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PSY 222 Chapter 4

Terms in this set (142)

genes
-discrete unit of heredity
-19th century monk Gregor Mendel demonstrated that inheritance occurs through these
blending process
-before Mendel, thought that inheritance was a blending process of the properties of egg and sperm
alleles
-pairs that genes come in
-aligned along chromosomes
gene
-portion of chromosome
-made of DNA (deoxyribonucleic acid)
DNA serves as....
model for synthesis of RNA
RNA
single strand chemical that can serve as a template/model for synthesis of Messenger RNA (mRNA)
Proteins determine the development of the body by:
-Forming part of the structure of the body
-Serving as enzymes, biological catalysts that regulate chemical reactions in the body
homozygous
person has identical pair of genes on 2 chromosomes
>TT(red-red) flower
heterozygous
person has unmatched pair of genes on 2 chromosomes
>Tt(red-white) flower
How many chromosomes do humans have?
23; 1 sex chromosome (X or Y) & 22 other chromosomes
46 b/c humans are diploid, chromosomes come in pairs
What are non-sex chromosomes called"
autosomes
dominant
gene that shows strong effect in either homozygous or heterozygous condition
recessive
shows its effect only in homozygous condition
intermediate
occurs in phenotype where this is incomplete dominance in heterozygous condition
Why are examples such as PTC & hair color misleading?
-implies that single gene combination completely controls a characteristic, not always true
Some genes are on expressed-----: in some cells & not others, or ----- under certain circumstances
- partly
-only
autosomal genes
all other genes except for sex-linked genes
sex-linked genes
Genes located on the sex chromosomes
- females have 2 X
-males have X & Y
During reproduction
- Females contribute an X chromosome
- Males contribute either an X or a Y chromosome that determines the sex of the child
if X chromosome contributed by male, kid will be
female
if Y contributed by male, kid will be
male
sex-linked genes
refer to X-linked genes since human Y chromosome has far fewer proteins than the X chromsome
sex-limited genes
genes that are present in both sexes but mainly have an effect on one sex
How can genes change?
-mutation
-micro duplication/ micro deletion
mutation
heritable changes in genetic information
Microduplication/microdeletion
part of a chromosome that might appear once might appear twice or not at all
schizophrenia
-might be result of micro duplications & micro deletions of brain relevant genes
Epigenetics
a field that is concerned with changes in gene expression without the modification of the DNA sequence
Some genes are active only @ a certain point in one's life, a certain time of day, etc.
true
What is central to learning & memory?
Changes in gene expression
What is most likely the explanation for differences between monozygotic "identical" twins?
epigenetic differences
What you do at any moment not only affects you now, but produces epigenetic effects that alter gene expressions for a longer period of time
true
What alters the activity of genes?
experiences
Heritability
refers to how much characteristics depend on genetic differences
Heritability of a certain trait is specific to a given population
true
What may cause genetic influences to have less of an effect
strong environmental influences
What do almost all behaviors have?
a genetic and environmental component
What do researchers study to infer contributions of heredity and environment?
monozygotic & dizygotic twins
What do researchers study to infer hereditary influences?
adopted children & their resemblance to their biological parents
What can be modified by environmental intervention?
traits with strong hereditary influence
PKU (phenylketonuria)
-a genetic inability to metabolize the amino acid phenylketonuria
-environmental interventions can modify PKU
Do genes directly produce behaviors?
No. They produce proteins that increase the probability that a behavior will develop under certain circumstances
How can genes alter your environment?
They can produce behaviors/ traits that alter how people in your environment behave to you
Articfical Selection
process of selecting plants/animals for desired traits
What are some examples of the fundamental issue of how much a role each factor plays in shaping human behaviors?
-universality of facial expressions
-psychological disorders
-weight gain
-personality
-sexual orientation
When does the human central nervous system begin to form?
when the embryo is approximately 2 weeks old
The dorsal surface thickens to form what?
a neural tube surrounding a fluid filled cavity
The forward end enlarges & differentiates into what?
the hindbrain, midbrain, & forebrain
What does the rest of the neural tube become?
the spinal cord
What is needed for the neural tube to develop properly?
folic acid
What does the fluid-filled (cerebrospinal fluid) cavity become?
the central canal of the spinal cord & the 4 ventricles of the brain
When do the first muscle movements occur?
7.5 weeks
How much does the human brain weigh @ birth?
approximately 350 grams
How much does the brain weigh by the first year?
approximately 1000 grams
How much does the adult brain weigh?
1200-1400 grams
The development of neurons in the brain involves what 5 processes?
1. proliferation
2. migration
3. differentiation
4. mylination
5. synaptogenesis
Proliferation
-refers to production of new cells/ neurons in the brain primarily occurring early in life
-early in development the cells lining the ventricles divide
-some become stem cells that continue to divide, others remain where they are or become neurons/ glia that migrate to other locations
- all neurons from within 28 weeks of gestation
What is migration?
refers to the movement of newly formed neurons & glia to their eventual locations
Where does migration occur?
-occurs in a variety of directions throughout the brain
-occurs via cells following chemical paths in brain (consisting of immunoglobins & chemokines)
- deficiency in these chemicals results in impaired migration, decreased brain size & mental retardation
What is differentiation?
refers to forming of axon & dendrite that gives neuron its distinctive shape
Which grows first, the axon or dendrites?
the axon grows first & is followed by the development of the dendrites
Neurons differ in their shape and chemical component depending on what?
their location in their location in the brain
myelination
-refers to process by which glia produce the fatty sheath that covers the axons of some neurons
-first occurs in the spinal cord & then in hindbrain, midbrain, & the forebrain
Synaptogenesis
-final stage of neural development
-refers to formation of synapses between neurons
-occurs throughout life b/c neurons are constantly forming new connections & throwing away old ones
-slows significantly late in lifetime
stem cells
-undifferentiated cells found in interior of brain that can generate "daughter cells" which can transform into glia or neurons in olfactory bulb
-new olfactory is continually replacing dying ones
New neurons later in life
-development of new neurons also occurs in other regions
>songbirds have steady replacement of new neurons in the singing area of brain
-stem cells differentiate into neurons in adult hippocampus of mammals & facilitate learning
(forming new memories)
skin cells
newest
most under a yr old
heart cells
tend to be as old as the person
mammalian cerebral cortexes from few/ no new neurons after birth
true
axons must travel great distances across brain to form correct connections
true
Sperry (1954)
-research with newts indicated that axons follow a chemical trail to reach their appropriate target
How do growing axons reach their target?
by following gradient of chemicals in which they are attracted by some chemicals & repelled by others
neurotrophin
a chemical that promotes the survival and activity of neurons
What happens to axons that are not exposed to neurotrophin after making connections?
They undergo apoptosis (preprogrammed mechanism of cell death)
Nerve Growth Factor (NGF)
a type of neurotrophin released by muscles that promotes the survival and growth of axons
The brain's system of overproducing neurons & then applying apoptosis enables what?
enables the exact matching of number of incoming axons to number of receiving cells
What do neurotrophins do to the axons and dendrites throughout life?
-neurons no longer need neurotrophin for survival
-they increase the branching on axons and dendrites
What is needed for the development of the brain?
a precise chemical environment
Are early stages of brain development critical for normal development in life?
yes
What do chemical distortions in the brain during early development cause?
they can cause significant impairment & developmental problems
fetal alcohol syndrome
- condition that children are born with if the mother drinks heavily during pregnancy
What are the symptoms of fetal alcohol syndrome?
-hyperactivity & impulsiveness
-difficulty maintaining attention
-varying degrees of cognitive disability
-motor problems & heart defects
-facial abnormalities
The dendrites of kids born with fetal alcohol syndrome are...
short w/ few branches
what does exposure to alcohol in the fetus brain do?
-It suppresses glutamate & enhances the release of Gaba
- meaning that many neurons consequently receive less excitation & exposure to neurotrophin than usual & undergo apoptosis
What effect does cocaine use during pregnancy have?
children of mothers who use cocaine during pregnancy show decrease in language skills, a slight decrease in IQ scores & impaired hearing
What effect does nicotine use during pregnancy have?
-Children of mothers who smoked nicotine during pregnancy are @ risk for low birth weight, sudden infant death syndrome, ADHD long term intellectual deficits & impairments of the immune system
The brain has some limited ability to reorganize itself in response to experience
true
Throughout the lifetime, axons & dendrites do what
throughout the lifetime, axons & dendrites continue to modify their structure & connections throughout the lifetime
What do dendrites continually grow?
-dendrites continually grow new spines
The gain & loss of spines indicates
new connections which relates to learning
What could be a possible cause for the underdevelopment of Genie's brain
Since Genie was raised in isolation, she had less branches on her neurons
What is observed in rats raised in an enriched environment?
rats raised in an enriched environment develop a thicker cortex & increased dendritic branching
What happens to the cerebral cortex in old age
the thickness of the cerebral cortex declines in old age but much less in those that are physically (and mentally?) active
What has been shown in humans as a function of physical activity
mesurable expansion of neurons has been shown in humans as a function of physical activity
Neurons also become more------ finely tuned & responsive to experiences that have been important in the past
finely tuned
Blind people often have what because neurons become more finely tuned & responsive to experiences that have been important in the past?
blind people often have enhanced tactile senses & verbal skills
The occipital lobe normally dedicated to processing visual information adapts to also process what?
tactile & verbal information
What changes the brain in a way that improves the ability of a skill?
extensive practice of a skill changes the brain in a that improves the ability for that skill
MRI studies reveal what about the temporal lobe of professional musicians?
temporal lobe of professional musicians in the right hemisphere is 30% larger than nonmusicians
What is the thicker gray matter in the part of the brain is responsible for?
hand control and vision of professional keyboard players
What does practicing a skill do to the brain?
Practicing a skill reorganizes the brain to maximize performance of the skill
What do certain types of training do if it begins early in life?
certain types of training may exert bigger effect if it begins early in life
Can adult experiences modify brain anatomy?
Yes
focal hand dystonia
-"musicians cramp"
-condition where the reorganization of the brain goes too far
What happens to the fingers of musicians who practice extensively?
-fingers of musicians who practice extensively become clumsy fatigue easily & make involuntary movements
- which is the result of extensive reorganization of sensory thalamus & cortex so that touch responses to one finger overlap those of another
What are characteristics of adolescent brains?
impulsivity
seek immediate reward rather than wait
prefrontal cortex not as mature
what are characteristics of old aged brains?
-less efficient functioning
-decline in memory
-brain able to activate other areas to compensate
plasticity
ability to strengthen neural connections @ synapses & establish new connections
What does the brain do in response to experience?
Brain is able to change & adapt in response to experience, which is the basis for the ability to form new memories & learn new things
closed head injury
-refers to trauma that occurs when a sharp blow to the head drives the brain tissue against the inside wall of the skull
What is one of the main causes of brain injury in young adults?
closed head injury
Stroke (cerebrovascular accident)
-temporary loss of blood flow to the brain
-common cause of brain damage in elderly
What are the types of strokes?
-ischemia
-hemorrhage
-aneurysm
ischemia
-most common type of stroke
-results from blood clot/ obstruction of artery
-neurons lose their oxygen & glucose supply
hemorrhage
-less frequent type of stroke resulting from a ruptured artery
-neurons flooded w/ excess blood, calcium, oxygen, & other chemicals
What can ischemia & hemorrhage cause?
edema
disruption of sodium-potassium pump leading to the accumulation of potassium ions inside neurons
edema
accumulation of fluid in brain resulting in increased pressure on brain & increasing probability of further strokes
What does Edema & excess potassium trigger?
edema & excess potassium triggers release of excitatory neurotransmitter glutamate
What does the overstimulation of neurons lead to?
the overstimulation of neurons leads to sodium & other ions entering the neuron in excessive amounts
excess positive ions in the neuron do what?
excess positive ions in neuron block metabolism in the mitochondria & kill neuron
tPA (tissue plasminogen activator)
drug that breaks up blood clots & can reduce the effects of ischemic strokes
•Research has begun to attempt to save cells in penumba region (region that surronds immediate damage) by:
-blocking glutamate synapses
-opening potassium channels
What is one of the most effective laboratory methods used to minimize damage caused by strokes?
cool the brain
Cannabinoids
-have also been shown to potentially minimize cell loss after brain stroke, closed head injury & other kinds of brain damage, decrease glutamate synapse
-benefits most likely due to cannabinoids antioxidant or anti-inflammatory actions
What does the application of omega-3 fatty acids do?
-omega-3 fatty acids are a major component of cell membranes
-may help to block apoptosis may help to block apoptosis & other neural damage
What do the surviving brain areas do following brain damage?
-following brain damage, surviving brain areas increase or reorganize their activity
diaschisis
decreased activity of surviving neurons after damage to other neurons
What is a possible mechanism of later recovery?
- use of drugs to stimulate activity in healthy regions of brain
- using stimulant
Is there any hope after brain damage?
-destoryed cell bodies can't be replaced but damaged axons may grow back under certain circumstances through therapy & focusing on what they are capable of doing
>if an axon in the peripheral nervous system is crushed, it follows its myelin sheath back to target & grows back toward the periphery @ a rate of about 1 mm per day
How much can damaged axons regenerate?
damaged axons only regenerate 1-2 millimeters in mature mammals
Paralysis caused by spinal cord damage is relatively----
permanent
What is a mechanical barrier to axon growth?
scar tissue makes a mechanical barrier to axon growth
What does myelin in the central nervous system release to inhibit axon growth?
myelin in the central nervous system releases proteins that inhibit axon growth
collateral sprouts
new branches formed by other non-damaged axons that attach to vacant receptors
What do cells that have lost their source of innervation release?
cells that have lost their source of innervation release neurotrophins
•Over several months, the sprouts fill in most vacated synapses and can be.....
useful, neutral, or harmful
What do postsynaptic cells deprived of synaptic inputs develop?
postsynaptic cells deprived of synaptic inputs develop increased sensitivity to neurotransmitter to compensate for decreased input
denervation supersensitivity
heightened sensitivity to a neurotransmitter after the destruction of an incoming axon
- due to increased number & effectiveness of receptors
disuse superse
hypersensitivity to neurotransmitter after a result of inactivity by an incoming axon
- due to increased number & effectiveness of receptors
phantom limb
-Refers to the continuation of sensation of an amputated body part.
- b/c cortex reorganizes itself after amputation of body part by becoming responsive to other parts of the body
- original axons degenerate leaving vacant synapses into which others axons sprout
In case study, what did patients feel during sex?
-patients feeling a phantom foot during sex
- b/c of brain reorganization: representation of intact organ has spread into the amputated area through axonal branching
What is are possible treatment options for phantom limbs?
-learned adjustments
-prosthetics
-virtual reality treatment
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