Module 2 Flashcards
(Module Notes AND Textbook Chapter)
Each one of us originated from what two germ cells?
A sperm and an ovum.
How are germ cells produced?
Through meiosis.
Define meiosis.
The cell division process that results in a germ cell containing 23 chromosomes.
True or False?
Females are born with all of their ovum, whereas males make sperm continuously.
True.
During conception, an average of how many sperm are released into the female and make their journey to attempt to fertilize the egg?
500 million.
(the sperm must swim for 6-7 hours to reach their destination.)
From the initial 500 million candidates, only about __________ sperm actually get close to the egg.
200.
Some sperm fail to reach the egg due to chance factors, while others fail due to _________.
Genetic defects.
Where does fertilization of the egg normally occur?
In the upper third portion of the fallopian tube.
What is a zygote?
A fertilized egg cell.
(Prenatal development has begun.)
Prenatal development is broken into what 3 main stages?
1) The germinal period (weeks 0-2)
2) The embryonic period (weeks 3-8)
3) The fetal period (weeks 9-birth)
What happens during the germinal period (the first 2 weeks of development)?
The zygote is rapidly dividing. Approximately 4-5 days after fertilization, the zygote enters the uterus from the fallopian tube. The zygote is now referred to as the blastocyst – it forms as a hollow ball of cells and will implant into the wall of the uterus. The germinal period comes to an end when the blastocyst is fully embedded, which takes about one week.
What happens during the embryonic period (implantation to 8 weeks)?
Cell differentiation begins and the beginnings of all organ systems are forming. Embryonic development follows a cephalocaudal pattern of development, meaning that areas near the head tend to develop first. By the end of the embryonic period, all bodily systems are functioning.
What are some key features of the embryonic period?
1) Three layers of cells differentiate:
Ectoderm: The ectoderm will become the nervous system, nails, teeth, inner ear, eye lens, and epidermis.
Mesoderm: The mesoderm will become muscles, bones, circulatory system, and skin.
Endoderm: The endoderm will become the digestive system, lungs, urinary tract and glands.
2) Nervous System Development - The neural tube also forms during this period, which is the precursor to the Central Nervous System. The neural tube is created when the ectoderm folds in on itself, creating a u-shaped groove.
3) Embryo Support System - This includes the amniotic sac (a liquid-filled sac in which the embryo floats, helping to protect it and maintain a constant temperature) and the placenta (which has numerous functions, including allowing nutrients, oxygen, and waste to pass through, while at the same time preventing maternal blood from mixing with the blood of the developing embryo.)
What happens during the fetal period (weeks 9-birth)?
Development continues to be rapid and cephalocaudal in nature. Around 11-12 weeks, the fetus starts to become more active (spontaneous movements, reflexes) although movements are not felt by the mother until the fetus becomes larger, usually around 16 weeks. By 20 weeks, the fetus starts to have facial expressions and begins putting on weight.
____________ weeks is considered the age of viability (the point at which the brain and lungs are developed enough for survival without major medical intervention).
a) 28 weeks
b) 23 weeks
c) 21 weeks
d) 24 weeks
b) 23 weeks.
True or False?
An active fetus is likely to become an active newborn.
True.
Fetal movement helps promote muscle development. Interestingly, there are large individual differences in prenatal activity, with these differences continuing into infancy. In other words, an active fetus is likely to become an active newborn.
A fetus experiences some degree of sensory input from all five senses, although __________ input is minimal.
Visual.
Since a fetus can move around, it can experience ________ sensations such as kicking the walls of the uterus.
Tactile.
True or False?
Amniotic fluid contains both odours and flavours (related to what the mother ingests), which a fetus can smell and taste.
True.
Researchers suspect that this may be one way in which cultural flavour preferences are transmitted.
A fetus can hear the world around them. This includes both the _______ world (e.g., mom’s heartbeat) and the _______ world (e.g., voices of their family members).
maternal, outside
When discussing fetal learning, we are only considering learning in its most simple form - and ___________.
habituation and dishabituation
(Researchers examine whether a fetus gets “bored” of a stimulus and if interest peaks when the stimulus is changed. Indeed, research suggests that the nervous system of a fetus is developed enough to engage in this type of basic learning (e.g., they habituate to repeated stimuli). A fetal brain, however, is not yet developed enough to engage in more complex forms of learning.)
Which of the following statements is NOT true about the period of the embryo?
a) It begins when the developing organism is fully implanted in the uterine wall.
b) It lasts from weeks 3-8 of a pregnancy.
c) All of the major organ systems are functioning before the end of this period.
d) All of the major organ systems are fully integrated with one another before the end of this period.
d) All of the major organ systems are fully integrated with one another before the end of this period.
What period of prenatal development last between 3-8 weeks?
The Embryonic Period.
What is a teratogen?
An external agent that can cause damage or death during prenatal development. (textbook definition)
Anything that has an adverse impact on development. (module definition)
List some examples of teratogens.
Chemicals
Medications
Recreational Drugs
Alcohol and Nicotine
Some Viruses and Bacteria
Maternal Health
The impact that a given teratogen will have on a developing fetus depends on many factors. List some of these factors.
Type of Teratogen
Dosage
Duration of Exposure
Timing of Exposure
Genetics of the Mother
Genetics of the Fetus
What is one of the most infamous teratogens?
Thalidomide - a medication that was approved for pregnant women without proper testing. Thalidomide resulted in serious birth defects for newborns who were exposed in utero.
____________ during pregnancy is one of the leading causes of preventable birth defects and developmental disabilities.
Alcohol use.
Exposure to teratogens during the ___________ period can result in major structural abnormalities.
(For example, exposure to alcohol can have significant impacts on major systems like the CNS.)
Embryonic.
Teratogen exposure during the _____________ period is more likely to result in physiological defects or minor structural abnormalities.
Fetal.
(Major structural defects are less likely in the fetal period because the basic organ systems are already in place.)
Not all pregnancies with such teratogen exposures will result in birth defects. What are 2 reasons why?
1) First, there is a dose-response relationship between exposure to teratogens like these and the likelihood of negative outcomes. In other words, the higher the dose, the greater the likelihood of negative outcomes.
2) Second, both maternal and fetal genetic susceptibilities (e.g., variation in the rate a drug will be metabolized) influence the final outcome.
Longitudinal research indicates that children exposed to cannabis early in development are at a greater risk for attention deficits, increased hyperactivity, and increased likelihood of _________.
substance use.
Which of the following statements is most true about the effect of alcohol on the developing baby?
a) The more mothers drink, the more likely it is to have an effect on their child; however, some babies will be unaffected due to their mother’s and/or their own genetic endowments.
b) The more mothers drink, the more likely it is to have an effect on their child; however, some babies will be unaffected due to the mother’s genetic endowments.
c) Babies will only be affected by mothers who drink in the last trimester.
d) All babies will be affected equally by mother’s drinking.
a) The more mothers drink, the more likely it is to have an effect on their child; however, some babies will be unaffected due to their mother’s and/or their own genetic endowments.
Which of the following are teratogens?
Alcohol
Sunshine
Cocaine
Phenytoin (Seizure medication)
Sushi
Varicella (Chickenpox)
Maternal exercise
Alcohol, Cocaine, Phenytoin (Seizure medication), Varicella (Chickenpox)
Every cell in your body contains chromosomes. Humans have _____ chromosomes, divided into _____ pairs.
46, 23
(We obtained one pair of chromosomes from each of our parents through meiosis.)
Chromosomes are made up of _____________.
DNA (deoxyribonucleic acid).
DNA carries all of the “instructions” for making a person, which are packaged in genes. Importantly, genes code for __________, NOT for specific behaviors.
proteins
(Proteins are the key ingredient that determines a cell’s characteristics and functions.)
What are alleles?
Different forms of the same gene. This “back up copy” is helpful to ensure proper development.
Very few human traits follow basic Mendelian patterns. In other words, _____________ is responsible for most human traits.
polygenic inheritance
Define genotype.
The genetic material an individual inherits.
Define phenotype.
The observable expression of the genotype, including both body characteristics and behaviour.
What do epigenetic “markers” do?
They control where and how much protein is made by a gene, effectively turning the gene “on” or “off”.
This occurs naturally during prenatal development when cells are differentiated (e.g., one cell becomes a brain cell while another becomes skin). It also occurs from environmental influences. Where you live, what you eat, who you interact with, and what you do in daily life impacts your gene expression. In other words, environmental experiences leave “marks” on our genetic information that changes how they are expressed
What is the study of behavioural genetics?
The study of how nature and nurture contribute to behaviour.
Specifically, behavioural genetics tries to determine how much variation in behaviour is the result of environmental versus genetic factors.
What is a twin study?
It compare monozygotic (identical, 100% genetic similarity) twins to dizygotic (fraternal, 50% genetic similarity) twins.
Researchers typically assume that the twins were raised in the same environment. This is one reason why dizygotic twins are used instead of siblings, as dizygotic twins have more similarity in their environment (starting from the womb!).
What is an important limitation in twin studies?
Even for twins, their environment is rarely 100% shared. For example, consider twins who might be in different classrooms at school – these children would have different teachers and different friendships.
What is an adoption study?
It looks to see if offspring become more similar to their biological parents or to their adoptive parents.
If they become more similar to their adoptive parents on a given trait (e.g., reading ability), we can assume there is an environmental contribution. On the other hand, if the children become more similar to their biological parents on a given trait (e.g., shyness), w
What is an important limitation in adoption studies?
There is little environmental variation in adoptive families. Most adoptive families are in the middle-class, so it is difficult to disentangle environmental and genetic influences in high-risk environments.
Define heritability of traits.
The percentage of variance in a population due to genes.
Heritability estimates range from 0-1. What does 0 mean? What does 1 mean?
0 means the variation in a trait is completely due to environmental factors.
1 means that 100% of the variation in a trait is completely due to genetic factors.
True or False
Heritability and heredity are the same thing.
False.
Heredity is the passing of traits from children to offspring, whereas heritability is a statistic looking at the proportion of variance in a trait that is due to genetics.
Heritability is measure at what level?
a) Individual
b) Population
b) Population.
A heritability estimate of .40 for shyness does NOT mean that 40% of your variability in shyness is from your parents. Heritability only talks about populations, not individuals.
Heritability is __________. It tells us nothing about the specific genes or environmental factors that contribute to behaviour.
abstract
Genes code for:
a) Traits
b) Behaviours
c) DNA
d) Proteins
d) Proteins.
(Remember - Proteins are they key ingredient that determines a cell’s characteristics and functions. )
Which of the following is NOT true about heritability?
a) Because we know that mental health conditions like Autism are heritable, we know all of the specific genes that contribute to this disease.
b) Heritability estimates range from 0-1. For example, height has a heritability of ~.80.
c) Heritability works at the population level, so we cannot say how much of a certain behaviour you inherited from your parents.
d) The degree of heritability for a given trait depends on the population and environment we are considering.
a) Because we know that mental health conditions like Autism are heritable, we know all of the specific genes that contribute to this disease.
Describe Neurogenesis.
The process through which new neurons are formed in the brain.
Begins 3-4 weeks after conception, generally ends by weeks 18-20.
At its peak, 250,000 neurons are formed each minute.
Describe Neural Migration.
The process by which neurons migrate, or move, to their adult location in the brain.
6-24 weeks after conception.
Neurons migrate using both active and passive movement – some actively propel themselves, while others are carried along passively.
Describe Myelination.
3rd trimester-adulthood
Once in their final destination, neurons continue to grow and differentiate. They also develop their myelin sheath – myelination is the process by which the myelin sheath (fatty sheath) forms around the axons of neurons.
The myelin sheath increases the speed of neural transmission and increases information-processing abilities in the brain.
Describe Synaptogenesis.
3rd trimester-adulthood
Once grown and developed, neurons start “talking” to each other through synapses. Synaptogenesis is the process through which neurons form synapses with other neurons, resulting in trillions of connections.
Describe Synaptic Pruning.
Occurs throughout development, with bursts in early development and during adolescence.
Synaptic pruning is a normal developmental process through which certain synapses are eliminated. About 40% of the synapses that develop are eventually eliminated. Pruning occurs in different areas of the brain depending on development. Gray matter becomes less dense as the brain matures. The prefrontal cortex, which controls executive functioning and long-term planning, is the last to mature.
Why does (synaptic) pruning happen?
It is an evolutionary advantage to have a changeable brain – this allows organisms to adapt to their environment and survive in changing conditions.
What is plasticity?
Plasticity reflects the capacity of the brain to be affected by experience. Plasticity is just another way the environment interacts with an organism to influence their development.
What are the 2 types of plasticity?
1) Experience-Expectant
2) Experience-Dependant
What is Experience-expectant plasticity?
It involves normal wiring of the brain and occurs in part from typical, expected experiences. For example, hearing sounds and language is an expected part of development, and helps to develop associated brain areas. If this doesn’t happen, these brain regions do not develop in typical ways and will be taken over by other sensory areas.
Relatedly, experience-expectant plasticity is associated with the concept of sensitive periods. These are specific times when the brain requires a specific form of experience. For example, the infant brain is wired to be responsive to language. If an infant is not exposed to language early in development, it is much more difficult for language capacities to develop in the brain
What is Experience-dependant plasticity?
The process by which neural connections are created/reorganized based on an individual’s personal experience.
This type of plasticity is related to learning and memory and occurs throughout the lifespan. For example, London taxi drivers have highly developed hippocampi, the area of the brain involved in memory. This is thought to be caused by their experiences driving and memorizing the complex roadways in London.
Leo is an avid drum player. He plays the drums throughout his childhood and becomes a professional drummer as an adult. What might we expect about Leo’s brain development?
a) Leo’s brain develops in ways similar to his family due to genetics.
b) The connections in Leo’s brain that are involved in playing the drums (e.g., motor control) were strong until puberty, but then were destroyed due to pruning.
c) The connections in Leo’s brain that are involved in playing the drums (e.g., motor control) are strong, which is different than someone who did not grow up playing the drums like Leo.
d) Playing the drums has no impact on Leo’s brain development
c) The connections in Leo’s brain that are involved in playing the drums (e.g., motor control) are strong, which is different than someone who did not grow up playing the drums like Leo.
Define epigenesis.
The emergence of new structures and functions in the course of development.
What are gametes (germ cells)?
Reproductive cells—egg and sperm—that contain only half the genetic material of all the other cells in the body.
Define conception.
The union of an egg from the mother and a sperm from the father.
True or False?
The egg is the largest human cell (the only one visible to the naked eye), but sperm are among the smallest.
True.
True or False?
For decades, and across many cultural contexts, infant mortality rates have been higher for boys than for girls.
True.
During labour and delivery, males are more likely to experience fetal distress than females, even controlling for the males’ larger size and head circumference .
Male fetuses are more sensitive than females are to teratogens (harmful external agents), including opioids and alcohol, which affects their viability and ability to thrive after birth. Male infants’ heightened vulnerability is not limited to the immediate postnatal period. Males are also more likely than females to die from SIDS, and have higher rates of incidence of a wide range of developmental disabilities, including attentional disorders and autism spectrum disorders.
True or False?
There are slightly more male newborns (51.3%) across generations and around the world.
True.
This is the case, despite the fact that male fetuses are more susceptible to spontaneous abortion than females in both the 1st week and last several weeks of pregnancy (though it is worth noting that female fetuses are more susceptible in weeks 10–15).
What 4 major developmental processes underlie the transformation of a zygote into an embryo and then a fetus?
1) Mitosis - cell division that results in two identical cells.
2) Cell Migration - the movement of newly formed cells away from their point of origin. (Ie: neurons that originate deep inside the embryonic brain and then travel to the outer reaches of the developing brain.)
3) Cell Differentiation - all of the embryo’s cells can give rise to any of the more than 200 possible cell types in the human body. After several cell divisions, however, these cells start to specialize.
4) Death - apoptosis (genetically programmed cell death). Ie: he formation of fingers depends on the death of the cells in between the ridges in the hand plate. Death is preprogrammed for the cells that disappear from the hand plates.
What is the difference between an embryo and a fetus?
Embryo - term for the developing organism from the 3rd to 8th week of prenatal development.
Fetus - term for the developing organism from the 9th week to birth.
