How fast nerve impulse travel

Two potassium ions from outside the cell then bind to the transport protein and as the phospate is removed, the protein assumes its original shape and releases the potassium ions inside the cell.

If the pump was to continue unchecked there would be no sodium or potassium ions left to pump, but there are also sodium and potassium ion channels in the membrane.

Concentration of ions inside and outside the neurone at rest:. This imbalance of ions causes a potential difference or voltage between the inside of the neurone and its surroundings, called the resting membrane potential. The membrane potential is always negative inside the cell, and varies in size from —20 to — mV milivolt in different cells and species in humans it is —70mV. An action potential occurs when a neurone sends information down an axon.

This involves an explosion of electrical activity, where the nerve and muscle cells resting membrane potential changes. In nerve and muscle cells the membranes are electrically excitable , which means they can change their membrane potential, and this is the basis of the nerve impulse. The sodium and potassium channels in these cells are voltage-gated , which means that they can open and close depending on the voltage across the membrane.

The normal membrane potential inside the axon of nerve cells is —70mV, and since this potential can change in nerve cells it is called the resting potential.

When a stimulus is applied a brief reversal of the membrane potential, lasting about a millisecond, occurs. This brief reversal is called the action potential :. An action potential has 2 main phases called depolarisation and repolarisation :. Check Point g Action Potential has two main phases: Depolarisation. A stimulus can cause the membrane potential to change a little. The voltage-gated ion channels can detect this change, and when the potential reaches —30mV the sodium channels open for 0.

The causes sodium ions to rush in, making the inside of the cell more positive. This phase is referred to as a depolarisation since the normal voltage polarity negative inside is reversed becomes positive inside. At a certain point, the depolarisation of the membrane causes the sodium channels to close. As a result the potassium channels open for 0.

Since this restores the original polarity, it is called repolarisation. The action potential only occurs if the stimulus causes enough sodium ions enter the cell to change the membrane potential to a certain threshold level. At the threshold, sodium gates open in the membrane and allow a sudden flood of sodium ions to enter the cell. If the depolarisation is not great enough to reach the threshold, then an action potential and hence an impulse will not be produced.

This is called the all or nothing law. This means that the ion channels are either open or closed; there is no half-way position. Action potentials are always the same size, however the frequency of the impulse carrying the information can determine the intensity of the stimulus, i. How do Nerve Impulses Start? Each initiates nerve impulses in sensory neurons when it is physically deformed by an outside force such as:. Touch Light touch is detected by receptors in the skin.

These are often found close to a hair follicle so even if the skin is not touched directly, movement of the hair is detected. In the mouse, light movement of hair triggers a generator potential in mechanically-gated sodium channels in a neuron located next to the hair follicle.

This potential opens voltage-gated sodium channels and if it reaches threshold, triggers an action potential in the neuron. Touch receptors are not distributed evenly over the body. The fingertips and tongue may have as many as per cm 2 ; the back of the hand fewer than 10 per cm 2. This can be demonstrated with the two-point threshold test.

With a pair of dividers like those used in mechanical drawing, determine in a blindfolded subject the minimum separation of the points that produces two separate touch sensations.

The ability to discriminate the two points is far better on the fingertips than on, say, the small of the back. The density of touch receptors is also reflected in the amount of somatosensory cortex in the brain assigned to that region of the body. Proprioception is our "body sense". It enables us to unconsciously monitor the position of our body.

But what about the speed of thought? To quantify the speed of anything, one needs to identify its beginning and end. The distinction between, and independence of, each of these processes is blurry. But we have to set our start- and endpoints somewhere to have any hope of tackling the question. There are many different kinds of thoughts that can vary greatly in timescale. Consider the differences between simple, speedy reactions like the sprinter deciding to run after the crack of the starting pistol on the order of milliseconds [ms] , and more complex decisions like deciding when to change lanes while driving on a highway or figuring out the appropriate strategy to solve a math problem on the order of seconds to minutes.

It relies on interactions across complex networks of neurons distributed throughout the peripheral and central nervous systems. Researchers can use imaging techniques, such as functional magnetic resonance imaging and electroencephalography , to see what areas of the nervous system are active during different thought processes, and how information flows through the nervous system.

Many scientists consider the best proxy measure of the speed or efficiency of thought processes to be reaction time — the time from the onset of a specific signal to the moment an action is initiated. Indeed, researchers interested in assessing how fast information travels through the nervous system have used reaction time since the mids.

This approach makes sense because thoughts are ultimately expressed through overt actions. Reaction time provides an index of how efficiently someone receives and interprets sensory information, decides what to do based on that information, and plans and initiates an action based on that decision. The time it takes for all thoughts to occur is ultimately shaped by the characteristics of the neurons and the networks involved.

Many things influence the speed at which information flows through the system, but three key factors are:.

The speed with which nerves transport impulses is being studied by many people. Communication with the brain and how the brain processes the received information is still very mysterious.

But scientists have an idea how fast nerves send signals. A larger time component is the delay between an impulse and the actual transmission of that response by your nerves. And that is what nerve damage is about.