Test 3: Types of Neurons & Supportive Cells – Flashcards
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What type of neuron has one axon and multiple dendrites?
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multipolar neuron
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What is the most common type of neuron, most neurons in the CNS?
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multipolar neuron
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What type of neuron has one axon and one dendrite?
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bipolar neuron
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What type of neuron has one axon and one dendrite?
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bipolar neuron
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What type of neuron is found in olfactory cells, the retina, and the inner ear?
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bipolar neuron
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What type of neuron has a single process leading away from the neuron?
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unipolar neuron
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What type of neuron are sensory cells (from skin and organs to spinal cord)
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unipolar neuron
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What type of neuron has many dendrites but no axon?
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anaxonic neuron
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What type of neuron is found in the retina, brain, and adrenal gland?
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anaxonic neuron
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There are about _____ _____ neurons in the nervous system, and neuroglia outnumber neurons by at least ____ to 1.
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one trillion, 10
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______ protect neurons and help them function.
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neuroglia (glial cells)
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Neuroglia bind neurons together and form framework for ____ tissue. In the fetus, neuroglia guide migrating ____ to their destination. If a mature neuron is not in ____ ____ with another neuron, it is covered by ____ ____. They prevent neurons from touching each other which gives precision to _____ pathways.
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nervous, neurons, synaptic contact, glial cells, conduction
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What are the four types of glia found in the CNS?
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oligodendrocytes, ependymal cells, microglia, astrocytes
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Which type of CNS glia form myelin sheaths in the CNS that speed signal conduction?
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oligodendrocytes
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What are the arm-like processes that wrap around nerve fibers?
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myelin sheaths
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Which type of CNS glia line internal cavities of the brain?
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ependymal cells
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Which type of CNS glia secrete and circulate cerebrospinal fluid (CSF)- cuboidal epithelium with cilia on apical surface?
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ependymal cells
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Which type of CNS glia wander through CNS looking for debris and damage?
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microglia
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Which type of CNS glia develop from white blood cells (monocytes) and become concentrated in areas of damage?
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microglia
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Associate _____ with myelin sheaths. Associate ______ with lining cavities and CSF. Associate _____ with helping with debris and damage. Associate ____ with being the most abundant.
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oligodendrocytes, ependymal cells, microglia, astrocytes
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What is the most abundant glial cell in the CNS, covering brain surface and most nonsynaptic regions of neurons in the gray matter?
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astrocytes
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Astrocytes provide a supportive ______, have extensions (_____ ____) that contact blood capillaries and stimulate them to form a seal called the ___-____ _____, convert ____ to _____ and supply this to neurons, secrete nerve ____ factors, communicate _____ with neurons, and regulate chemical composition of tissue fluid by absorbing excess ______. When neuron is damaged, astrocytes form hardened ____ ___ and fill in space.
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framework, perivascular feet, blood-brain barrier, glucose, lactate, growth, electrically, neurotransmitters, scar tissue
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What are the two types of glial cells of the PNS?
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satellite cells, schwann cells
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Which PNS glial cells surround the neurosomas in ganglis of the PNS?
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satellite cells
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Which PNS glial cells provide electrical insulation around the soma?
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satellite cells
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Which PNS glial cells regulate the chemical environment of the neuron?
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satellite cells
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Which PNS glial cells envelope nerve fibers in the PNS?
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schwann cells
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Which PNS glial cells wind repeatedly around a nerve fiber?
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schwann cells
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Which PNS glial cells produce a myeling sheath similar to the ones produced by oligodendrocytes in the CNS?
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schwann cells
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Which PNS glial cells assist in regeneration of damaged fibers?
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schwann cells
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Myelin sheath provides _____ around a nerve fiber. It consists of the plasma membrane and ____ ____ (20% ____, 80% _____).
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insulation, glial cells, protein, lipid
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What is the production of myelin sheath called?
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myelination
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Myelination: In the PNS, _____ ____ spiral repeatedly around a single nerve fiber. They lay down as many as one hundred layers of _____. There is no ____ between the membranes.
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schwann cells, membrane, cytoplasm
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What is the thick, outermost coil of myelin sheath that contains the nucleus and most of its cytoplasm in the PNS?
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neurilemma
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External to the neurolemma is ____ ____ and a thin layer of fibrous connective tissue called _____.
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basal lamina, endoneurium
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Myelination: In the CNS, ______ myelinate several nerve fibers in their immediate vicinity. They are anchored to multiple nerve fibers and cannot migrate around any one of them (unlike ____ ____). They must push newer layers of myelin ____ the old ones, so myelination spirals ____ towards the nerve fiber. Nerve fibers in the CNS __(do/do not)__ have neurilemma and endoneurium.
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oligodendrocytes, schwann cells, under, inwards, do not
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Many schwann cells and oligodendrocytes are need to cover _____ nerve fiber with myelin.
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one
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What are the four segments of myelin sheath?
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nodes of ranvier, internodes, initial segment, trigger zone
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What are the gaps between segments in the myelin sheath called?
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nodes of ranvier
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What are the myelin-covered segments from one gap to the next called?
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internodes
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What is the short section of nerve fiber between the axon hillock and the first glial cell?
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initial segment
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What are the axon hillock and initial segment of the myelin sheath together called? It plays an important role in initiating nerve signals.
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trigger zone
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Many CNS and PNS nerve fibers are ______.
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unmyelinated
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In the PNS, ____ ____ hold 1 to 12 small nerve fibers in surface grooves.
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schwann cells
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The membrane folds ____ around each fiber.
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once
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What are the two determining factors in the conduction speed of nerve fibers?
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diameter of the fiber, presence or absence of myelin
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_____ fibers have more ____ ____ and conduct signals more rapidly.
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large, surface area
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Myelin _____ speed signals.
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furthers
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Slow signals are sent to the ____ ____ where speed is less of an issue.
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GI tract
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Fast signals are sent to the _____ ____, where speed relates balance and coordination.
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skeletal muscles
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Regeneration of a nerve fiber can occur 1). if the ____ is in tact. 2). at least some of the _____ remains; however, regeneration is not always perfect or fast (can take up to ___ years).
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soma, neurilemma, 2
