EXAM 4
15-11-2017 Monday
Newslide Motor Systems
- Themes :
o Qn: Comatose patient ends in the ER, and you
press on the glabella ( where the superciliary
ridges meet) : You will be able to see a typical
posture which will signify the location of the
seizure.
o Maintaining posture while performing in skillful
movements
▪ Corticospinal :
• Lateral corticospinal tract
o Reflex movement of head and neck
towards a stimulus.
▪ Eg: Bomb goes off in one side of the
class.
▪ Tectospinal tract that will help in reflex movements that will help in auditory or visual
stimulus.
- Players in motor control :
o LMN helps in performing motor functions and therefore it is the final common pathway.
o Circuits that help in UMN:
▪ Basal ganglia:
• This is an initiator and integrator of motor movement.
▪ Cerebellum
• This is a coordinator and the predictor.
o Cerebellum+ basal ganglia → UMN → LMN
o Another group of tracts called extrapyramidal tracts starts from the brain stem:
▪ Rubrospinal + tectospinal from the midbrain
▪ Reticulospinal: Mainly from pons
▪ Vestibulospinal : Medulla +pons
- Overview of the motor system:
o Direct activation pathway : UMN/Corticospinal tracts/ pyramidal tract.
o Control circuits:
▪ These control circuits are controlling the motor movement/ LMN fibres through the UMN fibres.
▪ Includes cerebellum and basal ganglia.
o Indirect activation pathway :
▪ The extrapyramidal tracts.
o Final common pathway : LMN
▪ Qn: NT released by LMN: Ach as the LMN forms NMJs as they are innervating the muscles.
,- Corticospinal tracts :
o It starts from the primary motor cortex. (90% of fibres).
o The rest of the fibres are from supplementary motor cortex and the premotor cortex.
o The homunculus of the precentral gyrus:
▪ Hands have the most somatotopy as the hands are for most skillful movements.
o The 6 layers are arranged ascortical columns ( perpendicular to the pial surface)
▪ Layer 4 receives the input from the thalamus (VA,VL) GO BACK. VA VL recives information from
basal ganglia and cerebellum
▪ Basal ganglia + cerebellum → VA VL nucleus → Layer 4 of the cortex → Layer 5 of the cortex
that has pyramidal cells (BETZ cells) → UMN
o Tract :
▪ The fibres/ axons will form a crown like structure called corona radiate and will
bundle together and will pass through the posterior limb of internal capsule → cerebral
peduncles in the midbrain through the middle 1/3rd . This means that the tracts are coming
from posterior part of the internal capsule to the anterior part of the midbrain.
▪ It will pass through the basis pontis where the fibres will split because of pontine nuclei. They
will again bundle and will form the pyramids of the medulla. At the caudal aspect, the fibres
lateral corticospinal tracts as it
decussate to the opposite side to become the
assumes a position in the lateral funiculus of the spinal cord. The reminder will form
the anterior corticospinal tracts.
▪ Lateral corticospinal tracts will end on the lateral aspect of ventral horn/ lateral motor
neurons :
• Distal musculature
• Flexor group of motor neurons.
• Termination of lateral corticospinal tract is contralateral.
▪ Anterior corticospinal tract will terminate on the medial motor neurons
• The medial motor neurons will innervate the axial musculature.
• Extensors : Extensors are more important for posture.
• Therefore anterior corticospinal tracts will maintain posture during voluntary
movements. Spinocerebellar tracts will give unconscious proprioception.
▪ There are corticospinal tracts that start in the post central gyrus of the cortex (123) and end in
the dorsal horn, that will give you sensations of your movements.
- Corticofugal projections :
o Corticobulbar tracts: They start in the cortex and end in the cranial nerve nuclei.
▪ All have bilateral terminations in the cranial nerve nucleus in the brain stem except:
• 7 lower part of Facial nucleus
• 12 and NA.
o Corticopontine :
▪ Cortex → basis pontis (pontine nuclei)
▪ Passes through the anterior limb of the internal capsule.
o Corticorubral :
▪ Cortex → red nucleus (receives fibres from the opposite cerebellum; lesion here will cause
contralateral gait ataxia)
,- Control circuits :
o This includes the cerebellum and the basal ganglia.
o Even before we start moving , the impulses are in the basal ganglia. Out of the 5 key players, the GP
internum is the main output that will end in the VA VL nucleus of the thalamus. Therefore
particularly, the impulses start from the globus pallidum. Therefore this part of the basal ganglia is called
prime mover.
▪ This was tested by using a monkey, by using an fMRI.
o Cerebellum:
▪ GLu : Granule cells
• Mossy fibres and climbing fibres.
▪ All other cells will release GABA.
- Indirect activation pathways / extrapyramidal tracts :
o All the indirect activation pathways will start from the brain stem.
o Functions
▪ They control the tone of the muscle.
▪ Controls movements of head and neck.
▪ Maintenance of image on the retina:
• Vestibulospinal tracts support the head and the eye movements important for
vestibulooccular reflex.
o Extrapyramidal Tracts :
▪ In the midbrain :
• Rubrospinal tract :
o Starts from the red nucleus in the midbrain.
• Tectospinal tract :
o It starts in the midbrain tectum → spinal.
• (The reticular formation in the midbrain is important of cortical arousal. Bilateral lesion
here will lead to a vegetative coma state.
▪ In pons and medulla
• Reticulospinal :
o There are two types :
▪ Pontine Reticulospinal tract : For extension and thus posture.
▪ Medullary Reticulospinal tract. : For flexion and thus flexing.
o (The reticular formation in the midbrain is important of cortical arousal. Bilateral
lesion here will lead to a vegetative coma state.
• Vestibulospinal pathway
o Medial Vestibulospinal :
▪ Starts from the medial vestibular nuclei.
o Lateral Vestibulospinal :
▪ Starts from the lateral vestibular nuclei.
- All these pathways can be divided into two :
o Tonic system
▪ Tonic means Constantly active whether you need it or not.
, • Tectospinal
• Pontine Reticulospinal
• Vestibulospinal
▪ They have a constant control .
▪ extensor group of motor neurons and thus is important for
Tonic systems always work on
posture and balance. These innervate the antigravity muscles.
o Phasic system
▪ They start from the cortex , midbrain and the medulla and they are only active when needed.
▪ ****
• Rubrospinal is only active when required.
• Medullary Reticulospinal
▪ Phasic is related to flexor group of muscles and it is only active when required.
- Final common
pathway :
o LMN executes the
voluntary movements.
o Nicotinic receptors for
Ach are found at the
NMJ.
o There are also
interneurons in the
ventral horn cells that
will regulate the
▪ Proximal
▪ Distal
musculature.
- Descending tracts :
o Rubrospinal
tract :
INHIBTORY
▪ Forms a part along with the lateral corticospinal tract in the lateral funiculus and this is
innervating the flexors and the distal musculature.
▪ Starts from the Red nucleus and end in the spinal cord.
▪ It ends in the cervical levels and thus will only have effects on upper limbs.
▪ Function : Flexion as it is present on the lateral funiculus.
▪ Corticorubral fibres will inhibit the red nucleus , in animals , there is no inhibiton
and this is why the animals can run superfast with all the four limbs.
• Cutting the COrtico-rubral fibres will lead to flexion of the upper limbs. It is usually due
to a massive stroke and the person is usually in a coma.
▪ Cortex → red nucleus → upper cervical spinal cord.
▪ It decussates at the level of the red nucleus. Termination is contralateral.
▪ It terminates exclusively on alpha motor neurons on the upper
limbs.
15-11-2017 Monday
Newslide Motor Systems
- Themes :
o Qn: Comatose patient ends in the ER, and you
press on the glabella ( where the superciliary
ridges meet) : You will be able to see a typical
posture which will signify the location of the
seizure.
o Maintaining posture while performing in skillful
movements
▪ Corticospinal :
• Lateral corticospinal tract
o Reflex movement of head and neck
towards a stimulus.
▪ Eg: Bomb goes off in one side of the
class.
▪ Tectospinal tract that will help in reflex movements that will help in auditory or visual
stimulus.
- Players in motor control :
o LMN helps in performing motor functions and therefore it is the final common pathway.
o Circuits that help in UMN:
▪ Basal ganglia:
• This is an initiator and integrator of motor movement.
▪ Cerebellum
• This is a coordinator and the predictor.
o Cerebellum+ basal ganglia → UMN → LMN
o Another group of tracts called extrapyramidal tracts starts from the brain stem:
▪ Rubrospinal + tectospinal from the midbrain
▪ Reticulospinal: Mainly from pons
▪ Vestibulospinal : Medulla +pons
- Overview of the motor system:
o Direct activation pathway : UMN/Corticospinal tracts/ pyramidal tract.
o Control circuits:
▪ These control circuits are controlling the motor movement/ LMN fibres through the UMN fibres.
▪ Includes cerebellum and basal ganglia.
o Indirect activation pathway :
▪ The extrapyramidal tracts.
o Final common pathway : LMN
▪ Qn: NT released by LMN: Ach as the LMN forms NMJs as they are innervating the muscles.
,- Corticospinal tracts :
o It starts from the primary motor cortex. (90% of fibres).
o The rest of the fibres are from supplementary motor cortex and the premotor cortex.
o The homunculus of the precentral gyrus:
▪ Hands have the most somatotopy as the hands are for most skillful movements.
o The 6 layers are arranged ascortical columns ( perpendicular to the pial surface)
▪ Layer 4 receives the input from the thalamus (VA,VL) GO BACK. VA VL recives information from
basal ganglia and cerebellum
▪ Basal ganglia + cerebellum → VA VL nucleus → Layer 4 of the cortex → Layer 5 of the cortex
that has pyramidal cells (BETZ cells) → UMN
o Tract :
▪ The fibres/ axons will form a crown like structure called corona radiate and will
bundle together and will pass through the posterior limb of internal capsule → cerebral
peduncles in the midbrain through the middle 1/3rd . This means that the tracts are coming
from posterior part of the internal capsule to the anterior part of the midbrain.
▪ It will pass through the basis pontis where the fibres will split because of pontine nuclei. They
will again bundle and will form the pyramids of the medulla. At the caudal aspect, the fibres
lateral corticospinal tracts as it
decussate to the opposite side to become the
assumes a position in the lateral funiculus of the spinal cord. The reminder will form
the anterior corticospinal tracts.
▪ Lateral corticospinal tracts will end on the lateral aspect of ventral horn/ lateral motor
neurons :
• Distal musculature
• Flexor group of motor neurons.
• Termination of lateral corticospinal tract is contralateral.
▪ Anterior corticospinal tract will terminate on the medial motor neurons
• The medial motor neurons will innervate the axial musculature.
• Extensors : Extensors are more important for posture.
• Therefore anterior corticospinal tracts will maintain posture during voluntary
movements. Spinocerebellar tracts will give unconscious proprioception.
▪ There are corticospinal tracts that start in the post central gyrus of the cortex (123) and end in
the dorsal horn, that will give you sensations of your movements.
- Corticofugal projections :
o Corticobulbar tracts: They start in the cortex and end in the cranial nerve nuclei.
▪ All have bilateral terminations in the cranial nerve nucleus in the brain stem except:
• 7 lower part of Facial nucleus
• 12 and NA.
o Corticopontine :
▪ Cortex → basis pontis (pontine nuclei)
▪ Passes through the anterior limb of the internal capsule.
o Corticorubral :
▪ Cortex → red nucleus (receives fibres from the opposite cerebellum; lesion here will cause
contralateral gait ataxia)
,- Control circuits :
o This includes the cerebellum and the basal ganglia.
o Even before we start moving , the impulses are in the basal ganglia. Out of the 5 key players, the GP
internum is the main output that will end in the VA VL nucleus of the thalamus. Therefore
particularly, the impulses start from the globus pallidum. Therefore this part of the basal ganglia is called
prime mover.
▪ This was tested by using a monkey, by using an fMRI.
o Cerebellum:
▪ GLu : Granule cells
• Mossy fibres and climbing fibres.
▪ All other cells will release GABA.
- Indirect activation pathways / extrapyramidal tracts :
o All the indirect activation pathways will start from the brain stem.
o Functions
▪ They control the tone of the muscle.
▪ Controls movements of head and neck.
▪ Maintenance of image on the retina:
• Vestibulospinal tracts support the head and the eye movements important for
vestibulooccular reflex.
o Extrapyramidal Tracts :
▪ In the midbrain :
• Rubrospinal tract :
o Starts from the red nucleus in the midbrain.
• Tectospinal tract :
o It starts in the midbrain tectum → spinal.
• (The reticular formation in the midbrain is important of cortical arousal. Bilateral lesion
here will lead to a vegetative coma state.
▪ In pons and medulla
• Reticulospinal :
o There are two types :
▪ Pontine Reticulospinal tract : For extension and thus posture.
▪ Medullary Reticulospinal tract. : For flexion and thus flexing.
o (The reticular formation in the midbrain is important of cortical arousal. Bilateral
lesion here will lead to a vegetative coma state.
• Vestibulospinal pathway
o Medial Vestibulospinal :
▪ Starts from the medial vestibular nuclei.
o Lateral Vestibulospinal :
▪ Starts from the lateral vestibular nuclei.
- All these pathways can be divided into two :
o Tonic system
▪ Tonic means Constantly active whether you need it or not.
, • Tectospinal
• Pontine Reticulospinal
• Vestibulospinal
▪ They have a constant control .
▪ extensor group of motor neurons and thus is important for
Tonic systems always work on
posture and balance. These innervate the antigravity muscles.
o Phasic system
▪ They start from the cortex , midbrain and the medulla and they are only active when needed.
▪ ****
• Rubrospinal is only active when required.
• Medullary Reticulospinal
▪ Phasic is related to flexor group of muscles and it is only active when required.
- Final common
pathway :
o LMN executes the
voluntary movements.
o Nicotinic receptors for
Ach are found at the
NMJ.
o There are also
interneurons in the
ventral horn cells that
will regulate the
▪ Proximal
▪ Distal
musculature.
- Descending tracts :
o Rubrospinal
tract :
INHIBTORY
▪ Forms a part along with the lateral corticospinal tract in the lateral funiculus and this is
innervating the flexors and the distal musculature.
▪ Starts from the Red nucleus and end in the spinal cord.
▪ It ends in the cervical levels and thus will only have effects on upper limbs.
▪ Function : Flexion as it is present on the lateral funiculus.
▪ Corticorubral fibres will inhibit the red nucleus , in animals , there is no inhibiton
and this is why the animals can run superfast with all the four limbs.
• Cutting the COrtico-rubral fibres will lead to flexion of the upper limbs. It is usually due
to a massive stroke and the person is usually in a coma.
▪ Cortex → red nucleus → upper cervical spinal cord.
▪ It decussates at the level of the red nucleus. Termination is contralateral.
▪ It terminates exclusively on alpha motor neurons on the upper
limbs.
