8. Brain and Blood-Brain Barrier

Amazing Brain Growth Formula!

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Human brain development is sensational. With prenatal neuron growth of 250k per minute, the brain grows quickly. Founder cells spread out and neural cells follow the trail. They differentiate by location and then make lots and lots of interconnections.

 At birth, the brain has all of its parts functioning but total development is only about a third complete. It still has a long way to go. There are connection to make and neurons to myelinate. At maturity, this 3 pound, 100-billion neuron bundle is quite an accomplishment.

This lesson includes:

• developmental vulnerabilities
• blood-brain barrier
• neural Darwinism
• head injuries and what to do about them

Brain Lectures (raw)

 

And here is the second half:

 

Here are the resources you need:

• cluster
• slides
• terms
• notes
• quiz
• video

CLUSTER

SLIDES

TERMS

• active transport system
• ADHD
• adrenal medulla
• alcohol
• anti-convulsive
• antidepressant drugs
• antisaccade task
• apoptosis
• astrocytes
• asymmetrical division
• basal ganglia
• BDNF
• birth defects
• Blood-Brain Barrier
• brain injury
• capillary walls
• chemical gradients (Sperry, 1943)
• chemical guidance
• chemical pathfinding (Weiss, 1924)
• chicken pox-shingles
• close transfer
• closed head injury
• common blood supply
• concentrations
• concept of straight
• conception
• concussion
• confusion
• congenital varicella syndrome
• cortex differentiation
• critical periods
• dead
• dendritic branching
• differentiation
• dopamine for Parkinson’s
• ectoderm forms a plate
• endothelial cells
• enriched environments
• enrichment
• far transfer
• fetal alcohol syndrome
• fetal hydantoin syndrome
• forebrain
• founder cells
• head injury
• headaches
• hindbrain
• homeostasi
• hypertension
• hypothalamus
• implantation
• infectious disease
• Inferior collicui = hearing
• inflammation
• irritability
• ketones
• malnutrition
• microwaves & radiation
• midbrain
• migration
• musician’s cramp
• myelination
• near transfer
• neural Darwinism
• neural tube
• neurotrophins
• newborn period
• open head injury
• pathfinding
• pregnancy
• primitive streak
• proliferation
• radial glial cells
• semi-permeable
• skull fracture
• stem cells
• stiff neck
• superior colliculi = vision
• symmetrical division
• synapse elimination
• synapse formation
• synaptogenesis
• teratogens
• train the brain
• transfer
• undifferentiated
• unequal pupil size
• varicella (chickenpox)
• writer’s cramp

 

NOTES

• Prenatal
  • 18 days after conception
  • Primitive streak
    • Outer layer of embryo thickens
    • Ectoderm forms a plate
    • Edges curl up
    • Make a neural tube
      • Cells inside tube become neurons & glial cells
    • Closed tube
    • Tube with 3 bulges
  • Quick Preview
    • 1. Forebrain
      • Cerebral cortex
      • Basal ganglia
      • Limbic system
      • Thalamus
      • Hypothalamus
    • 2. Midbrain
      • Superior colliculi = vision
      • Inferior collicui = hearing
      • Homeostasis & reflexes
    • 3. Hindbrain
      • Medulla oblongata
      • Cerebellum
      • Pons
  • Phases
  • 1st Phase
    • Symmetrical Division
    • 2 identical founder cells
    • Radial Glial Cells
    • Spread out like tree
    • Neurons climb tree to their proper position
  • 2nd Phase
    • Asymmetrical Division
    • About 3 months
    • Divide into neuron & founder cells
  • End of cortical development
    • founder cells receive signal (cell death)
• Connections
  • When neurons reach home
  • Connect with each other
  • Grow dendrites & axons
  • Synapse formation
  • Synapse elimination
• 5 Steps of Neurons
  • 1. Proliferation
    • Production of new cells
    • Cells along the ventricles divide to become neurons and glia.
  • 2. Migration
    • Primitive neurons find their spots
    • Chemicals guide cells
  • 3. Differentiation
    • Neurons get axon & dendrites
    • Makes them different
    • Axon grow before dendrites
    • During migration
  • 4. Myelination
    • Glia cells produce myelin sheaths
    • first in spinal cord
    • Then in brain
    • Lasts til about 30
  • 5. Synaptogenesis
    • Continues throughout life
    • Forming synapses
• Age & Neurons
  • Neurons go from
    • undifferentiated
    • differentiated
    • dead
  • Stem cells
    • Nose cells always undifferentiated
    • Periodically divide & make new olfactory cells
• Pathfinding
  • Getting axons to their spots
  • Chemical Pathfinding (Weiss, 1924)
    • Grafted extra leg to a salamander
    • Axons grew, moved in sync with other legs
    • Nerves attach to muscles randomly
    • Variety of messages are sent
      • Each one tuned to a dif. muscle
  • Chemical Gradients (Sperry, 1943)
    • Severed optic nerve axons
    • Rotated them 180°
    • Grow back to their original target locations in midbrain
    • Axons attracted by some chemicals, repelled by others
    • TOPDV protein is 30x more concentrated in dorsal retina than ventral retina axons
    • Highest connect to highest
    • Lowest concentration axons connect to lowest
• Neural Darwinism
  • During development
    • Synapses form randomly
    • Selection process keeps some and rejects others
    • Chemical guidance
    • Neurotrophic factors
  • Muscles & synapse survival
    • produce & release NGF (nerve growth factor)
    • Not enough NGF, axons degenerate and cell bodies die
    • Neurons automatically die
      • don’t make synaptic connection
    • Apoptosis = cell death
  • Similar to NGF
    • Neurotrophin
      • promotes survival & activity
    • BDNF
      • brain-derived neurotrophic factor
      • most abundant neurotrophin in cortex
  • Make more than enough
    • Neurotrophins are also used in adult brains
    • More axon & dendrite branching
    • Deficiencies of neurotrophins lead to cortical shrinking and brain diseases
• Developing brain vulnerable
  • Toxic chemicals
    • Malnutrition
    • Infections
• Teratogens
  • Environmental factor
  • Interfere with development
  • Medication, drug, alcohol or substance
  • Disease
• Critical Periods
  • Implantation = common blood supply
    • Whatever’s in mother’s blood crosses
  • 10 to14 days after conception
  • 3.5 to 4.5 weeks
    • closure of the neural tube
  • Central nervous system vulnerable throughout pregnancy
• 3 Major Substances
  • Alcohol
  • Phenytoin
  • Chickenpox
• 1. Fetal alcohol syndrome
  • Best known non-genetic cause of mental retardation
    • (3 in 1,000)
  • Infant brains are especially sensitive to alcohol
  • Suppress release of glutamate
    • brain’s main excitatory
    • neurons receive less excitation and undergo apoptosis
  • Alcohol broken down more slowly
    • immature liver
  • Alcohol levels remain high longer
  • Worse when born to alcoholic mothers
    • drink more than four to five drinks/day
  • No amount of alcohol is safe
• 2. Phenytoin (or Dilantin)
  • Anti-convulsive
    • used to treat epilepsy (seizure disorder)
  • 10% chance of birth defects
  • Fetal Hydantoin Syndrome
  • If taken in the first trimester
• 3. Varicella (chickenpox)
  • Highly infectious disease
  • 95% of Americans have had it
  • 90% of pregnant women are immune
  • 1 out of 2,000 develop during pregnancy
  • A. If in pregnancy (week 1-20)
    • 2% chance of defects
    • “congenital varicella syndrome“
    • Scars
    • Malformed and paralyzed limbs
  • B. Newborn period
    • 5 days before to 2 after birth
    • About 25 % newborns become infected
    • About 30% of infected babies will die if not treated
• Parental use of:
  • Cocaine or cigarettes
  • ADHD
  • Antidepressant drugs
  • Heart problems
• Birth Defects
  • 3-5% of newborns
  • Leading cause of infant mortality
  • Majority have no known cause
• Cortex Differentiation
  • Different parts of cortex, different shapes
  • Shape and functions depend on input received
  • Transplant immature neurons
  • Become like neighbors
  • Transplant later
  • Some new, some old attributes
• Experience fine tunes
  • Redesign our brain to fit
    • (within limits)
  • Enriched environments
  • Thicker cortex
  • More dendritic branching
  • Best enrichment = activity
• Transfer
  • Far transfer = do well in one, do well in other tasks
  • Near transfer = practice task, do better on that task only
• Train the brain – doesn’t work
  • Blind from birth
  • Better at discriminating objects by touch
  • Increased activation in occipital lobe (vision) doing touch tasks
  • Use occipital cortex for Braille; sighted people don’t
  • Concept of straight
• Learning to read
  • Learn to read as adults
  • More gray matter in cortex
  • Thicker corpus callosum
• Music Training
  • Pro musicians
    • Bigger temporal lobe (30%)
    • 2x greater response to pure tones (in auditory cortex)
  • Violin players
    • larger area devoted to left fingers in the postcentral gyrus
  • Writer’s Cramp
    • Spend all day writing
    • Fingers get jerky, clumsy & tired
  • Musician’s Cramp
    • Practice too much
    • Fingers get jerky, clumsy & tired
    • Expanded representation of each finger overlaps neighbor
• Overruling reflexes
  • Antisaccade task
    • Object appears in periphery
    • Must look in opposite direction
  • Top-down processing overruling reflex
  • Improves with age unless
    • Very young
      • hard to look away from attention getter
    • ADHD
• Age & Neurons
  • At 30
    • Frontal cortex begins to thin
    • Much individual variation
  • 60+
    • Synapses alter more slowly (learn)
    • Hippocampus gradually shrinks
    • Compensate by using more brain areas
• Blood-Brain Barrier
  • (Paul Ehrlich, 1800’s)
  • Injected blue dye into animals
  • All tissues turned blue EXCEPT brain and spinal cord
  • Keeps most chemicals out of brain
  • Why need BBB?
    • Brain has no immune system
    • Neurons can’t replicate-replaced
    • No way to fix damage
    • Viruses that do enter kill you
      • Rabbies
    • Neural disorders last whole life
      • Chicken pox-shingles
  • How it works
    • Keeps out harmful chemicals
    • Keeps out medications
    • Cancer med
    • Dopamine for Parkinson’s
    • Astrocytes form layer around brain blood vessels
    • may be responsible for transporting ions from brain to blood
  • Semi-permeable
    • Endothelial cells line capillaries
    • Small spaces between each
    • Some things can move between them
    • Loosely joined in body, large gaps
    • Tightly joined in brain, blocking most molecules
    • Large molecules can’t easily pass thru
    • Molecules with a high electrical charge are slowed down
    • Protects the brain
  • What can cross passively
    • Small uncharged molecules
    • Oxygen & carbon dioxide
    • Molecules dissolve in fats
      • capillary walls are fats
  • What can cross actively
    • An active transport system
      • protein-mediated process
      • uses energy to pump chemicals
      • E.g., burn glucose for energy
    • Broken by:
      • Hypertension (high blood pressure)
      • Development (not fully formed at birth)
      • High concentrations of some substances
      • Microwaves & radiation
      • Inflammation
      • Brain injury
      • Infections
      • Alzheimer’s disease
        • endothelial cells shrink
        • makes gaps
        • harmful chemicals enter
  • Nourishing Neurons
    • Almost all need glucose
    • Practically only nutrient that crosses blood-brain barrier in adults
    • Ketones can also cross but are in short supply.
  • If you can’t use glucose
    • Korsakoff’s syndrome
    • thiamine (vitamin B1) deficiency
      • inability to use glucose
    • neuron death
    • severe memory impairment
• Head Injury
  • Open or Closed
    • Open head injury (penetrating)
      • Object enters brain
    • Closed head injury (skull not broke)
      • Concussion
      • Most common traumatic injury
      • Brain gets rattled
  • Causes
    • Car, train, airplane accident
    • Fall
    • Assault
    • Sports
  • Symptoms
    • Can show immediately or develop slowly
    • Unequal pupil size
    • Headaches
    • Obvious
    • Object sticking out of head
    • Fluid draining from nose-ears
    • Clear or bloody
    • Coma or unconscious
    • Paralysis
    • Seizures
  • Sort Of Obvious
    • Slurred speech
    • Blurred vision
    • Lack of coordination
    • Memory loss
    • Stiff neck
    • Vomiting more than once; children often vomit once
  • Not So Obvious
    • Irritability (especially children)
    • Mood or personality changes
    • Drowsiness
    • Confusion
    • Loss of hearing, vision, taste or smell
    • Low breathing rate
    • Memory loss
    • Symptoms improve, then get worse
  • Get immediate help if
    • Loss consciousness, even briefly
    • Severe headache or stiff neck
    • Vomits more than once
    • Behaves abnormally
    • Unusually drowsy
  • Do
    • Call 911
    • Make sure breathing
    • Assume spinal cord injury
    • If normal breathing but unconscious
    • Stabilize head and neck
    • Hands on both sides of head
  • If bleeding
    • Press clean cloth on wound
    • If soaks through, don’t remove it
    • Put another cloth over it
  • DO NOT
    • Don’t wash deep head wound
    • Don’t move or shake
    • Don’t remove helmet
    • Don’t pick up child
    • Don’t drink alcohol (48 hours)
    • If skull fracture
      • Don’t apply pressure to bleeding site
      • Don’t remove debris from wound
    • No aspirin
      • Aspirin & ibuprofen can increase risk of bleeding
    • If vomiting
      • Roll the head, neck & body as one unit
    • Sleeping
      • Wake every 2 to 3 hours, check alertness
      • ask simple questions: “What is your name?”

 

QUIZ

• 1. The Blood-Brain Barrier can be damaged by:
  • a.           mircowaves
  • b.           inflamation
  • c.           infection
  • d.           all of the above
• 2. Doing well in one task will transfer to your doing well in other tasks, according to:
  • a.           near transfer theory
  • b.           thin transfer theory
  • c.           tall transfer theory
  • d.           far transfer theory
• 3. 90% of pregnant women are immune to which infectious disease:
  • a.           insensitivity
  • b.           chickenpox
  • c.           diabetes
  • d.           arthritis
• 4. Synapses alter more slowly after what age:
  • a.           15
  • b.           30
  • c.           40
  • d.           60
• 5. The most common traumatic head injury is:
  • a.           to the temporal lobe
  • b.           to the parietal lobe
  • c.           closed
  • d.           open

For the answers: Click Here

VIDEO

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DISCUSSION ITEM

• Which brain development problems are you familiar with?