Week 15: Development Flashcards
(30 cards)
Haploid
Half chromosomes
The germinal period
8-10 days after egg and sperm unite and lasts for 2 weeks
Diploid
Full set of chromosomes
Gametes
Mature reproductive cell (haploid) egg and sperm
Zygote
The new cell at conception from the formation of the egg and sperm
Cleavage
Cell dividing into 2 then 4 then 8. Occurs 24 hours after fertilization
Morula
Spherical mass of divided cells
Stem cells
Unspecialized cells
Inner cell mass
The inner cells of the morula which will eventually become the embryo
Trophoblast
Outer cell lining of the blastocyst and will eventually form a protective layer around the embryo > extra embryonic layer & placenta that transports nutrients, oxygen and metabolizes across the membrane.
Blastocyst
Stage that a fertilized egg reaches 5-6 days
Neurulation
The process of a neural tube forming within an embryo > formation of the nervous system and the brain and CNS.
Neurogenesis
6-7 weeks after conception.
Embryonic Period
Eight weeks long and begins as soon as implantation within the uterine wall occurs.
Neural migration
Process of the movement, connection and organization of neural cells to form the mature brain.
- genetic instructions
- time & place of neurogenesis
- interactions with glial cells
- chemical genetic and environ signals
- largely unknown!
Embryonic development occurs in what directions?
Cephalocaudaul - most intensely at the head and work downwards
Proximodistal - from the centre of the organism outwards
Cell apoptosis
Programmed cell death that is a crucial part of development.
THINK: webbed cells between fingers must be reabsorbed in order to have digits instead of a fop appendage.
Foetal period
9th week after conception to birth.
Beginning of the foetal period: 30 grams x 4cm (my eraser)
10 weeks: breathing movements to practice muscle for birth not to obtain oxygen
4th month: sleep and wake patterns are detected and large enough for the movements to be noticed
5th month: vestibular system (balance & spatial coordination), responsive to sound, foetal heart beat changes in response to mothers voice, recognizes mothers voice
6th month: 700 grams and 30cm can be premature but obvi better in utero
6-8 month: heartbeat responsive to light stimulation, tastes (show a preference to foods that mom ate while in womb) and movement stops (to facilitate growth of inhibitory neural pathways)
8-9 month: grows 250grams per week until birth
Cat in the hat study
- memory in prenatal development
- mom read cat in hat 2 x a day
- after birth baby was given soother that would play cat and hat story or another story read by mom depending on the amount of sucking
- baby adjusted sucking to plays at in hat
Teratogen
Alcohol, heavy metal - mercury, some medications.
- the earlier the foetus is exposed the worse the effects
- will affect very mother and foetus differently
- the greater the amount and the longer it is exposed it will have a greater affect.
Famous teratogens
Alcohol > Foetal alcohol spectrum disorders
Smoking > lowered IQ and behavioural problems
Medication > Thalidomide was prescribed to mothers and left devastating effects
Diseases > rubella in prenatal infants can cause congenital heart disease, deafness, blindness or mental retardation. Influenza has been correlated with schizophrenia.
Reflexes
In infants there are many types of reflexes that are eventually replaced with voluntary behaviours.
Explanation for increasing cognitive complexity?
- not the number of neurons since it’s the greatest when we are born (18 weeks after conception)
- complexity of existing neurons: synaptogenesis occurs at a rapid pace after we are born to form all of the synapses we will ever have from birth to age 1.
Synaptic plasticity
Neurons can grow or shed connections to other neurons in order to accommodate their own activity levels.
