Neuronal structure and communication

1. Neuronal structure and communication Class 3

2. NEURON STRUCTURE & FUNCTION

3. The Neuron’s Structure

4. The Cell Membrane: Barrier and Gatekeeper • Concentration of dissolved substances in the extracellular and intracellular fluid is different

5. What do Membrane Proteins Do?

6. 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

7. 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)

8. Resting Potential

9. 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

10. Triggering an Action Potential

11. Sending a Message Along an Axon

13. NEURONAL COMMUNICATION: NEUROTRANSMISSION

14. The Structure of Synapses

15. Steps in Neurotransmission

16. Classifying Neurotransmitters • Three classes of neurotransmitters • Small-Molecule Transmitters • Peptide Transmitters • Transmitter Gases

17. Small-Molecule Transmitters • Small organic molecules • Synthesized and packaged in axon terminals • Derived from the food we eat • Act quickly

18. 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

19. 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)

20. 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 Receptors for Direct and Indirect Effects

23. 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.

24. Activating Systems: Noradrenergic Pathway

25. Activating Systems: Serotonergic Pathway

26. Activating Systems: Dopaminergic Pathway

27. Activating Systems: Cholinergic Pathway

28. CLINICAL VIGNETTES