Chapter 3/4 Flashcards
adaptive reflexes in infancy
- palmar reflex
- sucking reflex
- rooting reflex
- stepping reflex
- plantar reflex
palmar reflex
- occurs when something is placed in the palm of an infant’s hand and the infant quickly wraps their fingers around the object
- forces them to practice grasping in order to prepare them to pick of objects
sucking reflex
- occurs when something touches the roof of an infant’s mouth
- 2 aspects: expression (to express milk from a nipple by pressing it between their tongue and the roof of their mouth) and milking (moving tongue from areola to nipple to coax milk from breast)
rooting reflex
- occurs when anything strokes an infant’s cheek or corner of their mouth -> infant will turn their head towards the side that was touched
- helps them search for breast b/c they don’t have neck muscles
- rooting indicates hunger
stepping reflex
- occurs when the soles of an infant’s feet touch a flat surface -> they will life their legs as if they are marching or stepping
- tries to trigger areas in the brain related to walking
plantar reflex
- infant’s tendency to curl their toes down or away from their shin
- exercises ability to use feet for grasping, but this goes away because adults don’t reinforce it
what is the purpose of adaptive reflexes in general?
they enable infants to perform crucial motor skills which they otherwise wouldn’t be able to do due to insufficient brain development at birth
neuronal proliferation
- rapid production of neurons during the 10th-18th weeks of prenatal development
- because of this, most fetuses have produced all of their neurons by the 28th week of prenatal development
why can’t babies perform so many motor skills, even if they have all their neurons?
- neurons aren’t tightly packed together -> have synapses/gaps between each other
- neuron structure must further develop in order to communicate across the gaps
when do neurons consist of cell bodies only?
when they’re travelling from the neuron-manufacturing site
dendrites and axons
- allow neurons to form connections with other neurons
- allow neurons to communicate with other neurons
- are stimulation-dependent
dendrites
bring info from other neurons to the cell body (to receive info from other neurons)
axons
take info away from the cell body to other neurons (to send info to other neurons)
synaptogenesis
although a few neurons have formed synapses in pre-natal period, this mass production of synapses (dendrite and axon growth) occurs during infancy and toddlerhood
synaptic pruning
- the retraction/elimination of unused synapses
- synapses are activity dependent (need stimulation to survive) - if we don’t use it, we lose it
why are so many synaptic connections eliminated/pruned?
- inactivity (use it or lose it)
- initially the neuron produces a huge over-abundance of synaptic connections
advantage of synaptic pruning
- enables neurons to communicate with each other more efficiently (operational efficiency)
- this efficiency is accomplished due to greater specificity (automaticity) in synaptic connections
neuroplasticity
brain’s ability to reorganize/regenerate synapses from repeated stimulation/activity (helpful after a stroke, for example)
glial cells
- responsible for a lot of brain development in newborns
- responsible for myelination of axons
- different from neurons
myelination
- improves speed/efficiency of message transfer between neurons
- most rapid during the first 2 years after birth
- myelin = fatty substance
what 2 major things happen in our brain after birth?
- synaptogenesis (increase in axons and dendrites)
- myelination of axons (increase in number of glial cells)
involuntary/voluntary transition period
- involuntary = controlled by reflexes
- voluntary = adequate brain development to control movement
- during this period, it’s common to notice a decline in some of an infant’s motor skills
- ex. grasping skills - infants can grasp objects at 0-1 month, then from 2-3 months they can only swipe them, them at 4-6 months they can voluntarily grab objects
3 stages of prenatal development
- germinal
- embryonic
- fetal
germinal stage
- 1-2 weeks
- conception and implantation in uterine wall
