Somatic Sensations

Question 1

an elon­ gated encapsulated nerve ending of a large (type A β) myelinated sensory nerve iber.

present in the nonhairy parts of the skin
sensitive to movement of objects over the surface of the skin, as well as to low­frequency vibration.

Answer 1

Meissner’s corpuscle

touch receptor with great sensitivity

Question 2

six entirely diferent types of tactile receptors

Answer 2

free nerve endings,

Meissner’s corpuscle

expanded tip tactile receptors, one type of which is Merkel’s discs,

hair end-organ

Ruffini’s endings,

Pacinian corpuscles

Question 3

they transmit an initially strong but partially adapting signal and then a continuing weaker signal that adapts only slowly
responsible for giving steady­state signals that allow one to determine continuous touch of objects against the skin.

Answer 3

Merkel’s discs,

Question 4

play extremely important roles in localizing touch sensations to speciic surface areas of the body and in determining the texture of what is felt.

Answer 4

Merkel’s discs

Meissner’s corpuscles

Question 5

found in joint capsules and help to signal the degree of joint rotation

multibranched, encapsulated endings

important for signaling continuous states of deformation of the tissues, such as heavy prolonged touch and pressure signals.

Answer 5

Ruffini’s endings

Question 6

stimulated only by rapid local compression of the tissues because they adapt in a few hundredths of a second.

important for detecting E
tissue vibration or other rapid changes

Answer 6

Pacinian corpuscles

Question 7

Merkel discs are often grouped together in a receptor organ called the

Answer 7

Iggo dome receptor,

Question 8

Not all tactile receptors are in­ volved in detection of vibration, diferent recep­ tors detect diferent frequencies of vibration.

Answer 8

False. All tactile receptors are in­ volved in detection of vibration, although diferent recep­ tors detect diferent frequencies of vibration.

Question 9

Pacinian corpuscles can detect signal vibrations from

Answer 9

30 to 800 cycles/sec because they respond extremely rapidly to minute and rapid deformations of the tissues.

Question 10

transmis­sion velocities ranging from 30 to 70 m/sec

Answer 10

Almost all specialized sensory receptors transmit their signals in type Aβ nerve ibers

Question 11

com­
posed of large, myelinated nerve ibers that transmit signals to the brain at velocities of 30 to 110 m/sec,

high degree of spatial orientation of the nerve ibers with respect to their origin

Answer 11

dorsal column–medial lemniscal system

Question 12

composed of smaller myelinated ibers that transmit signals at velocities ranging from a few meters per second up to 40 m/sec.

Answer 12

anterolateral system

Question 13

he anterolateral system has a special capability that the dorsal system does not have

Answer 13

ability to transmit a broad spectrum of sensory modalities, such as pain, warmth, cold, and crude tactile sensation

Question 14

local neurons in the intermediate and anterior portions of the cord gray matter serve three functions:

Answer 14

give of ibers that enter the
dorsal columns of the cord and then travel upward to the brain

terminate
locally in the spinal cord gray matter to elicit local spinal cord relexes,

give rise to the spinocerebellar tracts

Question 15

thalamic sensory relay area

Answer 15

ventrobasal complex

Question 16

From the ventrobasal complex, third-order nerve fibers project mainly to the post- central gyrus of the cerebral cortex, which is called

Answer 16

somatic sensory area I

Question 17

Spatial Orientation of the Nerve
Fibers in the Dorsal Column–Medial
Lemniscal System

Fibers from the lower parts of the body lie toward the center of the cord, whereas those that enter the cord at progressively higher segmen­
tal levels form successive layers laterally.
True or False

Answer 17

True

Question 18

Spatial Orientation of the Nerve
Fibers in the Dorsal Column–Medial
Lemniscal System

tail end of the body represented by the most medial portions of the ventrobasal complex and the head and face represented by the lateral areas of the complex
True or False

Answer 18

False

tail end of the body represented by the most lateral portions of the ventrobasal complex and the head and face represented by the medial areas of the complex

Question 19

the portion of the cerebral cortex anterior to the central issure and constituting the posterior half of the frontal lobe is called

Answer 19

motor cortex

Question 20

lies immediately behind the central issure, located in the postcentral gyrus of the human cerebral cortex

Answer 20

Somatosensory Area I

Question 21

Those in layer
VI are generally larger and project to more distant
areas, such as to the basal ganglia, brain stem, and
spinal cord, where they control signal transmission.
True or False

Answer 21

False. Layer v

Question 22

signals from these sensory columns then spread anteriorly, directly to the motor cortex located immediately forward of the central issure.

Answer 22

Brodmann’s area 3A

Question 23

The Sensory Cortex Is Organized
in horizontal Columns of Neurons;
True or False

Answer 23

False. Vertical

Question 24

Functions of Somatosensory Area I

Answer 24

localize discretely the dif­
ferent sensations in the diferent parts of the body. 
Judge critical  degrees  of
pressure
weights of objects.
shapes  or  forms  of
objects. (astereognosis)
And texture of materials

Question 25

he capability of the sensorium to distinguish this presence of two points of stimulation is strongly inluenced by

Answer 25

lateral inhibi-

tion,

Question 26

It is likely that these are the receptors most responsible for detecting rate of movement.

Answer 26

Pacinian corpuscles and muscle spindles

Question 27

cross immediately in the anterior commissure of the cord to the opposite anterior and lateral white columns, where they turn upward toward the brain by way of the anterior spi-
nothalamic and lateral spinothalamic tracts.

Answer 27

anterolateral ibers

Question 28

transmitted in the backward direction from the cerebral cortex to the lower sensory relay stations of the thalamus, medulla, and spinal cord; they control the intensity of sensitivity of the sensory input.

Answer 28

corticofugal signals

Question 29

when sensory input intensity becomes too great, the corti­ cofugal signals automatically decrease transmission in the relay nuclei
True or False

Answer 29

True

Question 30

Three Types of Stimuli Excite Pain Receptors

Answer 30

Mechanical, Thermal, and Chemical

Question 31

enhance the sensitivity of pain endings but do not directly excite them.

Answer 31

prostaglandins and substance P

Question 32

especially important in stimulating the slow, sufering type of pain that occurs after tissue injury.

Answer 32

chemi-

cal substance

Question 33

increase in sen-

sitivity of the pain receptors

Answer 33

hyperalgesia

Question 34

pain resulting from heat is closely correlated with the rate at which damage to the tissues is occurring and not with the total damage that has already occurred.
True or False

Answer 34

True

Question 35

neurotransmitter substance secreted in the spinal cord at the type Aδ pain nerve iber endings.

Answer 35

Glutamate

Question 36

the Probable Slow-Chronic Neurotrans- mitter of Type C Nerve Endings

Answer 36

Substance P

Question 37

natural opiate of the brain.

All are breakdown products of three large protein molecules:

Answer 37

pro-opiomelanocortin, proenkephalin, and prodynorphin.

Question 38

Only one tenth to one fourth of the ibers pass all the way to the thalamus. Instead, most terminate in one of three areas:

Answer 38

1) the reticular nuclei of the medulla, pons, and mesencephalon; (2) the tectal area of the mesencephalon deep to the superior and inferior colliculi; or (3) the periaqueductal gray region surrounding the aqueduct of Sylvius.

Question 39

he analgesia system consists of three major components:

Answer 39

periaqueductal gray and periventricular areas

raphe magnus nucleus and nucleus reticularis paragiganto-
cellularis

a pain inhib-
itory complex located in the dorsal horns of the spinal cord.

Question 40

a thin midline nucleus located in the lower pons and upper medulla,

Answer 40

raphe magnus nucleus

Question 41

Among the more important of these opiate-like sub-

stances are

Answer 41

β-endorphin, met-enkephalin, leu-enkephalin, and dynorphin.

Question 42

True or False

inactivation of pain pathways by morphine-like drugs, can almost totally suppress many pain signals entering thru the peripheral nerves

Answer 42

True

Question 43

the basis of pain relief by acupuncture.

Answer 43

simultaneous psychogenic excitation of the central analgesia system

stimulation of large-type Aβ sensory ibers from peripheral tactile receptors can depress transmission of pain signals

Question 44

Causes of True Visceral Pain

Answer 44

ischemia of visceral tissue,
chemical damage to the surfaces of the viscera,
spasm of the smooth muscle of a hollow viscus,
excess distention of a hollow viscus, and
stretching of the connective tissue surrounding or within

Question 45

theory that explains migraine headache must also

explain the prodromal symptoms.

Answer 45

prolonged
emotion or tension causes relex vasospasm of some of the arteries of the head

spreading cortical
depression,

psychological abnormalities,
and vasospasm

caused by excess local potassium in the cerebral extracel-
lular luid.

genetic predisposition

Question 46

Most areas of the body have 3 to 10 times as many cold spots as warmth spots,
True or False

Answer 46

True

Question 47

thermal detection probably results from direct phy- sical efects of heat or cold on the nerve endings
True or False

Answer 47

False. thermal detection probably results not from direct phy- sical efects of heat or cold on the nerve endings but from chemical stimulation of the endings as modiied by temperature.