NC299S14

Chapter 14 Motor System 4 : Motor Cortex

The several motor cortices control voluntary manipulative and delicate motor movements and initiate motor performance. Descending cortical projections to the motor neurons travel via two pathways, the corticobulbar tract and the corticospinal tract, collectively called the pyramidal tract. These tracts control cranial and spinal motor neurons (LMN), respectively. Activity at the motor cortex is influenced by extensive feedback channels from the cerebellum, brainstem, thalamus, and basal ganglia.

不同的運動皮質支配隨意操縱和精巧靈敏的動作以及執行運動的開端。 下行皮質投射至運動神經運行經由兩個路徑，corticobulbar tract和大腦皮質脊髓徑，總稱錐體路徑。這些路徑個別控制腦和脊髓運動神經。運動皮質的活動受小腦、腦幹、視丘、及基底核的回饋通道影響非常大。

A lesion interrupting the excitatory projections from the motor cortex results in a specific loss of delicate motor control. It also results in sings of muscle weakness, flaccid tone, hyporeflexia, and loss of reflexes. However, in several weeks, the hyporeflexia and flaccid tone are replaced by increased reflexes (hyperreflexia ) and spastic tone in muscles.

若有一傷害打斷運動皮質的刺激將會很明顯的造成精細運動的控制喪失。 也會造成肌肉無力、肌肉張力下降、反射減弱、甚至反射作用喪失。然而在幾週內，反射減弱和肌肉張力下降會轉變為反射過強以及肌肉痙攣的現象。