Sensation and Perception

Question 1

What is Somaesthesis?

Answer 1

• Gr. Soma (body) aesthesis( to feel/perceive)
• “The bodily senses” – touch, proprioception,
  kinaesthesia, pain, itch, tickle, heat and balance
• A near sense (contrast with olfaction/vision)

Question 2

What is touch used for?

Answer 2

• Body information - posture, position, movement, pain
• Recognition and use of objects - food, tools, surfaces,
  other animals
• Communication - conveying messages, social cues
• Proper development –body growth
• Feedback in association with our movements

Question 3

What did happen in Ian Waterman’s case?

Answer 3

There is a suddenly struck down by a rare neurological illness after a flulike viral infection, No sensation of touch below the neck, and then there is a gradual onset became
increasingly weak then fell in heap on floor. No loss sensation of pain or heat. No sense of position, movement or touch below neck, slurred
speech, movement possible but appeared “drunk”.

Question 4

What did they find about Ian Waterman?

Answer 4

Autoimmune response had attacked his own sensory nerves -
judged incurable, but astonishingly reclaimed a life of
considerable mobility. Sensory neurons are critical of controlling our movement.

Question 5

What are some type of Somatosensation?

Answer 5

• Cutaneous Sensation
• Pressure
• Vibration(pressure and vibration are both mechanoreception)
• Temperature(thermoception)
• Pain(nociception)
• Proprioception
• Kinaesthesia
• Itch

Question 6

What is Lemniscal tract?

Answer 6

ascending sensory
pathway for signals for
cutaneous touch

Question 7

What is Spinothalamic tract?

Answer 7

ascending sensory
pathway for pain and
temperature

Question 8

What does touch use?

Answer 8

all peripheral nerve+Cranial nerve V(trigemeninal)

Question 9

What did Ian Waterman’s infection did not destroy?

Answer 9

trigeminal nerve

Question 10

What do we know about non-painful cutaneous sensation?

Answer 10

• The skin is the sense organ for touch
• Touch uses a variety of receptors
  located under the skin
• Specialised for pressure/stretch/vibration
• Touch receptors are “mechanoreceptors”
• Meissner’s corpuscle, Pacinian corpuscle,
  Ruffini’s corpuscle, Merkel’s disk

Question 11

What are the features of mechanoreceptors?

Answer 11

1. Sub-surface (unlike chemoreceptors)
2. Oriented vertically/horizontally
3. Different activation thresholds(because receptors to cover all possibility, activated in the different information combined)
4. Different activity rates(the ways of accumulate the information differently)

Question 12

What is Pacinian corpuscles?

Answer 12

• Deep, horizontal orientation
• Easily deformed structure, responds to
  dynamic pressure but not steady pressure(dynamic pressure refers to tickle and poke)
• Low threshold, rapidly adapting - responds
  easily but transiently to stimulation
• Respond to sudden stimuli( that’s why it is rapidly adapting)

Question 13

What is Meissner’s corpuscles?

Answer 13

• Shallow, vertical orientation
• Only in “glabrous” skin (hairless, smooth)( fingertip is great example of this)
• Mechanically deformed by light touch
• Very low threshold, shallow position,
  rapidly adapting, respond easily to
  dynamic, moderate stimulation(gripping definitely could be applied to )( e.g different textures)

Question 14

What is Ruffini’s corpuscles?

Answer 14

• Intermediate depth, horizontal
  orientation (moderate surface area)
• Mechanically deformed by stretch
• Slow response rate (2-3 Hz) allows
  them to respond to stable, low frequency
  stimulation (e.g. stretch)(e.g maybe proprioception)

Question 15

What is Merkel’s disks?

Answer 15

• Shallow, moderate surface area
• Mechanically deformed by pressure
  (but not so easily as PCs)
• Slow response rate and slowly adapting
• Respond to static pressure/touch
• static discrimination of shapes,
  edges(E.g. when holding an object)

Question 16

Where is mechanorecptors and what does it do?

Answer 16

under the skin and cause signal transduction(generates electrical signal in the sensory neuron)
Bundle of sensory nerve axons (i.e. a peripheral nerve)
heading to spinal cord*.
in case of the face, touch elicits signals in cranial nerve V
travelling to brainstem

Question 17

What does nerve fibres depend on?

Answer 17

they behave
in different ways based on Diameter,
Conduction Velocity, Myelination State
* Fibers of the A group have a large
diameter, high conduction velocity, and
are myelinated.(within this large diameter, the transduction goes quickly)
* Fibers(axons) differ based on the information
they carry and the tissues they
innervate.

Question 18

What does Myelination mean?

Answer 18

faster conduction

Question 19

What does Greater diameter mean?

Answer 19

faster conduction
Fibers of the ‘A’ group have large
diameter and are myelinated, so they
have high conduction velocity

Question 20

What type of fibre is associated with all four types of mechanoreceptors?

Answer 20

A type of A
fibers called A-beta fibers . They are Intermediate size (6–12 µm)
myelinated, and fast conduction
velocity (33–75 metres/second)

Question 21

Where does each nerve carries signals from?

Answer 21

A defined region of the
body (“dermatome”)( are the maps of all the skin on the body)

Question 22

Where does it feeds into?

Answer 22

Each nerve feeds sensory signals into the dorsal spinal cord.From there, either to brain via the ascending pathway(aka Lemniscal tract, medulla, thalamus, S1) or
just activate a reflex arc( sudden response, before your finger touch the nail).

Question 23

What is a sensorimotor loop?

Answer 23

Reflex arc (within spinal cord)
Sensory neuron (afferent information arrives from skin)
↓
Interneuron (AKA relay neuron)
↓
Motor neuron (efferent information exits out to muscles)

Question 24

What is the ascending pathway?

Answer 24

Non-painful information is relayed via Medial-Lemniscal Pathway
Sensory neuron →(first order neuron) Brainstem (second order neuron)→ Thalamus →Third order neuron) Somatosensory cortex

Question 25

How does somatosensory cortex involve?

Answer 25

* A long, thin strip of cortex extending (roughly) from ear to ear * 2 major subdivisions: SI – receives input from thalamus: SI is divided further into Brodmann’s 3a, 3b, 1, 2 SII – receives input from thalamus and SI Then on to other cortical areas

Question 26

What is the study on median nerve stimulation?

Answer 26

Purpose: to use electrical median nerve stimulation in healthy right-handed volunteers, and examine activity in cortical regions using fMRI, to test the hypothesis that S1(left side of the brain) and S11( left AND right side of brain Insula) will be activated. Effects of selective attention were also studied (count # of omitted pulses during stimulation– attention directed to the stimulus). When you focus on it, the sensation is different, that's why you put the variables of selective attention.

Question 27

Will selective attention influence the experiment result?

Answer 27

Enhanced fMRI responses in the contralateral SII but did not change activation in SI.

Question 28

What is Sensations that arise from inside the body essential for?

Answer 28

Requires a physical stimulus from the internal environment (e.g. mechanical stretch/tension in muscles). - Posture - Large scale movement (walking, reaching) - Small scale movements (haptic exploration & use) - Turning & counterbalance (orienting, balancing)

Question 29

What is the difference between kinesthesis and proprioception?

Answer 29

Feel of movement: kinesthesis Position of movement: proprioception

Question 30

What are the three mechanisms of kinaesthesia and proprioception?

Answer 30

Muscle spindles monitors muscle length, Golgi tendon organs monitors muscle tension, joint receptor neurons monitors joint movement. All afferent sensory neurons from these receptors travel to the spinal cord

Question 31

What is the route of sensory receptors?

Answer 31

1. Sensory receptors are activated, signal transduction occurs 2. Neural signal is relayed towards the brain, via thalamus, then to primary cortex and other cortical areas (many involved in associations, i.e., perception)