Case 6 - Multiple sclerosis Flashcards
What are the 4 types of neurons?
Unipolar = sensory
Pseudounipolar = sensory
Bipolar = interneuron
Multipolar = interneuron or motor neuron
What is axonal transport?
Transport of proteins and polypeptides from soma to axonal end for secretion. Packaged into vesicles by golgi apparatus in the soma
What are the 2 types of axonal transport and what proteins do they use?
Anterograde transport - from soma to axonal end = uses kinesin
Retrograde transport - terminal sends signals to the soma = uses dyenin
What is the role of astrocytes?
- Supply metabolic fuel (as lactic acid) to neurons
- Synthesise NT
- Maintains K+ concentration
- Act as support cells, maintain the BBB
What are the 2 types of astrocytes and where are they primarily found?
Fibrous astrocyte = white matter
Protoplasmic astrocyte = grey matter
What is the role of microglial cells?
Proliferate following injury, act as scavengers and remove cellular debris. They are the resident macrophages = 1st line of immune defence in the CNS
What is the role of oligodendrocytes?
Synthesise myelin in the CNS
What is an electrotonic potential? Give an example of what can cause one
Non-propagated local current, resulting from a local change in ionic conductance.
Example = Amacrine cells in retina
What are relay nuclei? Give examples and where they are present
Integrate converging information, found in the CNS but predominantly in the thalamus. They include local interneurons and projection neurons
What is the composition of myelin?
Lipids: galactocerebroside
Glycoproteins: myelin basic protein, myelin oligodendrocyte protein, myelin associated glycoprotein
How do action potentials jump from node to node from myelinated neurons?
Small gaps between myelin sheath = Nodes of Ranvier, VG Na+ channels are only present here, so AP jump from node to node (‘saltatory conduction’)
By how much does myelination increase the speed of conduction of neurones?
Around 15x faster:
Unmyelinated conduction = 0.5-10 m/s
Myelinated conduction = 150 m/s
How does demyelination of neurons make people feel more tired?
Impairs signal conductance so it increases the energy cost of neurons = fatigue faster
Compare primary and secondary demyelination
Primary demyelination: myelin sheath is damaged or destroyed whilst axons remain intact
Secondary demyelination: myelin sheath is damaged as a result of primary axonal damage
Give an example of a demyelinating disease affecting the CNS and the PNS
CNS: multiple sclerosis, vitamin B12 deficiency
PNS: Guillian-Barre syndrome
What are the functions of the cerebellum?
Coordinates movement, planning and execution of movement, maintenance of posture, control of head and eye movement
It integrates sensory information about position of spinal cord, motor information from cortex and balance from vestibular organs
What are the functional divisions of the cerebellum and what are their roles?
Vestibulocerebellum: controls balance and eye movements (i.e. VOR)
Spinocerebellum: inc. vermis and intermediate zone, controls synergy of movement and receives proprioceptive information
Cerebrocerebellum: largest, involved in planning movements and motor learning
What are the inputs/ outputs of the functional divisions of the cerebellum?
Vestibulocerebellum: input= vestibular system, sends outputs to vestibular nuclei
Spinocerebellum: input= spinal cord (spinocerebellar tract), outputs= rubrospinal, vestibulospinal, reticulospinal
Cerebrocerebellum: input= cerebral cortex and pontine nuclei, ouput= thalamus and red nucleus
What is the pontine regulator of the cerebellum and lies in the centre? Give its role
Vermis: regulates posture and eye movements
What tracts transmit unconscious proprioceptive information to the cerebellum? Which transmit information from upper vs lower limbs?
Spinocerebellar tracts:
> Dorsal and ventral spinocerebellar = lower limbs
> Cuneocerebellar and rostral spinocerebellar = upper limbs
If a patient has difficulty carrying out skilled planned movements and motor learning, which part of the cerebellum is likely to be affected?
Cerebrocerebellum and spinocerebellum
What acronym can be used for manifestations of cerebellar dysfunction?
DANISH:
Dysdiadochokinesia (difficulty carrying out rapid, alternating movement)
Ataxia
Nystagmus
Intention tremor
Scanning speech (long pauses between words)
Hypotonia
How is the cerebellum connected to the brainstem?
Afferent and efferent connections run between the peduncles:
Superior peduncle = midbrain
Middle peduncle = pons
Inferior peduncle = medulla
What is multiple sclerosis?
Slow, progressive CNS disease, characterised by destruction of myelin sheath around axons in brain and spinal cord. Seems to be an immune attach against oligodendocytes