NEURAL TRANSMISSION Neurons Electrical and Chemical Transmission

Neurons

Neurons

Glial Cells Astrocytes –Contact blood vessels and neurons –transport chemicals from blood to neurons Oligodendrocytes –Myelinate CNS axons Schwann cells –Myelinate PNS axons –Guide regeneration after damage Radial glia –Guide neural migration during development

CELL MEMBRANES Membrane Structure –Semipermeable lipid bilayer –Proteins Ion channels Transport pumps Receptors

MEMBRANE POTENTIAL

Electrochemical Gradient –Electrostatic Forces Electrical gradient Opposite charges attract, Same charges repel –Diffusion Forces Concentration gradient

RESTING MEMBRANE POTENTIAL Diffusion Forces –Na + and Cl - in –K + out Electrostatic Forces –Na + and K + in –Cl - out +

MEMBRANE POTENTIAL Na+/K+ Pump –Compensatory Mechanism –Active when intracellular Na+ high –Neutral or inactive when intracellular Na+ low

ACTION POTENTIAL

CONDUCTION OF A.P.

SYNAPTIC TRANSMISSION NEUROCHEMICAL SYNAPSES

SYNAPTIC COMMUNICATION POSTSYNAPTIC POTENTIALS –Excitatory PSP –Inhibitory PSP Electrical Synapses –Gap junctions Neurochemical Synapses

Structures of Neurochemical Synapses Presynaptic Membrane Postsynaptic Membrane Synaptic Vesicles Synaptic Cleft Receptor Sites

Steps In Neurochemical Transmission SynthesisStorage Neurotransmitter Release Receptor Activation Neurotransmitter Deactivation –Enzymatic Deactivation (Metabolism) –Reuptake

Steps in Neurochemical Transmission

SYNTHESIS

Receptor Activation Ionotropic Receptors –ligand gated ion channels Metabotropic Receptors –G proteins –Second Messengers

Neurotransmitter Inactivation  Enzymatic Degradation (Metabolism)  Acetylcholine is inactivated by an enzyme, Acetylcholinesterase (AChE).  The monoamines are inactivated by the enzyme, Monoamine Oxidase (MAO)  Catecholamines (DA, NE, E) are also inactivated by and Catechol-O- Methyltransferase (COMT).  Reuptake  The monoamines are also inactivated through reuptake.

MAJOR NEUROTRANSMITTERS Acetylcholine Monoamines Monoamines –Catecholamines EpinephrineNorepinephrineDopamine –Indoleamines Serotonin Amino Acid Transmitters Amino Acid Transmitters –Glutamate, Aspartate –GABA, Glycine Neuropeptides –Enkephalins –Endorphins

Cholinergic Pathways

Dopaminergic Pathways

Noradrenergic Pathways

Serotonergic Pathways

Neurochemical Pathways Dopamine –Nigrostriatal Pathways (Substantia Nigra  Basal Ganglia) –Mesolimbic, Mesocortical Patways (VTA  NAc and pfCTX) –Most widely studied neurobiology theory of drug dependence relates to dopamine

Neurochemical Pathways Acetylcholine –Pontine nuclei involved in components of REM sleep –Basal Forebrain Reduced quantities found in Alzheimer’s patients Norepinephrine –Locus Coeruleus  Forebrain Stimulant drugs may induce wakefulness through these pathways

Neurochemical Pathways Serotonin (5-HT) –Raphe Nuclei –Research on weight control, aggressiveness, and depression are centered on 5-HT GABA –Widespread in CNS – Related to seizures Endorphins –Spinal cord and midbrain –Involved in body’s natural mechanisms for pain relief