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Neuroanatomy (OCCU 6140) > Midterm 7 > Flashcards

Midterm 7 Flashcards

Gait Basal ganglia and dopamine

1
Q

What are the two phases of the gait cycle?

A

Stance phase and swing phase

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2
Q

Stance phase involves which actions?

A

Initial contact (heel strike)
Load response (foot flat)
Mid-stance (single-leg stance)
Terminal stance (heel-off)
Pre-swing (toe-off)

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3
Q

Swing phase involves which actions?

A

Initial swing (acceleration)
Mid-swing
Terminal swing (deceleration)

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4
Q

What are central pattern generators?

A

Spinal cord and brainstem circuits responsible for programmed, rhythmic movements

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5
Q

Central pattern generators consist of ______________ and ________________ in the central nervous system.

A

Central pattern generators consist of motor neurons and interneurons in the central nervous system.

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6
Q

Central pattern generators consist of motor neurons and interneurons in the central nervous system.

Circuits for chewing, swallowing and breathing are located in the _________________.

Circuits for locomotion are located in the ________________.

A

Chewing, swallowing and breathing = brainstem

Locomotion = spinal cord

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7
Q

Central pattern generators can be of three types (hint: how are they active?):
1)
2)
3)

A

1) Spontaneously active
2) Triggered by a specific sensory stimulus
3) Voluntary and triggered by higher motor centers

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8
Q

Locomotion is more than just a series of reflexes, the timing of the different muscle contractions is ___________ and ____________.

A

Complex and fast.

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9
Q

What is the key characteristic of locomotion in animals that makes them different from humans?

A

In animals, each limb has its own central pattern generator.

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10
Q

Central pattern generators activate __________________, eliciting stepping.

A

Central pattern generators activate lower motor neurons, eliciting stepping.

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11
Q

In animals, at times signals are sent to lower motor neurons for ___________________ and at other time, signals are sent to lower motor neurons for __________________.

A

Flexor muscles
Extensor muscles

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12
Q

In animals, for locomotion to occur, each limb requires a _____________________ that controls the timing of various muscles.

A

For locomotion to occur, each limb requires a central pattern generator that controls the timing of the various muscles.

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13
Q

Central pattern generators can produce rhythmic movements in the absence of ________________________.

A

Central pattern generators can produce rhythmic movements in the absence of descending control.

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14
Q

What is fictive locomotion?

A

Fictive locomotion is a benchmark method used in locomotor studies where the spinal cord is dissected out or the entire animal is paralyzed and electrodes are placed on ventral root s or musculature to measure motor neuron output.

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15
Q

What are the two mechanisms of rhythm generation?

A

1) Pacemaker networks
2) Reciprocal inhibition

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16
Q

What is a pacemaker network?

A

Pacemaker networks are a mechanism of rhythm generation.

A neuron can act as an oscillator that drives other neurons into a rhythmic pattern.

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17
Q

Newborns demonstrate stepping despite not having mature descending tracts, true or false?

A

true

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18
Q

Rhythmic involuntary movements are never observed in people with spinal cord injury, true or false?

A

False, rhythmic involuntary movements are observed in people with spinal cord injury

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19
Q

__________________ can induce stepping movements in people with spinal cord injury.

A

Epidural spinal cord stimulation can induce stepping movements in people with spinal cord injury.

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20
Q

Locomotion central motor pattern generators are likely located in the _______________ and ____________________ of the spinal cord.

A

Locomotion central motor pattern generators are likely located in the lower thoracic and lumber regions of the spinal cord.

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21
Q

Humans rely more on ___________________ influences than other animals.

A

Humans rely more on supraspinal influences than other animals.

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22
Q

What is the role/function of supraspinal input?

A
  1. Activates spinal central pattern generators
  2. Controls intensity of central pattern generators
  3. Maintains equilibrium during locomotion
  4. Adapts limb movements to external conditions
  5. Coordinates locomotion with other motor behaviors
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23
Q

Which part(s) of the brain is involved in initiating and regulating gait?

A

Basal ganglia
Supplementary motor area

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24
Q

Which part(s) of the brain is involved in executing movement in gait?

A

Primary motor cortex
Premotor cortex
Supplementary motor area

(motor cortex)

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25
Q

Which part(s) of the brain is involved in somatosensory function relating to gait?

A

Parietal cortex
Precuneus

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26
Q

Which part(s) of the brain is involved in relaying sensory information in relation to gait?

A

Thalamus

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27
Q

Which part(s) of the brain is involved in visual processing related to gait?

A

Occipital cortex

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28
Q

The control region for locomotion is located in the ___________________ in the caudal pons and medulla - the ___________________________ region.

A

The control region for locomotion is located in the reticular formation in the caudal pons and medulla - the mesencephalic locomotor region (MLR)

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29
Q

In animals, electrical stimulation of the mesencephalic locomotor region (MLR) produces…

A

Locomotor pattern

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30
Q

The increase of stimulation of the mesencephalic locomotor region via activation of brainstem reticulospinal neurons results in _____________________________.

A

Increased gait speed.

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31
Q

The mesencephalic locomotor region is important for _______________, ________________, and ____________________.

A

The mesencephalic locomotor region is important for gait initiation, modulation, and termination.

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32
Q

Supraspinal input from the basal ganglia is important for which aspect of movement?

A

Initiating and stopping movement.

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33
Q

Supraspinal input from the sensory and motor cortices is important for which aspect(s) of movement?

A

Complex tasks that require more sensorimotor activation

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34
Q

Supraspinal input from the cerebellum is important for which aspect(s) of movement?

A

Timing of muscle activation and fine-tuning movement, postural control.

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35
Q

Explain the role of interneurons in central pattern generators during stance phase:

A

Neuron activates extension lower motor neurons, collaterals extend to another neuron (interneuron) sending an inhibitory signal to the neuron that activates flexor lower motor neurons.

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36
Q

During stance, which components are active?

A

Muscle spindles, Golgi tendon organs, and touch and pressure receptors are active and they provide feedback.

The Golgi tendon organ and muscle spindles also facilitate the extensor lower motor neurons>

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37
Q

Central pattern generators do not adapt to the task and environment, true or false?

A

False, central pattern generators are constantly adapting to the task and the environment.

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38
Q

Central pattern generators can be modulated by sensory feedback, where does this feedback come from?

A

Golgi tendon organs, muscle spindles, and exterorecpetive (optic, vestibular and cutaneous) receptors.

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39
Q

Body weight supported treadmill training has been shown to increase walking ___________ and ___________________; although, no improvements are seen among those who are not walking independently at the start of treatment.

A

Walking speed and walking endurance.

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40
Q

Explain dual task paradigms

A

The concurrent performance of two tasks that can be performed independently, measured separately, and have distinct goals

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41
Q

Dual tasking predicts ___________ in older adults.

A

Dual tasking predicts falls in older adults.

42
Q

Name some general changes in gait with age:

A

Shortened stride, wider stance, decreased velocity, increased variability, increased stance and double support time.

43
Q

Name some deviations in gait commonly observed in neurological conditions:

A
  • Knee hyperextension is stance phase
  • Poor heel strike
  • Ataxic gait (wide base of support, unsteady)
  • Hemiparetic gait (slow, wide base of support, hip circumduction)
  • Festinating and freezing gait
  • Difficulty with dual tasking
44
Q

There is a relationship between gait speed and ____________ function.

A

There is a relationship between gait speed and cognitive function.

45
Q

Movement-Basal ganglia do no have direct synapses with lower motor neurons or local circuits, true or false?

A

True, they do not synapse directly.

46
Q

Movement-basal ganglia regulate the activity of ___________________.

A

Movement-basal ganglia regulate the activity of upper motor neuron pathways.

47
Q

Which steps for movement do basal ganglia fall in-between?

1) Intention
2) Planning
3) Programming and execution

A

2 and 3

(Turn motor programs off/on)

48
Q

The basal ganglia consists of five pairs of nuclei, what are they?

A
  1. Caudate nucleus
  2. Putamen
  3. Globus pallidus
  4. Substantia nigra
  5. Subthalamic nucleus
49
Q

The ___________________, are a group of subcortical structures found deep within the white matter of the brain. They form a part of the extrapyramidal motor system and work in tandem with the pyramidal and limbic systems.

A

The basal ganglia (or basal nuclei)

50
Q

The basal ganglia consist of five pairs of nuclei: caudate nucleus, putamen, globus pallidus, subthalamic nucleus, and substantia nigra. These nuclei are grouped into broader clusters, what are they?

A

Striatum: caudate and putamen
Globus pallidus: internal and external segments
Subthalamic nucleus

51
Q

What are the major inputs to the basal ganglia from the cerebral cortex? (3)

A

Glutamatergic (excitatory) inputs from:
- Frontal association area
- Parietal association area
- Supplementary motor area

52
Q

The secondary input to the basal ganglia comes from the ______________________ via the _______________________pathway.

A

The secondary input to the basal ganglia comes from the substantia nigra (pars compacta) via the dopaminergic pathway.

53
Q

Almost all inputs to the basal ganglia synapse with the _______________.

A

Striatum

54
Q

There are two parts of the globus pallidus, what are they?

A

Globus pallidus external

Globus pallidus internal

55
Q

There are two parts of the globus pallidus, what are they and what makes them different?

A

Globus pallidus internal: direct pathway

Globus pallidus external: Indirect pathway

56
Q

The major outputs of the basal ganglia are from the:
1)
2)

A

1) Globus pallidus internal
2) Substantia nigra par reticulata

57
Q

The main output pathways of the basal ganglia are ___________________ (excitatory or inhibitory?)

A

The main output pathways of the basal ganglia are inhibitory.

58
Q

The striatum is always excitatory, true or false?

A

False, the striatum is always inhibitory.

59
Q

The main targets of basal ganglia output include: (3)

A
  • Thalamus
  • Reticular formation
  • Superior colliculus
60
Q

What part of the basal ganglia is known to “hog” inputs?

A

The putamen

61
Q

At rest, how does the basal ganglia inhibit upper motor neurons?

A

At rest, the globus pallidus inhibits the thalamus which in turn inhibits upper motor neuron activity.

62
Q

To initiate movement (disinhibit the upper motor neurons) the cortex sends excitatory inputs to the __________________.

A

Striatum

63
Q

How does the striatum play a role in initiating movement (disinhibiting the upper motor neurons)?

A

The striatum inhibits the globus pallidus, when the globus pallidus is inhibited itself, it is unable to inhibit the thalamus (which keeps movements at rest)

Disinhibition of thalamus = excitation of thalamus

The thalamus can then reach threshold from other excitatory inputs causing the excitation of upper motor neurons for movement.

64
Q

There are two basal ganglia pathways, what are they?
1)
2)

A

1) Direct/Go pathway
2) Indirect/Stop pathway

65
Q

Explain the two basal ganglia pathways (in general terms):

A

1) Direct/Go pathway
- Initiation of movement
- Striatum
- Globus pallidus internal

2) Indirect/Stop pathway
- Inhibition of movement
- Globus pallidus external
- Subthalamic nucleus

66
Q

Explain the direct basal ganglia pathway:

A

At rest, the globus pallidus internal inhibits the thalamus.

When initiating movement, the cerebral cortex sends movement information to the striatum, the striatum then inhibits the globus pallidus internal.

As a result the thalamus is less inhibited (disinhibition), and able to communicate with the cortex to initiate movement.

67
Q

If the globus pallidus external inhibits the subthalamic nucleus, what occurs?

A

movement does not occur

68
Q

Explain the indirect basal ganglia pathway:

A

During movement suppression:

The cortex stimulates the striatum.

Striatum inhibits the globus pallidus external, so it is unable to inhibit the subthalamic nucleus.

Subthalamic nucleus is activated by cortex (hyper-direct pathway), stimulates Globus pallidus internal, which inhibits the thalamus.

69
Q

The indirect pathway ______________ the direct pathway.

A

The indirect (stop) pathway antagonizes the direct (go) pathway.

70
Q

Activation of intended and focused motor programs is completed via the _________ pathway.

A

The direct/go basal ganglia pathway.

71
Q

Broad suppression of competing motor programs is completed via the ______________ pathway.

A

The indirect/stop pathway.

72
Q

Which part if the basal ganglia modulates the activity of both direct and indirect pathways through dopamine release (dopaminergic pathway)?

A

The substantia nigra pars compacta

73
Q

Explain the dopaminergic effect on the striatum:

A

Dopamine receptor 1 (D-1) makes the direct pathway more active (less inhibition of the thalamus) = movement

Dopamine receptor 2 (D-2) makes the indirect pathway less active (less inhibition of the thalamus) = movement

The net effect of D-1 and D-2 = excitation of the thalamus = increased output to the cortex

74
Q

Dopamine-1 receptors affect which pathway, what about Dopamine-2?

A

D-1 = direct pathway (more active)
D-2 = indirect pathway (less active)

75
Q

The effects of dopamine on the striatum are ___________________, meaning the increased excitation to the cortex in the direct and indirect pathways occurs in concert with selection of a movement.

A

The effects of dopamine on the striatum are transient, meaning the increased excitation to the cortex in the direct and indirect pathway occurs in concert with selection of a movement.

76
Q

The basal ganglia form a motor loop with the _____________ in the same cerebral hemisphere.

A

The basal ganglia form a motor loop with the motor cortex in the same cerebral hemisphere.

77
Q

The prefrontal loop is involved in…

A

The prefrontal loop is involved in initiation and termination of cognitive processes.

78
Q

The limbic loop is involved in…

A

The regulation of emotional and motivated behavior.

Transitions from one mood state to another.

79
Q

Basal ganglia lesions or damage typically result in impairments to the ________________ side of the body.

A

Basal ganglia lesions or damage typically result in impairments to the contralateral (opposite) side of the body.

80
Q

The striatum is made up of the __________ and ______________.

A

Striatum: caudate and putamen

81
Q

What is the cause of Huntington’s disease (in simple terms)?

A

Selective atrophy of the striatum (caudate and putamen).

82
Q

In Huntington’s disease, there is progressive degeneration of _____________ neurons, and the _________________ pathway is affected first.

A

In Huntington’s disease, there is progressive degeneration of striatal neurons (caudate and putamen), and the indirect pathway is affected first.

83
Q

How does Huntington’s disease affect the indirect pathway?

A

Huntington’s disease causes the denegation of striatal neurons (caudate and putamen).

Therefore, there is less inhibition of the Globus pallidus external from the striatum.

The subthalamic nucleus and Globus pallidus internal are inhibited (globus pallidus external is disinhibited so the inhibitory signal it sends is uninterrupted).

As a result, there is less tonic inhibition of the thalamus.

Causing increased movements (hyperkinesia).

84
Q

Hemiballismus is a hyperkinetic disorder caused by…

A

A lesion affecting the subthalamic nucleus (e.g., stoke).

85
Q

What are the symptoms of hemiballismus?

A

Involuntary ballistic flinging of the arm or leg (contralateral to the damage).

86
Q

In hemiballismus disorder, involuntary ballistic flinging of the arm or leg is observed on the _________________side to the damage.

A

Contralateral (opposite) side to the damage.

87
Q

In general terms, what is the cause of hemiballismus disorder (what occurs in the pathway)?

A

Due to damage of the subthalamic nucleus which plays a role in causing the globus pallidus internal to inhibit the thalamus (activates the inhibition of the globus pallidus internal).

As a result, there is decreased inhibition to the thalamus, causing hyperkinesia.

88
Q

Parkinson’s disease is a hyperkinetic disorder, true or false?

A

False, Parkinson’s is a hypokinetic disorder.

89
Q

In general terms, what is the cause of Parkinson’s disease?

A

Progressive degeneration of dopaminergic neurons in substantia nigra pars compacta.

90
Q

What are the symptoms of Parkinson’s? (Hint: use a mnemonic)

A

T: Tremor
R: Rigidity
A: Akinesia
P: Postural (stooped)

91
Q

Explain how Parkinson’s disease affects the basal ganglia direct pathway:

A

There is less dopamine-1 receptor (D-1) facilitation (from the substantia pars compacta).

(D-1 facilitation causes disinhibition of the striatum (caudate and putamen). This affect does not occur however, due to degeneration.)

As a result, there is an increase in inhibitory output to the thalamus.

= Less movement

92
Q

In Parkinson’s disease only the direct pathway is affected, true or false?

A

False, in Parkinson’s disease both pathways are affected.

93
Q

In Parkinson’s disease only the indirect pathway is affected, true or false?

A

False, in Parkinson’s disease both pathways are affected.

94
Q

Explain how Parkinson’s disease affects the basal ganglia indirect pathway:

A

There is less dopamine-2 receptor (D-2) facilitation (from the substantia pars compacta).

(D-2 facilitation causes inhibition of the striatum (caudate and putamen). This affect does not occur however, due to degeneration.)

This means there is a decrease in the activity of the Globus pallidus external (less inhibition), and increased activity of the subthalamic nucleus, causing excessive inhibition of the thalamus.

95
Q

The net-effect of dopamine loss = inhibition of the _________________.

A

The net-effect of dopamine loss = inhibition of the thalamus, resulting in decreased cortical excitability.

96
Q

Can dopamine cross the blood-brain barrier?

A

No

97
Q

Explain Parkinson’s disease treatment (oral administration of L-DOPA)

A

L-DOPA (levodopa) is a dopamine precursor that can cross the blood-brain barrier.

The conversion to dopamine occurs in the dopaminergic neurons.

This treatment does NOT treat the disease itself, it treats the symptoms, and over-time it loses effectiveness.

98
Q

L-DOPA used for treatment of Parkinson’s is successful in relieving symptoms associated with the disease, through decreasing/reversing degeneration of the dopamine receptors, true or false?

A

False, L-DOPA does not treat the degeneration itself, it works to alleviate some of the symptoms.

99
Q

The effects of L-DOPA in Parkinson’s disease can fluctuate, explain:

A

Dyskinesia (involuntary movements may occur), the effects may begin to diminish leading to a predictable decline in function. Additionally, there are unpredictable changes in motor function (on-off fluctuations).

100
Q

Deep brain stimulation can be used to treat Parkinson’s disease, explain this treatment option:

A

An electrode (thin insulated wire) is inserted into the brain, an extension (insulated wire) goes from the electrode to implantable pulse generator, this impulse generator (battery pack) is typically implanted under the skin of the collarbone.

The stimulation is used to modulate/disrupt atypical patterns of neural activity in the brain.

The targets of stimulation include the Globus pallidus internal and the subthalamic nuclei.

101
Q

The motor function of the basal ganglia is to _____________ and ____________________.

A

The motor function of the basal ganglia is to initiate movements and suppress unwanted movements.

102
Q

Huntington’s disease affects the ________________ pathway; whereas Parkinson’s disease affects the ______________________.

A

Huntington’s: Indirect pathway (stop/hyperkinesia)

Parkinson’s: Both pathways (stop and go/hypokinesia)

Neuroanatomy (OCCU 6140) (20 decks)

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