Physiology of Somatosensation

Question 1

Somatosensation

Sensory information from skin, muscles, organs, and joints Information about skin and organs

Information about skin and organs

Answer 1

• Pain: Damage/inflammation and temperature
• Pressure and vibration
• Texture and shape
• Length and degree of stretch
• Tension and contraction
• Joint angle, position, movement

Question 2

Sensory Receptors in the Skin

Answer 2

Question 3

• *Determinants of Stimulus Localization**
• *& Sensory Acuity**

Size of the Receptive Field

Density of Innervation

Convergence

Lateral Inhibition

Answer 3

• Size of the Receptive Field
• Density of Innervation
• Convergence
• Lateral Inhibition

Question 4

spatial region where application of stimulus causes a sensory neuron to respond

Answer 4

receptive field

Question 5

size of the receptive field influences the precision with which stimuli can be localized

Answer 5

spatial resolution

Question 6

Receptive Field Size & Density Influences Sensory Acuity

Answer 6

Question 7

Stimuli applied to the center of receptive field has a (smaller/larger) impact on the receptor potential

Answer 7

larger

Question 8

2 points must be separated by greater distance in order to be distinguishes as separate

2 points can be closer together and still be distinguished as separate

Answer 8

Large Receptive Fields

Small Receptive Fields

Question 9

Receptive field _____ and _____ varies across the body surface

Areas with sensory receptors that have small receptive fields show better ______/________ in two-point discrimination

Answer 9

size and density

resolution/acuity

Question 10

Area of the body with lowest two-point discrimination threshold

Area of the body with largest two-point discrimination threshold

Answer 10

Lowest: Fingers (extremities)

Largest: Calf (limbs)

Question 11

influences sensory acuity

Answer 11

receptor field convergence

Question 12

Capacity of excited neuron to reduce its neighbors activity

Answer 12

Lateral Inhibition

Question 13

Lateral inhibition provides

Answer 13

high localization precision

Question 14

Receptor type

Fiber type

Modality

Muscle Spindles

Golgi Tendon Organ

Joint: pacinian and Ruffini

Meissner’s corpuscle

Merkel disk

Pacinian corpuscle

Ruffini ending

Hair- follicle

Free nerve ending

Answer 14

Receptor type

Fiber Type

Modality

Muscle Spindles

Ia/II, Aα/Aβ

Muscle length and velocity

Golgi Tendon Organ

Ib, Aα

Muscle tension

Joint: pacinian and Ruffini

II, Aβ

Joint movement and angle

Meissner’s corpuscle

II, Aβ

Stroking, fluttering

Merkel disk

II, Aβ

Pressure, texture

Pacinian corpuscle

II, Aβ

vibration

Ruffini ending

II, Aβ

Skin stretch

Hair- follicle

II/III, Aβ/Aδ

Stroking, fluttering

Free nerve ending

III/IV, Aδ/C

pain, temperature, crude touch

Question 15

Fiber Type

Diameter (micrometer)

Conduction Velocity (m/sec)

I, Aα

II, Aβ

III, Aδ

IV, C

Answer 15

Fiber Type

Diameter (micrometer)

Conduction Velocity (m/sec)

I, Aα

13-20

75 – 120

II, Aβ

6-12

35 - 75

III, Aδ

1-5

5 - 35

IV, C

<1.5

0.5 - 2.0

Question 16

Discriminative Touch, Vibration & Proprioception

& Proprioception

Answer 16

Aα and Aβ fibers

Question 17

Crude Touch, Pain & Temperature

Answer 17

Aδ and C fibers

Question 18

•Cell bodies located in dorsal root ganglia, trigeminal ganglion, or mesencephalic nucleus

Answer 18

vFirst Order Neuron (1°) (Primary Afferent Neuron)

Question 19

•Cell bodies located in ipsilateral, dorsal horn of spinal cord, ipsilateral medulla, or ipsilateral pons.•Cross the midline to the contralateral side.

Answer 19

vSecond Order (2°) Neuron

Question 20

•Cell bodies located in the contralateral VPL or VPM nucleus of the thalamus.•Project to the somatosensory regions of the cerebral cortex.

Answer 20

vThird Order (3°) Neuron

Question 21

1° Afferent Neurons

Shape:

Cell Body Locations:

Answer 21

Shape: Pseudo unipolar neurons

Cell Body Locations:

• Dorsal root ganglion
• Trigeminal ganglion
• Mesencephalic nucleus

Question 22

Answer 22

Question 23

Tactile, Pain & Temperature Paths for Face

Answer 23

Question 24

Tactile, Pain & Temperature Paths for Face