Lecture 11 - Sensory Systems: Posterior Column- Medial Lemniscus Pathways Flashcards
What are the 4 modalities ?
Touch, proprioception, pain, temperature
Hint: Double TT, Double PP
Is pain a chemical or mechanical irritation?
chemical
what are the 4 types of somatosensory receptors?
Mechanorecptors, chemoreceptors, thermoreceptors, nociceptors
True or false.. free nerve endings have a fast rate of conduction?
false
Mechanoreceptors for proprioception in and around joints detect which functions?
Detect limb position, joint movement and pressure
Golgi tendon organs are located where ?
muscle tendon junction
What is the connective tissue surrounding the entire peripheral nerve?
Epineurium
What is the delicate connective tissue surrounding each individual nerve fibre (axon)?
Endoneurium
T/F: The dorsal pathway conveys crude touch?
False.
Higher order neurons relay somatosensory information to other higher centres to modulate ______ and _____.
level of arousal and alertness
Sensory receptors are located at the _____ (distal or proximal) ends of peripheral nerves.
Distal
Define receptive field
The area of skin supplied by a single afferent
neuron is the receptive field for that neuron.
receptive fields are smaller ____ and ____ proximally
distally; larger
what are the advantages of a parallel system?
- adds to perceptual experience
- offers a measure of insurance
List the 4 types of information all sensory systems conveyed when stimulated.
modality, location, intensity, duration
Hint: MILD
What is the term for precision of stimulus location?
acuity
What is Lateral Inhibition.
a strong stimulus applied to the receptive field of one neuron causes that neuron to inhibit transmission of signals by neurons with neighboring receptive fields.
Duration is a relationship between _____ and ______.
stimulus intensity and perceived intensity
Rapidly adapting receptors burst when stimuli initiated only and responds best to _______ (changing or unchanging) stimuli
changing
List the Four major mechanoreceptors in the skin
Meissner’s corpuscles, Merkel’s disc receptors, Pacinian corpuscles, Ruffini endings
Define a dermatome
a peripheral region innervated by sensory fibers from a single nerve root
Where are sensory neuron cell bodies are located?
dorsal root ganglion
What is the 1st relay of sensory information to sites higher in the nervous system?
dorsal horn
What are the two main pathways of the sensory system?
posterior column-medial lemniscus pathway
anterolateral pathways
mechanoreceptors have ____ (large or small)diameter, ______ (myelinated or unmyelinated) axons that conduct AP’s rapidly
large; myelinated
What stimulates mechanoreceptors?
indentation of skin or motion across its surface
what are the 2 sub modalities for Mechanoreceptors for proprioception?
- joint position sense/proprioception
- speed and direction of limb movement (kinesthesia)
Mechanoreceptors for proprioception in and around joints include what 3 types of mechanoreceptors ?
Ruffini endings, pacinian corpuscles, free nerve endings
Primary sensory endings: group 1a afferents are stimulated at onset of _____.
stretch
Secondary sensory ending: group II afferents, respond to _______
tonic (sustained) stretch
T/F: Golgi tendon organs are innervated by 1a sensory axons ?
false
which mechanoreceptors for proprioception function via autogenic inhibitor ?
Golgi tendon organs
T/F: The Medial Lemniscus Pathway: majority of axons pass directly to the posterior or ventral column
false: dorsal
The gracile fasciculus conveys information from ____.
legs and lower trunk
The cuneate fasciculus conveys information from ____.
upper trunk (above T6) arms and neck
T/F: For the Posterior Column- Medial Lemniscus Pathway at the medulla, primary sensory neurons synapse on second order sensory neurons
true
T/F: At medulla the PCML axons of the first order neurons cross over to other side as internal arcuate fibres
false: second
True or False: medial lemniscus axons synapse on third order neurons in thalamus
true
The posterior limb of internal capsule is called ___ ____ _____.
thalamic somatosensory radiations
what does the analogous pathway (the trigeminal lemniscus) convey?
touch sensation for the face
From the internal capsule, ascending sensory fibres project to primary somatosensory cortex on the _____ _____.
postcentral gyrus
Do unilateral lesions from the level of the nuclei Gracilis and Cuneatus down through the cord produce unilateral or bilateral deficits ?
unilateral
