cutaneous senses pt 1

Question 1

two parts of somatosensory system

Answer 1

1. proprioception- perception of position, movement and effort from muscles, tendons and joints
2. cutaneous senses- perception of touch and pain from stimulation of skin

Question 2

skin-

Answer 2

epidermis- outer layer made up of dead skin cells
dermis- lower layer containing mechanoreceptors, responsive to pressure, stretching, vibration
2 types: hairy (thick) and glabrous (thin)

Question 3

merkel receptors

Answer 3

fire continously when stimulus is present
- SLOW ADAPTING
perceive fine details, shape and texture

Question 4

meissner corpuscles

Answer 4

fire only when stimulus is applied and removed
- RAPIDLY ADAPTING
perceive hand - grip control, motion

Question 5

two types near skin surface with small receptive field

Answer 5

merkel and meissner

Question 6

two types deep below skin surface w/ large receptive field

Answer 6

ruffini and pacini

Question 7

ruffini

Answer 7

fire continously to stimulation
- SLOW ADAPTING
perceive stretching of skin

Question 8

pacinian corpuscles

Answer 8

fire only when stimulus is applied and removed
- RAPIDLY ADAPTING
perceive vibrations and fine textures

Question 9

how many mechanoreceptors are in the hand

Answer 9

17,000

Question 10

somatosensory pathways

Answer 10

nerve endings
dorsal root ganglion
spinal cord
- medial lemniscal (large, proprioception and touch)
CROSSES OVER LATER
- spinothalamic (small, temperature and pain)
IMMEDIATE CROSS OVER
primary somatosensory cortex S1

Question 11

primary somatosensory cortex: S1

Answer 11

sensory homunculus

• somatotopic map and cortical magnification
• mechanoreceptors that we make use of more have more representation

Question 12

tactile acuity

Answer 12

raised pattern identification is used to determine smallest size identified

• braille
• two point threshold
• grating acuity: grooved stimulus indicate orientation

Question 13

fingertips tactile acuity

Answer 13

small receptive field and high density merkel receptors
- high discriminability
larger areas of cortical tissue
- magnification

Question 14

vibration of skin

Answer 14

pacinian corpuscle

• nerve fibers respond best to high fibration
• structure of receptor is responsible for response

Question 15

duplex theory of texture perception

Answer 15

perception of texture depends on two cues:
1. spatial cues
- rough surfaces
- determined by size, shape and distribution of larger surface elements
MERKEL RECEPTORS
2. temporal cues
- fine surfaces
- determined by rate of vibration as skin is moved across finely textured surface
PACINIAN CORPSCULES

Question 16

adaptation experiment

Answer 16

skin is adapted to
- 10 Hz stimulus to adapt meissner corpuscle
- 250 Hz stimulus to adapt pacinian corpuscle
only pacinian affected perception of fine textures