Organization of the Nervous System, Basic Functions of Synapses, and Neurotransmitters

Question 1

SENSORY PART OF THE NERVOUS

SYSTEM—SENSORY RECEPTORS

Answer 1

somatic portion of the sensory
system, which transmits sensory information from the
receptors of the entire body surface and from some
deep structures. This information enters the central
nervous system through peripheral nerves and is conducted immediately to multiple sensory areas in (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 2

what is somatic nervous system

Answer 2

he somatic nervous system is a component of the peripheral nervous system associated with the voluntary control of the body movements

Question 3

motor functions of the nervous system

Answer 3

(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 endocrine glands in many parts of the body

Question 4

muscle and glands functioning as motor functions are called

Answer 4

effectors

Question 5

that the skeletal muscles can
be controlled from many levels of the central nervous
system which are

Answer 5

(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 6

e integrative function of the nervous system

Answer 6

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

Question 7

most storage occurs in?

Answer 7

Most storage occurs in the cerebral cortex, but
even the basal regions of the brain and the spinal cord can
store small amounts of information

Question 8

what is fascillation

Answer 8

if one type of nerve impulse travels from a synpase more than one time the synpase becomes more capable of transmitting the same impulse After the sensory
signals have passed through the synapses a large number
of times, the synapses 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 9

three major levels of the

central nervous system have specific functional characteristics

Answer 9

(1) the spinal cord level, (2) the lower brain or

subcortical level, and (3) the higher brain or cortical level.

Question 10

Even after the spinal cord has been cut in the high neck region, many highly organized spinal cord functions still occur.
For instance,?

Answer 10

neuronal circuits in the cord can cause
(1) walking movements, (2) reflexes that withdraw portions of the body from painful objects, (3) reflexes that
stiffen the legs to support the body against gravity, and
(4) reflexes that control local blood vessels, gastrointestinal movements, or urinary excretion.

Question 11

subconscious activities of the body is controlled by

Answer 11

Many, if not most, of what we call subconscious activities of the body are controlled in the lower areas of the
brain—that is, in the medulla, pons, mesencephalon,
hypothalamus, thalamus, cerebellum, and basal ganglia.

Question 12

cerebral cortex function

Answer 12

store house of memory
works in association with lower parts of the brain
withoutthe cortex the lower parts of the brain does not work as effeciently

Question 13

synaptic functions of the neuron

Answer 13

(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. A

Question 14

2 types of synapses

Answer 14

chemical and electric

Question 15

chemical synapse

Answer 15

In these synapses, the first neuron secretes
at its nerve ending synapse a chemical substance called a
neurotransmitter (often called a transmitter substance),
and this transmitter in turn acts on receptor proteins
in the membrane of the next neuron to excite the
neuron, inhibit it, or modify its sensitivity in some other
way

Question 16

eg of nerotransmitters

Answer 16

acetylcholine, norepinephrine, epinephrine, histamine,
gamma-aminobutyric acid (GABA), glycine, serotonin,
and glutamate.

Question 17

electrical synapse

Answer 17

ions move through gap junctions from cytoplasm of one cell to another

Question 18

principle of one-way conduction

Answer 18

. This characteristic is that they
always transmit the signals in one direction—that is, from
the neuron that secretes the neurotransmitter, called the
presynaptic neuron, to the neuron on which the transmitter acts, called the postsynaptic neuron.

Question 19

role of calcium

Answer 19

when action potential reaches presynaptic molecule depolarization occurs which causes ca ions to be released into the terminal The 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.
calcium binds with release protein in the presynaptic membrane and releease neurotransmitter in the cleft

Question 20

The membrane of the postsynaptic neuron contains

large numbers of receptor proteins, also shown in . The molecules of these receptors have two important components

Answer 20

(1) a binding component that protrudes
outward from the membrane into the synaptic cleft—
here it binds the neurotransmitter coming from the presynaptic terminal—and (2) an intracellular component
that passes all the way through the postsynaptic membrane to the interior of the postsynaptic neuron

Question 21

receptor activation controls the opening of ion channels in the
postsynaptic cell in one of two ways:

Answer 21

(1) by gating ion
channels directly and allowing passage of specified 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 22

Neurotransmitter receptors that directly gate ion
channels are often called those that act through second messenger systems are
called ?

Answer 22

ionotropic receptors,

metabotropic receptors

Question 23

second messenger main role

Answer 23

memory is a prolomged neuronal effect which can be causes only due to te releasing of second messenger because the gated ion channels close in milliseconds but the second messenger doesn’t ( pg 575)

Question 24

changes that can occur trough second messenger

Answer 24

1. Opening specific ion channels through the postsynaptic 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
   Activation of gene transcription.

Question 25

the mechanism of excitation

Answer 25

1. Opening of sodium channels to allow large numbers
   of positive electrical charges to flow to the interior
   of the postsynaptic cell
2. Depressed conduction through chloride or potassium channels, or both.
3. Various changes in the internal metabolism of
   the postsynaptic neuron to excite cell activity

Question 26

the mechanism of inhibition

Answer 26

1. Opening of chloride ion channels through the postsynaptic neuronal membrane
2. Increase in conductance of potassium ions out of the
   neuron.
3. Activation of receptor enzymes

Question 27

Acetylcholine is secreted by neurons in

many areas of the nervous system but specifically by

Answer 27

(1) the terminals of the large pyramidal cells from the
motor cortex, (2) several different 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 28

acytelcholine inhibitory affect

Answer 28

to heart by vagus

Question 29

noreapiniphrine

Answer 29

is secreted by the terminals of many
neurons whose cell bodies are located in the brain stem
and hypothalamus. Specifically, norepinephrine-secreting
neurons located in the locus ceruleus in the pons send
nerve fibers to widespread areas of the brain to help
control overall activity and mood of the mind, such as
increasing the level of wakefulness released by some postganglionic synoathetic

Question 30

dopamine is secreted by

Answer 30

substantia nigra group of neurons in the striatal region of basal ganglion

Question 31

glycine

Answer 31

secreted by spinal cord has inibtory effect

Question 32

GABA

Answer 32

GABA (gamma-aminobutyric acid) is secreted by
nerve terminals in the spinal cord, cerebellum, basal
ganglia, and many areas of the cortex. It is believed to
always cause inhibition.

Question 33

serotinin

Answer 33

Serotonin is secreted by nuclei that originate in the
median raphe of the brain stem and project to many brain
and spinal cord areas, especially to the dorsal horns of the
spinal cord and to the hypothalamus. Serotonin acts as an
inhibitor of pain pathways in the cord, and 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

Question 34

nitric oxide

Answer 34

Nitric oxide is especially secreted by nerve terminals
in areas of the brain responsible for long-term behavior
and memory.

Question 35

wheere neuropeptides are formed

Answer 35

by ribosomes in the neuron cell body

Question 36

formation of neuropeptides

Answer 36

in rer the neuropeptide forming protein breaks into fragments and by Golgi apparatus they are formed into transmitter vesicle which are transported by axons through axon streaming to the neuronal terminals

Question 37

raphe nucleus co-release

Answer 37

serotonin and glutamate

Question 38

spinal motor neuron resting membrane potential

Answer 38

-65 mV
if more minus then inhibitory effect
if less minus then excitability affect

Question 39

difference of concentration of ions

Answer 39

At the top, the sodium ion concentration is
shown to be high in the extracellular fluid (142 mEq/L)
but low inside the neuron (14 mEq/L). This sodium concentration gradient is caused by a strong somal membrane sodium pump that continually pumps sodium out
of the neuron
potassium ion concentration is high inside the neuronal soma (120 mEq/L) but
low in the extracellular fluid (4.5 mEq/L). Furthermore,
it shows that there is a potassium pump (the other
half of the Na+
-K+
pump) that pumps potassium to the
interior.

Question 40

excitatory
postsynaptic potential (or EPSP)

Answer 40

This positive increase in
voltage above the normal resting neuronal potential—
that is, to a less negative value—is called the excitatory
postsynaptic potential (or EPSP), because if this potential
rises high enough in the positive direction, it will elicit an action potential in the postsynaptic neuron, thus exciting
it.

Question 41

why Generation of Action Potentials in the Initial Segment

of the Axon Leaving the Neuron

Answer 41

The main reason for this point of origin of the action
potential is that the soma has relatively few voltagegated sodium channels in its membrane, which makes
it difficult 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 does the soma and, therefore, can generate an
action potential with much greater ease than can the
soma. The EPSP that will elicit an action potential in
the axon initial segment is between +10 and +20 millivolts, in contrast to the +30 or +40 millivolts or more
required on the soma.

Question 42

Effect of Inhibitory Synapses on the Postsynaptic

Membrane—Inhibitory Postsynaptic Potential.

Answer 42

Therefore, opening the chloride channels will allow negatively charged
chloride ions to move from the extracellular fluid to the interior, which will make the interior membrane
potential more negative than normal, approaching the
−70 millivolt level. Opening potassium channels will allow positively
charged potassium ions to move to the exterior and will
also make the interior membrane potential more negative
than usual. Thus, both chloride influx and potassium
efflux increase the degree of intracellular negativity, which
is called hyperpolarization. This increase inhibits the
neuron because the membrane potential is even more
negative than the normal intracellular potential. Therefore,
an increase in negativity beyond the normal resting membrane potential level is called an inhibitory postsynaptic
potential (IPSP

Question 43

spatial

summation

Answer 43

This effect of summing simultaneous postsynaptic
potentials by activating multiple terminals on widely
spaced areas of the neuronal membrane is called spatial
summation.

Question 44

temporal summation.

Answer 44

Thus, 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.

Question 45

dendrites fail to transmit action potential

Answer 45

they have less na voltage gated channels to they trasnmit the umpulse through electric currect in the dendritic soma

Question 46

fatigue of synaptic transmission is imrtant in

Answer 46

brain epileptic siezures

Question 47

alkalosis causes what and why?

Answer 47

For
instance, a rise in arterial blood pH from the 7.4 norm to
7.8 to 8.0 often causes cerebral epileptic seizures because
of increased excitability of some or all of the cerebral
neurons. In a person who is predisposed to epileptic seizures, even a short period of hyperventilation, which
blows off carbon dioxide and elevates the pH, may precipitate an epileptic attack