Lecture 5 Flashcards
What develops 16 weeks after fertilization?
cerebral expansion and commissures
prosencephalon develops dramatically
What develops 3 months after fertilization?
basic structures established
What develops 5 months after fertilization?
CNS myelination begins
What develops 7 months after fertilization?
lobed cerebrum
What develops 9 months after fertilization?
gyri and sulci
What do cells have to do during development?
migrate
differentiate
become defined
What are commissures?
Connections between the brain and the heart
What are the composition changes in myelin?
galactolipids and protein compounds increase
When does myelin form?
5 months post fertilization in humans
10 days post fertilization in rats
How much “body weight” do oligodendrocytes produce perday?
3 times
When does myelination stop?
Most over by two years but some in late teens (in neocortex)
When are critical periods of development and how were they found?
6th week, 9th week, 5th to 10th weeks
Rubella infection
What abnormalities occur if the fetus is infected with rubella before the 6th week?
Eye malformations e.g. cataract
What abnormalities occur if the fetus is infected with rubella before the 9th week?
Deafness (organ of corti)
What abnormalities occur if the fetus is infected with rubella before the 5th to 10th week period?
Cardiac malformalities
What disorders can form in the second trimester?
CNS disorders
When does the risk of abnormalities fall?
16 weeks
Why is the fetus susceptible to fetal alcohol syndrome?
Alcohol causes placenta
Fetus doesn’t clear alcohol well
Fetal levels higher
What are major symptoms of fetal alcohol syndrome?
facial abnormalities microcephaly loss of cells loss of fibers e.g. callosal agenesis Disturbed migration Irritability - neurons are more excitable Motor and intellectual impairment
Name two examples of drugs of abuse and disorders that can be caused by them
Opiates - neonatal withdrawal Cocaine - hypoxia, abortion, withdrawal, cognition Ecstasy - long-term FX on hippocampus, other FX certain Cannabis - long-term cognitive FX
What animal model was used to study drugs of abuse?
rhesus monkeys
Whereabouts of the brain does cocaine affect?
Where mitosis occurs
What is the speed of conduction during the neonatal period?
20-25 m/s
What is the speed of conduction during the first six months after birth?
32-50 m/s
What is the speed of conduction during the 6th to 12th month after birth?
33-60 m/s
What is the speed of conduction from the 12th to 24th month after birth?
40-60 m/s = adult speed
Why is it important to discuss when the fetus starts to feel pain?
- Increasing use of interventional procedures and abortion debate
- Sentient conscious aspect of independent human
- Difficult to come to a conclusion; series of effects need to happen for the possibility to feel pain
- Somatosensory input
What can be the “series of effects” that need to happen for the possibility of pain?
Receptors must connect to the PNS/hypothalamus to relay signals
Connections and structures must be present
What are examples of somatosensory input?
Pain requires connection of receptors, sensory neurons, thalamasu and cortex
When does innervation of dermal skin and subdermal skin happen?
dermal: 28 weeks
subdermal: 6-8 weeks
What happens from 8 weeks?
DRG connection (non-noxious)
What happens from 19+ weeks?
C-fiber (noxious stimuli) connection
When does reflex response to noxious stimuli happen in preterm infants?
23 weeks
Is a reflex response a conscious perception of pain?
no
What happens from 28 weeks?
facial responses to heel lancing
Is a sub-plate considered a cortex?
No; it is a developing cortex
The organized thalamus forms when?
8+weeks
When do retinal inputs arrive?
14-16 weeks
What happens at 25 weeks?
Myelination
What happens at 24 weeks?
Connections from the thalamus to cortex form.
When do evoked potentials in the cortex form?
From 29 weeks or earlier
What do recent studies suggest when finding the beginning period of pain?
24 weeks because cortical responses have been found
What are well-developed at birth?
taste, smell, hearing
Is there a difference between bottle-fed and breast-fed babies?
Breast-fed babies can differentiate between their mother and other woman’s breast pads while bottle-fed babies prefer any lactating female
From what period can babies locate sounds?
3 days
From when do the eyes become vision-sensitive?
7 months
Are the optic nerves myelinated at birth?
no
When does vision become sharper?
6 months?
Why does vision become sharper overtime?
Development of ocular dominance columns
When is color vision considered to be good?
2 months
Where do babies writhe?
E28-32
Name 7 examples of postnatal reflexes?
Moro (startle) complex Stepping Palmar grasp Swimming Babinski reflex Rooting Sucking
What is the moro complex?
baby supine - remove head support
trunk extension
cycle of limb extension (adbuction from midline)
and limb flexion (adduction to midline)
When does the moro complex go away?
after 3 months
What is stepping?
Holding up feet onto surface
When does stepping go away?
After 6 weeks
What is the Palmar Grasp?
May support own weight and is involved in the development of inhibition
When does the palmar grasp go away?
3-4 months
Does swimming happen in all babies?
no
When does swimming go away?
After 4-6 months
What is the Babinski-reflex?
Neonates fan toes when sole is stroked?
What happens to the Babinski reflex as an adult?
Adults curl their toes instead of fanning
What happens to adults with descending motor tract damage?
Adults start to fan toes
What are examples of descending motor tract damage causes?
MS, spinal cord damage
What is rooting?
When the baby opens the mouth and moves the head about for nipple seeking after their cheek is stroked
When does rooting go away?
after 4-7 months
What are examples of co-ordinated responses post birth?
reaching
language development
When does reaching start?
5 months old
When do babies start to attain objects from reaching?
8-9 months old
When do infants start to sow adult motor patterns?
2 years old
