CNS

• Central Nervous System enables you to

  • Subconsciously regulate your internal environment by neural means
  • Experience emotions
  • Voluntarily control your movements
  • Be consciously aware of your own body and your surroundings
  • Engage in other higher cognitive processes such as thought and memory

  
• Components of the Central Nervous System

  • Brain
  • Spinal cord

  
• Neuroglial Cells


  Also called glial cells or supporting cells, they physically, metabolically, and functionally support interneurons

  
• CNS Glial Cells


  • Oligodendrocytes
  • Astrocytes
  • Microglia

  
• Oligodendrocytes


  • Present in white matter (predominant cells) and gray matter, myelinate parts of several axons

  
• Astrocytes


  • Largest and most abundant glial cells, have multiple processes and form perivascular feet that completely enclose all capillaries, classified as fibrous or protoplasmic

  
• Microglia


  • Smallest and rarest glial cells found in gray and white matter, migrate through the neuropil for protective and immune functions

  
• Ependymal Cells


  • Columnar or cuboidal cells (may have cilia or microvilli), no basal lamina, basal projections extend to the neuropil

  
• The Central Nervous System is enclosed by hard, bony structures, wrapped by three protective and nourishing membranes — meninges, and floats in cushioning fluid — CSF

  
• Blood-brain barrier (BBB)


  Limits access of blood-borne materials into nervous tissues, protects brain from chemical fluctuations in blood, minimizes possibility that harmful blood-borne substances might reach central nervous tissue, prevents certain circulating hormones that could also act as neurotransmitters from reaching brain, limits use of drugs for treatment of brain and spinal cord disorders

  
• The blood-brain barrier keeps K+ low and Na+ High, and the cells are joined by tight junctions

  
• Brain Components and their Major Functions

  • Basal Nuclei (Inhibit muscle tone, select and maintain purposeful motor activity, help monitor and coordinate slow, sustained contractions)
  • Hypothalamus (Regulate homeostatic functions, link nervous and endocrine systems, influence emotion and behavior, role in sleep-wake cycle)
  • Cerebellum (Maintain balance, enhance muscle tone, coordinate and plan skilled voluntary muscle activity)
  • Brain Stem (Origin of majority of peripheral cranial nerves, control cardiovascular, respiratory, and digestive functions, role in regulating muscle reflexes, integrates sensory input, governs sleep)

  
• Cerebellum


  • Maintains proper position of the body in space, subconscious coordination of motor activities, plays key role in learning skilled motor tasks, has three different parts (vestibulocerebellum, spinocerebellum, cerebrocerebellum)

  
• Basal Nuclei


  • Act by modifying ongoing activity in motor pathways, inhibit muscle tone, select and maintain purposeful motor activity while suppressing useless or unwanted patterns of movement, help monitor and coordinate slow, sustained contractions
• Diencephalon Components


  • Hypothalamus (Controls homeostatic functions, anterior pituitary hormone secretion, posterior pituitary hormones, ANS, emotion, behavior, sleep-wake cycle)
  • Thalamus (Performs primitive sensory processing, serves as relay station and synaptic integrating center for sensory input, involved in directing attention)

  
• Limbic System


  • Responsible for emotions, basic behavioral patterns related to survival and perpetuation of the species, plays important role in motivation, learning, and memory
• Amygdala


  • Located on interior underside of temporal lobe, site where link between unconditioned and conditioned stimulus is formed, activates flight-or-fight stress system, uses GABA to condition someone from a certain stimulus

  
• Neurotransmitters of the Limbic System


  Norepinephrine and Dopamine (elicit highest rates of self-stimulation), Norepinephrine and Serotonin (deficiency leads to depression, Prozac)
• Cerebral Cortex Lobes


  • Occipital Lobe (initial processing of visual input)
  • Temporal Lobe (initial reception of sound sensation)
  • Parietal Lobe (somatosensory processing)
  • Frontal Lobe (voluntary motor activity, speaking ability, thought elaboration)

  
• Primary Motor Cortex


  • Located in frontal lobe, confers voluntary control over movement produced by skeletal muscles, primarily controls muscles on the opposite side of the body, motor homunculus depicts location and relative amount of motor cortex devoted to output to muscles of each body part, activated by readiness potential
• Higher Motor Areas of the Cortex

  • Supplementary motor area (plays preparatory role in programming complex sequences of movement)
  • Premotor cortex (important in orienting the body and arms toward a specific target)
  • Posterior parietal cortex (guides the premotor cortex by processing sensory input about the body's momentary position in relation to the target)

  
• Somatosensory Motor Complex


  • Initial cortical processing and perception of somesthetic and proprioceptive input, sensory homunculus shows the distribution of sensory input to the somatosensory cortex from different parts of the body

  
• Primary Areas of Cortical Specialization for Language

  • Broca's area (governs speaking ability)
  • Wernicke's area (concerned with language comprehension, responsible for formulating coherent patterns of speech that are transferred to Broca's area)
• Language disorders include aphasias, speech impediments, and dyslexia
• Left Cerebral Hemisphere


  Excels in logical, analytic, sequential, and verbal tasks like math, language forms, and philosophy

  
• Right Cerebral Hemisphere


  Excels in nonlanguage skills like spatial perception and artistic and musical talents

  
• Stages of Sensory Processing in the Brain

  • Relayed from afferent neuronal receptors
  • Initial cortical processing of specific sensory input
  • Further elaboration and processing of specific sensory input

  
• Somatosensory Motor Complex


  Initial cortical processing and perception of somesthetic and proprioceptive input

  
• Sensory homunculus


  Shows the distribution of sensory input to the somatosensory cortex from different parts of the body

  
• Broca's area


  Governs speaking ability
• Wernicke's area


  Concerned with language comprehension, responsible for formulating coherent patterns of speech that are transferred to Broca's area
• Language disorders


  • Aphasias
  • Speech impediments
  • Dyslexia
• Left Cerebral Hemisphere


  • Excels in logical, analytic, sequential, and verbal tasks
  • Math, language forms, philosophy
• Right Cerebral Hemisphere


  • Excels in nonlanguage skills
  • Spatial perception and artistic and musical talents

  
• Cortical pathway for speaking a word seen or heard


  1. Visual information from primary visual cortex to angular gyrus

  2. Auditory information from primary auditory cortex to angular gyrus

  3. Information transferred to Wernicke's area to formulate language command

  4. Language command transmitted to Broca's area to translate into sound pattern

  5. Sound program conveyed to primary motor cortex to activate facial and tongue muscles

  
• Neuroglobin


  Binds to oxygen in neurons to provide oxygen for aerobic respiration
• Glycogen in astrocytes


  Stored for nourishment of neurons if glucose is depleted
• Substances may or may not pass through the blood-brain barrier

  
• Oxygen and glucose pass through the blood-brain barrier
• Drugs may or may not pass through the blood-brain barrier