Nervous System

• Nervous System

  The control center of the body
• Neurology


  A physician who diagnose and treat disorders of the nervous system
• Nervous System


  • One of the smallest yet most complex body system
• Functions of Nervous System

  1. Receiving sensory output

  2. Integrating information

  3. Controlling muscles and glands

  4. Maintaining homeostasis

  5. Establishing and maintaning mental activity
• Sensory receptors

  Monitor numerous external and internal stimuli
• Brain and spinal cord


  Major organs for processing sensory input and initiating responses
• Skeletal muscles


  Contract only when stimulated by the nervous system
• Nervous system

  Controls the major movements of the body
• Nervous system


  Participates in controlling cardiac muscle, smooth muscle, and many glands
• Nervous system


  Plays an important role in maintaining homeostasis
• Brain


  Center of mental activity, including consciousness, memory, and thinking
• Three basic functions of nervous system

  • Sensory
  • Integrative
  • Motor
• Central Nervous System (CNS)


  Consists of the brain and spinal cord
• Brain


  Part of the CNS that is located in the skull and contains about 85 billion neurons
• Spinal cord

  Connected to the brain through the FORAMEN MAGNUM of the occipital bone and is encircled by the bones of the vertebral column
• Peripheral Nervous System (PNS)


  Consists of the nervous tissue outside the CNS
• Nerve


  A bundle of hundred to thousands of axons plus associated connective tissue and blood vessels
• Cranial nerves


  Nerves that emerge directly from the brain, 12 pairs
• Neuron (nerve cell)


  Receive stimuli, conduct action potentials, transmit signals to other neurons or effector organs
• Parts of a neuron

  • Cell body (soma)
  • Dendrites
  • Axon
  • Myelin sheath
  • Nodes of Ranvier
  • Glial cells
• Types of neurons

  • Sensory neurons (afferent neurons)
  • Motor neurons (efferent neurons)
• Types of glial cells

  • Astrocytes
  • Ependymal cells
  • Microglial cells
  • Oligodendrocytes
  • Schwann cells
• Myelinated axons


  Increases the speed and efficiency of action potential generations along the axon
• Resting membrane potential

  Maintained by the unequal distribution of ions across the cell membrane
• Generation of action potential

  1. Voltage-gated ion channels open

  2. Depolarization occurs

  3. Action potential is generated

  4. Repolarization occurs
• Synapse


  Junction where the axon of one neuron interacts with another neuron or with cells of an effector organ
• Reflex arc

  1. Sensory receptor

  2. Sensory neuron

  3. Interneurons

  4. Motor neuron

  5. Effector organ
• Converging pathway

  Two or more neurons synapse with the same neuron
• Diverging pathway


  The axon from one neuron divides and synapses with more than one other neuron
• Spinal cord


  Extends from the foramen magnum at the base of the skull to the second lumbar vertebra
• Spinal nerves


  Communicate between the spinal cord and the body
• Knee-jerk reflex


  A classic example of the stretch reflex
• Withdrawal reflex


  Removes a limb or another body part from a painful stimulus
• Spinal nerves

  31 pairs, including cervical, thoracic, lumbar, sacral, and coccygeal nerves
• Dermatomes


  Area of skin supplied with sensory innervation by a pair of spinal nerves
• Cervical plexus


  Supplies the skin and muscles of the head, neck, superior portion of the shoulders and chest, and diaphragm
• Phrenic nerves


  Innervate the diaphragm, injuries can cause breathing to stop
• Brachial plexus


  Supplies the upper limb and shoulder, injuries can cause Erb-Duchenne palsy
• Lumbosacral plexus


  Supplies the lower limb, injuries can cause inability to extend the leg and loss of sensation
• Cerebrum


  Largest part of the brain, divided into left and right hemispheres