Question

Which cortical layer is enlarged in the primary motor cortex (M1)?

a) Layer I
b) Layer II
c) Layer V
d) Layer VI

Answer 1

The enlarged cortical layer in the primary motor cortex (M1) is Layer V, which contains large pyramidal neurons essential for initiating voluntary movement.

Step-by-step explanation:

The enlarged cortical layer in the primary motor cortex (M1) is Layer V. The primary motor cortex is notable for its role in initiating voluntary movement and is located in the precentral gyrus of the frontal lobe. Layer V is particularly large in this region because it contains large pyramidal neurons known as Betz cells, which send long axons down the spinal cord to synapse onto lower motor neurons. These lower motor neurons are the target of upper motor neurons that originate in the cerebral cortex, and they ultimately control skeletal muscle contraction, thus translating the cortex's commands into actions.