CNS Flashcards
three basic functions of the NS
- Relays information
- Motor functions
- Integrates thought processes, learning, and memory
two fundamental divisions
CNS and PNS
- Composed of 2 organs: brain and spinal cord
CNS
- Control center
- processes and analyzes information received from the sensory receptors
- issues motor commands to control body functions
CNS
Six Primary Areas of the Brain
- cerebrum
- diencephalon
- midbrain
- pons
- cerebellum
- medulla oblongata
Contains 2 forms of nerves: afferent and efferent
PNS
relay sensory information to the CNS
Afferent nerves
relay motor commands to the various muscles and glands
Efferent nerves
Efferent nerves are organized into two systems:
Somatic and autonomic NS
- also known as the voluntary nervous system
- carries motor information to the skeletal muscles
somatic ns
- Carries motor information to the smooth muscles (e.g. cardiac muscles) and other various glands (e.g. gastric system)
- These are the things that happen without effort coming from the brain. The major difference between these 2 systems pertains to conscious control
- Can be classified as sympathetic or parasympathetic
autonomic ns
2 categories of cells found in the nervous system
neurons and glial cells (neuroglia)
are the functional nerve cells directly responsible for transmission of information to and from the CNS to other areas of the body and vice versa
neurons
provide support to the neural tissue, regulate the environment around the neurons, and protect against foreign invaders
Glial cells (also known as neuroglia)
- communicate with all areas of the body and are present within both the CNS and PNS
- They serve to transmit rapid impulses to and from the brain and spinal cord to virtually all tissues and organs of the body
- They are an essential cell and their damage or death can have critical effects on body function and survival
neurons
When neurons die, they are not replaced (t or f)
T
As neurons are lost, so are certain neural functions such as:
memory, ability to think, quick reactions, coordination,
muscular strength, sight,
hearing, and taste
If the neuron loss or impairment is substantial, severe and permanent disorders can occur, such as
blindness, paralysis, and death
Neurons consist of a _______
cell body
2 types of extensions of the neuron
axons and dendrites
- may extend to long distances (over a meter
in some cases); usually transmit information from
one part of the body to another
axons
specialized in receiving incoming information and sending to the neuronal cell body with transmission or electrical charge down the
axon to one or more junctions with other neurons or muscle cells, also known as synapse
dendrites
intracellular space between 2 neurons
synapse
- covers axon
- insulating fatty layer that can speed up transmission
of electrical signals or even the neurotransmitters - Multilayer coating that wraps the axon and help
insulate the axons from surrounding tissue or fluids - Prevent the electrical charge or stimulus from
escaping the axon. - Guides the electrical impulses
myelin sheath
common parts that toxicants would attack:
nucleus, cell body, axons, myelin sheath, the transmission of neurotransmitters
____________ status of the nervous system with the maintenance of a biochemical barrier between the ____ and the _____
(7 generalities)
privileged; brain and the blood
importance of ____________ requirements of the brain
(7 generalities)
high energy
_________ of the nervous system as long cellular process and the requirements of cells with such a complex geometry
(7 generalities)
spatial extensions
maintenance of an environment rich in ______
(7 generalities)
lipids
transmission of information across ________ at the _________
(7 generalities)
extracellular space; synapse
distance over which ____________ must be transmitted, coordinated, and integrated
(7 generalities)
electrical impulses
development of ___________ pattern of the nervous system
(7 generalities)
regenerative
The nervous system is protected from the adverse effects of many potential toxicants by an anatomical barrier between the blood and the brain called
blood-brain barrier (BBB)
Most of the brain, spinal cord, retina, and PNS maintain this barrier with blood, this is not similar to the interface between cells and the extracellular space (t or f)
(BLOOD-BRAIN BARRIER)
F
To gain entry to the nervous system, molecules must pass into the _________________ of endothelial cells of the brain rather than between endothelial cells, as they do in other tissue
(BLOOD-BRAIN BARRIER)
cell membranes
The principal basis of the BBB ___________ cells in the brain’s ___________ aided by
interactions with ____
(BLOOD-BRAIN BARRIER)
specialized endothelial; microvasculature; glia
brain, spinal cord, and peripheral nerves are not completely covered with continuous lining of specialized cells
that limits the entry of molecules from adjacent tissues (t or f)
(BLOOD-BRAIN BARRIER)
F
In the brain and spinal cord (surface of specialized cells)
(BLOOD-BRAIN BARRIER)
meningeal surface
in the peripheral nerves, each _______ of nerve is surrounded by
_________
(BLOOD-BRAIN BARRIER)
fascicle; perineural cells
Among the unique properties of the endothelial cells in the nervous system is the presence of ______________ between cells
(BLOOD-BRAIN BARRIER)
tight junctions
The BBB also contains ______________ that transport some xenobiotics that have diffused through the endothelial cells back into the blood
(BLOOD-BRAIN BARRIER)
xenobiotic transporters
If not actively transported into the brain, the penetration of toxicants or their metabolites is largely related to their _____________ and to their ability to pass through the plasma
membrane of a cell, forming now the barrier
(BLOOD-BRAIN BARRIER)
lipid solubility
If the drug is _______, it can usually pass through
the BBB if it does not avail the active transport
(BLOOD-BRAIN BARRIER)
lipophilic
Sites within the brain that are not protected by the blood-tissue barrier
This discontinuity of the barrier is the basis for
______________ of some compounds
(BLOOD-BRAIN BARRIER)
Spinal ganglia, autonomic ganglia, and a small number of other sites
selective neurotoxicity
The BBB is completely developed at birth and even more so in premature infants. (t or f)
(BLOOD-BRAIN BARRIER)
F
Neurons are highly dependent on _____________ - maintain proper ion gradients
(ENERGY REQUIREMENTS)
aerobic metabolism
The brain is extremely sensitive to even brief interruptions in the supply of _______ or _______
(ENERGY REQUIREMENTS)
oxygen or glucose
exposure to chemicals or toxicants that exhibit
aerobic respiration such as _________or _______ can lead to early signs of neuronal dysfunction
(ENERGY REQUIREMENTS)
Cyanide or CO poisoning
Damage to the nervous system is a combination of ___________ on neurons and secondary damage from systemic ________ or _________
(ENERGY REQUIREMENTS)
direct toxic effects; hypoxia or ischemia
Impulses are conducted over great distance at a rapid speed, providing information about the environment to the organism in a coordinated manner that allows an organized response to be
carried out at a specific site (t or f)
(AXONAL TRANSPORT)
T
2 immediate demands placed on the neurons
(AXONAL TRANSPORT)
- maintenance of a much larger cellular volume, requiring more protein synthesis
- transport of intracellular materials over great distances using various mechanisms
neuronal demands require ATP (t or f)
(AXONAL TRANSPORT)
T
moves protein products from the cell body to
the appropriate site in the axon
(AXONAL TRANSPORT)
Axonal transport
Many proteins associated with vesicles migrate through the axon at a rate of ________
(AXONAL TRANSPORT)
400 mm/day
This process is dependent on microtubule-associated ___________ and the microtubule-associated motor proteins (____________) that provide both the mechanochemical
force in the form of a microtubule-associated ATPase and the
interface between microtubules as the track and vesicles as the cargo
(AXONAL TRANSPORT)
ATPase activity; kinesin and dynein
Vesicles are transported rapidly in an ___________ by kinesin, and they are transported in a ___________ by dynein
(AXONAL TRANSPORT)
anterograde direction; retrograde direction
The transport of some organelles, including , ___________ constitutes an intermediate component of axonal transport, moving at __________
(AXONAL TRANSPORT)
mitochondria; 50 mm/day
The slowest component of axonal transport represents the movement of the ______________
(AXONAL TRANSPORT)
cytoskeleton itself
is composed of microtubules formed by the association of tubulin subunits and neurofilaments formed by
the association of three neurofilament protein subunits
(AXONAL TRANSPORT)
cytoskeleton
_________and _________ move at a rate of approximately _________ and make up the majority of ____, which is the slowest moving component of axonal transport
(AXONAL TRANSPORT)
Neurofilaments and microtubules; 1 mm/day; SCa
The slowest moving component of axonal transport
(AXONAL TRANSPORT)
SCa
Moving at only a slightly more rapid rate of 2 to 4 mm/day in an anterograde direction is ______, which is composed of many
proteins
(AXONAL TRANSPORT)
SCb
Included in SCb are several structural proteins, such as the component of microfilaments (______) and several microfilament-associated proteins (____________), as
well as ______ and many soluble proteins
(AXONAL TRANSPORT)
actin; M2 protein and fodrin; clathrin
This continual transport of proteins from the cell body through the various components of ____________ transport is the
mechanism through which the neuron provides the distal axon with its complement of functional and structural proteins
(AXONAL TRANSPORT)
anterograde axonal
Some vesicles are also moving in a ___________ and undoubtedly provide the cell body with information concerning the status of the distal axon
(AXONAL TRANSPORT)
retrograde direction
toxicant-induced irreversible loss of neurons, including its cytoplasmic extensions, dendrites, axons, and the myelin ensheathing the axon
(AXONAL DEGENERATION)
neuronopathy
when the neuronal cell body has been lethally injured and it degenerates
(AXONAL DEGENERATION)
neuronopathy
This is characterized by the loss of the cell body and
all of its processes, with no potential for regeneration
(AXONAL DEGENERATION)
neuronopathy
when the injury is at the level of the axon, the axon
may degenerate while the neuronal cell body
continues to survive
(AXONAL DEGENERATION)
Axonopathy
there is a potential for regeneration and recovery
from the toxic injury as the axonal stump sprouts
and regenerates
(AXONAL DEGENERATION)
Axonopathy
The result of axotomy (transection of an axon) is that the distal axon is destined to degenerate, a process known as axonal degeneration, which is unique to the NS (t or f)
(AXONAL DEGENERATION)
T
The cell body of the neuron responds to the axotomy as well and undergoes a process of _________
(AXONAL DEGENERATION)
chromatolysis
The sequence of events that occurs in the distal stump of an axon following transection is referred to as __________
(AXONAL DEGENERATION)
Wallerian degeneration
Because the axonal degeneration associated
with chemicals and some disease states is thought to occur through a similar sequence of events, it is often referred to as
________________
(AXONAL DEGENERATION)
Wallerian-like axonal degeneration
Following axotomy, there is degeneration of the distal nerve stump, followed by generation of a microenvironment
supportive of ____________ and involving the distal axon, ensheathing glial cells and the blood nerve barrier
(AXONAL DEGENERATION)
regeneration
Initially there is a period during which the distal stump survives and maintains relatively normal structural, transport, and conduction properties (t or f)
(AXONAL DEGENERATION)
T
The duration of survival is inverse to the length of the axonal stump, and this relationship appears to be maintained across species
(AXONAL DEGENERATION)
F (proportional)
Terminating the period of survival is an __________ that digests the axolemma and axoplasm, leaving only a myelin sheath surrounding a swollen degenerate axon
(AXONAL DEGENERATION)
active proteolysis
Digestion of the axon appears to be an allornone event effected through ___________ proteases that are activated through increased levels of intracellular free ______
(AXONAL DEGENERATION)
endogenous; Ca2+
In the PNS, __________ respond to loss of axons by
decreasing synthesis of ________, down-regulating genes encoding _____________, and dedifferentiating to a
_________ mitotic Schwann cell phenotype
(AXONAL DEGENERATION)
Schwann cells; myelin lipids; myelin proteins; premyelinating
The proliferating Schwann cells create a tubular structure around the axon (referred to as a band of ______), providing
physical guidance for regenerating axons
(AXONAL DEGENERATION)
Bungner
These tubes also provide trophic support from __________, _________, __________, and corresponding receptors produced by the
associated Schwann cells
(AXONAL DEGENERATION)
- nerve growth factor (NGF)
- brain-derived neurotrophic factor
- insulin-like growth factor
Resident ___________ distributed along the endothelium within the endoneurium and the denervated Schwann cells assist in clearing ___________, but the recruitment of hematogenous macrophages accounts for the removal of the
_________ of myelin
(AXONAL DEGENERATION)
macrophages; myelin debris; majority
Another essential role of recruited, circulating macrophages is the production of _____________, which is responsible for
stimulating production of __________ by Schwann cells
(AXONAL DEGENERATION)
interleukin1 (IL1); NGF
A critical difference exists between axonal degeneration in the CNS compared with that in the PNS:
(AXONAL DEGENERATION)
peripheral axons can regenerate, whereas central axons cannot
Main factors contributing to the inability of the CNS to
regenerate include inhibitory factors secreted by ________
(AXONAL DEGENERATION)
oligodendrocytes, astrocyte scarring, and glial interference
Interestingly, experiments involving cellular transplants of Schwann cells to the CNS or CNS neurons to the PNS show that the regenerative capability of CNS neurons depends on both
_____________ and the _____________
(AXONAL DEGENERATION)
the microenvironment; properties of mature neurons
________________ was long thought to be a________
process that proceeded inexorably after separating the axon from the trophic support provided by the cell body
(AXONAL DEGENERATION)
Wallerian degeneration; passive
However, we now know from several lines of evidence that Wallerian degeneration is an ___________ mediated by the axon itself, and that it is possible to ____________ its progression
(AXONAL DEGENERATION)
active process; slow or even halt
Myelin is formed in the CNS by _____________ and in the PNS by ______________
(MYELIN FORMATION AND MAINTENANCE)
oligodendrocytes; Schwann cells
Both of these cell types form concentric layers of __________ by the progressive wrapping of their cytoplasmic processes around the axon in successive loops
(MYELIN FORMATION AND MAINTENANCE)
lipid-rich myelin
These cells exclude _________ from the inner surface of their membranes to form the major dense line of myelin
(MYELIN FORMATION AND MAINTENANCE)
cytoplasm
Some toxic compounds interfere with this complex process of the maintenance of myelin and result in the toxic _____________
(MYELIN FORMATION AND MAINTENANCE)
“myelinopathies”
In general, the loss of myelin with the preservation of axons is referred to as ____________
(MYELIN FORMATION AND MAINTENANCE)
demyelination
Intercellular communication is achieved in the NS through the synapse
(NEUROTRANSMISSION)
neurotransmission
Neurotransmitters released from one neuron act as the __________
(NEUROTRANSMISSION)
first messenger
Binding of the transmitter to the postsynaptic receptor is
followed by _________ of an ion channel or __________ of a second-messenger system, leading to changes in the responding cell
(NEUROTRANSMISSION)
modulation; activation
Various therapeutic drugs and toxic compounds impact the process of neurotransmission. (t or f)
(NEUROTRANSMISSION)
T
expresses itself in terms of altered conduction
and propagation of nerve impulses and changes in functions such as behavior, performance, and conditioning
(NEUROTRANSMISSION)
Neurotoxicity
In terms of toxicity, many side effects of neurological drugs may be viewed as short-term interactions that are reversible with time or that may be counteracted by the use of appropriate antagonists (t or f)
(NEUROTRANSMISSION)
T
Excessive stimulation of neurotransmitter systems may also have long-term consequences; e.g., ____________ (e.g.,
glutamate) produces ________ that is manifest as CNS diseases and nerve cell death.
(NEUROTRANSMISSION)
excitatory system; excitotoxicity
The NS begins development during ________ and continues through _________
(DEVELOPMENT OF THE NS)
gestation; adolescence
are the basic processes that
underlie development of the NS, and these occur in a tightly choreographed sequence that depends on the region, cell type, and neurotrophic signals
(DEVELOPMENT OF THE NS)
- proliferation
- migration
- differentiation
- synaptogenesis
- apoptosis
- myelination
______________ occur in waves that are specific for brain regions, but in general, the brain develops in a caudal to rostral direction (with ___________ development being a notable exception)
(DEVELOPMENT OF THE NS)
proliferation and migration; cerebellar