The Somasensory System Flashcards
How many types of systems are within the somatosensory system and what are they?
3
The exteroceptive system
The proprioceptive system
The interoceptive system
What is the role of the somatosensory system?
To perceive bodily sensations
What is the exteroceptive system responsible for?
Touch and external stimuli sensation of the skin
What is the interoceptive system responsible for?
Sensations for internal conditions such as temperature, blood pressure
What is the proprioceptive system responsible for?
The sensation of the orientation of the limbs
Name the receptors found in the dermis and epidermis. What somatosensory system would these belong to?
The cutaneous receptors. These would belong to the exteroceptive system
Explain the cutaneous receptor, free nerve ending cells.
Free nerve ending cells have no structure and are sensitive to pain and temperature
Explain the cutaneous receptor of pacinlan corpuscles.
Pacinlan corpuscles respond RAPIDLY to pressure and adapt quickly
Explain the cutaneous receptor of ruffini endings.
Ruffini endings respond and adapt GRADUALLY to pressure.
If I was to bump into an object what pressure cutaneous receptor would code for this?
Pacinlan corpuscles
If I was to sit on a chair for a long period of time what cutaneous pressure receptor would code for this?
Ruffini’s endings
What is a dermatome? What makes this system a bit more robust?
A dermatome is where the afferent, dorsal nerves on the spinal cord code for a particular skin region. It is made more robust as there is considerable overlap between each dermatome.
How many pathways from body to cortex are there in the somatosensory system? Name them.
2
The dorsal column medial-leminiscus
The anterolateral system
What pathway carries information about touch and proprioception to the cortex?
The dorsal column medial-lemniscous
What pathways carries information about pain and temperature to the cortex?
The anterolateral system
Which pathway is considered to be more important? Why? and how is this pathway harder to break?
The anterolateral system pathway. As this system codes for pain and pain is vital for survival. It is considered “indestructible” as it contains 3 tracks.
If both an excitatory and inhibitory region are stimulated at the same time, what type of firing occurs?
Baseline firing.
Why is pain important ?
As it is adaptive. It encourages learning and treatment about particular things
What cortical region is responsible for pain ?
There is no specific cortical region for pain. Whole hemispheres of the brain can be removed and pain will still be felt
However, what area is associated with the emotional responses of pain? What system does this belong to?
The anterior gingulate gyrus of the limbic system
What is the function of the periaqueductal gray (PAG)?
The PAG is the body’s built in pain reducer
How does the PAG reduce pain sensation?
electric stimulation
Receptors for opiates
Endorphins
Fill in the blanks.
Dorsal columns, ……. Medial lemnisicus, …….. , primary somatosensory cortex
Dorsal columns, dorsal column nuclei, medial lemnisicus, ventral posterior nucleus, primary somatosensory cortex
Name all 5 stages of the somatosensory receptor to cortex pathway.
Dorsal column, dorsal column nuclei, medial lemnisicus, ventral posterior nuclei, somatosensory pathway
What region on the thalamus does the somatosensory pathway project onto?
Ventral posterior nuclei
What region of the somatosensory pathway is where the medulla begins?
Dorsal column nuclei
What connects the medulla (dorsal column nuclei) to the thalamus (ventral posterior nucleus)?
Medial lemnisicus
At what stage does the triGerminal nucleus join onto the pathway?
During the medial lemnisicus
Where is the primary somatosensory cortex located?
Posteriorly to the central fissure in the postcentral gyrus.
Where is the secondary somatosensory cortex located?
Inferiorly to the primary somatosensory cortex, hidden in the lateral fissure
What is a pathway called when it runs against the typical receptor to cortex pathway? When is it used?
Centrifugal pathway. Used for pain.
Why use a centrifugal pathway to block pain?
As it reduces pain in times of intense emotional stress in order to increase chances of survival.
Fill in the blanks for the centrifugal pathway of pain.
- Periaqueductal gray
- Dorsolateral spinal cord
- Raphe nuclei
Fill in the blanks for the centrifugal pathway of pain.
1.
2. Raphe nuclei
3.
- Periaqueductal gray
3. Dorsolateral spinal cord
How is the somatosensory system organised?
Somatopically
Explain the somatosensory homunculus. What is distorted ?
Somatosensory homunculus is the map of all body part sensations controlled for in the primary somatosensory cortex. Hands, face and lips are greatly represented as they contain the highest number of sensation cells .
