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Nervous System

Nervous System. Function of the Nervous System. Allows communication throughout the body Transmits information about our body and surroundings to the brain. Information is sent from the the brain to muscles to stimulate contraction or relaxation Reflexes protect us from damage

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Nervous System

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  1. Nervous System

  2. Function of the Nervous System • Allows communication throughout the body • Transmits information about our body and surroundings to the brain. • Information is sent from the the brain to muscles to stimulate contraction or relaxation • Reflexes protect us from damage • Signals control hormone release

  3. Structure of the Nervous System • The nervous system is divided into the central and peripheral nervous system • Central nervous system (CNS) • brain and spinal cord • Peripheral nervous system (PNS) • all the other nerves • Two types of cells dominate the tissue •  neurons - send and receive messages • neuroglia- support the neurons

  4. Neurons 1) Sensory neurons • carry information to the CNS about the body's surroundings to the spinal cord and brain 2) Interneurons •  are in the brain and spinal cord and carry information within it 3) Motor neurons • carry signals out from the CNS to the PNS causing responses in muscles and glands

  5. Structure of the Nerve Cell • Dendrites - finger-like projections that receive messages • Cell body- part of the cell that the dendrites connect to. contains the nucleus • Axon - long, slender body that transmits information from one side of the cell to the next • Myelin - covers the nerve cell and allows the signal to be transported faster - makes nerves look white • Schwann Cells- partially surrounds nerves of the pns and produce the myelin sheath • Oligodendrocyte - produces the myelin sheath in the cns • Nodes of Ranvier - gaps in the myelin sheath

  6. How are messages transmitted from one nerve cell to another cell? • Synapse - the space between the nerves • Neurotransmitters - chemicals released from one nerve (presynaptic neuron) into the synapse that bond to the dendrites of the next nerve (postsynaptic neuron), muscle, or gland • "All or nothing" - If the signal sent to the postsynaptic neuron is not strong enough, the signal will not continue down the postsynaptic neuron.

  7. Reflex Arc • Reflexes help prevent more serious injury by allowing the body to quickly more away from danger (pain) • Steps in the Reflex Arc • a sensory receptor detects pain (something hot, sharp, etc.) • the signal is carried to the spinal cord - processing does NOT occur in the brain • a signal is sent back through a motor neuron to make the muscles move quickly away • Some reflexes involve only sensory and motor neurons • Reflexes also help maintain heart rate, blood pressure, digestion, swallowing, sneezing, and vomiting

  8. What happens if nerves are damaged?  *MATURE NERVE CELLS DO NOT DIVIDE* • If the cell body is injured, the nerve usually dies • To replace damaged nerves, the stem cell must be stimulated to divide • In the PNS if an axon is damaged, it may regrow - VERY slowly • If a axon in the CNS is damaged, regeneration is unlikely

  9. Reflex Arc Animation

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