What is the difference between pyramidal and extrapyramidal tracts

Axons which will innervate the muscles of the face are located medially. This tract is known as the corticobulbar tract. The axons which form the corticobulbar tract exit at their appropriate levels to synapse with their lower motor neurons in the cranial nerve nuclei. Link to cranial nerves. The axons which will innervate the legs are located laterally within the cerebral peduncle. Thus the name "lateral corticospinal tract".

These axons then aggegate to form the pyramids in the medulla. Thence the name "pyramidal tract". This is a very distinctive area on cross section known as the Pryamidal Decussation. The pyramidal decussation separates the medulla,above, from the spinal cord, below.

Injuries to the upper motor neurons in the cortex or to their axons before they enter the pyramidal decussation result in spastic paralysis of the opposite side of the body. Injuries to the pyramidal tract below the decussation or to the lower motor neurons in the spinal cord cause paralysis on the same side of the body.

The upper motor neuron axons then synapse on lower motor neurons in the Anterior horn of the spinal cord. The axons of these lower motor neurons then exit the spinal cord via the Ventral root. Related Books Free with a 30 day trial from Scribd. Related Audiobooks Free with a 30 day trial from Scribd. Patel Vipsa. Md Salim Usuf. Mohammed Tabrez. Sahriinii Paodumai. Sayyam Jan Sayyam. Hansie Paul. Aditya Nanddedkar. Srikar Teja. Ganji Anurag. Vamsi RocksForever. Zamiruddin Khalid , -- at Nangarhar regional public health hospital.

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Please write a single word answer in lowercase this is an anti-spam measure. This field is for validation purposes and should be left unchanged. Introduction The central nervous system uses ascending and descending pathways to communicate with the external environment, this article will discuss the descending motor tracts. These functional groups contain several anatomical tracts , one for each side of the body: Pyramidal : conscious control of muscles from the cerebral cortex to the muscles of the body and face; and Extrapyramidal : unconscious, reflexive or responsive control of muscles from various brainstem structures to postural or anti-gravity muscles You might also be interested in our Anatomy Flashcard Collection which contains over anatomy flashcards in addition to advanced features such as spaced repetition.

Table 3. Table 4. The facial nucleus 6. Clinical relevance: decerebrate and decorticate posturing Now that we understand the rubrospinal tract and the role it plays in adjusting flexor tone in the upper limb, we can discuss decorticate versus decerebrate posturing. Figure 5. Decerebrate posturing. Figure 6. Decorticate posturing. This results in upper limb flexion in decorticate posturing for lesions above the red nucleus. In decerebrate posturing, the loss of the rubrospinal tract causes the lateral reticulospinal tract to be overwhelmed by the other extrapyramidal tracts, resulting in upper limb extension.

Disruption of the lateral corticospinal tract allows the medial reticulospinal and medial and lateral vestibulospinal tracts of the lower limbs to overcome the input from the lateral reticulospinal tract. This results in lower limb extension in both decorticate or decerebrate posturing. This view reflects a long-held tradition in clinical neurology that equates abnormal involuntary movements and postures AIMP with the basal ganglia and pathways.

Although this may be valid for most vertebrates, it certainly does not apply to humans. This is so due to the simple fact that, except for a few critical reticulospinal projections, the human extrapyramidal pathways are rather reduced in bulk. Their chief functional role concerns the promotion of faciorespiratory synergies, especially automatic breathing 47 and the extreme emotional expressions of laughing and crying Figure: The fundamental organization of the motor system in vertebrates and man.

In most vertebrates, including nonhuman primates, the extrapyramidal and pyramidal fiber systems run in parallel from the motor cortices MC to the motoneuron pools of the brainstem and spinal cord. The extrapyramidal system consists of a series of cortical projections interrupted at the basal ganglia BG and brainstem tegmentum TEG whence tegmentospinal projections originate chiefly, reticulospinal, vestibulospinal, tectospinal and rubrospinal tracts.

The adoption of obligate erect bipedalism in humans was paralleled by a profound cerebral reorganization. These changes are reflected in an unprecedented increase in the ansa lenticularis fiber system.

The ansa directs the projections from widespread cortical areas into the thalamic motor nuclei mt , which project back to the motor cortices that give rise to the pyramidal tracts.

The increase in the pyramidal tracts MP , in turn, is paralleled by an unprecedented decrease of the descending motor extrapyramidal pathways. Note the perpendicular and parallel orientations of the quadrupedal and human body axes arrows , respectively, in relation to gravity g.

Moreover, in at least one case extensive destruction of the pontomedullary tegmentum leaving the pyramidal tracts intact did not produce any motor impairment of trunk or limbs Because, as demonstrated by clinicoanatomical studies, the parallel extrapyramidal pathways perform a limited, albeit vital automatic respiration , role in human movement, one must look for alternative pathways for the insertion of the workings of the basal ganglia into motor behavior.

Several independent lines of evidence indicate that the pyramidal tracts are the pathways through which the basal ganglia express their activity. One such compelling evidence is provided by the post-hemiplegic disorders of movement. Choreoathetosis and dystonia are well-known phenomena in some patients with strokes of the striothalamocapsular region These AIMP become clinically apparent if at least some fibers of the pyramidal tracts are spared in injuries of the internal pallidal segment or its thalamic recipients.