• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Neurophysiology - Discuss the roles of development learning and evolution in the construction of the nervous system

Extracts from this document...

Introduction

Neurophysiology Discuss the roles of development learning and evolution in the construction of the nervous system The nervous system is responsible for the initiation, propagation and co-ordination of animal behaviour. How it is constructed and what factors are involved encompasses many fields of biology, from ethology and neurophysics to evolution. In this essay I will describe the roles of development learning and evolution in the construction of the nervous system and give experimental evidence that backs up these theories. Evolution Evolution deals with the origins of the nervous system, where it comes from determines how it will be constructed. This will have direct consequences on the relative fitness of an individual as the layout of the nervous system relates to how the animal behaves. Phylogeny is very important therefore to analyse how changes in the nervous system relate to the evolution of behaviour. The only realistic way of studying the evolution of nervous systems, particularly the events, which lead to, their current day form, is through comparative biology. By comparing closely related species in similar niches, the difference in their behaviour must have a genetic/nervous system origin. A good example of how behaviour can be genetic in origin and show that nervous systems can evolve to create different behavioural responses is found in deer. The white tailed deer odocoileus virginianus and the mule deer O. ...read more.

Middle

The pathway and target selection mechanisms are believed to be autonomous, activity independent. This has been demonstrated by work done on Ambystomid Urodeles (Twitty and Johnson 1934). The embryos were paralysed with TTX for a period of days until the larvae would normally move and feed for themselves. At that point the TTX induced paralysis wore off and surprisingly the animals soon began to swim and eat in a remarkably normal fashion. In the 1970's a theory developed that the innervation of muscles is largely at random, with patterns emerging later by the elimination of connections and cell death. This appears to be a very costly mechanism as neurones are being created only to soon be destroyed. This theory was abandoned when studies were performed on chicks (Landmesser 1978, 1980) and zebra fish (Eisen et al, 1986) that showed specific motor neurones innervate their target muscle with relatively few error from the outset. They possess unique identities that allow them to differentially respond to the choice point region, follow particular pathways and innervate specific muscle. Sperry first postulated the mechanism for the directionality of growth cone movement in 1963 when he suggested the chemoaffinity hypothesis. Neuronal growth cones were specifically guided toward their correct targets by specific chemotactic cues and proposed gradients of chemical labels. The neurones enhance and transduce the signals from the extracellular matrix to remodel cytoskeletal elements. ...read more.

Conclusion

It also appears that the protein CREB is required for functional plasticity but it is not sufficient for morphological plasticity. The changes to the gross structure of the nervous system in response to learning can be seen in an experiment performed on monkeys that were trained to preferentially use only some fingers. The cortical representation of those fingers expanded (Merzenich and colleagues). This has also been demonstrated with violinists who show a disproportionate representation of their left hand (fingering hand) when compared to their right hand (bow movement). Conclusions The roles played by each factor described here each have their own specific effect on the construction of the nervous system. The evolutionary aspect controls the "blueprints" of the nervous systems that are hard coded into the DNA of the animal. However it is not specifically the genetic makeup of the nervous system that natural selection acts against, rather the phenotype of the nervous system, which is the combination of the developmental and the learning factors. The evolutionary factors alter the genotype, the only source of variation that can be passed down to their offspring. The development can only attempt to recreate the layout as specified by the different alleles; it cannot exceed them in terms of functionality. The true source of variation depends on the extrinsic information obtained and stored in memory, but that us not able to cross generations (with the exception of tradition) and so could be an explanation for the high evolutionary conservation of the nervous system. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Computer Science section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Computer Science essays

  1. Visual basic

    False X7.Visible = False X8.Visible = False X9.Visible = False End Function Private Sub Image1_Click() If sp1 = True And O1.Visible = False Then X1.Visible = True sp2 = True sp1 = False Exit Sub End If If sp2 = True And X1.Visible = False Then O1.Visible = True sp1

  2. Signal Theory

    It will compress the data before transmitting it. As soon as it receives the data it decodes and decompresses the data so it can arrange it in the way that it scanned it from the original document. There are a lot of things in a fax machine that allow it to do its function.

  1. Primary or Secondary Storage.

    This increases the chances that the next instruction requested by the CPU is already in cache. When a request from the CPU is found in cache, this is referred to as a cache hit. When it is not found it is referred to as a cache miss.

  2. Signalling Theory

    They are Amplitude Modulation, Frequency Modulation and Phase Modulation. They are all ways of modulating a digital signal from the computer to be able to pass freely down the phone line to its desired destination. As analogue wave signals can only pass through a phone line this operation becomes an imperative task.

  1. Smart Card System

    So whoever generates K can publish (pq,e). Anyone can send a secret message to him; he is the only one who can read the messages. The primary advantage of RSA public-key cryptography is increased security and convenience. Private keys never need to transmitted or revealed to anyone.

  2. System I designed in order to produce a promotion package for her newly formed ...

    troubleshooting guide for new users Microsoft Access * Wizard for guidance of structuring techniques * Easy to do datasheets * Gives you the option of creating your database in design view or on the datasheet itself * Checks any spelling errors * Automatically stores created documents * East to change

  1. Analysis of Johnson Music

    This would allow for interaction between the observer and the people being observed. An advantage of this type of observation is that when a problem is spotted or if the observer has any questions, then the observer is able to talk to whoever is being observed to find out more information.

  2. You need to discuss the advantages and disadvantages of someone in your

    is where the computer temporarily stores data on its way to or from the processor. Named for its role, random access memory allows you to perform random acts, such as launching an application or making changes to a file, with the speed you demand.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work