NROSCI 0080 1st EditionExam # 1 Study GuideTopic #1: Development of the Nervous SystemStructural development can predict behavior. How/when areas develop: similar for similar systems.Behavior can be used to predict structure. There are factors that influence both structure and behavior (injury, hormones, etc) and can be studied both.- Induce injury  see what behaviors are modified- Induce behavior  see what structures are activated/suppressed About 2 weeks after fertilization, the blastocyst migrates from the fallopian tube and implants into the uterine wall and forms the embryonic disc. This embryonic disc becomes the baby, and everything else becomes the amniotic sacand placenta. The cells of the embryonic disc differentiate and form 3 distinct layers:1. Endoderm2. Ectoderm- Becomes the nervous system!!3. MesodermThe ectoderm thickens in the center. This thickening forms the neural plate. The bottom of the neural plate grows much faster than the top, causing it the neural plate to curl up. This curling forms the neural groove—the midline of the structure. The curling edges eventually meet and fuse at the top. This forms the neural tube. This hollow structure becomes the central nervous system and the neural pores at each end remain open for ~3 weeks. If the anterior pore fails to close, anencephaly results (fatal condition, “no brain”). If the posterior pore fails to close, spina bifida results (lower spinal nerves cannot reach their destination in the legs—loss of motor control and sensation). The developing neural tube forms three main bulges that form the various parts of the nervous system:1. Forebrain bulge: forms the telencephalon and diencephalona. Telencephalon develops into the cortex and limbic systemb. Diencephalon develops into the thalamus and hypothalamusc. The lateral and third ventricles also develop from the forebrain bulge2. Midbrain bulge: forms the mesencephalona. Mesencephalon develops into the tectum and tegmentumb. Cerebral aqueduct 3. Hindbrain bulge: forms the metencephalon and myelencephalona. Pons, medulla, cerebellumb. Fourth ventricle The spinal cord regions bud off of the hindbrain bulge and surrounds the central canal.As we evolved higher processing abilities, our skull size/shape does not change. Instead, our brains evolved to increase its surface area by forming folds. These folds form bumps and grooves. The bumps are called gyri. The grooves are called one of two things, depending on their size. Sulci are shallow grooves, and fissures are deep grooves. There are also hollow spaces within the brain called ventricles. These have a protective function to absorb force from a blow to the head as to not spread the damage across the entire brain. These ventricles are filled with cerebrospinal fluid (CSF), which also reduces the net weight of the brain due to buoyancy. Cell birth: each cell starts out as a totipotent stem cell, meaning that it has the potential and ability to become any type of cell. After some differentiation, it becomes a specialized blast cell, meaning that it can only become one generic type of cell (neuron, glial cell, cardiac cell, etc). After even more differentiation, the cell becomes one very specific type (bipolar sensory neuron, oligodendrocyte, etc).The differentiated cells now have to get to their specific destination (we can’t have brain cells in our hearts!). Radial glial cells guide neurons to their final destination. Once all the cells are in place, the radial glial cells differentiate into other types of glial cells. All of this neural division and migration is completed by birth—we are born with the same number of neurons we will have our whole lives, and they stay in the same place. However, newconnections are constantly being made, and old ones are being pruned out. New dendrites and more extensive axonal branches are made, which contributes to the growing brain size as we mature in the early stages of life. Axons know where to branch out to/away from due to chemicals produced by other cells. The tip of the axon is called the growth cone. It is specialized to detect these chemicals. Lance-Jones and Landmesser conducted an experiment to see how long neurons are able to migrate to their proper destination. Mature neurons were unable to reach their proper destination, whereas fetal ones were able to. There comes a time right before birth where neurons lose the ability to migrate properly and therefore stay put. Simple synapses form first, then synapses in deep cortical areas. Formation of synapses happensat an extremely high rate during the first year of life. However, not all of these connections are necessary, and the brain compensated for this via synaptic pruning. Some axons are wrapped with myelin to speed up the speed of conduction. This myelin wrapping is fatty and is formed from projections of glial cells. In the CNS, they are called oligodendrocyes, and in the PNS, they are called Schwann cells. Myelin sheaths are being formed for the first 20 years of life. These brain development stages correlate with the different stages of behavior and motor ability that arises in infants.**Each milestone has a critical period when synapses are being formed. If there is a lack of adequate stimuli during the critical period, then those connections cannot be formed and the individual will forever experience deficits in that area. In summary, there are 7 stages of brain development:1. Cell birth2. Cell migration3. Cell differentiation4. Cell maturation5. Synaptogenesis—formation of synaptic connections 6. Synaptic pruning—not all synapsis are useful, so our bodies cut them out7. Myelogenesis—formation of myelin sheaths Topic #2: Anatomy of the BrainThe brain controls our motions and integrates sensory information to create a representation of our surroundings. It also has adaptive properties for environmental changes, learning, response to injury, etc.The nervous system is broken down as follows: Sensory information is afferent information. It originates in a body part, is relayed up the spinal cord, into the hindbrain, then up to higher levels of processing.Nervous SystemPeripheral NervousSystem:- Everything outside the skull/vertebraeCentral NervousSystem:- Brain- Spinal CordAutonomic NervousSystem:- Involuntary movementsSomatic NervousSystem:- Voluntary movementsMotor information is efferent information (exits the brain). It originates at higher cortical processes and descends