8.8. Supraspinal regulation of muscle functions. Postural reflexes. Flashcards
I. Supraspinal motor control
1. What are the features of Supraspinal motor control?
- Supraspinal motor control is based in the medulla, midbrain, cerebellum + basal ganglia and the motor cortex
- The movement can be conscious (lateral pathways) or unconscious (medial pathways).
***Pyramidal + extrapyramidal system terminology is not used here.
II. Major pathways connecting the brainstem and cortex with the spinal cord
1. What are the 2 Major pathways connecting the brainstem and cortex with the spinal cord?
- Lateral pathways: in the lateral funiculus of the spinal cord. Control conscious manipulation and movement coordination
- Medial pathways: in the ventral funiculus of the spinal cord. Deals more with postural reflexes via axial muscles, coordination etc.
II. Major pathways connecting the brainstem and cortex with the spinal cord
2. What are the location and function of lateral pathways?
- in the lateral funiculus of the spinal cord.
- Control conscious manipulation and movement coordination
II. Major pathways connecting the brainstem and cortex with the spinal cord - lateral pathways
3A. What are the 3 main lateral pathways?
- Lateral corticospinal tract (80%)
- Rubrospinal tract
- Lateral corticobulbar tract
II. Major pathways connecting the brainstem and cortex with the spinal cord - lateral pathways
3B. What are the features of Lateral corticospinal tract (80%)?
- pyramidal decussation.
- Can have direct or indirect synapse with an α-motor neuron, unique to humans/chimps
II. Major pathways connecting the brainstem and cortex with the spinal cord - lateral pathways
3C. What are the features of Rubrospinal tract?
- From red nucleus to the spinal cord.
- Innervates neck muscles + (some) large arm muscles -> flexor reflexes in upper limb
II. Major pathways connecting the brainstem and cortex with the spinal cord - lateral pathways
3D. What are the features of Lateral corticobulbar tract
Lateral corticobulbar tract: innervates lower face + tongue
II. Major pathways connecting the brainstem and cortex with the spinal cord
4A. What are the feature and location of medial pathways?
- In the ventral funiculus of the spinal cord.
- Deals more with postural reflexes via axial muscles, coordination etc.
II. Major pathways connecting the brainstem and cortex with the spinal cord - medial pathways
5A. What are the 6 main medial pathways?
II. Major pathways connecting the brainstem and cortex with the spinal cord - medial pathways
5B. What are the features of anterior corticospinal tract?
- Corticospinal tract (20%)
- Uncrossed.
- Innervates medially located muscles (activatebilaterally)
II. Major pathways connecting the brainstem and cortex with the spinal cord - medial pathways
5C. What are the features of Vestibulospinal tract?
- Lateral part gets afferentation from semicircular organs
- medial part gets afferentation from otoliths + SC organs
II. Major pathways connecting the brainstem and cortex with the spinal cord - medial pathways
5D. What are the features of Vestibulospinal tract?
mostly excitatory
II. Major pathways connecting the brainstem and cortex with the spinal cord - medial pathways
5E. What are the features of Medullary-reticulospinal tract?
mostly inhibitory
II. Major pathways connecting the brainstem and cortex with the spinal cord - medial pathways
5F. What are the features of Tectospinal tract?
- From superior colliculus to spinal cord.
- Vision + sound stimulus
II. Major pathways connecting the brainstem and cortex with the spinal cord - Reticular and vestibular nuclei in the brainstem
6. What are the main features of Reticular and vestibular nuclei in the brainstem?
- There are several nuclei in the brainstem which can affect the movement of our body
- The brainstem likes to excite motor neurons + interneurons -> get rigidity in the musculature
II. Major pathways connecting the brainstem and cortex with the spinal cord - Reticular and vestibular nuclei in the brainstem
7. What are the features of excitatory nuclei?
- Excitatory: vestibular, pontine reticular nuclei
- Excite neck muscles, axial muscles (which maintain
posture/balance), anti-gravity muscles, eye movements
II. Major pathways connecting the brainstem and cortex with the spinal cord - Reticular and vestibular nuclei in the brainstem
8. What are the features of Inhibitory nuclei?
- Inhibitory: cortex, red nucleus, medial reticular formation
- These ‘’higher center’’ like to limit the exaggerated rigidity caused by the brainstem
- If there is no action from the higher centers, the midbrain would like to increase the overall muscle tone
III. Postural reflexes
1. What are of Postural reflexes?
Postural reflexes (controlled by the brainstem) are automatic movements that control the equilibration we require once upright and moving with the effects of gravity.
III. Postural reflexes
2. What is the role of postural reflex?
- They maintain posture, balance and fluidity of movement
III. Postural reflexes
3. What is the localization of postural reflex?
The localization of these postural reflexes can be visualized with decerebration and decortication which is the separation/cutting of the brainstem from the cortex either at the level of ponto- medullary junction or above the red nucleus (these reflexes also occur with brain injury/lesions)
IV. Decerebration
1. What are the features of Decerebration?
- red nucleus is not included
- The higher centers (cortex, red nucleus, cerebellum) are not able to reduce the overall excitatory effect of the midbrain -> can see the ↑ rigidity in the body:
IV. Decerebration
2. Name of the reflex you can observe in Decerebration?
Tonic labyrinth reflex
IV. Decerebration
3. Describe Tonic labyrinth reflex
- red nucleus is not included
- The higher centers (cortex, red nucleus, cerebellum) are not able to reduce the overall excitatory effect of the midbrain -> can see the ↑ rigidity in the body:
V. Decortication
1. What are the features of Decortication?
V. Decortication
2. What are the reflexes of Decortication?
VI. Cerebral cortex
1. What is Motor cortex?
- Motor cortex (precentral gyrus) is the center of voluntary movements, as well as the motivation and planning associated with these movements.
- This area also regulates muscle tone and movements that need precise sensory-motor coordination.
VI. Cerebral cortex
2. What are subdivisions of motor cortex?
This functional area is divided into:
- Primary motor cortex – Brodmann 4
- Premotor cortex + supplementary motor area –
Brodmann 6
- Frontal eye movement area – Brodmann area 8
VI. Cerebral cortex -Steps in order of motor activity
3A. What are the steps in order of motor activity?
- Regulates the muscle tone (↓rigidity)
- Realization, planning, execution of voluntary movements
- Special movements found in cerebral cortex
- Cortical postural reflexes
- Regulation of movements requiring very precise sensory motor coordination
VI. Cerebral cortex -Steps in order of motor activity
3B. What happen in step 1: Regulates the muscle tone (↓rigidity)?
- Cortex would like to suppress the midbrain-originated rigidity (vestibular + pontine
reticular nuclei) - Extensors inhibited + flexors stimulated
VI. Cerebral cortex -Steps in order of motor activity
3C1. What happen in step 2: Realization, planning, execution of voluntary movements?
VI. Cerebral cortex -Steps in order of motor activity - step 2: Realization, planning, execution of voluntary movements
3C2. How does activation of functional areas occur?
Association areas (800ms prior to movement)
=> supplementary motor area (500ms prior)
=> premotor area (5ms prior)
=> primary motor cortex activated (0ms)
VI. Cerebral cortex -Steps in order of motor activity - step 2: Realization, planning, execution of voluntary movements
3C3. What happen after Activation of premotor cortex?
It will activate descending motor pathways via
medial pathways (ant.cs.tract)
VI. Cerebral cortex -Steps in order of motor activity - step 2: Realization, planning, execution of voluntary movements
3C4. What happen if we conduct any voluntary movement?
- body posture stabilized using the medial pathways – anterior corticospinal tract
- after few ms, the laterally located muscles which contribute to the movement will be activated by the lateral corticospinal tract => execute movement
VI. Cerebral cortex - Steps in order of motor activity - step 3: Special movements found in cerebral cortex
3D. What happen in step 3: Special movements found in cerebral cortex?
Some cortical areas are specialized to execute
special movements (eye, hand skills, hand rotation etc.)
VI. Cerebral cortex - Steps in order of motor activity - step 4. Cortical postural reflexes
3E1. What are the 3 reflexes found in step 4. Cortical postural reflexes?
- Optical righting reflex
- Placing reflex
- Hopping reflex
VI. Cerebral cortex - Steps in order of motor activity - step 4. Cortical postural reflexes
3E2. What is the feature of Optical righting reflex?
According to many different
visual sensations, we are able to correct our body
position
VI. Cerebral cortex - Steps in order of motor activity - step 4. Cortical postural reflexes
3E3. What is the feature of Placing reflex?
Placing reflex: causes the ‘’stepping on stair’’-like movement
VI. Cerebral cortex - Steps in order of motor activity - step 4. Cortical postural reflexes
3E4. What is the feature of Hopping reflex?
if we push someone to the side
=> they will have a jumping-like movement to keep the balance
VI. Cerebral cortex -Steps in order of motor activity
3F. What happen in step 5 “Regulation of movements requiring very precise sensory motor coordination”
- We can have colliding information from an object in various situations
=> example: to touch an object behind a prism (prism changes pictures of the object = difficult to touch) - conflicting information from visual system and different information from proprioceptors from hand
- But the cortex should be able to realize how to solve this eventually
