Final Exam Flashcards
What does the motor cortex consist of?
- Primary motor cortex
- Premotor area
- Supplemental motor area
The Primary motor cortex has a __________ arrangement
Somatotropic
Greater than half of the primary motor cortex controls ___________
Hands & speech
Stimulating the primary motor cortex stimulates ____________ instead of ____________
- movements
- contracting a single muscle
The ___________ area is the anterior and lateral portions of the primary motor area
Premotor
The premotor area projects to the _____________ and ___________
- Primary motor cortex
- Basal ganglia
The supplemental area is superior to the premotor area and mainly lies in the _____________
Longitudinal fissure
What do the premotor and supplemental motor areas function in concert to do?
- Attitudinal movements
- Fixation movements
- Positional movements of head and eyes
- Background for finer motor control of arms/hands
The ____________ tract descends via the posterior limb of the internal capsule (lies between caudate and putamen)
Corticospinal
What does the corticospinal tract form?
Pyramids of the medulla
What do the corticospinal tract fibers do?
- Some fibers cross midline & form the lateral corticospinal tract
- Some fibers stay ipsilateral & form the ventral corticospinal tract
What is spinal preparation?
- All tracts cut, cord completely isolated from brain
- Flaccidity (floppy paralysis)
What is decerebrate preparation?
- Transection at mid collicular level
- Decerebrate rigidity (extensors tonically hyperactive)
What is decorticate preparation?
- Destruction of the cerebral cortex
- Decorticate spaciticity
- Upper areas of reticular formation no longer under inhibitory cortical influence, therefore tonic excitation occurs
What is decorticate spasticity?
- Removal or lesion of cerebral cortex
- Seen in humans of the hemiplegic side after stroke
- 60% of intracerebral hemorrhages
What does decorticate spasticity cause?
- Loss of cortical inhibition of gamma efferent discharge mediated nu the medullary reticular formation
- Small arteries in the internal capsule are prone to rupture or thrombosis
What is decerebration?
- An experimental procedure useful for the study of reflexes
- Transection of midbrain often at intercollicular level
- Loss of sensation
What does decerebration alter?
- Motor control
- cortical descending pathways are interrupted
- brain stem control remains intact
What specific effects does decerebration have?
- Activity in some descending pathways: hyperactive
- Flexion reflexes: suppressed
- Stretch reflexes: exaggerated (selective excitation of gamma motor neurons)
What does decerebration lead to?
Decerebrate rigidity
What can happen with a spinal cord transection?
Spinal shock
What specifically occurs with spinal shock?
- Initially all cord functions, including spinal reflexes, are depressed (lack on tonic excitation from higher centers)
- Spinal cord neurons gradually regains excitability (days/weeks)
- Some spinal cord reflexes become hyperactive
- Eventually results in a mass reflex
What is a mass reflex?
- Spinal cord becomes excessively active
- Causes flexor spasms and evacuation of bladder & colon
What generally occurs with spinal shock?
- Arterial blood pressure falls dramatically
- All skeletal muscle reflexes integrated in the cord are blocked
- Sacral reflexes for control of bladder and colon evacuation are suppressed
What are the names of the reticular nuclei?
- Pontine reticular nuclei
- Medullary reticular nuclei
The pontine reticular nuclei transmit _______ signals via the ________________tract
- Excitatory
- Pontine (medial) reticulospinal
The pontine reticular nuclei stimulate the ______________
Axial trunk and extensor muscles (which support the body against gravity)
The pontine reticular nuclei receive stimulation from the _________ & _________
- Vestibular nuclei
- Deep nuclei of the cerebellum
The pontine reticular nuclei have a high degree of ___________
Natural excitability
The medullary reticular nuclei transmit ________ signals via the ___________ tract
- Inhibitory
- Medullary (lateral) reticulospinal tract
The medullary reticular nuclei inhibit the ___________
Axial trunk and extensor muscles (which support the body against gravity)
The medullary reticular nuclei receive strong input from the ________
- Cortex
- Red nucleus
- Other motor pathways
The medullary reticular nuclei allows___________________
Tone to be increased or decreased (depending on function needing to be performed)
Summarize the ventral corticospinal tract
- Descending pathway
- Ipsilateral
- Medial motor system
- Controls mainly axial and girdle muscles
Summarize the Reticulospinal tracts
- Consists of the Pontine & Medullary reticualr formations
- Descending pathway
- Ipsilateral
- Medial motor system
- Controls mainly axial and girdle muscles
Summarize the Vestibulospinal tracts
- Origin from lateral vestibular nucleus to mainly extensors
- Descending pathway
- Ipsilateral
- Medial motor system
- Controls mainly axial and girdle muscles
Summarize the Lateral Corticospinal tract
- Descending pathway
- Contralateral
- Lateral motor system
- Controls more distal muscles of limbs
Summarize the Rubrospinal tract
- Innervates mainly flexors
- Descending pathway
- Contralateral
- Lateral motor system
- Controls more distal muscles of limbs
Summarize the Tectospinal tract
- Innervates cervical musculature only
- Superior colliculus- orienting reactions
- Descending pathway
- Contralateral
- Medical motor system
The primary motor cortex has a _______________ arrangement
Vertical columnar
The primary motor cortex functions as an _______________
- Integrative processing system
- Stimulation of 50-100 pyramidal cells to achieve muscle contraction
What are the two types of output for pyramidal cells?
- Dynamic signals
- Static signals
What do dynamic signals do?
Excessively excited at the onset of contraction to initial muscle contraction
What do static signals do?
Fire at a slower rate to maintain contraction
What are the phases of voluntary movement?
- Planning & programming phase
2. Execution phase
What are the steps involved in voluntary movement?
- Signals for movement originate in the sensory association cortex
- Go directly or indirectly via Basal ganglia & Ceerebrocerebellum
- Go to primary motor cortex
4a. Go to spinal cord
4b. Go to spinocerebellum
* Feedback from periphery goes to spinocerebellum and then to primary motor cortex
What is electromyography (EMG)?
- The electrical activity within an accessible muscle can be recored via insertion of a needle electrode into it
- Patterns of activity at rest and during contraction have been characterized under normal and abnormal conditions
