Descending Tracts.. Pyrimidal Tract

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Descending Tracts (Motor/Efferent Tracts):

Descending Tracts (Motor/Efferent Tracts) Professor Husan Bano Department of Physiology Al- Tibri Medical College & Hospital ISRA University Karachi Campus

Descending Tracts (Motor/Efferent Tracts):

Descending Tracts (Motor/Efferent Tracts) Descending tracts are those tracts which transmit the impulses from brain to spinal cord. Descending tracts are of three types. 1. Pyramidal tract 2. Extra pyramidal tract 3. Cortico -bulbar tract

Pyramidal Tract:

Pyramidal Tract This is the largest tract starting from the motor cortex and reaching up to the last segment of spinal cord. The fibers of these tracts originating from the cortex , passing through medullary pyramids and enter into spinal cord . medulla

Pyramidal Tract:

Pyramidal Tract At the Junction of medulla oblongata and spinal cord it is divided into 3 tracts. Crossed pyramidal tract 2. Uncrossed pyramidal tract Direct pyramidal tract.

Pyramidal Tract:

Pyramidal Tract At the Junction of medulla oblongata and spinal cord it is divided into 3 tracts. 1. Crossed pyramidal tract ( Large lateral cortico spinal tract) 2. Uncrossed pyramidal tract (Small lateral cortico -spinal tract) 3. Direct pyramidal tract. ( Uncrossed anterior cortico spinal tract)

PowerPoint Presentation:

3 types of Pyramidal tract PONS Medulla PONS Medulla PONS Medulla Crossed prarimidal Tract Direct Prarimidal Tract Un Crossed prarimidal Tract

Pyramidal Tract:

Pyramidal Tract Pyramidal tract consists of about 1 million neuron. 60% myelinated NF 40% non- myelinated NF Nerve fibers of pyramidal tract originating from all areas of frontal lobe and parietal lobe . Pyramidal tract functions 12 to 18 months after birth.

Pathway of Pyramidal tract:

Pathway of Pyramidal tract Pyramidal tract originated from frontal and . parietal lobe These fibers passes through Crona Radiata . ( Crona radiata : projecting fibers which connect the brain stem and spinal cord.) These fibers converge and passes through internal capsule , and occupying genu . ( Genu : bent of internal capsule.)

Pathway of Pyramidal tract:

Pathway of Pyramidal tract From GENU it is passes through the peduncle of mid brain , pons and enter into the pyramids of medulla Now decussating takes place in the lower medulla and form crossed and uncrossed tract. About 80-90% decussate in lower part of medulla

Pathway of Pyramidal tract:

Pathway of Pyramidal tract 55% pyramidal fibers ends in cervical region. 20%----------------------ends in thoracic region 25%----------------------ends in lumbo-sacrral region

Functions of Pyramidal Tract:

Functions of Pyramidal Tract Pyramidal tract convey motor impulses to spinal cord and control the fine and skilled voluntary movement such as painting, writing , typing etc.

Difference Between Upper And Lower Motor Neuron:

Difference Between Upper And Lower Motor Neuron Upper motor neuron ? Lower motor Neuron ?

Lesions of Pyramidal Tract:

Lesions of Pyramidal Tract Paralysis of upper motor neuron: Loss of volitional movements Loss of superficial reflexes. Increased deep reflexes.(exaggerated) Spasticity (paralyzed muscle is rigid due to increased muscle tone. Bibinski’s sign positive (Planter reflex becomes extenser .

Lesions of Pyramidal Tract:

Lesions of Pyramidal Tract Paralysis of Lower Motor Neuron: Loss of all voluntary movement. Flaccid paralysis due to loss of muscle tone. Loss of all deep reflexes. Loss of superficial reflexes except the planter reflex. Muscle dystrophy.

Cortico-bulbar Tract:

Cortico -bulbar Tract This tract is originating in the inferioor position of pre-central gyrus . These fibers passes through the genu of internal capsule and bilaterally distributed in the reticular formation and to spinal cord.

Functions of Cortico-bulbar tract:

Functions of Cortico -bulbar tract This tract control the movement of: Larynx Pharynx Palate Face Jaws and E yes.

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