ch 38 nervous system

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ch 38 nervous system
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ch 38 nervous system
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  1. DENDRITES
    • Receive information from the environment
    • a large surface area
    • Dendrites of sensory neurons respond to
    • pressure, odor, light, body temperature, blood pH, or the position of a joint
    • respond neurotransmitters
  2. CELL BODY
    • Process the information and produce electrical signals
    • If incoming signals are positive enough, a large, rapid electrical signal called an action potential is produced
  3. AXON
    • Conduct electrical signals over distances to a junction where it meets another cell
    • Single axons may stretch from our spinal cord to our toes, a distance of about 3 feet
    • Axons are typically bundled together into nerves, much like wires are bundled within an electrical cable
  4. SYNAPTIC TERMINALS
    • Transmit information to other neurons, muscles, or glands
    • The synaptic terminal: at the end of an axon of the sending neuron
    • A dendrite or cell body of a receiving neuron, muscle, or gland cell
    • A small gap separating the two cells
  5. resting potential
    • resting potential :a constant electrical voltage difference, or potential, across its plasma membrane
    • The voltage inside the cell is always negative about –40 to –90 millivolts (mV)
    • If the membrane potential becomes less negative (more positive), it reaches a level called threshold and triggers an action potential

  6. The Structure and Function of the Synapse
    • Action potential is initiated
    • The action potential reaches the synaptic terminal of the presynaptic neuron.
    • The positive charge of the action potential causes the synaptic vesicles to release neurotransmitters.
    • Neurotransmitters bind to receptors on the postsynaptic neuron
    • Neurotransmitter binding causes ion channels to open, and ions flow in or out.
    • Neurotransmitters are taken back into the synaptic terminal, are degraded, or diffuse out of the synaptic cleft.
  7. inhibitory postsynaptic potential (IPSP
    • inhibitory postsynaptic potential (IPSP): postsynaptic neuron becomes more negative
  8. excitatory postsynaptic potential (EPSP
    • excitatory postsynaptic potential (EPSP): postsynaptic neuron becomes less negative
  9. process of recieving stimulus
    • Determine the type of stimulus
    • different stimuli result in action potentials in different axons
    • that connect to different areas of the brain
    • Example, olfactory
    • Determine and signal the intensity of a stimulus
    • frequency of action potentials in a single neuron
    • many neurons that can respond to the same input
    • Integrate information from many sources
    • Ex. the neurons that activate biceps muscles are different than those that activate muscles of the face
    • Initiate and direct appropriate responses
    • How hard a muscle contracts is determined by how many neurons connect to it and how fast those neurons fire action potentials
  10. Sensory neurons
    • respond to a stimulus
  11. Interneurons
    • receive signals from sensory neurons, hormones, or neurons that store memories; based on this input, often activate motor neurons
  12. Motor neurons
    • receive information from sensory neurons or interneurons and activate muscles or glands
  13. Effectors
    • usually muscles or glands, perform the response directed by the nervous system

  14. Most behaviors are controlled by pathways composed of four elements:
    • Sensory neurons: respond to a stimulus
    • Interneurons: receive signals from sensory neurons, hormones, or neurons that store memories; based on this input, often activate motor neurons
    • Motor neurons: receive information from sensory neurons or interneurons and activate muscles or glands
    • Effectors: usually muscles or glands, perform the response directed by the nervous system

  15. The nervous system of all mammals, including humans, can be divided into two parts:
    • The central nervous system (CNS), consisting of the brain and spinal cord
    • The peripheral nervous system (PNS), consisting of neurons that lie outside the CNS and the axons that connect these neurons with the CNS

  16. Motor portion of the peripheral nervous system:
    • The somatic nervous system: voluntary (skeletal)

    • The autonomic nervous system: involuntary
    • The sympathetic division
    • norepinephrine onto their target organs, preparing the body for stressful or energetic actions
    • The parasympathetic division
    • acetylcholine onto their target organs, rest and digest


  17. autonomic nervous system:
    • The sympathetic division
    • norepinephrine onto their target organs, preparing the body for stressful or energetic actions
    • The parasympathetic division
    • acetylcholine onto their target organs, rest and digest


  18. central nervous system
    • receives and processes sensory information, generates thoughts, and directs responses
    • Protected
    • The skull and vertebrae
    • The triple connective tissue layer of meninges lies between the bone and spinal cord
    • The cerebrospinal fluid that cushions the brain and spinal cord, and nourishes the cells of the CNS

  19. what makes up the spinal cord
    • dorsal root ganglia: contain the cell bodies of sensory neurons
    • gray matter : the cell bodies of motor neurons that control voluntary muscles, and the autonomic nervous system, plus interneurons
    • white matter: contains myelin-coated axons of neurons that extend up or down the spinal cord
  20. dorsal root ganglia
    contain the cell bodies of sensory neurons
  21. gray matter
    • : the cell bodies of motor neurons that control voluntary muscles, and the autonomic nervous system, plus interneurons
  22. white matter
    • contains myelin-coated axons of neurons that extend up or down the spinal cord
  23. pain withdrawal reflex
    • 1. a painful stimulus activates a pain sensory neuron
    • 2. The signal is transmitted by the pain sensosry neuron to the spinal cord.
    • 3. The signal is transmitted to an interneuron and then to a motor neuron
    • 4. The motor neuron stimulates the effector muscle.
    • 5. The effector muscles causes a withdrawal response.
  24. hindbrain
    • The hindbrain consists of the medulla, pons, and cerebellum
  25. medulla
    • Hindbrain
    • medulla like an enlarged extension of the spinal cord . controls several automatic functions, such as breathing, heart rate, blood pressure, and swallowing
  26. pons
    • Hindbrain
    • pons appears to influence transitions between sleep and wakefulness and the rate and pattern of breathing
  27. cerebellum
    • Hindbrain
    • coordinating movements of the body . guides smooth, accurate motions and body . position
    • involved in motor learning as a result of practice
  28. midbrain
    • The midbrain contains clusters of neurons that contribute to movement, arousal, and emotion
    • contains an auditory relay center
    • controls reflex movements of the eyes
    • produces the transmitter dopamine
    • reward circuit that is responsible for pleasurable sensations and addiction
    • reticular formation dozens of neurons in the medulla, pons, and midbrain, which neurons send axons to the forebrain
    • a role in sleep and wakefulness, emotion, muscle tone, and some movements and reflexes
    • read and concentrate in the presence of a variety of distracting stimuli

  29. reticular formation
    • Midbrain
    • reticular formation dozens of neurons in the medulla, pons, and midbrain, which neurons send axons to the forebrain
    • a role in sleep and wakefulness, emotion, muscle tone, and some movements and reflexes
    • read and concentrate in the presence of a variety of distracting stimuli
  30. forebrain
    • The forebrain :thalamus, hypothalamus, and cerebrum
  31. thalamus
    • thalamus: complex relay station that channels all sensory information, except olfaction, from all parts of the body to the cerebral cortex
  32. hypothalamus
    • directs the activities of the autonomic nervous system
    • maintains homeostasis by influencing body temperature, food intake, water balance, heart rate, blood pressure, the menstrual cycle, and circadian rhythms

  33. cerebrum
    • cerebrum consists of two cerebral hemispheres and
    • amygdala: produce sensations of pleasure, fear, or sexual arousal when stimulated
    • hippocampus: formation of long-term memory, is required for learning
    • basal ganglia: important in the overall control of movement ; essential to the decision to initiate a particular movement and to suppress other movements
    • In Parkinsons disease, the substantia nigra degenerates, and affected people have a hard time starting a movement
    • In Huntingtons disease, basal ganglia in the cerebrum degenerate, and affected people make involuntary, undirected, flailing movements
  34. amygdala
    • Cerebrum
    • amygdala: produce sensations of pleasure, fear, or sexual arousal when stimulated
  35. hippocampus
    • hippocampus: formation of long-term memory, is required for learning
  36. basal ganglia
    • basal ganglia: important in the overall control of movement ; essential to the decision to initiate a particular movement and to suppress other movements
  37. The cerebral cortex
    • The cerebral cortex thin outer layer of each cerebral hemisphere
  38. cerebral cortex
    • The cerebral cortex thin outer layer of each cerebral hemisphere
    • The cortex is folded into convolutions
    • Neurons in the cortex receive sensory information, process it, direct voluntary movements, create memories, and allow us to be creative and even envision the future
    • The corpus callosum a large band of axons; each hemisphere communicate with each other
    • cerebral cortex is divided into four anatomical regions: frontal, parietal, occipital, and temporal
  39. convolutions
    • The cortex is folded into convolutions
    • Neurons in the cortex receive sensory information, process it, direct voluntary movements, create memories, and allow us to be creative and even envision the future
  40. corpus callosum
    • The corpus callosum a large band of axons; each hemisphere communicate with each other
  41. cerebral cortex is divided into four anatomical regions
    • frontal, parietal, occipital, and temporal
  42. Roger Sperry
    • In the 1950s, Roger Sperry of the California Institute of Technology studied people whose hemispheres had been separated by cutting the corpus callosum to prevent the spread of epilepsy from one hemisphere to the other
  43. Learning has two phases
    • Working memory: Remembering a telephone number long enough to dial it
    • long term memory: if the number is called often enough, it becomes permanently remembered

  44. How do we learn?
    • Most working memory probably requires the repeated activity of a particular neural circuit in the brain, and as long as the circuit is active, the memory stays
    • In contrast, long-term memory seems to be structural and the result of persistent changes in the expression of certain genes
    • It may require the formation of new, long-lasting synaptic connections between specific neurons, or the long-term strengthening of existing, but weak, synapses
    • For many memories, converting working memory into long-term memory seems to involve the hippocampus, which is believed to process new memories and transfer them to the frontal and temporal lobes of the cerebral cortex for permanent storage

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