ОРГАНЫ ОЩУЩЕНИЯ Лекция 17

Лекция 17
ОРГАНЫ
ОЩУЩЕНИЯ
•Осязание
Клетки коротко- и длиннодистантных сенсорных рецепторов
Рецепторы растяжения
ракообразных (long sensory receptor)
Сенсорный рецептор
веретёнообразной мышцы
млекопитающего
(a) Gentle
touch
1
fires slowly
2
Сигнальный
стимул
интенсивности
silent
1
2
(b) Moderate
pressure
1
fires more rapidly
2
2
silent
1
(c) Strong
pressure
1
fires very rapidly
2
1
2
fires slowly
Рефлекс поверхностного болевого
ощущения
dorsal
root
receptor
REFLEX
ARC
stimulus
effector
ventral
root
sensation
relayed
to the
brain
Механорецепторы кожи
Sensory Nerve Endings in
Skin
Nerve
Endings
in The
Skin
Сенсорная система осязания
Рецепторы осязания и латеральное
ингибирование
•Органы
обоняния,
слуха и вкуса
Схематическое представление морфогенеза и
дифференцировки эктодермы в различные черепные
плакоды у позвоночных (Schlosser, 2006)
Органы вкуса и запаха
Обоняние
Способность ощущать
запахи обязана
существованию
обонятельных
рецепторов
Развитие обонятельных органов
Обонятельные рецепторы
• Although the human sense of smell is feeble
compared to that of many animals, it is still very
acute. We can recognise thousands of different
smells, and we are able to detect odours even in
infinitesimal quantities.
• Our smelling function is carried out by two small
odour-detecting patches – made up of about five
or six million yellowish cells – high up in the
nasal passages.
• For comparison, a rabbit has 100 million of
these olfactory receptors, and a dog 220 million.
Humans are nonetheless capable of detecting
certain substances in dilutions of less than one
part in several billion parts of air.
olfactory
epithelium
olfactory structure of brain
nasal
cavity
association
neurons
bone
olfactory
receptors
air with
odor molecules
mucus
layer
nasal cavity
olfactory
dendrites
Competence, specification and commitment to an olfactory placode fate
Sujata Bhattacharyya and Marianne Bronner-Fraser, Development 135, 4165-4177 (2008)
The nasal placode shares a common origin with other sensory placodes within a preplacodal domain at
the cranial neural plate border. However, little is known about early events in nasal placode
development as it segregates from prospective lens, neural tube and epidermis. Dlx3, Dlx5, Pax6 and
the pan-neuronal marker Hu serve as molecular labels to follow the maturation of olfactory precursors
over time. When competence to form olfactory placode was tested by grafting ectoderm from different
axial levels to the anterior neural fold, we found that competence is initially broad for head, but not
trunk, ectoderm and declines rapidly with time. Isolated olfactory precursors are specified by HH10,
concomitant with their complete segregation from other placodal, epidermal and neural progenitors.
Heterotopic transplantation of olfactory progenitors reveals they are capable of autonomous
differentiation only 12 hours later, shortly before overt placode invagination at HH14. Taken together,
these results show that olfactory placode development is a step-wise process whereby signals from
adjacent tissues specify competent ectoderm at or before HH10, followed by gradual commitment just
prior to morphological differentiation.
KEY WORDS: Olfactory placode, Nasal placode, Chick, Competence, Specification, Commitment,
Induction, Ectoderm
Обонятельные рецепторы
(хеморецепторы)
Обонятельные рецепторные
нейроны (хеморецепторы)
Передача сигналов через обонятельные
волоски (хеморецепторы)
• The prevailing paradigm for G proteincoupled receptors is that each receptor is
narrowly tuned to its ligand and closely
related agonists.
• An outstanding problem is whether this
paradigm applies to olfactory receptor (ORs),
which is the largest gene family in the
genome, in which each of 1,000 different G
protein-coupled receptors is believed to
interact with a range of different odor
molecules from the many thousands that
comprise ‘‘odor space.’’
• Insights into how these interactions occur
are essential for understanding the sense of
smell.
• The vomeronasal organ (VNO), or Jacobson's organ,
is an auxiliary olfactory sense organ that is found in
many animals. It was discovered by Ludvig Jacobson in
1813.
• During embryological development, it forms from the
nasal (olfactory) placode at the anterior edge of the
neural plate (cranial nerve zero). It is a chemoreceptor
organ which is completely separated from the nasal
cavity the majority of the time, being enclosed in a
separate bony or cartilaginous capsule which opens into
the base of the nasal cavity. It is a tubular crescent
shape and split into two pairs, separated by the nasal
septum. It is the first processing stage of the accessory
olfactory system, after which chemical stimuli go to the
accessory olfactory bulb, then to targets in the amygdala
and hypothalamus.
Frontal section of nasal cavities of a human embryo 28
mm. long (Vomeronasal organ of Jacobson
• The vomeronasal organ is mainly used to detect
pheromones, chemical messengers that carry
information between individuals of the same
species, hence is sometimes referred to as the
"sixth sense." The VNO has two separate types
of neuronal receptors, V1R and V2R, which are
seven-transmembrane receptors that are
coupled to G proteins. The receptors are distinct
from each other and form the large family of
receptors in the main olfactory system. Evidence
shows that the VNO responds to nonvolatile
cues which stimulate the receptor neurons.
Information is then transferred to the accessory
olfactory bulb as well as other centres of the
brain such as the anterior part of the
hypothalamus.