PSYC 100 Lecture Notes - Lecture 14: Amniotic Sac, Morula, Trophoblast
12 Jun 2018
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Week 14: Developmental Psychology I: Physical and Lifespan Development
Topic 01: Prenatal Development
• Germinal Period
o The first two weeks after the sperm and egg unite
o Sperm and ova are both gametes which are haploid
o During the germinal period, the zygotic cell divides multiple times, creating numerous
identical copies that hold together in a spherical shape
o These divisions occur through cleavage- the division of cells in the early embryo to form
blastomeres
o After a few instances of cleavage, the resulting spherical mass of cells is known as a
morula
• Stem Cells: Undifferentiated cells that can divide and produce any one of a variety of
differentiated cells **epigenetic modification
• Blastocyst:
o As the morula enters the uterus, it fills with fluid
o Here the cells begin to differentiate, forming two layers:
▪ Inner Cell Mass: The mass of cells inside the morula that eventually will form the
embryo
▪ Tropholast: The ell’s that for the outer layer of a lastoyst
• Embryo: The development stage preceding the foetus
• Blastocyst- The stage a fertilized egg reaches 5-6 days after fertilization
• After the zygote becomes a blastocyst, the trophoblast (outer layer of blastocyst) eventually
develops into extra-embryonic tissues, including the placenta, and controls the exchange of
oxygen and metabolites between the mother and embryo
• The trophoblast later transforms into two parts; the amniotic sac and the placenta
• In the embryonic period, the embryo separates into 3 layers:
o Endoderm: The innermost layer of tissue, eventually develops into the digestive system,
urinary tract and lungs
o Mesoderm: The middle layer, transforms into muscle, bone and the circulatory system
o Ectoderm: The outer layer, develops into skin, hair, teeth and the central nervous
system
• Neural Tube: The eryo’s preursor to the etral erous syste
• Neurulation: The formation of the embryonic nervous system, which will develop into the brain
and central nervous system
• Neurogenesis: The process by which neurons are generated, begins 6 or 7 weeks after
conception
• Neural Migration: The process through which neurons move, grow and connect as the basic
neural tube develops into a more mature brain
o Factors that influence migration: timing and location of neurogenesis, interaction with
glial cells and a combination of genetic, chemical and environmental signals
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• Embryonic development proceeds according to two patterns:
o Cephalocaudal: Development occurs most intensely at the head and proceeds
downward toward the body
o Proximodorsal: Development proceeding from the center of the organism outward
• Apoptosis: The genetically programmed process of cell death as part of normal development or
normal functioning of cells and organs
• The foetus:
o Start of the stage occurs 9 weeks after conception, foetus weighs 30g and is 4cm long
o At 3 months- majority of organ growth is complete. The foetus begins making breath-
like motions
o End of 4 months- Sleep and wake patterns emerge, foetus is now large enough for
mother to detect movement
o 5 months- the vestibular system begins to develop, foetus becomes responsive to sound
o 6 months- 700g and 30cm long
o 7-9 months, foetus experiences taste
• Teratogens: External compounds that can cause extreme deviations from typical development if
introduced to the developing organism
o Alcohol- Foetal Alcohol Spectrum Disorder
o Tobacco
o Prescription drugs
o Viruses
o Stress
o Nutrition
Topic 02: Childhood:
• Reflexes: Rooting (turning head and opening mouth when feeling something on cheek), sucking,
Babinski (stroking under an infants foot will cause them to fan and curl toes), tonic neck,
stepping, moro (putting arms and grasping if they feel like they are falling) and eye blink
• Growing in the brain:
o When we are born, we already possess most of the neurons we will ever have
(neurogenesis)
o Synaptogenesis: The process through which new synapses are formed between neurons
o Synapses: Connections through which neurons communicate with each other
o This is where our advanced cognitive skills come from
o Synaptic Pruning: Facilitates a change in neural structure by reducing the overall number
of synapses, leaving more efficient synaptic configurations
• Brain plasticity:
o Experience- Dependent Plasticity: The ability of the nervous system to wire and rewire
itself in response to lasting changes in environment/experience
o Experience Expectant Plasticity: Development that will not happen unless a particular
experience occurs during its critical period ex. Language
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Document Summary
Week 14: developmental psychology i: physical and lifespan development. Topic 02: childhood: reflexes: rooting (turning head and opening mouth when feeling something on cheek), sucking, Language: classical conditioning: conditioning is the primary mechanism through which children learn about the world, ex. Albert b- when albert reached for a white rat, the stimuli, they would produce a loud sound that would scare albert. After a few exposures, the rat was paired to the frightening noise and albert began to display fear. Intermittently reinforced behaviour is sometimes not rewarded, which affects the expectations of the reinforcement. Microsystem: consists of you and your relationships with those in your immediate surroundings ex. Mesosystem: made up of connections between different relationships you have within your microsystem: 3. Exosystem: refers to those settings that you might not directly experience but remain influenced by: 4. Macrosystem: refers to larger social constructs that shape your environment in less direct ways ex.
