What makes neurons different than other cells

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Continue reading with a Scientific American subscription. Subscribe Now You may cancel at any time. Neurotransmitters can excite the postsynaptic neuron, causing it to generate an action potential of its own.

Electrical synapses can only excite. They occur when two neurons are connected via a gap junction. This gap is much smaller than a synapse, and includes ion channels which facilitate the direct transmission of a positive electrical signal. As a result, electrical synapses are much faster than chemical synapses.

However, the signal diminishes from one neuron to the next, making them less effective at transmitting. Neurons vary in structure, function, and genetic makeup. Given the sheer number of neurons, there are thousands of different types, much like there are thousands of species of living organisms on Earth. In terms of function, scientists classify neurons into three broad types: sensory, motor, and interneurons.

Sensory neurons are triggered by physical and chemical inputs from your environment. Sound, touch, heat, and light are physical inputs. Smell and taste are chemical inputs. For example, stepping on hot sand activates sensory neurons in the soles of your feet. Those neurons send a message to your brain, which makes you aware of the heat. Motor neurons play a role in movement, including voluntary and involuntary movements.

These neurons allow the brain and spinal cord to communicate with muscles, organs, and glands all over the body.

There are two types of motor neurons: lower and upper. Lower motor neurons carry signals from the spinal cord to the smooth muscles and the skeletal muscles. Upper motor neurons carry signals between your brain and spinal cord. When you eat, for instance, lower motor neurons in your spinal cord send signals to the smooth muscles in your esophagus, stomach, and intestines. These muscles contract, which allows food to move through your digestive tract.

Interneurons are neural intermediaries found in your brain and spinal cord. Some neurons have short axons, while others can be quite long. The longest axon in the human body extends from the bottom of the spine to the big toe and averages a length of approximately three feet! How do neurons transmit and receive information?

In order for neurons to communicate, they need to transmit information both within the neuron and from one neuron to the next. This process utilizes both electrical signals as well as chemical messengers. The dendrites of neurons receive information from sensory receptors or other neurons. This information is then passed down to the cell body and on to the axon.

Once the information has arrived at the axon, it travels down the length of the axon in the form of an electrical signal known as an action potential. Once an electrical impulse has reached the end of an axon, the information must be transmitted across the synaptic gap to the dendrites of the adjoining neuron. In some cases, the electrical signal can almost instantaneously bridge the gap between the neurons and continue along its path.

In other cases, neurotransmitters are needed to send the information from one neuron to the next. Neurotransmitters are chemical messengers that are released from the axon terminals to cross the synaptic gap and reach the receptor sites of other neurons. In a process known as reuptake, these neurotransmitters attach to the receptor site and are reabsorbed by the neuron to be reused.

Neurotransmitters are an essential part of our everyday functioning. While it is not known exactly how many neurotransmitters exist, scientists have identified more than of these chemical messengers. The following are just a few of the major neurotransmitters, their known effects, and disorders they are associated with.

Acetylcholine: Associated with memory, muscle contractions, and learning. Endorphins: Associated with emotions and pain perception. The body releases endorphins in response to fear or trauma. These chemical messengers are similar to opiate drugs such as morphine but are significantly stronger. Dopamine: Associated with thought and pleasurable feelings. One category is dopamine agonists, which mimic the effects of dopamine. Another type of agent is levodopa, which is converted into dopamine in the brain.

More than that, their interactions define who we are as people. The creation of new neurons in the brain is called neurogenesis , and this can happen even in adults. A useful analogy is to think of a neuron as a tree. A neuron has three main parts: dendrites , an axon , and a cell body or soma see image below , which can be represented as the branches, roots and trunk of a tree, respectively. A dendrite tree branch is where a neuron receives input from other cells.

Dendrites branch as they move towards their tips, just like tree branches do, and they even have leaf-like structures on them called spines.

The axon tree roots is the output structure of the neuron; when a neuron wants to talk to another neuron, it sends an electrical message called an action potential throughout the entire axon. There are different types of neurons , both in the brain and the spinal cord.

They are generally divided according to where they orginate, where they project to and which neurotransmitters they use.