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CMHC201 > Lecture 13: Biology of childhood onset disorders > Flashcards

Lecture 13: Biology of childhood onset disorders Flashcards

1
Q

What are symptoms and signs?

A
  • indicative of potential disease or condition

- a manifestation of underlying pathology

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2
Q

what is pathology?

A
  • the disrupted/changed biological processes of the disease or condition
  • what is the underlying mechanism causing changes in biological processes?
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3
Q

what is aetiology?

A
  • what causes the disease or condition
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4
Q

what are some things to consider when dealing with conditions and diseases?

A
  • treatment for symptoms
  • can the impacted biological processes be corrected?
  • if we don’t understand the biology, we tend to be treating and managing the symptoms
  • early intervention? can we predict who may be affected?
  • need to understand pathology to cure, need to also understand the causes of the pathology to prevent
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5
Q

What are some prenatal risk factors which predispose diseases or disorders?

A
  • genetic/chromosomal
  • maternal factors:
  • obesity
  • high gestational weight gain
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6
Q

What are some perinatal risk factors which predispose diseases or disorders?

A
  • low birth weight
  • born prematurely
  • complications at birth:
    oxygen deprivation
    birth injuries
  • infections
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7
Q

What are some childhood risk factors which predispose diseases or disorders?

A
  • injuries
  • infections
  • malnutrition
  • environmental
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8
Q

what are some conditions that become apparent during infancy/childhood

A
  • asthma
  • cystic fibrosis
  • diabetes type 1
  • developmental disabilities e.g. ASD, ADHD
  • mental illnesses
  • cancer
  • disruptive behaviour disorder
  • motor skill disorders
  • obesity
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9
Q

what is type 1 diabetes?

A

inability to control blood glucose levels due to lack of insulin

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10
Q

who is affected by type 1 diabetes and when does it get diagnosed?

A
  • usually diagnosed in childhood, peaks at 4-7 and 10-14 years of age
  • affects about 1:500 school aged children in NZ
  • about 10% of all diabetes cases in NZ are type 1 (approx. 26,000)
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11
Q

what are some symptoms of type 1 diabetes?

A
  • increased thirst
  • frequent urination
  • extreme hunger
  • weight loss
  • fatigue
  • mood changes
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12
Q

what is the biology of diabetes type 1?

A

in a normal situation, insulin is released from the pancreas which stimulates glucose uptake by muscle and fat tissues

  • however in type 1 diabetes, insulin is not produced which results in cells unable to take p glucose.
  • Then, fat is mobilized for energy which the liver breaks down into ketones.
  • High levels of ketones can be dangerous and lead to coma or death.
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13
Q

what is the Aetiology of type 1 diabetes?

A

the immune system attacks beta cells in the pancreas

- type 1 diabetes is a tissue specific autoimmune disease

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14
Q

how does the autoimmune disease happen for type 1 diabetes?

A
  • beta cells release insulin and exosomes at the same time. exosomes are extracellular vesicles, a lipid membrane containing proteins
  • dendritic cells, a type of immune cell, process and present antigens to T cells because they think the exosomes are foreign
  • the T cells are immune cells which respond to a foreign target
  • antigens are a molecular structure which are capable to stimulating an immune response
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15
Q

how is genetics involved in type 1 diabetes?

A

10% of cases have a family history of type 1 diabetes

  • there are multiple genes involved including histocompatibility complex (MHC) genes (also called HLA). These have an important role in determining how the cells of the immune system recognise antigens.
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16
Q

what are some environmental factors in type 1 diabetes?

A
  • environmental factors are likely to be important as monozygotic twins (identical)), only have a 50% risk of type 1 diabetes if the other twin is affected so genetics aren’t too involved
  • exposure to viruses can trigger an autoimmune response
  • diet
  • stress
  • gut bacteria
    are also important environmental factors
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17
Q

what are the treatments for diabetes type 1?

A

insulin treatment!

  • the aim is to maintain healthy blood glucose levels

can be done by:

  • monitoring blood glucose
  • take exogenous insulin (injections or pumps)
  • healthy well balanced diet
  • regular exercise (this can cause uptake of glucose without needing insulin)
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18
Q

what are the 3 types of ADHD behaviours?

A

Inattentive

  • easily distracted
  • short attention span

Hyperactive

  • restless
  • can’t sit still

Impulsive

  • acts without thinking
  • interrupts

there are 3 sub-groups, but can present with overlapping characteristics

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19
Q

what is ADHD?

A

a neurological conditions

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20
Q

who does ADHD affect most?

A
  • ~1 in 20 New Zealanders
  • 2-5% of all children
  • more commonly diagnosed in males (may be because of presentation differences, diagnosis bias towards male, or sex differences in biology is yet to be fully determined)
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21
Q

how were people with ADHD described in the 1900s?

A

Dr Sir George described the condition as ‘an abnormal defect of moral control children’. Described some children that ‘could not control their behaviour in the same way a typical child would, but noted they were intelligent’.

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22
Q

how is ADHD described in modern times?

A

ADHD people are usually energetic, enthusiastic, creative, intuitive, sensitive and highly intelligent

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23
Q

what is the hypothesis of the biological cause of ADHD?

A

a delay in developmental/maturation of the brain

24
Q

what areas of the brain are impacted? what are these areas for?

A
  • prefrontal cortex - executive functioning, cognition
  • basal ganglia - regulates communication between brain areas
  • limbic system - regulates emotion
25
Q

what are the potential features of ADHD brains?

A
  • changes in brain structures

- chemical imbalance of local neurotransmitters

26
Q

what are some structural differences in ADHD brains?

A

MRI studies to image the brains of children with ADHD have shown:

  • developmental delays in brain maturation compared to matched controls
  • persistent reduction in cortical volume, gyrification, surface area
  • prefrontal cortex - executive functions
27
Q

what has research noticed in neurotransmitters in ADHD brains?

A
  • some evidence that the neurotransmitters in the brain are not functioning correctly.

Noradrenaline
- attention, memory, alertness

Dopamine
- concentration, memory, motivation

in ADHD, the process of releasing neurotransmitters to activate the post-synaptic neuron is thought to be disrupted/

28
Q

what is a common treatment for ADHD? what does it do?

A

Ritalin

  • increases levels of dopamine
  • improves attention/concentration until the drug wears off
  • it also acts as a reuptake inhibitor
29
Q

what is reuptake inhibition?

A

some dopamine stays in the space between the pre and postsynaptic neurons, which can sometimes be reuptaken by neuron 1. Ritalin stops the reuptake so neuron 2 can take the dopamine.

30
Q

what are the genetics of ADHD?

A
  • heritable (runs in families)
  • twin studies show that if one twin has it, the other has a 60-80% chance of getting it
  • there are no single genes identified
  • copy number variations are linked to ADHD
31
Q

what are environmental factors of ADHD?

A
  • maternal smoking/drinking/drug use/depression

- exposure to toxins. i.e. lead

32
Q

what leads to an increased risk of ADHD?

A

polygenic genes (multiple genes that have an additive effect that contributes to the disorder) and an exposure at a critical time of brain development

33
Q

is it possible for people to outgrow ADHD? what are the rate of remission?

A
  • 55-70% of ADHD cases in remission by early adulthood
  • 80% of ADHD cases in remission later in adulthood

However, of these, 25-48% still show ADHD-like symptoms, but not enough be diagnosed.

34
Q

what are 2 theories on remission?

A

1) development of brain toward typical neuro-function

2) New atypical neuro-circuit pathways that compensate for symptoms

35
Q

who is affected by ASD? (autism spectrum disorder)

A
  • common age for diagnosis in age 5-14
  • 1 in 100 children in New Zealand
  • affects for more (5x) than girls
  • different for every child, so we get a spectrum
36
Q

how is ASD diagnosed?

A
  • diagnosed by behavioural difficulties
  • communication
  • social interactions
  • repetitive and restrictive interests
37
Q

what is level 1 autism?

A

high-functioning autism

  • needs support
  • social skills and communication skills and repetitive behaviours are only noticeable without support
38
Q

what is level 2 autism

A

autism

  • needs substantial support
  • social and communication skills and repetitive behaviours are still obvious to the casual observer, even with support in place
39
Q

what is level 3 autism?

A

severe autism

  • needs very substantial support
  • social and communication skills are repetitive behaviours severely impair daily life
40
Q

what are a few of the hypotheses regarding the biology underlying ASD?

A

framework/anatomy: structural & brain volume differences

network: atypical connectivity between regions and within specific brain regions

41
Q

what happens to brain structure of ASD?

A
  • increased brain size early in life in ASD

- evident in areas that process sensory information

42
Q

what was found in the imaging study of babies?

A
  • high-risk babies were involved in the study.
    (high risk = they have a sibling with ASD as there is a high genetic component).
  • images of developing baby/toddlers’ brains and analysis of brain volume and cortical surface area
  • 15 out of the 106 young children had developed ASD
  • diagnoses of autism was associated with increased cortical surface area at 6-12 months old and increased brain volume at 12-24 months old.
43
Q

what is the dysregulation of neuron communication in those with ASD?

A
  • research has found that there is a difference in synapse number and synaptic pruning
  • human post-mortem sample found that in controls (neurotypical) had a 45% decrease in synapse spines during childhood to adolescence (pruning)
    while ASD brains on had a 16% reduction.
  • a research with mice with a mutation in an ASD associated gene showed that they had too many synapses and had difficulty learning motor skills?
44
Q

what is brain connectivity like in ASD brains?

A

too many poor connections and poor communication between various regions of the brain

45
Q

what has been found about brain connectivity in human imaging studies?

A
  • ASD has weaker long-range connections (between brain regions)
  • have additional local connections = brain wiring/organisation is atyoical

however, some studies have also identified regions with hypo-connectivity

46
Q

what does ASD potentially result from?

A
  • ASD potentially results due to rapid brain growth and impaired synapse pruning
47
Q

what are the genetics of ASD?

A
  • there is no single “autism gene”, there are more than 881 genes implicated in ASD
  • 25% of individuals with autism have a known genetic condition (e.g. a disorder that also results in autism characteristics)
48
Q

what are non-genetic causes that have been proposed for ASD?

A
  • prenatal development, low birth weight
  • immune reaction, especially in utero
  • environmental factors, a possible link with pollution
49
Q

what are the theories of the sex differences in ASD diagnosis?

A
  • female protective effect
  • males are more susceptible
  • chromosome (XX XY)
  • hormonally driven
  • extreme male brain theory
  • underdiagnosis of females?
50
Q

what is the female protective effect?

A
  • females who meet diagnostic threshold for ASD will carry a higher mutational load than males
51
Q

what is meant by males being more susceptible?

A
  • males exhibit greater genetic variability, allowing for an increased incidence
52
Q

what do the chromosomal differences mean for ASD?

A
  • one main difference between males and females is the sex chromosomes
  • however, most genetic mutations associated with ASD susceptibility are autosomal
53
Q

how do hormones drive ASD?

A
  • one main difference between males and females is the sex hormones (testosterone and estrogen)
  • higher testosterone during development associates with ASD?
54
Q

what is the extreme male brain theory?

A
  • states that there are morphological and functional differences between male and female brains, but the “autistic brain” is a more extreme, or hypermasculinized, version of the male brain.
55
Q

what is thought about the underdiagnosis of females?

A
  • females with ASD are more likely to present with co-occurring conditions such as intellectual disabilities, seizures, anxiety
  • females may present differently
56
Q

what is a limitation of understanding childhood disorders? how can this be overcome?

A
  • we are limited by our understanding of biological processes and pathologies in the body
  • the more research that gets done, the better our knowledge of how biological processes happen in the typical and atypical state, leading to better strategies for treatment, intervention and cures.

CMHC201 (15 decks)

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