nerve impulse

(noun)

the signal transmitted along a nerve fiber, either in response to a stimulus (such as touch, pain, or heat), or as an instruction (such as causing a muscle to contract)

Related Terms

Examples of nerve impulse in the following topics:

  • The Ear

    • The ear is the sensory organ that picks up sound waves from the air and turns them into nerve impulses that can be sent to the brain.
    • The ear is the sensory organ that picks up sound waves from the surrounding air and turns them into nerve impulses, which are then sent to the brain.
    • In this way sound waves are transformed into nerve impulses.
    • The nerve impulses travel from the left and right ears through the eighth cranial nerve to both sides of the brain stem and up to the part of the cerebral cortex dedicated to sound (auditory cortex, located in the temporal lobe).
    • Describe how sound waves are collected and transformed into nerve impulses

  • Structure of a Nerve

    • A nerve provides a structured pathway that supports the electrochemical nerve impulses transmitted along each of the axons.
    • A nerve conveys information in the form of electrochemical impulses (known as nerve impulses or action potentials) carried by the individual neurons that make up the nerve.
    • These impulses are extremely fast, with some myelinated neurons conducting at speeds up to 120 m/s.
    • The impulses travel from one neuron to another by crossing a synapse, and the message is converted from electrical to chemical and then back to electrical.
    • Thus they are synonymous with afferent nerves.

  • Electric Potential in Human

    • In humans, they are seen in cell membranes and nerve impulses in particular.
    • When the brain decides on an action, it sends an impulse that cascades to the extremity where a muscle contracts.
    • Neurons receive an impulse at the dendrites.
    • Neurons receive an impulse at the dendrites.
    • This impulse is passed through the axon, a long extension of the cell, in the form of an electrical potential created by differing concentrations of sodium and potassium ions on either side of a membrane in the axon.

  • Nerve Conduction and Electrocardiograms

    • There are three major functions of nerves.
    • Nerve conduction is a general term for electrical signals carried by nerve cells.
    • How does it get transmitted along the cell membrane as a nerve impulse?
    • Thus the action potential stimulated at one location triggers a nerve impulse that moves slowly (about 1 m/s) along the cell membrane.
    • Just as nerve impulses are transmitted by depolarization and repolarization of an adjacent membrane, the depolarization that causes muscle contraction can also stimulate adjacent muscle cells to depolarize (fire) and contract.

  • Signal Summation

    • Each neuron connects with numerous other neurons, often receiving multiple impulses from them.
    • However, if the neuron receives as many inhibitory as excitatory impulses, the inhibition cancels out the excitation and the nerve impulse will stop there.
    • Spatial summation means that the effects of impulses received at different places on the neuron add up so that the neuron may fire when such impulses are received simultaneously, even if each impulse on its own would not be sufficient to cause firing.
    • Temporal summation means that the effects of impulses received at the same place can add up if the impulses are received in close temporal succession.
    • Thus, the neuron may fire when multiple impulses are received, even if each impulse on its own would not be sufficient to cause firing.

  • Characteristics of Nervous Tissue

    • Nervous tissue is the main component of the nervous system, which includes the brain, spinal cord, and nerves.
    • Neurons are highly specialized nerve cells that generate and conduct nerve impulses.
    • The axons are responsible for transmitting impulses over long distances from cell body.
    • In the peripheral nervous system, Schwann cells are neuroglia cells that support neuronal function by increasing the speed of  impulse propagation.

  • Electrical Events

    • The SA and AV nodes initiate the electrical impulses that cause contraction within the atria and ventricles of the heart.
    • The SA node is a bundle of nerve cells located on the outer layer of the right atria.
    • The SA node nerve impulses travel through the atria and cause muscle cell depolarization and contraction of the atria directly.
    • The SA node impulses also travel to the AV node, which stimulates ventricular contraction.
    • The system of nerves that work together to set the heart rate and stimulate muscle cell depolarization within the heart.

  • Function and Physiology of the Spinal Nerves

    • The peripheral nervous system includes 12 cranial nerves and 31 pairs of spinal nerves, which provide communication from the CNS to the rest of the body by nerve impulses that regulate the functions of the human body.
    • Spinal nerve C1 (suboccipital nerve): Provides motor innervation to muscles at the base of the skull.
    • These include the greater occipital nerve which provides sensation to the back of the head, the lesser occipital nerve which provides sensation to the area behind the ears, the greater auricular nerve, and the lesser auricular nerve.
    • The phrenic nerve arises from nerve roots C3, C4, and C5.
    • PNS nerves are involved in the erection of genital tissues via the pelvic splanchnic nerves 2–4.

  • Stages of the Action Potential

    • Neural impulses occur when a stimulus depolarizes a cell membrane, prompting an action potential which sends an "all or nothing" signal.
    • Neural impulses from sensory receptors are sent to the brain and spinal cord for processing.
    • During the refractory phase this particular area of the nerve cell membrane cannot be depolarized.
    • Damage to the myelin sheath from disease can cause severe impairment of nerve-cell function.
    • In addition, some poisons and drugs interfere with nerve impulses by blocking sodium channels in nerves.

  • Optic (II) Nerve

    • The optic nerve (cranial nerve II) receives visual information from photoreceptors in the retina and transmits it to the brain.
    • The optic nerve is also known as cranial nerve II.
    • Each human optic nerve contains between 770,000 and 1.7 million nerve fibers.
    • As a consequence, optic nerve damage produces irreversible blindness.
    • It also conducts the visual impulses that are responsible for two important neurological reflexes: the light reflex and the accommodation reflex.