Term
| How are cells arranged in Nerve tissue? |
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Definition
| Cells are densely packed and intertwined. There are two main types. |
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Term
| What are the types of cells in nervous tissue? |
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Definition
1. Neurons- transmit electical signals
2. Support cells (neuroglial cells)- nonexcitable, surround and wrap neurons, and have several functions |
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Term
| What is the neuron cell body also known as? |
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Definition
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Term
| What do most neuronal cell bodies contain? |
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Definition
| usual organelles, plus other structures called Nissl bodies. |
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Term
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Definition
clusters of rough ER and free ribosomes
stain darkly and renew membranes of the cell |
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Term
| What are the neuron membrane processes? |
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Definition
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Term
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Definition
extensively branching from the cell body
transmit electrical signals toward cell body. Function as receptive sites. |
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Term
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Definition
Neuron has only one.
-they produce and conduct action potentials.
Transmit impulses away from cell body |
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Term
| In axons, what is the function of neurofilaments, actin microfilaments, and microtubules? |
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Definition
-provide strength along the length of axon and
-aid in the transport of substances to and from the cell body= axonal transport. |
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Term
| What is the initial segment of the axon called and what does it do? |
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Definition
| Axon hillock generates action potential |
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Term
| What are the multiple branches at end of axon called? |
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Definition
1. Terminal branches (telodendria)
2. End in knobs called axon terminals (end bulbs or boutons) |
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Term
| What are the three structural classes of neurons? |
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Definition
1. multipolar
2. bipolar
3. unipolar |
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Term
| Describe a multipolar neuron? |
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Definition
| more than two processes; usually many dendrites and one axon. |
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Term
| Describe a bipolar neuron? |
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Definition
| two processes that extend from opposite sides of cell body |
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Term
| Describe a unipolar neuron? |
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Definition
| one process that emerges from cell body and divides like an inverted letter T. |
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Term
| What are the supporting cells in the CNS? |
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Definition
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Term
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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 |
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Term
| How many types of neuroglial cells are there in the CNS vs PNS? |
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Definition
CNS= 4 types of glial cells
PNS= 2 types of supportive cells. |
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Term
| What are the types of CNS neuroglial cells? |
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Definition
| Astrocytes, Microglia, Ependymal, Oligodendrocytes |
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Term
| What is the most abundant glial cell type? |
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Definition
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Term
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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. |
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Term
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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 |
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Term
| What are ependymal cells? |
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Definition
produce cerbrospinal fluid
-line the central cavity of the spinal cord and brain.
-bear cilia, helping to circulate CSF |
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Term
| What are oligodendrocytes? |
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Definition
have few branches.
Wrap their cell processes around axons in CNS
-produce myelin sheaths |
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Term
| What are the types of PNS neroglial cells? |
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Definition
satellite cells
schwann cells |
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Term
| What are satellite cells? |
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Definition
| surround neuron cell bodies w/ ganglia |
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Term
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Definition
| (neurolemmocytes)- surround axons in PNS and form myelin sheath around axons of PNS |
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Term
| What are the Myelin Sheaths? |
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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) |
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Term
| What is a disease dealing w/myelin sheaths? |
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Definition
| Mulitple sclerosis- autoimmune disease; degeneration of myelin, weakness, difficulty walking, vision disturbances |
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Term
| In the PNS, myelin sheaths are formed by --, they are developed during --, they are arranged by --, they form --, which make electrical signals -- |
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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. |
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Term
| Which axons are myelinated? Which are not? What is the difference? |
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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. |
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Term
| In the CNS, oligodendrocytes form --, have -- processes, and coil --. |
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Definition
myelin sheaths
multiple
around seveal different axons |
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Term
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Definition
cordlike organs in PNS
consist of numerous axons wrapped in connective tissue. |
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Term
| What are nerve fascicles? |
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Definition
| groups of axons bound into bundles. |
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Term
| What are the layers of nerves? |
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Definition
| endoneurium, perineurium, epineurium |
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Term
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Definition
| layer of delicate connective tissue surrounding the axon |
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Term
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Definition
| connective tissue wrapping surrounding a nerve fascicle |
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Term
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Definition
| whole nerve is surrounded by tough fibrous sheath. |
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Term
| Gray vs white matter in the CNS? |
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Definition
gray- cell bodies, dendrites, axon terminals
white- axons |
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Term
| How are grey and white matter distrubuted? |
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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 ** |
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Term
| Distrubution of Gray matter: |
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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) |
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Term
| Distrubution of White Matter: |
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Definition
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Term
| What does the nervous system develop from? |
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Definition
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Term
| How does the nervous system develop from dorsal ectoderm? |
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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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