The role of the brain in addiction Essay Example | Topics and Well Written Essays - 2000 words

The role of the brain in addiction - Essay Example Photoreception and Signal Transmission: The photoreceptor cells of the retina are the cones and rods. Light stimulus causes changes in the visual chemical of the cones and rods producing a receptor potential. This passes through the bodies of the rods and cones and acts at the synapses to induce a signal in the bipolar cells. This signal is then transmitted to the ganglion cells. The axons of the ganglion cells leave the eyeball posteriorly to become the optic nerve. The two optic nerves enter the cranial cavity and join to form the optic chiasma. In the optic chiasma, the axons from the nasal (medial) halves of the retinas cross over to the opposite sides. From the optic chiasma on either side of the brainstem, the optic tracts continue. The optic tracts relays information to the LGB (lateral geniculate body) of the thalamus. From here, information is carried to the occipital lobes of the cerebral cortex, where the information is perceived as conscious vision. Due to the crossover, the right visual field is perceived within the left hemisphere, and the left visual field is perceived within the right hemisphere (Lesson assignment, n.d.) The nervous pathways for sound The neuron associated with the hair cells of the organ of Corti (located in the basilar membrane of the inner ear) carries the sound stimulus to the brainstem. Through a series of connections, the signal reaches Brodmann's area number 41, in the temporal lobe of the brain where the stimulus is perceived as sound.