Chapter 4 Flashcards
What are the differences between genetic and epigenetic influences on development?
While epigenetics deals with changes in gene expression over the course of a lifespan (development), genetic influences are hereditary and only provide the genes given by the mother and father
What are the types of evidence researchers use to infer heritability?
- Twin studies - comparison of monozygotic and dizygotic twins
- Adoption studies - examining children who were adopted and comparing their characteristics with their adopted and biological parents
- Heritability estimates - it shows how much something depends on variations in heredity within a population, and it varies from one population to another.
Why does heritability vary from one population to another?
This is because even a trait with high heritability can be modified by the environment and interventions.
Why does high heritability not mean that the environment cannot change something?
This is because genes are still modifiable even if they have high heritability
What are the ways in which genetic variations can influence behavior?
Due to genetics, you may
express a trait which the environment reinforces, leading you to maintain the behaviour for that trait which is reinforced. Such as a naturally tall kid being encouraged into basketball and being fixated on basketball since that is what their environment reinforces.t
What are the examples of evolutionary explanations in psychology?
- Evolutionary explanations - how our genes and behaviour reflect those of our ancestors
- Functional explanations - why natural selection might have favoured genes that promote certain behaviours
What are the problems in explaining a possible evolutionary basis for altruistic behavior?
Atruistic behaviour inherently prevents the spread of ones genes as it puts one at a disadvantage. However, it is likely promoted in the human species due to kin selection, reciprocal altruism and group selection
Describe the early development of the brain.
At 2 weeks old, the dorsal surface thickens and long thin lips rise, curl, and merge, forming a neural tube that surrounds a fluid-filled cavity. The forward end then enlarges and differentiates to the hind, mid and forebrain, with the other end as the spinal chord and 4 ventricles with CSF.
How do new neurons form in a mature brain?
- Proliferation - the production of new cells
- Migration - primitive cells then start to move to corresponding areas in the brain, guided by immunoglobulins and chemokines
- Differentiation - the cell becomes a neuron, forming dendrites, axons and synapses
- Synaptogensis - the formation of synapses which continues throughout life.
- Myelination - the process by which glia produce the insulating fatty sheaths that accelerate transmission in many vertebrate axons, which also continues throughout life
How do axons seek specific targets?
A growing axon follows a path of cell surface molecules, attracted by certain chemicals and repelled by others, in a process that steers the axon in the correct direction. While their chemical gradients should steer them to the right location, if that location is damaged, they will pick the next best option.
What is apoptosis?
A programmed mechanism of cell death where if the axon of the neuron does not connect to an appropriate postsynaptic cell by a certain age, the neuron kills itself. It’s known if the NGF (nerve growth factor) protein is not received, where any of its neurons forms a synapse onto a muscle
How do neurotrophins prevent apoptosis?
NGF prevents apoptosis as it tells the incoming axon that it should not die as it will help it. They are neurotrophins, a chemical that promotes the survival and activity of neurons.
What are some examples of how experiences alter brain anatomy and function?
Sensory input can, to some extent, instruct the cortex on how to develop. Although the central structure of a dendrite becomes stable by adolescence, the peripheral branches of a dendrite remain flexible throughout life. However, experience can only apply to near effect, far effect like thinking solving crossword puzzles would improve intellect isnt present. Special cases also show that the brain adapts to be more specific to minimise the negative effects of sensory loss, and that with training, the brain areas corresponding to the training will improve.
Evaluate explanations of risky behaviour in adolescents.
- Areas of the prefrontal cortex - these areas are responsible for inhibiting behaviours but they are not fully mature in adolescents. However, in lab tests, they can inhibit impulses just as well as adults and it should also be present in younger ages.
- The brain’s reward system - teenager’s reward system develops faster with age but rewards also come with risks.
What are the possible treatments after brain damage?
- Tissue plasminogen activator (tPA) - breaks up blood clots and decreases the negative effects of ischemia although makes hemorrhages worse.
- Procedures that block glutamate synapses, block calcium entry or protect neurons - they limit the amount of neural death by mitigating overstimulation (caused by strokes)
- Exposure to cannabinoids - they decrease the release of glutamate, exert anti-inflammatory effects, protect the blood-brain barrier, reduce edema and lower body temperatures.
How does remodeling in the cerebral cortex produce the phantom limb experience?
When a limb or other body part is lost, the loss of sensory input from that limb leaves vacant synaptic sites at several levels of the CNS. However, this does not mean that the initial properties were lost, these brain parts could still be responsible for a limb thats gone - leading to the phantom limb experience. Therefore, if the previous neurons responsible for the amputated limb were reconfigured to the face, if you touched the face you would get a phantom limb experience.
What are sex-limited genes?
They are genes that are present in both males and females but are only expressed in one group
How can epigenetic effects occur?
To activate a gene, the DNA must partially unwind from the histones. Adding an acetyl group to a histone tail loosens the histone’s grip on the DNA, facilitating the expression of the genes. Removing an acetyl group tightens the histone’s grip on the DNA and silences the gene. Another epigenetic change is to add a methyl group at the beginning of a gene, turning it off, or removing a methyl group to turn it on
What are the ways to see how important genes are for an outcome?
- Candidate Gene approach - researchers test a hypothesis by identifying a specific gene
- Genome wide association studies - it examines the entire set of chromosomes while comparing two groups, such as people with and without depression.
What is kin selection?
The selection for a gene that benefits the individual’s relatives.
What is reciprocal altruism?
The idea that individuals help those who will probably return the favor.
What is group selection?
According to this idea, altruistic groups thrive better than less cooperative ones
What areas in the brain still go through neurogenesis?
- Olfactory receptors - The nose contains stem cells that remain immature throughout life. Periodically, they divide, with one cell remaining immature while the other differentiates to replace a dying olfactory receptor.
- Hippocampus - New small interneurons form throughout life in the hippocampus (memory formation)
What is neural Darwinism?
The idea that we start with more neurons and synapses that we can keep, and then a selection process keeps the most successful combinations of synapses and rejects others.
What is an example of a negative case of reorganisation?
Focal hand dystonia - when a musician plays for such a long time that the brain regions corresponding to each finger enlarge and overlap, leading to the person unable to move fingers independently.
What are the different types of brain damage?
- Closed head injury - a sharp blow to the head that does not puncture the brain
- Stroke - a temporary interruption of normal blood flow to a brain area
> Ischemia: the result of a blood clot or other obstruction in an artery
> Hemorrhage: the result of a ruptured artery
What does one recover from a brain injury?
- Disachisis, the decreased activity of surviving neurons because of damage to connecting neurons, is mitigated with amphetamine which increases stimulation to keep these neurons active
- Regrowing axons is possible by using glial cells from a person’s olfactory bulb. These cells can be transplanted for slight axon regrowth.
- When a cell loses input from an axon, it secretes neurotrophins that induce other axons to form collateral sprouts to take over the vacant synapses. It can replace the previous function only if they convey the same information. Otherwise, its useless.
- Denervation supersensitivity can compensate for decreased input by increasing how easily aroused neighbouring neurons of the dead neuron are. However, it can strengthen the useless neurons.
