Somatosensation Flashcards
What senses does somatosensation consist of?
touch, temperature, pain and proprioception
Where are the cell bodies of the primary sensory afferent neurons held?
the dorsal root ganglia
What is the polarity of the cell body?
pseudounipolar
What is the trigeminal ganglia?
the neuron that innervates the head and neck and projects centrally to the trigeminal nucleus
What is the nodose ganglia?
also known as the inferior vagal projects to the floor of the fourth ventricle and innervates the viscera via the vagus nerve
What are the sensory receptive properties?
modality, threshold, adaptation rate, conduction velocity and site of termination
What is modality?
the type of stimulus adequate for transducing a response i.e. light is usually the adequate stimulus for your eyes however putting pressure on them can cause the perception of light
What is the threshold?
low threshold units respond to low intensity and non-damaging stimuli
high threshold units respond to high but not low intensity stimuli which are potentially noxious and can be interpreted as painful if it reaches the higher centres of the brain
What is adaptation?
when a stimulus is maintained, the AP firing rate decreases as the the receptor adapts to the stimulus. can be rapid, slow, or very slow (v.rapid, rapid and slow) i.e. slow adaption might be if you have broken your leg and try to walk on it
What is the conduction velocity?
where primary sensory afferents differ greatly in thickness, myelination, conduction velocity and associated receptors
What is the site of termination?
the receptive field - ie. the region that when stimulated with an adequate stimulus will cause a response in the neuron
What are the sensory cutaneous receptors?
Mechanical contact - merkel discs, krause end bulbs, root hair plexus, meissners corpuscles, ruffini endings
Temperature/Pain - free nerve endings
How are the Meissners corpuscles and panincian corpuscles innervated?
Meissners - Ab - rapid adapting, stroking/flutter
Panician - Ab - very rapid adapting, vibration
How does the Pancinian Corpuscle work?
consists of a central nerve terminal which is surrounded by concentric, fluid-filled lamellae which when compressed sends a signal to the nerve terminal opening machano-sensitive ion channels
responds to maintained pressure by rapid adaptation making it good for sensing vibration
What are the comparable receptive fields of Meissners corpuscles and Panician Corpuscles on the hand?
Meissners - small receptive fields but lots of them
Pancinian - large receptive fields but only 2 main sensitivity spots
