Age-Dependent Changes/Ageing Effects of Nervous System

Neurogenesis, neural proliferation/migration, folding

Neurogenesis starts at three weeks in utero = formation of neural plate, groove and tube (neural tube becomes brain vesicles)

Around week 12 = gradual thickening of cortex/formation of cortical layers

Around mid-gestation = gyrification and first primary sulci form

Neuronal connectivity

Starts in utero and continues to develop after birth

Around week 12 in utero = neuronal connectivity starts, gradual thickening of cortex, formation of cortical layers

Around mid-gestation = direct contact between cortex and rest of GNS, gyrification, first primary sulci form

Myelination

Starts at end of third month in utero = starts with peripheral sensory nerve then spinal cord

Continues through childhood adolescence well into fourth decade

Shows correlation between achieve of developmental milestones and nervous system development

Synaptogenesis

Starts in utero = immature synapses form, undergo maturation and convert from silent to active state

Synaptic number is reduced to refine neural connections

Synaptic pruning

Process of synaptic elimination that is completed by the time of sexual maturation, influenced by environmental factors, associated with learning

In early adolescence, synaptic pruning = ongoing myelination of brain and thinning grey matter, oestrogen/testosterone promote ns growth and pruning

What happens to the nervous system with age

Deteriorates with age disregarding diseases

Rapid decline in brain weight, reduced bulk of gyri, widening of sulci, reduction of synaptic connections/neurons, reduction in biochem activity (reduced ion channels, number of receptors and levels of neurotransmission)

Signs of NS ageing

Altered sleep patterns, changes in mood/irritability, loss of appetite/constipation, loss of memory, reduced motor control, weakened/loss of reflexes