Chapter 3 Gray matter vs. white matter Flashcards
Gray matter
neuronal cell bodies
White matter:
bundles of axons in myelin sheath
* Account for all interhemispheric and intrahemispheric
communication
* Three types:
* Commissural
* Association
* Projection
Three types of white fibers
Commissural
* Association
* Projection
Commissural Fibers
Course horizontally
* Interconnect corresponding structures across
hemispheres (Interhemispheric connections)
* Ex: Corpus Callosum
Association Fibers
Most numerous of the three types of white matter
fibers
* Intrahemispheric connections
* Ex: Arcuate Fasciculus
Projection Fibers
Carry information
between cortex and
brainstem/spinal cord
* Ex: Corona Radiata
converge to internal
capsule
Cells of the CNS and PNS
Neurons communicate with nerve impulses within the
nervous system
* Two primary types of cells: neurons and neuroglia
(glial cells)
* Excitatory and inhibitory impulses sent by
.Neauron
* neuroglia support, protect,
and repair
Neuron Elements
Elements:
* Cell body a.k.a. soma
* Dendrites
* Axon
Three types of neurons
Multipolar
* Bipolar
* Unipolar
Neuron Structure
* Soma
Nucleus: command center; contains DNA, nucleolus
(with RNA, ribosomal assembly)
Neuron Structure
Cytoplasm
Cytoplasm: aqueous substance within cell
membrane
* Contain organelles
* Used to process, metabolize protein
* Proteins sent through cell in network of microtubules
Neuron Structure (cont.)
* Dendrites
Cytoplasmic extension from cell body
* Most numerous neuronal process
* Afferent (receptive of signals)
* Signal moves towards cell body
* Arborization
Neuron Structure (cont.)
* Axons
Single cytoplasmic extension from cell body thinner and
longer than dendrites
* Branches at distal end
* Most covered in myelin sheath
* A “nerve fiber” is the axon plus protective myelin sheath
* Efferent (sending out)
* Transmits information away fromcell body
* Segments:
* Initial segment called Axon Hillock
* Axon
* Terminal Boutons (synaptic boutons)
Neuron Structure (cont.)
* Terminal boutons
Terminal boutons: release neurotransmitter from end
of axon to surface of nearby neurons’ dendrites
across the synaptic cleft .
* NT stimulates receptor site of next nerve cell
* synapse includes the
* knob/button/bouton, synaptic cleft, receptive site
of connecting cell
Neuroglia
Support cells of the nervous system
* Small, but 40–50x more numerous than neurons
* Found in
* Gray and white matter
* CNS and PNS
Four types of Neuroglia in CNS
Astrocytes
* Oligodendroglia
* Microglia
* Ependymal cells
* One type in PNS: Schwann cells
Astrocytes
Function
* Fill interneuronal space in CNS
* Separate neurons from each other except at synaptic cleft
* Provide stiffness and overall support
* Contribute to blood-brain barrier
* Aid in neural recovery by sealing cavity (following
damage/injury) and forming a cyst (in large areas) or filling
the space with a glial scar
Oligodendroglia
Myelinate neurons in CNS
* One oligodendrocyte can myelinate several axons
* Insulates and speeds up action potential conduction
Microglia
Small cells with smallest percentage of glia population
in CNS
* Activate when antigens present in CNS
* Travel to site of neuronal insult/injury and
phagocytose cellular debris leaving a cavity
Ependymal Cells
Form inner surface of ventricles
* Contribute to composition of choroid plexus (which is involved in Cerebrospinal fluid
Schwann Cells
Only support cell in PNS
* Performs same functions as glial cells in CNS
* Produces myelin
* Aids in neural recovery
* Structural support
* Surrounds myelinated and unmyelinated neurons
in PNS to separate from extracellular environment
