BCS 1.2 Cells of the Nervous System

Central Nervous System (CNS)

Consists of the brain and spinal cord; interprets sensory input, initiates movement, and mediates cognition.

Peripheral Nervous System (PNS)

Located outside the skull and spine; brings sensory info into the CNS and carries motor signals out.

Functional Unit of the Nervous System

The neuron, specialized for receiving, conducting, and transmitting electrochemical signals.

External Features of a Neuron

Dendrites receive inputs, the cell body (soma) integrates info, and the axon transmits output.

Neuronal Differences from Other Cells

Neurons stop dividing after birth and have specialized structures like dendrites and axons.

Neuron Cell Membrane

A lipid bilayer with embedded proteins providing selective permeability.

Golgi Stain

Silver stain that colors some neurons black, allowing visualization of shape and connectivity.

Nissl Stain

Selectively stains cell bodies (nuclei and ribosomes) to count neurons in an area.

Anterograde vs. Retrograde Tract Tracing

Anterograde traces axons projecting away; retrograde traces axons projecting into cell bodies.

Electron Microscopy

Provides fine structural details and definitive evidence for the neuron doctrine.

Two Photon Fluorescence Microscopy

Uses laser beams on living tissue, showing that dendritic spines are remodeled over time.

CNS vs. PNS Cell Body Clusters

Called nuclei in the CNS and ganglia in the PNS.

CNS vs. PNS Axon Bundles

Called tracts (white matter) in the CNS and nerves in the PNS.

Afferent vs. Efferent Connections

Afferent means approaching an area; efferent means exiting.

Glial Cells

Helper cells that outnumber neurons up to 5:1 and provide structural and metabolic support.

Oligodendrocytes vs. Schwann Cells

Oligodendrocytes myelinate multiple CNS areas; Schwann cells myelinate one PNS area.

Microglia

CNS glial cells that activate to engulf injured or diseased tissue.

Astrocytes

Star-shaped CNS glia that control microenvironments, form the blood-brain barrier, and aid synapses.

Satellite Cells

Flattened PNS glial cells that control the microenvironment around a single neuron.