9 Science Term 1 Week 1 - The Nervous System

• Neurons


  a nerve cell; the basic building block of the nervous system
• Nerve impulse


  the electrical message carried by a nerve cell
• Cell body


  part of the neuron that contains the nucleus
• Dendrites


  branches from cell body that receive messages from other neurons
• Axon


  A threadlike extension of a neuron that carries nerve impulses away from the cell body.
• motor neurons


  neurons that carry outgoing information from the brain and spinal cord to the muscles and glands
• Effectors


  -produces a response e.g.muscle contracts to move hand away from stimulus or gland squeezes and releases hormone into blood.
• Connector neurons


  transmit messages between neurons in the CNS
• Sensory neurons


  carry impulses from the sense organs to the spinal cord and brain
• Neurotransmitters


  Chemicals that transmit information from one neuron to another
• Synapse


  Gap between neurons
• Myelin sheath


  covers the axon of some neurons and helps speed neural impulses
• Cerebrum


  Largest part of the brain; responsible for voluntary muscular activity, vision, speech, taste, hearing, thought, and memory.
• Cerebellum


  Balance and coordination
• The 3 brain stem functions

  1. control heartbeat

  2. breathing

  3. blood pressure
• Medulla


  the base of the brainstem; controls heartbeat and breathing
• Cranium


  skull
• Vertebrae


  backbones
• cerebrospinal fluid


  the fluid in and around the brain and spinal cord
• The nervous system controls all organs, physiological and psychological reactions, and even the endocrine system.
• The nervous system is the most distinctive feature of our species.
• The nervous system consists of three principal functions: sensory input, integration, and motor output.
• Sensory receptors on the skin detect the eight legs of a spider, which is sensory input.
• The nervous system processes the sensory input, decides what should be done about it, and that process is called integration.
• The motor output is the response that occurs when the nervous system activates certain parts of the body.
• The nervous system consists of several levels of organization, starting with the central and peripheral nervous systems.
• The central nervous system consists of the brain and spinal cord, which is the main control center.
• The peripheral nervous system consists of all the nerves that branch off from the brain and spine that allow the central nervous system to communicate with the rest of the body.
• The sensory, or afferent division of the peripheral nervous system picks up sensory stimuli and slings that information to the brain.
• The motor, or efferent division of the peripheral nervous system sends directions from the brain to the muscles and glands.
• The somatic, or voluntary nervous system rules skeletal muscle movement.
• The autonomic, or involuntary nervous system keeps the heart beating, lungs breathing, and stomach churning.
• The autonomic nervous system also has its own complementary forces: the sympathetic division mobilizes the body into action and gets it all fired up, while the parasympathetic division relaxes the body and talks it down.
• Most sensory neurons are unipolar, while motor, or efferent, neurons are mostly multipolar and transmit impulses away from the central nervous system and out to the body’s muscles and glands.
• Interneurons, or association neurons, live in the central nervous system and transmit impulses between sensory and motor neurons.
• Some interneurons might send a signal straight down a bunch of multipolar neurons to your quadriceps muscle on your thigh, triggering you to kick your leg out before you even know what’s going on.
• Nerve cells use chemistry and electricity to communicate with each other, which is one of the most stupifyingly awesome and complicated aspects of your nervous system, and basically of all life.
• Sensory, or afferent, neurons pick up messages and transmit impulses from sensory receptors in the skin or internal organs, and send them toward the central nervous system.
• Bipolar neurons have two processes -- an axon and a single dendrite -- extending from opposite sides of the cell body, and are found mostly in the retina of the eye and other sensory receptors.
• Nerve cells are not all identical, and their differences in structure are one of the ways that they are classified and identified.