Lecture 3 Flashcards

1
Q

Every level of the NS can generate ___.

A

movement

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2
Q

The primary motor cortex, as you can see is a target of the ___ ____, and the ___. It gives input to the brainstem from the spinal cord and generates downward commands to everything.

A

The primary motor cortex, as you can see is a target of the basal ganglia, and the cerebellum. It gives input to the brainstem from the spinal cord and generates downward commands to everything.

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3
Q

Sensory inputs guide movement. Sensory inputs in the spinal cord help to control alpha motor neurons. Sensory inputs in the cerebellum help keep us coordinated. Sensory inputs in the basal ganglia help us decide which movements to make. Sensory and motor are inseparable to each other, although we separate them conceptually all the time.

A
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4
Q

The _____ tract is what conveys axial and motor control. This is the pathway that lets the brain control the movement of muscles.This pathway begins in the ____gyrus (the primary motor cortex).Our journey begins with two neurons. One will ultimately innervate the axial muscles, and the other will innervatethe limb muscles. They leave the cortex by descending through the internal capsule and into the brain stem.As the pathway descends ino the medulla, __% to ___% of the fibers decussate in the pyramids. The ___ fibers do not decussate though.After leaving the brainstem, the fibers run down the two corticospinal tracts (the ___ __ tract, and the __ __tracts).When they get to their target level, the fibers of the anterior corticospinal tract finally decussate through the __ __ __ before synapsing to aneuron in the ventromedial ventral hornof the grey matter.Conversely, thefibers of the lateral corticopspinal tract have already decussated at the level of the pyramids. As such when the fibers of the lateral corticospinal tractget to the appropriate level, They just synapse onto a neuron in the dorsolateral ventral horn and intermediate zone.It is worth noting that the neurons in the cortex are known as ___ __ ___ and a lesion any where in these fibers (from the cortex all the way down to the dorsolateral ventral horn and intermediate zone) are known as __ __ __lesions. These neurons in the ventral horn (ventralhorn cells) then project to the limb muscles and to the axial muscles. These neurons are known as __ ___neurons and as such, a lesion between the anterior horn and the muscle are known as ___ lesions.In summary, the ___ tract is a two neuron pathway. There is an upper motor neuron which arises in the cortex, and a lower motor neuron, which arises in the anterior horn. The limb pathway decussate at the pyrimidsin the medulla and the axial pathway decussates through the anterior white commissure in the spinal cord.

A

The corticospinaltract is what conveys axial and motor control. This is the pathway that lets the brain control the movement of muscles.This pathway begins in the pre-centralgyrus (the primary motor cortex).Our journey begins with two neurons. One will ultimately innervate the axial muscles, and the other will innervatethe limb muscles. They leave the cortex by descending through the internal capsule and into the brain stem.As the pathway descends ino the medulla, 75% to 90% of the fibers decussate in the pyramids. The axial fibers do not decussate though.After leaving the brainstem, the fibers run down the two corticospinal tracts (the lateral corticospinaltract, and the anterior corticospinal tracts).When they get to their target level, the fibers of the anterior corticospinal tract finally decussate through the anterior white commissure before synapsing to aneuron in the ventromedial ventral hornof the grey matter.Conversely, thefibers of the lateral corticopspinal tract have already decussated at the level of the pyramids. As such when the fibers of the lateral corticospinal tractget to the appropriate level, They just synapse onto a neuron in the dorsolateral ventral horn and intermediate zone.It is worth noting that the neurons in the cortex are known as upper motor neurons, and a lesion any where in these fibers (from the cortex all the way down to the dorsolateral ventral horn and intermediate zone) are known as UMNlesions.These neurons in the ventral horn (ventral horn cells) then project to the limb muscles and to the axial muscles. These neurons are known as LM neurons and as such, a lesion between the anterior horn and the muscle are known as LMN lesionsIn summary, the corticospinal tract is a two neuron pathway. There is an upper motor neuron which arises in the cortex, and a lower motor neuron, which arises in the anterior horn. The limb pathway decussate at the pyrimidsin the medulla and the axial pathway decussates through the anterior white commissure in the spinal cord.

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5
Q

The lateral system of the corticospinal tract:__ musculatureTerminates only ___Focused terminationsTerminate on motor neurons and interneurons.The medial system of the corticospinal tract:__ and __ musclesTerminates ___Terminates widelyTerminates only on ___.

A

The lateral system of the corticospinal tract:Distal musculatureTerminates only contralaterallyFocused terminationsTerminate on motor neurons and interneurons.The medial system of the corticospinal tract:Axial and proximalmusclesTerminates bilaterallyTerminates widelyTerminates only on interneurons

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6
Q

There are tons of inerneurons in the ___ zone of the spinal cord, in between the dorsal and ventral horn. They project into these alpha motor neurons aka ___.They are cholinergic (they use theNT, acetocholine, to get their messges through).

A

There are tons of inerneurons in the intermediatezone of the spinal cord, in between the dorsal and ventral horn. They project into these alpha motor neurons aka LMNs.They are cholinergic (they use theNT, acetocholine, to get their messages through).

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7
Q

___ damage produces characteristic syndromes:Paralysis or paresis (weakness)Loss of muscle toneHyporeflexia or loss of reflexesFasciculation and fibrillation (muscle fibers start to fire on their own)Muscle atrophy (why?)

A

LMN damage produces characteristic syndromes:Paralysis or paresisLoss of muscle toneHyporeflexia or loss of reflexesFasciculation and fibrillation (muscle fibers start to fire on their own)Muscle atrophy (Why?)–> It turns out that LMN not only activates muscles by releasing ACh, but they release trophic factors that the muscles need to be healthy. If you remove the trophic factors the muscles willatrophy.

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8
Q

Whatfour brainstem pathways contribute to their medial system? What are they and what do they do?

A
  1. Tectospinal - responsible for visually tracking moving objects. It arises in the superior colliculus. The fibers decussate immediately, and travel down the ventral columns to the upper level of the spinal cord (mainly for neck and upper body muscles).2. Reticulospinal - originates in the pons and medulla. It has an ipsilateral course and controls automatic posture and gait-related movements.3. Vestibulospinal tracts - receives input from vestibular nerve and from cerebellum. Descending projections help control postural adjustment. Ascending projections modulate eye movement. The descending projections keeps us upright and keeps our head oriented to gravity and earth.4. Anterior corticospinal tract - (10% of fibers in pyrmids. Decussate with other corticospinal fibers. Travel in anterior columns. Bilateral terminations.Originates from primary motor cortex and supplementary motor area. It controls bilateral axial and girdle muscles.
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9
Q

Motor cortex is the main contributor to the __ __ tract. This tract, although most of the contribution comes from the motor cortex, there is some cotribution from the somatosensory cortex. So the motor corticospinal neurons terminate in ventral horn and the comoponent that tract S1 terminates in dorsal horn where they control afferent input from muscle spindles

A

corticospinal tract

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10
Q

A stroke in the pons causes ___ ___ syndrome.

A

Locked-in syndrome. You can destroy the entire descendnig corticospinal system and leave a person unable to move except for some eye blinks and eye movement. They are conscious and alert and cognitively capable but completely paralyzed.

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11
Q

The corticospinal tract passes through the __ ___. The head portion or face portion of the corticospinal tract is through the __ of the internal capsule. The arms, trunksand legs pass through the __ __ of the internal capsule. You can get strokes there and you can get very weird syndromes such as complete paralysisof the lower body but not the head.From the internal capsule, they pass into the __ __and then into the ventral pons, where they are kind of spread out into big fasicles. They then coalesce in the medulla and go into the __ where they decussate. After the pyramids they go into the lateral corticospinal tract.Again, the reason to know the pathway is because different kinds of strokes will involve different portions of the corticospinal tract, and the symptoms are diagnostic. There are strokes in the pons that causes a thing called “___-____syndrome, where you can destroy the entire descending corticospinal system and leave a person unable to move except for eye movements and blnkings. In this syndrome, they are conscious and alert but completely paralyzed.

A

The corticospinal tract passes through the internal capsule. The head portion or face portion of the corticospinal tract is through the genu of the internal capsule. The arms, trunksand legs pass through the posterior horn of the internal capsule. You can get strokes there and you can get very weird syndromes such as complete paralysisof the lower body but not the head.From the internal capsule, they pass into the cerebral peduncles and then into the ventral pons, where theyspread out into big fasicles. They then coalesce in the medulla and go into the pyramids where they decussate. After the pyramids they go into the lateral corticospinal tract. Again, the reason to know the pathway is because different kinds of strokes will involve different portions of the corticospinal tract, and the symptoms are diagnostic. There are strokes in the pons that causes a thing called “locked-in” syndrome, where you can destroy the entire descending corticospinal system and leave a person unable to move except for eye movements and blnkings. In this syndrome, they are conscious and alert but completely paralyzed.

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12
Q

___ tract - these are the fibers that are going to the cranial nerves. They travel the same route: through the internal capsule and then thecerebral peduncles, butthey start dropping off as they get to the midbrain. There are fibers that go to different cranial nerves. These fibers are called ___ fibers.

A

Corticobulbartract - these are the fibers that are going to the cranial nerves. They travel the same route: through the internal capsule and then thecerebral peduncles, butthey start dropping off as they get to the midbrain. There are fibers that go to different cranial nerves. These fibers are called corticobulbar fibers.

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13
Q

If you get a lesion of the corticospinal system, you get ___syndromes. You get the loss of fine movements, and eventually (unlike LMN syndrome), UMN syndrome will evolveinto __ (increase in muscle tone, ___ and a ___ sign). Remember, UMN lesions, everything goes UP!

A

If you get a lesion of the corticospinal system, you get UMNsyndromes. You get the loss of fine movements, and eventually (unlike LMN syndrome), UMN syndrome will evolveinto spasticity (increase in muscle tone, hyperreflexia and a babinski sign). Remember, UMN lesions, everything goes UP!

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14
Q

If you get a __ lesion, everything goes DOWN.Paralysis or paresisLoss of muscle toneHyporeflexia or loss of reflexesFascinculation and fibrilationMuscle atrophy

A

LMN

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15
Q

Spasticity is the ultimate result of __ damageIt causes increased tone in leg extensors and arm flexors (decorticate rigidity)It causes increased resistance to ___ movements (varies with speed of movement). If you try to move a spastic limb, it won’t move.It causes increased __ __reflex. You get this thing called a __ ___ reflex and __ (you tap a tendon and the response keeps going). Sothe initial response from tapping the tendonis the stretch reflex. ___ seems to be responding to the stretch reflex

A

Spasticity is the ultimate result of corticospinal tract damageIt causes increased tone in leg extensors and arm flexors (decorticate rigidity)It causes increased resistance to passive movements (varies with speed of movement). If you try to move a spastic limb, it won’t move.It causes increased deep tendon reflex. You get this thing called a clasp knife reflex and clonus (you tap a tendon and the response keeps going). Sothe initial response from tapping the tendonis the stretch reflex. Clonus seems to be responding to the stretch reflex.

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16
Q

Babinski sign reveals __ __ damage. You see it in two conditions: after __ damage and the otherin ___ because it takes them until 18 months for the corticospinal tract to become myelinated. Until it is myelinated it is not working.The normal adult response is ___.. It is a skin reflexthat works to support the body against gravity as a foot touches the ground. CST supresses ____ to non-painful stimuli.Pathological response is ___(dorsiflexion), where the toe fans out.

A

Babinski sign reveals corticospinal tractdamage. You see it in two conditions: after CST damage and the otherin infants under 18 months because it takes18 months for the corticospinal tract to become myelinated. Until it is myelinated, it is not working.The normal adult response is ventroflexion. It is a skin reflexthat works to support the body against gravity as a foot touches the ground. CST supresses dorsiflexion to non-painful stimnuli. Pathological response is extension (dorsiflexion), where the toe fans out.

17
Q

When there is serious damage to the brain, the patient doesnot just lieflaccidly. They lie with different types of postures. One of them is called the __ (__) posture. You see this posture when there is damage in the brain ____the midbrain. The midbrainis intact but thestructures ____the midbrain have been damaged. It causes the___to be flexed and __to be extended.We believe that this posture with the armshas to do with the fact that the ___ ___is still in tact. The __ __ has got thearms flexing and the more caudal reticulo and vestibularspinal tract excite leg extensors so the legs are extended.

A

When there is serious damage to the brain, they do not just lie their flaccidly. They lie with different types of postures. One of them is called the decorticate (flexor)posture. You see this when there is damage in the brain ABOVE the midbrain. The midbrain is intact but the structures above the midbrain have been damaged. It causes thearms to be flexed and legs to be extended.We believe it has to do with the fact that the red nucleus is still intact. The red nucleus has got thearms flexing and the more caudal reticulo and vestibularspinal tract excite leg extensors so the legs are extended.

18
Q

The __ ___ Contributes to the Lateral Descending System.The __ __could direct arm & hand movementsIt could also excites upper limbflexorsIt is visible during decorticate (flexor )rigidity

A

The red nucleusContributes to the Lateral Descending System.The red nucleuscould direct arm & hand movementsIt could also excites upper limbflexorsIt is visible during decorticate (flexor )rigidity

19
Q

Decerebrate (extensor) posturing occurs when there is a lesion __ the midbrain. In this scenario, arms and legs are ___ (in response to painful stimulus). Release of reticulo- and vestibulospinal that excite both upper and lower limb extensors.

A

Decerebrate (extensor) posturing occurs when there is a lesion __ the midbrain. In this scenario, arms and legs are ___ (in response to painful stimulus). Release of reticulo- and vestibulospinal that excite both upper and lower limb extensors.

20
Q

The red nucleus is located in the __ midbrain. The ___ tract originates from here.In decorticate (flexor) posturing, what is the cause of the arms to be in the decortico position?–> Since the lesion is above the midbrain,the __ nucleus is still intact, sothe patient’s arms are bent because the __ __ isresponsible forexcitingthe upper limb flexors.Decerebrate posturing occurs by damage of the __ __. The damage is __ the midbrain. This causes arms to be ___ by the patient’s sides, wrist __ back and pushed against side. The legs are also ___ because the __ __ are still intact (these are responsible for exciting both the upper and lower limb extensors)

A

The red nucleus is located in the rostralmidbrain. The rubrospinal tractoriginates from here. In decorticate (flexor) posturing, what is the cause of the arms to be in the decorticoposition?–> Since the lesion is above the midbrain, the red nucleus is still intact so the patients arms are bent because the red nucleusisresponsible forexcitingthe upper limb flexors.Decerebrate posturing occurs by damage of the red nucleus. The damage is below the midbrain. This causes arms to be extended by the patient’s sides, wrist flexed back and pushed against side.The legs are also extended because the vestibulo and reticulospintal tractsare still intact (these are responsible for exciting both the upper and lower limb extensors).

21
Q

___s of neurons control movements, direction and speed.

A

Populations

22
Q

The __ and __ __ are major inputs to the motor cortex

A

Basal ganglia and cerebellum

23
Q

The motor nuclei of the thalamus are also in the ventral group. The ventral anterior nucleus receives inputs from the __ __ and __ __. It is the relayfrom the __ __. Theventrolateral nucleus hastwo parts.The most rostral part projects to pre-motor supplementory cortex. the morecaudal part projects to primary motor cortex, receiving its input from the cerebellum. The cerebellum has a direct connection to the motor cortex.

A

The motor nuclei of the thalamus are also in the ventral group. The ventral anterior nucleus receives inputs from the substantia niagraand globus pallidus. It is the relayfrom the motor cortex. Theventrolateral nucleus hastwo parts.The most rostral part projects to pre-motor supplementory cortex. The morecaudal part projects to primary motor cortex, receiving its input from the cerebellum. The cerebellum has a direct connection to the motor cortex.

24
Q

Muscles are innervated by alpha motor neurons, and the site where their innervation takes place is called the ____ ___,or the ____ ___ plate. It is a nicotinicreceptor, which is important. There are two kinds of cholinergic receptors: nicotinicand cholinergic. This one is nicotinic.Through this junction, trophic factors are also able to get to the muscle.

A

Muscles are innervated by alpha motor neurons, and the site where their innervation takes place is called the neuromuscular junction, or the motor endplate. It is a nicotinicreceptor, which is important. There are two kinds of cholinergic receptors: nicotinicand cholinergic. This one is nicotinic.Through this junction, trophic factors are also able to get to the muscle.