The Nervous System

The Nervous System By: Jen Pote and Megan Gallagan

Major Divisions of Brain • Cerebrum • Outer layer of gray matter • Neuronal cell bodies, dendrites • Higher functions (language, abstract thought) • Cerebellum • Attached to brain stem, part of hindbrain • Fine motor coordination/body movement, posture, and balance • Medulla (brain stem) • Part of hindbrain • Controls heart rate, constriction/dilation of blood vessels, respiration, and digestion

Functional Lobes of Cerebrum • Occipital: • Responsible for receiving/processing VISUAL info. • Temporal: Responsible for processing AUDITORY signals • Parietal: Processes information about touch, taste, pressure, pain, cold, and heat • Frontal: Responsible for motor activity, speech, and thought processes

The Neuron • Humans have about 100 billion neurons in their brain • Neurons have three main parts: • Dendrites (short, highly branched fibers that receive information from another cell and pass it on to the cell body) • Cell body (contains nucleus, mitochondria, cytoplasm, and organelles) • Axon (long fibers that conduct messages away from the cell body)

The Neuron

Types of Neurons • Motor Neurons • Transmit messages FROM central nervous system TO muscles/glands • i.e. brain sends message to hand to touch desk • Sensory Neurons: • Carry messages FROM sensory receptors TO the central nervous system • i.e. hand feels desk sends message to brain which recognizes what is being touched and what it feels like. “this is a desk!” • Interneurons • connect neuron to neuron • Like the game Telephone. Neurons must pass the message to other neurons that eventually get the message to the desired destination

Nervous Tissue • Neurons- transmit nerve messages • Glial Cells- Serve as support cells and help protect neurons • Astrocytes- type of Glial cell. Provides support for the endothelial cells, provide nutrients to the nervous tissue, maintains balance of ions, and helps with the repairing and scarring process after brain and spinal cord injuries

Nerves • A nerve is an enclosed cable-like bundle of axons. • Provide common pathways for nerve impulse transmissions

Impulse Transmission • When neurons are at rest (not transmitting messages) they maintain a “resting membrane potential” • This is when the cytoplasmic fluid next to the membrane is negatively charged and the interstitial fluid outside the membrane is positive. • When a message needs to be sent signals are sent to the dendrite and the neuron is stimulated by “action potential” • A brief voltage reversal across the plasma membrane • When the voltage in that area of the neuron reaches a threshold level the action potential triggers the voltage reversal along the rest of the neuron. This creates a chain reaction: dendrite>cell body>axon>dendrite of the adjacent neuron

Head Injury • Head injury-injury that can occur to the scalp, skull, brain, and underlying tissue and blood vessels in the head. • Brain Injury- injury that disrupts the function of the brain • Can be caused by a blow, jolt, or penetration to the head • Can be mild to severe • Can result in short term problems or long term problems

Types of Head Injury • Concussion- injury to the head that can cause instant loss of awareness or alertness. The concussion is temporary but may result in permanent damage • Skull fracture- a break in the skull bone. Four major types: • Linear-break but does not move bone. • Depressed-part of skull is sunken in • Diastatic- fracture that occurs along areas between the bones • Basilar-most serious type. Break in the bone at the base of the skull. • Intracranial hematoma- blood clots in or around the brain

Jeffrey’s Story • My Uncle Jeff- in 1967 while he was riding his bike he was hit head on by a car. His brain stem (Medulla) was damaged, his jaw shattered, and he went immediately into a deep coma • Coma: a profound state of unconsciousness. Person cannot be awakened and does not respond to pain, light, or sound.

Jeffrey’s Story • Jeff was in a coma for four months with no response • Doctors said he would die and if by some chance he survived he would be a vegetable • While in the coma they put him in ice water mats to keep body temperature low and to make sure the brain didn’t swell • Jeff was not really moved around contrary to today’s treatment where patient’s muscles are moved to prevent atrophy • Four months later Jeff awoke and entered into a semi-coma • He was responsive: blinked once for yes, etc. could not talk • Fell in and out of consciousness • Recognized family, etc. • Could not sit up or move

Jeffrey’s Story • Once in semi-coma he was moved to a rehabilitation hospital • Jeff remembered certain information such as his best friend’s phone number • Had to re-learn how to talk, eat, and sit up. But it came back quickly • Had to build up muscle again • Speech therapy-Jeff’s speech was permanently damaged • When Jeff’s brain stem was injured the messages that are sent from his brain to his body telling it to move were damaged. Today Jeff does not have control over his legs or his left arm.

Common Diseases of the Brain • Alzheimer's • Cause is still unknown • Formation of round senile plaques • Causes loss of memory and inability to carry out daily procedures such as dressing or eating • Increases rapidly. Lifespan with disease is usually 5 years

Common Diseases of the Brain • Parkinson’s • Movement disorder that occurs when brain cells that make the neurotransmitter Dopamine die over time • Symptoms: shaking, slow movement, freezing in place, soft voice, difficulty with facial expression, and stiff limbs • Treatment: medication to replace Dopamine loss

Common Diseases of the Brain • Stroke • Blood flow is interrupted by a clot. Oxygen and nutrient flow is cut off • Causes brain cells to die • Treatment: preventative “clot busting” drugs

Common Diseases of the Brain • Depression • Medical disorder in which sadness persists and interferes with day to day activities • Symptoms: loss of energy and enthusiasm, inability to concentrate, changes in sleep patterns and appetite, memory loss, crying spells, social withdrawal, physical pains and sometimes suicidal thoughts • Treatments: therapy and drugs

Brain Abscesses • A collection of immune cells, pus, and other materials in the brain, usually caused by a bacterial or fungal infection • Inflammation response to infection: immune response • Even though immune responses are meant to help the body, it can also be harmful to the body because as abscesses are formed, the brain swells and since the skull is unable to expand, pressure is put on the brain tissue, and infected material can block the blood vessels of the brain

Spinal Cord • A long, thin, tubular bundle of nervous tissue and support cells extending from the brain • Protected by bones which make up the vertebral column • Surrounded by Cerebral Spinal Fluid, which acts as a cushion to protect nerve tissues • Spinal nerve runs through the entire spinal cord and corresponds with respective areas of the body (the top controls sensation in the upper body) • Damage to spinal cord can cause paralysis and loss of sensation

Breakthroughs-Gene Therapy • Doctor Patrick Aubourg (from France) was able to recognize the gene that was effected by a fatal neurological disease called ALD • Recently, using gene therapy he was also able remove the damaged gene, repair it, and re-insert the gene into patients during the early stages of ALD

Memory • Short term- located in the pre-frontal lobe. (I ate macaroni and cheese yesterday) • Long term-located in the inner fold of the temporal lobe (when I was five years old I ate macaroni and cheese every day)

Brain Fact • The left side of our brain controls the right side of our body • The right side of our bran controls the left side of our body

Sources • http://thebrain.mcgill.ca/ • http://www.bio.davidson.edu/courses/anphys/2000/Rigel/Impulse%20Transmission%202.htm • http://www.biausa.org/aboutbi.htmhttp:// • www.healthsystem.virginia.edu/uvahealth/adult_neuro/headinj.cfm • http://www.umm.edu/ency/article/000783.htm • http://www.apparelyzed.com/spinalcord.html • http://www.npr.org/templates/story/story.php?storyId=120118988

The Nervous System