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Module 8 > Regulation of Motor Control & Anatomy of Limbic System > Flashcards

Regulation of Motor Control & Anatomy of Limbic System Flashcards

1
Q

what are the mature structures of the mammalian forebrain

A

telencephalon: cerebral cortices, limbic system and basal ganglia
diencephalon: thalamus, hypothalamus, pituitary gland, mammillary bodies

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2
Q

what are the divisions of the limbic system (7)

A
  1. right cingulate cortex
  2. left cingulate cortex
  3. hippocampus
  4. amygdala
  5. mammillary body
  6. septum
  7. fornix
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3
Q

what is the limbic system involved in

A

control of emotion, learning and memory

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4
Q

what is the structure of the hippocampus

A

3 layer cortical structure

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5
Q

what is the function of the hippocampus

A
  1. spatial memory
  2. transfer of some types of information for long term memories
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6
Q

what are the cells of the hippocampus

A
  1. “grid” cells that provide a universal neuronal coordinate system for spatial navigation
  2. “place” cells are activated only when animal is in a specific place
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7
Q

what is the hippocampus role in explicit memories

A
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8
Q

what do hippocampal lesions impact

A

explicit memory

anterograde amnesia –> unable to recall anything

implicit memories and working memory intact

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9
Q

what is the structure of the amygdala

A

collection of nuclei

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10
Q

what is the function of the amygdala

A

affective behaviours and other species typical behaviour

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11
Q

what are the neurons in the amygdala

A

multimodal and respond to more than one sensory modality

multiple bidirectional with hypothalamus, hippocampus, cortices and brain-stem and regulates neural activity associated with emotions

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12
Q

what do lesions of the amygdala cause

A
  1. tameness and loss of fear
  2. indiscriminate dietary behaviour (eat previously rejected foods)
  3. greatly increased autoerotic, homosexual and heterosexual activity
  4. tendency to attend to and react to every visual stimulus
  5. tendency to examine all objects by mouth
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13
Q

what role does the amygdala play in fear response

A

learned responses such as to avoid specific animals, places and objects that are associated with danger

fear conditioning (pavlovian methods)

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14
Q

what is the fornix structure

A

bundle of fibres along medial aspect of hemisphere

inter-connections with hippocampi on both sides of the two cerebral hemispheres

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15
Q

what is the the function of the fornix

A

primarily connects the hippocampus to the mammillary body of the hypothalamus

other fibres connect directly to the anterior nucleus of the thalamus

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16
Q

what is the role of the fornix in emotional processing

A

malfunctions of fornix signalling have been associated with multiple sclerosis

demyelination of fibre bundles of the fornix has been identified as a functional consequence and symptoms of cognitive dysfunction such as dementia, short term memory impairements and long term learning impairments

alzheimers disease, schizophrenia

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17
Q
A
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18
Q

what is the structure of the mammillary body

A

intricately connected with the hippocampal formation, fornix, amygdala and midbrain

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19
Q

what is the primary function of the mammillary body

A

associated with recollective memory

emotion and goal directed behaviour

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20
Q

what causes significant damage to the mammillary bodies and what does it cause

A

trauma

stroke

tumours

alcoholism

results in anterograde amnesia and reduced motivation

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21
Q

what is the function of the septum

A

emotional behaviours, sexual behaviour, aggressive behaviour, modulation of autonomic functions, attention and memory functions

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22
Q

what does septum recieve input from

A

hippocampus, amygdala, hypothalamus and midbrain

23
Q

where does the septum project to

A

hippocampus and dentate gyrus (via the fornix), the thalamus and several hypothalamic nuclei

24
Q

what do septal lesions induce

A

rage and overt aggression

25
Q

what is the structure of the cingulate cortex

A

reciprocal connections with the limbic (medial dorsal and anterior) thalamic nuclei and with other limbic areas including the subiculum and entorthinal cortex (hippocampal formation)

26
Q

where do cingulate cortical neurons send axons to

A

to motor and premotor areas including the striatum, motor and premotor cortex

27
Q

what is the cingulate cortex involved in

A

planned motor movements

28
Q

what do lesions to the cingulate cortex cause

A

indifference to pain and other sensations that have strong emotional connotations

produce social indifference and apathy

eliminate emotional intonation in speech

personality changes

lesions in posterior cingulate cortex result in diminished ability to perform spatial navigation

29
Q

what are bilateral anterior cingulate lesions cause

A

have been done as psychosurgery to alleviate intractable pain and to incapacitate anxiety, obsessive-compulsive behaviour and intractable depression

30
Q

what is the structure of the basal ganglia

A

four nuclei

31
Q

what is the function of the basal ganglia

A

voluntary movement

32
Q

what are the outputs and inputs of the basal ganglia

A

don’t have direct input or output with spinal cord

input from the cortex and output to the midbrain

another output pathways via the thalamus projects to the frontal, premotor and motor cortices

33
Q

what is the neural basis of parkinson’s disease

A

loss of dopamine leads to increased output of the basal ganglia

overactivity of the indirect pathway results in hypokinetic disorders (impaired initiation of movement and reduced voluntary movement)

34
Q

what are the surgical interventions of parkinson’s disease

A
  1. lesions of the subthalamic nucleus reduces symptoms by eliminating the excessive output from the internal segment of the globus pallidus
  2. lesions of the internal segment of globus pallidus prevents abnormal output and partially restores voluntary movement
35
Q

where does control of motor activity come from

A

feedback through sensory input and through prediction from previous activity

36
Q

what is the hierarchy of motor control

A

higher animals have additional control from higher centres in brain (encephalization)

spinal cord “expects” input from higher centres –> spinal shock occurs when cut

37
Q

how does the hierarchy system of motor control work

A
  1. sensory input coming in/being processed at higher centres
  2. higher centres regulate lower centres –> tonic inhibitory effect
  3. lesions at higher centres –> loss of integrated function, abnormal responses
38
Q

what is the first step in the hierarchy of motor control

A
  1. sensory input goes to limbic system (motivation)
  2. basal ganglia (initiation of movement)
  3. cerebellum (coordination of movement)
  4. motor cortex (refines action)
  5. movement (spinal cord)
39
Q

what are the descending pathways in the control of motor responses

A
  1. pyramidal tract
  2. extrapyramidal tract
40
Q

what is the pyramidal tract

A

motor neurons that originate in the frontal cortex and terminate in the spinal cord (corticospinal) or brain stem (corticobulbar)

41
Q

what is the extrapyramidal tract

A

located in the pons and medulla of the midbrain and involved in involuntary movements

42
Q

what is pyramidal tract syndrome

A

characterized by spasticity and paralysis

43
Q

what is the extrapyramidal tract syndrome

A

characterized by involuntary movements, muscular rigidity and immobility without paralysis

44
Q

what are the upper motor neurons in the pyramidal and extrapyramidal tracts

A

extrapyramidal: reticulo-spinal, vestibulo-spinal, rubro-spinal, tecto-spinal
pyramidal: cortico-spinal

45
Q

what are the tracts shown

A
46
Q

what is the corticospinal tract

A

starts in cortex

required for fine, skilled movement

fibres terminate on inter-neurones in the spinal cord

47
Q

what is the reticulospinal tract

A

“old” tract

basic instincts (startle reaction), postural, initiates locomotion

48
Q

what is the rubrospinal tract

A

acts mainly on flexors, postural (where nuclei reside)

49
Q

what is the tectospinal tract

A

input from vision and hearing

acts on cervical vertebrae

orientates head

50
Q

what is the species variation in the tracts

A

humans: lots of pyramidal
horses: lots of extrapyramidal
dogs: lots of extra and less pyramidal than horses

51
Q

what are effects of lesions in the descending tracts

A

lead to hyperactivity in extensor muscles

this is because descending tracts are inhibitory

52
Q

what are the effects of lesions shown here

A
  1. decorticate: spastic
  2. decerebrate: rigid
  3. spinal: flaccid
53
Q

fill in the blanks on this pathway

A
54
Q

fill in the blanks of this pathway

A

Module 8 (43 decks)

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