Section 6 Flashcards
What is proprioception?
Refers to our capacity to know the position of the different parts of our bodies
What do somatosensory receptors detect?
Cutaneous or muscular changes produced by mechanical, thermal, or sometimes chemical stimuli, and to convey this information to the CNS
Where are cell bodies of somatosensory receptors located?
In the dorsal root ganglion
What do we call the region of the skin that is innervated by a specific nerve?
Dermatoma
Cutaneous or subcutaneous receptors have receptive fields that are defined by ____________
The area of the skin where a stimulation can elicit a response in that receptor
How do you achieve a greater capacity to identify the precise location of an object touching the skin?
By having a high concentration of receptors in that area which have small receptive fields
How does the size of a somatosensory neurons receptive field vary based on where the receptor is?
Receptors located deeper in the skin will tend to have larger receptive fields than the ones located on the surface
Explain why several somatosensory receptors can be simultaneously activated even if the stimulus is very small?
The receptive fields of somatosensory receptors overlap
What is tactile acuity?
The capacity to detect the most delicate features of a stimulus
What technique would you use to assess tactile acuity?
Two-points threshold technique
Describe the two-points threshold technique
Typically assessed by applying two points of a drawing compass on the skin and asking participants if they perceive one of two points
The smaller the distance required to discriminate two points, the _______ (smaller/greater) the tactile acuity
greater
Regions such as the face and hands have much _______ (smaller/greater) tactile acuity compared to other regions such as the back and legs
greater
What are the two general types of somatosensory receptors?
Fast-adapting (FA) and slow-adapting (SA)
Describe fast-adapting somatosensory receptors
Respond strongly to the onset of a mechanical stimulus, but then quickly decrease their firing rate even if the stimulus is maintained
List three characteristics of FA type I receptors
- attached to Meissner corpuscles
- have smaller receptive fields
- mostly found in the fingertips and are extremely sensitive to movement and low frequency vibration, which is important for perceiving slip and maintaining grip when manipulating objects
List three characteristics of FA type II receptors
- Attached to Pacinian corpuscles that absorb much of the mechanical energy applied on the skin
- Located deeper in the skin and therefore have large receptive fields
- Most sensitive to high frequency vibration on the skin, which is important for perceiving fine textures or manipulating tools
Describe slow-adapting somatosensory receptors
Their response is sustained throughout the application of the mechanical stimulus
List three characteristics of SA type I receptors
- attached to Merkel cells
- located closer to the surface of the skin and therefore have small receptive fields
- play an important role in perceiving pattern, texture, and shape
List three characteristics of SA type II receptors
- attached to Ruffini endings
- have large receptive fields
- responsive to stretching of the skin, which can be useful for perceiving hand conformation
What are proprioceptors?
Convey information on the mechanical forces originating from body movements and posture in order to inform on the position of limbs and other body parts
Where are proprioceptors located?
muscle spindles, Golgi tendon organ, and ligaments
What are nociceptors?
They respond to pain and temperature throughout the body, and have never endings that are free from any specialized endings
Why do nociceptors have a high response threshold?
Because there is no reason for them to be activated by stimulus intensities that are too low to cause injury