Lecture 22 - The Somatosensory System

Question 1

proprioception

Answer 1

ability to sense where your body in physical space

The ability to sense the position of the
body and limbs.

is our (static) perception of our bodies,caused by feedback from the skin, muscles, and joints.

Question 2

cutaneous touch receptors

Answer 2

tactile function

Question 3

What do our skin and touch sensations do?

Answer 3

• Protect inner organs and systems
• Maintain homeostasis (body temperature, tracks what’s coming in and out)
• Provide strong social feedback
• Enable planned motion
• Detect objects and textures

Question 4

three components to the somatosensory

system

Answer 4

1) proprioception
2) kinesthesis
3) cutaneous sense

Question 5

kinesthesis

Answer 5

The ability to sense movement of the body and limbs: knowing where and how fast body parts are during movement, how is my body movement occurring, where is it going? how am i maintaining that action?

is is the tracking of our body as it is in motion.
• Information is sent to the spinal cord and brain from Golgi tendon organs (monitor tension) and muscle spindles (monitor stretch and speed). These are proprioceptors.

• Motor signals return to the muscle to execute both planned and automatic movements.

Question 6

cutaneous senses

Answer 6

Perception of touch and pain from direct

stimulation of the skin.

Question 7

Golgi tendon organs

Answer 7

monitor the tension in the tendons

muscles are connected to bones via tendons and have a certain amount of expected tension

if tension becomes too great it will inhibit muscle from contracting to protect it from tears when doing heavy lifting

Question 8

balance is inherently multisensory

Answer 8

using constant visual feedback

worse at balancing with eyes closed

Question 9

muscle spindles

Answer 9

are structures that are deep inside of muscle and monitor stretch and speed (rate at which it’s stretching)

monitors the amount of contraction in a muscle and the rate that it is contracting

Question 10

proprioceptors

Answer 10

both the (1) Golgi tendon organ and (2) muscle spindles help you maintain a sense of your body, where it is, and how it’s moving

Question 11

what would happen if you lost proprioceptors?

ian waterman

Answer 11

had a virus that completely devastated his PNS for proprioception: can no longer sense where his body is and has no sense of touch

couldn’t move his body at all because his body didn’t know where it was

Ian Waterman has no sensory input from the
proprioceptors in his muscles and joints. He also has no information from the mechanoreceptors in his skin that would respond to the physical objects in his environment. However, he does still feel pain and temperature. [Single dissociation - pain information travels through a diff pathway than proprioceptors and mechanoreceptors]

He was able to compensate with the use of visual information to update his brain on his body’s position (re-map proprioceptive sense). He has to be constantly visually aware of where is body is in order to move. This shows the underlying multimodal nature of proprioception (and cutaneous senses as well).

Question 12

mechanoreceptors

Answer 12

provide detail about items we touch and hold.

texture: how smooth, the fine detail (ridges)

These cutaneous receptors include:

• Merkel receptors – fine detail
• Meissner corpuscles – handgrip
• Ruffini cylinders – stretching of skin (opening of the hand)
• Pacinian corpuscles – rapid vibration, fine texture

Question 13

merkel receptors

Answer 13

fine detail: pad of the finger on an object with a ridge, you can still feel ridge as the finger stays there

respond constantly when pressure is being applied to the skin: stops firing when pressure stops

slow adapting: responds best when stimulus is constant, takes a long time to selectively adapt

close to the surface

Question 14

meissner corpuscles

Answer 14

close to the surface

responds to changes: fires only when a stimulus is first
applied and when it is
removed.

• Rapid adapting –
responsible for controlling hand-grip:

if you had something really heavy

Question 15

Ruffini cylinders

Answer 15

fires continuously to
stimulation.

• Slow adapting – respond to continuing presence of the stimulus: associated with perceived stretching of the skin
around objects and gross movements.

as you move your hand the amount of stretch in the skin will change: pressure, tension, ect..

Question 16

Pacinian corpuscles

Answer 16

rapid vibration, fine texture due to these vibrations

fires only when
a stimulus is first applied and when it
is removed.

• Rapid adapting – associated with
sensing fast vibrations and fine texture.

Question 17

both merkel receptors and meissner corpuscles have…

Answer 17

…..small response
fields and high acuity (sorta like cones in high acuity vision)

both are near the surface of the skin

Question 18

Ruffini cylinder and Pacinian corpuscle BOTH….

Answer 18

are deeper in the skin

have large receptive fields with low acuity.

Question 19

difference between high and low acuity

Answer 19

high acuity you can tell that two points on the skin are close or far apart whereas low acuity you can’t

Question 20

Which mechanoreceptor seems most useful for kinesthesis?

Answer 20

Ruffini cylinders: the stretching the skin

if you’re moving in space and your skin is moving in diff places that’s providing feedback of where and how your body is moving

Question 21

Measuring tactile acuity

Answer 21

Two-point threshold

Grating acuity

Raised pattern identification

Question 22

Two-point threshold:

Answer 22

use two probes and find the min separation between those two points where you can still detect that there are two things

at one point they will feel like just one probe

minimum separation needed between two
points to perceive them as two units.

” one point or two? “

Question 23

Grating acuity

Answer 23

horizontal or vertical

placing a grooved stimulus on the skin and asking
the participant to indicate the orientation of the grating.

“grating vertical or horizontal?”

Question 24

Raised pattern identification

Answer 24

using letters or simple shapes to

determine the smallest size that can be identified