| Term | Definition |
|---|
| neurons | nerve cells that carry impulses between various parts of the body |
| sensory neuron | a nerve cell that carries messages from the senses to the central nervous system |
| motor neuron | a nerve cell that carries messages from the brain and spinal cord to the muscles |
| dendrite | the part of a neuron that receives messages from other neurons |
| impulse | an electrical message passed from neuron to neuron |
| axon | the part of the neuron that receives messages from the dendrite and passes the messages to the next neuron |
| synapse | a gap between neurons where "messages" cross |
| neurotransmitters | chemicals, caused by the electrical impulse, which are released and cross the synapse to carry the message to the next sensory neuron |
| myelin sheath | the protective coating of a neuron that helps messages to travel faster from neuron to neuron |
| white matter | areas of the nervous system that have myelin sheaths |
| gray matter | areas of the central nervous system that do not have myelin sheaths |
| somatic nervous system | controls your skeletal muscle movements and helps your body adjust to its external environment |
| autonomic nervous system | controls involuntary activities such as heart rate, temperature regulation, blood pressure, breathing and digestion |
| system | a group of organs working together |
| reflex | an action that happens before the brain has time to think about the action |
| parts of a neuron | axon, dendrite |
| How many axons are in each nerve | one |
| How many dendrites are in each nerve | 10,000 |
| How many neurons are in the body | over 10 billion |
| How long is an axon | over 1 mile long |
| Peripheral Nervous System (PNS) | made up of the neurons outside the brain and the spinal cord |
| Are neurons replaced when they die | no |
| What determines the size and shape of neurons | their functions, or what their job is |
| Why are neurons unique | they communicate with each other |
| Do neurons have a nucleus, chromosomes and DNA | yes |
| What are the two parts of the PNS | Somatic nervous system and Autonomic nervous system |
| What is the main job of the somatic nervous system | helps you adjust to your external environment |
| What is the main job of the autonomic nervous system | regulates your internal system |
| Which kind of neurons does the autonomic nervous system use | motor neurons |
| How long does it take the brain to register what happens when you touch a hot stove and yank your hand away | one thousandth of a second |
| Examples of reflexes | sneezing, blinking, knee reflexes |
| photic sneezing | sneezing to bright light like sunlight |
| What kind of reflex is photic sneezing | genetic reflex |
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