Chapter 11: The Body Senses and Movement Flashcards
What are the four somatosensory systems?
Proprioception: kinesthesia, senses movement, action and location (what is your body doing and where is it)
Skin senses: senses condition at the bodies surface (touch and temperature)
Vestibular system: senses body position and movement
Interoceptive system: senses states of our internal organs (acts in background)
What sense is proprioception? What happens if you are deficient in this system?
Sense that informs us about the position and movement of our body and limbs. Its key to many basic functions such as maintaining posture and moving limbs and grasping/locating objects. If you are deficient in this system then you would be floppy and ragdoll like, you would have to rely heavily on other senses such as visual, and your body would fully collapse in dark environment as you have no visual input
What does the skin sense system detect? What is important about their receptors and pathways and what are they called? What does this system not detect?
Detects touch, warmth, and cold, as well as pain, includes tickling and touching. They are distinct with their own receptors and pathways to the brain which may be called a “labeled line”. This system does not detect “wetness”, you can only perceive it not sense it, instead you sense the temp changes
What are the types of receptors in the skin senses system?
Free nerve endings: processes at the ends of neuronal dendrites, at the surface of the skin to absorb stimuli, they detect warmth, cold, and pain
Encapsulated nerve endings: more complex structures enclosed in a membrane, detect touch, deeper in the skin than FNE
What are the four types of encapsulated nerve endings?
Meissner’s corpuscles
Merkel’s discs
Ruffini endings
Pacinian corpuscles
What are the Meissner’s corpuscles and Merkel’s disks? Where are they mostly located?
They are both encapsulated receptors, the MC respond with a brief burst of impulses, MD gives more sustained responses, and they detect texture and fine detail
They are mostly located in the fingers and lips, as well as places that are more sensitive such as hands and feet
What are the Pacinian corpuscles and Ruffini endings? Are they deep in the skin or near the surface?
They detect the stretching of skin which contributes to perception of shape of grasped objects. They are deeper in skin layers.
What are the types of free nerve endings?
Temperature receptors: members of the transient receptor potential (TRP) family of protein ion channels
Pain receptors: which respond to three different types of pain which are thermal (hot and cold pain, we have not identified the cold receptors), as well as chemical, and finally mechanical (not identified)
True or False. The number of receptors in the skin correlates to number of neurons in the brain.
TRUE
What is involved in the vestibular sense? What structures are involved in this system?
Helps us maintain balance, provides info about head position and movement.
Semi-circular canals: we have 3 of them that respond to and detect movement in three directions
Saccule: monitor head position in relation to gravity (with the ventricle)
Cupula: have tufts of hair within them that bends in response to movement speed/direction, and only tells us about acceleration of our bodies not the deceleration
What happens when the vestibular system is not working?
You get vertigo and sea sickness type feeling due to disruptions in the semi-circular canal
What is a dermatome? What phenomena does this explain?
A segment of the body powered by a single spinal nerve, sensory neurons will feed into one nerve, this explains why when you injure your spinal cord you cannot feel anything below it
Where does information coming into the CNS via spinal/cranial nerves cross the midline? Where are they sent to?
They cross the midline in the medulla, and they are then sent to the thalamus and then sends it to the somatosensory cortex.
What happens in the somatosensory cortex? What is it?
It is the projection areas for the body sense neurons, it is located in the parietal lobes just behind the primary motor cortex and the central sulcus
What is a somatotropic map? Where is it located?
Representation of the body in the somatosensory cortex, with adjacent body parts represented in adjacent parts of the cortex
What are the parts of the somatosensory cortex?
Primary somatosensory cortex (4 areas), secondary somatosensory cortex
What is the purpose of the primary somatosensory cortex?
It contains 4 areas, each containing a somatotropic map, and plays role in processing sensory info from the body. Information is processed from the thalamus into two subareas, some info is extracted, then sent to the other two areas, and then this information is passed to the secondary somatosensory cortex
What is the purpose of secondary somatosensory cortex?
Integrates information from both sides of the body, neurons in this area are responsive to stimuli that have acquired meaning (integrates info from other areas and sends info to other areas to gain meaning)
Also sends connections to the temporal lobe which contains the hippocampus which may form somatosensory memories
What happens in the posterior parietal cortex?
This is an association area that brings together the body senses, vision and hearing. It integrates the body with the world by determining the bodies orientation in space.
What is body integrity identity disorder (apotemnophilia)? What causes it?
Condition where individuals with no apparent brain damage or disorder are convinced that a limb does not belong to them. It appears to happen randomly and we have no been able to pinpoint any brain damage that causes it. When the specific limb is touched there is no response in the superior parietal area
In BIID, skin conductance in response to stimulation is doubled in the limb, what does this suggest?
That there is an intense emotion about the limb, therefore we have emotions about the limb BUT no perception
What is an out-of-body experience? What could it be caused by? Why are they hard to study?
An illusion where a person hallucinates seeing themselves/ their body from an outsiders POV, from a different location. You are conscious but watching your body from another location.
Causes could be seizures from epilepsy that affect the temporal-parietal junction, intentional electrical stimulation, or TBI. HOWEVER, anyone can experience them.
They are hard to study because they are difficult to ethically induce.
How does pain begin? What is the bodies first response to pain?
Pain begins when the free nerve endings in the skin are stimulated by intense pressure/temperature either by tissue damage or various chemicals.
The bodies first response is to release an inflammatory soup of molecules to combat the pain such as cytokines, chemokines, NT, histamine, proteins, lipids. Some of these molecules stimulate the pain receptors, some cause pain symptoms or increase the excitability of neurons.
Why do some molecules in the inflammatory soup increase the excitability of neurons? Why is this adaptive?
They increase the excitability of neurons therefore enhancing their sensitivity to stimuli. This means that now, less painful stimuli is required for us to feel pain as the threshold of the neuron is lowered. This prevents us from hurting ourselves further or exacerbating an existing injury.
