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The Nervous System. http://www.brightstorm.com/science/biology/the-human-body/nervous-system/. The Nervous System. A complex network of nervous tissue that carries electrical messages throughout the body Includes Brain and Spinal cord Central Nervous System
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The Nervous System http://www.brightstorm.com/science/biology/the-human-body/nervous-system/
The Nervous System • A complex network of nervous tissue that carries electrical messages throughout the body • Includes • Brain and Spinal cord • Central Nervous System • Nerves that run throughout the body • Peripheral Nervous System
Nerve Cells • Two basic types of nerve cells • Neurons • The structural and functional units of the nervous system • Transmit electrical signals called nerve impulses • Glial Cells • Support the neurons • Provide neurons with nutrients and other materials
Neurons • Cell body – contains the nucleus and other cell organelles • Dendrites – extend from the cell body and receive nerve impulses from other neurons • Axon – long extension of the cell body that transmits nerve impulses to other cells http://www.youtube.com/watch?v=ob5U8zPbAX4&lr=1
The Myelin Sheath • The outer layer of many neurons • Myelin is a lipid produced by a type of glial cell known as a Schwann cell • Acts like a layer of insulation • Regularly spaced nodes, or gaps, in the myelin sheath allow nerve impulses to skip along the axon very rapidly
Types of Neurons • Classified based on the direction in which they carry nerve impulses • Sensory neurons – carry nerve impulses away from tissues and organs to the spinal cord and brain • Motor neurons – carry nerve impulses from the brain and spinal cord to muscles and glands • Interneurons – carry nerve impulses back and forth between sensory and motor neurons
Nerve Impulses • These are electrical in nature • Come from a difference in electrical charge across the plasma membrane of a neuron • Ions are involved in this process • Remember that these are electrically charged atoms or molecules
Resting Potential • Not actively transmitting a nerve impulse • Maintained by the sodium-potassium pump • Maintains a charge differential across the membrane Uses ATP to pump Na+ ions out of the cells and K- ions into the cell The inside of the neuron is negatively charge with the fluid surrounding the neuron is positively charge The difference is called the resting potential
Action Potential • A nerve impulse causes a sudden reversal of the electrical charge across the membrane of a resting neuron • This reversal is called the action potential • Begins with a chemical signal from another cell • Gates to the Na/K pump open allowing Na+ ions to rush back into the cell • Charges are now reverse The reversed charges causes a ripple effect down the axon as a very rapid electrical current If a myelin sheath is there these ions can only flow where there is a node
Sodium Potassium Pumps and Action Potential • http://www.youtube.com/watch?v=C_H-ONQFjpQ&lr=1 • http://www.youtube.com/watch?v=gkQtRec2464&lr=1
The Synapse • The place where an axon terminal meets another cell is called a synapse • Separated by a narrow space known as the synaptic cleft • When an action potential reaches the axon terminal, a molecule called a neurotransmitter is released • http://outreach.mcb.harvard.edu/animations/synaptic.swf
Central Nervous System • CNS – brain and spinal cord • The Brain • The most complex organ of the human body • The control center of the CNS • 100 billion neurons • Reasoning • Imagination • Memory • Language • Breathing and Heartbeat
The CNS http://www.pbs.org/wnet/brain/3d/index.html
Parts of the Brain • Cerebrum – largest part of the brain • Conscious functions • Reasoning, language, sight, touch, hearing • Two hemispheres • Similar but not identical • Connected by a thick bundle of axons deep within the brain • 4 Lobes • Frontal lobe – reasoning • Parietal lobe – touch • Temporal lobe – hearing • Occipital lobe - sight
Parts of the Brain • Cerebellum • Just below the cerebrum • Coordinates body movements • Many nerve pathways link the cerebellum with motor neurons throughout the body • Brain Stem • The lowest part of the brain • Connects the rest of the brain to the spinal cord • Controls unconscious functions
Spinal Cord • A thin, tubular bundle of nerves running from the brain stem and down through the center of the body to the pelvis • Protected by the vertebrae
Peripheral Nervous Systems - PNS • All the nervous tissue outside of the CNS • Connected to the CNS by nerves • Longest nerve in the body is the sciatic nerve • From lower back all the way to the toes
PNS • Sensory and Motor portions • Somatic nervous system • Controls mainly voluntary activities that are under conscious control • Attached to skeletal muscles • Also controls unconscious activities like reflexes
Autonomic Nervous System - ANS • All other involuntary activities • Connected to glands and internal organs • Heart Rate • Breathing • Digestion • Sweat Production • http://www.garyfisk.com/anim/autonomicns.swf
ANS • Sympathetic division • Deals with emergency situations • “Fight or flight” • Parasympathetic division • Controls involuntary activities that are not emergencies • Organs of the digestive system
The Senses • Part of the PNS sensory division • Eyes • Ears • Mouth • Nose • Skin • All have special cells called sensory receptors • http://www.brightstorm.com/science/biology/the-human-body/sensory-system/
Sight • http://www.wisc-online.com/objects/ViewObject.aspx?ID=AP14304
Hearing • Translating sound ways into an understandable sound
Balance • Our ears are responsible for our sense of balance • Any movement sends impulses to the brain and then the bran sends out impulses triggering contractions of skeletal muscles as needed to restore balance
Taste and Smell • Both are involve the ability to sense chemicals • http://www.bbc.co.uk/science/humanbody/body/factfiles/taste/taste_ani_f5.swf
Touch • The ability to sense pressure • Pressure receptors are found mainly in the skin • Concentrated on the tongue, lips, face, palms of the hands, and soles of the feet • http://www.youtube.com/watch?v=xRkPNwqm0mM
The Flavor of Food: Smell + Taste + Touch • http://science.kqed.org/quest/video/science-of-taste/
Drugs and the Nervous System • Psychoactive – affects the CNS • Influence the transmission of nerve impulses • http://www.thirteen.org/closetohome/animation/neuron-main.html • Examples • Caffeine – a stimulant that makes you feel more awake and alert • Alcohol – a depressant
Drug Abuse and Addiction • Drug abuse – using a drug without the advice of a medical professional or more reasons not originally intended • Drug addiction – continued used where you are unable to stop • Usually leads to needing more of the drug to get the same effect • Can lead to overdose and death
Disorders of the Nervous System • Vascular disorders – causing death of brain cells • Infections of the nervous tissue • Meningitis • Brain or spinal cord injuries • Abnormal brain functioning • Headaches, epilepsy • Breakdown of nervous tissues • Alzheimer’s, ALS, Consussions
Autism • http://science.kqed.org/quest/video/autism-searching-for-causes/
Alzheimer’s Disease • http://science.kqed.org/quest/video/alzheimers-is-the-cure-in-the-genes/