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Neural Transmission
| Term | Definition |
|---|---|
| Plasticity | Neurons can change their structure and function |
| Longevity | Neurons are with us for life, although they do not regenerate (once they die, they're gone) |
| Convergence | One neuron receives signals from many neurons |
| Divergence | One neuron can send signals to many targets |
| Dendrites | Receive signals from other neurons |
| Soma | Connected to the dendrites, is the cell body which contains the nucleus and organelles |
| Axon hillock | The bottom of the soma, it is the location where all inputs are summed up and determines whether or not the cell sends signals |
| Axon | Longest extended branch of the neuron, carries info from the axon hillock to the axon terminals |
| Myelin sheath | Located along the axon, but it does not coat the entire axon |
| Nodes of Ranvier | The exposed parts of the axon |
| Axon terminals | The place where information conveyed to other neurons or cells, can sometimes be through electrical means but is normally chemical means |
| Synapse | The space between the axon terminals and dendrites, where the signal gets passed |
| Interneurons | The most common neuron type in mammals, creates a circuit, the cell bodies are located in the brain or spinal cord, and they target other neurons in the CNS |
| Interneuron subtypes | Pyramidal (in the cortex), Purkinje (in the cerebellum), and Stellate (in the thalamus) |
| Typical interneuron neurotransmitters | GABA (inhibitory), Glutamate (excitatory) |
| Motor neuron | Some of the longest neurons in the body, the cell bodies are in the brain or spinal cord, and target muscles |
| Motor neuron subtypes | Lower (connect the spinal cord to muscles) and upper (connect the brain to the spinal cord) |
| Typical motor neuron neurontransmitters | Acetylcholine (used by lower neurons), Glutamate (used by upper neurons) |
| Sensory neurons | The cell body location depends on the sense (e.g., cell bodies for touch neurons located in dorsal root of the spinal cord), and targets the CNS where it enters via the cranial and spinal nerves |
| Sensory neuron subtypes | Too many to mention |
| Typical sensory neuron neurotransmitters | Glutamate |
| Glial cells | The supporting cells of the nervous system that have many diverse functions and that can be replaces throughout one's lifetime |
| Oligodendrocytes | Myelinates axons in the CNS |
| Schwann cells | Serve the same function as oligodendrocytes (myelinating axons), but in the PNS |
| Microglia | Part of the immune system response in the brain, scavenges for debris in the nervous system |
| Astrocytes | Provide structural support to the nervous system, and transmits substances between the neurons and the blood vessels |
| Ependymal cells | Create CSF, line the ventricles, and make up the choroid plexus |
| Resting potential | The electrical charge across the cell membrane in the absence of stimulation. The inside of the cell is negatively charged at this stage, and the outside is positively charged |
| Graded potential | Small voltage fluctuations across the cell membrane which can hyperpolarize or depolarize the cell membrane. If the threshold is met by enough depolarizing graded potentials, an action potential will occur |
| Action potential | A large, brief reversal in polarity of the cell membrane; travels along the length of the axon caused by the combined influx of Na+ and K+ that consists of the summed voltages changes due to the ions |
| Ion distribution at rest | Sodium (+), chloride (-), and calcium (+) are concentrated outside the cell membrane while potassium (+) and other anions (-) are inside the cell membrane |
| Factors contribute to neuron's resting potential (1) | Large anions are stuck inside the cell keeping the intracellular side negative |
| Factors contribute to neuron's resting potential (2) | Potassium (+) and chloride (-) can move freely across the gradient, but sodium (+) cannot and the potassium concentration gradient keeps enough potassium ions on the extracellular side so that the intracellular side stays negative |
| Factors contribute to neuron's resting potential (3) | The sodium potassium pump moves 3 sodium ions (+) out of the cell for every 2 potassium ions (+) it brings into the cell, keeping the intracellular side negative |
| Depolarization | Decrease in the electrical charge across the membrane. Excitatory post-synaptic potentials do this. |
| Hyperpolarization | Increase in the electrical charge across a membrane. Inhibitory post-synaptic potentials do this. |
| All or none law | Once an action potential is triggered, it continues down the length of the axon at the same strength, and if the threshold is not met, there is no action potential |
| Saltatory conduction | The property myelinated axons use to propagate an action potential at each successive Node of Ranvier which makes signals travel faster because they only need to open voltage-sensitive channels at the nodes and not the whole length of the axon |
| Spatial summation | EPSPs produced at the same time, but on separate parts of the cell membrane do not influence each other, but EPSPs produced at the same time and close together add to form a larger EPSP (and the same applies with IPSPs in both instances) |
| Neurotransmitter | The chemicals released by our neurons into the synapse that have excitatory or inhibitory effects on their target |
| Chemical synapse | The junction between two neurons or a neuron and target tissue where chemicals are released |
| Microtuble | Transport structure that carries substances to the axon terminal |
| Mitochondrion | Organelle that provides the cell with energy |
| Synaptic vesicle | Round granule that contains neurotransmitters |
| Storage granule | Large compartment that holds synaptic vesicles |
| Presynaptic membrane | Encloses molecules that transmit chemical messages |
| Synaptic cleft | Small space separating presynaptic terminal and postsynaptic dendritic spine |
| Postsynaptic receptor | Site to which a neurotransmitter molecule binds |
| Postsynaptic membrane | Contains receptor molecules that receive chemical messages |
| Neural transmission steps | Synthesis, release, receptor activation, inactivation |
| Small molecule synthesis | Synthesized within the axon terminal from precursor molecules (often derived from foods) and enzymes readily available in the terminal |
| Small molecule neurotransmitters | Acetylcholine, dopamine, norepinephrine, serotonin |
| Neuropeptide synthesis | Larger neurotransmitters are derived in the soma from DNA instructions and then transported to the axon terminal |
| Neuropeptide neurotransmitters | Neuropeptide Y, endorphins, oxytocin |
| Release (Step 1) | When an action potential reaches the voltage-sensitive terminal, it opens calcium channels |
| Release (Step 2) | Incoming calcium ions bind to calmodulin, forming a complex |
| Release (Step 3) | The complex binds to vesicles, releasing some from filaments and inducing others to bind to the presynaptic membrane and to empty their contents by exocytosis |
| Receptor Action | Postsynaptic receptors are the primary binding sites for neurotransmitters, specifically autoreceptors, neurotransmitters only bind to their specific receptor (sub)types, and sometimes astrocytes may also have receptor binding sites |
| Types of inactivation | Diffusion, reuptake, degradation by enzymes, and glial cell absorption |
| Diffusion | Floating off to be disposed of by microglia eventually |
| Reuptake | Channels in the presynaptic neuron open to allow neurotransmitters to enter the cell to be repackaged in vesicles and to be rereleased eventually |
| Degradation by enzymes | Enzymes denature the neurotransmitters in the synaptic cleft |
| Adrenaline | Fight or flight |
| Noradrenaline | Concentration |
| Dopamine | Pleasure |
| Serotonin | Mood |
| GABA | Calming |
| Acetylcholine | Learning |
| Glutamate | Memory |
| Endorphins | Euphoria |
| Neurotransmitter qualifications | Chemical must be synthesized or present, chemical must produce a response in the target cell, the same receptor action must be obtained when chemical is experimentally applied, and there must be a mechanism for removal after the chemical's work is done |
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