Chapter 47 - Guyton

Question 1

mechanoreceptive somatic senses

Answer 1

both tactile and position sensations that are stimulated by mechanical displacement of some tissue of the body

Question 2

thermoreceptive senses

Answer 2

detect heat and cold

Question 3

three physiologic types of somatic senses

Answer 3

mechanoreceptive, thermoreceptive, pain

Question 4

Exteroreceptive sensations

Answer 4

surface of the body

Question 5

Proprioceptive sensations

Answer 5

physical state of the body, including position sensations, tendon and muscle sensations, pressure sensations from the bottom of the feet, and sensation of equilibrium

Question 6

Visceral sensations

Answer 6

from the viscera of the body; refers specifically to sensations from the internal organs

Question 7

Deep sensations

Answer 7

from deep tissues, such as from fascia,

muscles, and bone; include mainly “deep” pressure, pain, and vibration

Question 8

Principle differences among tactile sensations.

Answer 8

1) touch sensation from
stimulation of tactile receptors in skin or just below; 2) pressure sensation from deformation of deeper tissues; 3) vibration sensation results from rapidly repetitive sensory signals, but some of the same types of receptors as those for touch and pressure are used

Question 9

These tactile receptors are found everywhere in the skin and in many other tissues.

Answer 9

free nerve endings

Question 10

These tactile receptors present in the nonhairy parts of the skin and are particularly abundant in the fingertips, lips, and other areas of the skin where one’s ability to discern spatial locations of touch sensations is highly developed.

Answer 10

Meissner’s corpuscle (great sensitivity)

Question 11

These tactile receptors are responsible for giving

steady-state signals that allow one to determine continuous touch of objects against the skin.

Answer 11

Merkel’s discs (hairy and non-hairy skin)

Question 12

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

Answer 12

Meissner’s corpuscle and Merkel’s discs

Question 13

An entire group of Merkel’s discs would be innervated by which type of fiber?

Answer 13

a single large, myelinated nerve fiber (type A beta)

Question 14

Merkel’s discs are often grouped together in a

receptor organ called:

Answer 14

Iggo dome receptor

Question 15

These endings adapt very slowly and, therefore, are important for signaling continuous states of deformation of the tissues, such as heavy prolonged touch and pressure signals (also in joint capsules and sense degree of joint rotation).

Answer 15

Ruffini’s end-organs

Question 16

They are particularly important for detecting tissue vibration or other rapid changes in the mechanical state of the tissues.

Answer 16

Pacinian corpuscles

Question 17

Free nerve ending tactile receptors transmit signals mainly by way of which type of fiber?

Answer 17

type A delta, 5-30 m/sec

Question 18

Almost all specialized sensory receptors, such as
Meissner’s corpuscles, Iggo dome receptors, hair receptors, pacinian corpuscles, and Ruffini’s endings transmit their signals in which type of fiber?

Answer 18

type A beta nerve fibers that have

transmission velocities ranging from 30-70 m/sec

Question 19

Some tactile free nerve endings transmit by way of
type C unmyelinated fibers at velocities from a fraction of a meter up to 2 m/sec; these send signals into the spinal cord and lower brain stem, probably subserving mainly the sensation of:

Answer 19

tickle

Question 20

Which tactile receptors can detect vibration?

Answer 20

all but mainly pacinian and meissner’s

Question 21

From the entry point into the cord and then to the brain, the sensory signals are carried through one of two alternative sensory pathways:

Answer 21

1) the dorsal column–medial

lemniscal system or 2) the anterolateral system (come back together at the thalamus)

Question 22

Sensory information that must be transmitted rapidly and with temporal and spatial fidelity is transmitted mainly in the:

Answer 22

dorsal column-medial leminiscal system (large, myelinated fibers)

Question 23

Sensory information which does not
need to be transmitted rapidly or with great spatial
fidelity is transmitted mainly in the:

Answer 23

anterolateral system (small, myelinated fibers)

Question 24

The ability to transmit a broad spectrum of sensory modalities—pain, warmth, cold, and crude tactile sensations is transmitted by:

Answer 24

anterolateral system

Question 25

Dorsal Column-Medial Leminiscal System

Answer 25

1. Touch sensations requiring a high degree of
   localization of the stimulus
2. Touch sensations requiring transmission of fine
   gradations of intensity
3. Phasic sensations, such as vibratory sensations
4. Sensations that signal movement against the skin
5. Position sensations from the joints
6. Pressure sensations having to do with fine degrees of judgment of pressure intensity

Question 26

Anterolateral System

Answer 26

1. Pain
2. Thermal sensations, including both warmth and
   cold sensations
3. Crude touch and pressure sensations capable only of crude localizing ability on the surface of the
   body
4. Tickle and itch sensations
5. Sexual sensations

Question 27

In the dorsal columns of the spinal cord, the fibers from the lower parts of the body lie toward the ______ of the cord, whereas those that enter the cord at progressively higher segmental levels form successive layers ______.

Answer 27

center, laterally

Question 28

Contains large, myelinated fibers for fast transmission (30-110 m/sec).

Answer 28

dorsal column system

Question 29

Contains smaller myelinated and unmyelinated fibers for slow transmission (0.5-40 m/sec).

Answer 29

anterolateral system

Question 30

Where does the crossing of fibers occur in the Dorsal Column-Medial Lemniscal System.

Answer 30

medulla

Question 31

Somatic Sensory Cortex

Answer 31

located in the post-central gyrus, highly organized distinct spatial orientation, each side receives info from opposite side of body

Question 32

In the somatic sensory cortex, which areas have the greatest representation.

Answer 32

lips, face, thumb

Question 33

In what layer do incoming signals enter the cerebral cortex?

Answer 33

layer IV and spread up and down (layers I and II receive diffuse input from lower brain centers)

Question 34

Which layers send axons to closely related portion of the cortex for communicating?

Answer 34

layers II and III

Question 35

Layer V sends axons to:

Answer 35

brain stem and spinal cord

Question 36

Layer VI sends axons to:

Answer 36

thalamus

Question 37

Damage to Somatic Area I could result in?

Answer 37

loss of discrete localization ability, inability to judge degree of pressure, inability to determine weight of an object, inability to determine shape or form of object (astereognosis), inability to judge texture

Question 38

Somatic Association Areas

Answer 38

located behind the somatic sensory cortex in the parietal area of the cortex; receives input from somatic sensory cortex, ventrobasal nuclei of thalamus, visual and auditory cortex; functions to decipher sensory meaning

Question 39

Special Aspects of Thalamus Function

Answer 39

some ability to discriminate tactile sensation, important role in perception of pain and temperature

Question 40

Damage to what area might result in a person being unable to sense the form of one side of the body (amorphosynthesis).

Answer 40

Somatic Association Area

Question 41

What occurs during two-point discrimination in the nervous system to help distinguish the point of touch?

Answer 41

lateral inhibition

Question 42

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

Answer 42

pacinian corpuscles and muscle spindles

Question 43

These fibers are inhibitory and can suppress the sensory input. They function to decrease the spread of signal, sharpen the degree of contrast, and adjust the sensitivity of the system.

Answer 43

corticofugal fibers (run backwards from cortex to thalamus, medulla, and spinal cord)