Somatosensory System

Question 1

Modality: Touch, Sensed Stimuli:

Answer 1

Contact with body surface

Question 2

Modality: Pain, Sensed Stimuli:

Answer 2

Tissue damage

Question 3

Modality: Hearing, Sensed Stimuli:

Answer 3

Sound vibrations in the air

Question 4

Modality: Vestibular, Sensed Stimuli:

Answer 4

Head movement and orientation

Question 5

Modality: Joint, Sensed Stimuli:

Answer 5

Position and movement

Question 6

Modality: Muscle, Sensed Stimuli:

Answer 6

Tension

Question 7

Modality: Vision, Sensed Stimuli:

Answer 7

Photons from light sources or reflected from sources

Question 8

Modality: Smell, Sensed Stimuli:

Answer 8

Odorant chemicals in the air

Question 9

Modality: Taste, Sensed Stimuli:

Answer 9

Substances on taste receptors

Question 10

Somatosensory System Pathway

Answer 10

1. Somatosensory afferent neurons convey information from the skin surface via sensory ganglion cells
2. Via sensory ganglion cells, information goes to the dorsal horn of the spinal cord
3. Information from the dorsal horn ascends to the sensory cortex

Question 11

Dorsal root ganglion

Answer 11

Ganglion cells carrying sensory neural information from the body

Question 12

Cranial nerve ganglion

Answer 12

Ganglion cells carrying sensory neural information from the brain

Question 13

Dorsal horn

Answer 13

A division of the spinal cord gray matter where the first synapse of the system occurs

Question 14

Sensory transduction

Answer 14

Conversion of stimulus energy to that of an electrical energy

Question 15

Merkel’s Disc

Answer 15

Nerve endings that respond to light touch and skin indentation with high tactile acuity for an object’s physical features

Question 16

Meissner’s Corpuscles

Answer 16

Skin receptor cell that responds to low frequency vibrations and fine touch

Question 17

Ruffini Corpuscle

Answer 17

Skin receptor cell that responds to gradual skin stretching and recognize hand/ finger position

Question 18

Pacinian Corpuscle

Answer 18

Skin receptor cell that responds to high frequency vibration and sudden deep pressure

Question 19

Free nerve endings

Answer 19

Axons that are near the skin’s surface that respond to pain, warmth, and cold

Question 20

Transduction for mechanosensory afferents process

Answer 20

1. As a stimulus is applied to that sensory receptor, the neuronal membrane stretches
2. Ion channels open, permitting the entry of Na ions
3. The cell membrane depolarizes enough to reach a threshold to initiate an action potential

Question 21

Center on/ Surround off receptive field

Answer 21

Touch in the center excites while touch in the surrounding inhibits

Question 22

Center off/ Surround on receptive field

Answer 22

Touch in the center inhibits while touch in the surrounding excites

Question 23

Sensory adaptation

Answer 23

The progressive decrease in a receptor’s response to sustained stimulation

Question 24

Dermatome

Answer 24

The area of the skin or body innervated by the dorsal roots of the spinal cord

Question 25

What are the 5 regions of the spinal cord?

Answer 25

Cervical, thoracic, lumbar, sacral, coccygeal

Question 26

Why is the face and head not covered by the spinal cord dermatome?

Answer 26

They are innervated by the cranial and trigeminal nerve

Question 27

Dorsal column medial lemniscus touch system

Answer 27

1. Action potential fired by a sensory neuron from the skin synapses first on a dorsal root ganglion cell 2. Action potential travels up the dorsal column to second synapse on the dorsal column nuclei 3. Action potential travels up the trigeminal nerve to third synapse on the ventral posterior nucleus in the thalamus 4. Information is relayed to the somatosensory cortex

Question 28

Trigeminal touch system to the face

Answer 28

1. Large mechanoreceptor axons from the face synapse on the principal sensory trigeminal nucleus via the trigeminal nerve 2. Action potential synapses onto the thalamus 3. Thalamus relays the information to the primary somatosensory cortex

Question 29

Cortical somatotopic map

Answer 29

A representation of how many cells in the brain are related to locations on the body (homunculus)

Question 30

Would homunculus differ from a mouse-unculus?

Answer 30

Yes; homunculus designates a large amount of brain matter to touch of the hands whereas a mouse-unculus would designate more space to the nose and whiskers

Question 31

Primary somatosensory cortex

Answer 31

S1; the brain area that receives touch information from the opposite side of the body

Question 32

Posterior parietal cortex

Answer 32

Brain area that responds to visual and somatosensory stimuli for higher processing

Question 33

Association cortex

Answer 33

Regions of the brain where different modalities combine for dual-sense processing of vision and touch

Question 34

Secondary somatosensory cortex

Answer 34

S2; the brain area that recognizes objects by their texture and size

Question 35

Astereognosia

Answer 35

The inability to recognize objects by touch caused by damage to S2

Question 36

A-delta afferent fibers

Answer 36

Myelinated neurons that send pain signals fast for the sensation of sharp, immediate pain (first pain occurring for a short amount of time)

Question 37

C afferent fibers

Answer 37

Unmyelinated neurons that send pain signals slow for the sensation of dull, aching pain (second pain occurring for a long amount of time)

Question 38

Neural pathway of pain

Answer 38

1. When cells are damaged, they release chemicals that activate free nerve endings 2. Action potentials generated in the periphery can reflexively excite blood vessels and mast cells to inflame 3. Stimulated mast cells release histamine 4. Information enters through the dorsal root and synapses on neurons in the dorsal horn 5. Pain fibers release glutamate as a transmitter and substance P as a neuromodulator in the spinal cord 6. Dorsal horn cells send information across the midline up to the thalamus

Question 39

Anterolateral system

Answer 39

Ascending pain pathway that carries temperature and pain information only

Question 40

Spinothalamic tract

Answer 40

The main pain signal pathway from the first synapse at the dorsal root ganglion cell, up the spinal cord, to the thalamus

Question 41

Spinotectal tract

Answer 41

The pain pathway where pain is controlled and inhibited by opiate release, from first synapse at dorsal root ganglion cells, then up the spinal cord, to the PAG

Question 42

Periaqueductal gray

Answer 42

PAG; the region of the midbrain involved in the release of endorphins to inhibit pain stimuli

Question 43

Spinoreticular tract

Answer 43

The pain pathway where motivation and emotion affect turning into an action response, from the first synapse at dorsal root ganglion cells, up the spinal cord, to the reticular activating system

Question 44

Neural-mediated pathways

Answer 44

Modulating pain experience from the release of endorphins or opiates

Question 45

Stress-induced analgesia

Answer 45

The suppressing of pain from stress of great injury

Question 46

Distraction or meditation-induced analgesia

Answer 46

Suppressing pain through cognitive strategies to draw away attention (ex: coping)