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?