Hnfns Exam 21Jan2008

Front 1

What are three types of neuronal reactions to axonal injury?

Back 1

-Anterograde reaction
-Retrograde reaction
-Transneuronal reaction

Front 2

Wallerian degeneration is _______ degeneration.

Back 2

Anterograde degeneration.

Front 3

After axonal degradation, what clears the debris in a PNS injury? In a CNS injury?

Back 3

-Schwann cells and macrophages
-Microglia, astrocytes, macrophages

Front 4

What induces the first wave of Schwann cell proliferation after axonal damage?

Back 4

Macrophages in the distal stump.

Front 5

What phagocytosis cells are in the CNS for phagocytosis of axonal debris? In the PNS?

Back 5

-Microglia, astrocytes, macrophages
-Schwann cells, macrophages

Front 6

What are three factors that determine regeneration of PNS?

Back 6

-Crush vs transection
-Site (closer to target site better)
-Age (younger is better)

Front 7

What are four factors that inhibit CNS regeneration?

Back 7

-Loss of axonal growth promoting factors (eg laminin and fibronectic)
-Molecules that inhibit axonal growth (eg inhibitory glycoproteins from oligodendroglia and cytokines from macroglia and macrophages)
-Formation of a glial scar (impedes growth of axons due to proteoglycan production that inhibits sprouting)
-Oligodendrocytes do NOT form guidance tunnels

Front 8

Multiple methods (peripheral nerve grafts, growth factors, transplantation of cell types, etc) have been tried to improve CNS regeneration. What is the best method?

Back 8

-Conbination of internventions (eg transplants plus growth factors)

Front 9

What two stains stain degenerating axons and degenerating axon terminals?

Back 9

-Silver stains
-Nauta-Gygax

Front 10

What two stains stain degenerating myelin sheaths?

Back 10

-Osmic Acid Stain
-Marchi

Front 11

What three stains stain normal myelin but do NOT stain degenerating myelin sheaths?

Back 11

-Iron hematoxylin
-Weil
-Weigert

Front 12

What are the 3 retrograde reactions in axonal damage?

Back 12

-Proximal portion of axon degenerates similar to the distal portion but only back to the nearest Node of Ranvier
-Dendrite retraction
-Cell body reaction

Front 13

Where are transmitter related molecules synthesized?

Back 13

Nissl substance

Front 14

What is described:
"Parallel lamellae of RER which is comprised of SER with ribosomes attached to the external serugace and free polyribosomes between lamellae"

Back 14

Nissl

Front 15

How is Nissl substance different between motor neurons and sensory neurons?

Back 15

Motor neurons have more Nissl substance (but NOT at the axon hillock)

Front 16

What are the 3 cell body changes after axonal damage?

Back 16

-Eccentric nucleus
-Cell swelling
-Chromatolysis - dispersion of Nissl into fine, fuzzy particles)

Front 17

What does Cresyl Violet stain for?

Back 17

Nissl substance

Front 18

How would you determine the site of origin of damaged fibers?

Back 18

Use a cresyl violet stain (for Nissle substance) to locate the region with cell body reaction (eccentric nucleus, swelling, chromatolysis)

Front 19

What is a transneuronal reaction?

Back 19

-If there is damage to axons that provide the majority of input to a neuron, changes may appear in the next neuron in the line.
-Rare, best example is a lesion of the retina causing transneuronal degeneration of cells in lateral geniculate body.

Front 20

Is the corticospinal tract ascending or descending?

Back 20

Descending

Front 21

Is the spinothalamic tract ascending or descending?

Back 21

Ascending

Front 22

Which way does axonal transport occur- anterograde or retrograde?

Back 22

Both!
-Proteins are manufactured by Nissl bodies and then transported in an anterograde direction.

Front 23

Which way is HRP (horseradish peroxidase) transported?

Back 23

-Retrogradely (pinocytosed by axon terminals)
-Anterogradely

Front 24

Which way is tritiated amino acids transported?

Back 24

-Anterogradely. It is taken up by the cell body and incorporated into protein to be transported down axon.

Front 25

Describe how metabolic mapping can be utilized to study fiber tracts.

Back 25

-More active neurons use more glucose so 2-deoxy-D-glucose can be used as a tracer.

Front 26

What do basophilic stains (such as Cresyl Violet and Toluidine Blue) stain?

Back 26

-Neuron cell bodies (nucleus, nucleolus, Nissl)
-Proximal dendrites
-Neuroglial cells
-Ependymal cells (secrete CSF in CNS)
-Endothelial cells of blood vessels

Front 27

What are the 3 types of neurons? Where are they found?

Back 27

-Pseudounipolar --> DRG and sensory ganglia of CN VII, CN IX, CN X in PNS and mesencephalic nucleus of CN V in CNS.
-Bipolar neurons --> cochlear ganglia, vestibular ganglia, ganglion cells of retina and olfactory neuurons
-Multipolar neuron --> many sensory/motor neurons in CNS and autonomic ganglia in PNS

Front 28

Are motor neurons found in the dorsal or ventral root of the spinal cord?

Back 28

Ventral (efferent)

Front 29

Is the ventral horn sensory or motor?

Back 29

Motor

Front 30

Is the dorsal horn sensory or motor?

Back 30

Sensory

Front 31

Is there more Nissl substance in a motor neuron or a sensory neuron?

Back 31

Motor neuron has large clumps. (Sensory neurons have fine, dust-like particles).

Front 32

Are sensory neurons found in the dorsal horn or the ventral horn?

Back 32

Dorsal horn

Front 33

Which glial cells have light staining nuclei with beads of chromatin adherent to inner surface of nuclear membrane?

Back 33

Astrocytes

Front 34

Which glial cells have spherical nuclei with densely staining nucleoplasm?

Back 34

Oligodendroglia

Front 35

Which glial cells are spindle shaped?

Back 35

Microglial cells

Front 36

In a golgi stain, cellular details cannot be delineated. Can you see the axon?

Back 36

Only the proximal part. Appears as a smooth, unbranched process. Dendrites are easily seen.

Front 37

Besides neurons, what else stains with a Golgi stain?

Back 37

-Blood vessels
-Astrocytes

Front 38

Of the following myelin sheath stains, does NOT stain normal myelin and leaves a pale-gold background instead?
Luxol Fast Blue, Marchi, Weil, Weigert

Back 38

Marchi

Front 39

In the CNS, how many presynaptic inputs are required to bring a neuron to threshold?

Back 39

More than one! Single EPSP's are generally below threshold and will NOT independently generate an action potential.

Front 40

Are there EPSP's and IPSP's in the CNS? At neuromuscular junctions?

Back 40

-Yes
-No, only EPSP's at NM junctions.

Front 41

What are two factors that determine the amplitude of the graded synaptic potential?

Back 41

-Amount of neurotransmitter released.
-Density of receptors on post-synaptic membrane

Front 42

Do graded synaptic potentials in the CNS spread actively or passively?

Back 42

Passive, decay with time and distance.

Front 43

How is spatial summation different from temporal summation of EPSP's?

Back 43

Temporal summation- consecutive EPSP's at the same site add together
Spatial summation- simultaneous EPSP's at different synapses (same neuron)

Front 44

This region has a high density of voltage-gated sodium channels to make it the trigger zone. It is also where graded postsynaptic potentials are summed together...

Back 44

The axon hillock.

Front 45

What is being described:
"causes amplitude of PSP to decay faster"

Back 45

Internal resistance- opposition to charge flow within the cell

Front 46

What is being described:
"causes depolarization to last longer"

Back 46

Capacitance- stores charge across membrane

Front 47

Both time constant (T) and length constant (λ) are related to how easy it is to sum EPSP's to reach threshold. Is higher or lower better?

Back 47

Both higher is better for generating an action potential.

Front 48

This is an example of what:
"One presynaptic neuron synapses on multiple postsynaptic neurons"

Back 48

Divergence.
An example is the sensory signal from touching a hot stove- withdraws limb and notifies CNS.

Front 49

This is an example of what:
"Multiple axon terminals (from one or more neurons) synapse on same post-synaptic cell"

Back 49

Convergence
Can help with spatial summation.

Front 50

What does an axoaxonic synapse do?

Back 50

Modulates the entry of calcium into the postsynaptic axon terminal, causing a change in the amount of neurotransmitter released.

Front 51

There are two types of feedforward processes, excitatory and inhibitory. Briefly describe them.

Back 51

-Neuron A excites-->Neuron B excites-->Neuron C
-Neuron A excites-->Neuron B inhibits-->Neuron C

Front 52

What is lateral inhibition?

Back 52

Activation of one feedforward neuron leads to inhibition of adjacent feedforward neurons.

Front 53

Name 2 ways to "improve" two-point discrimination.

Back 53

-Decrease the receptive field
-Use lateral inhibition

Front 54

What is being described:
"Axons of excitatory neurons give off collaterals to inhibitory interneurons that, in turn, project back to original excitatory neurons, inhibiting them"

Back 54

Recurrent inhibition

Front 55

What is being described:
"Neuron A excites-->Neuron B inhibits-->Neuron C inhibits-->Neuron D

Back 55

Disinhibition, similar to a "doublle negative" by inhibiting an inhibitory neuron.

Front 56

Where do large (Group Ia and Ib) and intermediate (Group I and II) fibers enter the spinal cord (ascending tracts)?

Back 56

Medial to the Zone of Lissauer

Front 57

What do large fibers (Group Ia and Ib) convey in terms of sensory information (ascending tracts)?

Back 57

Unconscious proprioception

Front 58

What do intermediate fibers(Group I and II) convey in terms of sensory information?

Back 58

-Vibration
-Tactile discrimination
-Kinesthetic sense

Front 59

Where do small, thinly myelinated and small, unmyelinated fibers enter the spinal cord?

Back 59

Zone of Lissauer

Front 60

What do small, thinly myelinated fibers convey in terms of sensory information?

Back 60

-Light touch
-Fast pain (sharp)
-Thermal sense (both small, unmyelinated and small, myelinated fibers)

Front 61

What do small, unmyelinated fibers convey in terms of sensory information?

Back 61

-Slow pain (burning)
-Thermal sense (both small, unmyelinated and small, myelinated fibers)

Front 62

What levels in the spinal cord are the posterior columns found?

Back 62

-ALL levels of the spinal cord (remember fasiculus cuneatus is only T6 and above)

Front 63

What sensory modalities are the posterior columns responsible for?

Back 63

-Vibration
-Tactile discrimination
-Position sense (kinesthesis)

Front 64

How are the primary afferent fibers of the posterior columnns arranged (by level) in the spinal cord?

Back 64

-Lower goes medial (right up against posterior median septum)
-Higher goes lateral
-From Medial-->Lateral
(S5, S4, S3, S2, S1, L5, L4, L3, L2, L1, T12, T11, T10, T9, T8, T7, T6, T5, T4, T3, etc)

Front 65

How many spinal nerves are there by level?

Back 65

8Cervical - Above named vertebrae
12Thoracic - Below named vertebrae
5Lumbar - Below named vertebrae
5Sacral
1Coccyeal

Front 66

Where do primary afferent fibers of the posterior column tract enter the spinal cord?

Back 66

Medial to the zone of Lissauer. Lower spinal levels go medially (right up against posterior median septum) and higher levels go more laterally

Front 67

What kinds of fibers make up the posterior column ascending tract? What sensory modalities?

Back 67

-Type I and II
-Vibration, tactile discrimination, position sense

Front 68

Where are bodies of the secondary afferent neurons of the posterior column system found?

Back 68

In the medulla (nucleus gracilis and nucleus cuneatus)

Front 69

Is there any crossing over of the posterior column system?

Back 69

No, ipsilateral up and down!

Front 70

What damage would you see with a dorsal rhizotomy (posterior column tract)?

Back 70

-Anterograde degeneration in the ipsilateral posterior funiculus above the site of the lesion
-Terminal degeneration in the ipsilateral medulla (nucleus gracilis)
-Retrograde chromatolysis in ipsilateral dorsal root ganglion
-Loss of ALL cutaneous sensation in ipsilateral lower extremity (recall that the dorsal root contains afferent information from the anterolateral spinothalamic system as well!)

Front 71

What damage would you see with desctruction of the fasiculus gracilis at L1?

Back 71

-Anterograde degeneration of the most lateral portion of fasiculus gracilis (L1-S5)above site of lesion
-Terminal degeneration in the ipsilateral nucleus gracilis in medulla
-Chromatolysis of neurons in ipsilateral dorsal root ganglion.
-Loss of tactile discrimination and kinesthesis of ipsilateral lower extremity.

Front 72

What level is the DNC?

Back 72

T1-L2

Front 73

What spinal levels contain the IML (intermediolateral lateral nucleus)? What type of neurons call the IML home?

Back 73

-T1-L2
-Preganglionic neurons of the sympathetic nervous system

Front 74

Function of Lateral corticospinal tract

Back 74

Voluntary, fine, fractionated movement

Front 75

Function of Rubrospinal tract

Back 75

Flexors of upper ext (clinically insignificant)

Front 76

Function of Anterior corticospinal tract

Back 76

Voluntary; neck muscles and prox UE; postural movements of head and UE (clinically insignificant)

Front 77

Function of Lateral vestibulospinal tract

Back 77

Extensors of UE/LE; "righting reflex" (unopposed LVST is responsible for decerebrate rigidity)

Front 78

Function of Medial vestibulospinal tract

Back 78

control positioning and posture of the head; coordinate head movements with eye movements

Front 79

Function of Pontine Reticulospinal Tract

Back 79

axial and proximal musculature for postural tone and adjustments, MINOR role in decerebrate rigidity

Front 80

Function of Medullary Reticulospinal Tract

Back 80

Inhibits axial and proximal limb muscles during sleep (sleep atonia)

Front 81

Function of Posterior Columns

Back 81

vibration, 2-point discrimination, conscious proprioception

Front 82

Function of Anterolateral Spinothalamic System

Back 82

pain, thermal sense, light touch

Front 83

Function of Posterior Spinocerebellar Tract

Back 83

unconscious proprioception (LE), fine coordination of posture through individual muscles

Front 84

Function of Cuneocerebellar Tract

Back 84

unconscious proprioception (UE), fine coordination of posture through individual muscles

Front 85

Function of Anterior Spinocerebellar Tract

Back 85

unconscious proprioception (LE), gross coordination of posture through LE as a whole

Front 86

Is the posterior spinocerebellar tract found at all spinal cord levels?

Back 86

No, this ascending tract starts at the DNC at level L2!