W6 Lecture 2 - Neurobiology PDF

# 3/9 W6 Lecture 2 ## Neurons - **Soma:** cell body. Contains the nucleus. - **Axon:** fiber extending from the soma to connect to terminals. - **Dendrites:** small fibers extending from the soma. - **Myelin:** protective layer around the axon. - Neurons pick up signals from their dendrites and t...

# 3/9 W6 Lecture 2 ## Neurons - **Soma:** cell body. Contains the nucleus. - **Axon:** fiber extending from the soma to connect to terminals. - **Dendrites:** small fibers extending from the soma. - **Myelin:** protective layer around the axon. - Neurons pick up signals from their dendrites and then send those signals to the terminals - Signals contact on/off systems. - Neurons are covered in a lipid (fat) membrane. - Most of the time it's in a resting state, aka polarized or "off". - When sending a signal it activates **action potential**. This opens ion channels in the lipid and allows ions to enter and exit. This makes the neuron "flip" and it is now depolarized. Then it flips off again. - Neurons are digital. - They convey's only one bit of information. - Action potentials are channels of depolarization that form almost a wave effect and runs the entire neuron. This process starts in the dendrites. ## Myelin - Prevents depolarization except at gaps. - Covers the axon of a neuron. - Gaps in the myelin allow for action potential to skip the myelin, going between the gaps. - Myelin does this way speeds up action potential. - Short axons don't need myelin because AP travels fast enough. ## Neural functions: more sophistication of brain function due to: - High speed of info. - Large number of neurons. - Complexity of connections between neurons (circuitry). ## Neurotransmission - Neurons interact through a small gap but then a chemical across the small gap that sticks to the other neuron. The gap is called the **synapse**. - Neurotransmitters as the chemicals are spilled into the synapse from the terminal. - This process is from action potential sending signals to another neuron. - After neurotransmission, the neurotransmitters have to get removed from the synapse ASAP. They are cleaned up either by enzymes, or are sucked back up by neurons. - Drugs affect the functioning of neurons. ## Drugs (recreational): - **Opiates:** mimic receptors of opioid neurotransmitters. - **Stimulants (cocaine, ecstasy, etc):** promote release of chemicals. - **Nicotine:** stimulates acetylcholine receptors. - **Caffeine:** blocks adenosine receptors. ## Therapeutic drugs: - **Valium:** enhances GABA. - **Anti-schitzo drugs:** block dopamine receptors. - **Antidepressants:** improve serotonin receptors.