Throughout this lecture, refer to the SLIDE SHOW with diagrams of most of these points: here

Discussing the segmental nature of the spinal cord: each segment has sensory (touch, pain, temperature) input from a particular dermatome through the spinal nerves, and motor output to the muscles in that dermatome through the spinal nerves. The cell bodies of the motor neurons that extend their axons to the muscles are located in the ventral gray matter of the spinal cord. The cell bodies of the sensory neurons that receive input from the axons that originated in the skin surface are located in the dorsal gray matter. The gray matter (butterfly shape) in the center of the spinal cord contains cell bodies, the white matter contains axons that are traveling up to the brain (these are carrying sensory information) and axons that carry motor instructions down from the brain where they will communicate with cell bodies that send out their axons to muscles at the appropriate spinal cord segment. The distribution of white and gray matter at the various levels of the spinal cord is arranged differently depending on which spinal cord segment it is.

The autonomic nervous system (motor control for the internal organs) contains axons that leave the spinal cord and brain stem and send their axons to their targets—the body’s organs. The sympathetic division consists of neurons that have cell bodies in the central regions of the spinal cord and send their axons (along the spinal nerves) to the organs of the body that increase their activity during times of stress, when the body must mobilize its resources for meeting challenges (fight-or-flight). The parasympathetic division consists of neurons that have cell bodies in the brain stem/upper spinal cord and lower spinal cord and send their axons to those same organs, but have largely the opposite effects.

Other things that the Nervous System must do:

• Interpret Stimuli
• Initiate Movements
• Think/Decide/Plan/Motivate
• Language

These are all functions of the cerebral cortex, the structure we discussed briefly last time--the outer covering of the cerebral hemispheres. Wrinkled cortex accomplishes an increased surface area (stretched out, would be the size of a 16" pizza a few millimeters thick) in a fixed-size cranium. The cortex is divided into "lobes".

Frontal lobe is separated by central sulcus from the parietal lobe. Temporal lobe is located low on the side, the occipital lobe is in the back of the brain.

Functions:

Occipital lobe: contains primary visual cortex and visual association cortex (discussion of primary sensory cortex all over the brain and higher order cortex that interprets and understands sensory information)

Temporal lobe: contains primary auditory cortex (and auditory association cortex) as well as areas responsible for language. Under the surface of the temporal cortex lies the hippocampus, the structure important for memory formation.

Parietal lobe: strip of cortex (called a gyrus) behind the central sulcus is called the post-central gyrus…here lies a map of the body surface known as the primary somatosensory (touch sensation) cortex—stimulation of this strip of cortex will result in touch sensations along the body surface in a highly organized somatotopic map (adjacent areas of the cortex are responsible for adjacent areas of the body surface). Also in the parietal lobe are some of the higher order processing areas for visual information (especially those regions that are adjacent to the occipital lobe)

Frontal lobe: the precentral gyrus (analgous to the postcentral gyrus which contains primary somatosensory cortex) is the primary motor cortex—stimulation of this body map results in movements of various muscle groups in the body, again in a highly organized fashion. Other regions of the frontal lobe are involved in motor planning…deciding the precise arrangement of which spinal cord motor neurons to activate in order to execute planned movements takes place in “motor association” cortex. The prefrontal area of the frontal lobe (the most forward region of the brain, that which is most highly developed in humans compared to other animals) carries out the brain’s “executive function”…planning, consciously deciding on a course of action in response to sensory stimulation, considering social consequences of actions and formulating plans for meeting goals—motivated behaviors.

Subcortical nuclei also play prominent roles in behaviors

Basal Ganglia: fine motor control and initiation of movements--degenerates in Parkinson's Disease
Limbic System: involved in responses to emotion-producing stimuli--organize emotional responses to threatening or otherwise emotion-provoking stimuli. Located largely at the interface between the higher order cortical structures and the brain stem nuclei controlling the Autonomic Nervous System.
Hippocampus: involved in memory formation. Damage here impairs ability to learn. Site of great plasticity, even into adulthood.

Subcortical white matter makes up a large portion of the cerebral hemispheres.

Brain Stem/Cerebellum: see diagram at end of slide show