A&P - Chapter 11 Sections 11.1 - 11.2
myelination
The *formation of the myelin sheath* is known as ____. During this process, a *Schwann cell wraps itself outward away from the axon in successfully tighter bans*, forming a myelin sheath up to 100 layers thick.
gray matter
The color difference reflects the distribution of the myelin sheath. The darker-colored areas, or ___, *are made up primarily of cell bodies and dendrites, which are never myelinated, as well as small unmyelinated axons.*
white matter
The color difference reflects the distribution of the myelin sheath. The lighter-colored areas, or ___, are* composed of myelinated axons*.
microglia
The least numerous neuroglial cells are the small and branching ____. *Activate by injury within the brain and become wandering phagocytes*-- cells that "clean up" the environment in the brain.
brain
The mass of nerve tissue that is the *main control center of the nervous system*
axolemma
The* plasma membrane that envelops the axon* is called the ____.
internodes
The* segments of an axon that are covered by neuroglia* are called ___. They range from 0.15 to 1.5mm in length.
axon terminals or synaptic knbobs
The* telodendria terminate* in the _____, that *communicate with a target cell*. Each axon generally splits into 1000 or more ____.
multipolar neurons
These neurons have a *single axon and typically multiple highly branched dendrites*. This group of neurons has the widest variability in terms of shape and size.
ganglia
Within the PNS, *clusters of cell bodies* are called ____.
PNS motor division
__ *consists of motor neurons that carry out the motor functions* of the nervous system
autonomic nervous system
__ *consists of neurons that carry signals primarily to thoracic and abdominal viscera*. It regulates secretion from certain glands, the contractions of smooth muscle, and the contraction of cardiac muscle in the heart.
visceral sensory division
__ *consists of neurons that transmit signals from viscera (organs) such as the heart, lungs, stomach, intestines, kidneys, and urinary bladder.*
neurons
__ are the *excitable cell type responsible for sending and receiving signals* in the form of action potentials.
astrocytes
__ are the *most numerous and the largest of the neuroglia* in the CNS. Functions include- 1) Anchoring neurons and blood vessels in place 2) Regulating the extracellular-environment of the brain 3) Assisting in the formation of the blood-brain barrier 4) Repairing damaged brain tissue
cell body or soma
__ is the most metabolically active part of the neuron, because it is* responsible for maintaining the sometimes huge cytoplasmic volume of the neuron and also for the manufacturing all of the proteins the neuron needs.*
neuroglial cells
__ were named for the early scientific idea that these cells *"glue together" neurons*. We now recognize that they also *maintain the environment around neurons, protecting them, and assisting in their proper functioning. *They retain their ability to divide, and they fill in gaps left when neurons die.
somatic sensory division
___ *consists of neurons that carry signals from skeletal muscles, bones, joints, and skin.* This division also includes special sensory neurons that transmit signals from the official sensory neurons that transmit signals from the organs of vision, hearing, taste, smell, and balance.
satellite cells
___ are flat cells that surround the cell bodies of neurons in the PNS. *They appear to enclose and support the cell bodies, and have intertwined processes that link them with other parts of the neuron*, other ____, and also neighboring schwann cells.
somatic motor division
___ consists of *neurons that transmit signals to skeletal muscles. *This division is sometimes referred to as the voluntary motor division
bipolar neurons
___ has *only two processes:* one axon and one dendrite.
sensory functions
___ involve *gathering information about the internal and external environments of the body.*
integrative functions
____ *analyze and interpret incoming sensory information* and *determine an appropriate response.*
pseudounipolar neurons
____ *begin developmentally as bipolar neurons*, but their* two processes fuse to give rise to a single axon.*
motor functions
____ are the* actions* performed in* response to integration.*
neurofibrils
a *filment in the cytoplasm *of a nerve cell that provides structural support that extends out into the dendrites and axon of the neuron as well.
oligodendrocytes
are fewer in number and smaller than those of astrocytes. The *flattened ends of some of these processes wrap around part of the axons of certain neurons.*
dendrites
are typically short, highly forked processes that resemble the branches of a tree limb.* they receive input form other neurons, which they transmit in the form of electrical impulses toward the cell body. *These DO NOT generate or conduct action potentials.
motor (efferent) division
motor output is performed by __
myelin
oligodendrocytes' wrapped processes form *concentric layers of plasma membrane* that are called ___.
sensory (afferent) division
sensory input is gathered by ____
peripheral nervous system
the *sensory and motor neurons that connect the central nervous system to the rest of the body*
axoplasm
the* axon's cytoplasm* is known as ___.
node of Ranvier
*Between each internode is a gap about 1 um wide* called a _____, or myelin sheath gap, where no myelin is found.
nuclei
*Cell bodies of neurons* are typically found within clusters, most of which are in the CNS, where they are called ___.
axon hillock
*Each axon arises from an area of the cell body *called the ____, and then tapers to form the slender axon, which is often wrapped in the insulating myelin sheath.
spinal cord
*Nerves that run up and down the length of the back* and *transmit most messages between the body and brain*
effectors
*Organs that carry out the effects of the nervous system* are often called ___.
regeneration
*Replacement of damaged tissue with new tissue. *Damaged axons and dendrites in the CNS almost never regenerate.
sensory receptors
*Sensory information is first detected* by structures of the PNS called ___.
slow axonal transport
*Substances within axoplasm, such as cytoskeletal proteins and other types of proteins*, move by ______. These substances* move only away from the cell body *and do so at a rate of about 1-3mm/day.
fast axonal transport
*Vesicles and membrane-bounded organelles use _______ to travel much more rapidly through the axon. *This type of transport *relies on motor proteins in the axoplasm that consume ATP to move substances along microtubules* either toward the cell body, at a maximum rate of about 200 mm/day, or away from the cell body at a maximum rate of about 400 mm/day.
ependymal cells
*Within the brain and spinal cord are fluid-filled cavities lined with ciliated neuroglia* known as ____. *Functions include circulating cerebrospinal fluid, which is the fluid in the cavities of the brain and spinal cord*. ___ also plays a role in the formation of this fluid, and others are thought to monitor its compositions.
axon collaterals
*branches* that typically* arise at right angles to the axon*, called the ____.
motor neurons
*carry information away from their cell bodies* in the CNS *to muscles and glands.*
sensory neurons
*carry information toward the central nervous system. *These *neurons receive information from a sensory receptor and transmit this information to their cell body in the PNS, then down their axon to the brain or spinal cord.*
axon
*process that carries a signal away from the cell body. *The ___ of certain neurons can carry a signal both toward and away from the cell body.
interneurons
*relay messages within the CNS*, primary *between sensory and motor neurons* and are the* location of most information processing.* neuron that transmits impulses between other neurons
nerve
A *cordlike bundle of neuronal axons and/or dendrites and associated connective tissue* coursing together outside the central nervous system
schwann cells
A *glial cell that wraps around the nerve fiber in the peripheral nervous system, and forms the myelin sheaths of peripheral axons.* Additionally, ____ play a role in repair of damaged axons in the PNS.
telodendria
Both the* axon and its collaterals split* near their ends to *produce multiple fine branches* known as ____.
central nervous system
Brain and spinal cord
myelin sheath
Certain *neuroglia wrap themselves around the axons of neurons to create a structure known as the ___. *It is *composed of repeating layers of the plasma membrane of the neuroglial cell*, so it has the same substances in any plasma membrane: phospholipids, other lipids, and proteins.
