3n4

• Nervous system


  Includes a huge number of neurons, and an even huger number of synapses
• Central nervous system (CNS)

  The brain and the spinal cord
• Peripheral nervous system (PNS)


  Connects the brain and spinal cord to the rest of the body
• Parts of the PNS


  • Somatic nervous system
  • Autonomic nervous system
• Somatic nervous system


  Consists of the axons conveying messages from the sense organs to the CNS and from the CNS to the muscles
• Autonomic nervous system


  Controls the heart, intestines, and other organs
• The nervous system is three-dimensional
• Dorsal


  Toward the back
• Ventral


  Toward the stomach
• The dorsal–ventral axis of the human brain is at a right angle to the dorsal–ventral axis of the spinal cord
• Planes through the brain


  • Horizontal
  • Sagittal
  • Coronal (or frontal)
• Somatic nervous system


  Controls voluntary muscles and conveys sensory information to the central nervous system
• Autonomic nervous system


  Controls involuntary muscles
• Parts of the autonomic nervous system


  • Sympathetic: Expends energy
  • Parasympathetic: Conserves energy
• Anatomical terms referring to directions

  • Dorsal
  • Ventral
  • Anterior
  • Posterior
  • Superior
  • Inferior
  • Lateral
  • Medial
  • Proximal
  • Distal
  • Ipsilateral
  • Contralateral
• Planes through the brain

  • Coronal plane (or frontal plane)
  • Sagittal plane
  • Horizontal plane (or transverse plane)
• Lamina


  A row or layer of cell bodies separated from other cell bodies by a layer of axons and dendrites
• Column


  A set of cells perpendicular to the surface of the cortex, with similar properties
• Tract


  A set of axons within the CNS, also known as a projection
• Nerve


  A set of axons in the periphery, either from the CNS to a muscle or gland or from a sensory organ to the CNS
• Nucleus


  A cluster of neuron cell bodies within the CNS
• Ganglion


  A cluster of neuron cell bodies, usually outside the CNS (as in the sympathetic nervous system)
• Gyrus (pl.: gyri)


  A protuberance on the surface of the brain
• Sulcus (pl.: sulci)


  A fold or groove that separates one gyrus from another
• Fissure


  A long, deep sulcus
• Spinal cord


  The part of the CNS within the spinal column
• The spinal cord communicates with all the sense organs and muscles except those of the head
• The spinal cord is a segmented structure, and each segment has on both the left and right sides a sensory nerve and a motor nerve
• The entering dorsal roots (axon bundles) carry sensory information, and the exiting ventral roots carry motor information
• Dorsal root ganglia


  Clusters of neurons outside the spinal cord where the cell bodies of the sensory neurons are located
• Cell bodies of the motor neurons are inside the spinal cord
• Gray matter


  1. shaped area in the center of the spinal cord that is densely packed with cell bodies and dendrites
• Many neurons from the gray matter of the spinal cord send axons to the brain or to other parts of the spinal cord through the white matter, containing myelinated axons
• Each segment of the spinal cord sends sensory information to the brain and receives motor commands from the brain
• Autonomic nervous system


  Consists of neurons that receive information from and send commands to the heart, intestines, and other organs
• Sympathetic nervous system


  A network of nerves that prepare the organs for a burst of vigorous activity
• The sympathetic ganglia are closely linked, so they often act as a single system "in sympathy" with one another
• Parasympathetic nervous system


  Facilitates vegetative, nonemergency responses
• The parasympathetic ganglia are not linked to one another, so they act more independently than the sympathetic ganglia
• The parasympathetic nervous system's axons release the neurotransmitter acetylcholine onto the organs, while most sympathetic nervous system axons release norepinephrine