Please enable JavaScript.
Coggle requires JavaScript to display documents.
Lectures 24 & 25: Signaling Within Organisms II: Electrical Signals…
Lectures 24 & 25: Signaling Within Organisms II: Electrical Signals
Neurons: Basic signaling unit of nervous systems
Dendrites
Cell body
Axon
Axon Terminal
Axon Hillock
Glial Cells
Schwann Cells: Myelinate
Astrocytes: Contribute to BBB; protect brain from harmful chemicals in blood; take up neurotransmitter; supply neurons with nutrients; can release neurotransmitter in signaling; help regeneration of neurons; communicates between blood and neurons
Oligodendrocytes: Myelinate
Microglia: Immune defenses for nervous system
Resting Potential: Maintained by Na+ K+ gradient
Membrane more permeable to K+ at rest
Types of Gated Ion Channels
Chemically-Gated Ion Channels: Open or close when chemical, e.g. neurotransmitter, binds to channel.
Voltage-gated ion channels: open or close in response to a change in membrane potential. Found in axons (and in cell bodies and dendrites of some neurons).
Stretch-Gated Ion Channels: Open when the membrane is deformed by physical forces
Patch Clamping: Suction of pipette removes section of membrane-opening and closing of channels can be measured through pipette
Graded Potentials: Magnitude of change in polarization changes with strength of stimulus
Steps of an Action Potential:
Na+ Channel inactivation; K+ Channels open- repolarization & undershoot
All gated channels close; Na+ channels deinactivate
Na+ Channels open, depolarizing
Saltatory Action potentials fire only at nodes of Ranvier
Invertebrates use electrical synapses; vertebrates use chemical synapses
Electrical Synapses use gap junctions; ionotropic
Chemical Synapses use neurotransmitters, Calcium, synaptic vesicles, Metabotropic receptors
Ionotropic Receptors are themselves ion channels; fast- short-lived response
Metabotropic Receptors produce slower- longer-lived response through second messengers
Synapses
Temporal & Spatial Summation
Excitatory postsynaptic potentials (EPSPs) depolarize the postsynaptic neuron
Inhibitory postsynaptic potentials (IPSPs) hyperpolarize the postsynaptic neuron.