Synaptic Transmission and AP Flashcards
2 types of synapses between neurons
Chemical - most common
Electrical
How do chemical synapses work?
Unidirectional. Presynaptic membrane secretes neurotransmitters that act on receptors in the postsynaptic neuron. Can be excitatory or inhibitory.
Conventional neurotransmitters in chemical synapses
Amino acids
Biogenic amines - dopamine, serotonin, Epi/NorEpi
Achetylcholine
Endorphins
Unconventional neurotransmitters in chemical synapses
Endocannabinoids
Gastrotransmitters
How do electrical synapses work?
Cytoplasm of adjacent cells is directly connected via Gap Junctions. Allows for bidirectional free movement of ions.
2 types of chemical synapse receptors
Metabotropic
Ionotropic
What type chemical synapse receptor acts through a second messenger system?
metabotropic.
Give an example of a metabotropic receptor
GPCRs open ion channels and then activate cAMP (a second messenger)
What type of chemical synapse receptor directly opens ion gated channels?
Ionotropic
What ion channel is opened by excitatory neurotransmitters and induces depolarization?
Cation (Na+ channels)
What ion channel is opened by inhibitory neurotransmitters and induces hyperpolarization?
Anion (Cl- channels)
What are graded potentials?
local membrane potentials that integrate at the axon hillock to generate an action potential
What determines the strength of a graded potential?
intensity of the stimulus
What is the threshold voltage that the integration of graded potentials must reach to generate an AP at the trigger zone?
-55mV
Depolarizing graded potentials
Shift toward threshold (+)
Excitatory neurotransmitters (cation channels)
Excitatory post synaptic potentials (EPSP)
Hyperpolarizing graded potentials
Shift away from threshold (more neg)
Inhibitory neurotransmitters (anion channels)
Inhibitory post synaptic potentials (IPSP)
2 types of graded potentials
Spatial
Temporal
How do spatial graded potentials generate an AP?
Graded potentials from different synapses collect in the axon hillock. If the sum of the EPSP and IPSP reaches -55mV, an AP occurs.
How do temporal graded potentials generate an AP?
Successive discharges from a single synapse collect in the post synaptic neuron. If the discharges are rapid enough to combine, and reach -55mV, an AP occurs.
What is saltatory conduction?
Action potentials occur only at Nodes of Ranvier in myelinated fibers. AP jumps from node to node.
What do Nodes of Ranvier have a lot of that make them so good at conducting electrical impulses?
Ion channels
Decremental conduction
Decrease in stimulus which leads to decrease in response down the fiber.
Corrected in each Node of Ranvier
