The special senses
Dpt. of Normal, Pathological and
Clinical Physiology
CHAPTERS
1.
2.
3.
4.
hearing
vestibular apparatus
taste
smell
HEARING
• regular compression vawes
• transmitted in air (300m/s), water (1500m/s), and
in a solid
• type of mechanical disturbances based
communication (head vibration in snakes, lateral line in fish)
• external, middle, inner ear
terminology
TONES AND BACKGROUND
NOISE
• pitch tone: sine curve
– pitch of a tone:
frequency
– volume (loudness):
amplitude
• harmonic vibration :
tone quality (timbre of
sound)
• noise: non-periodic
terminology
terminology
DECIBEL
• sound intensity Sound Pressure Level
• range of hearing 20 microPa – 20 Pa –
therefore decibel introduction
• logarithmic unit
SPL [dB] = 20 . log(px / po)
where
px is a measured value of acoustic pressure
and
po standard sound pressure 2.10-5 Pa
terminology
PHON
subjective
sound level
depends on the
frequency
low frequency
tone (60Hz) of
the given
sound pressure
(90dB) is
percieved like
the reference
tone having
80dB – 80
phons
LOUDNESS OF COMMON
SOUNDS
jet engine
160 dB
(pain)
140 dB
(unpleasant)
120 dB
metro
100 dB
traffic
80 dB
speech
60 dB
whisper
30 dB
EXTERNAL EAR
• pinna (earlobe) and ear
canal
– act like a funnel and
resonance chamber
– localization of a source
– amplification of the waves
of specific f
– in animals – mobile pinna
MIDDLE EAR
•
•
•
•
cavity in temporal bone, Eustachian canal
ear drum, auditory ossicles, foramen ovale
lever arm system: magnification of the sound pressure 30x
tympanic reflex: contraction of m. tensor tympani and m.
stapedius, stapes out, defense function, 0.1 s
INNER EAR
• bony labyrinth (os temporale),
membranous labyrinth
• cochlea: 35mm, 2 ¾ turns,
divided by basilar and
Reissner’s membrane into 3
chambers: the upper scala
vestibuli and lower scala
tympani (helicotrema,
perilymph, foramen ovale,
foramen rotundum); the middle
scala media (endolymph, does
not communicate)
ORGAN OF CORTI
• outer hair cells: 3
rows, 20000
• inner HCs: 1 row,
3500 = receptor
• membrana
tectorialis - tips of
outer hair cells are
embedded
tonotopical organization of the cochlea
AUDITORY
PATHWAY
• inner hair cells
• ganglion spirale
• ncl. cochlearis doraslis et
ventralis in oblongata
• olivary nuclei ipsi + contra
• (nc. lateral lemnicsi)
• colliculi inferiores
(auditory reflexes)
• corpus geniculatum
mediale (thalamus)
• primary auditory cortex
(temporal, Brodmann 41)
BAEP
The thalamus (medial
geniculate ganglion) and
the auditory cortex
(temporal lobe) make up
the middle and late
waves of the AEP.
auditory nerve = wave I
cochlear nuclei = wave II
superior olive = wave III
lateral lemniscus = wave IV
inferior colliculus = wave V
Waves I-V make up the
brainstem AEP.
BRAIN AREAS
• frequency of APs is
proportional to the
loudness
• tonotopical
character through
whole pathway
(cohlea to cortex)
LOCALIZATION OF THE
SOURCE
• timing – difference in
latency between both
ears (20 ms is enough),
important for the tones
under 3000 Hz
• difference in loudness
between both ears,
over 3000 Hz
VESTIBULAR APPARATUS
• located in os temporale, formed by membranous
labyrinth
• 3 semicircular canals and 2 cavities (saculle and
utricle)
SACCULE AND UTRICLE
• sensory organ
macula, in utricle
horizontally, in
saccule ventrically
• macula contains hair
cells, gelatinous layer
with CaCO3 crystals
• genesis of AP
• linear acceleration,
gravitation
SEMICIRCULAR
CANALS
• each widen at the end
to form ampula
• ampula contains
cupula: analogous
with macula (hair cells,
excitated by the
movements of
endolymph)
• angular acceleration
Hair cells
Vestibular nerve
(Ganglion vestibularis)
Ncc. vestibulares
Vestibular
ncc. efferents
• Vestibuloocular III, IV, VI
(oculomotor, trochlearis,abducens)
• vestibulospinalis
• Vestibulocerebellaris
• VB complex – Sylvian
fissure
TASTE
•
•
•
Chemoreceptors
distant chemical sense
functions:
1. recognition of food, differentiation from
poisons
2. strong coupling with behavior and emotions
•
the same for smell
TYPES OF RECEPTORS
• 13 types of taste receptors:
– 2 receptors sodium, 2 kallium, 1 chlorine, 1
adenosin, 1 inosin, 2 saccharids, 2 bitter taste, 1
glutamate and 1 for H+
• beside them tactile and nociceptive
receptors in mouth (V nerve)
TASTE QUALITY
•
hundreds of tastes, maybe a result of
combination of 4 basic (analogy with color
vision)
1. sour taste
2. salt
3. sweet (sugar, glykol, ethanol, aldehyde, ketone, amide,
4.
5.
AA, peptides)
bitter (long chained substances containing nitrogeon,
alkaloid - chinin, kofein, strychnin, nicotine)
umami
THRESHOLD VALUES
• the lowest for the bitter
taste (10-5 mol), the
highest for salt and sweet
(10-2 mol)
• taste blindness
fenylthiokarbamid (cabbage,
broccoli): 30%
RATIO
• sweet: sucrose 1, 1-propoxy2-amino-4-nitrobenzen 5000,
fructose 1.7, glucose 0.8,
lactose 0,3
• salt: NaCl 1, NaF 2, CaCl2
1, NH4Cl 2.5, KCl 0.6
• sour: HCl 1, formic a. 1.1,
butiric a. 0.85, citric a.
0.46
• bitter: chinin 1, strychnin
3.1, cofein 0.4, morphine
0.02
TASTE BUDS
• 50 epithelial cells (taste
and supporting cells)
• taste pores, microvilli
contains receptors,
synapse nerves
LOCALIZATION OF TASTE
BUDS
TASTE
PATHWAYS
• Buds
• Facial nerve – Chorda
tympani (ncc.)
• Glossopharyngeal nerve
(ncc.)
• (vagus)
• Tractus solitarius (gustatory
ncc.)
----------• Thalamus (VB complex)
• Sylvian fissure (SSA1)
SMELL
•
low known sense:
1. subjective, cannot be studied in animals
2. not well developed in humans (?)
• each nostril, surface area 2.4 cm2
OLFACTORY CELLS
•
•
•
•
•
•
bipolar neurons, 100 millions
olfactory hairs, contain receptors
thousands of receptors, smell blindness
Bowman’s glands: secretion of mucus
ligand has to be water soluble
G-protein coupled receptors (amplification: 1 ligand =>
several G-protein => more adenylcyclases => lot of cAMP)
• absolute and recognition thresholds (garlic
ADAPTATION
• during first few seconds 50%
• then slow and weak
• important role of CNS (similar to taste)
OLFACTORY
PATHWAYS
• axons of olfactory cells
through lamina
cribriformis to the bulbus
olfactorius
• synapse to the mitral cells
(in glomerulus – segregation)
• their axons via olfactory
tract to the olfactory
cortex (ncl. olf. ant.,
pyriform cortex,
tuberculum olfactorium,
amygdala, entorhinal
cortex) and reticular
formation (arousal)
OLFACTORY CORTEX
• ncl. olf. ant.: coordination of
contralateral inputs
• pyriform cortex: smell
discrimination
• amygdala: emotion
• entorhinal cortex: memory
processes
• eliciting salivary and
gastric secretion
• hygiene monitor
• social information
• sexual behavior