excitbility : a single nerve fiber can be excited or stimulated by using differend types of stimulus like electrical, thermal, mechanical and chemical. electrical stimulant is mostly used because its strength & duration is strictly maintained. a) strength of stimulus : a minimun strength of stimulus is required for the stimulation of nerve fiber. beleow this level it is unaffected. duration of stimulus : this stimulus should be applied a certain period of time. below this there is no respons. c)nutration & oxygen supplement : nerve fibers need some energy which is obtained from nutration & oxygen suppldment. d)direction of application of stimulus : normally two directions are found . it the stimulus is applied according to the length of nerve fibre then we get the maximum application & vice verse . e.g. hit of a wood piece gives less pain in then a poke of a needle. e) inoganic ion level: excitability mainly depends on na+ k+ ca++ loack of ca++ increases the excitability when na+ & k+ level increases then excitability f) pathological condition: in somed pathological condition like damage or injury nerve fiber then the excitability increases. conductivity : like nerve fibers the neurofibrils. contain some conductivity. here direction of conduction is always one the way wiug sone velocity : a)temperature : when temperature increases then conduction increases & when temperature decreases then conductivity decreases. so condu < tempe. b)inorganic ion concentration : na, k,ca, ion increasds the conduc. c) ph level : when ph level increases then contuctivits decreases. so conduc propotional to ph level d. supplement of nutration : if the supplement of nutration is totally cut off then all the properties of nerve fiber are lost & there is no conductivity. e.oxygen supply : if the is no supply of oxygen then the conductivily & excitability finally stops.
Posted on: Tue, 18 Jun 2013 03:23:31 +0000
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