A&P Ch 11 Fundamentals of the Nervous System and Nervous Tissue Flashcards

Terms Definitions
parts of the central nervous system
brain and spinal cord
function of the central nervous system
integration and command center
parts of the peripheral nervous system
paired spinal and cranial nerves
function of the peripheral nervous system
carries messages to and from the spinal cord and brain
what do the sensory afferent fibers and visceral afferent fibers of the sensory division of the peripheral nervous system do?
sensory afferent fibers carry impulses from skin, skeletal muscles, and joints to the brainvisceral afferent fibers transmit impulses from visceral organs to the brain
what does the motor division of the peripheral nervous system do?
transmits impulses from the CNS to effector organs
two parts of the motor (efferent) division
somatic nervous system autonomic nervous system
somatic nervous system
conscious control of skeletal muscles
autonomic nervous system
regulates smooth muscle, cardiac muscle and glands
what are the two divisions of the autonomic nervous system?
sympathetic and parasympathetic
two principal cell types of the nervous system
neuronssupporting cells
excitable cells that transmit electrical signals
supporting cells
cells that surround and wrap neurons
functions of the supporting cells (neuroglia or gilal cells)
provide a supportive scaffolding for neuronssegregate and insulate neuronsguide young neurons to the proper connectionspromote health and growth
most abundant, versatile and highly branched glial cells
functions of astrocytes
support and brace neuronsanchor neurons to their nutrient suppliesbuide migration of young neurons control the chemical environment
where are astrocytes?
they cling to neurons and their synaptic endings, and cover capillaries
small, ovoid cells with spiny processes
function of microglia
phagocytes that monitor the health of neurons
what are the different types of neuroglia or glial cells?
astrocytesmicrogliaependymal cells oligodendrocytesschwann cellssatellite cells
ependymal cells
range in shape from squamous to columnarthey line the central cavities of the brain and spinal column
branched cells that wrap CS nerve fibers
schwann cells (neurolemmocytes)
surround fibers of the PNS
satellite cells
surround neuron cell bodies with ganglia
what are the parts of a neuron?
body axondendrites
describe the soma or body of a neuron
contains the nucleus and a nucleolusmajor biosynthetic centerfocal point for the outgrowth of neruonal processeshas no centrioles - hence its amitotic nature has well-developed nissl bodies (Rough ER)contains an axon hillock - cone-shaped area from which axons arise
armlike extensions from the soma called tracts in the CNA and nerves in the PNS
what are the two types of processes
axons and dendrites
dendrites of motor neurons
short, tapering and diffusely branched processes
function of dendrites
receptive, or input regions of the neruonelectrical signals are conveyed as graded potentials not action potentials
structure of axons
slender processes of uniform diameter arising from the hillocklong axons are called nerve fibersusually only one unbranched axon per neruonrare branches, if present are called axon collaterals
axonal terminal
branched terminus of an axon
function of axons
generate and transmit action potentials secrete neurotransmitters from the axonal terminals
how does movement along axons occur?
anterograde - toward axonal terminal retrograde-away from axonal terminal
myelin sheath
whitish, fatty (protein-lipoid) segmented sheath around most long axons
function of myelin sheath
protect the axon electrically insulate fibers from one anotherincrease the speed of nerve impulse transmission
white matter
dense collections of myelinated fibers
gray matter
mostly soma and unmyelinated fibers
action potentials or nerve impulses
electrical impulses carried along the length of axons always the same regardless of stimulusunderlying functional feature of the nervous system
when is there a potential on either side of membranes?
when the number of ions is different across the membrane or when the membrane provides a resistance to ion flow
what happens during action potential depolarization
Na+ permeability increases- membrane potential reversesNa+gates are opened and K+ gates are closed
what happens during the repolarization phase of action potentials?
sodium inactivation gates close membrane permeability to Na+ declines to resting levelsas sodium gates close, voltage-0 sensitive K+ gates open K+ exits the cell and internal negativity of the resting neuron is restored
what is the function of re polarization?
restores the resting electrical conditions of the neuron
absolute refractory period
time from the opening of the Na+ activation gates until the closing of the inactivation gates
function of the refractory period
prevent the neuron from generating an action potentialensure that each action potential is separateenforces one-way transmission of nerve impulses
relative refractory period
the interval following the absolute refractory period when sodium gates are closed, potassium gates are open and repolarization is occuring
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