Touch & Pain Flashcards
Why are receptors that respond to touch found?
They are embedded in the dermal layers of the skin
What are the types of receptors that respond to touch?
Pacinian corpuscles, Meissen corpuscles, Merkel’s disks and Ruffini endings
What do receptors do?
They have ion channels that open in response to mechanical deformation which triggers action potentials
What do Pacinian and Meissen corpuscles respond best to?
Rapidly changing indentations like sense of vibration and flutter
What do Merkel’s disk respond best to?
Sustained indentation of the skin like sense of pressure
What does Ruffini ending respond best to?
Slowly changing indentations
What is receptive field?
Area of skin to which each individual receptor responds
Which has a larger receptive field, Pacinian or Meissner corpuscles?
Pacinian corpuscles
How do receptors work?
Once they detect a stimulus, the receptors send impulses along the sensory nerves that enter the dorsal roots of the spinal cord. The axons connecting touch receptors are large myelinated fibres that convey information through the periphery towards the cerebral cortex extremely rapidly
How and what is the speed at which cold, warmth and pain are detected?
They are detected by thin axons with “naked” endings, which transmit more slowly
What is special about temperature receptors?
They show adaptation
How are touch relayed?
There are relay stations for touch in the medulla and the thalamus, before projection on the primary sensory area in the cortex call3d the somatosensory cortex
Which hemisphere is the right side of the body represented in and why?
The left hemisphere because the nerves crosses midline
What happens at the somatosensory cortex?
The input from the body is systematically mapped across the somatosensory cortex to form a representation of the body surface
What is the packing density like in the somatosensory cortex compared to our actual body?
In the somatosensory cortex, the packing density of neurons is uniform, which for body, the density is not uniform. Therefore, the map of the body surface on the cortex is very distorted
What is sensory homunculus?
Topographic distribution of sensory distribution of body found in the cerebral cortex
How to test different sensitivity across the body?
Using two-point discrimination test
Where is the ability to perceive fine details most highly developed?
Tip of fingers and lips
What is touch also involved in?
Active control of movement
Why is touch involved in the active control of movement?
Neurons in the motor cortex controlling muscles in your arm that move your fingers get sensory input from touch receptors in the finger tips
When do cross-talks happen between sensory and motor systems?
It begins at the first relays in spinal cord, including proprioceptive (stimuli produced) feedback on to motor neurons and continues at all level of the somatosensory system
Where are the primary cortex and motor cortices located relative to each other?
They are right beside beach other
What is crucial for the sense of touch?
Active exploration
Does the identification of textures or objects by touch involve one or different regions of cortex?
It involves different regions
