Intro to Neuroscience: Exam 2 (Neurochemistry) – Flashcards

Otto Loewi resolves debate: Question: Do neurons release a chemical to communicate with other cells, or is the communication based on electrical signals? Experiment: Stimulate the vagus nerve to slow the heart. Collect fluid from around the slowed heart and apply the fluid to a second heart. Result: The second heart slowed Conclusion: The vagus nerve uses a chemical neurotransmitter, not a direct electrical connection, to communicate to cells of the heart and cause it to slow down.

1. Presynaptic neuron/membrane 2. Synaptic vesicle -Neurotransmitter 3.Synaptic cleft 4. Postsynaptic neuron/membrane -Receptors

1. Depolarization of presynaptic membrane 2. Fusing of vesicles 3. Release of neurotransmitters into synaptic cleft 4. Binding of neurotransmitters to receptors on postsynaptic membrane 5. Generate EPSP or IPSP 6. Removal of neurotransmitter from synaptic cleft

Ionotropic (aka ligand-gated ion channels) -Direct Gating - Faster response Metabotropic (GPCR) -Indirect gating - Slower response - Can also result in gene expressiom changes

Why is it necessary? - Prevents continuous signal transfer Two Major Mechanisms: - Reuptake - Deactivation by enzymes

Distance between pre and postsynaptic membranes: Chemical: 20 nm-40 nm Electrical: 4nm Cytoplasmic continuity between pre-and postsynaptic cells: Chemical: No Electrical: Yes Ultrastructural components: Chemical: Presynaptic vesicles and active zones, postsynaptic receptors. Electrical: Gap-junction channels Agent of transmission: Chemical: Chemical transmitter Electrical: Ion current Synaptic delay: Chemical: Significant: at least 0.3 ms, usually 1-5 ms or longer Electrical: Virtually absent Direction of Transmission: Chemical: Undirectional Electrical: Usually bidirectional

Amino Acids: Ex: GABA and glutamate -Two ubiquitous neurotransmitters in CNS Amines: Family/Subfamily: Quaternary amines and Monoamines Ex: Serotonin (Feeding, sociality, mood,Sleep/wake) and Melatonin (Sleep/wake cycles, feeding, inhibits reproduction) Neuropeptides: Family/Subfamily: Opioid peptides (e.g. Endorphins(Pain regulation/sensation, Attachment, Reward, Love) Other neuropeptides: Oxytocin( e.g. Fluid regulation, social behavior, attachment etc.) Gases: Ex: Nitric oxide (e.g. Can be released as retrograde transmitter or cotransmitter)