Page 340 - Color Atlas Of Pathophysiology (S Silbernagl Et Al, Thieme 2000)

(frontal lobe and insular cortex). The olfactory
Vestibular System, Nystagmus sense may be lost in circulatory disorders, for
example, in a nasal cold, nasal malformation,
In order to maintain positional equilibrium the foreign body, tumor, hematoma, or abscess
organism requires information about the (conductive hyposmia). The sensitivity of the
movement of the endolymph in the semicircu- sensory cells is increased by estrogens and de-
lar canals, the position of the statoliths in the creases in the elderly. It is reduced by genetic
Systems inner ear (in relation to gravity), the position defects, some drugs (e.g., cocaine, morphine),
and tension of the body’s musculature as well
and toxins (e.g., cement dust, lead, cadmium,
cyanide, chlorine compounds). The axons of
as the retinal image in relation to the activity
the sensory cells can be torn by fracture in the
of the eye muscles (→ A). On turning the head
Neuromuscular and Sensory that a stable picture is transiently maintained This results in reduced (hyposmia) or absent
region of the cribriform plate. The central pro-
the eye muscles normally move in such a way
cessing of olfactory sensations is impaired by
on the retina (→ A1). As soon as maximal dis-
neurodegenerative disease (Alzheimer’s dis-
disease
placement of the head is obtained, the eye is
[→
ease
[→ p. 348],
Parkinson’s
p. 312ff.]), inflammation, tumors, alcohol, epi-
returned in jolt-like movements of restoration
and a new point in the environment is fixed
lepsy (→ p. 338) and schizophrenia (→ p. 352).
(optokinetic nystagmus). All this information
(anosmia) sense of smell, or increased (hyper-
is processed in the vestibular nucleus and the
(cacosmia) olfactory sensation.
fluences the eye muscles via the oculomotor
and abducens nerves. An abnormality of the
10 cerebellum, and in turn such information in- osmia), inadequate (parosmia), or unpleasant
sense of balance can occur in damage to the
semicircular canals and the maculae of the Taste
membranous labyrinth (ischemia, trauma, in-
ner ear infection, Ménière’s disease [→ Taste receptors in the tongue, palate, and
p. 328]), the cerebellum (intoxication, genetic throat transmit the modalities sweet, sour,
defects, degenerative disease, inflammation salty, and bitter. The information is transmit-
[→ p. 316]), the thalamus (ischemia), and the ted to the solitarius nucleus via the facial
cerebral cortex (ischemia, epilepsy [→ p. 338]). (VII), glossopharyngeal (IX), and vagus (X)
False information leads to inadequate move- nerves (→ C). After connecting with second-or-
ment of the eye muscles (nystagmus), and der neurons, the afferent fibers pass via the
thus to roving of the surrounding objects on thalamus to the primary taste cortex in the re-
the retina (the room spins). Dizziness occurs gion of the insula. Taste receptors may be ge-
and, via connections with autonomic neurons, netically defective or damaged by radiation or
nausea and vomiting. However, these distur- some drugs (e.g., local anesthetics, cocaine,
bances are usually quickly compensated if penicillamine, streptomycin). Their sensitivity
there is prolonged loss of one of the organs in is reduced in hyperthyroidism. Patients with
the vestibular system. diabetes mellitus suffer from a reduction in
the ability to sense sweet tastes; those with
an aldosterone deficiency cannot sense salty
Olfaction tastes. The chorda tympani of the facial nerve
may be damaged by a skull fracture or inflam-
Sensory cells in the olfactory mucosa transmit mation as well as damage to or operation on
different qualities of odor, namely flowery, the ear, while the glossopharyngeal nerve
ethereal, musky, camphoric, foul, sweaty, and may be damaged during tonsillectomy. Central
stinging. Their axons pass through openings in conduction and processing can be affected by
the cribriform plate to the olfactory bulb (→ B). tumors, ischemia, and epilepsy, causing a re-
From there the information reaches the olfac- duction or loss of gustatory sense (hypogeusia
tory cortex via the olfactory tract and is then or ageusia, respectively). The sense of taste
330 transmitted to the hypothalamus, the amygda- may also be increased (hypergeusia), inade-
loid bodies, and, via the thalamus, to the cortex quate (parageusia), or unpleasant (dysgeusia).
Silbernagl/Lang, Color Atlas of Pathophysiology © 2000 Thieme
All rights reserved. Usage subject to terms and conditions of license.