TBL: Structure and function of the spinal cord Flashcards
An increase in neuronal activity is thought to lead to communication between the axon and what?
Glia cells through gliotransmitters (signalling molecules).
An increase in what type of nerve fibres is thought to account for an increase in white matter volume?
Myelinated.
What is optic neuritis caused by?
Demyelination of the optic nerve.
In optic neuritis, why do patients not experience blindness?
There is a reduced and blocked conduction along the nerve fibres, but some axons are still able to transmit messages thought the optic nerve.
Which examination is used to assess an optic nerve?
Fundoscopy
A high stoppage, wide based gait and unsteadiness would be signs of which type of sensory loss?
Proprioception.
What is the Romberg’s test?
When someone is more unsteady with their eyes closed than open.
This tests for proprioception + the dorsal column.
Which receptors detect temperature sensation?
Nociceptors
Which fibres transmit an initial pain sensation?
Alpha-delta (quick message transmission)
A prolonged pain sensation is transmitted by which fibres?
Unmyelinated C fibres.
Pain received by brain following transmission from the ascending spinothalamic tract.
What is the knee jerk reflex?
A dynamic stretch reflex that responds to a sudden stretch in muscle (tendon hammer on patella).
Stretch detected in the muscle spindles, this produces a signal that is sent through afferent fibres entering the spinal cord through the dorsal root ganglion and synapses at the level of L3/L4.
There is then stimulation of the gamma motor neurons to contract the infrafusal muscle fibres in the muscle spindle, but the gamma motor neuron doesn’t control the voluntary muscle.
This tests proprioception.
There are no interneurons involved - therefore a monosynaptic pathway.
In UMN disorders, why are reflexes exaggerated?
There is a reduction in normal inhibitory control.
Golgi tendon organ in the muscle tendon responds to tension + protects against excessive tension by having an inhibitory affect on alpha motor neurons, relaxing the muscle (Clasp-knife reflex/inverse stretch reflex).
Golgi tendon organs transmit information regarding tension and the mount of force being applied to a muscle. A reduction in this control results in exaggerated reflexes.
Interneuron pathways involved = polysynaptic.
