases
Small-Molecule Transmitters
• Small organic molecules
• Synthesized and packaged in axon terminals
• Derived from the food we eat
• Act quickly
Peptide Transmitters
• Neuropeptides
– Multifunctional chains of amino acids made by the cell’s DNA
– Process is longer to make and transport than small molecules
• Peptide transmitters:
– Serve as hormones
– Active in response to stress
– Encourage mother-child bonding
– Facilitate learning
– Regulate eating and drinking
– Respond to pleasure and pain
Transmitter Gases
• Synthesized as needed by the cell• Can be produced in many regions of the cell• After production diffuse away from the cell right
through the cell membrane (don’t need channels)– Nitric Oxide (NO) – Carbon Monoxide (CO)
Receptors for Direct and Indirect Effects
• Ionotropic– Direct effects– Allow the movement of
ions across the membrane
– Rapid– Do not last long
• Metabotropic– Indirect effects– Slower– Last longer– G-Protein
• Three subunits
– Second messenger• Carries the message to
other structures in the cell
Activating Systems
• Activating Systems– Cell bodies located in the brainstem, axons
distributed throughout the brain– Neurotransmitter pathways. The NTs are
manufactured in the cell bodies and released throughout the system.