Functions of the Nervous System

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Functions of the Nervous System

• The nervous system has three basic functions
• Sensory - The nervous system senses certain
  changes (stimuli) both within your body and
  outside of your body.
• Integrative - It analyzes the sensory
  information, stores some aspects, and makes
  decisions regarding appropriate behaviors.
• Motor - The nervous system may respond to
  stimuli by initiating muscular contractions or
  glandular secretions.
• These three functions enable the nervous system
  the accomplishment of mental activity, the
  control of homeostasis, the regulation of other
  systems, and the control of all muscles and
  glands.

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Divisions of the Nervous System

• The central nervous system (CNS) consists of the
  brain and the spinal cord.
• The peripheral nervous system (PNS) consists of
  nerves and ganglia outside the CNS.
• The afferent division of the PNS transmits action
  potentials to the CNS.
• The efferent division carries action potentials
  away from the CNS.
• The PNS is subdivided into the somatic motor
  nervous system and the autonomic nervous system.
• The somatic motor nervous system which
  innervates skeletal muscle is mostly under
  voluntary control.
• The autonomic nervous system (ANS) innervates
  cardiac muscle, smooth muscle, and glands, and it
  is mostly under involuntary control.
• The ANS has sympathetic and parasympathetic
  divisions.

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Histology of the Nervous System

• The cells of the nervous system include neurons
  and neuroglia.
• Neurons receive stimuli and transmit action
  potentials.
• Neurons consist of a cell body (soma or
  parikaryon), dendrites, and axons.
• Neurons can be multipolar, bipolar, or unipolar.
• On the basis of function, sensory (afferent)
  neurons conduct impulses from receptors to the
  CNS association neurons (interneurons) conduct
  impulses from one neuron to another within the
  CNS and motor (efferent) neurons conduct
  impulses to effectors.
• Neuroglia include astrocytes, oligodendrocytes,
  Schwann cells, microglia, and ependymal cells.
• Neuroglia are specialized tissue cells that
  support neurons, attach neurons to blood vessels,
  produce myelin sheaths around axons, and carry
  out phagocytosis.
• Two types of neuroglia produce myelin sheaths
  oligodendrocytes myelinate axons in the CNS and
  Schwann cells myelinate axons in the PNS.

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Nerve
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Nerve
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Nerve
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Astrocytes
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The Cerebellum

• The cerebellum occupies the inferior and
  posterior aspects of the cranial cavity. It
  consists of two lateral hemispheres and a medial,
  constricted vermis.
• The cerebellum is attached to the brain stem by
  three pairs of cerebellar peduncles. These
  peduncles contain both sensory and motor axons
  that carry information into and out of the
  cerebellum.
• The cerebellum functions in the coordination of
  skeletal muscles and the maintenance of normal
  muscle tone, posture, and balance.

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Cerebellum
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The Cerebrum

• The cerebrum is the largest part of the brain.
  Its cortex contains gyri (convolutions),
  fissures, and sulci.
• The cerebral lobes are named the frontal,
  parietal, temporal, and occipital.
• The white matter is deep to the cortex and
  consists of myelinated and unmyelinated axons
  extending to other regions as association,
  commissural, and projection fibers.
• The basal ganglia are paired masses of gray
  matter in the cerebral hemisphere. They help
  control muscular movements.
• The limbic system is found in the cerebral
  hemispheres and diencephalon. It functions in
  emotional aspects of behavior and memory.

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Cerebrum
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The Cerebrum

• The sensory areas of the cerebral cortex are
  concerned with the interpretation of sensory
  impulses.
• The motor areas are the regions that govern
  muscular movement.
• The association areas are concerned with more
  complex integrative functions such as recognition
  of information.
• Speech involves the sensory speech area, the
  motor speech area, and the interactions between
  them and other cortical areas.
• Memory consists of sensory (lasting less than 1
  sec), short-term (lasting a few minutes), and
  long-term (permanent) memory.
• Each hemisphere controls the opposite half of the
  body. Commissures connect the two hemispheres.
  The left hemisphere is thought to dominate
  analytical, while the left is dominant for
  spatial perception and musical ability.

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Neural Terms

• Ganglia - A cluster of neuron cell bodies outside
  of the CNS. Located in the PNS.
• Nucleus - A cluster of neuron cell bodies in the
  CNS.
• Nerve - A group of axons and dendrites located in
  the PNS.
• Fiber tract - A group of axons and dendrites
  located in the CNS.
• Decussation- The crossing of nerve tracts from
  one side to the other within the CNS.
• Contralateral - On the opposite side affecting
  or controlling the opposite side of the body.
• Ipsalateral - On the same side affecting or
  controlling the same side of the body.

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Development of the Nervous System

• The development of the nervous system begins with
  a thickening of ectoderm called the neural plate.
• The parts of the brain develop from primary and
  secondary vesicles.
• The primary vesicles include the prosencephalon
  (forebrain), mesoencephalon (midbrain), and the
  rhombencephalon (hindbrain).
• There are five secondary vesicles.
• The prosencephalon divides into an anterior
  telencephalon and a posterior diencephalon.
• The mesencephalon remains unchanged.
• The rhombencephalon divides into an anterior
  metencephalon and a posterior myelencephalon.

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Neural Crest Cell Derivatives

• Bones of the skull
• Pharyngeal arch cartilages
• Otic capsule
• Stroma of the thyroid, parathyroid, thymus and
  salivary glands.
• Adrenal medullary cells
• Enteric neurons
• Sympathetic neurons
• Sensory neurons
• Schwann cells
• Pigment cells