Download The Nervous System

SBI4U The Nervous System •  ________________ Nervous System (CNS): consists of the brain and spinal cord –  Acts as the coordina:ng centre for incoming and outgoing informa:on •  _________________ Nervous System (PNS): onsists of the nerves that carry informa:on between the organs of the body and the CNS. The PNS can be divided further: –  _______________: controls the skeletal muscle, bones, and skin –  ___________________: controls the internal organs of the body Anatomy of a Nerve Cell Two different types of cells are found in the nervous system •  ______________ cells (neuroglial cells): nonconduc:ng cells important for structural support and metabolism of the nerve cells •  Important for structural support and metabolism of nerve cells –  “Glia” means glue in Greek –  Schwann cells are types of glial cells –  The blood brain barrier is made up of glia •  ________________: nerve cells that conduct nerve impulses –  Func:onal units of the nervous system –  Sensory neurons (_______________ neurons) –  _________________ –  Motor neurons (_______________ neurons) Nerve Impulses •  Jump from one node to another •  Move faster along myelinated nerve fibers than nonmyelinated ones •  Smaller the diameter the faster the speed of the impulse The Neuron All neurons contain dendrites, cell bodies, and axons •  Dendrites: projec:ons of cytoplasm that carry impulses toward the cell –  Receive informa:on from sensory neurons –  Conduct nerve impulses toward the cell body •  Axon: extension of cytoplasm that carries nerve impulses away from the cell body –  Carries the nerve pulse impulse toward other neurons or to effectors •  Myelin sheath: insulated covering over the axon of a nerve cell –  White coat of a faUy protein •  Schwann cells: special type of glial cell that produces the myelin sheath •  Nodes of Ranvier: regularly occurring gaps between sec:ons of myelin sheath along the axon •  Neurilemma: delicate thin membrane that surrounds the axon of nerve fibers found within the PNS –  Made of Schwann cells –  Promotes the regenera:on of damaged axons –  Nerves in the CNS do not have neurilemma, but they can s:ll be myelinated Sensory Neurons Sensory neurons (afferent neurons) carry impulses from sensory receptors to the CNS. _____________: clusters of sensory neurons located outside of the spinal cord ______________ ___________: Each sensory neuron has a specific sensory field where that one neuron will receive ___________ from. These recep:ve fields have the ability to _______________. These recep:ve fields are larger in our back and forearms, and much smaller in our lips, and finger pads. Interneurons These neurons lie completely within the CNS. They process the incoming signals by the sensory neurons and signal the appropriate outgoing motor neurons. •  Link neurons within the body Motor Neurons Motor neurons (efferent neurons) receive informa:on from interneurons. These neurons carry impulses from the CNS to ____________. Muscles, organs, and glands are classified as effectors because they produce ______________. Neurons Travel in Bundles Neurons travel throughout our body in bundles referred to as nerves. Reflexes •  Reflexes are specific, predictable, _______________ responses to types of s:mula:on Neuronal Circuits •  When we feel pain, we don't stop to think about how much that pain hurts. For example if we touch a hot stove, we pull our hand away quickly without thinking about it. •  ______________ _________: neural circuit through the spinal cord that provides a framework for a reflex ac:on (no direct input from the brain) •  The reflex arc begins when a receptor picks up a painful s:mulus. Sensory informa:on is sent to the spinal cord, and interneurons relay this informa:on directly to the motor neuron. The motor neuron ac:vates the muscle, causing it to contract. This allows our bodies to react as quick as possible.