Chapter 3 Gray matter vs. white matter

Question 1

Gray matter

Answer 1

neuronal cell bodies

Question 2

White matter:

Answer 2

bundles of axons in myelin sheath
* Account for all interhemispheric and intrahemispheric
communication
* Three types:
* Commissural
* Association
* Projection

Question 3

Three types of white fibers

Answer 3

Commissural
* Association
* Projection

Question 4

Commissural Fibers

Answer 4

Course horizontally
* Interconnect corresponding structures across
hemispheres (Interhemispheric connections)
* Ex: Corpus Callosum

Question 5

Association Fibers

Answer 5

Most numerous of the three types of white matter
fibers
* Intrahemispheric connections
* Ex: Arcuate Fasciculus

Question 6

Projection Fibers

Answer 6

Carry information
between cortex and
brainstem/spinal cord
* Ex: Corona Radiata
converge to internal
capsule

Question 7

Cells of the CNS and PNS

Answer 7

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

Question 8

Neuron Elements

Answer 8

Elements:
* Cell body a.k.a. soma
* Dendrites
* Axon

Question 9

Three types of neurons

Answer 9

Multipolar
* Bipolar
* Unipolar

Question 10

Neuron Structure
* Soma

Answer 10

Nucleus: command center; contains DNA, nucleolus
(with RNA, ribosomal assembly)

Question 11

Neuron Structure
Cytoplasm

Answer 11

Cytoplasm: aqueous substance within cell
membrane
* Contain organelles
* Used to process, metabolize protein
* Proteins sent through cell in network of microtubules

Question 12

Neuron Structure (cont.)
* Dendrites

Answer 12

Cytoplasmic extension from cell body
* Most numerous neuronal process
* Afferent (receptive of signals)
* Signal moves towards cell body
* Arborization

Question 13

Neuron Structure (cont.)
* Axons

Answer 13

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)

Question 14

Neuron Structure (cont.)
* Terminal boutons

Answer 14

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

Question 15

Neuroglia

Answer 15

Support cells of the nervous system
* Small, but 40–50x more numerous than neurons
* Found in
* Gray and white matter
* CNS and PNS

Question 16

Four types of Neuroglia in CNS

Answer 16

Astrocytes
* Oligodendroglia
* Microglia
* Ependymal cells
* One type in PNS: Schwann cells

Question 17

Astrocytes

Answer 17

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

Question 18

Oligodendroglia

Answer 18

Myelinate neurons in CNS
* One oligodendrocyte can myelinate several axons
* Insulates and speeds up action potential conduction

Question 19

Microglia

Answer 19

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

Question 20

Ependymal Cells

Answer 20

Form inner surface of ventricles
* Contribute to composition of choroid plexus (which is involved in Cerebrospinal fluid

Question 21

Schwann Cells

Answer 21

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