Bone

• CNS protection


  • Bone
  • Meninges
• Dura mater


  Tough, thick, strong, durable
• Arachnoid mater


  Spider web like extension secure it to the pia mater, contains blood vessels that form capillaries in pia mater
• Pia mater


  Gentle, delicate layer attached to surface of brain or spinal cord
• Subarachnoid space


  Filled with CSF
• Meningitis


  Inflammation of meninges, may be caused by a bacterial or viral infection, dangerous as it can spread to CNS
• Lumbar puncture


  Performed between L4 and L5 to obtain a sample of spinal fluid
• CSF


  • Water solution, similar to blood plasma but contains less protein and different ion concentrations, constantly being replenished with volume remaining constant
• Functions of CSF


  Supports and cushions brain and spinal cord, maintains chemically stable extracellular environment, regulates ion concentrations, provides nutrient delivery, removes waste, carries signals
• CSF production and flow


  Produced by choroid plexuses, flows through ventricles of brain and central canal of spinal cord, enters subarachnoid space via apertures in fourth ventricle, absorbed into blood of dural venous sinuses via arachnoid granulations
• If CSF circulation or drainage is obstructed

  CSF accumulates, exerting pressure on the brain
• In infants, CSF pressure can cause the brain and skull to swell outward
• Meningitis can cause hydrocephalus


  In this case we have more than just the problems associated with pressure
• Brain blood supply


  • Brain has very good blood supply, needs constant supply of O2 and glucose
• Blood-Brain Barrier (BBB)


  Brain is dependent on constant environment, brain capillaries are the least permeable in the body with endothelial cells joined by tight junctions
• Substances that can pass the BBB

  • Alcohol, CO2, oxygen, glucose, nicotine
• Exceptions to the BBB include the vomiting center in the brain stem and the hypothalamus
• Brain functions

  • Receives sensory input, correlates sensations, makes decisions, sends motor output, source of intelligence, emotions, behavior, memory
• Principal parts of the brain

  • Brain stem, cerebellum, diencephalon, cerebrum
• Brain stem

  Continuous with spinal cord, houses nuclei of 10 of 12 cranial nerves, houses reflex centers
• Brainstem regions

  • Medulla, pons, midbrain
• Diencephalon

  Center of the brain, just superior to the brain stem, includes the epithalamus, thalamus, and hypothalamus
• Epithalamus

  Includes the pineal body and melatonin
• Thalamus

  Relays information between the cerebral cortex and the periphery, spinal cord or brain stem, acts as a gateway to the cerebral cortex
• Hypothalamus

  Controls the autonomic nervous system, endocrine functions, links emotion to physical response, regulates body temperature, food intake, water balance, and sleep-wake schedule
• Cerebellum

  • Second largest portion of the brain, divided into left and right hemispheres, outer gray matter and inner white matter
• Cerebellum functions

  Coordinates skeletal muscle for smooth, highly skilled movements, coordinates skeletal muscles to maintain posture and balance
• Cerebrum

  Largest, most superior, most developed and most functionally complex region of the brain, has ridges and grooves to increase surface area
• Left brain controls the right side, right brain controls the left side
• Cerebral lobes

  • Frontal, parietal, occipital, temporal, insula
• White matter

  Composed of myelinated nerve fibers that carry information within the hemisphere, includes association fibers, commissural fibers, and projection fibers
• Gray matter

  Known as the cerebral cortex, contains neuron cell bodies and dendrites
• Functional regions of the cerebral cortex

  • Sensory areas, motor areas, complex integrative functions
• Primary somatosensory cortex

  Receives information from somatic sensory receptors, identifies body region
• Somatosensory association cortex

  Processes information from the primary somatosensory cortex to produce an understanding of an object
• Primary visual cortex

  Receives action potentials from the eye and produces a contralateral map of visual space
• Visual association area

  Communicates with the primary visual cortex
• Primary auditory cortex

  Receives action potentials from the ears and interprets pitch
• Wernicke's area

  Responsible for understanding language
• Primary olfactory cortex

  Processes conscious awareness of odors