1. Nerve Cells & NerveNerve Cells & Nerve
ImpulsesImpulses
The Cells of theThe Cells of the
Nervous SystemNervous System
2. Anatomy of Neurons & Glia
Two Types of Cells
in t he Nervous
Syst em
1. Neurons
Receive & transmit information
to other cells
Around 100 billion to 1 trillion
2. Glia
Different functions but don’t
transmit information like neurons
Around 9x more than neurons
4. Glial Cells
Oligodendrocyte
s
Builds myelin sheaths
around certain neurons in
the brain & spinal cord
Schwann Cells
Builds myelin sheaths
around certain neurons in
the periphery of the body
5. Glial Cells
Radial Glia
A type of astrocyte that
guides the migration of
neurons & growth of axons
& dendrites during
embryonic development
6. Basic Structure of the Neuron
Cellular Membrane
2 layers of fat molecules which
allow some small uncharged
particles to flow in & out of the cell
Protein channels allow a few
charged ions to cross the
membrane but most chemicals are
kept out
Nucleus
Structure containing
chromosomes
7. Basic Structure of the Neuron
Mitochondria
Provides the cell with energy
Requires fuel & oxygen to function
Ribosomes
Site of protein synthesis
Endoplasmic
Reticulum
Thin tubes that transport newly
synthesized proteins to locations
around the cell
Proteins may have ribosomes attached
8. Basic Structure of the Neuron
Dendrites – Receives input & sends it to other neurons
Cell Body – Process input & contains cellular organelles
Axon – Sends input down & out of the neuron
Myelin Sheath – Insulates & speeds Neural Impulse
Presynaptic Terminals – Releases communication chemicals
9. Dendrit ic Spines
Short outgrowths
found on some
dendritic branches
Changes in dendritic spine
density underlie many brain
functions, including motivation,
learning, and memory.
Long-term memory is mediated
in part by the growth of new
dendritic spines
10. Other Neurons
Afferent
Neurons
Brings information into a structure
Efferent
Neurons
Sends information away from a
structure
Interneurons
Located entirely within a single
structure of the nervous system
11. The Blood-Brain Barrier
Keeps Most Chemicals
Out of the Brain
Brain doesn’t have an immune
system
Endothelial Cells
Line the walls of the
capillaries in a tight formation
in the brain
Active Transport
System
Pumps the necessary chemicals
(e.g. glucose) through the
barrier
12. The Neural
I mpulseImportant Terms
Electrical Gradient – the difference in the electrical charge inside & outside of the cell
Polarization – difference between an electrical charge between 2 locations
Resting Potential – when the electrical voltage is negatively higher inside relative to the outside
Selective Permeability – a cellular membrane that allows some, not all, molecules to pass freely
Sodium-Potassium Pump – a protein complex on the neural membrane that transports 3 sodium ions
outside of the cell while drawing 2 potassium ions into the cell in active transport
Concentration Gradient – the difference in the distribution of ions between the inside & outside of the
membrane
Hyperpolarization – when the negative charge inside of the axon increases
Depolarization – when the negative charge inside of the axon decreases
Threshold of Excitation – the level that a depolarization must reach for an action potential to occur
Action Potential – when depolarization meets or goes beyond the threshold of excitation
All-or-none Law – a neuron must have enough stimulation of a certain type to fire or it will not fire
Refractory Period – period immediately after an action potential when the neuron will resist another
action potential
13. The Action
PotentialAxon Hillock
Where the Action Potential begins
Action Potential
Regenerated due to Sodium Ions
moving down the Axon,
Depolarizing adjacent areas of the
Membrane
Moves down the axon by
regenerating itself as successive
points on the axon
Refractory Period
Prevent Action Potentials from
moving in the opposite direction
14. TheMyelinSheath
Myelin Sheath
Myelinated Axons: axons covered with a
myelin sheath
Nodes of Ranvier: short unmyelinated
sections an a myelinated axon
Saltatory Conduction
The “jumping” of the action potential
from node to node
Multiple Sclerosis: disease where the
axon loses myelin
Local Neurons
Small Neurons with Short Dendrites &
Short or non-existent axons