w-6 touch and proprioception Flashcards
(42 cards)
cell bodies of sensory neurons (primary afferents) are located where?
the dorsal root ganglia and the trigeminal ganglia
these are part of the peripheral nervous system
what part of the spinal chord is used to send sensory info?
send into the dorsal horn of the spinal chord through the dorsal root entry zone
what is different about sensory neurons?
- continuous peripheral and central components (they dont have seperation between their dendrites and their soma)
- connects to cell body by a single process
- pseudounipolar
- AP doesnt necessarily have to travel through cell body
what is a neurite?
any extension off of a neuron
how does transduction in a mechanosensory afferent occur?
the membrane is stretched, the ion channels open, Na+ comes in and creates a graded potential that is proportional to the amount of stretch until it reaches the AP threshhold
what is the receptor type and the afferent axon types for proprioception?
the recptor type is a muscle spindle and the afferent axon type is Ia and II
what are the receptor types and the afferent axon type for touch?
the receptor types are merkel, meissner, pacinian, and ruffini cells and the afferent axon type is AB (beta)
what is the receptor type and the afferent axon type for pain and temperature?
the receptors are free nerve endings and the afferent axon type is A gamma
what is the receptor type and the afferent axon type for pain, temperature, itch, and non-discriminative touch?
the receptor types are unmyelinated free nerve endings and the afferent axon type is C
afferents are often surrounded by ___________ ____/_______________ that help tune the afferent fiber. what do they do?
- receptor cells/encapsulation
- they often reduce the threshold for action potential (increase sensitivity)
free nerve endings mean…
there is no receptor/encapsulation
mechanoreceptors respond to what kind of stimulus?
both the slowly adapting (via slowly adapting receptors that sense the entire stimulus with slow adaptations) and dynamic (via dynamic receptors that fire only at the onset and offset of the stimulus) qualities of a stimulus
what could potentially change the firing pattern of a mechanoreceptor
- firing patterns can sometimes be attributed to recptor cells
- rapidly adapting afferents associated with pacinian corpuscles can become slow adapting if receptor cells are removed
What do somatosensory afferents carry?
Information from the skin to central circuits
Where are the cell bodies of sensory neurons located?
In the dorsal root ganglia and trigeminal ganglia
How do mechanosensory afferents enter the spinal cord?
Through the dorsal root and bifurcate into ascending and descending branches
Where do ascending branches of mechanosensory afferents project?
Ipsilaterally through the dorsal column to dorsal column nuclei in the medulla
What do second-order neurons in the dorsal column nuclei do?
Send axons to the somatosensory thalamus
What happens to the axons of second-order neurons in the dorsal column nuclei?
They decussate, or cross the midline
Where do the axons of second-order neurons synapse?
With thalamic neurons in the ventral posterior complex
What do third-order neurons project to?
The somatosensory cortex
What is a dermatome?
The innervation arising from a single dorsal root ganglion and its spinal nerve
What is a characteristic of the somatosensory cortex?
It contains a somatotopic map, also known as a homunculus
