Suprasegmental Motor Control I
Terms
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- What is required for successful movement?
- 1. feedback, 2. control of muscle contraction, 3. coordination of muscle activity, 4. motor system should calibrate based on learning
- What are the actions of the motor system?
-
Basic reflex
Central reflex
Voluntary movements - How does the nervous system perform motor actions?
- Feedback and Feed-forward
- What is feedback used for?
- Slow movements and to maintain posture.
- What is feedforward used for?
- to perform anticipatory actions and allows for rapid movements
- what are the three levels of suprasegmental control?
- The spinal cord, brainstem, and forebrain
- where are motoneurons controlling axial muscles?
- In the ventromedial horn
- Which two tracts innervate primarily medial motor neurons?
- Reticulospinal and Vestibulospinal tracts
- Which spinal tract innvervates primarily lateral motor neurons in animals?
- The rubrospinal tract (from the red nucleus to the spinal cord)
- What has replaced the rubrospinal tract in humans?
- the corticospinal tract
- Neurons in the ___________ give rise to the ventral corticospinal pathway and innvervate primarily medial neurons in the spinal cord bilaterally, as well as neurons in the reticular and vestibular nuclei
- Premotor cortex and neck and trunk regions
- The lateral corticospinal tract originates where?
- In the primary motor cortex, as well as from somatosensory cortices.
- Three quarters of the axons (in humans) cross the midline in the _____.
- Pyramidal decussation
- Lesions of the suprasegmental motor system produces what symptoms?
- Weakness, loss of voluntary strength, slowing of musclar contraction and loss of fractionation.
- What are the characteristics of spasticity?
- Increased muscle tone, hyperactive stretch reflexes, and clonus (oscillatory muscle responses to muscle stretching).
- Where is spasticity more marked?
- In antigravity muscles
- Describe decerebrate rigidity.
- Condition in which there is increased muscle tone in the extensors of the arms and legs. (Loss of descending inhibition)
- What reduces spasticity and what does this suggest?
- lesioning the dorsal root afferents reduces spasticity and this suggests that it results from an increased gain in the spinal reflexes
- Give the example used to describe the production of reflexes that are normally suppressed.
- Babinski reflex
- What is the result of lesions that involve pathways that control upper limb muscles?
- Loss of the ability to control fine finger movements.
- In Parkinson's disease, why are the reflexes not affected?
- Becauses the disease affects a extrapyramidal motor system (the basal ganglia in this case), so the corticospinal tract is not involved.
- What are the three classes of sensory inputs for postural responses?
- Proprioceptors, vestibular receptors, and anticipatory postural reflexes
- Transection where can produce decerebrate rigidity?
- Above the vestibular nuceli and below the red nucleus
- Walking movements :
- 1. are generated in the spine, 2. do not require suprasegmental inputs, 3. do not require sensory input, but 4. can have individual component movemets that are graded by afferent inputs.
- Name the region of the brain that will stimulate walking on a treadmill
- Mesencephalon Locomotor Region (MLR)
- How does visual information affect locomotion?
- It affects it by modulating the output of the motor cortex.
- What is the fundamental influence driving locomotion?
- A type of nueronal circuit called a central pattern generator.
- Where are the central pattern generating neurons thought to reside?
- In the intermediate gray matter of the spinal cord.