nervous tissue

• CNS

  brain and spinal cord
• PNS

  nerves, sensory receptors, ganglia
• in nervous tissues, cellular processes take up space, not ECM
• neurons are widely scattered with only limited contact at extremities
• PNS contains

  somatic nervous system and autonomic nervous system
• ANS contains

  sympathetic and parasympathetic
• somatic and autonomic are made of nerves and ganglia
• glial cells in CNS

  oligodendrocytes, astrocytes, microglia, ependymal cells
• glial cells in PNS

  schwann cells and satellite cells
• schwann cells are found in nerves and ganglia
• satellite cells are only found in ganglia
• summation occurs at the axon hillock
• axon terminals often synapse at dendrites
• bipolar neurons have 2 processes and are involved in vision, taste, smell and hearing
• unipolar neurons have 2 axon and dendrites and sense pain, temperature, touch, and vibration
• multipolar neurons have 1 axon and numerous dendrites, CNS to periphery
• oligodendrocytes may myelinate many different axons at once via long cytoplasmic processes
• schwann cells are intimately associated with their axons
• unmyelinated axons are still eneloped by schwann cells
• synapses consist of

  axon terminals with synaptic vesicles, presynaptic membrane, synaptic cleft, postsynaptic membrane
• synaptic vesicles contain neurotransmitters
• synaptic cleft is a small space between axon terminal and membrane
• post synaptic membrane contains receptors
• white matter

  myelinated axons carrying information
• grey matter

  neurons and neuropil recieving infomation
• neuropil is where synapses are found
• neuropil is made of axons, dendrites, and glial cells
• astrocytes have many cytoplasmic processes that extend into the surrounding tissue of the brain and spinal cord
• astrocytes form end feet that cover blood vessels and form a component of the blood brain barrier
• astrocytes have gap junctions and form scar tissue
• microglial cells are resident macrophages in the CNS and are derived from monocytes
• ependymal cells line the central canal of the spinal cord and brain passages, carrying CSF
• types of ganglia

  dorsal root, sympathetic, parasympathetic
• ganglia consists of large soma, encircled by satellite cells and axons
• sympathetic and parasympathetic ganglia are autonomic
• parasympathetic ganglia is in the wall of the structure its innervating
• sympathetic ganglia are stand alone structures
• nerve cell bodies are not found in peripheral nerves
• post synaptic membranes are usually dark as there is a high density of ligand gated ion channels
• spinal cord is tracts of predominantly myelinated axons and glial cells