Question

Explain how motor signals travel from the PMC to the extremities and how sensory information travels from the body’s exterior to the brain. You needn’t worry about left and right with the PMC or the PSC.In this assignment, you should mention the following vocabulary: decussation, medulla oblongata, homunculus, receptors, spinal cord, spinal nerves.

Answer 1

The primary motor cortex( broadmann area 4) is a brain region that in humans is located in the dorsal portion of the frontal lobe,it is the primary region of the motor system and works in association with other motor areas including premotor cortex,posterior parietal cortex.

Pathway=As the motor axons travel down through the cerebral white mtter they move close together and form part of the posterior limb of the internal capsule

Theycontinue down into brainstem where some of them after crossing over to the contralateral side distribute to the cranial nerve motor nuclei. after crossing over to contralateral side in the medulla oblongata the axons travel down the spinal cord as the lateral corticospinal tract.

Fibres that do not cross over in the brainstem travel down seprate ventral corticospinal tract ,and most of them cross over to the contralateral side in the spinal cord before reaching the motor neurons.

Inshort for motr function the brain sends the signal to spinal corde,the spinal cord send signal to erve,and finally signal to muscle via spinal cord

Sensory information from body to brain

These neurons are called as afferent neurons,that convert specific type stimulus via their receptors into action potential or graded potential,this process is called sensory transduction,the sensory information will travel along afferent nerve fibres to the brain via spinal cord by different sensory receptors.

The sensory information enters the spinal cord on the same side of the body as the stimulus,ascending tracts cross over the midline of the body to the contralateral side of the thalamus,the thalamus directly signal to the cerebral cortex for the conscious perception.