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Chapter Four Anatomy of the Nervous System

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Title: Chapter Four Anatomy of the Nervous System


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Chapter FourAnatomy of the Nervous System
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Divisions of the Vertebrate Nervous System
  • Central Nervous System-the brain and the spinal
    cord
  • Peripheral Nervous System-the nerves outside the
    brain and spinal cord
  • Two Division of the PNS
  • Somatic Nervous System-the nerves that convey
    messages from the sense organs to the CNS and
    from the CNS to the muscles and glands
  • Autonomic Nervous System-a set of neurons that
    control the heart, the intestines, and other
    organs

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Figure 4.1  The human nervous systemBoth the
central nervous system and the peripheral nervous
system havemajor subdivisions. The closeup of
the brain shows the right hemisphereas seen from
the midline.
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The Nervous System
  • The Spinal Cord-part of the CNS found within the
    spinal column
  • The spinal cord communicates with the sense
    organs and muscles below the level of the head
  • Bell-Magendie Law-the entering dorsal roots carry
    sensory information and the exiting ventral roots
    carry motor information to the muscles and glands
  • Dorsal Root Ganglia-clusters of neurons outside
    the spinal cord

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Figure 4.3  Diagram of a cross section through
the spinal cordThe dorsal root on each side
conveys sensory information to the spinal cord
the ventral root conveys motor commands to the
muscles.
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Autonomic Nervous System
  • Sympathetic-prepares the
  • body for arousal
  • Ex increased breathing, increased heart rate,
    decreased digestive activity
  • Form chain of ganglia just outside spinal cord
  • Short preganglionic axons release norepinephrine
  • Long postganglionic axons release norepinephrine
  • Parasympathetic-facilitates vegetative,
    nonemergency responses by the bodys organs
  • Ex increase digestive activity, activities
    opposing sympathetic system
  • Consists of cranial nerves and nerves from sacral
    spinal cord
  • Long preganglionic axons extend from the spinal
    cord to parasympathetic ganglia close to each
    internal organ release norepinephrine
  • Shorter postganglionic fibers then extend from
    the parasympathetic ganglia in the organs
    release acetylcholine

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The Brain
  • The Hindbrain/rhombencephalon
  • Posterior part of brain
  • Medulla-controls vital reflexes like breathing,
    heart beat, etc
  • Pons-Area where many axons cross from one side of
    the brain to the other
  • Reticular formation-control motor areas of the
    spinal cord and sends output to cerebral cortex
    increasing arousal and attention
  • Raphe system-sends axons to much of the
    forebrain, increasing or decreasing the brains
    readiness to respond to stimuli
  • Cerebellum-control movement, shifts of attention,
    balance and coordination

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The Brain
  • The Midbrain-middle of the brain
  • Tegmentum-roof or covering
  • Nuclei for third and fourth cranial nerves
  • Parts of Reticular formation
  • Extensions of the pathways between the forebrain
    and the spinal cord or hindbrain
  • Tectum-roof
  • Superior Colliculus Inferior Colliculus-importan
    t in routes of sensory information

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Figure 4.8  The human brain stemThis composite
structure extends from the top of the spinal cord
into the center of the forebrain. The pons,
pineal gland, and colliculi are ordinarily
surrounded by the cerebral cortex.
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The Brain
  • The Forebrain-most anterior and most prominent
    part of the mammalian brain
  • Thalamus
  • Part of the Diencephalon
  • Center of forebrain
  • Relay Station for Sensory Information
  • Hypothalamus
  • Part of Diencephalon
  • Regulates homeostasis, sexual behavior, fighting,
    feeding
  • Pituitary Gland
  • Endocrine gland attached to the base of the
    hypothalamus

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Figure 4.10  The limbic system is a set of
subcortical structures that form a border (or
limbus) around the brain stem
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Figure 4.12  A sagittal section through the human
brain
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The Brain
  • Forebrain Contd
  • Basal Ganglia
  • Responsible for motor behavior, some memory and
    emotional expression
  • Basal Forebrain
  • Located on the dorsal surface of the forebrain
  • Received input from the hypothalamus and basal
    ganglia
  • Send axons to cerebral cortex
  • Important in arousal, wakefulness, and attention
  • Hippocampus
  • Located between thalamus and cerebral cortex
  • Critical for the formation of new memory

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Figure 4.14  The basal gangliaThe thalamus is in
the center, the basal ganglia are lateral to it,
and the cerebral cortex is on the outside.
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The Brain
  • The Ventricles-Assists in cushioning the brain
  • Central Canal-fluid-filled channel in the center
    of the spinal cord
  • Ventricles-four fluid-filled cavities within the
    brain
  • CSF-clear fluid similar to blood plasma
  • Formed in choroid plexus
  • Flows from lateral to third to fourth ventricle
    to central canal or between meninges
  • Meninges-membranes that surround the brain and
    spinal cord

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Figure 4.16  The cerebral ventriclesDiagram
showing positions of the four ventricles.
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The Cerebral Cortex
  • Organization of the Cerebral Cortex
  • Contains six distinct layers of cells
  • Organized into columns-cells with similar
    properties arranged perpendicular to the laminae
  • Cells within a given column have similar or
    related properties

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The Lobes
  • The Occipital Lobe-posterior end of cortex
  • Contains primary visual cortex
  • The Parietal Lobe-between occipital love the
    central sulcus
  • Contains the primary somatosensory
    cortex-receiving touch sensation, muscle-stretch
    information and joint position information
  • The Temporal Lobe-lateral portion of each
    hemisphere, near the temples
  • Contains targets for audition, essential for
    understanding spoken language, complex visual
    processes, emotional and motivational behaviors
  • The Frontal Lobe-extends from the central sulcus
    to the anterior limit of the brain
  • Contains Primary Motor Cortex-fine movements
  • Contributes to shifting attention, planning of
    action, delayed response tasks as examples

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Figure 4.20  Some major subdivisions of the human
cerebral cortexThe four lobes occipital,
parietal, temporal, and frontal.
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Brain Function
How Do the Pieces Work Together? Does the Brain
Operate as a Whole or a Collection of Parts? Each
brain area has a function but it cant do much by
itself The Binding Problem The question of how
the visual, auditory, and other areas of your
brain influence on another to produce a combined
perception of the single object Synchronized
neural activity?
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