Neural final- nerve cell physiology and synaptic function

cell body

Main part of the neuron; contains nucleus; controls all cell functions

nucleus

Contains DNA; blueprint for cell type and function

cytoplasm

Fluid filling the cell body; metabolizes proteins for maintenance and growth

dentrites

Afferent (incoming) fibers; bring signals TO the cell body from other cells

axon

Efferent (outgoing) process; sends signals AWAY to other neurons or organs

axon hillock

Where the axon leaves the cell body; site of action potential initiation

nodes of raniver

Gaps in the myelin sheath; contain voltage-gated Na⁺ channels

myelin sheath

Insulates the axon; prevents electrical energy loss during conduction

resting potential

−60 to −70 mV; interior of cell is negatively charged relative to outside

action potential

Rapid change in voltage across the cell membrane (negative → positive)

threshold

−50 to −55 mV; minimum voltage needed to trigger an action potential

all-or-none

APs have the same amplitude; frequency increases with stronger stimuli

refractory period

After an AP fires, another cannot immediately be generated (Na⁺ channels temporarily inactivated)

saltatory conduction

In myelinated axons, APs jump between nodes of Ranvier — faster conduction

subthreshold

stimulus too weak nothing happens

threshold

stimulus reaches -50 to -55 mV AP triggered

subprathreshold

stimulus exceeds threshold AP produced higher frequency with stronger stimuli

hyperpolarization

Membrane potential rises toward threshold; voltage-gated Na⁺ channels begin to open

depolarization

Rapid influx of Na⁺; cell interior becomes increasingly positive; potential approaches +61 mV

overshoot

Peak positivity; K⁺ channels begin to open

repolarizatio

Na⁺ channels close; K⁺ exits cell; membrane potential drops back toward resting level

hyperpolarization

Membrane overshoots resting potential; becomes more negative than resting state; Na⁺ channels reset

resting state

Na⁺/K⁺ pump restores ion gradients using ATP; both channel types deactivated

synapse

Small gap between pre- and post-synaptic cells; allows neuron-to-neuron communication

synaptic terminals

contain and store neurotransmitters in vesicles

receptor proteins

located on postsynaptic membrane; bind neurotransmitters

neurotransmitter release

An arriving action potential causes vesicles to release neurotransmitters into the cleft

EPSP

Excitatory postsynaptic potential — depolarizes the postsynaptic membrane

IPSP

Inhibitory postsynaptic potential — hyperpolarizes the postsynaptic membrane

electrical synapses

fast direct communication (vision, hearing)

ligand-gated

opened by binding of neurotransmitters or signaling molecules

voltage-gated

opened or closed based on the voltage across the membrane