Physiology of Neurons
Nerve stimulation; generation of action potential
Communication by neurons depend on 2 basic properties-
1. Their electrical voltage, called resting membrane potential across membrane.
2. Their plasma membrane contains variety of ion channel (pores) that may open and close.
Resting membrane potential
Resting neuron is one that doesn't conducting nerve impulse but electrically charged.
1. At rest; polarised state
Resting membrane potential; -70mv
Relatively leaky K+ channel.
Open ion channels
Plasma membrane of Neuron is selectively permeable to Na+, K+, Cl- ion through voltage gate Na+ and K+ open gate.
At resting state Na + channel is closed, while some channel of K+ is opened, maximum K+ channel closed.
At resting stage to maintain potential difference (-70mv) sodium potassium pump working. (difference between electrical charge between inside and outside.)
Pump bind ATP energy with 3 Na+ ions inside and outside bind 2 K+ ions and rotate.
Na+ goes outside and K+ come inside.
At resting state condition in extracellular more Na+ ion should present and in intracellular more K+ should be present.
Action potential
To change in electrical potential associated with passage of impulse along the membrane of muscle cell or nerve cell.
Mechanism of nerve impulse
2. Action potential; depolarisation; to send information forward to brain.
Potassium channel as it is, but open sodium channel
As information comes,
Na+ channel get open
Threshold potential; -60mv
Action potential; +50mv
In outside more Na+ present, and diffuses inside and increase positivity and changes negative potential.
Polarity end - Depolarization
To get polarity again - Repolarization - bring cell back to resting potential
3. As action potential
Sodium channel close, potassium channel open.
Passes potassium, channel gate open
Repolarization
Sodium gate closed and potassium gate open
Repolarization done but ionic concentration get different outside K+ and inside Na+.
Now sodium potassium pump working to maintain original state.
Refractory period
Period of time during which excitable cell cannot generate another action potential is called refractory period.
Hyperpolarisation
Make cell more negative than its resting membrane potential.
Occurs when membrane potential increase, becoming more negative than the resting potential.
For example; Charge from -70mv to -80mv is hyperpolarization. To maintain original state Na+ -K+ pump working.
Transmission of impulse or action potential is due to movement of in ion (sodium, potassium) across the nerve cell membrane.
Action potential continue to move forward.
0 Comments