25 Things To Know. Brain. development

Transcription

1 25 Things To Know Brain development

2 Brain Development 18 days after conception Primitive streak Outer layer of embryo thickens Ectoderm forms a plate

3 Brain Development 18 days after conception Edges curl up

4 Brain Development 18 days after conception Edges curl up Make a neural tube

5 Brain Development Cells inside tube Become neurons & glial cells

6 Brain Development Closed tube Tube with 3 bulges Forebrain Midbrain Hindbrain

7 Brain Development Forebrain Midbrain Hindbrain Heart

8 Quick Preview 1. Forebrain Cerebral cortex Basal ganglia Limbic system Thalamus Hypothalamus

9 Quick Preview 2. Midbrain Superior colliculi = vision Inferior collicui = hearing Homeostasis & reflexes

10 Quick Preview 3. Hindbrain Medulla oblongata Cerebellum Pons

11 PHASES 1 st Phase Symmetrical Division 2 identical founder cells

12 PHASES Radial Glial Cells Spread out like tree

13 PHASES Radial Glial Cells Spread out like tree Neurons climb tree to their proper position

14 PHASES 2 nd Phase Asymmetrical Division About 3 months Divide into neuron & founder cells

15 PHASES End of cortical development founder cells receive signal (cell death)

16 Connections When neurons reach home Connect with each other Grow dendrites & axons Synapse formation Synapse elimination

17 5 Steps of Neurons 1. Proliferation Production of new cells Cells along the ventricles divide to become neurons and glia.

18 5 Steps of Neurons 2. Migration Primitive neurons find their spots Chemicals guide cells

19 5 Steps of Neurons 3. Differentiation Neurons get axon & dendrites Makes them different Axon grow before dendrites During migration

20 5 Steps of Neurons 4. Myelination Glia cells produce myelin sheaths first in spinal cord Then in brain Lasts til about 30

21 5 Steps of Neurons 5. Synaptogenesis Continues throughout life Forming synapses

22 Age & Neurons Neurons go from undifferentiated differentiated dead

23 Age & Neurons Stem cells Nose cells always undifferentiated Periodically divide & make new olfactory cells

24 Pathfinding Getting axons to their spots Chemical Pathfinding Weiss (1924) grafted extra leg to a salamander axons grew, moved in sync with other legs

25 Pathfinding Weiss (1924) Theory: nerves attach to muscles randomly variety of messages are sent each one tuned to a dif. muscle

26 Pathfinding Sperry (1943) Severed optic nerve axons Rotated them 180 Grow back to their original target locations in midbrain Chemical gradients

27 Pathfinding Chemical Gradients Axons attracted by some chemicals, repelled by others TOPDV protein is 30x more concentrated in dorsal retina than ventral retina axons

28 Pathfinding Chemical Gradients Highest connect to highest Lowest concentration axons connect to lowest

29 Neural Darwinism During development Synapses form randomly Selection process keeps some and rejects others Chemical guidance Neurotrophic factors

30 Neural Darwinism Muscles & synapse survival produce & release NGF (nerve growth factor) Not enough NGF, axons degenerate and cell bodies die

31 Neural Darwinism Neurons automatically die don t make synaptic connection Apoptosis = cell death

32 Neural Darwinism Similar to NGF Neurotrophin promotes survival & activity

33 Neural Darwinism Similar to NGF BDNF brain-derived neurotrophic factor most abundant neurotrophin in cortex

34 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

35 Vulnerabilities Developing brain vulnerable Toxic chemicals Malnutrition Infections

36 Teratogens Environmental factor Interfere with development Medication, drug, alcohol or substance Disease

37 Teratogens Critical Periods Implantation = common blood supply Whatever s in mother's blood crosses 10 to14 days after conception

38 Teratogens Critical Periods 3.5 to 4.5 weeks closure of the neural tube Central nervous system vulnerable throughout pregnancy

39 Teratogens 3 Major Substances Alcohol Phenytoin Chickenpox

40 Alcohol 1. Fetal alcohol syndrome Best known non-genetic cause of mental retardation (3 in 1,000)

41 Alcohol 1. Fetal alcohol syndrome Infant brains are especially sensitive to alcohol

42 Alcohol 1. Fetal alcohol syndrome Suppress release of glutamate brain s main excitatory neurons receive less excitation and undergo apoptosis

43 Alcohol 1. Fetal alcohol syndrome Alcohol broken down more slowly immature liver alcohol levels remain high longer

44 Alcohol 1. Fetal alcohol syndrome Worse when born to alcoholic mothers drink more than four to five drinks/day No amount of alcohol is safe

45 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

46 3. Varicella (chickenpox) highly infectious disease 95% of Americans have had it 90% of pregnant women immune 1 out of 2,000 develop during pregnancy

47 3. Varicella (chickenpox) A. If in pregnancy (week 1-20) 2% chance of defects "congenital vericella syndrome Scars Malformed and paralyzed limbs

48 3. Varicella (chickenpox) 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

49 Parental use of: Cocaine or cigarettes ADHS Antidepressant drugs heart problems

50 Birth Defects Birth defects 3-5% of newborns Leading cause of infant mortality Majority have no known cause

51 Cortex Differentiation Different parts of cortex different shapes Shape and functions depend on input received

52 Cortex Differentiation Different parts of cortex Transplant immature neurons Become like neighbors Transplant later Some new, some old attributes

53 Experience fine tunes Redesign our brain to fit (within limits)

54 Experience fine tunes Enriched environments Thicker cortex More dendritic branching Best enrichment = activity

55 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

56 Blind from birth Skills better at discriminating objects by touch increased activation in occipital lobe (vision) doing touch tasks

57 Blind from birth Skills Use occipital cortex for Braille sighted people don t Concept of straight

58 Learning to read Learn to read as adults More gray matter in cortex Thicker corpus callosum

59 Music Training Pro musicians Bigger temporal lobe (30%) 2x greater response to pure tones (in auditory cortex)

60 Music Training Violin players larger area devoted to left fingers in the postcentral gyrus

61 Writer s Cramp Spend all day writing Fingers get jerky, clumsy & tired

62 Musician s Cramp Practice too much Fingers get jerky, clumsy & tired expanded representation of each finger overlaps neighbor

63 Overruling reflexes Antisaccade task Object appears in periphery Must look in opposite direction

64 Overruling reflexes Antisaccade task Top-down processing overruling reflex

65 Overruling reflexes Antisaccade task Improves with age unless Very young hard to look away from attention getter ADHD

66 Age & Neurons At 30, frontal cortex begins to thin Much individual variation

67 Age & Neurons 60+ Synapses alter more slowly (learn) Hippocampus gradually shrinks Compensate by using more brain areas

68 Blood-Brain Barrier

69 Blood-Brain Barrier Paul Ehrlich (1800 s) Injected blue dye into animals All tissues EXCEPT brain and spinal cord

70 Blood-Brain Barrier Keeps most chemicals out of brain

71 Why need BBB? Brain has no immune system Neurons can t replicate-replaced No way to fix damage

72 Why need BBB? Brain has no immune system Viruses that do enter kill you Rabbies

73 Why need BBB? Brain has no immune system Neural disorders last whole life Chicken pox-shingles

74 How it works Keeps out harmful chemicals Keeps out medications Cancer med Dopamine for Parkinson s

75 How it works Astrocytes form layer around brain blood vessels may be responsible for transporting ions from brain to blood

76 How it works Semi-permeable Endothelial cells line capillaries Small spaces between each Some things can move between them

77 How it works Endothelial cells walls of capillaries Loosely joined in body, large gaps Tightly joined in brain blocking most molecules

78 How it works Large molecules can t easily pass thru Molecules with a high electrical charge are slowed down Protects the brain

79 How it works What can cross passively Small uncharged molecules Oxygen & carbon dioxide Molecules dissolve in fats capillary walls are fats

80 How it works What can cross actively An active transport system protein-mediated process uses energy to pump chems. E.g., glucose

81 Blood-Brain Barrier Broken by: Hypertension (high blood pressure) Development (not fully formed at birth) High concentrations of some substances Microwaves & radiation

82 Blood-Brain Barrier Broken by: Inflammation Brain injury Infections

83 How it works Alzheimer s disease endothelial cells shrink makes gaps harmful chemicals enter

84 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.

85 Nourishing Neurons If you can t use glucose Korsakoff's syndrome thiamine (vitamin B 1 ) deficiency inability to use glucose neuron death severe memory impairment

86 Head Injury

87 Head Injury Open or Closed Open head injury (penetrating) Object enters brain

88 Head Injury Open or Closed Closed head injury (skull not broke) Concussion Most common traumatic injury Brain gets rattled

89 Head Injury

90 Head Injury

91 Head Injury Causes Car, train, airplane accident Fall Assault Sports

92 Head Injury Symptoms Can show immediately or develop slowly Unequal pupil size Headaches

93 Head Injury Symptoms Obvious Object sticking out of head Fluid draining from nose-ears Clear or bloody Coma or unconscious

94 Head Injury Symptoms Obvious Paralysis Seizures

95 Head Injury Symptoms Sort Of Obvious Slurred speech Blurred vision Lack of coordination Memory loss

96 Head Injury Symptoms Sort Of Obvious Stiff neck Vomiting more than once Children often vomit once

97 Head Injury Symptoms Not So Obvious Irritability (especially children) Mood or personality changes Drowsiness Confusion

98 Head Injury Symptoms Not So Obvious Loss of hearing, vision, taste or smell Low breathing rate Memory loss

99 Head Injury Symptoms Not So Obvious Symptoms improve, then get worse

100 Head Injury Get immediate help if Loss consciousness, even briefly Severe headache or stiff neck Vomits more than once Behaves abnormally Unusually drowsy

101 Head Injury Do Call 911 Make sure breathing

102 Head Injury Do Assume spinal cord injury If normal breathing but unconscious Stabilize head and neck Hands on both sides of head

103 Head Injury Do If bleeding Press clean cloth on wound If soaks through, don t remove it Put another cloth over it

104 Head Injury 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)

105 Head Injury DO NOT If skull fracture Don t apply pressure to bleeding site Don t remove debris from wound

106 Head Injury No aspirin Aspirin & ibuprofen can increase risk of bleeding

107 Head Injury If vomiting Roll the head, neck & body as one unit

108 Head Injury Sleeping Wake every 2 to 3 hours, check alertness ask simple questions: "What is your name?"

109 Biological Psych.com