Key Terms
Dendrites
Tree-like extensions that receive incoming signals at synapses. Can have dendritic spines to increase surface area for m
Cell body (soma)
Contains the nucleus; integrates incoming signals passively.
Axon hillock
Junction between cell body and axon; integrates signals from multiple synapses; where the "go/no-go" decision happens.
Axon
Tube that carries the signal away from the soma toward axon terminals. Usually one per neuron.
Axon terminals
Where the signal ends and neurotransmitters get released.
Myelin sheath
Fatty insulation around axons; speeds up signal conduction; produced by GLIAL CELLS, not the neuron itself.
Nodes of Ranvier
Periodic gaps in the myelin sheath where the signal gets recharged as it travels.
Net result
More positive charges outside, more negative charges inside.
Threshold
-55 mV. If the membrane depolarizes to that level, the action potential fires.
Refractory period
While Na+ channels are inactivated and K+ channels are still open, the neuron cannot fire again. This enforces one- dire
EPSP (Excitatory Postsynaptic Potential)
Positive ions enter; membrane depolarizes; neuron more likely to fire. Example: acetylcholine at the neuromuscular junct
IPSP (Inhibitory Postsynaptic Potential)
Negative ions enter; membrane hyperpolarizes; neuron less likely to fire. Example: GABA opens Cl- channels.
Long-Term Potentiation (LTP)
Synapse gets stronger
Long-Term Depression (LTD)
Synapse gets weaker
Dura mater
Outermost; tough; protects; also contains veins returning blood from brain Arachnoid mater: middle; web-like Pia mater: