Integration and Coordination Systems

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Integration and Coordination Systems

• Nervous System

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Introduction

• Nervous tissue consists of masses of nerve cells.
  These are called neurons.
• Nerve impulses electrochemical changes that
  transmit neurons.
• Nerves bundles of nerve fibers
• Neuroglial cells a specialized cell of the
  nervous system that produces myelin, communicates
  between cells, and maintains the ionic
  environment.

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Nervous System

• The organs of the nervous system can be divided
  into two groups
• Central Nervous System (CNS) consists of the
  brain and the spinal cord.
• Peripheral Nervous System (PNS) Portions of the
  nervous system that are outside the CNS (cranial
  and spinal nerves).

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General Functions

• The sensory function of the nervous system
  derives from sensory receptors at the ends of the
  peripheral neurons.
• Sensory receptors monitor external environmental
  factors (ex light and sound intensities) and
  conditions of the bodys internal environment
  (ex temperature and oxygen concentration).

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Functions

• Coordination of homeostasis
• Senses environmental change
• Interprets the change
• Acts on interpretations by initiating action in
  the form of muscle contractions and/or glandular
  secretions
• Monitors internal and external environments
• Works closely with the endocrine system to
  coordinate organ system activities in response to
  changing environmental conditions

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Neurons are highly specialized cells.

• A neuron has three main parts.
• Cell body has nucleus and organelles.
• Dendrites are nerve fibers that receive impulses.
• Axon are nerve fibers that carry impulses.

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• Neurons have other structures to transmit signals.

• Schwann cell type of neuroglial cell that
  surrounds a fiber of peripheral neuron, forming
  the neurilemmal sheath and myelin.

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• Neurons have other structures to transmit signals.

• Synapse junction between the axon of one neuron
  and dendrite or cell body of another neuron

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Two types of nerve fibers

• Myelinated
• Lipid-rich substance called myelin
• White due to lipid content
• Impulses travel faster
• Schwann cells migrate along axon and envelope it.
• Myelin sheath formed when Schwann cell wraps
  itself around axon several times.
• The neurilemmal sheath of Schwann contains
  cytoplasm and nuclei.
• GAP between Schwann cells and in myelin sheath
  are called Nodes of Ranvier.

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Two types of nerve fibers

• Myelinated (cont.)
• Schwann cells are not found in CNS.
• Myelinated axons appear white.
• White matter in the brain and spinal cord are
  produced by oligodendrocytes.
• Unmyelinated
• Unmyelinated tissue is gray.
• Lack a myelin sheath.

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Types of Neurons and Neuroglial
Cells(Classification of Neurons)

• Bipolar Neurons - The cell body has only two
  nerve fibers, one arising from each end.
• One is dendrite
• One is axon
• Example eyes, ears, nose
• Unipolar Neurons Single nerve fiber

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Types of Neurons and Neuroglial
Cells(Classification of Neurons)

• Multipolar Neurons Many nerve fibers arising
  from their cell bodies
• Only one fiber of each neuron is an axon
• The rest are dendrites
• Example brain, spinal cord

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Types of Neurons and Neuroglial
Cells(Classification of Neurons)

• On the basis of functional differences, neurons
  are grouped as follows

Sensory Neuron (afferent) Long dendrites of sensory neurons (only) Carries message from receptors to CNS
Motor Neuron (efferent) Long atoms of motor neurosensory Carries nerve impulses out of the brain or spinal cord to effectors stimulate muscles to contract and glands to release secretions
Mixed Neuron (all same) Both Interconnected to other neurons (brain and spinal cord)
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Types of Neuroglial Cells

• Astrocytes commonly found between neurons and
  blood vessels
• Provide structural support
• Join parts by numerous cellular processes
• Help regulate the concentration of nutrients and
  ions within the tissue
• Form scar tissue that fills spaces following
  injury to the CNS

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Types of Neuroglial Cells

• Oligodendrocytes occur in rows along nerve
  fibers
• Form myelin within the brain and spinal cord
• Do not form neurilemmal sheaths
• Microglia scattered through the central nervous
  system
• Support neurons and phagocytize bacterial cells
  and cellular debris

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Types of Neuroglial Cells

• Epedyma Form an epithelial-like membrane that
  covers specialized brain parts and forms the
  inner linings that enclose spaces within the bran
  and spinal cord

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Neurons receive and transmit signals.

• Resting potential means no signal is being
  transmitted.
• more Na (sodium) outside of cell
• more K (potassium) inside of cell

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• An action potential is a moving electrical
  impulse.

• It is generated by a stimulus.
• Na enters, and cell becomes positively charged.
• K leaves, and area of positive charge moves.

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• A chemical signal passes between neurons.

• Impulse reaches terminal.

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• Impulse reaches terminal.

impulse
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• Impulse reaches terminal.

• Neurotransmitters released into synapse.

impulse
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• Impulse reaches terminal.
• Neurotransmitters released into synapse.

• Neurotransmitters stimulate next cell.

impulse
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Types of Nerves

• A nerve fiber is an extension of a neuron.
• A nerve is a cordlike bundle of nerve fibers held
  together by layers of connective tissue.
• Sensory nerves - conduct impulses into the brain
  or spinal cord
• Motor nerves carry impulses to muscles or
  glands
• Mixed nerves both sensory and motor fibers

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Nerve Pathways

• The routes nerve impulses follow as they travel
  through the nerve system are called nerve
  pathways.
• A reflex arc usually includes a sensory neuron, a
  reflex center composed of interneurons, and a
  motor neuron.

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Nerve Pathways

• Reflex behavior
• Reflexes are automatic, subconscious responses to
  changes.
• Help maintain homeostasis.
• Knee-jerk reflex employs only two neurons.
• Withdrawal reflexes are protective.

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Spinal Cord

• The spinal cord is a nerve column that extends
  from the brain into the vertebral canal.
• Structure
• Composed of 31 segments, each of which gives rise
  to a pair of spinal nerves.
• Has a cervical enlargement and a lumbar
  enlargement.
• Has a central core of gray matter within white
  matter.
• The white matter is composed of bundles of
  myelinated nerve fibers.

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Spinal Cord

• Functions
• Provides a two-way communication system between
  the brain and other body parts.
• Ascending tracts carry sensory impulses to the
  brain.
• Descending tracts carry motor impulses to muscles
  and glands.

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Brain

• The brain is subdivided into the cerebrum,
  cerebellum, and brain stem.

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Cerebrum

• Structure
• Consists of two cerebral hemispheres connected by
  the corpus callsoum.
• Cerebral cortex is a thin layer of gray matter
  near the surface.
• White matter consists of myelinated nerve fibers
  that connect neurons within the nervous system
  and communicate with other body parts.

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Cerebrum

• Functions
• Provides higher brain functions.
• Cerebral cortex consists of sensory, motor, and
  association areas.
• One cerebral hemisphere usually dominates for
  certain intellectual functions.

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Cerebrum
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Brain Stem

• The brain stem consists of the midbrain, pons,
  and medulla oblongata.
• The midbrain contains reflex centers associated
  with eye and head movements.
• The pons transmits impulses between the cerebrum
  and other parts of the nervous system and
  contains centers that help regulate the rate and
  depth of breathing.
• The medulla oblongata transmits all ascending and
  descending impulses and contains several vital
  and nonvital reflex centers.

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Cerebrum
Brain Stem
Medulla Oblongata
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Cerebellum

• Consists of two hemispheres.
• Functions primarily as a reflex center for
  integrating sensory information required in the
  coordination of skeletal muscle movements and
  maintenance of equilibrium.

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Cerebrum
Cerebellum
Brain Stem
Medulla Oblongata
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Peripheral Nervous System

• The peripheral nervous system consists of cranial
  and spinal nerves that branch from the brain and
  spinal cord to all body parts.
• It is subdivided into the somatic and autonomic
  systems.

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Somatic Nervous System

• The somatic nervous system consists of the
  cranial and spinal nerve fibers that connect the
  CNS to the skin and skeletal muscles it oversees
  conscious activities.
• Cranial nerves
• Twelve pairs of cranial nerves connect the brain
  to parts in the head, neck, and trunk.
• Most cranial nerves are mixed, but some are
  purely sensory and others are primarily motor.
• Names of the cranial nerves indicate their
  primary functions or the general distributions of
  their fibers.
• Some are somatic, and other are autonomic.

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Somatic Nervous System

• Spinal nerves
• Thirty-one pairs of spinal nerves originate from
  the spinal cord.
• These mixed nerves provide a two-way
  communication system between the spinal cord and
  parts of the upper and lower limbs, neck, and
  trunk.
• Grouped according to the levels from which they
  arise, and they are numbered in sequence.
• Divides into several branches just beyond its
  foramen.
• Most combine to form plexuses in which nerve
  fibers are sorted and recombined so that those
  fibers associated with a particular part reach it
  together.

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Autonomic Nervous System

• The autonomic nervous system functions without
  conscious effort. It regulates the visceral
  activities that maintain homeostasis.
• General characteristics
• Autonomic functions are reflexes controlled from
  nerve centers in the brain and spinal cord.
• Consists of two divisions
• Sympathetic responds to stressful and emergency
  conditions
• Parasympathetic most active under ordinary
  conditions