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Neuroanatmony
n/a
189
Anatomy
Graduate
02/06/2011

Additional Anatomy Flashcards

 


 

Cards

Term
Neural Plate
Definition
The portion of the primative ectoderm that will develop into the brain and spinal cord
Term
Notochord
Definition

A line of cell ventral to the neural plate that will become the site of the vertebral column.

 

Remnants of the notochord are found in the nucleus pulposus of the intervertebral discs.

Term
Neural Crest
Definition

Cells arising from the neural fold during the invagination of the neural plate. As the neural plate becomes the neural tube, these cells will be pushed out to the dorsal sides, essentially surrouding the folding plate.

 

These will mostly form the dorsal roots, containing the sensory nerves.

Term
Neural Groove
Definition
The invagination of the neural plate, edged by the neural fold (which will become the neural crest cells)
Term
Neural Tube
Definition
The complete fusion of the edges of the neural plate, creating a hollow tube, which will become the brain and spinal cord.
Term
Somite
Definition

Mesodermal tissue that is covered by ectoderm that appear as lumps on the dorsal side of the embryo. This shows the segmentation of the nervous system.

 

The mesoderm will develop in muscle, and will carry nerves (motor; ventral) that will relate back to the original developmental position = myotomes


The ectoderm will develop into skin, and will carry nerves (sensory; dorsal) that will relate back to the original delopmental position = dermatomes

.

Term
What side of the developing spinal cord is sensory information normally on?
Definition
Dorsal
Term
What side of the developing spinal cord is motor information normally on?
Definition
Ventral
Term
Dermatome
Definition
Portion of skin innervated by a specific spinal nerves, coming from the dorsal roots of the spinal cord.
Term
Myotomes
Definition
Muscles innervated by specific spinal nerves from the ventral roots of the spinal cord.
Term
Central Canal
Definition
The pin-sized hole in the middle of the adult spinal cord; may be a potential space in some areas.
Term
Spinal Nerve
Definition
The combination of sensory and motor fibers coming from the ventral and dorsal roots. They leave the vertebral column and go out to the body.
Term
Cranial Nerve I
Definition
  • Olfactory
  • Sensory: smell
  • Directly off brain
Term
Cranial Nerve II
Definition
  • Optic
  • Sensory: vision
  • Directly off the brain
Term
Cranial Nerve III
Definition
  • Oculomotor
  • Motor: iris (contracted), levator palpebrae, Eye muscles (except lateral rectus and superior oblique)
  • Off of the midbrain
Term
Cranial Nerve IV
Definition
  • Trochlear
  • Motor: Superior Oblique
  • Off of the midbrain
Term
Cranial Nerve V
Definition
  • Trigeminal
  • Motor: muscles of mastication
  • Sensory: facial sensation
  • Off of the middle pons
Term
Cranial Nerve VI
Definition
  • Abducens
  • Motor: Lateral Rectus
  • Off of the lower pons
Term
Cranial Nerve VII
Definition
  • Facial
  • Motor: facial expression
  • Sensory: taste
  • Off of the lower pons
Term
Cranial Nerve VIII
Definition
  • Vestibulo-cochlear
  • Sensory: head position, acceleration, hearing
  • Off of the lower pons
Term
Cranial Nerve IX
Definition
  • Glossopharyngeal
  • Motor: pharynx
  • Sensory: taste
  • Off of the medulla oblongata
Term
Cranial Nerve X
Definition
  • Vagus
  • Motor & Sensory: Lung, Heart, Gut, Larynx
  • Off of the medulla oblongata
Term
Cranial Nerve XI
Definition
  • Spinal Accessory
  • Motor: Trapezius and SCM
  • Off the medulla oblongata and spinal cord
Term
Cranial Nerve XII
Definition
  • Hypoglossal
  • Motor: Tongue
  • Off the medulla oblongata
Term
Spinal Nerve C4 - Dermatome
Definition
Upper shoulder
Term
Spinal Nerve C5 - Dermatome
Definition
Lateral arm & forearm
Term
Spinal Nerve C6 - Dermatome
Definition
Lateral forearm & thumb
Term
Spinal Nerve C7 - Dermatome
Definition
Middle finger
Term
Spinal Nerve C8 - Dermatome
Definition
Pinky & Ulnar border
Term
Spinal Nerve T1 - Dermatome
Definition
Medial arm
Term
Spinal Nerve T4 - Dermatome
Definition
Nipple line
Term
Spinal Nerve T10 - Dermatome
Definition
Umbilicus
Term
Spinal Nerve L1 - Dermatome
Definition
Anterior thigh, parallel to the inguinal ligament
Term
Spinal Nerve L2 - Dermatome
Definition
Obliquely traversing the mid-anterior thigh
Term
Spinal Nerve L3 - Dermatome
Definition
Distal anterior thigh & knee
Term
Spinal Nerve L4 - Dermatome
Definition
Medial leg & foot
Term
Spinal Nerve L5 - Dermatome
Definition
Lateral leg & dorsum of foot
Term
Spinal Nerve S1 - Dermatome
Definition
Lateral plantar aspect of foot
Term
Spinal Nerve S2 - Dermatome
Definition
Posterior thigh
Term
Spinal Nerve S3-S5 - Dermatome
Definition
Saddle back (anus)
Term
Spinal Nerve C5 - Myotome
Definition
Biceps
Term
Spinal Nerve C6 - Myotome
Definition
Wrist extensors & Brachioradialis
Term
Spinal Nerve C7 - Myotome
Definition
Wrist flexors & Triceps
Term
Spinal Nerve C8 - Myotome
Definition
Hand extrinsics
Term
Spinal Nerve T1 - Myotome
Definition
Hand intrinsics
Term
Spinal Nerve L2 - Myotome
Definition
Iliopsoas
Term
Spinal Nerve L3 - Myotome
Definition
Some quads
Term
Spinal Nerve L4 - Myotome
Definition
Quads & anterior tibialis
Term
Spinal Nerve L5 - Myotome
Definition
Extensor hallucis longus
Term
Spinal Nerve S1 - Myotome
Definition
Plantar flexors & evertors
Term
Free Nerve Endings sense:
Definition
Pain and temperature
Term
Follicular endings sense:
Definition
Light touch
Term
Merkel's Disks sense:
Definition

Vertical pressure (perpendicular to the skin)

 

"Merkel is Vertical"

Term
Messiner's Corpuscles sense:
Definition

  Lateral pressure (parallel to the skin)

 

"M.C. Later(-al)"

Term
Ruffini's Corpuscles sense:
Definition

Deep pressure

 

"Press roughly (deep)"

Term
Pacinian Corpuscles sense:
Definition

Deep vibrations

 

"Pa-pa-pa" vibrations

Term
Neuropraxia
Definition

Transient signal interuption due to axon compression. No axonal degeneration/death.

Best case scenario.

 

Refers to damage in the PNS.

Term
Axonotmesis
Definition

Axon is damaged by an extended pressure injury. The connective tissue is intact.

Has a better chance for regeneration than neurotmesis.

 

Refers to damage in the PNS.

Term
Neurotmesis
Definition

Damage to both the axon and the connective tissue (complete cut/severence). Damage to the CT results in displacement of the severed nerve ends. Most severe situation, less chance for regeneration.

 

Regards to damage in the PNS.

Term
What part of the neuron is most susceptible to injury?
Definition
The axon because it is so long. Cell body damage requires very direct damage, which is less likely to occur.
Term
Anterograde (Wallerian) Degeneration
Definition
Degeneration of the axon distal to the lesion. Will include all of the axon from the lesion to the synapse.
Term
Retrograde Degeneration
Definition
Axonal death proximal to the lesion. Only retracts 1-2 Nodes of Ranvier from the lesion.
Term
What is the 15% Rule?
Definition
If damage to an axon is 15% of the distance from the cell body or less, the cell will die. Therefore, the father away from the cell body the lesion, the greater the chances for survival and regeneration.
Term
What occurs minutes after a is nerve lesion in Anterograde degeneration?
Definition
  • Neurofilaments swell and fragment.
  • There is an increase in mitochondria, in an attempt to repair and clean up
  • The myelin retracts from the axon
Term
What occurs 12 hours after a nerve is lesioned in Anterograde degeneration?
Definition
  • The axon myelin becomes swollen and irregular
Term
What occurs in the early days following a nerve lesion in Anterograde degeneration?
Definition
The myelin becomes ellipsoid and then digested.
Term
What occurs at day 6 post lesion in Anterograde degeneration?
Definition
Schwann cells form a tube, which will (hopefully) allow the nerve to regenerate - if the nerve sprout reaches the tube, it will be guided to the correct place.
Term
How soon post injury can proximal axons sprout?
Definition
6 hours, assuming the cell is alive (15% rule). However, crushing injuries or tears can take up to 1 week to sprout.
Term
Prosencephalon
Definition

The forebrain (the most cephaled).

Develops into the:

  1. Telencephalon
  2. Diencephalon
Term
Telencephalon
Definition

Derived from the prosencephalon. Develops into:

  • Cerebral hemispheres
  • Lobes of the cortex
  • The 2 lateral ventricles
Term
Diencephalon
Definition

A derivative of the prosencephalon. Develops into:

  • The thalamus
  • Hypothalamus
  • 3rd ventricle
Term
Mesencephalon
Definition

The midbrain. Remains the mesencephalon as development continues (doesn't "divide")

Cranial Nerves III & IV will arise from here.

Term
Rhombencephalon
Definition

The "Hindbrain". Divides into:

  1. Metencephalon
  2. Myelencephalon
Term
Metencephalon
Definition

A Rhombencephalon derivative. Develops into:

  • Pons
  • Cerebellum
  • 4th ventricle
Term
Myelencephalon
Definition

A Rhombencephalon derivative. Develops into:

  • Medulla Oblongata
Term
What are the 2 main "points" of learning embryology?
Definition
That the nervous system is segmented and hollow.
Term
Afferents
Definition
Nerves/neurons that carry sensory information to the CNS (Integrating centers)
Term
Efferents
Definition

Nerves/neurons carrying motor information to the PNS (effectors).

 

"Efferents exit the CNS"

Term
Purpose of Gray Matter
Definition
The processing of information. Contains the cell bodies and some glial cells.
Term
Purpose of White Matter
Definition
The long distance traveling of information between the PNS and CNS. Contains (un)myelinated axon tracts.
Term
Bipolar Neuron
Definition

Single axon coming from body, single dendrite coming to the body. "Typical" neuron we draw/examine.

"Discrete" neurons

Term
Unipolar Neuron
Definition

One long process dendrite --> axon with cell body "off" the process. Has central and periphery connections.

Ex: dorsal root ganglion cells: Ganglion holds the cell body, process is in both CNS and PNS.

Term
Multipolar
Definition
The most common nerve type in the nervous system. Has multiple dendritic processes with one axon (which may branch into many synaptic terminals). Common of motor neurons.
Term
Hypoexcitable Neuron
Definition

A neuron whose threshold potential is > -40mV. This means it takes a larger stimulus to reach threshold and trigger an AP.

Clinically, this would present as sluggish behavior, slow deep tendoon reflex, etc.

Term
Hyperexcitable Neuron
Definition
A neuron whose threshold is <-40mV (or whose resting Vm is >-70mV). It takes a smaller stimulus to reach threshold and trigger an AP
Term
Hypokalemia
Definition

A condition in which the [K+] in the ECF drops. This increases the tendency for K+ to leave the cell because the gradient has changed. This then causes the Vm to become more (-), making the cell hypoexcitable. (Remember that K+ influences Vm, while Na+ influences threshold)

 

This is a common in elderly patients using diuretics with BP medicine, as increased urine output "washes" out the ECF K+

Term
What types of cells become brain tumors?
Definition
Accessory elements (glia, etc), not conducting cells.
Term
What receptors are found in joints?
Definition
  • Free nerve endings: pain and temp
  • Pacinian corpuscles: deep vibrations
  • Ruffini's corpuscles: deep pressure

Pacinian and Ruffini corpuscles contribute to our sense of proprioception.

Term
What are golgi tendon organs?
Definition
Sensory receptor organs located at the skeletal muscle - tendon border that sense tendon tension which can be relfective of muscle contraction or passive tension. This contributes to our sense of proprioception.
Term
Muscle Spindles
Definition
Sensory receptors containing intrafusal muscle fibers, and surrounded by extrafusal muscles. They sense changes in muscle length, contributing to proprioception. There are afferent and efferent nerve fibers coming to and exiting the spindle.
Term
Intrafusal Muscle Fiber
Definition

A component of the muscle spindle. Two types:

Bag - dynamic stretch sensor

Chain - static stretch sensor

 

The afferent nerve wraps around this fiber.

Term
Extrafusal Muscle Fiber
Definition
An external component of the muscle spindle. It receives the efferent nerve. These contributes to tension and such.
Term
Basic Tract of a Deep Tendon Reflex
Definition
  1. Tap the tendon
  2. Stretches the spindle
  3. The stretch is sensed by the afferent nerve (Ia fiber)
  4. Afferent sends signal to spinal cord, where it synapses on the motor efferent
  5. Motor efferent (Aα fiber) synapses onto the extrafusal fiber
  6. The muscle contracts
Term
Hypoactive Reflex
Definition

Some of the afferent and/or efferent fibers involved in the DTR circut are damaged, but there are enough to still produce a (weakened) reflex.

 

This can be caused by damage to the nerves directly or a herniated disk that compresses the nerves leaving the spinal cord.

Term
What does the I-IV System classify?
Definition
Sensory peripheral nerve fibers
Term
What does the A-C system classify?
Definition
Both sensory and motor peripheral nerve fibers.
Term
Fiber type: Aα
Definition
  • Large diameter
  • Motor fiber
  • 120 m/sec
Term
Fiber type: Aδ
Definition
  • Small diameter
  • Pain and temperature
  • 15 m/sec
Term
Fiber type: C
Definition
  • Small diameter
  • Unmyelinated
  • Pain and temperature
  • 2 m/sec
Term
Fiber type: Ia
Definition
  • Large diameter
  • Spindle afferents
  • 120 m/sec
Term
Fiber type: III
Definition
  • Small diameter
  • Pain and temperature
  • 15 m/sec
Term
Fiber type: IV
Definition
  • Small diameter
  • Unmyelinated
  • Pain and temperature
  • 2 m/sec
Term
Symptom(s) of a CN I Lesion
Definition
Loss of smell
Term
Symptom(s) of a CN II Lesion
Definition
Blindness
Term
Symptom(s) of a CN III Lesion
Definition
  • Droopy or closed eyelid
  • Lose ability to move eye: down, in, up
  • Lose iris control: fixed and dilated (relaxed)
  • Resting position of eye: lateral
Term
Symptom(s) of a CN IV Lesion
Definition
Affects the superior oblique, but it's difficult to determine because the other eye muscles compensate
Term
Symptom(s) of a CN V Lesion
Definition
  • Depending on where the lesion is, lose 1/3 to all of facial sensation
  • Loss of chewing
Term
Symptom(s) of a CN VI Lesion
Definition
  • Loss of lateral eye movement
  • Resting eye postion - medial
Term
Symptom(s) of a CN VII Lesion
Definition
  • Loss of facial expression: Bell's Palsy
  • Some taste loss
Term
Symptom(s) of a CN VIII Lesion
Definition
  • Hearing loss
  • Balance loss
Term
Symptom(s) of a CN IX Lesion
Definition
  • Loss of pharynx control
  • Changes in blood pressure and breathing
  • Difficulty swallowing
Term
Symptom(s) of a CN X Lesion
Definition
  • Motor loss: Pharynx and larynx, swallowing, speech, heart, gut, lungs
  • Increased heart rate
Term
Symptom(s) of a CN XI Lesion
Definition
  • Motor: trapezius and SCM
  • symptoms are easier to see with lesions to the spinal part of the nerve
Term
Symptom(s) of a CN XII Lesion
Definition
  • Tongue control
    • Easy to test - have patient stick out tongue. The tongue will deviate to the side of the affected lesion (ie: A right sided lesion - tongue deviates to the right)
Term
How can you test if a muscle problem in the arm is SN related?
Definition
Do a DTR. Compare the biceps (C5), triceps (C7), and/ore brachioradialis (C6)
Term
What DTR could you use to test SN L4 compression?
Definition
Knee Jerk because L4 innervates the quads and anterior tibialis
Term
What are the Basal Ganglia?
Definition
  1. Caudate Nucleus
  2. Globis Pallidus
  3. Putamen

These are involved in motor activity

Term
What landmarks tells you that you're viewing the posterior limb of the internal capsule in a coronal section?
Definition
The 3rd Ventricle and Thalamus (which surrounds the 3rd ventricle)
Term
What nuclei is the most common area of stroke?
Definition
The Internal Capsule
Term
What makes the Posterior Limb of the Internal Capsule so important?
Definition

It is the place where all sensory and motor tracts pass through from the spinal cord and brain.

Fibers run ventral-dorsal (down-up); as they move up into the cortex, the fibers fan out (corona radiata) to their appropriate destinations.

Term
How can you determine the anterior and posterior ends of a horizontal brain slice?
Definition
The posterior horns of the Lateral Ventricles are father apart than the anterior horns.
Term
In the "pie" of the basal ganglia, what is the filling?
Definition
Globis Pallidus
Term
In the "pie" of the basal ganglia, what is the crust?
Definition
Putamen
Term
How do you recognize a horizontal section of the rostral midbrain?
Definition

You can see the the cerebral aqueduct and superior colliculi.

 

Note that in the stained picture, the substantia nigra stains white.

Term
What is the crus?
Definition
In the most anterior portion of the rostral midbrain, it is an area that carries motor info from the internal capsule. It is lateral to the substantia nigra.
Term
What 2 structures make the cerebral peduncle?
Definition
The crus and substantia nigra. It is the anterior "lobe" of the rostal midbrain section.
Term
[image]
Definition
Caudal medulla
Term
[image]
Definition
Coronal section
Term
[image]
Definition
Lower midbrain
Term
[image]
Definition
Mid pons
Term
[image]
Definition
Rostral medulla
Term
[image]
Definition
Rostral midbrain
Term
Landmarks of the Rostral Midbrain Section
Definition

A. Superior colliculus
B. Periaqueductal gray

C. Thalamus
D. Red nucleus (just lateral to CN III)

E. CN III

F. Cerebral aqueduct

G. Substantia Nigra

HIJ. Crus

 

 

        [image]

Term
Landmarks of Lower Midbrain Section
Definition

A. Periaqueductal gray

B. Inferior Colliculus -> resembles tennis racket

E. Substantia Nigra

I. Cerebral Aqueduct

 

        [image]

Term
Landmarks of the Mid Pons Section
Definition

A. Cerebellum

B. Cerebral aqueduct --> 4th Ventricl

C. CN V

G. Pontocerebellar fibers

 

        [image]

 

Term
Landmarks of the Rostral Medulla
Definition

B. 4th Ventricle -> key to determining the slice

E. Olives - appear squiggly when stained

F. CN XII - hypoglossal

G. CN IX - glossopharyngeal

G. CN X - vagus

H. Pyramids - corticospinal tract

 

          [image]

Term
Caudal Medulla - Key Points
Definition
  • Sensory decussation
  • Motor decussation (below sensory)
  • Can't see the 4th ventricle
  • Start to notice transition into the spinal cord
Term
Reticular Formation
Definition
  • Short pools of nuclei
  • Receives multiple sensory inputs
  • Contains the Ascending Reticular Activating System (ARAS)
    • Contributes to the awake state and sense of awareness
  • Suppresses Sensory information, namely pain
  • Vital integrating centers
    • Cardiovascular, BP, HR, respiration, vomiting, walking, swallowing
Term
What is the overall shape of the spinal cord and why?
Definition

It is hour glass shaped, with the cervial and lumbosacral regions being larger than the thoracic.

 

This is because the larger areas innervate much more than the thoracic:

C = upper extremity

LS = lower extremite

T= chest

Term
Why is there more white matter in the cervical region of the spinal cord than the lower regions?
Definition
As you ascend the cord, it "collects" more information. Remember that white matter is the conduit for signals. So at the top of the spinal cord you have tracts for the entire body, while at lower levels you only have tracts from the "stuff" below that level, not the stuff above.
Term
Why is there more gray matter in the cervical and lumbosacral regions of the spinal cord?
Definition
Those areas lead to the major plexi, innervating the limbs.
Term
What is contained within the gray matter of the spinal cord?
Definition

Gray matter is the area of processing and modulation. It includes:

  • internuncial neurons = the modulators
  • motor neurons
  • autonomic neurons
  • tract cells - ascending, sensory cell bodies
Term
What is the old classification system for the gray matter of the SC?
Definition

3 horns, which contain specific nuclei:

  • Dorsal horn
  • Lateral horn
  • Ventral horn

 

Term
What nuclei are found in the dorsal horn?
Definition
  1. Substantia gelatinosa = pain suppression
  2. Nucleus propius = pain
Term
What nuclei are found in the lateral horn?
Definition
  1. IMM (intermediomedial) cell column
  2. IML (intermediolateral) cell column

Both have autonomic functions.

The lateral horn is most prominant in the thoracic region

Term
What nuclei are found in the ventral horn?
Definition
  1. Medial and Lateral motor nuclei - cell bodies and dendrites for Aα LMNs
  2. Special nuclei: phrenic and spinal accessory
Term
What is the new classification system for the spinal cord?
Definition
The Lamina of Rexed, which divides the gray matter into 10 lamina
Term
Which lamina(s) represent pain and temperature? Which "horn" do they belong to?
Definition

Lamina I, III, IV, and V

 

They are found in the dorsal horn.

Term
Which lamina is the Substantia Gelatinosa?
Definition
Lamina II. It is invovled in pain suppression. It is found in the dorsal horn.
Term
Which lamina is represents deep sensory information?
Definition
Lamina VI, which is part of the dorsal horn.
Term
Which lamina is involved in the ANS and contains the Nucleus dorsalis (proprioception)?
Definition
Lamina VII, located in the lateral horn.
Term
Which lamina is involved in motor information?
Definition

Lamina IX. It contains the cell bodies of Aα LMNs

This is the most important lamina, and is located in the ventral horn.

Term
In which lamina do the tracts cross to the contralateral side?
Definition
Lamina X, which is located centrally, surrounding the central canal.
Term
What is the white matter of the SC divided into?
Definition

Columns or nuclei:

Dorsal

Lateral

Ventral

Term
What information does the Dorsal Column (posterior funiculus) of the white matter of the SC carry?
Definition
Tactile sensibility (touch, pressure, proprioception), not pain and temperature
Term
What information does the Lateral Column (lateral funiculus) of the white matter of the SC carry?
Definition
Major motor pathways and pain and temperature
Term
What information does the Ventral Column (Ventral funiculus) of the white matter of SC carry?
Definition
Minor role in motor and pain and temperature, but the lateral column is more important.
Term
What do the descending tracts of the white matter carry?
Definition
  • Movement
  • Muscle tone
  • Visceral functioning
  • Sensory editing (ex: pain suppression)
Term
What do the ascending tracts of the white matter carry?
Definition
  • Touch
  • Pressure
  • Pain
  • Temperature
  • Proprioception
Term
Which lamina receives descending information?
Definition
Lamina VIII
Term
What tracts are found in the Dorsal column (Posterior funiculus)?
Definition
  • Fasiculus gracilis (most medial tract) = lower limb, sensory
  • Fasiculus cuneatus (lateral to FG) = upper limb, sensory

[image]

Term
What tracts are found in the lateral column (faniculus)?
Definition
  • Lateral corticospinal
  • Spinothalamic (lateral)

[image]

Term
What does the corticospinal tract carry?
Definition
Dscending motor fiber to all muscles of the body, especially those that control fine motor movement.
Term
What does the spinothalamic (lateral) tract carry?
Definition
Ascending pathways carrying sensory information, such as pain, temperature, touch, etc.
Term
What tracts does the Ventral column (funiculus) carry?
Definition
  • Ventral (medial) corticospinal - minor to the lateral
  • Spinothalamic (ventral/anterior)
Term
How do you recognize a cervical section of the SC?
Definition

It has big "wings" of gray matter. You can also see both the Fasiculus gracilis (N) and fasiculus cuneatus (O). (this is the only place you will see both, since FC carries sensory information from the upper limb)

 

[image]

Term
What's a key feature of a thoracic SC section?
Definition

The lateral horns are most prominant here, since the ANS information is primarily visceral organs, located in the thoracic region.

Additionally, there will be very little gray matter; mostly white matter

 

[image]

 

Term
How can you recognize a lumbar SC section?
Definition

There is a more prominant butterfly gray, and you can see FG. There is still a fair amount of white matter.

 

[image]

Term
How can you recognize a sacral SC section?
Definition

There is a larger amount of gray matter than white matter. This is because there is only tracts from the lower limbs, fewer ascending and descending tracts are need.

 

[image]

Term
What can you see in a cauda equina slice?
Definition

Multiple nerve roots

 

[image]

Term
How can you distinguish between the dorsal and ventral sides of the spinal cord?
Definition
The dorsal horns are small than the ventral horns.
Term
What is the maximum amout of regeneration that can occur? What time of damage is most likely to achieve this amount?
Definition
At best, 80% of function can be gained back. This is reached with axonotmesis, since th CT is still intact. Neurotmesis will be <80% due to the damage to CT
Term
What is the growth rate for nerve regeneration?
Definition
1-2 mm/day
Term
What happens to the growth sprouts when one of them finds the tube?
Definition
They die off
Term
What a complications with regeneration?
Definition
  • Scar tissue can make it difficult for sprouts to find and/or reach the tube.
  • The wrong type of nerve sprout may end up in the wrong tube, thereby making that a non-functional regeneration (ie: A sensory nerve sprout finds a motor tube)
  • The size of the gap. More than a few mm will hinder regeneration
Term
What are the 2 other PNS recovery mechanisms (other than regeneration)?
Definition
  1. Reinstatement of blood flow (only in neuropraxia, where there is only compression, no lesion of the neuron or CT)
  2. Recovery of Synaptic Effectiveness (also only in neuropraxia)
Term
What is the time frame for reinstatement of blood flow in the PNS?
Definition
1-2 minutes. It is a short and quick recovery mechanism - relieve the pressure and blood returns to the region, allowing sensation to return.
Term
Explain Recovery of synaptic effectiveness in the PNS? What is the time frame?
Definition
This occurs when there is edema that is compressing a non-lesioned nerve, thereby inhibiting its action. As the edema is reduced, the functioning of this nerve is restored, since the problem was only compression. This can take days or weeks to occur, depending on the severity of the injury/inflammation.
Term
What is the major difference between recovery in the PNS and the CNS?
Definition
There is no regeneration in the CNS.
Term
How do we analyze the type of injury that occurs in Acute Nerve Compression?
Definition
It is not always obvious at first, so we use the time frame of recovery to determine if the injury was neuropraxia, axonotmesis, or neurotmesis
Term
Explain Neural (spinal) Shock
Definition

Widespread CNS inhibition that occurs when there is an injury. There is no cell death, so it's analogous to neuropraxia. It seems that the CNS just "shuts down" these intact neurons.

Ex: concussion (contact injury); TIA (24 hrs post = complete recovery)

 

The cause of the inhibition is unclear. It may be: The hypothalamus, or the adjacent areas to the lesions, or changes in blood flow.

Term
Recovery of Synaptic Effectiveness in the CNS
Definition
Same as in the PNS. Local edema compresses intact nerves. As the edema reduces, those intact neurons recover their synaptic effectiveness.
Term
Explain collateral sprouting in the CNS.
Definition
This is a recovery mechanism in which intact neurons surrounding a lesion grow new axons to synpase on other intact neurons that had lost their connection with the lesioned neuron. This is not nerve regeneration. Rather, it's a form of reorganization, in which bypasses are created around the lesioned neurons.
Term
Explain vicarious function in the CNS
Definition
This is cortical reorganization, in which pathways change function in an attempt to help regain some of the function lost by a lesion.
Term
Explain Recovery of Silent Synapses in the CNS
Definition

A recovery mechanism in which a lesion "awakens" neurons in a silent pathway. There are neurons in the brain that are silent, or "asleep". When a lesion occurs, it activates these neurons to help with regaining some function.

 

This also plays an important role in learning and memory. (Long term potentiation)

Term
Explain the effects of rehab on plasticity in the CNS
Definition
Repeated use of limbs affected by a lesion can show significant recovery of function.
Term
What are the time frames for CNS recovery?
Definition
  • Most will occur within the first 6 months post-injury (if they recover at all - some injuries or diseases have a downhill progression)
  • There can be some recovery 6-12 months later
  • And very little occurs after a year (although current research is starting to show this is not necessarily true)
Term
Why is there no regeneration in the CNS?
Definition

It is not fully understood, but some theories include:

  • Antigrowth factors produced by oligodendrocytes (Nogo), which are not produced by Schwann cells in the PNS
  • A difference between the myelin and/or neural growth factors produced by Schwann cells and Oligodendrocytes
  • Abscent growth factors in the CNS
  • Immune response
  • Too much scarring
Term
What is behavioral substitution?
Definition
This a recovery mechanism in which the patient learns how to compensate for loss of function. This is not neural plasticity. Rather, it's using intact pathways to make up for the lost ones. It can be seen in both CNS and PNS recovery, and it can be used in both motor and sensory damage.
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