What happens when the action potential reaches the end of its journey when it makes its way to the axon terminal and is ready to be converted into a chemical signal? Well, the axon terminal will have formed a junction with another cell. This junction is called a synapse. It's that connection between neurons that allows them to pass signals along. Signals are almost always going to be traveling from the presynaptic cell to the postsynaptic cell. That is the cell that had the action potential moving through it to the cell on the other side of the synapse. Now, I say almost always because there are some very notable exceptions including the endocannabinoid system which throws these rules out the window, also the gas nitric oxide which can act as a neurotransmitter, basically diffuses in any direction it pleases. It is not bound by these restrictions. However, we're not going to be bothering really with those exceptions, so you can basically safely assume that synaptic transmission will, you know, basically always go from the presynaptic cell to the postsynaptic cell. It's not until you get into like more advanced neuroscience stuff where you have to actually worry about those exceptions. So, signals, as we've said, can be chemical neurotransmitters. Right? The neuron will release neurotransmitters into the synapse. However, not all synapses are chemical synapses, some are electrical and we've actually seen these in other places. These are gap junctions, right? Those protein channels that connect cells together actually will allow the action potential to pass directly from one cell into another cell. So those are electrical synapses. However, we're going to be looking at chemical synapses and these chemical synapses will contain voltage gated calcium channels. These voltage gated calcium channels are critical to neurotransmitter release. So how does this actually all go down? Well, of course, you're going to begin with the action potential finally making its way to the axon terminal of the presynaptic cell. So, here, we have our sodium and potassium channels that allow the action potential to move its way along the axon until it finally reaches the terminal, here, it's going to cause depolarization and that depolarization opens these voltage gated calcium channels. These voltage gated calcium channels will allow calcium ions into the cell. These calcium ions act as a signal to vesicles. Now, in the axon terminal, you will have lots of these synaptic vesicles and they are basically going to just be hanging around storing neurotransmitters. NT. That's what I mean there. Neurotransmitters. When they get the calcium signal, they actually bind to the membrane of the axon terminal and fuse with it and in this process, they release their neurotransmitters into what's called the synaptic cleft. This space between the axon terminal of the presynaptic cell and the membrane of the postsynaptic cell. So, these neurotransmitters will diffuse across that gap, that synaptic cleft and bind to receptors on the postsynaptic membrane. And in binding these receptors, we'll actually, see the signal be transduced to the other cell. Now there are going to basically be 2 kinds of receptors we'll see on that postsynaptic membrane, they're ionotropic receptors and metabotropic receptors. And you don't really need to worry about knowing these terms, I'm throwing them out because it just makes it easier to describe 2 different categories of postsynaptic membrane receptors. So, these ionotropic receptors basically are just membrane receptors that act by opening an ion channel. Pretty simple. So, by that, by virtue of that, essentially, they are going to be ligand gated ion channels which we talked about before. They open in response to ligand binding like neurotransmitters. Neurotransmitters are a ligand. So, here we have a neurotransmitter called acetylcholine. It will bind to this ionotropic receptor which will open it and allow ions to move in and out of the cell. Now, on the flip side, you have metabotropic receptors. These act through second messengers and they're often going to be g protein coupled receptors. So the neurotransmitter will bind and then a bunch of stuff's going to happen in the cell and they can have a wide variety of effects. For example, they can lead to, you know, increasing numbers of receptors on the membrane or they can actually also lead to ions moving in and out of the cell. They're much more varied whereas the ionotropic receptors are very cut and dry. Ligand binds, ions either come in or out of the cell. With that, let's go ahead and flip the page.
Table of contents
- 1. Introduction to Biology2h 40m
- 2. Chemistry3h 40m
- 3. Water1h 26m
- 4. Biomolecules2h 23m
- 5. Cell Components2h 26m
- 6. The Membrane2h 31m
- 7. Energy and Metabolism2h 0m
- 8. Respiration2h 40m
- 9. Photosynthesis2h 49m
- 10. Cell Signaling59m
- 11. Cell Division2h 47m
- 12. Meiosis2h 0m
- 13. Mendelian Genetics4h 41m
- Introduction to Mendel's Experiments7m
- Genotype vs. Phenotype17m
- Punnett Squares13m
- Mendel's Experiments26m
- Mendel's Laws18m
- Monohybrid Crosses16m
- Test Crosses14m
- Dihybrid Crosses20m
- Punnett Square Probability26m
- Incomplete Dominance vs. Codominance20m
- Epistasis7m
- Non-Mendelian Genetics12m
- Pedigrees6m
- Autosomal Inheritance21m
- Sex-Linked Inheritance43m
- X-Inactivation9m
- 14. DNA Synthesis2h 27m
- 15. Gene Expression3h 20m
- 16. Regulation of Expression3h 31m
- Introduction to Regulation of Gene Expression13m
- Prokaryotic Gene Regulation via Operons27m
- The Lac Operon21m
- Glucose's Impact on Lac Operon25m
- The Trp Operon20m
- Review of the Lac Operon & Trp Operon11m
- Introduction to Eukaryotic Gene Regulation9m
- Eukaryotic Chromatin Modifications16m
- Eukaryotic Transcriptional Control22m
- Eukaryotic Post-Transcriptional Regulation28m
- Eukaryotic Post-Translational Regulation13m
- 17. Viruses37m
- 18. Biotechnology2h 58m
- 19. Genomics17m
- 20. Development1h 5m
- 21. Evolution3h 1m
- 22. Evolution of Populations3h 52m
- 23. Speciation1h 37m
- 24. History of Life on Earth2h 6m
- 25. Phylogeny2h 31m
- 26. Prokaryotes4h 59m
- 27. Protists1h 12m
- 28. Plants1h 22m
- 29. Fungi36m
- 30. Overview of Animals34m
- 31. Invertebrates1h 2m
- 32. Vertebrates50m
- 33. Plant Anatomy1h 3m
- 34. Vascular Plant Transport2m
- 35. Soil37m
- 36. Plant Reproduction47m
- 37. Plant Sensation and Response1h 9m
- 38. Animal Form and Function1h 19m
- 39. Digestive System10m
- 40. Circulatory System1h 57m
- 41. Immune System1h 12m
- 42. Osmoregulation and Excretion50m
- 43. Endocrine System4m
- 44. Animal Reproduction2m
- 45. Nervous System55m
- 46. Sensory Systems46m
- 47. Muscle Systems23m
- 48. Ecology3h 11m
- Introduction to Ecology20m
- Biogeography14m
- Earth's Climate Patterns50m
- Introduction to Terrestrial Biomes10m
- Terrestrial Biomes: Near Equator13m
- Terrestrial Biomes: Temperate Regions10m
- Terrestrial Biomes: Northern Regions15m
- Introduction to Aquatic Biomes27m
- Freshwater Aquatic Biomes14m
- Marine Aquatic Biomes13m
- 49. Animal Behavior28m
- 50. Population Ecology3h 41m
- Introduction to Population Ecology28m
- Population Sampling Methods23m
- Life History12m
- Population Demography17m
- Factors Limiting Population Growth14m
- Introduction to Population Growth Models22m
- Linear Population Growth6m
- Exponential Population Growth29m
- Logistic Population Growth32m
- r/K Selection10m
- The Human Population22m
- 51. Community Ecology2h 46m
- Introduction to Community Ecology2m
- Introduction to Community Interactions9m
- Community Interactions: Competition (-/-)38m
- Community Interactions: Exploitation (+/-)23m
- Community Interactions: Mutualism (+/+) & Commensalism (+/0)9m
- Community Structure35m
- Community Dynamics26m
- Geographic Impact on Communities21m
- 52. Ecosystems2h 36m
- 53. Conservation Biology24m
45. Nervous System
Neurons and Action Potentials
Video duration:
6mPlay a video:
Related Videos
Related Practice
Neurons and Action Potentials practice set
- Problem sets built by lead tutorsExpert video explanations