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Nerve impulses are the electrical signals that travel through your nervous system. They carry information from your brain to your muscles, telling them when to contract. But how do these impulses travel through your neurons?
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Introduction
Nerve impulses are generated by special groups of cells called neurons. Each neuron consists of a cell body, dendrites, and an axon (see Figure 1). The cell body contains the nucleus, which houses the genetic material for the cell. The dendrites are short processes that arise from the cell body. Dendrites receive information from other neurons and conduct signals toward the cell body. The axon also arises from the cell body and is much longer than the dendrites. The axon conducts signals away from the cell body to other neurons or muscle cells.
The structure of a neuron
Neurons are cells that transmit nerve impulses. A nerve impulse is an electrical signal that travels through the nervous system. The nervous system is made up of two parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS is made up of the brain and the spinal cord. The PNS is made up of all the nerves that branch out from the spinal cord to the rest of the body.
There are three types of neurons: sensory neurons, motor neurons, and interneurons. Sensory neurons are responsible for sending information from the senses to the CNS. Motor neurons are responsible for sending information from the CNS to the muscles. Interneurons are responsible for sending information between neurons.
All three types of neurons have three parts: dendrites, a cell body, and an axon. Dendrites are tree-like structures that receive information from other neurons. The cell body is responsible for processing this information. The axon is a long, thin structure that transmits information to other cells.
The structure of a neuron allows it to transmit nerve impulses quickly and effectively. When a stimulus, such as a touch or a sound, enters one of the dendrites, it triggers an electrical signal in the cell body. This signal travels down the axon to the terminals, where it triggers a chemical reaction that passes the signal on to other cells.
How a nerve impulse is generated
Nerves are made up of long, thin fibers called axons that protrude from the body of the neuron. When an impulse starts at the dendrites, it travels down the length of the axon to the axon terminals. The nerve impulse then causes a release of neurotransmitters, which pass the message on to the next neuron.
How a nerve impulse is conducted
Neurons are specialized cells that transmit nerve impulses. Nerve impulses are generated by the movement of ions across the cell membrane, and they are conducted from the cell body to the axon terminal by the axon. The axon is a long, thin extension of the neuron that transmits impulses from the cell body to the axon terminal.
At the point where the axon meets the cell body, there is a gap called the synapse. The synapse is bridged by specialized molecules called neurotransmitters. When an impulse reaches the synapse, it triggers the release of neurotransmitters from storage vesicles in the axon terminal. The neurotransmitters diffuses across the synapse and binds to receptors on the post-synaptic membrane, which initiates an impulse in the post-synaptic neuron.
How a nerve impulse is transmitted
Nerve impulses are generated by special cells called neurons. Each neuron has a cell body, which contains the nucleus and other important organelles. The cell body is where most of the metabolic activity of the cell takes place. Nerve impulses are generated in the cell body and then travel down the length of the cell.
The part of the cell that conducts the nerve impulse is called an axon. Axons can be very long, and they are often wrapped in a myelin sheath. The myelin sheath is a lipid-rich layer that insulates the axon and speeds up conduction of the nerve impulse.
At the end of the axon, there are sites called synapses where nerve impulses are passed from one neuron to another. The space between two neurons at a synapse is called a synaptic cleft. In order for an impulse to be transmitted across a synaptic cleft, a chemical called a neurotransmitter must be released into the gap.
The role of myelin in nerve impulse conduction
Myelin is a white, fatty substance that covers and protects the axons of many neurons. Myelin is composed of lipids and proteins, and it forms a layer around the axon in a manner similar to the way electrical insulation surrounds a copper wire. Each myelin sheath is wrapped around the axon in spiral fashion, with each successive layer enclosing a segment of the axon that is slightly longer than the preceding segment. The gaps between adjacent myelin sheaths are called nodes of Ranvier.
The role of the axon terminal in nerve impulse transmission
The axon terminal is the specialized ceullar structure at the end of an axon that is responsible for the transmission of nerve impulses. The axon terminal is typically founnd at the synapse, which is the point of communication between two neurons. When a nerve impulse arrives at the terminals, it triggers the release of neurotransmitters, which then cross the synapse and bind to receptors on the postsynaptic cell. This process results in the depolarization of the postsynaptic cell membrane and initiates an action potential.
The synapse
The synapse is the site of communication between neurons. A nerve impulse arriving at the terminal button of one neuron can cause an electrical change in the membrane of the adjacent neuron. This change, called an action potential, propagates along the membrane until it reaches the next synapse.
The refractory period
When a neuron is stimulated, an electrical impulse, or action potential, is generated. This action potential propagates down the length of the axon to the synaptic terminals, where it triggers the release of neurotransmitters. The neurotransmitters then bind to receptors on the post-synaptic cell and cause another action potential to be generated. This process repeats itself until the action potential reaches its target.
The flow of electrons through the neuron during an action potential is extremely fast, but it is not instantaneous. There is a brief delay between the time when the first electron enters the axon and when the last electron exits. This delay is called the refractory period.
During the refractory period, the neuron cannot respond to another stimulus even if it is strong enough to generate an action potential. This ensures that action potentials always travel in one direction and that they do not backfire.
Summation
In order for a neuron to generate an action potential, the cell must first reach what is known as the threshold potential. This occurs when the neuron’s membrane potential is raised to a certain level by a process called summation. There are two types of summation: spatial summation and temporal summation.
