L19 Motor Control by the CNS Flashcards Preview

Physiology > L19 Motor Control by the CNS > Flashcards

Flashcards in L19 Motor Control by the CNS Deck (25):
1

Hierarchy of Integration 

What are the structures involved in and the functions of

  1. The Spinal Level
  2. The Subcortical Level
  3. The Cortical Level

 

  1. the spinal cord
  2. sends information down the spinal cord by medial and ventral pathways that are phylogenetically old (evolved early), control proximal limb musculature and are chiefly responsible for automatic control.  Correspondingly the medial portion of the cerebellum is also thought to underlie posture control and basic movement correction
  3. sends information down the spinal cord in lateral and dorsal tracts that are phylogenetically new, control distal limb musculature and are responsible for skilled movement.  Similarly the lateral cerebellum (sometimes called cerebrocerebellum) initiates skilled and sophisticated movements. 

2

Hierarchy of Integration 

  1. What happens as we go laterally to dorsally in the spinal cord?
  2. Where do the newer tracts tend to decussate?
  3. Where do the older posture maintenance and crude sensation tracts decussate?

  1. the newness of the tracts evolution and the level of sophistication increases
  2. higher
  3. At the level at which the nerves enter or leave the spinal cord

3

  1. Who was able to produce a map of the movement areas of the brain, what we currently term the primary motor cortex (area M1)?
  2. Who expanded the work?
  3. What did he do?
  4. What did this give rise to?

  1. Sherrington
  2. Penfield
  3. He had developed the Montreal procedure for treating severe epilepsy by ablating areas of the cortex from which seizures originated.  While the patients brain was exposed (they were only under local anaesthetic!) he was able to stimulate the motor and sensory areas of the brain and thus characterise what areas were mapped to what areas of the body
  4. The sensory homunculus in the POST central gyrus and the motor homunculus in the PRE central gyrus

A image thumb
4

  1. Where is the sensory homunculus?
  2. Where is the motor homunculus?
  3. Why do the areas requiring fine control (lips, phonatory structures, hands) occupy over 50% of the area?

  1.  POST central gyrus
  2. PRE central gyrus
  3. a large amount of nerves are necessary to provide that degree of control.

5

Motor Cortex and Associated Areas

  1. Name the two main areas in the cortex that feed into the motor area and effect control over muscles?
  2. What do they do?
  3. Name other areas that feed into the motor area that are involved in control of movement
  4. What does the motor cortex represent?

  1. Premotor Cortex and Supplementary Motor Areas
  2. Premotor cortex - thought to set a posture appropriate for movement, aids in selecting movement
    1. Supplementary Motor - involved in integrating complex, planned patterns of movement

3. 

  • Primary Somatosensory Map of the Body - mainly proprioceptive
  • Posterior Parietal - associations
  • Cortex
  • Thalamus - tactile signs, joint and muscle signals, signals from cerebellum
  • Basal Ganglia
  • Cerebellum serving vision and hearing 
  • Some collaterals from the opposite cortex

4.  a library of movements (not a library of muscles)

6

​Corticospinal Tracts

  1. What are these?
  2. Where do 80% of these travel from?
  3. After they decussate, where do they travel?
  4. What do they innervate?
  5. What are the other 20%?
  6. Where do they decussate?
  7. What  do they act in by their innervation?

  1. the main descending tracts responsible for motor control 
  2. 80% of these travel from the cortex to the pyramids in the medulla where they decussate, hence why they are often called pyramidal tracts
  3. They then travel down via the lateral corticospinal (pyramidal) tracts
  4. tracts to innervate distal muscles responsible for fine control
  5. ventral corticospinal tracts 
  6. not until they leave the spinal cord 
  7. bilateral postural movements - responsible for posture

A image thumb
7

  1. What do motor neurons innervating the face travel by?

  1. Corticobulbar tracts

8

Where do the pyramidal neurons come from?

  • 30% from primary motor cortex
  • 30% from premotor and supplementary motor areas
  • 40% from parietal association area and the primary somatosensory area

9

What happens the more medially you go in the spinal cord?

The older and less sophisticated the reflexes and pathways get

10

Other Brain Stem Pathways

Rubrospinal Tracts

  1. Where do they originate?
  2. Where does the info come from?
  3. Where do they cross over?
  4. What do the signals pass down?
  5. What do they innervate?
  6. What are they responsible for?

Q image thumb

  1. In the RED nucleus of the MIDBRAIN
  2. Motor cortex and cerebellum through red nucleus 
  3. The midline
  4. LATERAL corticospinal tract
  5. innervate distal musculature, sets baseline posture
  6. control and modulation of the walking Central Pattern Generators in the spinal cord

You could think of them as an alternative pathway for transmitting cortical and cerebellar signals to the spinal cord. (UMN Lesions)

A image thumb
11

Other Brain Stem Pathways (Extrapyramidal)

Pontine and Medullary Reticulospinal Tracts

  1. Which is exitatory?
  2. Which is inhibitory?
  3. Where do they originate?
  4. Where do they recieve connections from?
  5. Where do they innervate?
  6. How are their actions mediated?

  1. Pontine
  2. Medullary
  3. In the reticular nuclei of the medulla
  4. the motor cortex and cerebellum
  5. innervate anti-gravity muscles via the reticulospinal tracts, to help maintain an upright posture in standing.
  6. partially by input to the gamma motor system (γ efferents to muscle spindles)

A image thumb
12

Other Brainstem Pathways (Extrapyramidal)

Vestibulospinal Tracts

  1. Where do they originate?
  2. Where do they travel?
  3. What do they innervate?

  1. The vestibular nuclei of the medulla
  2. Travel ventrally in the spinal cord
  3. innervate neck and antigravity muscles

A image thumb
13

Other Brainstem Pathways (Extrapyramidal)

Tectospinal Tract

  1. Where does it originate?
  2. What does it act to do?

 

  1. in the superior colliculus of the midbrain
  2. control eye movements

14

Final Common Path

Why is the lower motor neuron is often referred to as the final common path from upper motor neurons?

the neuron which eventually innervates a motor unit (shown in blue) recieves input from many other neurons, either from posture maintenance tracts, or from movement controlling tracts, often via interneurons. 

A image thumb
15

UMN Lesions

  1. Give examples
  2. How did Sherrington enable an understanding of the location of integration of various movements?
  3. What is a classical example and how is it pathological

  1. stroke and Brown-Sequard syndrome
  2. Experimental upper motor neuron lesions were originally performed on cats, by performing surgical sections at different levels of the brain and midbrain.  
  3. Cerebral Stroke - decorticating the patient 

    This removes the higher control over the midbrain reflexes and causes the characteristic signs of stroke (hyperactive stretch reflexes, Spastic rigidity of flexors in upper limbs and extensors in lower limbs and the positive Babinski sign.  These primitive survival reflexes are not evident in the healthy human with intact Upper Motor Neurons  as higher order reflexes override them.

     

A image thumb
16

Basal Ganglia

What are the basal ganglia?

 

 

 

Where do they output to?

Where do they recieve input from

5 interactive and intricately linked structures on each side of the brain

  • caudate nucleus and putamen (collectively called striatum)
  • the globus pallidus (ext. and int. segments)
  • the substantia nigra
  • subthalamic nuclei

They feed their output to the motor and associated areas of the cerebral cortex via the thalamus

 receive input from the cortex (mainly association areas)

A image thumb
17

Basal Ganglia

  1. Where do virtually all motor fibres pass through?
  2. What do the following cause?
    1. Excessive Suppression
    2.  and Excessive Release of pre-programmed movements and behaviours

Q image thumb

  1. the internal capsule, the space between the caudate and globus pallidus
  2.  
    1. Parkinson's disease
    2. Huntingtons chorea, parkinsons disease, tourettes syndrome

18

Basal Ganglia

Putamen Circuit

  1. How is the putamen ciruit arranged?
  2. What does it function in?
  3. What can problems in it give rise to?

  1. A loop = Cortex to  putamen to globus pallidus to substantia nigra and subthalamic nuclei to thalamus back to cortex.
  2. The release of preprogrammed patterns of motor activity 
  3. twisting, bending movements of hands, arms, face or neck (athetosis) Flailing movements of the whole limb (ballismus) and flickering, dance like movements of the hands and face (Chorea)

A image thumb
19

Basal Ganglia

Caudate Circuit

  1. What is it concerned with?
  2. What is the balance between releasing and suppressing movements in both of these circuits maintained by?
  3.  What do problems with the basal ganglia often arise due to?

  1. the cognitive control of motor pattern sequences, ie the subconscious determination of what pattern of movements will achieve a desired goal
  2. An exitatory dopaminergic projection between the substantia nigra and the striatum
  3. hyperactivity or depression of this dopaminergic connection 

A image thumb
20

Outline the the simplifed circuit involving the putamen and caudate circuit

Primary motor cortex

Premotor cortex

Supplementary motor area

Somatosensory cortex

TO

Striatum (= caudate nucleus+putamen)

TO

Globus pallidus (And substantia nigra)

TO

Subthalamic nucleus

Thalamus 

TO START

A image thumb
21

Basal Ganglia 

  1. What do problems with basal ganglia often result in?
  2. How do they often arise?
  3. What happens in Parkinson's Disease?
  4. What happens in Huntington's Disease?
  5. What happens in Tourettes Syndrome?

Q image thumb

  1. either the uncontrolled release (hyperkinesia) or suppression of movements (hypokinesia)
  2. with problems in the dopaminergic pathway between the substantia nigra and the striatum affecting the balance between release and suppression of movements.
  3. the dopaminergic neurons between the SN and the Striatum degenerate resulting in less excitation of the striatum, less inhibition of the GP, and therefore a greater inhibition of the thalamic projection to the cortex. 
    1. gives rise to the hypokinetic aspects of parkinsons, the inability to initiate movements.  The upset in balance also causes hyperkinetic aspects, such as tremor at rest and “lead pipe" (flexible but stiff) or “cog wheel" (only moves like ticking of a clock)
  4. breakdown of cholinergic and gabaergic pathways in the basal ganglia gives rise to release of unintentional movements, (athetosis, ballismus and chorea).
  5. an excess of dopamine, results in the characteristic tics and inappropriate utterances, due to unintentional release of pre programmed behaviours and movements. 

A image thumb
22

Cerebellum

  1. Where does it recieve innervation from?
  2. Where does it feed this information to?
  3. What does it function as?
  4. What can it be divided into?

Q image thumb

  1. cortex, the brain stem and the periphery (proprioception, skin, ear, vestibular apparatus, eyes) 
  2. the cortex, brainstem reticular formation and red nucleus.
  3. a “co processor” of the brain, correcting errors in movement and setting posture against which movement takes place.

4. Vestibulocerebellum (Flocculonodular lobe) - equilibrium and eye movements

Spinocerebellum (Vermis and Intermediate zone) - has a somatotopic map of body zones (going medial-lateral zone, proximal limb-distal limb), comparing what the motor cortex and associated areas want the body to do (efference copy or motor plan) with what its actually doing (from the senses, mainly proprioceptive), and makes appropriate corrections

Cerebrocerebellum (lateral) - Newest phylogenetically. planning and pre programming movements

 

The cerebellum is the seat of skills, and interestingly a second language is controlled from here

 Remember old V new, medial V lateral

23

Cerebellum

  1. What do problems with the cerebellum lead to?
  2. What do problems with the vestibulo and spinocerebellum lead to?
  3. What do problems with the cerebrocerebellum lead to?
  4. What commonly depresses cerebral function?

  1. inaccurate movements and difficulty maintaining a stable posture and visual fixation. Kinaesthetic learning is also disrupted
  2. wide stance, swaying while standing, inappropriate nystagmus, ataxic gait
  3. dysmetric [inaccurate] movements (dysmetira, past pointing), decomposition of movements, intention tremor
  4. Being drunk

24

Outline the 3 regions of the cerebellum and their function?

Vestibulocerebellum (Flocculonodular lobe)

•Equilibrium, eye mvmts

Spinocerebellum (Vermis and Intermediate Zone)

•Recieves efference copy (what the brain wants the body to do)

•Proprioception (what the body is actually doing)

•Makes the 2 the same

Cerebrocerebellum (lateral)

•Planning movements

•Movement accuracy

•Learned skills

25

Summing Up (for general perusal)

•Supraspinal influences from the motor and associated cortex, the basal ganglia and the cerebellum exert final control over the spinal reflexes we considered last week.

•Motor tracts are organised heirarchically with medial tracts serving posture and basic movements with lateral tracts and structures serving precise movement

•The basal ganglia help initiate movements, while the cerebellum acts as a movement co processor for the brain, initiating and correcting it

Decks in Physiology Class (46):