Chapter 2: Cells of the Nervous System (All About Neurons)

Neurons vs. Glial Cells

____ (the chocolate chips in a cookie)

• information processing

• senses changes in the environment

• communicates and commands

vs.

__ (the dough in a cookie)

• glue (holds everything together)

• insulation

• support

• nourishment

• housekeeping (gets rid of toxins)

Neurites

= tubes that expand out from the cell body

(general term for either axon or dendrite)

The Neuron Doctrine

“neurons communicate by contact NOT continuity” (Cajal)

= idea that says the nervous system is a bunch of INDIVIDUAL cells talking to each other instead of a single CONTINUOUS web

Cytosol

= Fluid of the cytoplasm, excluding organelles.

• inside of the cell

• potassium rich

Rough ER

• studded with ribosomes

• protein synthesis and transport within the cell

  • the place where RNA bind to ribosomes to begin TRANSLATION into proteins

• 

Smooth ER

functions:

• protein folding (prep before send-off)

• substance concentration control (ex. calcium)

• NO ribosomes on its surface

Mitochondria

produce ATP

• especially for maintaining membrane concentration differences

Neuronal Membrane

• separates cytoplasm from outside fluid

• protein pumps and channels line it (diff. composition depending on which region of the neuron

Cytoskeleton

= Network of protein filaments in the cell providing:

• structure

• cell division,

• cell movement and transport

has 3 parts:

1. Microtubules

2. Neurofilaments

3. Microfilaments

Polymerization

= joining of proteins into a strand

Microtubules

part of the cytoskeleton

• Tubulin proteins

• 20 nm (BIG)

• run along neurites (dendrites or axons)

• constantly being built/broken down by MAPs (microtubule-associated proteins)

• cell division

Neurofilaments

part of the cytoskeleton

• long proteins in a tight coil

• very strong

Microfilaments

part of the cytoskeleton

• Actin proteins (in braids)

• stringlike = more for cell signaling and movement

• structure

• constantly being built/broken down

Axon

• no rough ER (so no protein synthesis)

• membrane of this part of the neuron is made up of different protein channels (causes “telegraph wire” or information sending properties)

Innervation

when a neuron makes a synapse at another cell

Special Characteristics of Axon Terminal

1. microtubules (cytoskeleton) end before it

2. vesicles

3. dense proteins near synapse

4. has a LOT of mitochondria (needs a lot of ATP for the membrane pumps)

Synaptic Transmission

When info passes through the synapse

pre-synaptic (electric impulse) —> neurotransmitters in the synapse (chemical signal) to post-synaptic (electrical impulse)

Axoplasmic Transport

the flow of materials down the axon

• since there are no ribosomes in axons or axon terminals, they depend on the soma from protein generation

Wallerian Degeneration

When axons die from being cut off from the soma (axoplasmic transport stopped = flow of material stopped)

Anterograde Transport

when kinesin proteins move material (in vesicles) by “walking” down the axon from soma to axon terminal

Retrograde Transport

When dynein proteins move material back up axon from axon terminal to the soma

Dendrites

Antennae of the neuron

• have many receptor proteins to detect neurotransmitters

Dendritic Spines

Bumps on dendrites that receive special input

• they recognize specific types or amounts of chemical synaptic activity

Stellate Cell

star shaped neuron

• can be spiny or aspinous

Pyramidal Cell

a cell shaped like a pyramid

• always spiny

Golgi Type I

classification of neurons by length

= long axons (from brain end to end)

Golgi Type II

classification of neurons by length

= short axons (local circuits)

Astrocyte

a type of glial cell that fills space between neurons (influences neurite growth)

• majority of CNS neurons

• regulates chemicals (like K+ ions)

• stops neurotransmitters from spreading beyond synapses (can even remove them from the synaptic cleft)

Myelinating Glia

a type of glial cell whose membrane wraps around axons for insulation

Oligodendroglial Cells

a type of myelinating glia

• only in CNS

• myelinates multiple axons

Schwann Cells

a type of myelinating glia

• only in PNS

• myelinates a single axon

• regenerates (especially after a demyelinating disease)

Microglia

a type of glial cell that removes debris/toxins in the brain

• “immune cells” of the brain

• the “protectors” of the brain