Organization Of The NS

Question 1

Incoming signals

enter this neuron through synapses located mostly on the

Answer 1

neuronal dendrites, but also on the cell body.

Question 2

output signal travels by way of
several axon leaving the neuron.
True or False

Answer 2

False. Single axon only

Question 3

information enters the central nervous system through peripheral nerves and is con­
ducted immediately to multiple sensory areas in

Answer 3

(1) the spinal cord at all levels;
(2) the reticular substance of the medulla, pons, and mesencephalon of the brain;
(3) the cerebellum;
(4) the thalamus; and
(5) areas of the cerebral cortex.

Question 4

skeletal muscles can be controlled from many levels of the central nervous system, including

Answer 4

(1) the spinal cord;
(2) the reticular substance of the medulla, pons, and mesencephalon; (3) the basal ganglia;
(4) the cerebellum; and
(5) the motor cortex.

Question 5

junction point from one neuron to the next.

determine the directions that the nervous signals will spread through the nervous system

Answer 5

synapse

Question 6

function of the synapses

Answer 6

memory

Facilitation

Question 7

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 called

Answer 7

facilitation

Question 8

neuronal circuits in the cord can cause

Answer 8

(1) walking movements, (2) relexes that withdraw por­ tions of the body from painful objects,
(3) relexes that stifen the legs to support the body against gravity, and (4) relexes that control local blood vessels, gastrointesti­ nal movements, or urinary excretion.

Question 9

True or False

upper levels of the nervous system often operate by sending signals directly to the periphery of the body

Answer 9

False. by sending signals to the control centers of the cord, simply “com­ manding” the cord centers to perform their functions.

Question 10

subconscious control of arterial pressure and respiration is achieved mainly in

Answer 10

the medulla and pons.

Question 11

combined function of the older portions of the cerebellum and the reticular substance of the medulla, pons, and mesencephalon.

Answer 11

Control of equilibrium

Question 12

Feeding relexes, such as salivation and licking of the lips in response to the taste of food, are controlled by areas in the

Answer 12

medulla, pons, mesencephalon, amygdala, and

hypothalamus

Question 13

emotional patterns such as anger, excitement, sexual response, reaction to pain, and reaction to pleasure can still occur after destruction of much of the cerebral cortex
True or False

Answer 13

True

Question 14

an extremely large memory storehouse.

Fxns in association with lower centers of the nervous system.

Answer 14

cerebral corte

Question 15

it is the cerebral cortex, that initiate wakefulness

True or False

Answer 15

False. it is the lower brain centers, not the cortex, that initiate wakefulness in the cerebral cortex

Question 16

lower brain centers opens the cortex’s bank of memories to the thinking machinery of the brain
True or False

Answer 16

True

Question 17

All these functions can

be classiied as synaptic functions of neurons.

Answer 17

each impulse (1) may be
blocked in its transmission from one neuron to the next,
(2) may be changed from a single impulse into repetitive
impulses, or
(3) may be integrated with impulses from
other neurons to cause highly intricate patterns of
impulses in successive neurons.

Question 18

important neurotransmitters

Answer 18

acetylcholine, norepinephrine, epinephrine,
histamine,
gamma­aminobutyric acid (GABA), glycine,
serotonin, and
glutamate.

Question 19

useful in detecting the coincidence of simultaneous subthreshold depolarizations within a group of interconnected neu­
rons; this enables increased neuronal sensitivity and pro­
motes synchronous iring of a group of interconnected neurons

Answer 19

bidirectional transmis­

sion of electrical synapses

Question 20

it is this speciic transmission of signals to discrete and highly focused areas both within the nervous system and at the terminals of the peripheral nerves that allows the nervous system to perform its myriad functions of sensation, motor control, memory, and many other functions.

Answer 20

principle of one-way conduction

Question 21

These diferences make neurons in diferent parts of the nervous system react diferently to incoming synaptic signals and, therefore, perform many diferent functions.

Answer 21

1. the size of the cell body;
   (2) the length, size, and number of dendrites
   (3) the length and size of the axon; and
   (4) the number of presynaptic terminals

Question 22

structural changes of appropri­
ately activated neurons do not occur, especially in long­
term memory processes.
True or False

Answer 22

False. Do occur

Question 23

he importance of having inhibitory, as well as excitatory, types of receptors is that

Answer 23

this feature gives an additional dimension to nervous function, allowing restraint of nervous action and excitation.

Question 24

It is by far the most widely used means for causing excitation.

Answer 24

Opening of sodium channels to allow large numbers

of positive electrical charges to flow to the interior of the postsynaptic cell.

Question 25

Depressed conduction through chloride or potas- sium channels, or both make the internal membrane potential more posi­ tive than normal, which is inhibitory. True or False

Answer 25

False. Excitatory

Question 26

two groups of synaptic transmitters.

Answer 26

small-molecule, rapidly acting transmitters. he other is made up of a large number of neuropeptides of much larger molecular size that usually act much more slowly.

Question 27

neuropeptides prolonged actions

Answer 27

changes in numbers of neuronal receptors, opening or closure of certain ion channels, changes in numbers of synapses or sizes of synapses.

Question 28

present in the proteoglycan reticulum that ills the space of the synaptic cleft.

Answer 28

cholinesterase

Question 29

Acetylcholine is secreted by neurons in many areas of the nervous system but speciically by

Answer 29

1) the terminals of the large pyramidal cells from the motor cortex, 2) several diferent types of neurons in the basal ganglia 3) the motor neurons that innervate the skeletal muscles 4) the preganglionic neurons of the autonomic nervous system 5) the postganglionic neurons of the parasympathetic nervous system, and 6) some of the postganglionic neurons of the sympathetic nervous system

Question 30

inhibitory efect of acetylcholine

Answer 30

inhibition of the heart by the vagus nerves.

Question 31

Norepinephrine is secreted by

Answer 31

brain stem and hypothalamus | locus ceruleus

Question 32

secreted by neurons that originate in the substantia nigra.

Answer 32

Dopamine

Question 33

It is believed to always act as an inhibitory transmitter.

Answer 33

Glycine GABA

Question 34

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

Answer 34

Glutamate

Question 35

originate in the median raphe of the brain stem and project to many brain and spinal cord areas and to the hypothalamus.

Answer 35

Serotonin

Question 36

especially secreted by nerve terminals in areas of the brain responsible for long­term behavior and memory.

Answer 36

Nitric oxide

Question 37

the action potential begins adjacent to the excit­ atory synapses. True or False

Answer 37

False. it begins in the initial segment of the axon

Question 38

Time required for the excess positive charges to leak out of the excited neuron and to re­establish the normal resting membrane potential.

Answer 38

15 sec

Question 39

change in potential at any single point within the soma will cause the potential to change everywhere inside the soma almost equally. True or False

Answer 39

True

Question 40

successive discharges from a single presynaptic terminal, if they occur rapidly enough, can add to one another

Answer 40

temporal summation.

Question 41

Part of the fatigue process probably results from two other factors as well:

Answer 41

1) progressive inactivation of many of the postsynaptic membrane receptors and (2) slow development of abnor­ mal concentrations of ions inside the postsynaptic neuro­ nal cell.

Question 42

from the axon of a preceding neuron to dendrites on cell mem- branes of subsequent neurons. his feature forces the signal to travel in required directions to perform speciic nervous functions. 

Answer 42

forward direction

Question 43

transmits sensory information from the receptors of the entire body surface and from some deep structures

Answer 43

somatic portion of the sen- | sory system

Question 44

he most important eventual role of the nervous sys- tem is to control the various bodily activities achieved by controlling collectively called motor functions of the nervous system

Answer 44

1) contraction of appropriate skeletal muscles throughout the body; 2) contraction of smooth muscle in the internal organs; and 3) secretion of active chemical substances by both exocrine and endo- crine glands in many parts of the body

Question 45

lower regions (of the levels of the CNS) are concerned primarily with

Answer 45

Automatic, instantaneous muscle responses to sensory stimuli,

Question 46

higher regions are concerned with

Answer 46

deliberate complex muscle movements controlled by thought processes of the brain. 

Question 47

when important sensory information excites the mind, it is immediately channeled into proper inte- grative and motor regions of the brain to cause desired responses. This channeling and processing of information is called the

Answer 47

integrative function of the nervous system.

Question 48

determine the directions that the nervous sig- nals will spread through the nervous system.

Answer 48

Synapses

Question 49

much of the information is stored for future control of motor activities and for use in the thinking processes True or False

Answer 49

True

Question 50

his process gives the person a perception of experiencing the original sensa- tions, although the perceptions are only memories of the sensations.

Answer 50

the syn- apses become so facilitated that signals generated within the brain itself can also cause transmission of impulses through the same sequences of synapses, even when the sensory input is not excited

Question 51

three major levels of the central nervous system have speciic functional characteristics

Answer 51

(1) the spinal cord level; (2) the lower brain or subcortical level; and (3) the higher brain or cor- tical level.

Question 52

the cytoplasms of adjacent cells are directly connected by clusters of ion channels called ? They allow free movement of ions from the interior of one cell to the interior of the next cell.

Answer 52

Gap junctions in electrical synapses

Question 53

he presyn- aptic terminal is separated from the postsynaptic neuro- nal soma by a

Answer 53

synaptic cleft

Question 54

he terminal has two internal structures impor- tant to the excitatory or inhibitory function of the syn- apse:

Answer 54

transmitter vesicles and the mitochondria

Question 55

provide adenosine triphosphate (ATP), which in turn supplies the energy for synthesizing new transmitter substances.

Answer 55

mitochondria

Question 56

contain the neurotransmitter that when released into the synaptic cleft, excites or inhibits the postsynaptic neuron.

Answer 56

transmitter vesicles

Question 57

he quantity of neurotransmitter that is then released from the terminal into the synaptic cleft is directly related to the number of calcium ions that enter True or False

Answer 57

True

Question 58

Receptor activation controls the opening of ion chan- nels in the postsynaptic cell in one of two ways:

Answer 58

1. by gat- ing ion channels directly and allowing passage of speciied types of ions through the membrane; or 2. by activating a “second messenger” that is not an ion channel but, instead, is a molecule that protrudes into the cell cytoplasm and activates one or more substances inside the postsynaptic neuron.

Question 59

Neurotransmitter receptors that directly gate ion channels are often called

Answer 59

ionotropic receptors,

Question 60

those that act through second messenger systems are called

Answer 60

metabotropic receptors.

Question 61

a neurotransmitter that opens cation channels is called an

Answer 61

excitatory transmitter

Question 62

prolonged postsynaptic neuronal excitation or inhibition is achieved by activating ION CHANNELS chemical system inside the postsynaptic neu- ronal cell, and then it is the second messenger that causes the prolonged efect. True or False

Answer 62

SECOND MESSENGER

Question 63

As long as the G protein complex is bound to GDP, it remains active True or False

Answer 63

False. Bound - Inactive

Question 64

The following four changes that can occur when G protein complex is unbounded

Answer 64

1. Opening specific ion channels through the postsyn- aptic cell membrane 2. Activation of cyclic adenosine monophosphate (cAMP) or cyclic guanosine monophosphate (cGMP) in the neuronal cell. 3. Activation of one or more intracellular enzymes 4. Activation of gene transcription.

Question 65

synthesized as integral parts of large- protein molecules by ribosomes in the neuronal cell body. Not in the cytosol

Answer 65

Neuropeptides

Question 66

Another important characteristic of the neuropeptides is that they often cause much more prolonged actions. Some of these actions include

Answer 66

-prolonged closure of calcium channels, -prolonged changes in the metabolic machinery of cells, -prolonged changes in activation or deactivation of spe- ciic genes in the cell nucleus, and/or -prolonged altera- tions in numbers of excitatory or inhibitory receptors.

Question 67

the action potential does not begin adjacent to the excita- | tory synapses. Instead, it begins in

Answer 67

the initial segment of the axon where the axon leaves the neuronal soma.

Question 68

True or False the soma has relatively few voltage- gated sodium channels in its membrane

Answer 68

True. which makes it dicult for the EPSP to open the required number of sodium channels to elicit an action potential. Conversely, the membrane of the initial segment has seven times as great a concentration of voltage- gated sodium channels as the soma

Question 69

he inhibitory synapses mainly open what channels

Answer 69

Cl channels

Question 70

both chloride influx and potas- | sium efflux increase the degree of intracellular negativity,

Answer 70

hyperpolarization.

Question 71

An increase in negativity beyond the normal resting membrane potential level is called an

Answer 71

inhibitory postsynaptic potential (IPSP).

Question 72

caused by release of an inhibi- tory substance onto the outsides of the presynaptic nerve ibrils before their own endings terminate on the post- synaptic neuron.

Answer 72

Presynaptic inhibition

Question 73

opens anion channels, allowing large numbers of chloride ions to difuse into the terminal ibril. he negative charges of these ions inhibit synaptic transmission because they cancel much of the excitatory efect of the positively charged sodium ions that also enter the terminal ibrils when an action potential arrives.

Answer 73

GABA

Question 74

summing simultaneous postsynaptic potentials by activating multiple terminals on widely spaced areas of the neuronal membrane

Answer 74

spatial summation. 

Question 75

the summated postsynaptic potential is excitatory but has not risen high enough to reach the threshold for iring by the postsynaptic neuron. another excitatory signal entering the neuron from some other source can then excite the neuron very easily

Answer 75

When this situation occurs, the neuron is said to be facilitated.

Question 76

It is also important that between 80% and 95% of all the presynaptic terminals of the anterior motor neuron terminate on dendrites, in contrast to only 5% to 20% ter- minating on the neuronal soma. True or False

Answer 76

True

Question 77

direct spread of electrical cur- | rent by ion conduction in the luids of the dendrites but without the generation of action potentials

Answer 77

electrotonic current

Question 78

before the excitatory potentials can reach the soma, a large share of the potential is lost by leakage through the membrane. his decrease in mem- brane potential as it spreads electrotonically along den- drites toward the soma is called

Answer 78

decremental conduction.

Question 79

True or False The farther the excitatory synapse is from the soma of the neuron, the lesser will be the decrement and the greater will be excitatory signal reaching the soma.

Answer 79

False. The farther the excitatory synapse is from the soma of the neuron, the greater will be the decrement and the lesser will be excitatory signal reaching the soma.

Question 80

number of discharges by the postsynaptic neuron is at irst very great, but the iring rate becomes progressively less in succeeding milliseconds or seconds

Answer 80

fatigue of synaptic transmission.

Question 81

he mechanism of SUMMATION is mainly exhaustion or partial exhaustion of the stores of transmitters in the presynaptic terminals. True or False

Answer 81

FALSE. FATIGUE

Question 82

Nor- mally, alkalosis greatly increases neuronal excitability. acidosis greatly depresses neuronal activ- ity; a fall in pH from 7.4 to below 7.0 usually causes a comatose state. True or False

Answer 82

TRUE ALL

Question 83

increase neu- | ronal excitability, presumably by reducing the threshold for excitation of neurons.

Answer 83

caffeine, theophylline, and theobromine,

Question 84

it inhibits the action of some normally inhibitory transmitter substances, especially the inhibitory efect of glycine in the spinal cord.

Answer 84

Strychnine the efects of the excitatory transmitters become overwhelming, and the neurons become so excited that they go into rap- idly repetitive discharge, resulting in severe tonic muscle spasms.