New Neuron Knowledge

1. New Neuron Knowledge By Andi Gerleman, Ailey Naugle, Ryan Austin, and Luke Brown

2. Facts • The average human being contains as many as 100 billion neurons • All neurons are specialized to receive and transmit information • Like other cells, the neuron’s cell body is made up of a nucleus, which contains a complete set of chromosomes and genes, cytoplasm, and the cell membrane

3. Parts of a Neuron

4. Parts of a Neuron • Dendrites - Short fibers that branch out from the cell body and pick up incoming messages • Axon – Single long fiber extending from the cell body that carries outgoing messages. They can vary in length from 1-2 millimeters to 3 feet. • Myelin sheath – White fatty covering found on some axons. It provides insulation so that signals from adjacent neurons do not interfere with each other.The myelin sheath also increases the speed at which signals are transmitted. • Axon terminal button – Releases neurotransmitters into the synaptic space

5. Types of Neurons • Sensory neurons – Neurons that carry messages from sense organs to the spinal cord or brain • Motor neurons – Neurons that carry messages from the spinal cord or brain to the muscles and glands • Interneuron – Neurons that carry messages from one neuron to another

6. Resting vs. action potential • Resting potential – Electrical charge across a neuron membrane due to excessive positive ions concentrated on the outside and excessive negative ions on the inside • Action potential – The firing of a nerve cell.Sudden, massive change in charge in the neuron. Occurs when depolarization reaches the threshold of excitation.

7. Additional vocabulary • Glial cells – Cells that form the myelin sheath; they insulate and support neurons by holding them together, removing waste products, and preventing harmful substances from passing the bloodstream into the brain. • All-or-none law – Principle that the action potential in a neuron does not vary in strength; the neuron either fires at full strength or it does not fire at all. • Absolute refractory period – A period after firing when a neuron will not fire again no matter how strong the incoming message may be. • Relative refractory period – A period after firing when a neuron is returning to it’s normal polarized state and will fire again only if the incoming message is much stronger than usual.

8. Synaptic space • Tiny gap between the axon terminal of one neuron and the dendrites or cell body of the next neuron.

9. INJURY to neurons • If a neuron is damaged, one becomes slightly less functional; however thousands of neurons are killed every day, and up to twice as many are lost during alcohol consumption or drug use. • It is possible that if enough neurons are damaged this could affect the central nervous system. If the central nervous system is damaged enough, it could result in paralyses or death. • You have billions of neurons, so generally killing or damaging neurons has little to no effect on the body

10. Neuron Diseases • Motor neuron disorder is defined as when neurons are incorrectly transferred and one loses voluntary muscle movements. • Symptoms or motor neuron disorders include uncomfortable twitching; difficulty swallowing, stiffness, movements become slow and effortful, and tendons relax. • Nearly all Neuron disorders result in death, with a 25% survival rate. • Disorders such as ALS (Amyotrophic lateral sclerosis) are hereditary, and effect 5 in 100,000 people. • Symptoms develop in children and adults, even after age 40.