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Systems Neuroscience > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

What is the role of MVST?

A

Input from the canals, projects bilaterally through the MLF, both excitatory and inhibitory to motor neurons innervating neck and upper limb.

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2
Q

What is the role of LVST?

A

Input from the canals and otolithic organs, projects ipsilaterally through anterior fasciculus and is excitatory to extensor muscle motor neurons for proximal limb and trunk.

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3
Q

What directions are Pitch, Roll and Yaw?

A

Pitch: shaking head yes
Roll: Shoulder to shoulder
Yaw: Shaking head no, horizontal direction

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4
Q

What are the steps of vestibular transduction?

A
  1. Hair bundle deflection towards tallest kinocilium, opens MET channels.
  2. K+ influx from endolymph, depolarizes and opens voltage dependent channels.
  3. Ca2+ influx causes fusion of synaptic vesicles and release of glu.
  4. Glu activates postsynaptic AMPA on primary vestibular afferent.
  5. Afferent depolarizes, gives rise to more action potentials, travels to CNS.
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5
Q

How are hair cells arranged in the semicircular canals?

A

Hair celsl are in a line facing the same direction, so all depolarize on one size and hyperpolarize on the other.

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6
Q

How are hair cells arranged in the utricle and saccule?

A

Hair cells change direction half way through, so some are inhibited and some are excited on each side of the head.

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7
Q

Where are cell bodies of the vestibular division of CN VIII found?

A

In superior and inferior division ganglia.

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8
Q

What are the types of vestibular afferents?

A

Calyx, Bouton and Dimorphic.

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9
Q

What are the characteristics of calyx afferents?

A

Reside in the central zone of the epithelium, high phase leads with less gain.

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10
Q

What are the characteristics of bouton afferents?

A

Reside in the peripheral zone, have low phase leads and more gain.

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11
Q

What are the characteristics of dimorphic afferents?

A

Reside throughout central and peripheral zones, and vary in phase lead and gain. These are the majority of afferents.

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12
Q

How to calyx, dimorphic and bouton afferents differ?

A

Conduction velocity, discharge regularity, sensitivity and response dynamics (timing).

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13
Q

What is meant by Gain and Phase in the vestibular system?

A

Gain is a measurement of response to a stimulus, expressed in spikes per degrees, and can vary up to 20 fold.
Phase is the timing of the afferent response with respect to the stimulus, which provides information about wether the afferent is concerned with velocity or acceleration.

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14
Q

What is CV*?

A

The measure of normalized discharge regularity. By taking the standard deviation of interspike interval (ISI) divided by the mean, you get CV, and to normalize CV you use a known ISI.

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15
Q

What do low and high CV* values indicate?

A

Low indicates regular discharge, which are more in phase with the stimulus and high indicates irregular discharge which are more sensitive (gain).

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16
Q

What do leading, lagging and in sync afferents mean for what the afferent pays attention to?

A

Leading - cares about acceleration
Lagging - cares about position
In sync - cares about velocity

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17
Q

Where does the Vestibular Nuclei receive inputs from?

A

CN VIII, optokinetic signals, neck proprioception, purkinje cell projections, spinal, descending fibers.

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18
Q

Where does the vestibular nuclei give output to?

A

CNs III, IV, VI, Spinal motor, cerebellum, comissural, thalamus, autonomic, ascending fibers.

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19
Q

What are the vestibular nuclei?

A

Superior, Lateral, Medial, Inferior

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20
Q

How are central neurons organized in the vestibular system and how is convergence beneficial?

A

Mostly converging, and not organized based on discrete metrics. Convergence allows for varied information and lower thresholds. Single afferents do not register perceptually so multiple sources give information in order to register small stimuli.

21
Q

What is the vestibular ocular reflex?

A

Movement of eyes in equal and opposite direction to head movement, gaze remains fixed. Gain = 1, phase = 0
Neurons in VOR only care about head movement.
Requires input to both left and right eyes to keep eyes fixed as the head moves.

22
Q

What is the difference between rotational VOR and translational VOR?

A

Rotational is rotation of the head and translational is side to side movement of the head. Rotational receives information from the semicircular canals and translational from the utricle and saccule.

23
Q

What is a Position Vestibular Pause neuron?

A

These neurons pause when the eyes move.

24
Q

What is the efferent copy signal?

A

This is used when planning a movement, where the body sends a motor command to a muscle and then internall matches what the input would be from the vestibular system and blocks the vestibular signal based on the movement.

25
Q

What is the role of the rostral fastigeal nucleus?

A

rFN neurons are likely the source for discriminating active versus passive movements.

26
Q

What are the sensory inputs for Spinal reflexes?

A

Muscle spindle - via 1a afferents, information about muscle length.
Golgi tendon organ - via 1b afferents, information about muscle tension.

27
Q

What is the difference between a motor neuron pool and a motor unit?

A

Motor Unit is one motor neuron and the many fibers it innervates, and the motor neuron pool is all of the neurons that innervate a single muscle.

28
Q

What is the role of alpha and gamma motor neurons?

A

Alpha motor neurons are the drivers of muscle contraction and gamma motor neurons re-adjust muscle spindles.
These interactions maintain muscle sensitivity to motor requirements.

29
Q

What is reciprocal inhibition?

A

Inhibition of antagonizing muscles through inhibitory interneurons.

30
Q

What is the lower and upper loop?

A

Lower loop is the local, short reflex pathway, and upper loop or long loop is the pathway modulating events via integration in the cortex such as basal ganglia and primary areas.

31
Q

What disorders are suggested by absent or hypoactive stretch reflex?

A

Sensory or motor axons, motor neuron disease such as ALS, muscle degeneration and supraspinal center issues.

32
Q

What disorders are suggested by hyperactive reflex?

A

Damage to supraspinal centers, spinal cord injury - loss of descending input no longer modulates the local activity resulting and overcompensation.

33
Q

What is locomotion?

A

Rhythmic activity generated without sensory input such as two step cycles for a stepping pattern which are generated at the spinal level.

34
Q

What is mutual inhibition model for central pattern generators?

A

This is where inhibitory neurons feedback from each side to impact the contralateral neuron in the pathway.

35
Q

What is half center inhibition?

A

Supression of antagonistic pathway which generates rhythmicity and can be measured when stimulating nerves.

36
Q

What are key components of locomotion?

A

Central Pattern generator in spinal cord circuits, Sensory input from limbs and adaptation by descending signals.

37
Q

What features are used to classify spinal neurons?

A

Cytoarchetecture, physiology, connectivity, transcriptional profile, cell lineage, behavior.

38
Q

What are the regions of the spinal cord?

A

Dorsal - sensory
Intermediate - Integration
Ventral - Motor

39
Q

How is the dorsal area of the spinal cord organized?

A

Layered organization by neurotransmitter type

40
Q

How is the ventral area of the spinal cord organized?

A

Organized by area of body innervated, such as axial, distal and proximal muscles.

41
Q

What morphogen gradients result in different cellular identities?

A

Dorsal - BMP
Ventral - Shh
Posterior - Shh
Anterior - Wnts

42
Q

What is the length-tension relationship?

A

When a muscle is stretched fully and when it is fully shortened it cannot generate as much force. There is an operating range.

43
Q

What is the force-velocity tradeoff?

A

Movement occuring at a high speed cannot exert as much force, the most force is exerted in a lengthening contraction.

44
Q

What is motor unit recruitment?

A

Initially during a contraction, small motor units are recruited since they are easier to get to fire, as the contraction increases, larger motor units are recruited and more force can be generated.

45
Q

What are primary and secondary afferents?

A

Primary afferents are sensitive to small changes, increasing firing during stretch and then ceasing.
Secondary afferents are sensitive to the static stretch of muscle, continuing to fire while the muscle is stretched.

46
Q

What are the descending pathways?

A

Corticospinal, rubrospinal, propriospinal, medullary reticulospinal, pontine reticulospinal, vestibulospinal (not as involved in voluntary movements).

47
Q

How is the corticospinal tract organized?

A

Dorsolateral - fine motor
Ventromedial - gross motor

  • lesion to the lateral CST causes initial paralysis with recover, but no recovery of fine movement of fingers
  • lesion to medial CST allows for fine motor skill use but no standing/walking
48
Q
A

Systems Neuroscience (2 decks)

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