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Download Neuron & the Nervous Systems & Reflex
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Nervous Systems The Nervous System: Sends messages quickly but they don’t last long. Broken into two parts: • Central Nervous System (CNS) – Brain and spinal cord • Peripheral Nervous System (PNS) – Carries messages to and from CNS The Nervous System: It breaks down into two parts. Central nervous system Peripheral nervous system Sympathetic and parasympathetic divisions of the nervous system Summary of autonomic differences Autonomic nervous system controls physiological arousal Sympathetic division (arousing) Pupils dilate Parasympathetic division (calming) EYES Pupils contract SALIVATION Increases Perspires SKIN Dries Increases RESPERATION Decreases Accelerates HEART Slows Inhibits DIGESTION Activates Secrete stress hormones ADRENAL GLANDS Decrease secretion of stress hormones Decreases 3 types Neurons Types of Neurons Sensory Motor Interneurons Sensory Neurons • INPUT From sensory organs to the brain and spinal cord Drawing shows a somatic neuron Sensory Neuron Brain Spinal Cord Motor Neurons • OUTPUT From the brain and spinal cord, to the muscles and glands Sensory Neuron Brain Spinal Cord Motor Neuron Interneurons • Interneurons carry information between other neurons only found in the brain and spinal cord Sensory Neuron Brain Spinal Cord Motor Neuron The Neuron & Action Potential The basic building block of our nervous system and how it sends messages. Cell Body & Nucleus The Cell Body Contains the cell’s nucleus – round, centrally located structure – contains DNA – controls protein manufacturing – directs metabolism – no role in neural signaling Dendrites Dendrites • Information collectors or receivers • Receive inputs or signals from neighboring neurons • Inputs may number in thousands • If enough inputs the cell’s AXON may generate an electrical output Dendritic Growth • Mature neurons generally can’t divide • But new dendrites can grow • Provides room for more connections to other neurons • New connections are basis for learning • Studies show people with higher education have more dendritic connections than someone that is a high school dropout. Neural Networks Axon Axon Axon • Where all the action is • Action Potential takes place – electrical charge is sent down the axon. • One axon per cell, 2 distinct parts – tube-like structure – branches at end (axon terminals) that branch out to dendrites of other cells Myelin Sheath & Nodes of Ranvier Myelin Sheath • • • • White fatty casing on axon Acts as an electrical insulator Not present on all cells When present, increases the speed of neural signals down the axon allowing the action potential to “jump” to each Node of Ranvier - like a paved highway (see video below to compare mylenated axons vs. non-mylenated axons • If this degenerates (dirt road), you have multiple sclerosis and can’t control your muscles. If time view this in a video click on the web address below (it will use QuickTime): Mylenated Axon Axon Terminal or Buttons Axon Terminals Axon Terminal or Buttons • This is where the electrical impulse triggers synaptic transmission to the dendrites of a receiving neuron. Glial Cells •They are the janitors of the neuron. •Support cells that provide neurons with structural support and nutrition. •They also remove cell wastes and enhance the speed of the neuron The Reflex Works by bypassing the brain so you can react quicker. Sensory Neuron Interneuron Motor Neuron A Neural Chain A Neural Chain A Neural Chain A Neural Chain A Neural Chain A Neural Chain
