Structure of Nervous System

• Neuroanatomy


  The anatomy of the nervous system and the study of the various parts of the nervous system and their respective function(s)

  
• Nervous system


  • A network of neurons whose main feature is to generate, modulate and transmit information between all the different parts of the human body
  • Responsible for regulation of vital body functions (heartbeat, breathing, digestion), sensation and body movements
  • Presides over everything that makes us human; our consciousness, cognition, behavior and memories

  
• Sensory function


  • Nervous system uses its millions of sensory receptors to monitor changes occurring both inside and outside of the body
  • Those changes are called STIMULI, and the gathered information is called Sensory Input
• Integrative function


  • The Nervous System processes and interprets the sensory input and makes decisions about what should be done at each moment--a process called Integration

  
• Motor function


  • The nervous System then sends information to muscles, glands, and organs (effectors) so they can respond correctly, such as muscular contraction or glandular secretions
• Neurons


  The main structural and functional units of the nervous system, consisting of a body (soma) and a number of processes (neurites)

  
• Structural types of neurons

  • Multipolar
  • Bipolar
  • Pseudounipolar
  • Unipolar

  
• Central Nervous System


  • The control center of the body, consisting of the brain and spinal cord
  • Interprets incoming sensory information and issues instructions based on past experience and current conditions

  
• Peripheral Nervous System


  • Consists of bundles of nerves between the spinal cord and the rest of the body
• Brain


  • One of the largest and most complex organs in the human body
  • Made up of more than 100 billion nerves that communicate in trillions of connections called synapses
• Cerebrum


  • The largest part of the brain, covered by the cerebral cortex
  • Regulates senses, memory, emotions, intellectual activities and body movements
  • The cerebral cortex is responsible for processing information that is divided into 2 hemispheres: right cerebral hemisphere controls the left side of the body, left cerebral hemisphere controls the right side of the body

  
• Frontal lobe


  • Involves voluntary movement, reasoning, impulse control, language and speech
  • Broca's Area is part of the left frontal lobe and is associated with speech production

  
• Phineas Gage is often referred to as the "man who began neuroscience". He experienced a traumatic brain injury when an iron rod was driven through his skull, destroying much of his frontal lobe. His personality and behavior were so changed as a result of the frontal lobe damage that many of his friends described him as an almost different person entirely. The impact that the accident had has helped us better understand what the frontal lobe does, especially in relation to personality.
• Parietal lobe


  • Mainly involved with processing the sense of touch, limb position, and spatial awareness
  • Damage to the parietal lobe typically involves loss of these abilities in the parts of the body opposite the lesion, due to the brain's contralateral function
• Temporal lobe


  • Primarily processes auditory stimuli
  • A region in the temporal lobe known as Wernicke's area comprehends the sounds we hear by translating different pitches and frequencies into meaning
  • The temporal lobe communicates with the hippocampus to produce long-term memory

  
• Occipital lobe


  • Located at the rear end of the cerebral cortex and is known to be the visual processing center of the brain
  • Brodmann Area 17, the primary visual cortex, determines the size, shape and location of objects in the field of vision
  • Damage to the occipital lobe can cause an inability to identify colors, loss of visual capacity, and even hallucinations

  
• Corpus callosum


  • A network of nerve fibers that connects the right and left hemispheres of the brain
  • Damage to this region causes split-brain, where the hemispheres act independently from each other
• Roger Sperry's split-brain experiments in the 1960s pioneered modern-day knowledge on the condition of split-brain, where cognition differs between hemispheres and the two hemispheres have separate streams of consciousness with their own memories, perceptions and impulses

  
• Thalamus


  • A sensory relay for the brain, where all our senses, with the exception of smell, are routed before being directed to other areas of the brain for processing
  • Involved with consciousness, alertness and sleep
• Limbic system


  • Controls basic emotions and psychological drives, made up of the hippocampus, the amygdala and the hypothalamus
• Amygdala


  • An almond-shaped set of neurons responsible for processing fear, as demonstrated by research by Heinrich Kluver and Paul Bucy in the 1930s
• Hypothalamus


  • Located at the base of the brain near the pituitary gland, involved with pleasure, food, body temperature and sex
  • Regulates the pituitary gland and other hormone-releasing glands in the body, referred to as the "master gland" of the endocrine system
• Midbrain


  • Contains the colliculi, tegmentum and cerebral peduncles
  • The colliculi process visual and auditory signals before they are relayed to the occipital and temporal lobes
  • The tegmentum is involved in movement coordination and alertness
  • The cerebral peduncles play an important part in the central nervous system

  
• Hindbrain


  • Contains the medulla oblongata, pons and cerebellum
  • The medulla oblongata is primarily involved in breathing, heart rate, digestion, swallowing, heart rhythms and sneezing
  • The pons is involved in arousal, sleep, motor control and muscle tone
  • The cerebellum receives messages from muscles, tendons, joints and structures in the ear to control balance, coordination, movement and facilitate motor learning

  
• Motor/efferent neurons


  Carry impulses from the CNS to effectors organs, muscles and glands
• Sensory/afferent neurons


  Consist of nerve fibers that convey impulses to the CNS from sensory receptors located in various parts of the body, including somatic (from the skin, skeletal muscles, and joints) and visceral (from the visceral organs) sensory fibers
• Somatic nervous system


  • Connects the skin and muscles, allows us to consciously or voluntarily control our skeletal muscles
• Autonomic nervous system


  • Regulates events that are automatic or involuntary, such as the activity of smooth muscles and glands
• Sympathetic nervous system


  • Controls the "Fight or Flight" phenomenon, preparing the body to defend or escape by quickening heart rate, increasing breathing, diverting blood flow to muscles, dilating pupils, etc.
• Parasympathetic nervous system


  • The "housekeeping" system, relaxing the body and returning it to a resting state after the sympathetic response