Lyrics · 完整歌詞
Neuronal structure reflects the demands of maintaining a specialised cell whose signalling
and transport processes may extend far beyond its cell body.
Nissl bodies, stacked rough endoplasmic reticulum,
fill the soma and dendrites but never the axon.
Kinesin carries cargo forward to the terminal and dynein returns it,
the same retrograde train that carries tetanus toxin back to the cord.
Oligodendrocytes myelinate many central axons each, Schwann cells one internode each,
and microglia, the only glia of mesodermal origin,
clear debris that oligodendrocytes cannot.
Astrocytic end-feet, endothelial tight junctions and basement membrane form the blood-brain barrier,
which the area postrema deliberately lacks.
The neural tube folds from a plate,
and its front end swells into three vesicles, then five.
The telencephalon becomes cortex and basal ganglia around the lateral ventricles,
and the diencephalon becomes thalamus,
retina and posterior pituitary around the third ventricle.
The mesencephalon keeps the aqueduct, and the metencephalon forms pons and cerebellum.
The anterior neuropore closes around day 25
and the posterior around day 27 to 28;
failure gives anencephaly or, with folate deficiency, spina bifida.
Dandy-Walker bulges outward from an absent vermis,
whereas Chiari II drags vermis and medulla down through the foramen magnum.
Neuronal structure reflects the demands of maintaining a specialised cell whose signalling
and transport processes may extend far beyond its cell body.
Medicines act on three switches: channels, receptors and reuptake.
Ethosuximide blocks thalamic T-type calcium channels in absence seizures,
benzodiazepines increase the frequency and barbiturates the duration of GABA-A opening,
and baclofen agonises GABA-B.
Beta receptors raise cAMP through Gs,
alpha-1 and M3 raise calcium through Gq,
alpha-2 and M2 lower cAMP through Gi,
and cGMP belongs to nitric oxide.
Hence alpha-1 closes the bladder sphincter while M3 contracts the detrusor,
so overactive bladders take M3 antagonists or a beta-3 agonist
and prostatic obstruction takes an alpha-1 antagonist.
Localisation asks the height, the side and the system.
The striatum is caudate, putamen and globus pallidus;
the midbrain dopaminergic nucleus and subthalamic nucleus belong to the circuit
but not to the striatum.
A destroyed frontal eye field lets the eyes drift toward the lesion,
whereas a destroyed pontine gaze centre drives them away.
Hearing relays in the medial geniculate body, which is thalamic, not midbrain,
and vision in the lateral geniculate.
The mandibular nerve leaves through the foramen ovale,
the maxillary through the rotundum,
the facial nerve exits at the stylomastoid foramen,
and the vestibulocochlear enters the internal acoustic meatus.
Genioglossus protrudes the tongue,
so a hypoglossal palsy deviates it toward the lesion;
the anterior two-thirds taste through the chorda tympani
and the posterior third through IX.
The vagus drives the pharyngeal constrictors, palate and vocal cords,
so its injury causes aspiration.
Deep intrinsic back muscles, the erector spinae that arch the tetanic spine,
are supplied by dorsal rami,
whereas the superficial extrinsic layer answers to ventral rami.
Neuronal structure reflects the demands of maintaining a specialised cell whose signalling
and transport processes may extend far beyond its cell body.