Model Call Girls In Chennai WhatsApp Booking 7427069034 call girl service 24 ...
Pathways 2
1. 1
Ivano-Frankivsk National Medical University
The Department of Human anatomy
Descending (efferent) pathways.
Pathways of visual, auditory
analyzers, taste and smell.
Topography of pathways of spinal
cord on the transverse section.
Prepared by PhDPrepared by PhD
Tetyana Knyazevych - ChornaTetyana Knyazevych - Chorna
2. 17-2
Descending (efferent) pathways:
Pyramidal pathways conduct voluntary
motor inpulses from the cerebral cortex
Extrapyramidal pathways deals with the
basal nuclei, maintain interrelations and
act as a single unit
3. 17-3
Pyramidal pathways
Corticonuclear fibers
Corticospinal fibers
The first neurons- gigantic
pyramidal cells (of Betz) of
precentral gyrus and the
paracentral lobule. The
axons form the pyramidal
fasciculus that descends
to the brainstem and
spinal cord.
4. 17-4
Some fibers decussate yet in the
brainstem and terminate on the
motor nuclei of the cranial nerves
(III and IV pairs in midbrain; V-VIII
in pons; IX-XII in medulla) and form
the corticonuclear fibers.
The motor cells of the nuclei of
cranial nerves are the second
neurons. Their axons quit the
brainstem and reach the areas of
the responsibility
6. 17-6
The larger portion of the
fibers descends to the
pyramids of the medulla as
a corticospinal fibers.
80% decussate and enter
the lateral funiculus to form
the lateral corticospinal
tract. The rest of fibers
proceed to the anterior
funiculus to form the
anterior corticospinal tract.
7. 17-7
Injury of the
pyramidal tracts
results in central
paralysis of both
limbs while the
diaphragm and the
muscles of trunk
manifest little
malfunctioning.
8. 17-8
Extrapyramidal pathways
the extrapyramidal system is a neural
network that causes involuntary reflexes
and movement, and modulation of
movement. Extrapyramidal tracts are chiefly
found in the reticular formation of
the pons and medulla, and target neurons
in the spinal cord involved in reflexes,
locomotion, complex movements, and
postural control.
9. 17-9
These tracts are in turn modulated by
various parts of the central nervous
system, including the nigrostriatal
pathway, the basal ganglia, the
cerebellum, the vestibular nuclei, and
different sensory areas of the cerebral
cortex. All of these regulatory components
can be considered part of the
extrapyramidal system, in that they
modulate motor activity without directly
innervating motor neurons.
10. 17-10
Extrapyramidal pathways
The rubrospinal tract
The tectospinal tract
The vestibulospinal tract
The olivospinal tract
The reticulospinal tract
14. 17-14
Olfaction – Sense of Smell
The olfactory system represents
one of the oldest sensory
modalities in the phylogenetic
history of mammals. As a chemical
sensor, the olfactory system
detects food and influences social
and sexual behavior.
15. 17-15
The olfactory area related to the superior
nasal concha and adherent portion of
nasal septum. The olfactory part
comprise 3 types of cells: receptor cells,
supporting cells, basal cells.
The axons of receptor cells pass the
cribriform plate of ethmoid bone as the
olfactory nerve, they reach the olfactory
bulb to synapse with the second
neurons.
16. 17-16
The second neurons form the
olfactory tract, which terminates
within the olfactory trigone, the
anterior perforated substance,
septum pellucidum, where the 3-d
neuron stay.
17. 17-17
Axons of 3-d neuron
run to amygdaloid
body, the olfacrory
cortex of
parahippocampal
gyrus, uncus.
It has the
connections with the
mammilary bodies,
reticular formation,
nuclei of cranial
nerves.
19. 17-19
Gustation – Sense of Taste
Gustatory receptors are housed in specialized taste buds
on the surface of the tongue.
4 types of papillae:
filiform
fungiform
vallate
foliate
The tongue detects five basic taste sensations:
salty
sweet
sour
bitter
umami
21. 17-21
The first neurons are the
pseudounipolar neurons of
the sensory ganglia of facial
and glossopharyngeal
nerves.
Lingual nerve of facial
cranial nerve (from anterior
2/3 of tongue) and lingual
branches of
glossopharyngeal nerve
(from posterior 1/3 of
tongue) terminates the
nucleus of solitary tract,
where the bodes of 2-d
neurons stay.
The axons of 2-nd neurons
decussate and join the
medial lemniscus that
ascends to the thalamus.
The axons of 3-d neurons of
thalamus reach the uncus of
23. 17-23
Visual Pathways
a pathway over which a visual
sensation is transmitted from
the retina to the brain.
The fibers of an optic nerve traveling
through the optic chiasm to the the
thalamus,the lateral geniculate body and
superior coliculi, and optic radiations
terminating in an occipital lobe (sulcus
calcarinus). Each optic nerve contains
fibers from only one retina. The fibers from
the middle parts of the retinas cross to the
opposite side of the brain at the optic
chiasm.
24. 17-24
The fibers from the
lateral part of each eye
do not cross at the
optic chiasm, pass
through the lateral
geniculate body on the
same side of the brain,
and continue back to
the occipital lobe. If the
right optic tract were
destroyed, a person
would lose partial
vision in both eyes -
the right medial and the
left lateral fields of
vision.
31. 17-31
Ears & Hearing - Cochlea
Oval window attached to scala vestibuli (at base of
cochlea)
Vibrations at oval window induce pressure waves in
perilymph fluid of scala vestibuli
Scalas vestibuli & tympani are continuous at apex
So waves in vestibuli pass to tympani & displace round
window (at base of cochlea)
Necessary because fluids are incompressible & waves would not be
possible without round window
10-53
32. 17-32
Ears & Hearing - Cochlea
Low frequencies can travel all way thru vestibuli & back in
tympani
As frequencies increase they travel less before passing directly
through vestibular & basilar membranes to tympani
Fig 10.20
10-54
33. 17-33
Ears & Hearing - Cochlea
High
frequencies
produce
maximum
stimulation of
Spiral Organ
closer to base
of cochlea &
lower
frequencies
stimulate
closer to apex
10-55
34. 17-34
Spiral Organ (Organ of Corti)
Spiral Organ is
where sound is
transduced
Sensory hair cells
located on the
basilar membrane
1 row of inner
cells extend
length of basilar
membrane
Multiple rows of
outer hair cells
are embedded in
tectorial
membrane
10-56
35. 17-35
Spiral Organ (Organ of Corti)
Pressure waves moving thru cochlear duct
create shearing forces between basilar &
tectorial membranes, moving & bending
stereocilia
10-57
36. 17-36
Neural Pathway for Hearing
Info from 8th
nerve goes to
pons, then to
inferior
colliculus, then
to thalamus, &
to auditory
cortex
10-58
37. 17-37
Neural Pathways for Hearing
Neurons in
different
regions of
cochlea
stimulate
neurons in
corresponding
areas of
auditory cortex
Each area of
cortex
represents
different part of
cochlea & thus
a different pitch
10-59
38. 17-38
Vestibular Apparatus
Provides sense of
equilibrium
=orientation to gravity
Vestibular apparatus &
cochlea form inner ear
V. apparatus consists
of otolith organs
(utricle & saccule) &
semicircular canals
10-35
39. 17-39
Semicircular Canals
Provide information
about rotational
acceleration
Project in 3
different planes
Each contains a
semicircular duct
At base is crista
ampullaris where
sensory hair cells
are located
Fig 10.12
10-42
40. 17-40
Utricle and saccule provide info about linear
acceleration
Semicircular canals, oriented in 3 planes, give sense of
angular acceleration
Vestibular Apparatus
10-37
41. 17-41
Hair cells are receptors for equilibrium
Each contains 20-50 hair-like extensions called stereocilia
1 of these is a kinocilium
Vestibular Apparatus
10-38
42. 17-42
When stereocilia are bent toward kinocilium, hair cell
depolarizes & releases NT that stimulates 8th nerve
When bent away from kinocilium, hair cell hyperpolarizes
In this way, frequency of APs in hair cells carries information about
movement
Vestibular Apparatus
10-39
43. 17-43
Utricle & Saccule
Have a macula containing hair cells
Hair cells embedded in gelatinous otolithic membrane
Which contains calcium carbonate crystals (=otoliths) that resist
change in movement
10-40
44. 17-44
Utricle & Saccule
Utricle sensitive to
horizontal
acceleration
Hairs pushed
backward during
forward
acceleration
Saccule sensitive
to vertical
acceleration
Hairs pushed
upward when
person descends
10-41
45. 17-45
Semicircular Canals
Provide information
about rotational
acceleration
Project in 3
different planes
Each contains a
semicircular duct
At base is crista
ampullaris where
sensory hair cells
are located
10-42