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CNS is composed of what?
Brain and spinal chord
what are the three functions of the nervous system
sensory input, intergration, motor input
nerve cells travel fastest in:
large myelinated fibers
central nervous system contains what
Brain and spinal cord. Intergration and command center
peripheral nervous system does/contains what
paired spinal and cranial nerves. carries messages to and from the spinal cord and brain
what are the two PNS functional divisions
sensory (afferent) sensory afferent fibers carry impulses from skin, skeletal muscles, and joints to the brain.
Motor (efferent) transmits impulses from the CNS to effector organs
what are the two motor division parts
somatic nervous sytem: conscious control of skeletal muscles , somatic motor efferent fibers
autonomic nervous system: visceral (autonomic) motor efferent fibers. regulates smooth muscle, cardiac muscle and glands. divisions are sympathetic and parasympathetic
what are the two principal cell types of the nervous system
neurons- excitable cells that transmit electrical signals
supporting cells- cells that surround and wrap neurons
what do supporting cells (neuroglia cells) do
provide a supportive scaffolding for neurons, segregate and insulate neurons, guide young neurons to the proper connections, promote health and growth.
how many supporting cells are in CNS and PNS
four in CNS: astrocytes, microglia, ependymal, oligodendrocytes
two in pns: schwann cells, satalite cells
Describe astrocytes
most abundant, versatile, and highly branched glial cells.
help form blood brain barriers
guide young neurons
describe microglia cells
small, ovoid cells with spiny processes. phagocytes that monitor the health of neurons
describe ependymal
range in shape from squamous to columnar. they line the central cavities of the brain and spinal column( blood brain barrier)
describe oligodendrocytes
branched cells that wrap CNS nerve fibers (myelinate)
describe Schwann cells
surround fibers of the PNS (myelinate)
Describe satellite cells
surround neuron cell bodies with ganglia
describe neurons (nerve cells)
structural units of the nervous system. composed of a body, axon, and dendrites
their plasma membrane functions in: electrical signaling, and cell-to-cell signaling during development
describe a nerve cell body
contains the nucleus and a nucleolus
has no centrioles
has well developed Nissl bodies
contains axon hillock- cone shaped area from which axons arise
clusters of neuron cell bodies are called what
nuclei in the CNS
Ganglia in the PNS
what are processes
armlike extensions from the soma
called tracts in the CNS and nerves in the PNS
there are two types: axons and dendrites
describe dendrites of motor neurons
short, tapering, and diffusely branched processes
they are receptive, or input, regions of the neuron- carry info to the soma
electrical signals are conveyed as graded potentials
describe “axons” structure
slender process of uniform diameter arising from the hillock
long axons are called nerve fibers
describe axon functions
generate and transmit action potentials (conducting component)
secrete neurotransmitters from the axonal terminals at the end of terminal branches
movement along axons occur in what two ways
anterograde- toward axonal termanal
retrograde- away from axonal terminal (recycling)
describe a myelin sheath
whitish, fatty, segmented sheath around most long axons
what are myelin sheath functions
protect axons
electrically insulate fibers from one another
increase speed of the nerve impulse transmission
what is ‘‘white'‘ and “gray” matter in the regions of the brain and spinal cord
white matter- dense collections of myelinated fibers
gray matter- mostly soma and unmyellinated fibers
what are the three neuron classifications (structural)
multipolar- three or more processes, most common major type of CNS
bipolar- two process (axon and dendrite)
unipolar- single process, sensory in PNS
unipolar neurons are more accurately called
pseudounipolar
what are the three “functional” neuron classifications
sensory (afferent)- transmit impulses toward the CNS
motor (efferent)- carry impulses away from the CNS
interneurons (association neurons)- shuttle signals through CNS pathways
neurons are highly irritable -True/False
True
action potentials, or nerve impulses are:
electrical impulses carried along the length of axons
the underlying functional feature of the nervous system
nerve fibers are classified according to:
describe a synapse
a junction that mediates information transfer from one neuron:
-to another neuron
-to an effector
types of synapses
axodendritic- synapses between the axon of one neuron and the dendrite of another
axosomatic- synapses between
describe electrical synapses
are less common than chemical synapses
correspond to gap junctions found in other cell types
are important in the CNS- arousal from sleep, mental attention
describe chemical synapses
specialized for the release of reception of neurotransmitters
chemical synapses are composed of what two parts
axonal terminal of the presynaptic neuron
receptor region on the dendrites or soma of the postsynaptic neuron
describe a synaptic cleft
fluid filled space seperating the presynaptic and postsynaptic neurons
prevent nerve impulses from directly passing from one neuron to the next
one role of the astrocyte is to:
help form the blood brain barrier
what lines the ventricles in the brain
astrocytes
oligodendrocytes are only found in :
CNS
interneurons are only found in:
CNS
the visceral motor division is further divided into:
sympathetic and parasympathetic divisions
satellite cells are only found in:
PNS
a bipolar neuron has:
one axon and one dendrite arising from the soma
the majority of neurons are
multipolar
which cells form the myelin sheath in the CNS
oligodendrocytes
what is the neurolemma
the outermost layer of a schwann cell
which structures are found only in the PNS
nerves