The Nervous System

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  • CENTRAL – The brain and spinal chord Brain Controls the body and interprets sensory input Spinal cord Pathway connecting the brain and the peripheral nervous system PERIPHERAL - Transmits information to and from the central nervous system Autonomic nervous system Automatically regulates glands, internal organs and blood vessels, pupil dilation, digestion, and blood pressure Somatic nervous system Carries sensory information and controls movement of the skeletal muscles Parasympathetic division Maintains body functions under ordinary conditions; saves energy Sympathetic division Prepares the body to react and expend energy in times of stress
  • CENTRAL – The brain and spinal chord Brain Controls the body and interprets sensory input Spinal cord Pathway connecting the brain and the peripheral nervous system
  • PERIPHERAL - Transmits information to and from the central nervous system Autonomic nervous system Automatically regulates glands, internal organs and blood vessels, pupil dilation, digestion, and blood pressure Somatic nervous system Carries sensory information and controls movement of the skeletal muscles Parasympathetic division Maintains body functions under ordinary conditions; saves energy Sympathetic division Prepares the body to react and expend energy in times of stress
  • Neuroscience – a branch of the life sciences that deals with the structure and function of neurons, nerves, and nervous tissue, especially focusing on their relationship to behavior and learning
  • Neurons - the basic cell that makes up the nervous system and which receives and sends messages within that system. Parts of a Neuron Dendrites - branch-like structures that receive messages from other neurons. Soma - the cell body of the neuron, responsible for maintaining the life of the cell. Axon - long tube-like structure that carries the neural message to other cells. Glial cells - grey fatty cells that: provide support for the neurons to grow on and around, deliver nutrients to neurons, produce myelin to coat axons, Myelin - fatty substances produced by certain glial cells that coat the axons of neurons to insulate, protect, and speed up the neural impulse. clean up waste products and dead neurons.
  • “ … axons of neurons found in the body are also coated with a thin membrane called the neurilemma , or Schwann’s membrane. This membrane, which surrounds the axon and the myelin sheath, serves as a tunnel through which damaged nerve fibers can repair themselves.” That’s why a severed toe might actually regain some function and feeling if sewn back on in time. Unfortunately, axons of the neurons in the brain and spinal cord do not have this coating and are, therefore, more likely to be permanently damaged.”
  • Resting potential - the state of the neuron when not firing a neural impulse. Action potential - the release of the neural impulse consisting of a reversal of the electrical charge within the axon. Allows positive sodium ions to enter the cell. All-or-none - referring to the fact that a neuron either fires completely or does not fire at all. Return to resting potential.
  • Ions – charged particles. Inside neuron – negatively charged. Outside neuron – positively charged. The Neuron at Rest - During the resting potential, the neuron is negatively charged inside and positively charged outside. The Neural Impulse - The action potential occurs when positive sodium ions enter into the cell, causing a reversal of the electrical charge from negative to positive. The Neural Impulse Continues – as the action potential moves down the axon toward the axon terminals, the cell areas behind the action potential return to their resting state of a negative charge as the positive sodium ions are pumped to the outside of the cell, and the positive potassium ions rapidly leave.
  • Axon terminals - branches at the end of the axon. Synaptic knob – rounded areas on the end of axon terminals. Synaptic vesicles - sack-like structures found inside the synaptic knob containing chemicals. Neurotransmitters - chemical found in the synaptic vesicles which, when released, has an effect on the next cell. Synapse/synaptic gap - microscopic fluid-filled space between the rounded areas on the end of the axon terminals of one cell and the dendrites or surface of the next cell. Receptor sites - holes in the surface of the dendrites or certain cells of the muscles and glands, which are shaped to fit only certain neurotransmitters. The key and lock images on this slide can be used analogously to highlight the functional significance of neurotransmitters and receptor sites .
  • Neurons must be turned ON and OFF. Excitatory neurotransmitter - neurotransmitter that causes the receiving cell to fire. Inhibitory neurotransmitter - neurotransmitter that causes the receiving cell to stop firing. Chemical substances can affect neuronal communication. Agonists - mimic or enhance the effects of a neurotransmitter on the receptor sites of the next cell, increasing or decreasing the activity of that cell. Antagonists - block or reduce a cell’s response to the action of other chemicals or neurotransmitters.
  • What would happen if the neurons released too much acetylcholine? The bite of a black widow spider does just that. Its venom stimulates the release of excessive amounts of acetylcholine and causes convulsions and possible death. Black widow spider venom is an agonist for acetylcholine. Acetylcholine is also found in the hippocampus, an area of the brain that is responsible for forming new memories, and low levels of acetylcholine have been associated with Alzheimer’s disease, the most common type of dementia.
  • Reuptake - process by which neurotransmitters are taken back into the synaptic vesicles. Enzyme - a complex protein that is manufactured by cells. One type specifically breaks up acetylcholine because muscle activity needs to happen rapidly, so reuptake would be too slow. “ The neurotransmitters have to get out of the receptor sites before the next stimulation can occur. Most neurotransmitters will end up back in the synaptic vesicles in a process called reuptake . (Think of a little suction tube, sucking the chemicals back into the vesicles.) That way, the synapse is cleared for the next release of neurotransmitters. Some drugs, like cocaine , affect the nervous system by blocking the reuptake process.”
  • Central nervous system (CNS) - part of the nervous system consisting of the brain and spinal cord. Spinal cord - a long bundle of neurons that carries messages to and from the body to the brain that is responsible for very fast, lifesaving reflexes.
  • Sensory neuron - a neuron that carries information from the senses to the central nervous system. Also called afferent neuron. Motor neuron - a neuron that carries messages from the central nervous system to the muscles of the body. Also called efferent neuron. Interneuron - a neuron found in the center of the spinal cord that receives information from the sensory neurons and sends commands to the muscles through the motor neurons. Interneurons also make up the bulk of the neurons in the brain.
  • Peripheral nervous system (PNS) - all nerves and neurons that are not contained in the brain and spinal cord but that run through the body itself; divided into the: Somatic nervous system - division of the PNS consisting of nerves that carry information from the senses to the CNS and from the CNS to the voluntary muscles of the body. Autonomic nervous system - division of the PNS consisting of nerves that control all of the involuntary muscles, organs, and glands sensory pathway nerves coming from the sensory organs to the CNS consisting of sensory neurons.
  • Soma = body Somatic nervous system - division of the PNS consisting of nerves that carry information from the senses to the CNS and from the CNS to the voluntary muscles of the body. Autonomic nervous system (ANS) - division of the PNS consisting of nerves that control all of the involuntary muscles, organs, and glands sensory pathway nerves coming from the sensory organs to the CNS consisting of sensory neurons. Sympathetic division (fight-or-flight system) - part of the ANS that is responsible for reacting to stressful events and bodily arousal. Parasympathetic division - part of the ANS that restores the body to normal functioning after arousal and is responsible for the day-to-day functioning of the organs and glands.
  • Soma = body Somatic nervous system - division of the PNS consisting of nerves that carry information from the senses to the CNS and from the CNS to the voluntary muscles of the body. Autonomic nervous system (ANS) - division of the PNS consisting of nerves that control all of the involuntary muscles, organs, and glands sensory pathway nerves coming from the sensory organs to the CNS consisting of sensory neurons. Sympathetic division (fight-or-flight system) - part of the ANS that is responsible for reacting to stressful events and bodily arousal. Parasympathetic division - part of the ANS that restores the body to normal functioning after arousal and is responsible for the day-to-day functioning of the organs and glands.
  • ACTIVITY Objectives This is a two-part activity designed to very loosely measure: 1. reaction time, and 2. neural conductance speed. Students will be exposed to the concept of neural chains and fast-moving speed of a neural impulse. Given that this activity is a very unscientific way to assess one aspect of neural conductance, students should be encouraged to discuss the activity’s validity/reliability shortcomings. Extra materials needed Measuring Tape Stopwatch (A Flash scripted stopwatch has been embedded on this slide. If it does not appear and function properly, a cell-phone timer will work.) White board and dry-erase marker Part 1: Reaction Time Invite all students to get up from their chairs and have students form a large circle around the room. Count the number of students in the circle. The activity is most effective if the class size is between 30 and 200 students. Write the number of students on the board. Have each student place their right hand on the shoulder of the person to their right. Identify beginning of the chain and the end of the chain. Instruct the students that when you shout “Start,” the person at the beginning of the chain will squeeze the shoulder of the person to his/her right and that this activity should be repeated by everyone in the chain. As soon as a student feels the shoulder squeeze, he or she should pass that squeeze along to the next person in the circle, as fast as possible. Make sure to start the stopwatch, as soon as you shout, “Start.” When the last person in the circle feels his/her shoulder being squeezed, he/she should shout, “STOP.” At this point, the timing will stop. On the board, write the total time it took students to complete the neural circuit. Repeat the above activity once or twice more and encourage the students to complete the circuit faster and faster. Divide the best time by the total number of student in the circle to find the REACTION TIME. Part 2: Neural Speed To focus a little more on neural speed, inform the students that they will have to arrange themselves in such a way that the neural impulse travels the entire length of the body . Randomly select a few students from class and measure the distance from their toes to the tips of their fingers, with their arms stretched as high above their heads as possible. Calculate the average distance (from toe to tip) in inches, and write this information on the board. This will represent the average distance for the entire class. Now, have students take their right hand and grab the left ankle of the person to their right. If students kneel in some way, this usually works best. Instruct the students that when you shout “Start,” the person at the beginning of the chain will squeeze the ankle of the person to his/her right and that this activity should be repeated by everyone in the chain. As soon as a student feels the ankle squeeze, he or she should pass that squeeze along to the next person in the circle, as fast as possible. Make sure to start the stopwatch, as soon as you shout, “Start.” When the last person in the circle feels his/her ankle being squeezed, he/she should shout, “STOP.” At this point, the timing will stop. On the board, write the total time it took students to complete the neural circuit. TO CALCULATE NEURAL CONDUCTANCE SPEED – First , divide the total time by the number of students . Second , take the result from the last step and divide it by the average distance (from toe to finger tip). This will result in what we might loosely call the speed of a neural impulse.
  • So what’s the difference between strong stimulation and weak stimulation? A strong message will cause the neuron to fire more quickly (as if someone flicked the light switch on and off as quickly as possible), and it will also cause more neurons to fire (as if there were a lot of lights going on and off instead of just one). The latter point can be demonstrated quite easily. Just touch lightly on the palm of your hand. You feel a very light pressure sensation. Now push hard in the same spot. You will feel a much stronger pressure sensation, and you can see with your own eyes that more of the skin on the palm of your hand is pushed in by your touch—more skin involved means more neurons firing.
  • The Nervous System

    1. 1. The Biological Perspective The Biological Perspective Nervous System Controlling Sensing & Behavior Neurons & The Biological Perspective
    2. 2. Links to Learning Objectives <ul><li>NS, NEURONS & NERVES </li></ul><ul><li>LO 2.1 Nervous system, neurons, nerves </li></ul><ul><li>LO 2.2 Neural communication </li></ul><ul><li>CENTRAL & PERIPHERAL NS </li></ul><ul><li>LO 2.3 Brain and spinal cord </li></ul><ul><li>LO 2.4 Somatic and autonomic systems </li></ul>STRUCTURES OF THE BRAIN LO 2.5 Studying the brain LO 2.6 Bottom part of the brain LO 2.7 Control of emotion, learning, memory, & motivation LO 2.8 Control of senses and movement LO 2.9 Higher forms of thought LO 2.10 Left and right sides of the brain THE CHEMICAL CONNECTION LO 2.11 Hormones & the nervous system
    3. 3. Nervous System, Neurons & Nerves Nervous Svstem. Neurons & Nerves Nervous System, Neurons & Nerves
    4. 4. Carries information to and from all parts of the body ervous system
    5. 5. Branches of Nervous System PERIPHERAL Autonomic Somatic Para Sympathetic Brain Spinal Chord 2.1 What are the nervous system, neurons and nerves? CENTRAL
    6. 6. Central Nervous System Brain Spinal Chord CENTRAL
    7. 7. Peripheral Nervous System PERIPHERAL Autonomic Somatic Para Sympathetic
    8. 8. Neuroscience <ul><li>Neuroscience – study of neural structures, behavior and learning </li></ul>
    9. 9. Structure of the Neuron Dendrites Axon Soma Myelin
    10. 10. Repairing Nerve Fibers “ … axons of neurons found in the body are also coated with a thin membrane called the neurilemma , or Schwann’s membrane. This membrane, which surrounds the axon and the myelin sheath, serves as a tunnel through which damaged nerve fibers can repair themselves.” -Page 50 (Ciccarelli & White)
    11. 11. Generating the Message: Neural Impulse <ul><li>All or none – like the firing of a gun, the neuron either fires completely or it does not fire at all </li></ul>
    12. 12. Generating the Message: Neural Impulse
    13. 13. The Synapse 2.2 How do neurons use neurotransmitter to communicate? The neurotransmitter is like a key and the receptor sites are like locks.
    14. 14. Neuron Communication <ul><li>Excitatory neurotransmitter - causes receiving cell to fire </li></ul><ul><ul><li>agonists mimic/enhance neurotransmitter effect on receptor sites </li></ul></ul><ul><li>Inhibitory neurotransmitter - causes receiving cell to stop firing </li></ul><ul><ul><li>antagonists block/reduce cell’s response to other neurotransmitters </li></ul></ul>
    15. 16. Cleaning Up The Synapse
    16. 17. Central & Peripheral Nervous Systems Nervous Svstems Central & Perioheral Central & Peripheral Nervous Systems
    17. 18. Central Nervous System <ul><li>Central nervous system (CNS) – brain and spinal cord </li></ul><ul><ul><li>spinal cord - bundle of neurons carries messages between body and brain </li></ul></ul>2.3 How do the brain and spinal cord interact?
    18. 19. Reflex Arc: Three Types of Neurons Afferent (sensory) neurons Efferent (motor) neurons Interneurons
    19. 20. Peripheral Nervous System <ul><li>Peripheral nervous system (PNS) - all nerves and neurons not contained in the CNS </li></ul><ul><ul><li>allows brain to communicate with senses </li></ul></ul>2.4 How do the autonomic and somatic nervous systems interact and control?
    20. 21. Autonomic NS: Parasympathetic “ Rest and digest” Some psychologists believe that extraverts are seeking to increase naturally low autonomic arousal.
    21. 22. Autonomic NS: Sympathetic “ Fight or Flight” Some psychologists believe that introverts shy away from things in an attempt to lower naturally high autonomic arousal.
    22. 23. END OF FIRST SECTION OF SLIDES Jump to next section
    23. 24. Lecture Activities
    24. 25. Neural Squeeze Chain What is your reaction time like? How many inches per second does a neural impulse travel? Let’s find out. We will need a stopwatch, a calculator and a little touching…
    25. 26. <ul><li>If the neural impulse fires with same “strength” every time it fires, how can you tell the difference among different stimulus intensities? </li></ul>
    26. 27. <ul><li>In small groups, discuss how the sympathetic NS functions help out in a “fight or flight” situation. What are the implications when the sympathetic NS remains active for extended time periods? </li></ul>

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