General:

Gross neuroanatomy had to do with the brain structures that can be seen by the naked eye; fine neuroanatomy, has to do with the organisation of the brain at the cellular or subcellular level.

Neuroanatomy

The central nervous system consists of the brain and spinal cord. The peripheral nervous system consists of all nerves outside of the central nervous system.

The lobes of the brain include the

1. 1. Frontal lobe
2. 2. Parietal lobe
3. 3. Temporal lobe
4. 4. Occipital lobe
5. 5. Limbic lobe (sometimes)

• The frontal lobe is for: planning, cognitive control and execution of movements.
• The parietal lobe receives sensory input about touch, pain, temperature & limb position & is involved in coding space & co-ordinating actions.
• The temporal lobe contains auditory, visual & multimodal processing areas.
• The occipital lobe processes visual information
• The limbic lobe is involved in emotional processing, learning & memory.

• Gyri are the protruding areas seen on the surface of the cortex; sulci or fissures, are the enfolded regions of the cortex.
• Gray matter is formed by the cell bodies in the brain, white mater is formed by the axons.
• White matter form tracts that connect various regions of the brain. Tracts are referred to by source and then by target. E.g. The corticospinal tract goes from the cortex to the spinal cord.
• Retrograde tracers are injected at the axon terminal and proceed up the axon to label the cell body. Anterograde tracers are injected at the cell body and travel down the axon to label the axon and the axon terminals.
• The corpus callosum is the largest interhemispheric (commissural) white matter tract in the brain.
• Brodmann divided the brain into distinct regions based on underlying cytoarchitectonics.
• Cerebral cortex can be subdivided into major regions that differ in the degree of complexity of the neuronal layering (e.g. neocortex, allocortex & paleocortex)
• The basal ganglia are involved in movement processing.
• The hippocampus is involved in learning & memory.
• The thalamus is the relay station for almost all sensory information. Association cortex if neocortex that is neither sensory nor motor in function.
• The hypothalamus is important for the autonomic nervous system and endocrine system. It controls functions necessary for the maintenance of homeostasis. It is also involved in emotion processing and in the control of the pituitary gland.

• The brainstem includes the midbrain, pons, and medulla. Nuclei of the brainstem control respiration, sleep and wakefulness.
• The cerebellum integrates information about the body and motor commands and modifies motor outflow to effect smooth, coordinated movements.
• The spinal cord conducts the final motor signals to the muscles and it relays sensory information from the body’s peripheral receptors to the brain.
• The autonomic nervous system is involved in controlling the action of smooth muscles, the heart, and various glands. It includes the sympathetic & parasympathetic systems.
• The sympathetic system uses the neurotransmitters neuroepinephrine. This system increases heart rate, diverts energy from the digestive tract to the somatic musculature, and prepares the body for fight-or-flight responses by stimulating the adrenal glands.
• The parasympathetic system uses acetylcholine as a neurotransmitter. It is responsible for decreasing heart and stimulating digestion.

Neurodevelopment

· The nervous system develops fro the ectoderm, which forms a neural plate. The neural plate becomes the neural groove and eventually the neural tube.

· Neuronal proliferation is the process of cell division in the developing embryo and foetus. It is responsible for populating the nervous system with neurons.

· Neurons and glial cells are formed fro precursor cells. After mitosis these cells migrate along the radial glial cells to the developing cortex.

· The key to the type of cell that will be made (e.g. the stellate or pyramidal cell appears to be the time at which the cell is born (genesis) rather than the time at which it begins to migrate.

· The radial unit hypothesis states that the columnar organisation in the adult cortex is derived during development from cells that divide in the ventricular region.

Neurogensis and plasticity

· A belief strongly held by the general public (and, until recently most neuroscientists) was that the adult brain produces no new neurons. We now know that this is not the case and that new neurons form throughout life in certain brain regions.

· Synaptigenesis is the birth of new synapses

· Neurogesis is the birth of new neurons.

· The adult brain is plastic, that is, able to remap or change its function. The topographic map of the sensory cortex, for instance, will remap to reflect changes in sensory experience (e.g. Increased use of fingers in the left hand as in violin players, or increased use of part of the body because of loss of a limb)

· And the visual cortex is able to remap to process information about touch and audition after sensory deprivation e.g. the onset of blindness.

· The mechanisms that underlie cortical plasticity are not entirely understood but might include on or both of the following: (a) unveiling of weak connections that exist already in the cortex through the release of inhibition and/changes in the efficacy of the synapses (b) the growth of new neurons or synapses