Nervous System: Cells & Tissues Department of Biology, WCU

Nervous tissue 1. Neurons 2. Supporting cells Embryonic origin surround and wrap Embryonic origin i. ii.

Neurons single axon axon hillock axon length (up to 3 feet), nerve fiber axon collaterals telodendria terminal boutons lack Nissl bodies

Neuron classification Multipolar: 3 or more processes mostly in CNS

Neuron classification Bipolar: 2 processes (axon & dendrite) e.g. eye

Neuron classification Unipolar: single process mostly in PNS

Neurons Functional areas Conducting component (axon) Secretory component (synapse)

Chemical synapse

Chemical synapse Events infiltration of Ca++ synaptic vesicles crossing the synapse binding to postsynaptic membrane

Anaesthetics Modes of action block synaptic transmission (bind to postsynaptic membrane) raise threshold (membrane potential lecture)

Supporting cells Neuron scaffolding Types: 4 CNS, 2 PNS Common function: insulation

CNS supporting cells Neuroglia (9:1) Types 1. Astrocytes abundant link neuron to nutrients “mop up” leaky K+ and neurotransmitter

CNS supporting cells 2. Microglia protection (microbes, dead tissue)

CNS supporting cells 3. Ependymal cells ciliated permeable barrier circulation and protection

CNS supporting cells 4. Oligodendrocytes myelin sheath insulate electrical impulse

PNS supporting cells 1. Satellite cells 2. Schwann cells surround cell body function like Astrocytes 2. Schwann cells myelin sheath insulate, phagocytosis

Myelin nerve fibers (myelin vs unmylenated) lipo-protein saltatory conduction (1 to 150 m/sec)

Myelin Schwann cells Neurilemma Collateral branches

Nerve structure Collection of neurons Endoneurium Fascicles Perineurium Epineurium