Chapter 4 -Quiz 2 Flashcards
4.1 Genetics and Evolution of Behavior
Is there a role for genetics in controlling facial expressions?
-Yes
-tested blind people
Mendellian Genetics
What did Mendel demonstrate?
-inheritance occurs through genes
Mendellian Genetics
Define genes
-units of heredity that maintain their structural identity from one generation to another
Mendellian Genetics
What are chromosomes?
-strands of genes
-come in pairs
Mendellian genetics
What are genes made of?
-DNA
Mendellian Genetics
What does a strand of DNA serve as a template for the synthesis of?
-RNA
-single strand
Mendellian Genetics
What does RNA’s template help to synthesize?
-protein molecules
Mendellian Genetics
What are the four bases of DNA?
-adenosine, guanine, cytosine and uracil
Mendellian Genetics
What does homozygous mean?
-you have the same gene on both chromosomes
Mendellian Genetics
What does heterozygous mean?
-you have different pairs of genes
-think blue eye vs brown eye
Mendellian Genetics
Is the gene for sensitivity to the taste of PTC dominant or recessive?
-dominant
Mendellian Genetics
Why is it misleading to say a characteristic is linked to a single gene?
-almost any characteristic depends on more than one gene and environment influences
Mendellian Genetics
What are sex-limited genes?
-on autosomal chromosomes and activated by hormones in one sex more than the other
-chest hair in men or breast size in women
Mendellian Genetics
What is a mutation?
-heritable change in DNA, where one of the bases changes to another, duplicates or deletes
Mendellian Genetics
What is epigenetics?
-changes in gene expression
Mendellian Genetics
Does every cell in your body have the same DNA as every other cell? Is there an exception? (2)
-yes
-exception is red blood cells
Mendellian Genetics
Can epigenetics be inherited?
-yes, at least for a generation or two
Mendellian Genetics
What do histones do?
-bind DNA into a ball
Mendellian Genetics
How do epigenetics cause the histones to loosen their grip on the DNA, facilitating the expression of that gene?
-by adding acetyl groups to the histone tails
-the opposite turns the gene off
Mendellian Genetics
What does adding methyl groups to a promoter do to a gene?
-adding them turns off a gene and removing them turns it on
Mendellian Genetics
How does an epigenetic change differ from a mutation?
-A mutation is a permanent change in part of a chromosome whereas an epigenetic change is an increase or decrease in the activity of a gene or group of genes.
Heredity and environment
If a characteristic has high heritability what does this mean?
-if the variation in that characteristic depends largely on genetic differences
-ranges from 0 for none to 1
Heredity and environmentq
What are the three kinds of evidence researchers rely on to determine heritability of a characteristic? (3)
- Comparison of monozygotic twins and dizygotic twins
- Another is resemblance between adopted children and their biological parents.
- A particular gene is more common than average among people who show a particular behavior.
Heredity and environment
What is the candidate gene approach and how successful has it been? (2)
-researchers test whether a gene can have significant influence on one characteristic (like alcohol abuse)
-many studies have yielded small or uncertain effects
Heredity and environment
What is genome wide association research?
-examining all the genes and comparing them between two groups
-issues with this approach too
Heredity and environment
Suppose someone determines the heritability of IQ scores for a given population. Then society changes in a way that provides the best possible opportunity for everyone within that population. Will heritability of IQ increase, decrease, or stay the same?
-Heritability will increase. Heritability estimates how much of the variation is due to differences in genes. If everyone has the same environment, then differences in environment cannot account for much of the remaining differences in IQ scores. Therefore, the relative role of genetic differences will be greater.
Heredity and environment
What does the example with phenylketonuria (PKU) show?
-this condition is hereditary but can be influenced by what the child eats, which means it is not unmodifiable
-keeping the child on a low-phenylaline diet helps
Evolution of behavior
What was Charles Darwin the founder of and what term did he not like? (2)
-founder of evolutionary theory
-did not like term evolution and preferred descent with modification
The Evolution of behavior
Define evolution
-change over generations in frequency of genes in a population
The evolution of behavior
What are the two questions we must ditinguish about evolution?
-how did some species evolve and how do species evolve
-ancestors vs. genetics passing down
The Evolution of behavior
What does evolutionary psychology focus on?
-what explanations do they focus on
-evolutionary and functional explanations
-how our genes reflect ancestors + natural selection
The evolution of behavior
What is kin selection?
-selection for gene that benefits relatives
-you risk your life for your children, who spread your genes
The evolution of behavior
What does altruism show us through a lens of evolutionary psychology? (3)
-what three reasons does it explain for altruism
Three reasons for its existence:
-kin selection
-reciprocal altruism
-group selection
The evolution of behavior
What is reciprocal altruism?
-individuals help those who will return the favour
-requires an ability to identify individuals and remember them
The evolution of human behavior
What is group selection?
-altruistic groups thrive better than less cooperative groups
-works especially well for humans because we can punish uncooperative pp
Maturation of the Vertebrate brain
What are homebox genes? What animals/bugs are they found in? (2)
-regulate the expression of other genes and control start of anatomical development
-vertebrates, insects, plants, even fungi and yeast
-all share a large sequence of DNA bases and mutations cause bad effecrs
Maturation of the vertebrate brain
When does a human central nervous system begin to form during the developmental stages?
-like what week as a fetus
-2 weeks old
Maturation of the vertebrate brain
What parts of the central nervous system begin to develop in a fetus? Describe this (5)
-Dorsal surface thickens
-Lips rise, curl, merge forming neural tube
-Tube sinks, enlarges into hindbrain, midbrain, forebrain
-Rest becomes spinal cord
-Cavity becomes central canal & brain ventricles
Maturation of the vertebrate brain
In early infancy, what area of the cortex is more mature?
-primary somatosensory areas of the cortex
-registering vision, hearing and other senses
-greatest change over first couple of years is the prefrontal cortex and other cortical areas responsible for attenion, working memory and decision making
-the infant brain is set up to see, hear and so forth but limited in its abiity to interpret that information or decide what to do with it
Maturation of the vertebrate brain: growth and development of neurons
What is proliferation?
-production of new cells
-cells are not yet identifiable as neurons or glia
Maturation of the vertebrate brain: growth and development of neurons
Early in development, what happens to the cells lining the ventricles of the brain? (2)
-some stay there and are stem cells contuing to divide
-some migrate to other parts of the nervous system
in humans, most of the migration occurs before birth, but some after
Maturation of vertebrate brain
What is one of the major differences between human brains and chimpanzee brains in regards to neurons?
-human neurons continue to proliferate longer
Maturation of the vertebrate brain: growth and development of neurons
What chemicals help cells migrate within the body in early development?
-immunoglobins and chemokines
-a deficit in these leads to impaired migration, decreased brain size
and “retardation”
Maturation of the vertebrate brain: Growth and development of neurons
What is differentiation?
-when a cell differentiates into a neuron
-it will begin to form its dendrites, axon and synapses
Maturation of the vertebrate brain: Growth and development of neurons
What is synaptogenesis?
-the formation of synapses
-this begins long before birth but continues throughout life as neurons form new synapses and discard old ones
-this process slows in older people as does the formation of dendritic branches
Maturation of the vertebrate brain: growth and development of neurons
What is myelination?
-process by which glia produce the insulating fatty sheaths
-later and slower stage
-myelins form first in the spinal cord and then in the hindbrain, midbrain and forebrain
-continues gradually for decades and increases as a result of learning new motor skills
Maturation of vertebrate brain: new neurons later in life
What exceptions were found that showed some neurons were generated after infancy? (2)
-Exceptions found: Olfactory receptors, songbirds, hippocampus, basal ganglia
-Traditional belief: No new neurons after infancy
Maturation of vertebrate brain: new neurons later in life
What was the method used to determine if new neurons were made after infancy? (2)
-use of radioactive isotope through examination of carbon in DNA of cells
-could compare the concentraion of carbon because of nuclear war
Maturation of vertebrate brain: new neurons later in life
What structures in the brain do and do not get new neurons? (3)
-Cerebral cortex: Few to no new neurons after birth
-Hippocampus: Almost 2% neurons replaced yearly
-Basal ganglia: Neurons replaced in parts like striatum
-when neurons are formed they are small interneurons not projecting neurons
-The mean C14 concentration of the DNA of human neurons in the hippocampus and basal ganglia corresponds to a level slightly more recent than the year the person was born, indicating that some of those neurons formed after birth.
Pathfinding by axons: Chemical pathfinding by axons
How did Paul Weiss’s experiment with salamanders challenge conventional wisdom about nerve connections? Discuss the experiment and how it worked, what the outcomes were and what Weiss deduced from it (4)
-Experiment: Grafted extra leg to salamander
-Axons grew into extra limb, allowing movement
-Weiss proposed nerves attached randomly, muscles responded selectively
-Weiss dismissed idea of specific axon-muscle connections, likened muscles to radios tuned to different signals.
-Contrary to mammals, salamanders accept transplants
Pathfinding by axons: specificy of axon connections
How did Roger Sperry’s experiment demonstrate specificity of axon connections? Describe the experiment, how he changed it and what he found and concluded. (5)
-Experiment: Cut optic nerves in newts
-Optic nerves grew back to tectum, restoring vision
-then rotated eye by 180 degrees, cut optic nerve again and axons regrew to original targets, despite eye rotation
-Newts saw world upside down, confirming specificity of axon growth
-Sperry’s experiment showed axons regrow to original targets, suggesting they follow specific chemical trails.
Pathfinding by axons: Chemical gradients
How does an axon find its target despite the vast number of neurons and limited genes? Give a general answer and then break it down. (2)
-growing axon follows a path of cell surface molecules and is attracted and repelled by different molecules
-then axons with a greater concentration of a chemical will attach to target cells with a greater chemical concentration of the same chemical
Pathfinding by axons: Chemical gradients
How do axons align themselves with their target cells? Give a bit of an example (2)
-like how does the chemical gradient work
-they align themselves with target cells based on concentration of chemicals
-higher concentraion of protein in axon connects to higher concentration in target cell and vice versa
Pathfinding by axons: competition among axons as a general principle
When axons intially reach their targets, chemical gradients steer them to approx the correct location, but it isn’t 100% accurate. What happens to help with this accuracy? (2)
-each axon forms synapses onto many cells in approx the right location and each target cell recieves synapses from many axons
-over time, the postsynaptic cell strengthens the most appropriate synapses and eliminates others
-suggest a general principle called neural darwinism
Pathfinding by axons: competition among axons as a general principle
Explain neural darwinism. What happens in the beginning, middle and end? (3)
-Start with more neurons/synapses than needed
-Selection process retains some synapses, rejects others
-Successful combinations survive, others fail
-Caution with analogy to Darwinian evolution: Mutations are random, while neurotrophins guide axonal branches and synapses
Pathfinding by axons: Stop and Check Q Pg 122
If axons from the retina were prevented from showing spontaneous activity during early development, what would be the probable effect on development of the thalamus?
-The axons would attach based on a chemical gradient but could not fine-tune their adjustment based on experience. Therefore, the connections would be less precise.
Determinants of Neuronal Survival
What did the research by Rita Levi-Montalcini reveal about axon development? (4)
-Muscle role: Promote survival, not formation, of axons
-Discovery: Muscles deliver nerve growth factor (NGF) to axons
-NGF supports survival and growth of axons
-Axons without NGF degenerate, leading to apoptosis of their cell bodies
-Muscles deliver NGF to axons, supporting their survival and growth. Axons without NGF undergo apoptosis if they fail to connect with postsynaptic cells.
-That is, each neuron starts life with a “suicide program”: If its axon does not make contact with an appropriate postsynaptic cell by a certain age, the neuron kills itself through a process called apoptosis1, a programmed mechanism of cell death.
Determinants of neuronal survival
Define neurotrophin
-chemical that promotes the survival and activity of neurons
-In addition to NGF, the nervous system responds to brain-derived neurotrophic factor (BDNF) and several other neurotrophins
-Neurotrophins are essential for growth of axons and dendrites, formation of new synapses, and learning
Determinant of neuronal survival: stop and check Q Pg 123
What process assures that the spinal cord has the right number of axons to innervate all the muscle cells?
-The nervous system builds more neurons than it needs and discards through apoptosis those that do not make lasting synapses
Determinant of neuronal survival: stop and check Q Pg 123
At what age does a person have the greatest number of neurons—early in life, during adolescence, or during adulthood?
-greatest early in life.
The Vulnerable Developing Brain
What are the symptoms of fetal alcohol syndrome? (2)
-ADHD like symptoms
-mental disabilities, motor problems, hearts defects and facial abnormalities
-drinking during pregnancy leads to thinning of the cerebral cortex
The Vulnerable Developing brain Stop and Check Pg 123
Anesthetic drugs and anxiety-reducing drugs increase activity of GABA, decreasing brain excitation. Why would we predict that exposure to these drugs might be dangerous to the brain of a fetus?
-Prolonged exposure to anesthetics or anxiety-reducing drugs might increase apoptosis of developing neurons.
- Increased GABA activity decreases excitation, and developing neurons undergo apoptosis if they do not receive enough excitation.
Differentiation of the Cortex
What surprising result occurred when researchers rewired the auditory thalamus and cortex in ferrets?
-The rewired temporal cortex, receiving input from the optic nerve, produced visual responses.
-this helps answer when and how a neuron decides what neuron it will differentiate into.
-the sensory input instructs the cortex about how to develop
Fine-tuning by experience: Experience and dendritic branching
What is far transfer?
-the idea that you can teach something challenging and hope it helps someone get better at other, unrelated tasks too
-in general, this is not shown in humans, only near transfer
Module 4.2: End of module Quiz
Which parts of the cerebral cortex are most likely to detoriate in Alzheimers disease and other conditions?
-the areas that mature at the latest age, such as the prefrontal cortex
Module 4.2: End of Module quiz
If a pregnant woman drinks alcohol, alcohol harms the brain of the fetus not only while it is in the system, but also while it is washing away after drinking. What is the danger while alcohol is washing away?
-overstimulation at glutamate synapses can poision the mitochondria
Unit 4.3: Brain damage and short-term recovery
What is the most common head injury in young people?
-closed head injury
-sharp blow to the head that doesn’t puncture brain
Brain-damage and short term recovery: reducing the harm from a stroke
What is a stoke
-AKA as a cerebrovascular accident
-interruption of normal blood flow to a brain area
-more common in older people
-can be ischemia (blood clot) or hemorrhage (ruptured artery)
Brain-damage and short-term recovery: reducing the harm from a stoke
What problems do both ischemic and hemorrhage strokes lead to? (2)
-accumulation of fluid which creates pressure (edema)
-impair sodium-potassium pump
-combination of edema and excess sodium provokes excess release of the transmitter glutamate which overstimulates neurons, damaging both neurons and synapses
Brain-damage and short term recovery: immediate treatments
What drug helps with ischemic strokes but makes hemorraging ones worse?
-tissue plasminogen activator or tPA
-breaks up blood clots
Later mechanisms of recovery: increased brain stimulation
What is diaschisis?
-decreased activity of surviving neurons after damage to other neurons
-if diachisis contributes to behavioural deficits following brain damage, then increased stimulation should help
Later mechanisms of recovery: increased brain stimulation stop and check
After someone has had a stroke, would it be best (if possible) to direct stimulant drugs to the cells that were damaged or somewhere else?
-It is best to direct a stimulant drug to the cells that had been receiving input from the damaged cells.
-Presumably, the loss of input has produced diaschisis.
Later mechanisms of recovery: axon sprouting
After a cell loses input from an axon, what does it secrete and what does it form from those secretions? (2)
-secretes neurotrophins
-induce other axons to form new branches or collateral sprouts
-collateral sprouting in the cortex contributes to behavioral recovery in some cases
-however, the result depends on whether the sprouting axons convery information similar to those they replace
Later mechanisms of recovery: denervation supersensitivity
What is denervation supersensitivity?
-AKA receptor supersensitivity
-increased sensitivity of neurons following the damage or cells nearby
-helps compensate for decreased input
-however, it can strengthen both desirable connections and undesirable connections (like those responsible for pain)
Later mechanisms of recovery: stop and check Pg 139
Is collatera sprouting a change in axons or dendritic receptors?
-Axons
Later mechanisms of recovery: Stop and Check Pg 139
Is denervation supersensitivity a change in axons or dendritic receptors?
-dendritic receptors
Later mechanisms of recovery: reorganized sensory rep and phantom limb
What causes phantom limb sensations, according to modern understanding?
-occur when the somatosensory cortex reorganizes and becomes responsive to alternative inputs, such as inputs from neighboring body parts.
-touch on the face now produces a facial sensation and a sensation in the phantom hand
-amputees who learn to use an artifical arm report that the phantom sensations gradually disappear
Later mechanisms of recovery: learned adjusments of behavior
What is a deafferented limb?
-when the motor nerves still connect to the muscle but the animal can’t feel it
-however, if both limbs are deafferented the monkey will still use it
