Anatomy_Key Terms_Ch12 Flashcards
sensory input
the nervous system uses its milliosn of sensory receptors to monitor changes occurring both inside and outside the body. each of these changes is called a stimulus, and the gathered information is called _
intergration
the nervous system processes and interprets the sensory input and makes decisions about what sohuld be done at each moment, a process called _
motor output
the nervous system dictates a response by activating the effector organs, our muscles or glands; the response is called _
central nervous system
consists of the brain and the spinal cord, which occupy the cranium and the vertebral canal respectively. the CNS is the integrating and comman center of the nervous system: it receives incoming sensory signals, interprets these signals, and dictates motor responses based on past experiences, reflexes, and current conditions
peripheral nervous system (PNS)
the part of the nervous sytem outside the CNS, consists mainly of the nerves that extend from the brain and spinal cord
ganglia
areas where the cell bodies of neurons are clustered
sonsory/afferent division
signals are picked up by sensory receptors located throughout the body and carrie by nerve fibers of the PNS into the CNS
motor/efferent division
signals are carried away from the CNS by nerve fibers of the PNS to innervate the muscles and glands, causing these organs either to contract or to secrete
somatic sensory
the sensory innervation of the outer tube: skin, body wall, and limbs
visceral sensory
the sensory innervation of the viscera
somatic motor
or voluntary motor, the motor innervation of the outer tube, specifically skeletal muscles
visceral motor
aka autonomic nervous system (ANS), the involuntary motor innervation of the inner tube, specifically soomth muscle, cardiac muscle, and glands, as well as some outer tube structuers: arrector pili muscles, smooth muscle in the vessels, and sweat glands
general somatic senses
sense whose receptors are spread widely throughout the outer tube of the body
proprioception
”"”sensing one’s own body””, a sense that detects the amount of ste]retch in muscles, tendons, and joint capsules”
special somatic senses
somatic senses whose receptors are confined to relatively small areas rather than spread widely throughout the body
equilibrium
balance, using receptors in the inner ear, a special sense
general visceral senses
incledue stretch, pain, and temperature, which can be felt widely in the digestive and urinary tracts, reproductive organs, and other viscera
special visceral senses
taste and smell, aka chemical sense, have their sensory receptors localized to the tongue and nasal cavity
nervous tissue parts
neurons, the excitable nerve cells that transmit electrical signals<br></br>neuroglia, nonexcitable supporting cells that surround and wrap the neurons
neurons/nerve cells
basic strutural units of the nervous system
neurilemma
plasma membrane (for nerve cells)
nerve impulses
aka action potenials, a reversal of electrical charge that travels rapidly along the neuronal membrane
neurons have a number of special functional characteristics
neurons are highly specialized cells that conduct electrical signals from one part of the body to another. these signals are transmitted along the plasma membrane, or neurilemma, in the form of nerve impulses, or action potentials. basically, an impulse is a reversal of electrical charge that tranels rapidly along the neuronal membrane<br></br>neurons have extreme longevity. they can live and function for a lifetime, over 100 years<br></br>neurons do not divide. as the fetal neurons assume their roles as communication links in the nervous system, they lose their ability to undergo mitosis. there can be a high price for this characteristic of neurons, for they cannot replace themselves if destroyed. there are some exceptions to this rule; neural stem cells have been identified in certain areas of the CNS<br></br>neurons have an exceptionally high metabolic rate, requiring continuous and abundant supplies of oxygen and glucose. neurons cannot survive for more than a few minutes without oxygen
cell body (neuron)
all consist of a single nucleus surrounded by cytoplasm
chromatophilic substance
large clusters of rough endoplasmic reticulum and free ribosomes that stain darkly with basic dyes
neurofibrils
bundles of intermediate filaments (neurofilaments) that run in a network between the chromatophilic substance
processes (neuron)
extend from the cell bodies; of two types, dentrites and axons
axon hillock
cone-shaped region of the cell body from which arises the axon
nerve fiber
any long axon
axon collaterals
occasional branches along the length of an axon
terminal arborization
end of the axon where it usually branches profusely
presynaptic neuron
neuron that conducts signals toward a synapse
postsynaptic neuron
neuron that transmits signals away from the synapse
axodendritic synapses
most synapses (called _) occur between the terminal boutons of one neuron and the dentrites of another neuron
axosomatic synapses
many synapses occur between axons and neuron cell bodies
synaptic vesicles
membrane-bound sacs filled with neurotransmitters, the molecules that transmit signals across the synapse
multipolar neurons
have more than two processes, nearly all in the body, usually have numerous dendrites and a single axon
bipolar neurons
have two processes that extend from opposite sides of the cell body, mostly serve as sensory neurons
unipolar neurons
have a short, single process that emerges from the cell body and divides like an inverted T into two long branches, generally start as bipolar neurons whose processes fuse together during development, aka pseudounipolar neurons
central process
one branch of the single process of a unipolar neuron, runs centrally into the CNS
peripheral process
one branch of the single process of the unipolar neuron, extends peripherally to the receptors
sensory neurons
aka afferent neurons, make up the sensory division of the PNS, transmit impulses toward the CNS from sensory receptors in the PNS, most are pseudounipolar
interneurons
lie between motor and sensory neurons, confined entirely to the CNS, link together into chans that form complex neuronal pathways, make up 99.98% of the neurons of the body
astrocytes
”"”star cells””, most abundant glial cells of the CNS, regulate neurotransmitter levels by increasing the rate of neurotransmitter uptake in regions of high neuronal activity, signal increased blood flow through capillaries in active regions of the brain, control the ionic environment around neurons”
microglial cells
smalles and lest abundant neuroglia of the CNS, phagocytes, the macrophages of the CNS
ependymal cells
”"”wrapping garment””, form a simple epithelium that lines the central cavity of the spinal cord and brain, provide a fairly permeable layer between tho cerebrospinal fluid that fills this cavity and tissue fluid that bathes the cells of the CNS, bear cilia that help circulate the cerbrospinal fluid”
obigondendrocytes
”"”few-branch cells””, line up in small groups and wrape their cell precess around the thicker axons in the CNS producing insulating coverings called myelin sheaths”
satellite cells
surround neuron cell bodies within ganglia
Schwann cells
surround all axons in the PNS and form myelin sheaths around many of these axons
myelin sheaths
produced by oligodendrocytes in the CNS and Schwann cells in the PNS, segmented structures that are composed of the lipoprotein myelin and surround the thicker axons of the body
myelin
lipoprotein that makes up myelin sheaths
myelin sheath gaps
aka nodes of Ranvier, occur at regular intervals about 1 mm apart; in myelinated axons, nerve impulses do not travel along the myelin-covered regions of the axonal membrane but instead jump from the membrane of one myelin sheath gap to the next in a way that greatly speeds impulse conduction
nonmyelinated axons
thin, slowly conducting axons lack a myelin sheath
gray matter
gray-collored zone that surrounds the hollow central cavity of the CNS; the site where neuron cell bodies are clustered; more specifically, the gray matter of the CNS is a mixture of neuron cell bodies, dendrites, short, nonmyelinated neurons, and neuroglia; synapes occur in the gray matter
white matter
contains no neuron cell bodies but millions of axons and neuroglia; consists of axons running between different parts of the CNS
tracts
within white matter, axons, traveling to similar destinations form axon bundles
cortex
in two regions of the brain (the cerebrum and cerebellum) there is an additional layer of gray matter located superficially, the _
nerve
cablelike organ in the peripheral nervous system, each consists of many axoins arranged in parallel bundles and enclosed by successive wrappings of connective tissue
endoneurium
a delicate layer of loose connective tissue covering the Schwann cells
fascicles
groups of axons bound into bundles called nerve _ by a wrapping of connective tissue called the perneurium
perineurium
wrapping of connective tissue that surrounds the nerve fascicles
