Neurology | Descending Tracts: Vestibulospinal Tract
Summary
TLDRThis educational video script delves into the vestibular spinal tract, a crucial component of the nervous system responsible for activating extensor or anti-gravity muscles. It emphasizes the tract's role in maintaining posture and balance during linear and angular acceleration. The script explains the tract's origin in the vestibular nuclear complex, its stimulation from the inner ear and cerebellum, and its pathway to motor neurons. It also highlights the red nucleus's inhibitory function to prevent extensor hypertonus, ensuring a balanced muscle response.
Takeaways
- đ The video series will cover four descending tracks in the nervous system, focusing on the vestibular spinal tract in the first video.
- đ The vestibular spinal tract is primarily responsible for activating extensor muscles, which are crucial for posture and balance.
- đȘ The tract is particularly important for anti-gravity muscles, which help maintain posture and balance during linear and angular acceleration.
- đ The vestibular nuclear complex, located in the upper part of the medulla, is the main structure that receives stimuli for the vestibular spinal tract.
- đ Stimuli to the vestibular nuclear complex come from the inner ear structures, such as the macula and the cristae of the semicircular ducts, and from the cerebellum's vestibular and fastigial nuclei.
- đą The lateral and medial vestibular nuclei are the main components of the vestibular spinal tract, with the lateral controlling limb and trunk extension, and the medial controlling head and neck musculature.
- đ The vestibular spinal tract sends fibers down to the spinal cord, where they synapse with alpha and gamma motor neurons to control muscle contractions.
- đ The tract also has a role in controlling eye movement through connections with the oculomotor system, although this is not the main focus of the script.
- đ The red nucleus in the midbrain acts as an inhibitory control for the vestibular spinal tract, preventing excessive contraction of extensor muscles.
- đ Without the inhibitory control from the red nucleus, there could be a risk of extensor hypertonus, where the extensor muscles contract excessively.
- đ The script emphasizes the importance of understanding the function and control of the vestibular spinal tract for maintaining balance and posture during movement.
Q & A
What is the main function of the vestibulospinal tract?
-The main function of the vestibulospinal tract is to activate extensor muscles, specifically anti-gravity muscles that help maintain posture and balance.
What are the primary components of the vestibulospinal tract?
-The primary components of the vestibulospinal tract are the lateral vestibular nucleus and the medial vestibular nucleus.
Where is the vestibular nuclear complex located?
-The vestibular nuclear complex is located within the upper part of the medulla.
What stimuli do the vestibular nuclei receive?
-The vestibular nuclei receive stimuli from the macula in the utricle and saccule (which detect linear acceleration) and from the crista ampullaris in the semicircular ducts (which detect angular acceleration). Additionally, they receive proprioceptive information from the cerebellum.
What role does the cerebellum play in the vestibulospinal tract?
-The cerebellum provides proprioceptive information to the vestibular nuclear complex, helping it understand the position of muscles, tendons, joints, and ligaments, which is crucial for coordinating muscle contractions accurately.
What is the difference between the medial and lateral vestibulospinal tracts?
-The medial vestibulospinal tract primarily controls head and neck musculature, while the lateral vestibulospinal tract controls limb and trunk extensor muscles, which are important for maintaining posture and balance.
How does the vestibulospinal tract interact with motor neurons?
-The vestibulospinal tract sends descending fibers to the spinal cord, where they stimulate alpha and gamma motor neurons in the anterior or ventral gray horn. These motor neurons then innervate extensor muscles to maintain posture and balance.
What is the role of the red nucleus in the vestibulospinal tract system?
-The red nucleus provides inhibitory signals to the vestibular nuclear complex, preventing excessive contraction of extensor muscles and ensuring proper muscle tone.
What happens if the inhibitory signals from the red nucleus are absent?
-If inhibitory signals from the red nucleus are absent, it could lead to extensor hypertonus, where extensor muscles contract excessively.
What additional function does the vestibular nuclear complex have besides controlling extensor muscles?
-The vestibular nuclear complex can also send fibers to control eye movements via the medial longitudinal fasciculus, influencing the third, fourth, and sixth cranial nerves.
Outlines
đ Introduction to the Vestibular Spinal Tract Series
This introductory paragraph sets the stage for a four-part series focusing on various descending tracks, starting with the vestibular spinal tract in this video. The speaker emphasizes the importance of understanding the ultimate function of each tract, especially the vestibular spinal tract's role in activating extensor muscles, also known as anti-gravity muscles, which are crucial for posture and balance. The paragraph also mentions the need to revisit the vestibular pathway for those who have seen previous content on the subject, highlighting the value of repetition in learning.
đ Detailed Exploration of the Vestibular Spinal Tract
The speaker delves into the specifics of the vestibular spinal tract, explaining its origin from the vestibular nuclear complex located in the medulla and the stimuli it receives from the inner ear structures, such as the macula and the cristae of the semicircular ducts, as well as from the cerebellum via the vestibular and fastigial nuclei. The paragraph clarifies the roles of the medial and lateral vestibular nuclei in forming the tract and their respective influences on head, neck, and limb/trunk muscles. The speaker also describes the pathway of the vestibular spinal tract fibers as they descend through the spinal cord and synapse laterally with alpha and gamma motor neurons, which in turn control the contraction of extensor muscles.
đ The Role of the Red Nucleus in Regulating the Vestibular Spinal Tract
In this concluding segment, the speaker introduces the red nucleus as a regulatory component of the vestibular spinal tract system. The red nucleus sends inhibitory signals to the vestibular nuclear complex to prevent excessive contraction of the extensor muscles, thus acting as a 'brake' system. The speaker also touches on the broader implications of the vestibular system, including its influence on eye movement control through the medial longitudinal fasciculus and the importance of the red nucleus's regulatory role in maintaining proper muscle tone and preventing extensor hypertonus.
Mindmap
Keywords
đĄVestibular Spinal Tract
đĄExtensor Muscles
đĄAnti-Gravity Muscles
đĄVestibular Nuclear Complex
đĄMacula
đĄSemicircular Ducts
đĄCerebellum
đĄRed Nucleus
đĄAlpha and Gamma Motor Neurons
đĄExtensor Hypertonus
đĄMedial and Lateral Vestibular Spinal Tracts
Highlights
The four-part series discusses descending tracks, focusing on the vestibular spinal tract in this video.
The vestibular spinal tract primarily activates extensor muscles, which are crucial for anti-gravity and posture maintenance.
The vestibular nuclear complex, located in the medulla, receives stimuli from the inner ear and cerebellum for balance and posture control.
The macula and cristae ampullares from the inner ear provide information on linear and rotational acceleration to the vestibular nuclear complex.
The lateral and medial vestibular nuclei are the main components of the vestibular spinal tract, with distinct roles in musculature control.
The lateral vestibular nucleus controls limb and trunk extension, while the medial nucleus manages head and neck musculature.
The cerebellum's fastigial and vestibular nuclei send proprioceptive information to the vestibular nuclear complex for coordinated muscle contraction.
Vestibular spinal tract fibers descend into the spinal cord, synapsing laterally with alpha and gamma motor neurons.
Alpha motor neurons are responsible for muscle fiber contraction, while gamma neurons maintain muscle spindle tightness.
The medial vestibular spinal tract targets head and neck muscles, specifically in the cervical region of the spinal cord.
The lateral vestibular spinal tract stimulates axial and appendicular extensors for posture and balance against gravity.
The red nucleus in the midbrain inhibits the vestibular nuclear complex to prevent excessive extensor contraction.
Extensor hypertonus can occur without the red nucleus's inhibitory control, leading to over-contraction of extensor muscles.
The vestibular system also influences eye movement through connections with the medial longitudinal fasciculus and related cranial nerves.
The ultimate goal of the vestibular spinal tract is to control anti-gravity muscles for posture and balance during linear and angular acceleration.
The red nucleus acts as a brake system for the vestibular spinal tract to ensure proper muscle tone and prevent hyperactivity.
Transcripts
iein engineers join us in this four-part
series where we're gonna talk about
descending tracks we're gonna talk about
four individual ones okay so four
separate videos the first video then
we're gonna talk about in this one is
gonna be the vestibular spinal track so
we're gonna talk about that one in this
video the next video we're gonna talk
about the Ponto reticulospinal tract
then we'll talk about the rubra spinal
tract and then finally we'll finish off
with the medullary reticulospinal tract
so let's go ahead and start first on the
vestibular spinal tract alright so let's
go ahead and SART a little bit stupido
spinal tracts so if you guys haven't
already watched the vestibular cochlear
nerve the vestibular pathway we actually
talked about this tract and pretty good
detail in that so if you haven't go
watch that too or anyway we're gonna
cover it again because repetition is
always good alright so the vestibular
spinal tract here's the big thing that I
want to get out of all these videos I
want you guys to remember the ultimate
termination or destination or function
of this track this track this vestibular
spinal tract is mainly going to activate
extensor muscles
extensor muscles but to even be a little
bit more specific
this vestibular spinal tract is also
important for anti-gravity muscles
posture muscles and we'll explain why
but I want you to remember that it's
primarily for extensor muscles but we
can classify this as our anti-gravity
anti-gravity muscles helps to maintain
our posture and and balance right so
anti-gravity muscles okay now why is
this well there's a special set of
nuclear this is your vestibular nuclear
complex your vestibular nuclear complex
is located within the medulla right the
upper part of the medulla so this is our
vestibular nuclear complex and this is
our vestibular nuclear complex you have
our right one and a left one all right
so here's the right side here's the left
side now where do these nuclei get
stimuli from they get it from two
different stimuli so what is the
stimulus well it comes from two
different stimuli one is in the inner
ear you know in the inner ear you have
the macula and the macula if you
remember that was located in the utricle
and the saccule they respond to linear
acceleration but another one was
actually going to be within the
semicircular ducts specifically in the
ampulla of the semicircle a box they
called it the cris day and Belarus if
you remember these two structures gave
what they gave that vestibular branch of
the vestibulocochlear nerve and that
vestibular branch of the
vestibulocochlear nerve came and ended
up on this vestibular nuclear complex
alright now what did it do from that
point remember there's the vestibular
nuclear complex has the superior the
inferior the medial and the lateral
vestibular nucleus why am I telling you
this the reason why is the lateral
vestibular nucleus and the medial
vestibular nucleus are the main
components of this vestibular spinal
tract ire so the medial and the lateral
are the main components of the
vestibular meinl tract
now there's two different stimulations
we said one is coming from the inner ear
right from the macula which is detecting
linear acceleration so pretend you're in
a vehicle and you just hit the hit the
gas or you hit the brakes really fast
either one that they're shifting within
the inner ear which helps to send that
information to the vestibular nuclear
complex another one is if you're lit
you're actually rotational or angular
lis accelerating that activates the
chrisstambo layers and tells the
vestibular nuclear complex of that
there's another situation you know in
the cerebellum here's your cell or
cerebellum right here there's different
types of nuclei in here you know there's
a special nucleus and it's called the
vestigial nucleus and the fastidian
nucleus can actually send information
out to this vestibular nuclear complex
and tell this vestibular nuclear complex
about what the cerebellum knows about
it's proprioception so you know
proprioception is basically the position
of your muscles your tendons your joints
your ligaments our cerebellum has
constant awareness of where our limbs
and our body is in space so the
cerebellum has a way of telling these
vestibular nuclei hey I know where the
arm is I know where the legs are so here
take this information so that whenever
you have these movements these
descending fibers coming down you tell
the muscles exactly how they should
contract in the exact direction the
exact way that they should do it it's a
beautiful system so two different
stimuli one it's coming from the
vestigial nucleus within the cerebellum
and the other one is coming from the
inner ear structure specifically the
macula and the Christian pilaris
now once they get their stimulus like I
told you the lateral and the medial the
ones that are actually primarily forming
the vestibular spinal tract but even
more I want you to remember is most of
the fibers are coming from the lateral
the reason why is the lateral is
controlling specific types of
musculature right so the medial controls
more of your head and neck musculature
all right being able to maintain the
movement of our head and our posture
whenever we're actually Road
accelerating right in the rotational
direction or linearly accelerating we
want to be able to maintain our actual
muscle tone within the head and neck
muscles the lateral vestibular spinal
tract is controlling more of the actual
limb and even trunk extension all right
so that's why it's important so now
let's bring these guys down though okay
so they're gonna come down these fibers
these this actual vestibular spinal
tract when they come down they're going
to go into the actual into the spinal
cord now as they go down through the
spinal cord they're going to give
stimulation it see laterally if see
laterally to the actual cell bodies of
the actual alpha and gamma motor neurons
located within the anterior or ventral
great horn so let's say they here I have
these cell bodies right here right and
let's say I pretend that these are my
alpha motor neurons and then right
adjacent to it all I have maybe I'll
have some gamma motor neurons so over
here I'll have some gamma motor neurons
what would these guys do from here these
alpha motor neurons are going to come
out and go to specific types of muscles
what muscles will they be going to we
said that they're going to extensor
muscles or anti-gravity muscles right or
muscles that help to maintain our
posture and our balance when we're
linearly or rotating accelerating in a
rotational direction now we said if it's
the medial let's pretend that these are
for the medial let's just say these are
for the medial vestibular spinal tract
if this is for the medial vestibular
the Simula spinal tract if this is for
the medial vestibular spinal tract this
will only be going to what type of
muscles you have to remember this this
is for the head
and neck muscles all right this is for
the medial vestibular spinal tract
headed neck muscles so let's pretend
that this is like the cervical section
with spinal cord okay pretend for a
second that this right here is the
cervical section this is the cervical
section of the spinal cord all right so
it's going to be going to the head and
neck muscles now let's say that we keep
following these down so let's say that
we keep following these guys down and
let's presume that now this is going to
be the lateral force stimulus spinal
tract right so now the lateral
vestibular spinal tract is gonna come
over here and go epsy laterally on to
some alpha and gamma motor neurons that
are located within the anterior grey
Horn of the spinal cord and what will
they do they'll come out and stimulate
these actual muscles if you guys haven't
already watched the corticospinal video
you guys will member remember that the
gamma is specifically for the muscle
spindles right to maintain the actual
tightness of the muscle spindles the
Alpha is for the extra fuse of muscle
fibers the muscle fibers that actually
contract and shorten and lengthen the
muscle all right now if it is the
lateral if it is the lateral vestibular
spinal tract the lateral of a stimulus
Pinal tract what type of muscles will
this be going to this will be going to
more of the axial and the appendicular
and appendicular extensors
okay so it's going to be going Sun to
the some of the axial and the athlete
appendicular extensors if you think
about it we want to have these muscles
contracting right to be able to maintain
our posture and our balance and the
right to resist gravity but here's the
important thing there has to be some way
that we could have put a brake on this
system this system has to constantly
whenever it's not necessarily needs to
be stimulated whenever it doesn't need
to be stimulated we need to have some
brake on it way that we can control it
we get my red marker here there's a
special nucleus located within the
midbrain and this nucleus is called the
red nucleus right it's called the red
nucleus the red nucleus can come down
here and inhibit the vestibular nuclear
complex and prevent these actual
vestibular spinal tracts from going down
why to prevent excessive contraction of
the extensors if this this is actually
going to be coming from again.what
nucleus the red nuclei here if these
guys aren't sending these inhibitory
pathways down to the vestibular nuclei
you know what could happen it could
cause what's called extensor hyper tonus
where the extensor muscles are so
crazily contracted more than they need
to be so to prevent that from happening
we have a brake system here and that's
this red nucleus okay they can give
inhibitory descending fibers to inhibit
these vestibular nuclei from
continuously stimulating the actual
vestibular spinal tract via the medial
and the lateral and there's another way
remember I told you that whenever you're
rotating linearly or if you're doing
linear acceleration or angular
acceleration you have to move your head
and neck you have to maintain posture
and balance right but what else did you
do you move your eyes there's another
one we're not going to talk about it but
remember that the vestibular nucleus can
also send fibers upwards to control eye
movement you have the third nerve the
fourth cranial nerve and the sixth
cranial nerve if you remember that was
called the medial longitudinal
fasciculus okay so basic thing that I
want you guys to get out of this is the
vestibular spinal tract it controls your
extensor muscles or you
anti-gravity muscles to maintain posture
and balance during linear and angular
acceleration what are the two stimuli
the inner ear structures macula Kristine
Belarus and it gets some modification
from the vestigial nucleus within the
cerebellum
what's its ultimate goal to send down
via medial and lateral vestibular spinal
tracts into the spinal cord if it's
going to the cervical region it's going
to be the medial supplying the head and
neck muscles and if it's going to more
axial more of the appendicular skeleton
what is it going to be supplying it's
then going to be supplying to be
supplied by the lateral vestibular
spinal tract and then remember we have
to have a brake system on this tract
which is gonna be coming from the red
nucleus ionizer so we covered the
vestibular spinal tract now in the next
video
we're gonna go and talk about the Ponto
reticulospinal tract I'll see you guys
there
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you
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