transmission of nerve impulse

 

Transmission of nerve impulse

Transmission of impulse (action potential) from one neuron to another.

A nerve impulse (action potential) activates volatge hated calcium ion channels on axon, causing Ca+ ions inflow into axon terminal.

Increase in Ca+ concentration stimulate release of neurotransmitter acetylcholine from axon terminal into synaptic cleft.

(Neurotransmitter bind to receptor)

Acetylcholine diffuses across synaptic cleft at neuromuscular junction and binds to next neuron dendrites sites on motor-end plate and open Na+ channel and depolarisation start.

Then opening of Na+ and K+ channel (channel of protein in plasma membrane involve

 transporting ions across membrane ion channels).

Myelinated nerve fiber which attach to neuromuscular junction. There is one neuromuscular junction for each fibre.

At resting, polarised state, resting membrane potential is -70mv

When sodium rushes in and potassium rushes out, flow of Na+ into is greater than flow of K+ ion out.

The resulting changes in concentration of Na+ and K+ ions cause depolarization (+50mv).

(To pass information impulse cell inside +ve should be)

When potential reach threshold potential (-60mv), sodium ions flow in with rush (-50mv)

Now to get polarity again- repolarisation occurs

Potassium ion channels open and sodium get closed.

Flow of K+ ion outside the cell, and ionic concentration has different.

To maintain original state now Na+/ K+ pump working. Na+/K+ pump which uses energy generate ATP to actively transport ions across the membrane.

Sodium is transported outside the cell and K+ is transported back into the cell. 

One cycle of pump transport 3 sodium ions out side the cell and bring 2 potassium ion inside the cell.

Returns backwards it's resting state.

Synapses and Neurotransmitter

There is always more than one neuron involved in transmission of nerve impulse from its origin to destination.

There is no physical contact between these neurons, the point at which nerve impulse passes from one to another neuron called synapses.

There are certain agent which are responsible for transmission of nerve impulse from one neuron to another. They are neurotransmitter.

Neurotransmitters are released in synaptic cleft.

The neurotransmitter in brain and spinal codes include - 

Noreadrenaline ( norepinephrine)

Adrenaline (epinephrine)

Dopamine

Histamine

Serotonin

Acetylcholine

Noradrenaline or norepinephrine are responsible for contraction of smooth muscle of Heart and gland which will help in cardiac contraction and secreting.

 adrenaline or epinephrine also help with smooth muscle contraction of heart and gland.

Acetylcholine is responsible for the skeletal muscle contraction.