Lateral & Medial Descending pathway & Motor Organisation of Spinal cord Flashcards
What are the tracts located in the Lateral funiculus?
Lat. corticospinal, rubrospinal, lat. Reticulospinal
- Fine voluntary movement, Distal muscles
What are the tracts in the anterior ( medial ) funiculus ?
Vestibulospinal, reticulospinal, medial (anterior) corticospinal, tectospinal.
- Postural and reflex movement, Proximal and axial muscles
Which tracts modify segmental reflex activity?
Supraspinal tracts
Which tract regulates posture and balance and facilitates Aa motor neurons of the postural ( antigravity ) extensor muscles?
Vestibulospinal tract
Which tract originates from the superior colliculus ?
Tectospinal tract
True or False? The tectospinal tract is confined to lumbo-sacral segments of the spinal cord.
FALSE!! It is confined to the Cervical segments of the spinal cord.
What is the function of the Tectospinal tract?
It controls head and movement
Which medial activation tracts innervate proximal limbs and trunk extensors ( both upper & lower limb) ?
Medial reticulospinal & Lateral Vestibulospinal
Which medial activation tract innervate the Head and neck region?
Medial vestibulospinal and Tectospinal tract .
Fill in the blanks. “ ___________ innervates the innervates trunk and proximal limb muscles in upper limb.”
Medial corticospinal tract
What is the major role of the medial pathways?
The major role of the medial pathways is to regulate posture and balance, by acting mainly on the more proximal and axial antigravity musculature.
Which tract plays a significant part in decorticate rigidity?
Rubrospinal tract
Fill in the blanks. “The lateral reticulospinal tract descends in the ____________ column and inhibit __________ while it facilitates __________-.”
The lateral reticulospinal tract descends in the anterolateral column
inhibit extensor and facilitate flexor motoneurones - targeting the Ag more than the Aa motoneurones.
Where does the corticobulbar tract originate?
From the facial region of the motor cortex.
Which Cranial nerve controls eye movements?
CN III, IV, and VI
Which cranial nerves control Cranial, facial , pharyngeal and laryngeal muscles ?
CN V,VII, IX, and X
Which cranial nerves supply some superficial muscles of the back and neck ?
CN XI
Which cranial nerve supplies the intrinsic and extrinsic muscles of the tongue?
CN XII
What is the major function of the Lateral activation system?
The major function of the lateral system is to
over-ride the postural set (inhibit anti-gravity muscles) in order to promote the integrated, but independent and finely controlled, dexterous use of the muscles of the distal appendages, to carry out a highly variable repertoire of movements.
What happens during the recovery of a transection of the spinal cord?
1) Development of hypersensitivity in the denervated neurones below the lesion.
(2) Sprouting of intact nerve terminals below the lesion to make new functional contacts.
During the recovery of a transection of the spinal cord, why do reflexes become hyperactive or altered?
This is as a result of:
(a) loss of descending modulatory control or
(b) newly formed synaptic contacts, and
(c) denervation hypersensitivity.
What does the Medial Reticular Extensor inhibitory area?
This area inhibits mainly the g-motor neurones, and to a lesser extent the a -motor neurones, of the extensor muscles.
Which nuclei is Extensory inhibitory?
Reticular nuclei
Which nuclei is Extensor Facilitatory?
Pontine nuclei
Fill in the blanks. “ The ___________ drives the rigidity which is released from control by higher centers.”
Vestibular system
What are the causes of Decerebrate ?
Primary lesions, such as infarction, hemorrhage, or tumor. Other causes include metabolic encephalopathy, head injury, and brain stem compression associated with increased intracranial pressure
Fill in the blanks. “ Decerebrate posture indicates ____________.”
Upper brain stem damage.
Fill in the blanks. “ Lesion of the vestibular system will __________.”
Abolish speciosity and lead to Hypotonia
What is the function of the Vestibular nuclei?
This selectively control the excitatory signals to the different antigravity M. to maintain equilibrium in response to signals from the vestibular apparatus.
What is the Inhibitory area?
Medullary reticular system
What is Decortication?
Destruction of the cerebral cortex leaving the red nucleus and basal ganglia intact.
What is the site of origin of descending fibres?
The motor cortex
What is the basic unit of a reflex action called?
Reflex arc
What is the reflex arc composed of?
- A sensory organ
- An afferent neuron
- One or more synapses( Interneurons ) in spinal cord or brain
- An efferent neuron
- An effector
What is the name given to a sense organ that monitors length of muscle and how fast muscles change in length?
Muscle spindle
What type of muscle fibres are found in the muscle spindle?
Ia and II
What are the structures that the muscle spindle are composed of?
Intrafusal muscle fibres
Afferent fibres
Gamma motor neurons
Fill in the blanks.” Alpha motor neurons supplies _________ fibres.”
Extrafusal fibres
Fill in the blanks. “ ____________ supplies contractile peripheral part of intrafusal fibers. “
Gamma motor neurons
Where does alpha motor nerves originate from?
Rexed lamina IX
