CNS*

• functions of central nervous system (CNS):

  • interpretation of sensory information
  • planning & monitoring movement
  • maintaining homeostasis
  • higher mental functions (language &learning)
• creation of neural tube:

  1. notochord forms from mesoderm cells soon after gastrulation is complete
  2. signals from notochord cause inward folding of ectoderm at the neural plate
  3. ends of neural plate fuse and disconnect to form an autonomous neural tube
• brain and spinal cord begin as the neural tube
• label development

  A) neural tube

  B) forebrain

  C) midbrain

  D) hindbrain

  E) telencephalon

  F) diencephalon

  G) mesencephalon

  H) metencephalon

  I) myelencephalon

  J) cerebrum

  K) diencephalon

  L) brainstem: midbrain

  M) brainstem: pons

  N) cerebellum

  O) brainstem: medulla oblongata

  
• regions of brain:

  1. cerebrum / cerebral hemispheres
  2. diencephalon
  3. brain stem
  4. cerebellum
• brain is organized into white matter and gray matter

  • white matter: myelinated and non-myelinated axons; tracts
  • gray matter: non-myelinated neurons and cell bodies
• function of the regions of the brain:

  • cerebrum
  • higher mental function
  • interpretation of sensory stimuli
  • planning and invitation of movement
  • diencephalon
  • processes, integrates, & relays info
  • maintains homeostasis
  • regulates biological rhythms
  • brain stem
  • maintains homeostasis
  • controls some reflexes
  • monitors movements
  • integrates & relays info
  • cerebellum
  • monitors & coordinates movement
• cerebral hemispheres

  • superior part of the brain
  • ~ 83% of the total brain mass
  • divided into 5 lobes
  • frontal
  • parietal
  • temporal
  • occipital
  • insular
  • forms part of floor (located deep)
• gyri: elevated ridges of tissue

  sulci: shallow grooves

  fissures: deep grooves
• cerebral cortex: where consciousness resides

  • composed of gray matter
  • no fiber tracts
  • billions of neurons
  • ~ 40% of the total brain mass
  • hemispheres are contralateral: concerned with the opposite side of body
  • arranged into 6 layers
• lobe "general" functions

  • frontal
  • planning, thinking, behavior, conscience, personality
  • parietal
  • sensory integration, attention
  • temporal
  • hearing, language, memory, emotion
  • occipital
  • visual information processing
• Neocortex/cerebral cortex areas:

  1. primary motor cortex: plans & executes movement
  2. frontal lobe
  3. primary sensory cortices: receive and process sensory input
  4. parietal, insular, temporal, occipital lobes
  5. association areas:
  6. single-task association areas
  7. multiple-task association areas
• motor areas in cerebral cortex:

  • primary (somatic) motor cortex
  • premotor cortex
  • broca's area
  • frontal eye field
• ventricles in brain:

  1. hollow chambers
  2. filled with CS fluid
  3. continuous
  4. lined with ependymal cells (glial cell)
  5. lateral ventricles
  6. paired
  7. within cerebral hemispheres
  8. third ventricle
  9. in the diencephalon
  10. fourth ventricle
  11. in the hindbrain
• broca's area: production of speech

  Wernicke's area: comprehension of speech
• sensory areas in cerebral cortex:

  • primary somatosensory cortex: receives info from somatic sensory receptors in skin
  • somatosensory association cortex: integrates sensory inputs from PSC
  • visual areas
  • primary visual cortex: receives info from retina
  • visual association area: uses past visual experience for interpretation
  • auditory areas:
  • primary auditory cortex: interpret auditory input
  • auditory association area: permits perception & stores sound memory
  • vestibular cortex: balance
  • olfactory cortex: smell
  • gustatory cortex: taste
  • visceral sensory area: visceral/body sensations
• multimodal association areas in cerebral cortex: receive input from multiple senses; allows for integration and storage of previous experiences

  • 3 parts
  • anterior association area/prefrontal cortex: involved in learning and personality
  • posterior association area: involved in pattern recognition
  • limbic association area: regulates emotional magnitude
• ~90% of people are right-handed and left hemisphere dominant
• left himisphere

  • language
  • math
  • logic

  right hemisphere

  • visual-spatial skills
  • intuition
  • emotion
  • art/music
• cerebral white matter: responsible for communication between hemispheres

  • commissural fibers: connect right & left hemispheres
  • projection fibers: connect cerebral cortex to rest of brain and spinal cord
  • association fibers: connect grey matter of cortical gyri with one another
• basal nuclei: cluster of nuclei embedded in central white matter, either side of diencephalon

  • involved in movement (behavior, cognition, & perception)
  • receives input from the entire cerebral cortex
  • acts as a filter
  • limits inappropriate responses
  • limits unnecessary movements
• striatum: caudate nucleus and putamen
• brain stem includes

  1. midbrain: movement, sensation, startle reflex
  2. pons: breathing, sleep arousal
  3. medulla oblongata: regulates breathing and heart beat, near instant death if damaged
• brain stem

  • occupy ~2.5% of the total brain mass
  • associated with 10 of the 12 cranial nerves
  • produces "programmed" autonomic behaviors
• pons: located between midbrain and medulla oblongata

  • composed primarily of conduction tracts
  • cranial nerves
  • trigeminal
  • abducens
  • facial nerves
• medulla oblongata: inferior part of the brain stem

  • maintains homeostasis
  • cardiovascular center
  • respiratory center
  • cranial nerves
  • hypoglossal
  • glossopharyngeal
  • vagus
• cerebellum: coordinates movement; process inputs from cerebral cortex, brain stem, and sensory nuclei

  • ~11% of total brain mass
  • works with cerebrum, basal nuclei, brain stem & spinal cord
  • 2 hemispheres
  • connected by Vermis
  • grey matter: cerebellar cortex & deep nuclei
  • white matter: arbor vitae and cerebellar peduncles
• cerebellar peduncles: paired fiber tracts that connect the cerebellum to the brain stem (ipsilateral)

  1. superior cerebellar peduncles
  2. middle cerebellar peduncles
  3. inferior cerebellar peduncles
• cerebellum processing:

  • fine-tunes motor activities
  • cerebellum receives information from somatic proprioreceptors throughout the body and visual equilibrium pathways
  • coordinates muscle movement
  • cerebral motor cortex influences motor neurons of the spinal cord
• limbic system: example of functional groups of grey matter connected by white matter (unique to mammals); emotional center (relayed mostly through the hypothalamus)
• reticular formation: network of nuclei (100+) throughout brain stem

  • input from several sources
  • output to entire brain & spinal cord
  • sleep, pain transmission, mood, motor functions, breathing, blood pressure, alertness
  • functions:
  • maintains cerebral cortical alertness
  • filters out repetitive stimuli
  • regulates skeletal and visceral muscle activity
  • inhibited by sleep centers
  • depressed by alcohol and tranquilizers
• factors influencing memory:

  • emotional state
  • rehearsal
  • association
  • automatic memory
  • formed via first impression
• types of brain wave patterns:

  1. alpha (8-13 hz)
  2. regular, rhythmic; indicate calm wakefulness
  3. beta (14-30 hz)
  4. less regular; mentally alert and concentrating
  5. theta (4-7 hz)
  6. irregular, most common in children; appear when concentrating
  7. delta (<5 hz)
  8. high amplitude
  9. observed during sleep
  10. in awake adults (brain damage)
• sleep/wake cycles are regulated by circadian rhythm in the hypothalamus

  • hormonally controlled
• importance of sleep/wake cycles

  • unknown
  • hypotheses:
  • allow for memory and emotional analysis
  • eliminate unneeded synapses
• types of sleep/wake cycles:

  1. non-rapid eye movement (NREM)
  2. type 1: relaxation, alpha waves
  3. type 2: arousal is more difficult, irregular EEG
  4. type 3: sleep deepens, theta and delta waves appear
  5. type 4: arousal is difficult, dominated by delta waves
  6. rapid eye movement (REM): muscles inhibited (except for the eyes and diaphragm)
  7. dreams
• higher brain functions:

  1. language
  2. Broca's area
  3. Wernicke's area
  4. memory
  5. declarative: facts
  6. short-term and long-term
  7. procedural: skills
  8. motor
  9. emotional memory
  10. brain wave patterns
  11. alpha
  12. beta
  13. theta
  14. delta
  15. sleep/wake cycles
  16. non-rapid eye movement (NREM)
  17. rapid eye movement (REM)
  18. consciousness
• consciousness

  • undefined
  • involves simultaneous activity of large areas of the cerebral cortex
  • is superimposed on other types of neural activity
  • is holistic and interconnected
  • measured on a gradient

  1. alertness
  2. drowsiness/lethargy
  3. stupor
  4. coma
• brain is a soft, delicate organ

  • protection
  • skull bones
  • cranial meninges
  • cerebrospinal fluid
  • blood-brain barrier
• meninges: connective tissue membranes

  • functions:
  • cover and protect CNS
  • protect blood vessels & enclose venous system
  • contain cerebrospinal fluid
  • partitions the skull
  • spaces
  • epidural: absence of periosteal dura in spinal cord provides space for epidural anesthetics
  • dural: separation of dural layers to provide sinuses for drainage of brain
  • subdural: houses serous fluid & some drainage veins
  • subarachnoid: houses major blood vessels and CSF
  • mater
  • dura: strongest, outer-most layer
  • arachnoid: middle meninx, separated from dura mater by subarachnoid space
  • pia: blood vessels