Somatosensation (P1) Flashcards
(22 cards)
What is somatosensation?
Somatosensation is the sensory perception of bodily feelings, including kinaesthesia, pain, itch, tickle, and heat.
What are the functions of touch?
Provides body information: posture, position, movement, pain.
Aids in recognition and use of objects: food, tools, surfaces, animals.
Facilitates communication: conveying messages, social cues.
Supports proper development: body growth.
Provides feedback associated with our movements.
Who is Ian Waterman (IW) and what is his case study?
an Waterman developed a rare neurological illness after a viral infection, losing sensation below his neck. He had no sensation of touch but retained the ability to feel pain and heat. Despite immense concentration and attention, he relearned motor skills like walking, though movements appeared “drunk.”
What are the two main ascending sensory pathways in the somatosensory system?
Lemniscal tract: For fine touch, vibration, and proprioception.
Spinothalamic tract: For pain and temperature.
What is the role of mechanoreceptors in the skin?
Mechanoreceptors are responsible for detecting different types of touch, such as pressure, vibration, stretch, and texture. They are located in the dermis and have different activation thresholds and orientations.
Name the four primary mechanoreceptors in the skin and their functions.
Meissner’s corpuscles: Shallow, respond to light touch, rapidly adapting.
Merkel’s disks: Shallow, respond to static pressure, help in shape and edge discrimination, slow adapting.
Ruffini’s corpuscles: Intermediate depth, respond to stretch, slow response.
Pacinian corpuscles: Deep, respond to dynamic pressure, rapidly adapting.
Example with Pacinian Corpuscles
- Pacinian corpuscles
Example: Feeling the vibration of a phone vibrating in your pocket or detecting the sensation when a person taps on your shoulder.
Explanation: These receptors are sensitive to deep pressure and rapid changes in texture, like when you touch a textured surface briefly or experience quick pressure changes.
Example Meissners
Meissner’s corpuscles
Example: Feeling the sensation when you touch a soft fabric like velvet or when you rub your fingers over a smooth surface like glass.
Explanation: Meissner’s corpuscles are responsible for detecting light touch and texture, especially in areas like fingertips where sensitivity to touch is high.
example Ruffinis
Ruffini’s corpuscles
Example: The sensation of your skin stretching when you open your hand wide or when your fingers are slowly pressed together.
Explanation: These receptors respond to continuous pressure or stretching, allowing you to perceive things like the stretch in your skin during hand movements or grasping.
example Merkels
Merkel’s disks
Example: The feeling of holding an object with distinct edges, such as a book or a pen.
Explanation: Merkel’s disks are responsible for detecting sustained pressure and help you feel and discriminate the shape, texture, and edges of objects, such as when you’re holding or gripping something.
What is the function of muscle spindles and Golgi tendon organs and Joint Receptor neurons?
Muscle Spindles
* Muscle length & stretch
* Trigger stretch reflex, maintain tone/posture
**Golgi Tendon Organs **
* Muscle tension/force Muscle-tendon junction
* Prevent overstretch by inhibiting contraction
Joint Receptors
* Joint angle & movement Joint capsules/ligaments
* Sense joint position, protect from overextension
How do sensory signals travel from the skin to the brain?
Signals travel through the dorsal root into the spinal cord, with fine touch and proprioception following the lemniscal pathway and pain and temperature following the spinothalamic tract. The signals cross over in the brainstem, ascend to the thalamus, and are relayed to the somatosensory cortex for processing.
Lemniscal tract = cross over in the brainstem (medulla oblongata)
Spinothalamic tract cross over in the spinal cord
What is the role of the somatosensory cortex?
The somatosensory cortex processes sensory input, receiving information from the thalamus and further divided into areas for specific sensory functions. It also integrates sensory input for perception and action.
What is selective attention, and how does it affect sensory processing?
Selective attention allows us to focus on relevant somatosensory information (touch, pain, temperature) while filtering out irrelevant stimuli. This process is crucial for efficient sensory processing and behavior, as it prevents our brains from being overloaded with all incoming sensory information.
Selective attention boosts activity in the secondary somatosensory cortex (SII) while not affecting the primary somatosensory cortex (SI). It helps prioritize relevant sensory information for processing.
What is the posterior parietal cortex responsible for?
The posterior parietal cortex is essential for multiple functions, including attention, body awareness, navigation, and integrating spatial sensory information. Lesions in this area lead to deficits in these functions, including neglect.
What type of touch information is processed by the Lemniscal tract?
The Lemniscal tract processes fine touch, vibration, and proprioception signals. These signals ascend through the dorsal column-medial lemniscal pathway to the brain.
What is the main difference between the Lemniscal tract and the Spinothalamic tract?
The Lemniscal tract carries fine touch, vibration, and proprioception, while the Spinothalamic tract carries pain and temperature signals.
How does the somatosensory cortex process touch information?
The primary somatosensory cortex (SI) receives input from the thalamus and processes touch signals. The secondary somatosensory cortex (SII) receives information from SI and is involved in higher-level integration, such as attention and awareness.
What sensory pathway is responsible for carrying pain signals to the brain?
Pain signals are transmitted via the Spinothalamic tract. The signal crosses over at the spinal cord and then travels to the thalamus and primary somatosensory cortex for processing.
What happened in the case of Ian Waterman, and how does it relate to somatosensation?
an Waterman lost the sensation of touch below his neck due to an autoimmune response after a viral infection. Despite having no touch sensation, he retained pain and heat perception and learned to compensate through immense concentration.
What is proprioception, and how does it relate to kinesthesia?
Proprioception is the sense of body position, while kinesthesia refers to the feeling of movement. Both are critical for posture, body orientation, and movement control, monitored by muscle spindles and Golgi tendon organs.
What is a reflex arc, and how does it function in somatosensation?
A reflex arc is a simple neural pathway involving a sensory neuron, interneuron, and motor neuron. It allows for an immediate motor response to stimuli, like pulling your hand away from a hot stove before feeling pain.
