SYNAPTIC TRANSMISSION, GLIAL CELLS & MYELINATION

Synapse

Junction where a neuron communicates with another cell.

Presynaptic cell

Cell that sends a signal across a synapse.

Postsynaptic cell

Cell that receives a synaptic signal.

Synaptic cleft

Small space separating cells at a chemical synapse.

Neurotransmitter

Chemical messenger released by a neuron to communicate with a target cell.

Synaptic vesicle

Membrane-bound structure that stores neurotransmitters.

Chemical synapse

Synapse where neurotransmitters transmit signals between cells.

Electrical synapse

Synapse where ions flow directly between cells through gap junctions.

Calcium's role in neurotransmitter release

Calcium enters the axon terminal and triggers synaptic vesicle fusion.

Postsynaptic receptor

Protein that detects neurotransmitters and initiates a cellular response.

Excitatory postsynaptic potential (EPSP)

Graded depolarization that increases the likelihood of an action potential.

Inhibitory postsynaptic potential (IPSP)

Graded change that decreases the likelihood of an action potential.

Synaptic integration

Combining excitatory and inhibitory signals to determine whether threshold is reached.

Neurotransmitter reuptake

Transport of neurotransmitter back into cells from the synaptic cleft.

Enzymatic degradation

Breakdown of neurotransmitters by enzymes to help terminate signaling.

Neuroglia (glial cells)

Supporting cells that protect

Astrocytes

CNS glial cells that support neurons and help maintain the extracellular environment.

Oligodendrocytes

CNS glial cells that form myelin around axons.

Microglia

CNS immune cells that remove debris and respond to tissue damage.

Ependymal cells

Cells lining CNS cavities that help with cerebrospinal fluid function.

Neurolemmocytes (Schwann cells)

PNS glial cells that form myelin around peripheral axons.

Satellite cells

PNS glial cells that surround and support neuron cell bodies in ganglia.

Myelination

Formation of an insulating sheath around an axon.

Saltatory conduction

Rapid conduction in which action potentials are regenerated at successive myelin sheath gaps.

Axon diameter and conduction speed

Larger-diameter axons generally conduct action potentials faster.

Chemical synaptic transmission

Action potential reaches the axon terminal, calcium enters, neurotransmitters are released, and postsynaptic receptors respond.

Myelin sheath

Insulating layer around an axon that reduces current loss and increases conduction speed.

Myelin sheath gaps (nodes of Ranvier)

Exposed regions of the axon membrane where action potentials are regenerated