Chapter 46: Organization of the Nervous System... Flashcards
T/F: Most neuronal synaptic signal normally passes in the forward direction
T
Most activities of the nervous system are initiated by __________ experiences
Sensory experiences that excite sensory receptors
The most important eventual role of the nervous system is to control:
motor functions of the effectors
These are actual anatomical structures that perform the functions directed by the nerve signals
effectors
Which regions of the CNS are concerned primarily with automatic, instantaneous muscle responses to sensory stimuli?
Lower regions
Which regions of the CNS are concerned with the deliberate complex muscle movements controlled by the thought process of the brain?
Higher regions
This is the channeling and processing of information of the central nervous system
integrative function of the CNS
These determine the directions that the nervous signals will spread through the nervous system
synapses
Where in the nervous system does most storage of information occurs?
cerebral cortex
Each time certain types of sensory signals pass through sequences of synapses, these synapses become more capable of transmitting the same type of signal the next time, a process calle:
facilitation
This is the part of the nervous system for the subconscious control of arterial pressure and respiration
medulla and pons
Control of equilibrium is a combined function of:
older portions of the cerebellum (archicerebellum) and reticular substance of the brainstem
Which major level of the central nervous system initiate wakefulness in the cerebral cortex?
lower brain centers
Information is transmitted in the central nervous system mainly in the form of nerve action potentials, called:
nerve impulse
Most of the synapses used for signal transmission in the central nervous system of the human being are:
chemical synapses
This is the chemical substance secreted by the neuron at its nerve ending synapse
neurotransmitter or transmitter substance
These are clusters of ion channels that allow free movement of ions from the interior of one cell to the interior of the next cell
gap junctions
True or False:
Electrical synapses have bidirectional transmission
True
Which type of synapse that always transmit signals in one direction?
chemical synapse
*principle of one-way conduction
Electron microscopic studies of the presynaptic terminals show that they have varied anatomical forms, but most of them resemble small round or oval knobs and therefore are sometimes called
terminal knobs, boutons, end-feet, synaptic knobs
How wide is a synaptic cleft?
200-300 angstroms
These are the two important internal structures at the synaptic terminal for excitatory and inhibitory functions of the neuron
transmitter vesicles and mitochondria
What protein channels found in the presynaptic membrane opens when an action potential depolarizes the membrane?
voltage-gated calcium channels
To which special proteins in the presynaptic membrane do calcium ions bind causing them to open through the membrane, and allowing a few transmitter vesicles to release their transmitter into the cleft after each single action potential
release sites
What are the two components of receptor proteins in post-synaptic neurons?
Binding component and intracellular component
This is a molecule that protrudes into the cell cytoplasm and activates one or more substances inside the postsynaptic neuron
second messenger
These are neurotransmitter neurons that directly gate ion channels
ionotropic receptors
These are neurotransmitters that act through second messenger systems
metabotropic receptors
Between cation and anion channels, which channel is known to be excitatory?
cation channels (entry of sodium)
Prolonged postsynaptic neuronal excitation or inhibition is achieved by activating a ___________ system inside the postsynaptic neuronal cell, and then it is this that causes the prolonged changes in neurons after the initial transmitter substance is gone
second messenger chemical system
Which component of the G protein in the activator component?
alpha component
What is the most widely used means of excitation of postsynaptic receptors?
Opening of sodium channels to allow large numbers of positive electrical charges to flow to the interior of the postsynaptic cell
What is the most widely used means of excitation of postsynaptic receptors?
Opening of sodium channels to allow large numbers of positive electrical charges to flow to the interior of the postsynaptic cell
What are the 2 groups of chemical synaptic transmitters?
small-molecule, rapidly acting transmitters and
neuropeptides
Which type of chemical synaptic transmitters usually cause more prolonged actions such as long-term changes in numbers of neuronal receptors, long-term opening or closure of certain ion channels, and possibly even long-term changes in numbers of synapses or sizes of synapses?
neuropeptides
Give the Class I small-molecule, rapidly acting transmitter
acetylcholine
Give the Class II small-molecule, rapidly acting transmitters
THE AMINES: norepinephrine epinephrine dopamine serotonin histamine melatonin
Give the Class III small-molecule, rapidly acting transmitters
THE AMINO ACIDS gamma-aminobutyric acid glycine glutamine aspartate
Give the Class IV small-molecule, rapidly acting transmitters
"ANAC" ATP nitric oxide arachidonic acid carbon monoxide
This is the enzyme responsible for the synthesis of acetylcholine from acetyl coenzyme A and choline
choline acetyltransferase
This is the enzyme present in the proteoglycan reticulum that fills the space of the synaptic space between synaptic neurons, and splits the acetylcholine to acetate and choline
cholinesterase
What is the neurotransmitter for the inhibition of the heart via the vagus nerve?
acetylcholine
This is the nucleus of the pons for the physiologic response to stress and panic, and control of overall activity and mood of the mind, such as increasing levels of wakefulness via the neurotransmitter norepinephrine
locus ceruleus [coeruleus]
Where is the main termination of the neurotransmitter dopamine?
striatal region of the basal ganglia
This is the inhibitory neurotransmitter found mainly in the synapses of the spinal cord
glycine
This is the primary inhibitory neurotransmitter of the adult central nervous system
gamma-aminobutyric acid
In the early stages of brain development, including the embryonic period and first week of postnatal life, GABA is thought to serve as an __________ neurotransmitter.
A. inhibitory
B. excitatory
B. excitatory
This excitatory neurotransmitter is secreted by the presynaptic terminals in many of the sensory pathways entering the central nervous system, as well as in many areas of the cerebral cortex.
glutamate
Which part of the brainstem contains the nuclei that secretes serotonin?
median raphe
This neurotransmitter acts as an inhibitor of pain pathways in the cord; an inhibitor action in the higher regions of the nervous system is believed to help control the mood of the person, perhaps even to cause sleep.
Serotonin
This is the neurotransmitter produced by nerve terminals in areas of the brain responsible for long-term behavior and memory.
Nitric oxide
This neurotransmitter is not preformed and stored in vesicles in the presynaptic terminal, as are other transmitters. Instead, it is synthesized almost instantly as needed and then diffuses out of the presynaptic terminals over a period of seconds rather than being released in vesicular packets.
nitric oxide
Where are neuropeptides synthesized compared to the small-molecule, rapidly acting transmitters that are synthesized in the cytosol?
The neuropeptides are not synthesized in the cytosol of the presynaptic terminals. Instead, they are synthesized as integral parts of large-protein molecules by ribosomes in the neuronal cell body
How are neuropeptide transmitter vesicles transported from the cell body all the way to the tips of the nerve fibers?
axonal streaming
traveling at the slow rate of only a few centimeters per day
Which type of synaptic transmitters are contained in vesicles that are autolyzed and not utilized after secretion?
neuropeptides
This is the type of secretion of Neuropeptide and Small-Molecule Transmitters coexisting in the Same Neurons wherein both transmitters are stored in the same set of synaptic vesicles and released together when an action potential reaches the presynaptic terminal.
co-release
This is the type of secretion of Neuropeptide and Small-Molecule Transmitters coexisting in the Same Neurons wherein the transmitters are stored in different populations of synaptic vesicles with differential release mediated by different calcium ion (Ca2+) sensitivities, or contained in spatially segregated vesicle populations to different boutons, allowing uniform information to be transmitted to different postsynaptic targets
co-transmission
may be:
- differential Ca2+ sensitivity
- spatial segregation
Which neurotransmitters are co-released from the raphe nucleus of the brainstem, and play an important role in the cycle of sleep and wakefulness?
serotonin and glutamate
These are the 3 ions that are most important for neuronal function
sodium ions
potassium ions
chloride ions
This is the positive increase in voltage above the normal resting neuronal potential of the neuronal cell membrane eliciting an action potential in the postsynaptic neuron, thus exciting it in cases of +20 mV.
excitatory postsynaptic potential
This is the process of simultaneous discharge of many nerve terminals at the same time or rapid succession
summation
This is the segment of the axon where action potential is generated due to the seven times greater concentration of voltage-gated sodium channels in the membrane.
initial segment of the axon
**other sources: Axon Initial Segment (AIS)
What is the threshold for excitation of the neuron?
-45mV
This refers to an increase in negativity beyond the normal resting membrane potential level
inhibitory postsynaptic potential
What neurotransmitter causes the opening of anion channels in the presynaptic neurons, allowing large numbers of chloride ions to diffuse into the terminal fibril, thus inhibiting the presynaptic neuron
gamma-aminobutyric acid
This is the effect of summing simultaneous postsynaptic potentials by activating multiple terminals on widely spaced areas of the neuronal membrane
spatial summation
When the EPSP becomes great enough, the ______ will be reached
threshold for firing
Successive discharges from a single presynaptic terminal, if they occur rapidly enough, can add to one another; that is, they can summate. This type of summation is called:
temporal summation
Often, the summated postsynaptic potential is excitatory but has not risen high enough to reach the threshold for firing by the postsynaptic neuron. When this situation occurs, the neuron is said to be _________
facilitated
How can dendrites transmit signals within the same neuron?
electrotonic conduction
This is the decrease in membrane potential as it spreads electrotonically along dendrites toward the soma
decremental conduction
This is the summated degree of excitatory drive to the neuron
excitatory state
The phenomenon of progressively decreasing number of discharges by the postsynaptic neuron in succeeding repetitive stimulation at rapid rate.
fatigue of synaptic transmission
This is a protective mechanism against excess neuronal activity, and the most important means whereby the excess excitability of the brain during an epileptic seizure is finally subdued so that the seizure ceases
fatigue [of synaptic transmission]
Part of the fatigue process of synaptic transmission probably results from two other factors apart from the exhaustion of stores of transmitters, and these are:
(1) progressive inactivation of many postsynaptic receptors
(2) slow development of abnormal concentration of ions in the postsynaptic neuronal cell
Hyperventilation is most likely to have which of the following effects on a typical neuron in the central nervous system?
increased neuronal excitability
- hyperventilation causes alkalosis which greatly increases neuronal excitability
Cessation of oxygen for only a few seconds can cause _____________ of some neurons
complete inexcitability
This is one of the best known of all agents that increase excitability of neurons. However, it does not do this by reducing the threshold for excitation of the neurons; instead, it inhibits the action of some normally inhibitory transmitter substances, especially the inhibitory effect of GLYCINE in the spinal cord. Therefore, the effects of the excitatory transmitters become overwhelming, and the neurons become so excited that they go into rapidly repetitive discharge, resulting in severe tonic muscle spasms.
strychnine
The minimal period of time required for the events of neuronal signal transmission to take place, even when large numbers of excitatory synapses are stimulated simultaneously, is about 0.5 millisecond, called the
synaptic delay
Equilibrium potential of sodium
+62 mV
Equilibrium potential of potassium
-86 mV
Equilibrium potential of chloride
-70 mV
