Senses and Perceptions 2 Flashcards
Where do afferent neurones begin and where do efferent neurones end?
afferent - skin, muscle
efferent - muscle
What is each nerve fibre encased by?
endoneurium
What is each fascicle encased by?
perineurium
What are groups of fascicles encased by?
epineurium
What are myelinated axons surrounded by?
myelin sheath from Schwann cells
What are characteristics of a-alpha fibres?
myelinated, large diameter, conducts very fast, sensory (proprioception) and motor information from skeletal muscles
What are characteristics of a-beta fibres?
myelinated, medium diameter, conducts fast, mechanoreceptors of skin
What are characteristics of a-delta?
myelinated, small diameter, conducts slowly, pain and temperature
What are characteristics of C axons?
non-myelinated, small diameter, conducts very slowly, pain, temperature, itch
What are the horns found in grey matter?
dorsal
intermediate
ventral
In what horns does motor and sensory innervation take place?
dorsal - sensory
ventral - motor
What are dermatomes?
areas of skin on your body that are innervated by specific regions of the spine.
What are myotomes?
muscles in the body are supplied by segments of the spinal cord and their corresponding spinal nerves.
What components of the trigeminal nerve are solely sensory?
ophthalmic
maxillary
What component of the trigeminal nerve has motor and sensory function?
mandibular
How many neurones is the sensory pathway composed of?
3 inter-connected neurones
What do 1st (primary) order sensory neurones bring information from?
from periphery to spinal cord/brainstem
What do 2nd (secondary) order sensory neurones bring information from?
from spinal cord/brainstem to thalamus
Where do 3rd (tertiary) order sensory neurones bring information from?
thalamus to cerebral cortex
Where does the sensory pathway direct?
to opposite side of the body
What neurone usually cross the midline boundary?
2nd order
Why is the sensory homunculus distorted?
Body regions with high sensory innervation (i.e. high density of receptor endings and small overlapping receptive fields) have greater cortical representation
Describe the somatic mechanosensation Dorsal Column-Medial Lemniscal Pathway (body)
afferent 1st order nerve fibre travels from skin to dorsal horn to synapse with 2nd order nerve fibre at brainstem (oblongata medulla)
2nd order crosses over to reach 3rd order at thalamus
3rd order sends out to the somasensory cortex
Describe the somatic mechanosensation Posterior (Dorsal) Trigeminothalamic Pathway (face)
trigeminal nerve 1st order synapses at brainstem nucleus (medulla)
2nd order neurone crosses over to the thalamus to connect to 3rd order
3rd order sends out to the somasensory cortex
Describe the somatic nociception Spinothalamic Pathway (body)
afferent 1st order nerve synapses at the dorsal horn
2nd order crosses the midline to the thalamus
3rd order sends out to the somasensory cortex
Describe the somatic nociception Anterior (Ventral) Trigeminothalamic Pathway (face)
trigeminal nerve 1st order synapses at spinal trigeminal nucleus of spinal cord
2nd order neurone crosses over to the thalamus to connect to 3rd order
3rd order sends out to the somasensory cortex
What is sensation?
The process of sensing our environment (touch, taste, sight, smell) by activation of sensory pathways
What is perception?
The interpretation of sensory input (interpretation of sensation)
What is stereognosis?
The mental perception of objects referenced by touch via memory, texture, weight and size
Where does stereognosis retrieve information and regulate activity?
hippocampus; basal ganglia; motor cortex
What is Proprioception (Kinesthesia)?
the sense that lets us perceive the location, movement, and action of parts of the body.
What sensations does the DCML pathway process?
fine touch, 2 point discrimination, proprioception
