chapter 4: prenatal development Flashcards
prenatal development
the development of humans before they’re born
postnatal development
the development of humans after they’re born, especially in infancy
stages of prenatal development
o Zygote – first two weeks
o Embryo – 2-10 weeks (the period when organs develop)
o Foetus – after week 10 until birth
indirect methods for studying prenatal development
non-human models of prenatal changes in brain and behaviour + human embryos and foetuses that died + testing perception and memory of neonates (infants who’re less than a month old)
direct methods of studying prenatal development
measurement of autonomic nervous system activity with external stimulation + phenotypes (characteristics, capacities and patterns of activity) + placing a foetal ultrasound cardiotocograph sensor around the maternal abdomen that can record the heartrate and movement + using fMRI and MEG
aproptosis
programmed death of cells
when does organogenesis end
8 weeks
stages of zygote
o Zygote – day 1, fertilized egg
o Morula – day 3, ball of 16 cell, cell differentiation starts
o Blastula – day 4-7, cavity arises, embryo arises out of inner cells, implantation in uterus
what’s gastrulation
formation of the 3 germ layers by migration and differentiation of blastula cells
layers of blastula cells
ectoderm - skin, hair and nervous system
mesoderm - muscles and bones
endoderm - most other organs
neurulation
ectoderm - neural plate (18 days) - neural tube (cranial-caudal organization)
when are cells for different parts of the brain differentiated
18 days
what happens when the closing of the neural tube fails
spina bifida (open back) + anencephaly or open skull (usually miscarriage or death shortly after birth)
folic acid during first 12 weeks - helps
neurogenesis
the birth of neurons
cerebral cortex
the area of the brain that is associated with complex tasks (memory, language, thoughts, control and integration of movement and the senses)
when do cerebral hemispheres begin to arise
9 weeks
when do the cells in the cerebral hemisphere proliferate and migrate
4 months
when is the surface no longer smooth and what appears then
6 months, sulci (groove), gyri (ridges)
when does the process of inhibition become function and what happens then
15 weeks - period of reorganisation of behaviours – reflexive neuronal circuits are still in place, now controlled by more sophisticated nerve cells in the new higher centres
when is the number of cells in the cerebral cortex mature
27 weeks - but at birth the brain is only at about 25% of its full adult volume (myelination)
lobes and their function
Frontal lobes – associated with movement, parietal lobes – sensations, temporal lobes – hearing, memory, sense of self and time, occipital lobes – visual centre of the brain
+Association cortex – surrounds the primary sensory areas, longer development (concerned with higher cognitive and integrative function that develop with experience)
what brain regions are the same and different than adult?
Same – sensory and motor networks
Different – emotion and control
pattern of rest and activity at 34 weeks
20-30% of their time in quiet, motion-less sleep with a steady heartbeat and breathing movements that are rhythmic
rest of the time - the same as newborn active sleep - many different body movements, eyes moving rapidly back and forth + heart and breathing rate are irregular + responsive to the sensory stimuli they’re exposed to +fewer general body movements + breathing movements
does the baby move at 38 weeks
longer periods of deep sleep - rest periods of about 80-100 minutes
development of touch
8 weeks – if the area around the lips is stroked – foetuses will respond by moving
10 weeks – foetuses will curl their fingers in a reflexive grasp when their palm is touched
12 weeks – their toes will curl when soles are touches
rooting reflex
the reflex that causes newborn babies to respond to one of their cheeks being touched by turning their head in that direction – helps them nurse
chemosensory system
encompasses both the gustatory (taste) and olfactory (smell) senses
how can infants experience taste stimulants
mouth, nose, blood
when are nose plugs gone
4th month