reflexes, pain, motor control Flashcards
patellar reflex -
describe the pathway
the point of this reflex and it’s broader name
afferent sensory fibre to dorsal root ganglion
direct synapse with motor neuron in ventral horn
synapses at muscle
point = stretching the extensor muscle and associated tendon causes stretching that must be corrected
broader name is the stretch reflex - pouring a drink, arm doesn’t as drink gets heavier as an example
stretch reflex - what is the other part of the circuit?
sensory neuron also talks to an interneuron, which talks to a motor neuron to inhibit the other muscle from counteracting the reflex
muscle spindle - where?
what does it do?
include details on the neurons used?
found in striated muscle
the extrafusal muscle like the bicep or whatever, the home of the muscle spindle, is innervated by alpha motor neuron
spindles slacken when muscle contracts, Ia sensory fibres aren’t firing
when stretched the spindle is tight and lets you know the end point
muscle fibre - innervated by gamma motor neurons - adjust the tension
golgi tendon organ - what do they do and what neurons do they activate?
they detect muscle tension, not stretch
sensory Ib fibres actiavted by too much tension, GTO causes inhibitory neurons to inhibit the alpha neurons of that msucle to prevent you from over doing it
flexor/withdrawal reflex?
what is it?
poly or monosynaptic?
parallele after-discharge circuit?
jerks a limb away from something painful
polysynaptic
parallel after discharge = looks like a parallel circuit from physics, with different number of sunapses so info arrives in succession not at once, sustains response
contralateral element of withdrawal reflex?
prepares other leg to take weight
what are repetitive behaviours? Like in walking, alternating the pattern of flexion and extension
Like in walking, alternating the pattern of flexion and extension when walking, plus alternating sides - can happen with severed spinal cord
stretch receptors involved
sensory receptors - encapsualted?
meissner/tactile corpuscles - light touch and texture, found in palms and eyelids, lips and tongue etc… 30-50Hz, these are rapidly adapting
Pacinian corpuscles - detect deep pressure, vibrations, tickles 250-350Hz, these are rapidly adapting
Ruffini corpuscles - actually a kind of proprioceptor - located in the dermis, subcutaneous tissue - detect deep pressure, skin stretch, joint movements, these are slow adapting
Capsules are involved in ‘filtering’ so that different cells respond to different frequencies and we can differentiate between types of touch
unencapsulated sensory receptors?
merkel/tactile cells/discs - light touch, edges and texture
Free nerve endings - pain, heat and cold, widespread in the epithelia
rapid and slow adapting meaning?
rapid = when stimulus starts, desensitises?
slow = tonic, persistent
how are axons classified?
A B C where A is fastest/largest, alpha to delta subdivisions alpha fastest
muscles use roman numerals I - IV
what axons do 1) pain 2) proprioception
use?
1) = C
2) = Aa
medial lemniscal tracts carry…
mechano and proprioceptive signals to the thalamus
spinothalamic tract…
pain and temperature to spinal cord
medial leminiscal - is lower or upper body more medial in the spinal cord and how is topology preserved?
lpwer is medial/gracile nucleus, upper is lateral/cuneate nucleus
2nd order neurons cross midline, making upper the more medial, so the htird order neurons must cross again to preserve topology in the brain
