Nervous System

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Nervous System

• AP Biology
• Ch. 48
• Ms. Haut

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Function of Nervous System

• Sensory Input
• Conduction of signals from sensory receptors
• Integration
• Carried out by Central Nervous System (CNS)
• Brain and spinal cord
• Motor Output
• Carried out by Peripheral Nervous System (PNS)
• Conduction of signals to muscle or gland cells
• Carry out bodys responses to stimuli

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Animal Nerve Cells

• Nerves rope-like bundles of extensions of
  neurons, tightly wrapped in connective tissue
• Neurons functional unit of the nervous system

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Functional Organization of Neurons

• Sensory Neurons relay information (stimuli) from
  the external and internal environments to CNS
• Interneurons integrate sensory input and motor
  output (carry stimuli in the brain and spinal
  cord)
• Motor Neurons convey impulses from CNS to
  effector cells in muscles or glands
• Glial cells support, protect, and nourish neurons

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Structural Diversity of Neurons
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Overview of Vertebrate Nervous System
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Neuron Circuitry

• Simplest neural circuit involves synapses between
  2 neurons, a sensory neuron and a motor neuron
• Result is often an automatic response called a
  reflex

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The Knee-jerk Reflex
http//bio.rutgers.edu/gb102/lab_5/103ar.html
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Neural Signals

• Nerve impulse is an electrical signal that
  depends on the flow of ions across the plasma
  membrane of a neuron

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Membrane Resting Potential
Cell is said to be polarized
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Action Potential

• A nerve impulse is generated when the difference
  in electrical charge disappears
• Occurs when a stimulus contacts the tip of a
  dendrite and increases the permeability of the
  cell membrane to Na ions
• Cell is said to be depolarized

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Graded Potentials
All-or-none event
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Regulation of Action Potential
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Propagation of the Action Potential

• After the wave of depolarization has passed, the
  neuron reestablishes the difference in charges by
  pumping K out of the cytoplasm

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Saltatory Conduction
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Synapses

• Nerve impulses pass down the dendrite, through
  the cell body, and down the axon.
• At the end of the axon, the signal reaches a
  fluid-filled space (synapse) separating the end
  of the axon from the dendrite of the next neuron.
• Neuromuscular junction synapse located at the
  junction of a neuron and muscle fiber

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Chemical Synapse
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Organizations of Invertebrates
Without CNS
(PNS)
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Vertebrate Nervous System
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Autonomic Nervous System

• Works on an involuntary basis
• 2 subdivisions

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Roles of Parasympathetic and Sympathetic
Divisions of the Autonomic Nervous System
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Structure of Brain
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Brainstem

• Medulla oblongata
• Contains centers that control
  visceral (autonomic,
  
  homeostatic) functions
• Breathing, heart and blood vessel activity,
  swallowing,
  vomiting, and digestion
• Pons
• Have nuclei in the medulla that regulate
  breathing centers
• Midbrain
• Centers for receipt and integration of sensory
  information
• Coordinates large-scale body movements such as
  walking

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Cerebellum

• Primary function is
  coordination of movement
• Receives information about
  position from joints and length of muscles,
  as well as auditory and visual systems
• Plays role in learning and remembering motor
  responses (hand-eye coordination)

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Thalamus and Hypothalamus

• Thalamus
• Main input center for sensory information going
  to cerebrum
• Receives input from cerebrum to regulate emotion
  and arousal
• Hypothalamus
• Source of posterior pituitary hormones and
  releasing hormones that act on anterior pituitary
• Regulates body temp, thirst, hunger, other basic
  survival mechanisms
• Plays role in sexual response and mating
  behaviors, fight-or-flight response, and pleasure

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Structure and Function of Cerebrum
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Primary Somatosensory cortex
Primary Motor cortex
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Sleep and Arousal

• Controlled by several centers in the cerebrum and
  brainstem
• Reticular formation neurons that pass through
  the brainstem
• Reticular activating system--regulates sleep and
  arousal
• Increased input to cortex, increases alertness
• Medulla and pons
• Nuclei stimulated induces sleep
• Serotonin may activate sleep centers

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Lateralization, Language, and Speech

• Association areas of cerebral cortex are
  lateralized (specialized functions)
• Left hemisphere
• Speech, language, calculation, and rapid serial
  processing of details
• Right hemisphere
• Overall context, spatial perception, and creative
  abilities

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Emotions

• Limbic system-functional group of nuclei and
  interconnecting axon tracts in the CNS
• Includes parts of the thalamus and hypothalamus,
  and portions of the cerebral cortex
• Linked to areas of cerebral cortex involved with
  complex learning, reasoning, and personality
• Amygdala-prominent component of limbic system
• Major organizer of emotional information
• Plays role in memory association