Chapter 9: The Somatic sensory System - Touch

Question 1

Somatic sensation originates from the activity of ________ whose peripheral processes ramify within the skin or in muscle

Answer 1

Afferent nerve fibers

Question 2

_________ convey stimuli from the skin to Central Circuits

Answer 2

Somatosensory afferents

Question 3

Neurons in the _________ and in the __________ (for the body and head, respectively) are the critical links supplying central nervous system circuits with information about sensory events that occur in the periphery

Answer 3

Dorsal root ganglia, Cranial nerve ganglia

DC

Question 4

The territory innervated by each spinal nerve

is called a ____________

Answer 4

dermatome

Question 5

Somatic sensory afferents differ significantly in their response properties and these differences, taken together, define distinct classes of afferents, each of which makes unique contributions to somatic sensation.

Answer 5

a) Axon diameter
b) size of the receptive field
c) response to sensory stimulation

Question 6

Rapid ly adapting afferents (those that become
quiescent in the face of continued stimulation) are thought to be particularly effective in conveying information about changes in ongoing stimulation such as those produced by stimulus movement.

Answer 6

In contrast, slowly adapting afferents are better suited to provide information about the spatial attributes of the stimulus, such as size and shape

Question 7

The axons of cutaneous mechanosensory afferents enter the spinal cord through the _________ and the majority ascend __________ through the dorsal
columns

Answer 7

dorsal roots (also called the posterior funiculi)

ipsilaterally (Located on or affecting the same side of the body)

Question 8

____________ conducts the nerve impulse from the receptor to the spinal cord or brain stem

Answer 8

First order neuron

1st order neurons ascend ipsilaterally & synapse on 2nd order neurons.

Question 9

_________ conducts the impulse from the brainstem- spinal cord to the thalamus (ALWAYS ENDS IN THE THALAMUS)

Answer 9

Second order neuron

2nd order neurons decussate & synapse on contra-laterally (Taking place or originating in a corresponding part on an opposite side) thalamus.

Question 10

____________ in the ventral posterior lateral nucleus (VPL) send their axons via the internal capsule to terminate in the post-central gyrus of the cerebral cortex, a region known as the primary somatosensory cortex.

Answer 10

Third-order neurons

*Draw & label

Question 11

__________ conducts nerve impulses from the thalamus to the primary somatosensory area.

Answer 11

Third order neuron

Question 12

Draw the brain and label

1) Somatic sensory cortex
2) four distinct regions, or fields, known as Brodrnann’s areas 3a, 3b, 1, and 2

Answer 12

Go…

Question 13

If neuron origintes from face travels through __________

Answer 13

a crainal nerve to the brainstem.

Question 14

If neuron originates from anywhere else enters ___________

Answer 14

a spinal nerve and enter the spinal cord.

Question 15

Peripheral and central components of afferent fibers are continuous, attached to the cell body in the ganglia by a single process.

Answer 15

For this reason, neurons in the dorsal root ganglia are often called pseudounipolar. Because of this configuration, conduction of electrical activity through the membrane of the cell body is not an
obligatory step in conveying sensory information to central targets.

Question 16

sensory transduction

Answer 16

the process of converting the energy of a stimulus into an electrical signal somatic sensory afferents: a stimulus alters the permeability of cation channels in the afferent nerve endings, generating a depolarizing current known as a receptor (or generator) potential

Question 17

If sufficient in magnitude, the receptor potential reaches threshold for the generation of action potentials in the afferent fiber; the resulting rate of action potential firing is roughly proportional to the magnitude of the depolarization

Answer 17

get this

Question 18

Cervical/Thoracic/Lumbar/Sacral

Answer 18

C - Hands
T- Chest/Back
L- Legs
S - Genitalia/Feet bottoms

Question 19

The axons of cutaneous mechanosensory afferents enter the spinal cord through the dorsal roots and the majority ascend ipsilaterally through the dorsal
columns

Answer 19

DRAW/LABEL

Question 20

1st order neurons ascend ipsilaterally & synapse on 2nd order neurons.

Answer 20

2nd order neurons decussate & synapse on contralaterally thalamus

Question 21

First order neuron

Answer 21

conducts the nerve impulse from the receptor to the spinal cord or brain stem

Question 22

Second order neuron

Answer 22

conducts the impulse from the brainstem- spinal cord to the thalamus (ALWAYS ENDS IN THE THALAMUS)

BSt

Question 23

Third-order neurons

Answer 23

conducts nerve impulses from the thalamus to the primary somatosensory area.

Question 24

primary somatosensory area location

Answer 24

Central sulcus [ Somatic sensory area] Posterior parietal cortex

Question 25

The primary somatic sensory cortex in humans (also called Sl) is located

Answer 25

in the postcentral gyrus of the parietal lobe and comprises four distinct regions, or fields, known as Brodrnann’s areas 3a, 3b, 1, and 2

Question 26

Mapping studies in humans and other primates show further that each of these four cortical areas contains a separate and complete representation of the body.

Answer 26

DRAW