Advanced nervous systems - general trend in evolution, Biology

Advanced Nervous Systems - General Trend In Evolution

In higher groups of animals you will observe clear trends towards centralisation of the nervous system, to maximize effectiveness. The diffuse peripheral network becomes less conspicuous or not recognizable giving place to nerves made up of nerve fibers. The motor neurons and association neurons become mainly concentrated and centralised into masses known as ganglia. The increasing dominance of the association neurons that are the links in reflex pathways, makes possible more complex central pathways that form the structural basis of advances in integration. The sensory neurons become relegated to the periphery. This results in differentiation of functional tracts of neurites and nerves by which stimuli are brought to and carried out of the central nervous system. Thus better association or integration of afferent sensory stimuli along with meaningful efferent motor outputs become possible, resulting in more intricate and capable behavioral patterns. Perikarya become limited to the rind or cortex of the ganglia, the interior being made up of nerve fiber mass called neuropile where conspicuous pathways or tracts already evident in the lower groups, become developed. The development of giant fiber system associated with the central nervous system further improves the efficiency resulting in enhanced speed of propagation of impulse and hence efficiency of response to stimuli. With one end of the animal always directed forward throughout locomotion, an anterior end and bilateral symmetry become established. The anterior end becomes more significant with most sensory organs becoming associated with this end. Naturally, the ganglia become better developed and much more highly organized in this region, giving rise to the structurally and physiologically more complicated brain dominating over the whole organism. This is the direct result of cephalisation.

Posted Date: 2/4/2013 6:43:20 AM | Location : United States







Related Discussions:- Advanced nervous systems - general trend in evolution, Assignment Help, Ask Question on Advanced nervous systems - general trend in evolution, Get Answer, Expert's Help, Advanced nervous systems - general trend in evolution Discussions

Write discussion on Advanced nervous systems - general trend in evolution
Your posts are moderated
Related Questions
SALI V A R Y GLAND - These are compound - Alveolar, tubular glands made up of columnar / cuboidal epithelium. Saliva is manufactured in them. In mammals these are pai

Q. How is the striped pattern of the striated muscle cells formed? The functional units of the muscle fibers are the sarcomeres within the sarcomeres blocks of myosin and actin

Q. What is the life cycle of ascaris? The Adult ascaris that live within the human intestine can release up to 200 thousand eggs a day. The eggs are eradicating with human fece

In the human body, the potassium ion can pass easily through cell membranes, yet the potassium ion concentration is higher inside many cells than it is outside these cells. Could t

Peak Flow Velocity  fs  derived  from Doppler  shift by  rearranging Doppler equation: V = C/2 x ΔF/Fo Various  information can be obtained from spectral display

Define Japanese criteria for functional foods? The Japanese criteria for functional foods include: They are food (not capsules, pills/powder) on the basis of naturally o

The conduction of impulse in a nerve fibre is. a electrochemical process. Maximum speed of transmission of nerve impulse can be 13 metre/second due to axoplasm is much resistant to

What is the difference between transcription and translation? Transcription is the name given to the formation of RNA molecules from an open DNA chain used as a template. Trans

Define Sample Titration for Estimation of Vitamin c in Lemon Juice? Cut the lemon into two halves with a stainless steel knife. Remove the seeds. Squeeze the juice from half a

Q. What are few mechanisms by which pathogenic bacteria cause diseases? And why is this knowledge important? Pathogenic bacteria have characteristics called as virulence factor