Hereditary and Brain Development, Prenatal Development

Polygenetic Inheritence + Polygenic traits

Polygenetic inheretence: Multiple genes contribute to a single characteristic

Polygenic traits: Trait produced by those genes

Phenotypic Plasticity

The degree to which environmental factors affect a given trait

Low plasticity vs High plasticity

Low: Traits change very little in response to environment

High: Traits are easily changed. Physical, biochemical, or behavioural traits

Canalization

Phenotypes that remain unchanged regardless of the environment

Norm of Reaction

The range of possible phenotypes for a given genotype

How can we describe genes and environments in the context of Norm of Reaction?

Genes: boundaries and limits

Environments: ranges

Epigenetics

The complex process where environments shape the expression of the genetic code

Rat example for Epigenetics

Mother rats licking (environment)

Activate glucocorticoid receptor genes (genotype)

These genes are involved in stress reactivity (phenotype)

Neurons + their role in one word

Basic units of the brain and nervous system

• communication

Synapses

Connective spaces between neurons

Glia Cells + what do they produce?

Cells that surround and protect neurons

Myelin sheath protects and nourishes

Neurogenesis

Increase of neurons through cell division

3-4 weeks to 18 weeks after conception

Migration

New neurons moving to where they will serve their ultimate purpose

Synaptogenesis + when does it start?

Neurons form synapses with other neurons

• starts in the prenatal period, with rapid development right before and after birth

Aborization + Overproduction

Aborization: the growth and branching of dendrite trees

Overproduction: More synapses produced than will actually be used

Synaptic Pruning + when does it happen?

Elimination of excess synapses, determined by experience

• happens from prenatal period to late adolescence

What is Aptosis

Death of neurons

Myelination + when does it happen?

Insulating myelin forms around axons

• prenatal to early adulthood

Brain Plasticity

The capacity of the brain to be shaped and affected by experience

Experience-Expectant Plasticity + Examples

The normal wiring of the brain as a result of general experiences that human infants normally have

Ex: Visual stimulation, language exposure

Experience-dependent Plasticity + example

Changes in brain wiring that occur as a response to their unique life experience and circumstances.

ex: enriched vs impoverished environment

Timing of experience: Critical Periods

Times when specific experiences result in permanent changes in a child’s brain that cannot be altered

Timing of experience: Sensitive Periods

Times in development when the brain is most susceptible to experiences, but changes are still reversible

Dandelion Children Susceptibility

Low susceptibility (resilient)

• Able to cope with stress and flourish despite environmental challenges

Orchid Children Susceptibility

High susceptibility (low resilience)

• Wilt when faced with environmental challenges

Amount of chromosomes in a zygote

46 → 23 from each parent

Twins: Dizygotic

2 eggs fertilized

(1 in 125 births)

Twins: Monozygotic

1 egg fertilized and split

(1 in 250 births)

The period of the Zygotye

Germinal period (weeks 1-2)

• time from conception to implantation

The period of the Embryo

Embryonic period (weeks 3-8)

The period of the Fetus

Fetal period (week 9-birth)

What 4 things to the Zygote cells do?

Cell:

• Division

• Migration

• Differentiation

• Aptosis

Inner Gastrulation + example

Embryo

ex: neural tube

Outer Gastrulation + example

Supporting system

ex: umbilical cord, placenta, amniotic sac

What are the 3 layers of the embryo cells?

1. Ectoderm (outer)

2. Mesoderm (middle)

3. Endoderm (inner)

Ectoderm components (5)

Nervous system

Sensory organs

Nails

Teeth

Outer surface of the skin

Mesoderm components (5)

Muscles

Bones

Circulatory system

Inner layers of the skin

Internal organs

Endoderm components (2 categories of systems)

Digestive and respiratory

Cephalocaudal Development

Head before body

Arms before legs

Proximo-distal Development

Center of the body before other areas

What is the age of viability for the Fetus?

22-28 weeks

When does labour start?

Approx 38 weeks

What are the 3 stages of labour and how long do they last?

1. Contractions cause the cervix to open, dilate, soften, and thin (8-14 hours)

2. Contractions propel the fetus down the birth canal (30 min-1.5 hours)

3. Placenta is expelled (5-10 mins)

What is a reflex and what are 6 survival reflexes? (BBRPSS)

Reflex: involuntary, automatic response to a stimulus

• Breathing

• Blinking

• Rooting

• Pupillary

• Sucking

• Swallowing

What are 5 Primitive Reflexes?

• Babinski (toe thing)

• Palmar

• Moro (weird reaching thing)

• Stepping

• Swimming

What is the proportion of REM sleep in newborns VS 6 month olds

• 50% of newborn sleep

• 25-30% of 6 month old

What is the autostimulation theory to explain why newborns do so much REM sleep?

The high brain activity and twitching during REM helps build the central nervous system and visual pathways because it provides internal stimulation