Nerve cell

• Neurons are also called nerve cells and are the basic unit of the nervous system
• There are billions of neurons in the body, some exist alone while others are joined together to form organs like the brain and spinal cord
• One part of the brain alone can have 12 to 14 billion neurons
• Parts of a neuron:

  • Cell body contains the nucleus
  • Dendrites carry impulses toward the cell body, with a single dendrite able to be over one meter long and a cell may have up to 200 dendrites
  • Axons carry impulses away from the body, passing impulses to the dendrites of other neurons or the cell body of muscle cells. Axons can be grouped together into cable-like bundles called nerves
• Neurons have the special ability to carry signals or impulses
• Thoughts, emotions, learning, and many body functions are created by nerve impulses in neurons
• A nerve impulse is a combination of an electrical charge and chemical reaction, moving along a neuron as an electrochemical signal
• A nerve impulse cannot jump from one neuron to another
• When a nerve impulse reaches the end of an axon, it produces a chemical called neurotransmitter to be released
• The neurotransmitter crosses the space between neurons called synapse and stimulates the nerve impulse to start in the next dendrite
• The nervous system is assisted by five sense organs: eyes, ears, nose, tongue, and skin
• Sense organs constantly receive information from the environment and send messages to the brain, aiding in the survival of human beings
• Stimulus is any factor in the environment that may trigger a nerve impulse
• Response is a reaction to a stimulus
• An organism must be able to respond to stimuli in order to survive
• Messages do not travel in both directions along the same neuron
• Only the axon of the neuron releases neurotransmitter that crosses the space between neurons
• Reaction time is the length of time between the application of a stimulus and the detection of a response
• Nerve cell is also known as a neuron
• Nerve cells are found in the blood vessels
• Nerves in the brain are different
• Nerve cell is the basic unit of the nervous system
• The nervous system includes the brain and spinal cord
• There are 12 to 14 billion nerve cells in one part of the brain
• Three parts of a nerve cell:

  • Cell body: contains the nucleus, which is the center of the cell
  • Dendrites: carry impulses into the cell body towards the neuron
  • Axon: carries impulses away from the cell body
• Nerve impulses carry signals related to thoughts, emotions, and learning
• Each impulse carries information and has an electrical and chemical charge
• Impulses pass from one nerve cell to another
• Impulses cannot jump from one nerve cell to another
• At the end of a nerve cell, there is a gap called a synapse where a chemical (neurotransmitter) is produced
• Sense organs are constantly receiving information from outside the body
• The brain interprets the information received from the sense organs
• Stimulus may trigger an impulse (e.g., getting hurt sends a message of pain)
• Response is the interpretation of the brain to the stimulus
• There is always a response to a stimulus
• Messages do not travel in both directions in nerve cells
• Only the axon of a nerve cell releases neurotransmitters
• Reaction time is the length of time it takes for a response to a stimulus
• Our responses are fast because impulses can travel very quickly