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Organ Systems III > OS III Exam III > Flashcards

OS III Exam III Flashcards

1
Q

What is the difference between lower and upper motor neurons?

A

Upper: cerebral cortex, reticular formation, and vestibular nuclei. Lower: Alpha motor neurons, final common pathway.

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2
Q

What is a muscle spindle and how does it respond to changing muscle length?

A

Intrafusal muscle fibers parallel to extrafusal, surrounded by CT and wrapped with annulospiral sensory neurons. When stretched, physically gated channes in the sensory nerve open (Na/Cl) to generate a potential.

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3
Q

Describe the myotatic reflex.

A

Stretch spindle -> IA & II afferents -> alpha motor neuron -> contract same and synergistic muscles/ inhibit antagonist muscles (relax)

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4
Q

How does gamma motor neurons activity affect myotatic reflexes?

A

Set the sensitivity of the spindle.Tighter spindle = more sensitivity to I and II afferent neurons.

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5
Q

What controls gamma motor neurons: brain stem or muscle receptors?

A

Brain stem

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6
Q

What is a Golgi tendon organ and how does it respond to muscle tension?

A

Embedded in tendon and is sensitive to stretch/tension at the tendon. Maintains tension in response to stretch. Ib afferents inhibit alpha motor neurons to the same muscle.

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7
Q

Is the Golgi tendon organ regulated by gamma motor neurons?

A

NO

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8
Q

What is crossed extension reflex/flexor withdrawal?

A

Pain afferent (Agamma) cause extension of contralateral limb and flexion of limb affected.

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9
Q

Describe propriospinal neurons and their action on spinal reflexes.

A

Organize all the limbs together (e.g. walking, reaction to stimulation) Medial propriospinal neurons regulate full body posture, while lateral propriospinal neurons regulate fine motor movement.

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10
Q

What are some general functions of upper motor neurons?

A

Posture, balance, movements

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11
Q

Describe the motor control functions of the vestibulospinal and reticulospinal tracts.

A

Vestibulospinal relays head movement activity to spinal cord. Reticulospinal regulates muscle tone and flexor responses, coordinates complex actions. Reticulospinal has medial (pons) and lateral (medulla) tracts. The medial facilitates movements and muscle tone (via gamma motor neurons) while the lateral inhibits voluntary actions and reduces tone. Maintains posture and balance!

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12
Q

What is the antigravity posture and what produces it?

A

Lower limbs extended, upper limbs flexed. Vestibulospinal and reticulospinal tracts.

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13
Q

What is the internal capsule?

A

Bundle of axons in cerebral hemisphere that is a common site for strokes.

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14
Q

Describe the corticonuclear tract and what it does.

A

Projects to motor neurons of cranial nerves and controls muscles of face, head, and neck.

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15
Q

Describe the corticospinal tract and what it does. </p>

A

<p>Projects from the cortex through the internal capsule, cerebral peduncles, medulla (decussating), finally to alpha and gamma motor neurons of spinal cord. Lateral portion (90% decussed) controls fine motor movement. Medial portion (10% non-decussed) controls posture of neck and trunk. </p>

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16
Q

Describe the corticoreticular tract and what it does. </p>

A

<p>Primary and premotor cortices project to pontine and medullary reticular formation. Smoothes out movemtns and breaks up patterns. </p>

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17
Q

The medullary decussation?

A

90% of the corticospinal motor neurons cross, while 10% do not

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18
Q

How do the anterior and later corticospinal tracts differ in structure and function?

A

Anterior (ventral) has to do with the posture of the neck and trunk. The lateral deals with fine motor movements.

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19
Q

Compare lower motor neuron and upper motor neuron disease.

A

Lower motor neuron disease = flaccid paralysis. Upper neuron disease = spasticity.

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20
Q

What are the aspects of spasticity?

A

Active, but inappropriate muscle contraction. Can be caused by stroke (disruption of cortical projections to reticular formation). E.g anti-gravity posture, hypertonicity (clasp knife reflex), Babinski sign.

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21
Q

What two tracts does a stroke in the motor cortices disrupt?

A

Corticospinal, Corticoreticular

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22
Q

Compare the functions of the primary, supplementary and pre-motor cortices.

A

Primary: what to do and when to do it, encodes force, direction, extent, and speed of movements. activates muscles for discrete movments. Supplementary/Premotor: develop strategies for motor programs, high level integration with sensory information. ensures correct motor sequence (rehearsal)

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23
Q

What is the key function of the pre-motor cortex?

A

INTENTION. Spatial and sensory information as well as abstract rules. Based on memory.

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24
Q

What is Broca’s area?

A

Part of premotor cortex that control motor preparation for speech.

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25
Q

What is efference copy?

A

A copy of the motor program sent from the primary motor cortex to the somatosensory cortex.

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26
Q

How does efference copy play a role in self awareness?

A

It allows the somatosensory to compare what it expects to feel with what it actually receives from the periphery. It can feedback to refine the motor program until it matches.

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27
Q

What two concepts make up self-awareness?

A

Self-agency and Self-ownership

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28
Q

What are mirror neurons and where are they located?

A

Neurons that unify action perception and execution. Located at the inferior premotor area and inferior parietal cortex.

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29
Q

Describe the pathway from cerebellar cortex to motor cortex and back.

A

Closed loop from cerebellar cortex to dentate or fastigial nucleus to ventrolateral nucleus (thalamus) to the cortex to the pontine nuclei back to the cerebellar cortex.

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30
Q

Describe the location and functions of the cerebrocerebellum.

A

Lateral hemispheres of the cerebellum. Project to dentate nuclei to thalamus(ventrolateral nucleus) to cortex. Initiate voluntary movement by projecting anticipatory information to the primary motor cortex.

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31
Q

Describe the location and functions of the vestibulocerebellum.

A

Sliver at the base of the cerebellum. Receives input from vestibular system and projects to vestibular nuclei of emdulla. Controls posture, balance, & eye movements. Connected with VOR.

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32
Q

Describe the location and functions of the spinocerebellum.

A

Vermis (spine of cerebellum). Feedback control for ongoing movements. Detect disparaties

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33
Q

How do the vestibulocerebellum, spinocerebellum, and cerebrocerebellum differ in their connections with the motor cortex and spinal cord?

A

Go via different nuclei. Vestibulo -vestibular nuclei. Spino- fastigial and interposed nuclei. Cerebro -dentate.

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34
Q

Key word for spinocerebellum?

A

Comparer (in execution)

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35
Q

Key word for cerebrocerebellum?

A

Anticipation (in planning/programming)

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36
Q

Key word for vestibulocerebellum?

A

Balance

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37
Q

How do the vestibulocerebellum, spinocerebellum, and cerebrocerebellum participate in motor learning?

A

Allows motor movements to be precise and automatic. Your cerebellum gets very good at predicting.

38
Q

What is “intention tremor”? Why is the latter in quotes?

A

Not a true tremor. Oscillations due to damage of the cerebellum. Oscillatory movement of a limb as it approaches a targe.

39
Q

What is dysmetria?

A

The inability to control range of movement.

40
Q

What is ataxia?

A

Lack of smoothly coordinated movement.

41
Q

What is dysarthria?

A

Inability to articulate words correctly

42
Q

What is dysdiadochokinesia?

A

Inability to perform rapid alternating movements

43
Q

What roles does the cerebellum play in cognition and visceral functions?

A

Coordinate cognitive tasks to obtain a certain goal: mental flexibility, multitasking, problem solving.

44
Q

For example, how is an unmyelinated nerve fiber (axon) designated in terms of the compound action potential?

A

It would be further out or slower, the further you move down the nerve pathway.

45
Q

Describe the compound action potential and what it tells you.

A

Compound action potentials are the sum of action potentials measured over time at a particular site on the nerve. Indicates clusters of axons with different conduction velocities and degrees of myelination.

46
Q

What is meant by intensity coding?

A

Increased amplitude of receptor potential increases the frequency of AP and thereby the intensity.

47
Q

What impact do slow vs fast adapting receptors have on the message sent to the brain?

A

Rapid is quick impulses to indicate “that it occurs” whereas the slow is a gradual decrease in receptor activity, “what is occuring”

48
Q

What are cutaneous receptive fields and how do they contribute to tactile localization?

A

Area of skin innervated by ONE sensory neuron. Can not localize within the receptive field.

49
Q

How are sensory modalities distinguished by the peripheral nerves?

A

TRP (Transient receptor type) ion channels repond optimally to ONE stimulus and less to others. Adequate stimulus is required to determine modality.

50
Q

Describe some examples of the kinds of information that slow and fast adapting exteroceptors mediate.

A

Slow: merkel for texture and form. ruffini for stretch. Fast: meissner for movement across the skin. pacinian for vibration.

51
Q

What type of axons mediate pain, temperature and non-discriminative touch?

A

Pain: C and Adelta. Temp: C and Adelta. FREE NERVE ENDINGS!!

52
Q

What is proprioception?

A

Somatic sensitivity to position, location, orientation, and movement of joints, muscles, and fascia.

53
Q

Describe the dorsal column lemniscal system in terms of: Modalities

A

Discriminative touch, proprioception.

54
Q

Describe the dorsal column lemniscal system in terms of: Location

A

Runs up the dorsal side of the spinal cord in the white matter.

55
Q

Describe the dorsal column lemniscal system in terms of: projection and decussation of first, second and third order neurons

A

Projects through spinal cord, brain stem, and thalamus to the cerebral cortex. First order form the dorsal columns, second order decussate in the medulla, third order form part of internal capsul and project to cortex.

56
Q

Describe the anterolateral system in terms of: Pathways

A

Non-discriminative touch, pain, temperature.

57
Q

Describe the anterolateral system in terms of: Location of second order neurons

A

The second order neurons decussate to anterolateral system.

58
Q

Compare the neo- and paleospinothalamic pathways

A

Neospinothalamic projects to lateral thalamus and contributes to localization of sensation. Paleospinothalamic projects to reticular formation, medial thalamus, and cortex for qualitative aspects.

59
Q

Where do anterolateral third order neurons project to?

A

From the lateral thalamus to primary somatosensory cortex and cingulate gyrus and insula.

60
Q

Give a general description of the reticular formation

A

Tract that runs through the brain stem into the thalamic and limbic regions and is responsible for wake/attention.

61
Q

Compare the medial and lateral projections of the anterolateral system third order neurons in terms of location and perception

A

Medial projections go to the insula and cingulate gyrus to get a qualitiatve. The lateral projecation ptojects to primary somatosensory cortex somatotopicaly for localization.

62
Q

Account for the peculiar symptoms of syringomyelia and Brown-Sequard syndromes

A

Cysts in the grey matter disrupt the decussation of anterolateral second order neurons decussation. Causing bilateral pain/temp lost, but discriminative touch still intact.

63
Q

Describe the anatomy and sensory projections of the trigeminal nerve.

A

CN V projects from the pons and is divided into 3 divisions: opthalmic (oral cavity, forehead, dorsum of the nose), maxillary (nasal cavity, cheek area), mandibular (oral cavity, chin, side of face, external acoustic meatus, tympanic membrane, motor to masticators).

64
Q

What are the different nuclei that mediate the different modalities?

A

Principle Sensory: discriminative touch. Spinal Trigeminal: pain and temp. Mesencephalic: proprioception of masticators. Motor: motor to masticating muscles.

65
Q

What are dermatomes?

A

Area of skin innervated by a certain level of the spinal cord.

66
Q

How do the body and face dermatomes compare?

A

Discontinuous stripes. Face looks like an onion.

67
Q

How many layers are there in neocortex?

A

6 layers

68
Q

Which layers of the neocortex contain the major input receiving cell and the output cells? What are those cells called?

A

Stellate: input, IV. Pyramidal: output, V.

69
Q

What are Brodmann’s areas?

A

Areas of cortex that are histologically distinguishable.

70
Q

What does fMRI measure? No paramagnetic details needed here!

A

Measures brain activity and blood flow.

71
Q

Describe the general organization of the thalamus.

A

Cluster of nuclei, bilaterally project sensory/motor/integrated neural information to and from the cortex.

72
Q

Which areasof the thalamus are associated with the somatosensory cortices?

A

VPL and VPM

73
Q

Where and what is the primary somatosensory cortex?

A

The post-central gyrus. Elaborate and contextualize sensory information into meaningful experiences.

74
Q

What are cortical columns?

A

Neurons with similar sensory receptive properties (modality and RF)

75
Q

What is somatotopy?

A

The point-for-point correspondence of an area of the body to a specific point on the central nervous system

76
Q

The homunculus?

A

Representation of the body within the cortex in proportion to the density of sensory receptors in that area of the body.

77
Q

What is meant by cortical plasticity?

A

Changes in cortical sensory representation with experience/learning.

78
Q

Give a general description of lateral inhibition.

A

Dorsal column nuclei enhace difference between somatosensory RFs, by inhibiting peripheral RFs.

79
Q

How does lateral inhibition impact incoming somatosensory information?

A

Refines input. Greater signal/noise ratio.

80
Q

How do the sensory and motor cortices affect lateral inhibition and information processing in the ascending somatosensory system?

A

Select for only the most important sensory inputs related to movement.

81
Q

What is two-point discrimination?

A

Ability to discriminate between seperate but simultaneous pin pricks to the skin.

82
Q

What part of the somatosensory system is responsible for two point discrimination?</p>

A

Dorsal column lemiscal system

83
Q

What are the somatosensory “dorsal and ventral streams”?

A

Ventral stream goes to secondary somatosensory cortex bilaterally, what? Dorsal stream projects to posterior parietal cortex, where?, how?

84
Q

What happens to somatosensory information as it spreads from primary somatosensory into SII and association cortices along either the dorsal or ventral streams?

A

It integrates more and more receptive fields, more meaningful wholes.

85
Q

What aspects of somatosensory information are associated with the posterior parietal cortex? With the secondary (SII) cortex?

A

PPC: Space coded in a body-centered reference frame. SII: Develop 3D picture of the object.

86
Q

What role does the posterior parietal cortex play in how vision and somatosensory information impacts somatosensory awareness?

A

Creates body schema for embodiment of sensory experience. Generates conscious body image.

87
Q

What are the characteristics and cortical issues associated with phantom limb phenomena?

A

Latent sensory pathways from severed limbs still creating somatoperception (though somatorepresentation realizes the limb is gone).

88
Q

What is astereognosis?

A

Inability to ID object by touch.

89
Q

What is neglect syndrome? What part of the brain is usually involved in neglect?

A

Deficit in attention to and awareness of one side of space. Right parietal lobe lesion.

90
Q

What is the difference between illusion and delusion?

A

lllusion: you perceive something that isn’t there. Delusion: false belief about what isn’t there

Organ Systems III (5 decks)

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