NonNeuronal Cells of the Nervous System Neuroglia Cant

Non-Neuronal Cells of the Nervous System Neuroglia Can’t generate or transmit nerve impulses (signals)

Non-Neuronal Cells of the Nervous System

Central Nervous System (4 kinds of cells) 1) Astrocytes • Provides neurons with nutrients & energy • Physical support • Forms the “Blood: Brain Barrier”

2) Oligodendrocytes • Secretes myelin sheaths around the axon of the neurons (this directs impulse)

3) Microglia • Are like Macrophages • Scavenge cell debris • Protects from pathogens in the brain

4) Ependymal Cells • Line the hollow cavities (ventricles) • Secretes cerebral & spinal fluid which acts as ‘shock absorber’, and distributes nutrients in the brain and spinal cord

Central Nervous System

Peripheral Nervous System 1. A myelin system 2. Protects cells

Transmission Of the Nerve Impulse

Before arrival of an Action (Electric) Potential Synapse (2 cells) Page 399

Action Potential opens channels that cause Calcium ions to move into the Synaptic Bulb

Vesicles fuse to the Synaptic Membrane

Neurotransmitters released into ‘cleft’ Examples: • Glutamate (most common in brain) • Gamma-aminobutyric acid (GABA) • Dopamine • Acetylcholine • Epinephrine • Histamine • Serotonin • Neurotensin • Nitric Oxide • Neuropeptide Y

Neurotransmitters bind to receptors in next neuron. . . opening Sodium channels. This initiates an Action Potential in the next Neuron.

Neurotransmitters are cleared out of cleft. By: • Diffusion • Reuptake by upper neuron • Enzymatic breakdown