lecture: https://www.youtube.com/watch?v=_6dPCNHxfDI&t=1s

Glia

• Make up 80-90% of CNS
• Perform support functions
  Macroglia
• Astrocytes
  • Named after their star-like structure
  • Multitaskers
  • Attach to neurons to remain in place in a liquid environment
  • Interact with capillaries to form the blood-brain barrier (BBB)
  • Prevents substances in circulation from entering nervous system tissue
  • Some toxins do get through, which is why we have psychoactive drugs
  • Interactions with the capillaries can maintain blood flow based on local activity, visible on a larger scale in an fMRI
  • Regulate synapses, or communication points between neurons
  • Absorb certain neurochemicals to prevent excessive concentrations and stop others from traveling away from synapses
  • Release chemicals themselves
  • Play a role in modulating neural transmission and communication
  • Neurons behave differently when astrocytes are present
  • Astrocytes can become reactive to damage, with both positive and negative outcomes
  • Can form scar tissue, offering short-term benefits but potentially hindering neural regrowth
  • Glutamate release, in large quantities, can be toxic
• Ependymal Cells
  • Cube-like cells that line ventricles
  • Wave around in cerebrospinal fluid (CSF)
  • Contribute to its mobility
  • In some parts of the ventricular system, they interact with blood supply in the Choroid Plexus
  • Where CSF is produced
  • Help with infection, though this often doesn't end well for the cells
  • Supplies brain cells with protein from the CSF
  • Capable of regeneration
• Oligodendrocytes
  • Produce myelin to insulate nerve fibers, transferring information more quickly and efficiently
  • Multiple sclerosis attacks myelin, causing fatigue and misfiring neurons
  • Each oligodendrocyte can make several myelin segments
  • Contribute to the stability of the nervous system
  • Form scar tissue, which inhibits regrowth (CNS damage is permanent)
• Schwann Cell (which myelinate peripheral nerves)
  • Can make only one segment
  • Respond differently to injury
  • Usually helpful following injury, facilitating the reattachment of limbs or cadaver parts

Microglia

• Mobile, move to areas of damage
• Clean up debris
• Have the ability to prune synapses
• Synapses change every time we learn something new
• They prune unwanted information, usually during sleep
• Infants with autism spectrum disorder may not prune enough synapses during development

Neurons

• Process and communicate information

The Neural Membrane

• Typically, dendrites are on the receiving end of information
• Axon transmits information
• Very thin membrane (2 molecules thick)
• Some channels respond to chemical messengers
• Most allow a single type of molecule
• Retrograde transport is a mechanism for moving substances from the axon back to the cell body.
• Action potential is a rapid rise and fall in electrical charge across a neuron's membrane, allowing the neuron to transmit a signal.

Cytoskeleton

• Layer of oil, shapeless
• Skeleton needed for shape
• Microtubules
  • Structure and transport
  • Involved in Alzheimer's
• Intermediate filament
  • Provides mechanical support
• Microfilaments
  • Involved in cell movement and shape
    The Cell Body
• Large number of mitochondria in the cell
  Axons and Dendrites
• Provide surface for incoming signals
• Axon terminal is where neurotransmitters are released
• Presynaptic refers to the sending side
• Postsynaptic is the receiving side
  Unipolar Neuron
• Lots found in the somatosensory system
  Bipolar Neuron
• Two processes
• Axon and dendrite
  Multipolar Neuron
• Complex shapes
  Functional Variations in Neurons
• Form follows function
• Sensory Neurons
• Carry sensory information toward the CNS
• Interneurons
• Everything else
• Most processing requires many of these
• Not involved in reflex arcs
• Motor Neurons
• Communicate with muscles