Special Senses Lecture 1

Question 1

What is the somatosensory system?

Answer 1

part of the sensory system concerned with the conscious perception of touch, pressure, pain, temperature, position, movement, and vibration which arise from the muscles, joints, skin and fascia

Question 2

What is somatic sensation?

Answer 2

sensation from the skin, muscles, bones, tendons and joints (“relating to the body”

Question 3

What is somatosensation?

Answer 3

Somatosensation refers to the process that conveys information regarding the body surface and its interaction with the environment

Question 4

What are the submodalities of somatosensation?

Answer 4

1. Touch
2. pressure
3. temperature
4. pain

Question 5

What receptors are responsible for proprioception?

Answer 5

Mix of joint tendon stretch receptors

Question 6

The specialized receptor cells generate graded potentials called _______ potentials in response to a stimulus

Answer 6

The specialized receptor cells generate graded potentials called receptor potentials in response to a stimulus

Question 7

What is the difference between graded potentials and action potentials?

Answer 7

Graded potentials are small depolarizations; if there are enough of these small depolarizations, they can end up generating an action potential

Question 8

Name the receptor that responds to each of the following modalities:

1. Respond to light:
2. Respond to pressure:
3. Respond to temperature:
4. Respond to sound:

Answer 8

Name the receptor that responds to each of the following modalities:

1. Respond to light: Photoreceptors
2. Respond to pressure: mechanoreceptors
3. Respond to temperature: Thermoreceptors
4. Respond to sound: auditory receptors

Question 9

What are five different types of somatosensory (touch and pressure) receptors?

Answer 9

1. Meissner’s corpuscles
   
   • mechanoreceptor that responds to touch and pressure
   • Rapidly adapting
2. Merkel’s corpuscles
   
   • respond to touch and pressure
   • slowly adapting
3. Free neuron ending
   
   • nociceptor
   • thermoreceptor
   • mechanoreceptors (slow-adapting)
4. Pacinian corpuscle
   
   • vibration and deep pressure
   • rapidly adapting
5. Ruffini corpuscle
   
   • responds to skin stretch
   • slow-adapting

Question 10

Which of the touch/pressure receptors are slowly adapting? Which are rapidly adapting?

Answer 10

Slow-Adapting:

• Merkel’s
• Free Neuron ending
• Ruffini corpuscle

Rapidly-adapting:

• Pacinian corpuscle
• Meissner corpuscle

Question 11

How are afferents (mechanoreceptors or somatosensory receptors) activated?

use Meissner’s or Merkel’s as example

• Poke on arm > activates ______ > _____ channels in distal end of receptor open and _____ flows down its concentration gradient into the afferent neuron (or sensory receptor) = _________ _______ of the sensory receptor

Answer 11

Meissner’s and merkel’s corpuscles are somatosensory receptors that are activated by touch or pressure (mechanoreceptors)

• Poke on arm > activates mechanoreceptor > cationic channels in distal end of receptor open and sodium flows down its concentration gradient into the afferent neuron (or sensory receptor) = graded depolarization of the sensory receptor

Question 12

What are the two types of sensory receptors?

Answer 12

a) sensory receptor is located directly on the afferent fibre

• sesnory receptor is located on the afferent neuron and the afferent neuron travels to the spinal cord
• Na+ flows into the cell resulting in a graded depolarization; AP is not necessarily generated bu that equivalent of an EPSP is generated in the distal end of the receptor cell which is located on the afferent

b) The sensory receptor is located on a specialized receptor cell
* Poke in the arm activates mechanoreceptors > cation channels open > Na+ flows in > graded depolarization > NT released > binds to afferent neuron > spinal cord

Question 13

Graded potentials are the equivalent of ______ and are small, longer lasting _____ at the location of the sensory receptor in the periphery

Answer 13

Graded potentials are the equivalent of EPSP’s and are small, longer lasting depolarizations at the location of the sensory receptor in the periphery

Question 14

The afferent fibre of a sensory receptor has a number of _______

Answer 14

Receptor terminals

• the more receptor terminals activated = the more ap’s

Question 15

What are three important factors that affect our ability to localize a stimulus?

Answer 15

• Density of innervations
• Receptive field size
• Overlapping receptive fields