Neuroscience Somethesis Steven Youngentob

Question 1

To what kind of stimulus do slowly adapting mechanoreceptors respond?

Answer 1

Enduring

Question 2

To what kind of stimulus do rapidly adapting mechanoreceptors respond?

Answer 2

At the onset and sometimes the termination of a long stimulus

Question 3

What is one similarity between the two kinds of tactile receptors (slowly adapting and rapidly adapting)?

Answer 3

They are both more active at the beginning of a stimulus

Question 4

Name this: the portion of the skin directly innervated by the receptor terminals and the area of adjacent tissue through which a stimulus can be conducted through the receptor.

Answer 4

The receptive field

Question 5

Areas of the skin most sensitive to touch, ie fingers, have what large or small receptive fields?

Answer 5

Small, and the largest # of receptive fields per unit area.

Question 6

What type of mechanoreceptor is a Merkel’s cell?

Answer 6

Slowly adapting

Question 7

What type of mechanoreceptor is a Meissner’s corpuscle?

Answer 7

Rapidly adapting

Question 8

What type of mechanoreceptor is a Pacinian corpuscle?

Answer 8

Rapidly adapting

Question 9

What are the two major ascending systems carrying somatosensory information to the cerebral cortex?

Answer 9

1. Dorsal column-lemniscal system

2. Anterolateral system

Question 10

What is the main function of the dorsal column-lemniscal system?

Answer 10

To mediate tactile sensations including vibration sense and proprioception

Question 11

What is the main function of the anterolateral system?

Answer 11

To carry information mostly about pain and temperature sensation

Question 12

The tactile information transmitted by the _______ provides crude touch and pressure information, poo localizing ability on the body and little capacity for fine intensity discrimination.

Answer 12

Anterolateral system

Question 13

1. Sacral axons enter the spinal cord and are packed where?

2. The axons added at higher levels are packed at successively more _____ positions.

Answer 13

1. Near the midline

2. Laterally

Question 14

Is the cuneate fascicle more lateral or more midline in the spinal cord?

Answer 14

Lateral

Question 15

Is the gracile fascicle more lateral or more midline in the spinal cord?

Answer 15

Midline

Question 16

The dorsal column-lemniscus system has nerve fibers that enter the dorsal column and travel up what side of the body?

Answer 16

Ipsilateral to the ipsilateral side of the caudal medulla

Question 17

What are the nuclei where dorsal nerves synapse and where are the nuclei located?

Answer 17

Gracile and cuneate nuclei, together called the dorsal column nuclei, in the caudal medulla

Question 18

What is different about a second order receptive neuron, as compared with a regular receptor neuron?

Answer 18

The second-order receptive neuron has both excitatory and inhibitory regions

Question 19

How does a receptive field become larger?

Answer 19

It receives more input from primary sensory neurons

Question 20

T or F: Receptive fields have overlapping areas.

Answer 20

True

Question 21

What is the medial lemniscus?

Answer 21

The bundle of fibers traveling from the dorsal column nuclei to the brain. They are delivering contralateral information from second order sensory neurons that have decussated upon entering the spinal column.

Question 22

The fibers of the medial lemniscus synapse on the _____ of the thalamus.

Answer 22

ventral posterior nucleus

Question 23

How many sections is the ventral posterior nucleus divided into? What are they called?

Answer 23

Two, the medial and lateral division.

Question 24

The medial division of the ventral posterior nucleus received input from what?

Answer 24

Input from the face

Question 25

The lateral division of the ventral posterior nucleus receive input from what?

Answer 25

Input from the trunk and limbs

Question 26

Sensory information about a particular modality from one part of the body is processed by collections of neurons that form what?

Answer 26

Discrete functional units in the thalamus

Question 27

Within the thalamic nuclei, __1__ is represented mediolaterally and __2__ is represented anteroposteriorly.

Answer 27

1. place | 2. modality

Question 28

The cortical region that receives somatosensory input from the central posterior nucleus is located:

Answer 28

in the postcentral gyrus (primary somatosensory cortex)

Question 29

The projections of the medial and lateral divisions of the VPN are directed to different portions of the postcentral gyrus: Which goes to which side?

Answer 29

The lateral division projects to the medial and superior portions of the postcentral gyrus. The medial division projects to the lateral portion of the postcentral gyrus.

Question 30

The somatosensory cortex is subdivided into four cytoarchitectural regions called:

Answer 30

Brodmann's areas 1, 2, 3a and 3b.

Question 31

In what subdivisions of the somatosensory cortex do the thalamic fibers terminate?

Answer 31

3a and 3b

Question 32

The cells 3a and 3b project where in the postcentral gyrus?

Answer 32

1 and 2

Question 33

What did early electrophysiological experiments show?

Answer 33

That the body surface is represented in the brain in an orderly fashion.

Question 34

Wilder Penfield found that stimulation of the postcentral gyrus produced tactile sensations where?

Answer 34

On the opposite side of the body

Question 35

Why were Wilder Penfields experiments important clinically?

Answer 35

They explained how a disturbance in the somatosensory system could be localized clinically.

Question 36

What is a Jacksonian seizure?

Answer 36

Numbness beginning at the fingertip and progressing to the shoulder, spinal cord and then down the ipsilateral leg

Question 37

In the most posterior portion of the somatosensory cortex, there are vertical columns that only respond to __1__. These cells are primarily found in areas __2__, but most of all in area __3__.

Answer 37

1. When a stimulus moves across the skin in a particular direction 2. 1 and 2 3. 2