NEUR 2600 Lecture Notes - Lecture 3: Ependyma, Trisomy, Chromosome Abnormality
CHAPTER 3: WHAT ARE THE NERVOUS SYSTEM’S FUNCTIONAL UNITS
●Cells of the nervous system
○Debate in the 1900s
■Golgi
●The nervous system is composed of a network of interconnected
fibers: a “nerve net”
■Cajal
●Nervous system is made of discrete cells
●Neuron hypothesis
○Neurons are the units of brain function
●Both were jointly awarded a Nobel Peace Prize in 1996
●Used the Golgi stain to show that the nervous system was made up
of discrete cells, thereby supporting the neuron hypothesis
■Brainbow
●Individual cells can be visualized, which offers a way to trace
where each neuron sends its processes and how it connects with
other neurons
○Basic structure of a neuron
■Core region called the cell body, or soma (greek for body)
■Branching extensions, or dendrites (from greek for tree), collect
information from other cells
■Main root is the single axon (greek for axle) which carries messages to
other neurons
●A neuron has only one axon, but most have many dendrites
○Neurons: the basis of information processing
■Human nervous system contains 85 billion neurons
■Examining how one cell works is a source of insight that we can
generalize to other cell types
■As you learn to recognize some of the types, you will also see how their
specialized structure contributes to their functions in your body
■Most behaviours are produced by groups of hundreds or thousands of
neurons
●Functional groups of neurons, or neural networks, connect wide
areas of the brain and spinal cord
●An ongoing effort aims to map the structural connectivity-the
physical writing, or connectome-of the entire human brain
■Neurons continuously change their shape
●Grow and shrink (idea of neuroplasticity)
■The production of new neurons does take place throughout life, and some
behaviour depends on new neurons
■Most CNS neurons are with you for life and are never replaced
■Structure and function of the neuron
●Three basic subdivisions
○Dendrites
■Gather information from other neurons
○Cell body or soma
■The core region; it contains the nucleus
■Integrates the information
○Axon
■Carries information to be passed on to other cells
●Dendritic spines
○Protrusion from a dendrite that greatly increases its surface
area and is the usual point of contact with axons of other
cells
●Axon hillock
○Juncture of soma and axon, where the action potential
begins
●Axon collaterals
○Branch of an axon
●Telodendria
○End branches of an axon
●Terminal button
○Knob at the tip of an axon that conveys information to
other neurons; also called an end foot
●Synapse
○Gap between one neuron and another neuron
○Usually between an end foot of the axon of one neuron and
a dendritic spine of another neuron
●Information flow in a neuron
○Starts at the dendrite, follows into the cell body, into the
axon and lastly finds itself in the end foot
●Three functions of neurons
○Sensory neurons
■Carry information from the sensory receptors in or
on the body to the spinal cord
■Sensory neurons collect information from a source
■Bipolar neurons transmit afferent (incoming)
sensory information from the retina’s light receptors
to the neurons that carry information into the brain’s
visual centers
■Somatosensory dendrite connects directly to its
axon, so the cell body sits to one side of this long
pathway
○Interneurons (association neurons)
■Associate sensory and motor activity within the
central nervous system
■The many branches of interneurons collect
information from many sources
■Stellate (star-shaped) cell is small; many dendrites
extend around the cell body
■Pyramidal cell has a long axon, a pyramid-shaped
cell body, and two sets of dendrites, apical and
basal
■Purkinje cell is a distinctive interneuron with
extremely branched dendrites that form a fan shape
○Motor neurons
■Send signals from the brain and spinal cord to
muscles
Document Summary
Chapter 3: what are the nervous system"s functional units. The nervous system is composed of a network of interconnected fibers: a nerve net . Nervous system is made of discrete cells. Neurons are the units of brain function. Both were jointly awarded a nobel peace prize in 1996. Used the golgi stain to show that the nervous system was made up of discrete cells, thereby supporting the neuron hypothesis. Individual cells can be visualized, which offers a way to trace where each neuron sends its processes and how it connects with other neurons. Core region called the cell body, or soma (greek for body) Branching extensions, or dendrites (from greek for tree), collect information from other cells. Main root is the single axon (greek for axle) which carries messages to other neurons. A neuron has only one axon, but most have many dendrites. Human nervous system contains 85 billion neurons.
