Neurophysiology IV Flashcards
EPSP
Excitatory Postsynaptic Potential
- produces small local depolarization
- influx of Na+
- pushes cell closer threshold
IPSP
Inhibitory Postsynaptic Potential
- produces small hyperpolarization
- influx of Cl-
- pushes cell further threshold
Axon Hillock
Point at which it is decided whether to fire an action potential
- balances excitatory and inhibitory potentials
Spatial Summation
EPSPs from different axon terminals fire simultaneously
- Triggers action potential easily
Temporal Summation
EPSPs from same axon terminals
- Because of refractory period, more difficult to trigger action potential
Convergence & Divergence
Ex: Visual System
- Information from 100 million light receptors converges on 1 million axons
- Diverges to billions of cortical neurons
Glial Cells
- Oligodendrocytes
- Schwann Cells
- Microglia
- Astrocytes
Oligodendrocytes
Glial cell found in CNS
- Myelin projections wrap around several axons to myelinate them
Schwann Cells
Glial cell found in PNS
- Fat cell wraps around axon to myelinate it
- One-to-one
Microglia
Immune cells of brain
- Break down debris
- Fight infection
- Disintegrate dead neurons
Astrocytes
Glial cell that makes up majority of CNS
- Promotes synapse formation
- Regulates blood-brain barrier
- Clears excess neurotransmitter
- Regulates blood flow
Tripartite Synapse
Astrocytes wrap around synapse
- Enhance signal by releasing more neurotransmitters
- Clear excess neurotransmitters
Sequence of Synapse Transmission
- Action potential causes release of neurotransmitters in synapse
- Voltage-gated Ca2+ channels open, Ca2+ enter
- Synaptic vesicles fuse with membrane and release transmitter into cleft
- Transmitters bind to postsynaptic receptors
- Ion flow creates EPSP or IPSP
- Excess transmitter is inactivated by enzymes and removed by transporters
