In the paper by Goslin and Banker (1989) observations about the modifiable state of axons is presented. While the paper makes useful observations about the hippocampal neurites, the experimentation clearly needed to go further to answer many unanswered questions about neuronal polarity. The study revealed that the closer a cut is made to the soma, the more likely the axon would be to regrow somewhere else. However, this study was mainly observational and there were many questions about neuronal polarity and why the length of the neurite would have an effect on the formation of the axon. Based on observations like these, Toriyama et al. (2010) attempts address the mechanisms of how neurons can sense neurite length in order to identify the longest …show more content…
(2010) did a study to define the role of the centrosome in microtubule nucleation and found that the centrosome loses its function as a microtubule organizing center in hippocampal neurons and axons extend independently of centrosomal microtubule nucleation. This led to the conclusion that the decentralization of microtubule nucleation and the dismantling of the centrosome may be essential in the enabling axon branching. Jacobson et al. (2006) did a study to see where kinesins translocate in developing neurons. This study came to the conclusion that the view that all neurons are morphologically and molecularly identical and a break in symmetry is an indication of axon formation is incorrect. The results suggested that at that stage, growth and molecular differentiation are separate events. After reading this paper along with the controversial study of Calderon de Anda et al. (2005) many questions have arisen about whether the instruction for polarized cell growth is truly determined before the neurons are formed. While Steiss et al. (2010) explores the role of the centrosome during neuronal polarization and the necessity of its positioning during, further studies could still explore the possibility of neuritic fate being predetermined. Future studies can also investigate why Calderon de Anda et al. (2005) saw a phenotype with two long neurites instead of several short neurites when neurons had two centrosomal clusters. Could there have also be other factors being affected during the process of generating neurons with more than one centrosome? Cytochalasin D, which was used to block cytokinesis is an inhibitor of actin polymerization. The role of centrosomes in action polymerization should be further explored to better understand the role centrosomes may play a role in actin nucleation and how that relates to neuritic growth and phenotype. It is clear that the phenotype they saw was due to defects in neuronal polarity and it would be interesting to
Hippocampus is a small, curved region, which exists in both hemispheres of the brain and plays a vital role in emotions, learning and acquisition of new information. It also contributes majorly to long term memory, which is permanent information stored in the brain. Although long term memory is the last information that can be forgotten, its impairment has become very common nowadays. The dysfunction is exemplified by many neurological disorders such as amnesia. There are two types of amnesia, anterograde and retrograde. Anterograde amnesia is inability in forming new information, while retrograde refers to the loss of the past memory. As suggested by Cipolotti and Bird (2006), hippocampus’s lesions are responsible for both types of amnesia. According to multiple trace theory, the author suggests that hippocampal region plays a major role in effective retrieving of episodic memory (Cipolotti and Bird, 2006). For example, patients with hippocampal damage show extensively ungraded retrograde amnesia (Cipolotti and Bird, 2006). They have a difficult time in retrieving information from their non-personal episodic events and autobiographical memory. However, this theory conflicts with standard model of consolidation. The difference between these theories suggests that researchers need to do more work to solve this controversy. Besides retrieving information, hippocampus is also important in obtaining new semantic information, as well as familiarity and recollection (Cipolotti and Bird, 2006). For instance, hippocampal amnesic patient V.C shows in ability to acquire new semantic knowledge such as vocabularies and factual concepts (Cipolotti and Bird, 2006). He is also unable to recognize and recall even...
Organized in the class Actinopterygii, seahorses, Hippocampus spp., are marine dwelling organisms found in bodies of water which span from tropical to temperate zones around the Earth. As cited by Foster in Life History and Ecology of Seahorses, research by R. A. Fritschze suggests that the genus Hippocampus diverged at least 20 million years ago from its ancestral origins. Research pertaining to organisms organized under the genus Hippocampus are conflicting in regards to the number species contained within it, although a general figure places the number at around fifty discovered species(website source). These odd-looking organisms reside at shallow depths of less than 30 meters and can be found in habitats containing seagrass beds and coral reefs(Foster 10). Hippocampus spp. are all predatory organisms, their main sources of food consist of small crustaceans and fish, as well as other organisms which are small enough to be consumed(lourie 10). Although Hippocampus spp. are predatory, their size and restricted mobility capabilities place them at risk of being prey for other carnivorous organisms.
Through studies performed on sleep-deprived rats, experimental results have shown a decrease in cellular activity in the hippocampus. The hippocampus is responsible for most of the brain’s memory processing. When entering into sleep deprivation, the brain will experience consequences such as a failure for the hippocampus to encode, consolidate, or retrieve signals powering memory processing. As a result, researchers are looking for cellular characteristics that could lead to further details into the relationship between sleep deprivation and memory impairment. There are several different ways memory can be disrupted, one suggested in being an imbalance of neurotransmitters in the hippocampal region of the brain. Both hormonal and oxidative stress are also factors that are observed to play major roles of memory impairment in the hippocampus. These
Therefore, they summarize that the reason why Clive suffers in the Amnesia is caused by the hippocampus is not affected. The Hippocampus is a structure that is located inside the temporal lobe, and that is a part of the limbic system. The function of the Hippocampus is similar to a post office used for encoding, storage and recalling memories, all presenting information would first remain, analysed and encoded in the Hippocampus then transmit them to different areas of the brain. In other words, Clive is unable to encode memory and hold information which is currently aware, and it is difficult to form new long-term memory such as explicit and semantic memory. Clive Wearing, now 78 years old, still cannot recover from the anterograde amnesia, he becomes a man who has the shortest memory in the world.
Kandel, E. R., J. H. Schwarz, and T. M. Jessel. Principles of Neural Science. 3rd ed. Elsevier. New York: 1991.
When a message comes to the brain from body parts such as the hand, the brain dictates the body on how to respond such as instructing muscles in the hand to pull away from a hot stove. The nerves in one’s skin send a message of pain to the brain. In response, the brain sends a message back dictating the muscles in one’s hand to pull away from the source of pain. Sensory neurons are nerve cells that carry signals from outside of the body to the central nervous system. Neurons form nerve fibers that transmit impulses throughout the body. Neurons consists of three basic parts: the cell body, axon, and dendrites. The axon carries the nerve impulse along the cell. Sensory and motor neurons are insulated by a layer of myelin sheath, the myelin helps
Neuroplasticity is the term given to the physical changes occurring in the brain over one’s lifetime. In the past, it was believed that the brain stayed the same size and shape all one’s life, but now that modern technology has given us the ability to view the brain visually and observe its changes, we have seen evidence of the brain’s natural ability to change its shape, structure and density. Neuroplasticity occurs in small scales over time, but can also change in response to injury, behaviour, environmental stimuli, thought, and emotions. This is significant in relation to learning, memory, development, and recovery from brain damage (Pascual-Leone et al, 2005). Neuroplasticity occurs when new
The neurons or brain cells are shaped like trees. Young brain cells, called soma, resemble an acorn or small seed of a tree. The seed sprouts limbs when stimulated, called dendrites. Further on in development, the cell will grow a trunk like structure called an axon. The axon has an outer shell, like the bark of a tree, called the myelin sheath. Finally, at the base of the cell, there are root-like structures called axon terminal bulbs. Through these bulbs and the dendrite of another cell, cells communicate with each other through electrochemical impulses. These impulses cause the dendrites to
A neuron is a cell that transmits information throughout the human brain and nervous system. The average human has approximately 100 billion neurons and about 90% of the neurons are located in the cerebral cortex. For as many neurons there are in the human brain, there are as many neuroglia which serve to protect and support the neurons. Neurons are unlike any other brain cell because at birth the neurons are able to divide and make new cells. The cells divide and increase in size until about the age of eighteen but they last a lifetime. The most interesting part of neurons dividing occurs in the hippocampus. The hippocampus is an area in the human brain essential to memory and is the only area in the brain where neurons continue to divide and increase in size throughout life. (Mastin,
This paper involves how the brain and neurons works. The target is to display the brain and neurons behavior by sending signals. The nervous system that sends it like a text message. This becomes clear on how we exam in the brain. The techniques show how the brain create in order for the nerves about 100 billion cells. Neurons in the brain may be the only fractions of an inch in length. How powerful the brain could be while controlling everything around in. When it’s sending it signals to different places, and the neurons have three types: afferent neurons, efferent neurons, and the interneurons. In humans we see the old part of emotions which we create memories plus our brain controls heart beating, and breathing. The cortex helps us do outside of the brain touch, feel, smell, and see. It’s also our human thinking cap which we plan our day or when we have to do something that particular day. Our neurons are like pin head. It’s important that we know how our brain and neurons play a big part in our body. There the one’s that control our motions, the way we see things. Each neuron has a job to communicate with other neurons by the brain working network among each cell. Neurons are almost like a forest where they sending chemical signals. Neurons link up but they don’t actually touch each other. The synapses separates there branches. They released 50 different neurons.
2. Sketch what Lorenzo’s neurons most likely looked like after one year. Then sketch a healthy neuron.
During early childhood, there is a huge proliferation of connections between neurons, usually peaking around the age of two. The adolescent brain then cuts down the amount of connections, deciding which ones are important to keep and which can be let go. While there are various theories as to the molecular mechanisms by which pruning actually occurs, most agree that pruning is primarily carried out by a very motile form of glial cell, called microglia [1], and pre-programmed cell death (apoptosis). These microglia are thought to remove cellular debris and perform surveillance during the healing process of an injured brain, but in the healthy, developing brain they have a possibly more important function. If a synapse receives little activity, it is weakened and eventually deleted by microglia and other glial cells through a process called long-term depotentiation (LTD). After the synapse has been removed, the space and resources that it once used are taken by other synapses. These synapses are strengthened by long-term potentiation (LTP). These processes and various others take place throughout development, peaking at adolescence and reaching their base around the age of 21, and transform the brain to create more complex and efficient neuronal configurations.
Sperry, R. W. (1963, October 15). Chemoaffinity in the Orderly Growth of Nerve Fiber Patterns and Connection. Natioanl Academy of Science, 50(4), 703-710.
R. L. Paul, M. M. (1972). The Species of the Brain Research, 1-19. pp. 113-117. S. A. Clark, T. A.
The human body is divided into many different parts called organs. All of the parts are controlled by an organ called the brain, which is located in the head. The brain weighs about 2. 75 pounds, and has a whitish-pink appearance. The brain is made up of many cells, and is the control centre of the body. The brain flashes messages out to all the other parts of the body.