Anatomy Neuroanatomy pt 2

Anything from the shoulders down

There is a lesion in the right medullary pyramid, what part/region of body will be affected?

White matter tracts of the sensory pathway

What do the blue regions represent?

White matter tracts of the motor pathway

What does the pink/orange regions represent?

3 neuron chain

Sensory information follows a pathway that involves how many neurons?

Periphery (outer parts of the body)

Where does the sensory tract begin?

Ascends the spinal column/brainstem

Signal ends in the CNS

How does the sensory tract travel through the spinal column/brainstem? Where does the signal end?

Two(ish) neuron chain

Motor information follows a pathway that involves how many neurons?

Descends the brainstem/spinal column

How does the motor tract travel through the spinal column/brainstem?

Begins in CNS and ends in the periphery

Where does the motor tract start and where does it end?

Interneuron - activity mediates interactions between sensory & motor systems, local circuit (reflex pathways)

What is the starred structure? What does it do?

Posterior/dorsal, just sensory pathways

What is the name of column #1? What pathways does this column have?

Lateral, sensory and motor pathways

What is the name of column #2? What pathways does this column have?

Anterior/ventral, sensory and motor pathways

What is the name of column #3? What pathways does this column have?

1. Dorsal column lemniscus

2. Anterolateral system

What are the two sensory pathways?

Dorsal column lemniscus

What is 1 pointing to?

Anterolateral system

What is 2 pointing to?

Discriminative (fine) touch, pressure and vibration

What is the function of the dorsal column lemniscus?

Crude (diffuse) touch, pain and temperature

What is the function of the anterolateral system?

1. Corticospinal tract

2. Corticobulbar tract

What are the two motor pathways?

Motor to trunk and limbs

What is the function of the corticospinal tract?

Spinal cord (ventral horns)

Where are the LMN of the corticospinal tract?

Motor to head and neck

What is the function of the corticobulbar tract?

In the DRG, and the peripheral/central neurons extend from it

Where is the 1st order neuron of the Dorsal Column Lemniscus of the limbs/trunk located?

Cerebral cortex

Where are all of the upper motor neurons?

Thalamus (always) in VPL

Where is the 3rd order neuron of the Dorsal Column Lemniscus of the limbs/trunk located?

nuclie

A _______ is a collection of cell bodies

tracts

Axons coming off the cell bodies are going to be going into _______

Most inferior aspect of the medulla

What is the caudal medulla?

Pre central gyrus

Where is the primary motor cortex?

Gracile/Cuneate tract

What is the ascending part of the central axon of the 1st order neuron called?

Gracile tract is more medial, cuneate tract is more lateral

Is the gracile or cuneate tract more medial?

Lumbar spinal cord

Gracile tract

Where do neurons coming from the lower limbs enter the Dorsal Column Lemniscus? Is this the gracile or tract?

Cervical spinal cord

Cuneate tract

Where do neurons coming from the upper limbs enter the Dorsal Column Lemniscus? Is this the gracile or cuneate tract?

In the gracile/cuneate nuclei within the caudal medulla (dorsal column nuclei)

Where does the 2 order neuron of the Dorsal Column Lemniscus of the limbs/trunk sit?

In the caudal medulla

Where does the 2 order neuron of the Dorsal Column Lemniscus of the limbs/trunk decussate?

2nd order neuron

In the sensory pathway, what neuron always decussates?

Medial lemniscus tract

After decussating, the 2nd order axon of the Dorsal Column Lemniscus of the limbs/trunk ascends in the _________.

Ventral posterior lateral nucleus (VPL) of the thalamus

What does the 3 order neuron of the Dorsal Column Lemniscus of the limbs/trunk sit in?

3o axon (at VPL) → internal capsule →corona radiate → post-central gyrus

What is the pathway of the 3 order neuron of the Dorsal Column Lemniscus of the limbs/trunk?

Paracentral lobule

Where does the gracile tract synapse in the motor cortex?

Superior lateral aspect of the post central gyrus

Where does the cuneate tract synapse in the motor cortex?

Gracile

Which tract of the Dorsal Column Lemniscus of the limbs/trunk is located at 1?

Cuneate

Which tract of the Dorsal Column Lemniscus of the limbs/trunk is located at 2?

trigeminal ganglion

Where is the 1st order neuron of the Dorsal Column Lemniscus of the face (trigeminal nerve) located?

Principal sensory nucleus in the pons

Where is the 2nd order neuron of the Dorsal Column Lemniscus of the face (trigeminal nerve) located?

2nd order neuron

Trigeminal Lemniscus

Medial Lemniscus

Which neuron of the Dorsal Column Lemniscus of the face (trigeminal nerve) crosses over to the contralateral side? Once the cross over happens, what is this new tract called? What was the tract prior to cross over called?

Ventral posterior medial (VPM) nucleus of the thalamus

Where is the 3rd order neuron of the Dorsal Column Lemniscus of the face (trigeminal nerve) located?

1st order neuron (ophthalmic division of the trigeminal nerve)

Your patient is feeling loss of all sensation all over the cornea and conjunctiva, what neuron is affected?

Dorsal column meniscus pathway (anywhere 2° neuron)

Patient is feeling loss of discriminative sensation (but feels pain and temperature) over all of right face. If this was a lesion, where would it be?

DRG - central axon enters spinal cord

Where is the 1st order neuron of the Anterolateral Pathway of the limbs/trunk located? What part of the 1st order neuron enters the spinal cord?

In the dorsal horn

Where is the 2nd order neuron of the Anterolateral Pathway of the limbs/trunk located?

Lower limbs: lumbar region

Upper limbs: cervical region

Where do neurons coming from the lower limbs enter the Anterolateral Pathway? Upper limbs?

Spinothalamic tract

What is the tract the 2nd order neuron of the Anterolateral Pathway of the limbs/trunkascends after it duccasates?

Ventral posterior lateral nucleus (VPL) of the thalamus

Where is the 3rd order neuron of the Anterolateral Pathway of the limbs/trunk located?

No

3o axon → internal capsule →corona radiate → post-central gyrus

Is the pathway of the 3 order neuron of the Anterolateral Pathway different that the Dorsal Column Lemniscus?

Trigeminal ganglion

Where is the 1st order neuron of the Anterolateral Pathway of the face located?

Spinal nucleus in the pons

Where is the 2nd order neuron of the Anterolateral Pathway of the face located?

Trigeminothalamic tract

What is the tract the 2nd order neuron of the Anterolateral Pathway of the face ascends after it decussates?

Ventral posterior medial nucleus of the thalamus

Where is the 3rd order neuron of the Anterolateral Pathway of the face located?

Upper motor neuron (UMN): pre-central gyrus

Lower motor neuron (LMN): ventral horn of the spinal cord/brainstem

What are the 2 neurons in the motor pathway and where are they located?

Begins in primary motor cortex (pre-central gyrus) as UMN

Where does the corticospinal motor pathway begin and as what?

Voluntary, discrete and skilled movements

Corticospinal pathway controls what kind of movement?

Brainstem

Where are the LMN of the corticobulbar tract?

Brainstem

UMN axons of the corticospinal pathway descend and most decussate in the _________.

ventral horn

UMN of the corticospinal pathway synapse with LMN in the _______

peripheral nerve

LMN of the corticospinal pathway sends axon out through _______ to body/limbs

Lateral corticospinal tract, goes to the limbs

90% of corticospinal axons descend on what tract? Where does this tract go?

Ventral corticospinal tract, goes to the trunk

10% of corticospinal axons descend on what tract? Where does this tract go?

Caudal medulla

Where does the decussation of the UMN of the corticospinal pathway occur?

pre-central gyrus→ corona radiata → internal capsule → cerebral peduncle→ pons → medulla → enters pyramids→ pyramidal decussation incaudal medulla

What is the pathway of the UMN of the corticospinal pathway from the pre-central gyrus to the point of decussation?

Lateral corticospinal tract

What tract does the UMN of the corticospinal pathway travel down after decussation?

Sends axon out of anterior root of ventral horn to skeletal muscle

What is the path of the LMN of the corticospinal pathway?

Ipsilateral; ventral corticospinal tract

10% of the neurons of the corticospinal pathway continue into spinal cord on ______ side. What is this tract called?

Ventral horn of where they are leaving

Where do the neurons travelling down the ventral corticospinal tract deccusate?

Discrete motor innervation

There is a lesion in the right medullary pyramid, what type of innervation is lost?

Left side

There is a lesion in the right medullary pyramid, what side of the body will lose function?

Used to test integrity of nerve pathway (sensory and motor)

- Absence indicates damage to 1o neuron function, inter neuron connection, or LMN

- Part of mechanoreception

What is the purpose of the myotactic reflex?

Send out trophic signals that keep muscles healthy, create tone, and maintain size

Besides contraction, what else do LMN do?

1. Affects a smaller group of muscles

2. Knocks out trophic signal and impulse to contract muscles,

3. Flaccid, atrophy and hypotonic (no tone))

4. Hyporeflexia

What does LMN lesion do?

1. Impact a larger area

2. Hypereflexia/spasticity of LMN

3. Hypertonia/ minimal atrophy

4. Loss of skilled movement

What does UMN lesion do?

Begins in primary motor cortex (pre-central gyrus) as UMN

Where does the 1st order neuron of the corticobulbar pathway start?

Most UMN send axons bilaterally

Exceptions: facial, hypoglossal

How do UMN of the corticobulbar pathway send axons? What are the exceptions?

Synapses in brainstem with LMN related to cranial nerves (cranial nerve nuclei)

Where do the UMN of the corticobulbar pathway synapse and with what?

UMN send axons bilaterally because cranial muscles are important for basic function

Why do UMN of the corticobulbar pathway send bilateral axons?

Lower face mm. receive contralateral only. (B,M,C)

What is the facial nerve exception of the corticobulbar tract?

Genioglossus m. receives contralateral only.

What is the hypoglossal nerve exception of the corticobulbar tract?

LMN: ipsilateral side

UMN: contralateral side

Lesion on the lower motor neuron body would affect what side of the body? Lesion on the upper motor neuron?

Lateral corticospinal tract

What tract is A?

Vestibulospinal tract - adjustments to posture and head movement (think about standing on a moving bus)

What tract is B? What is the function?

Reticulospinal tract - adjustments to posture that anticipate instability (think about getting ready to jump)

What tract is C? What is the function?

Tectospinal tract - reflexive head movement to orient visual stimuli (think about hearing your name in a crowded room)

What tract is D? What is the function?

Ventral corticospinal tract

What tract is E?

Control axial muscles

Posture, balance and coarse control of axial and proximal muscles

"Other" Descending Motor Pathways control what?

In brainstem → axons terminate with lower motor/ interneurons

Where do the nuclei of the "Other" Descending Motor Pathways sit? Where do axons terminate?

"Reticular system" of the cerebellum.

"Other" Descending Motor Pathways are separate from what system?

1. Caudate nucleus

2. Putamen

3. Nucleus accumbens

4. Globus pallidus

What are the 4 components to the basal ganglia?

1. Caudate nucleus

2. Putamen

3. Nucleus accumbens

What parts of the basal ganglia make up the striatum?

Movement of mind or thought

What is the function of the Caudate nucleus?

Body movement

What is the function of the Putamen?

Movement of emotion, motivated behavior

What is the function of the Nucleus accumbens?