Characteristics - Flexible, yet sturdy barrierthat surrounds and contains the cytoplasm of a cell

Functions: Protects the cellular components

Makes contacts with other cells

Mediates entry and exits of substances

Characteristics: The liquid component of the cytoplasm that surrounds organelles

Function: The site of many chemical reactions required for a cell's existence

Characteristics: Tiny organelles composed of a type of RNA and various proteins

Function: sites of Protein Synthesis

Characteristics: extensive network of folded membranes that extends from the nuclear envelope throughout the cytoplasm

Functions: Synthesizes fatty acids and steroids

Inactivates/detoxifies drugs and other harmful substances

Characteristics: three to twenty flattened membranous sacs with bulging edges stacked on one another

Function: modify, sory and package proteins for transport to different destinations

Forms lysosomes

Characteristics: Double membraned organelle with a fluid filled space in between

REFERRED TO AS THE POWERHOUSE

site of atp synthesis

Membrane enclosed vesicles that contains digestive enzymes

Digests worn out organelles, virus & bacteria and food particles

Motile hair-like projections containing microtubules

Cilia moves fluid over the cells, flagella moves the entire cell

Contains a nucleus surrounded by cytoplasm with typical organelles

Nissl Bodies: Prominent clusters of rough endoplasmic reticulum which is the site of protein synthesis in neurons

Neurofibrils - bundles of intermediate filaments that provide the cell shape and support

Star-shaped, with many processes

Provides nutrients to neurons

Help form blood brain barrier

Smaller than astrocytes, with fewer processes; round or oval cell body

Forms supporting network around CNS neurons

produces myelin sheath

epithelial cells arranged in a single layer, may be ciliated

Lines ventricles of the brain and central canal of the spinal cord

Forms Cerebral Spinal Fluid and assists in circulation

flattened cells that encircle the PNS axons

participates in regeneration of axons

flattened cells arranged around the cell bodies of neurons in ganglia

Support neurons in PNS ganglia

Threshold - when stimulus causes membrane to depolarize to a critical level, typically -55mV

Inflow of Na+ causes potential to change from -55mV, passes 0mV and reaches +30mV

Resting membrane potential restored

Slowing of Na+ inflow and increase of K+ outflow causes potential to change from +30 mV to 0 mV to -70 mV

Membrane potential drifts toward the potassium equilibrium potential (about -90mV)

Return to -70mV occurs when K+ channels close

The period of time which an excitable cell cannot generate another action potential

A second action potential cannot be initiated, even with very strong stimulus