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Nerve tissue
n/a
44
Anatomy
Undergraduate 3
09/30/2012

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Term
How are cells arranged in Nerve tissue?
Definition
Cells are densely packed and intertwined. There are two main types.
Term
What are the types of cells in nervous tissue?
Definition
1. Neurons- transmit electical signals
2. Support cells (neuroglial cells)- nonexcitable, surround and wrap neurons, and have several functions
Term
What is the neuron cell body also known as?
Definition
perikaryon
Term
What do most neuronal cell bodies contain?
Definition
usual organelles, plus other structures called Nissl bodies.
Term
What are Nissl bodies?
Definition
clusters of rough ER and free ribosomes
stain darkly and renew membranes of the cell
Term
What are the neuron membrane processes?
Definition
dendrites and axons
Term
What are dendrites?
Definition
extensively branching from the cell body
transmit electrical signals toward cell body. Function as receptive sites.
Term
What are axons?
Definition
Neuron has only one.
-they produce and conduct action potentials.
Transmit impulses away from cell body
Term
In axons, what is the function of neurofilaments, actin microfilaments, and microtubules?
Definition
-provide strength along the length of axon and
-aid in the transport of substances to and from the cell body= axonal transport.
Term
What is the initial segment of the axon called and what does it do?
Definition
Axon hillock generates action potential
Term
What are the multiple branches at end of axon called?
Definition
1. Terminal branches (telodendria)
2. End in knobs called axon terminals (end bulbs or boutons)
Term
What are the three structural classes of neurons?
Definition
1. multipolar
2. bipolar
3. unipolar
Term
Describe a multipolar neuron?
Definition
more than two processes; usually many dendrites and one axon.
Term
Describe a bipolar neuron?
Definition
two processes that extend from opposite sides of cell body
Term
Describe a unipolar neuron?
Definition
one process that emerges from cell body and divides like an inverted letter T.
Term
What are the supporting cells in the CNS?
Definition
Neuroglia
Term
What are neuroglia?
Definition
usually referes to supporting cells in CNS
-glia cells have branching processes and a central cell body
-outnumber neurons 10 to 1
-Make up half the mass of the brain
Term
How many types of neuroglial cells are there in the CNS vs PNS?
Definition
CNS= 4 types of glial cells
PNS= 2 types of supportive cells.
Term
What are the types of CNS neuroglial cells?
Definition
Astrocytes, Microglia, Ependymal, Oligodendrocytes
Term
What is the most abundant glial cell type?
Definition
astrocytes
Term
What are astrocytes?
Definition
take up and release ions to control the environment around neurons.
Recapture and recycles neurotransmitters.
Involved w/ synapse formation in developing neural tissue
Produce molecules necessary for neural growth
may be involved in memory (degeneration of astrocytes may play a role in alzheimer's disease.
Term
What are microglia?
Definition
smallest and lease abundant, immune cells.
**phagocytes- the macrophages of the CNS.
-engulf invading microogranism and dead neurons.
-derive from blood cells called monocytes
Term
What are ependymal cells?
Definition
produce cerbrospinal fluid
-line the central cavity of the spinal cord and brain.
-bear cilia, helping to circulate CSF
Term
What are oligodendrocytes?
Definition
have few branches.
Wrap their cell processes around axons in CNS
-produce myelin sheaths
Term
What are the types of PNS neroglial cells?
Definition
satellite cells
schwann cells
Term
What are satellite cells?
Definition
surround neuron cell bodies w/ ganglia
Term
What are schwann cells?
Definition
(neurolemmocytes)- surround axons in PNS and form myelin sheath around axons of PNS
Term
What are the Myelin Sheaths?
Definition
segmented structures composed of the lipoprotein myelin. Form an insulating layer to prevent leakage of electrical current.
**Increase the speed of impulse conduction (50X)
Term
What is a disease dealing w/myelin sheaths?
Definition
Mulitple sclerosis- autoimmune disease; degeneration of myelin, weakness, difficulty walking, vision disturbances
Term
In the PNS, myelin sheaths are formed by --, they are developed during --, they are arranged by --, they form --, which make electrical signals --
Definition
formed by schwann cells, developed during fetal period and in first year of postnatal life, shwann cells wrap in concentric layers around the axon, which covers the axon in a tightly packed coil of membranes, they form nodes of ranvier which are gaps along axon that allows electrical signals to jump from node to node increasing speed.
Term
Which axons are myelinated? Which are not? What is the difference?
Definition
thick axons are myelinated
thin axons are unmyelinated- they conduct electric signals more slowly, and are still supported by schwann cells but do not form sheaths.
Term
In the CNS, oligodendrocytes form --, have -- processes, and coil --.
Definition
myelin sheaths
multiple
around seveal different axons
Term
What are nerves?
Definition
cordlike organs in PNS
consist of numerous axons wrapped in connective tissue.
Term
What are nerve fascicles?
Definition
groups of axons bound into bundles.
Term
What are the layers of nerves?
Definition
endoneurium, perineurium, epineurium
Term
What is the endoneurium?
Definition
layer of delicate connective tissue surrounding the axon
Term
What is the perineurium?
Definition
connective tissue wrapping surrounding a nerve fascicle
Term
What is the epineurium?
Definition
whole nerve is surrounded by tough fibrous sheath.
Term
Gray vs white matter in the CNS?
Definition
gray- cell bodies, dendrites, axon terminals
white- axons
Term
How are grey and white matter distrubuted?
Definition
Not randomly. Generally:
Gray matter is centrally located
White matter is external to central gray.
additional layer of gray matter external to white matter bc of groups of neurons migrating externally, forming cortexes- the outer layer of gray matter, located in cerebrum and cerebellum **
Term
Distrubution of Gray matter:
Definition
1. nuclei- clusters of cell bodies in CNS
2. Ganglia- clusters of cell bodies in PNS
3. Columns- rows of cell bodies
4. Cortex- continuous sheet (cerebrum and cerebellum)
Term
Distrubution of White Matter:
Definition
Tracts
Term
What does the nervous system develop from?
Definition
the dorsal ectoderm
Term
How does the nervous system develop from dorsal ectoderm?
Definition
invaginates to form the neural tube and neural crest.
The neural tube walls begin as neuroepithelial cells. These cells divide and become neuroblasts.
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