lecture 2 - neurologic thinking

which glial cell surrounds axons in PNS?

schwann cells

which glial cells myelinate CNS axons?

oligodendrocytes

which glial cells maintain the blood-brain barrier, provide structural support, and regulate ion/nutrient concentrations?

astrocytes

which glial cells remove cell debris, wastes, and pathogens?

microglia

which glial cells line the ventricles and central canal and assist in the regulation of CSF

ependymal cells

neurons that are larger than 2μm in diameter tend to be (myelinated/unmyelinated). neurons that are smaller than that are ___

myelinated, unmyelinated

name the locations: unipolar neurons, pseudounipolar neurons, bipolar neurons, multipolar neurons

unipolar - rare, brush cells

pseudounipolar - DRGs, sensory ganglia

bipolar - retina, cochlea

multipolar - most common, throughout CNS, PNS

reactive gliosis

disease or injury activates microglia/astrocytes → inflammation → further activation → cell death, more activation, repeat

(inflammation bad)

multiple sclerosis

autoimmune disease that causes myelin to break down over time. not confined to one area, develops slowly

signs vs symptoms

symptoms - what the patient reports

signs - objective abnormalities seen in imaging or tests, etc

negative manifestations reflect ___, while positive abnormalities reflect ___

damage to neurons, inappropriate excitation of neurons

negative manifestations

loss of function (hemiparesis, impaired sensation, loss of memory, etc)

parkinsons and MS are examples of (negative/positive) manifestations

negative

positive manifestations

gain of function. seizures, spasticity, etc

how do gray and white matter lesions differ?

gray matter lesions impair the function of neuron cell bodies → cause negative or positive abnormalities

white matter lesions block axonal conduction → only negative signs

optic neuritis (demyelination of optic nerve, causing blindness) is an example of

a white matter lesion

symptoms are usually contralateral to the lesion in the CNS, except for

the cerebellum

what kind of lesion: normal muscle bulk, increased tone, increased reflexes, increased plantar reflexes

upper motor neurons

what kind of lesion: decreased muscle bulk, decreased tone, decreased reflexes, decreased plantar reflexes

lower motor neurons

what kind of lesion: normal muscle bulk, normal tone, normal reflexes, normal plantar reflexes

neuromuscular junction or non-neurological weakness

what kind of lesion: decreased muscle bulk, normal or decreased tone, normal or decreased reflexes, normal plantar reflexes

muscular

where are UMN lesions

in brain or spinal cord

where are LMN lesions

peripheral nerves, NMJ

hyperreflexia is an example of a ___ lesion

UMN

Hyporeflexia is an example of a ___ lesion

LMN

babinski reflex (big toe up), clonus (muscle spasm) suggest what kind of lesion?

UMN lesion