the biological basis for behavior the human brain

The Biological Basis for Behavior

The Human Brain

Bellringer 3

• List at least five things your brain does on a daily basis.

I. Brain Basics

• A. Studying the brain– 1. This area of the science of psychology is

experiencing an explosion of research– 2. This is mostly due to changes in technology that

allow us to see the brain as it works.

• B. Phrenology– 1. A concept developed by a German Physician

named Franz Gall.– 2. The theory stated that bumps on the skull

revealed our mental abilities and personality traits.

Phrenology

• C. Basic Terminology– 1. Biological psychologist = a branch of

psychology concerned with the links between biology and behavior.

– 2. Sometimes referred to as neuropsychology, neuroscience, physiological psychology, or biopsychology.

– 3. Neuroanatomy refers to the study of the parts and functions of neurons

II. Neural anatomy and Neural Communication

• A. Neurons the basic building blocks of the brain– electrically transmit

data in your brain

– makeup 1/2 the volume of the brain

Neurons

• B. Glial Cells support the neurons– 1. may be 10 times as numerous as neurons– 2. make up the other half of the volume of the

brain

• C. Neurons– 1. Three types of

Neurons• a. Sensory = neurons

that carry incoming information from the sense receptors to the CNS also known as AFFERENT NEURONS.

Sensory Neuron

• b. Motor = the neurons that carry outgoing messages from the CNS to the muscles and glands. Also known as EFFERENT NEURONS.

• c. Interneurons = CNS neurons that internally communicate and intervene between the sensory inputs and motor outputs

SpinalCord

BrainSensoryNeuron

MotorNeuron

Diagram of a Neuron

– 2. The structure of the Neuron• a. Dendrites = the bushy, branching extensions of a

neuron that receive messages and conduct impulses forward toward the cell body. Get its name from the Greek word for tree.

• b. Axon = the extension of a neuron, ending in branching terminal fibers, through which messages are sent to other neurons or to muscles or glands

• c. The Soma = the Cell body – its function is to support the cell. At the center is the nucleus

• d. The myelin sheath is a layer of fatty segmented tissue that encases the fibers of many neurons

– Enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next

– The Nodes of Ranvier = the nodes along the myelin sheath

• e. The Synapse = the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron – also called the synaptic gap or cleft

The Synapse

• f. The axon terminal = or pre-synaptic terminal is the bulb at the end of an axon through which neurotransmitters are released. (AKA terminal buttons, end buttons, and synaptic knobs)

• g. Vesicles = bubble like structures which contain the neurotransmitters

• h. Neurotransmitters = chemical messengers that transverse the synaptic gaps between neurons. They create or inhibit the receiving neuron form generating a neural impulse

• i. Synaptic receptor sites – AKA binding sites – each site is like a lock keyed to the particular chemical structure of each different type of neurotransmitter

Neurotransmitters at work

– 3. The Neuron at Rest• a. Resting potential = the interior cellular fluid of

the axon has a slightly higher negative charge. This positive outside/negative inside polarization is called resting potential

• b. The cell membrane is selectively permeable that is it allows only certain ions in or out

• c. Sodium & Potassium pump = the resting cell continually pumps three sodium ions out while letting two potassium ions in – Since both of these ions have a positive charge the result is a slight decrease in the positive charge of the inside of the cell

Ion concentrations

Cell Membrane in resting state

K+

Na+ Cl-K+A-

Outside of Cell

Inside of Cell

Na+ Cl-

The Cell Membrane is Semi-Permeable

Cell Membrane at rest

Na+ Cl-K+

Na+

Cl-K+ A-

Outside of Cell

Inside of Cell

Potassium (K+) can pass through to equalize its concentration

Sodium and Chlorine cannot pass through

Result - inside is negative relative to outside

- 70 mv

– 4. The Action Potential• a. Action potential = a neural impulse

– i. A brief electrical charge that travels down an axon

– ii. The action potential is generated by the movement of positively charged sodium ions into the axon

• b. Thresholds = the level of stimulation required to trigger a neural impulse

• c. The all-or-none law states the size, amplitude and velocity of an action potential are independent of the intensity of the stimulus that initiated it

Resting Potential

• At rest the inside of the cell is at -70 microvolts

• With inputs to dendrites inside becomes more positive

• if resting potential rises above threshold an action potential starts to travel from cell body down the axon

• Figure shows resting axon being approached by an AP

Depolarization ahead of AP

• AP opens cell membrane to allow sodium (NA+) in• inside of cell rapidly becomes more positive than

outside• this depolarization travels down the axon as leading

edge of the AP

Repolarization follows

• After depolarization potassium (K+) moves out restoring the inside to a negative voltage

• This is called repolarization• The rapid depolarization and repolarization produce

a pattern called a spike discharge

• d. The refractory period is the time during which a neuron resists further action potentials while it recharges

Bell Ringer 4

• How is a neuron firing like a toilet flushing? Be sure to include the following vocabulary in your explanation (underline each term).– Resting Potential

– Threshold

– Action Potential

– All or none

– Depolarization

– Refractory Period

III. Neurotransmitters

• A. Serotonin– 1. Affects mood, hunger, sleep and arousal – 2. Implicated in states of consciousness– 3. Prozac and similar antidepressant drugs

raise serotonin levels– 4. LSD seems to act on this system

Serotonin

• B. Dopamine– 1. Influences movement, learning, attention

and emotion– 2. Excess activity at dopamine receptor sites is

associated with schizophrenia – 3. Too little activity is associated with

Parkinson’s

• C. Norepinephrine– 1. Helps control alertness and arousal– 2. Too little can lead to depression– 3. Too much can lead to manic episodes

Dopamine & Drugs

Norepinephrine

• D. Acetycholine– 1. Works on neurons involved in muscle

action, learning and memory– 2. The poison curare works by blocking ACh – 3. Patients with Alzheimer’s show a

deterioration in this chemical messenger

• E. GABA = gamma aminobutyric acid– 1. Serves inhibitory functions and is sometimes

implicated in eating and sleeping disorders – 2. Also implicated in anxiety– 3. Works with valium by increasing GABA

which decreases anxiety.

• F. Glutamate– 1. Is the main excitatory neurotransmitter in

the brain– 2. Some people have an adverse reaction to

MSG (Monosodium Glutamate) in Chinese food, it tends to wind them up and make them feel anxious

• F. Endorphins• a. Natural pain killers in the brain

• b. Morphine is a synthetic endorphin

• c. Substance P is a neuro-cheimical that is still not fully understood but researchers suspect that it is involved in triggering the pain response

ENDORPHINS

• G. How drugs and other chemicals Alter neurotransmission– 1. Agonist work by mimicking a particular

neurotransmitter or by blocking its reuptake (or absorption back into the body)

– 2. Antagonist work by blocking the release of particular neurotransmitters.

• A. The Central Nervous System – 1. Also known as the CNS – 2. It consist of the brain and the spinal cord– 3. Cerebrospinal Fluid (CFS) is a a liquid similar to

blood serum found in the ventricles of the brain and in the central canal of the spinal cord

– 4. The Blood-Brain Barrier is the mechanism that keeps many chemicals from crossing from the blood stream into the brain. This keeps most viruses out of our brain. Certain chemicals like drugs are disolved in fats and can cross the barrier.

The Nervous System

• B. The Peripheral Nervous System PNS – 1. The sensory and motor neurons that connect

the CNS to the rest of the body – 2. It sends sensory input to the brain and relays

commands from the brain to muscles

– 3. Nerves = neural cables containing many axons which connect the CNS with muscles, glands, and sense organs

– 4. The PNS consists of • a. The Somatic System = the division of the PNS

that controls the body’s skeletal muscles; AKA the skeletal nervous system

• b. Autonomic System = the part of the PNS that controls the glands and the muscles of the internal organs such as the heart.

– Sympathetic Nervous System = the division of the ANS that arouses the body, mobilizing its energy in stressful situations

– Parasympathetic Nervous System = the division of the ANS that calms the body, conserving its energy

The Nervous System

The Autonomic Nervous System

• Sympathetic Nervous System– Dilates pupils

– Accelerates heartbeat

– Inhibits digestion

– Stimulates release of adrenaline, epinephrine and norepinephrine

– Releases the bladder

• Parasympathetic Nervous System– Contracts pupils

– Slows heartbeat

– Stimulates digestion

– Contracts bladder

• C. Reflexes and Neural Networks– 1. Reflex is a simple, automatic, inborn

response to a sensory stimulus, such as the knee-jerk response

– 2. A simple reflex pathway also known as a reflex arc is composed of a single sensory neuron and single motor neuron and sometimes an interneuron

– 3. An example of a simple reflex• a. If you put your hand over a flame you will pull it

back before you actually feel the pain• b. Sensory neurons in your hand send info up your

arm to interneurons located in your spine

• c. From the interneurons to motor neurons causing your hand to pull back

• d. Finally the message will also travel up your spine to your brain where the feeling of pain will register

– 4. Neural Networks• a. Interconnected neural cells

• b. With experience, networks can learn, as feedback strengthens or inhibits connections that produce certain results.

• c. Computer simulations of neural networks show analogous learning

Bell-ringer 4

– Write down these sentences then write down which nervous system would be in charge of each of these functions

• sending visual information to the brain

• Throwing a baseball

• your personality

• an increase in your heart rate during an emergency

• Thinking about your boyfriend or girlfriend

• Bringing the body back to its normal state.

IV. The Endocrine System

• A. The body’s slow chemical communication system; made up of a set of glands that secrete hormones into the bloodstream– 1. Transmit hormones through the blood

system as compared to the neural system– 2. Slow, minutes or hours compared with

fractions of seconds– 3. Long lasting, versus short lived

• B. Hormones = chemical messengers mostly those manufactured by the endocrine glands, that are produced in one tissue and affect another.

• C. The Glands– 1. The adrenal glands

• a. A pair of endocrine glands just above the kidneys

• b. The adrenals secrete the hormones epinephrine and norepinephrine (also known as adrenaline and noradrenaline)

• c. Helps to arouse the body in times of stress

– 2. The Pituitary Gland• a. The endocrine system's most influential gland.

• b. Once considered the master gland

• c. located at the base of the brain near the hypothalamus

• d. Under the influence of the hypothalamus the pituitary regulates growth and controls other endocrine glands

• 3. Thyroid Gland– a. H shaped gland

located in the neck

– b. Affects metabolism

• 4. Parathyroids – help regulate calcium in the blood stream which is important for neurotransmission

• 5. Pancreas – regulates the level of sugar in the blood

– 6. Types of hormones• a. Progesterone – a hormone that prepares the

uterus for the implantation of an egg.

• b. Estrogen – a hormone that is more prevalent in females

• c. Testosterone – a hormone that is more prevalent in males

• d. Insulin – a pancreatic hormone that facilitates the entry of glucose into the cells

• e. Melatonin – a hormone that is closely tied to sleep.

• f. Cortisol – a hormone that is released by the adrenal glands which is associated with elevating blood sugar and with stress.

• g. Epinephrine is also known as adrenaline it is also used as a neurotransmitter

• h. Norepinephrine is a hormone that is also a neurotransmitter

Bell-ringer

• Take out your diagram of the neuron and study for a quiz

V. The Brain

• A. Tools of Discovery– 1. Lesions and Accidents=

• a. Tissue destruction. A brain lesion is a naturally or experimentally caused destruction of brain tissue

• b. Used to determine the impact on the brain functioning

• 2. EEG– a. Electroencephalogram

– b. An amplified recording of the waves of electrical activity that sweep across the brain’s surface. These waves are measured by electrodes placed on the scalp

• 3. CT/CAT SCAN– a. Computed Tomography– b. A series of x-ray photos

taken from different angles and combined by a computer into a composite representation of a slice through the brain or body

• 4. SPECT Scan– a. Single Positron

Emission Computed Tomography

– b. Inject a radioactive isotope into the blood and examine how the blood is moved in the brain.

• 5. PET SCAN– a. Positron Emission Tomography

– b. A visual display of brain activity that detects where a radioactive form of glucose goes while the brain performs a given task

• 6. MRI– a. Magnetic Resonance Imaging

– b. A technique that uses magnetic fields and radio waves to produce computer-generated images that distinguish between different types of soft tissue

– c. Allows us to see structures within the brain

CBS special on MRI lie detection

– 7. FMRI• a. Functional MRI

• b. Similar to the MRI but pictures are taken less than a second apart

• c. The pictures reveal how much oxygen is being used in each area of the brain while functioning

• d. These pictures reveal when things happen, how the brain changes with experience and how different areas of the brain work together

– 8. Recent findings using scanning technology• a. PET scans show that the brain areas that light up

when people silently say the name of a animal differs from when they say the name of a tool

• b. MRI scans of bilingual people’s brain reveal that second languages are represented in the same area as the first if learned early and in different areas if learned later.

• c. FMRI scans reveal that during a rhyming task men’s brains have a distinctively active left brain area while women’s brains are active on both sides

• B. The basic organization– 1. Reptilian - aka R-complex Brain

• a. Medulla, pons and cerebellum

• b. Homeostasis and instinctive behaviors

– 2. early mammalian• a. Limbic system - hippocampus and the amygdala,

the hypothalamus and the thalamus

• b. Affective and emotional behavior

– 3. late mammalian• a. Cerebral cortext

• b. Judgement planning etc…

• C. The Central Core– 1. The brain stem

• a. brainstem = the oldest part and central core of the brain• b. Begins where the spinal cord swells as it enters the skull• c. The brainstem is responsible for automatic survival functions • d. The hindbrain is the most posterior part of the brain it includes the

medulla, Pons and cerebellum

– 2. Medulla oblongata• a. Medulla = the base of the brainstem;

• b. Controls heartbeat and breathing

• c. It lies directly on top of the spinal cord

– 3. Pons– lies directly above the Medulla

– acts as a bridge between the Medulla and the rest of the brain, as well as between the cerebral cortex and the cerebellum

– 4. Reticular formation• a. Reticular formation = a nerve network in the

brainstem that plays an important role in controlling arousal

• b. Moruzzi and Magoun discovered that electrically stimulating the reticular formation of a sleeping cat almost instantly produces an awake and alert animal. They also severed the reticular formation and the cat went into a coma

– 5. The Midbrain – located between the hindbrain and forebrain, it controls and coordinates some basic sensory and muscle movements.

– 6. The Thalamus• a. The thalamus = the brain’s sensory switchboard

• b. Located on top of the brainstem; located in both hemispheres resembling twin avocados

• c. It directs messages to the sensory receiving areas of the cortex and transmits replies to the cerebellum and medulla

– 7. Cerebellum • a. The “little brain” attached to the rear of the brain

stem, to the side of the pons and medulla

• b. It helps to coordinate voluntary movement and balance

• D. The Limbic System– 1. Sometimes referred to

as the forebrain – 2. The limbic system =

• a. a doughnut shaped system of neural structures at the border of the brainstem and the cerebra hemispheres

• b. Associated with emotions such as fear and aggression and drives such as those for food and sex

• c. Includes the hippocampus, the amygdala, and the hypothalamus

– 2. The amygdala• a. Two almond shaped neural clusters that are

components of the limbic system and are linked to emotion

• b. Research on aggression– Lesions on the amygdala of an ill-tempered monkey

turned him docile (Bucy 1939)

– Stimulate one section of a cat’s amygdala and it prepares to attack, stimulate another area and put it in a cage with a mouse and it cowers in terror

– Has been tried on human patients with mixed and sometimes devastating results

– 3. The Hippocampus = • a. From the Latin word meaning seahorse

• b. Lies between the thalamus and the cerebral cortex

• . Is linked with forming new memories

– 4. The Hypothalamus• a. A neural structure lying below (hypo) the

thalamus.

• b. It directs several maintenance activities (eating, drinking and body temp), it helps govern the endocrine system via the pituitary gland and it is linked to emotion

• c. Olds and Milner– While trying to implant electrodes in the

reticular formation of white rats they mistakenly implanted the electrode in a region of the hypothalamus

– The rat kept returning to the place in his cage where he received the electrical stimulation

– They had discovered a reward center in the hypothalamus

– The rats would do anything to get this stimulation, including crossing an electrified floor. They would push the button to get the stimulation up to 700 times per hour

– Similar reward centers have been found in many other animals such as goldfish, dolphins and monkeys

– When an electrode was planted in violent patients they reported mild pleasure but were not driven to frenzy like the rats

– Reward deficiency syndrome is genetic disposed deficiency in the natural brain systems for pleasure and may lead to such disorders as alcohol and drug abuse

Olds and Milner Study

• E. The Cerebral Cortex– 1. Physical description

• a. Convolutions increase the surface area of the brain

• b. Gyri = rolls that form the folding out portion

• c. Sulci = valleys

• d. Fissures are deeper than valleys

The Cerebral Cortex

– 2. The four lobes• a. Frontal lobes

– The portion of the cerebral cortex lying just behind the forehead;

– Involved in speaking and muscle movements and in making plans and judgments

– prefrontal cortex receives sensory information from all senses

• b. Occipital lobes– The portion of the cerebral cortex lying at the back of the

head;

– Includes the visual areas, (V1 & V2) which receive visual information from the opposite visual field

– cortical blindness is a specific type of blindness due to brain damage

• c. Parietal lobes– The portion of the cerebral cortex lying at the top of the

head and toward the rear;

– Includes the sensory cortex

– specializes in processing body information such as touch and body location

• d. Temporal lobes– The portion of the cerebral cortex lying roughly above the

ears;

– Includes the auditory areas, each of which receives auditory information primarily from the opposite ear.

– One of the key areas of speech known as Wernicke’s Area is located in this lobe

– 3. Motor Functions• a. The motor cortex = an area at the rear of the

frontal lobes that controls voluntary movement

• b. Foerster and Penfield mapped the motor cortexes of wide awake patients by electrically stimulating portions of the motor cortex and noting the body responses

• Delgado illustrated this by making a monkey smile and forcing a patient to make a fist

– 4. Sensory Functions• a. The sensory cortex = the area at the front of the

parietal lobes that registers and processes body sensations

• b. The more sensitive the body region the greater the area dedicated to this body part.

• c. Examples include; if you lose a finger the area dedicated for that finger will reorganize itself to pick up sensations from neighboring fingers

Motor and Sensory Areas

– 5. Association Functions• a. Association areas = areas of the cerebral cortex that

are not involved in primary motor or sensory functions

• b. Rather they are involved in higher mental functions such as learning remembering, thinking and speaking

• c. Examples of association area damage– Wilder Penfield’s sister had damage to her frontal lobe, and

although she had perfect knowledge of cake recipes could not bake a cake.

– Phineas Gage was a railroad worker who suffered sever brain damage. As a result his limbic system (emotional center) was seperated from his frontal lobe (planning center) He was now irritable and quick to be angry

– 6. Language• a. Aphasia = impairment of language usually

caused by left hemisphere damage either to Broca’s area (impairing speaking) or to Wernicke’s area (impairing understanding).

• b. Broca’s area = an area of the frontal lobe usually in the left hemisphere

– It directs the muscle movements involved in speech

– Discovered when Paul Broca treated his famous patient “Tan”

• c. Wernicke’s Area = a brain area involved in language comprehension and expression; usually found in the left temporal lobe

• e. Geschwind’s description of how we read aloud– The visual cortex in the

occipital lobe receives written words as visual stimulation

– The angular gyrus transforms the visual representations into an auditory code

– Wernicke’s area interprets the auditory code

– Broca’s Area controls the muscled for speech via the motor cortex

– The motor cortex signals the appropriate muscles to make speech

GHOTI

– 7. Brain Reorganization• a. Plasticity = the brain’s capacity for modification

as evident in brain reorganization following damage (specifically in children) and in experiments on the effects of experience on brain development

• b. Examples include a man who had ½ of his brain removed and yet made it through college and grad school.

VII. Our Divided Brains

• A. Splitting the Brain– 1. Sperry and Myers used classical conditioning to

train a cat while one eye was closed. When tested with the opposite eye open the cat was unable to produce the newly learned behavior. The study showed that the cat must be conditioned for both eyes.

– 2. Vogel and Bogen were two neurosurgeons who proposed splitting the brain of one of their severely epileptic patients, a 48 year old war veteran referred to as W.J.

Split Brain Experiment

– 3. Upon awakening the patients seemed to be fine able to think and function normally.

– 4. Roger Sperry invented an apparatus to study the split brain patients. This apparatus involved flashing different words to each visual field while also allowing for the patient to blindly feel objects with both hands.

– 5. The subject is asked to fixate on the center of the screen while words are flashed very briefly onto the screen. The subjects were then asked to identify vocally and with their hands what they saw.

– 6. When intact brain patients participate they have no trouble identifying the word “key ring”

– 7. Split brain patients on the other hand report only the word “ring” which was presented in their right field of vision which is processed by the left brain which is also the verbal side of the brain.

– 8. If asked to identify the object with their left hand (controlled by the right brain) they will search for the key that they would adamantly deny seeing.

– 9. One way they can compensate is by saying the word out loud so both sides become aware of it or by pointing to communicate between the right and left hemispheres

– 10. The results may have been over-generalized to the fields of education and literature.

• B. Studying Hemispheric Difference in the Intact Brain– 1. Perceptual task are centered in the right

hemisphere• a. For example most people recognize a picture

more quickly when it is projected to the right brain

• b. Although the left brain is better at recognizing words the right brain is better at identifying abstract relationships between words

• c. Faces are recognized in the right brain

– 2. Language tasks are generally centered in the left hemisphere

• a. For example most people recognize words more quickly when flashed to the left hemisphere

• C. Brain Organization and Handedness– 1. Handedness and language

• a. About 95% of right handers process language in their left brain

• b. Left-handers are more diverse– More than half process language in their left hemisphere

– About 25% process language in their right hemisphere

– And the other 25% process language in both hemispheres

– 2. Is handedness inherited• a. Right handedness goes back to prehistoric times

• b. Ultrasound shows that 9 out of 10 babies in the womb show a preference for sucking the right thumb

• c. Handedness is one of the few characteristics identical twins often do not share

– 3. The Case of the Disappearing Southpaws• a. Studies show that left handers die earlier than

right handers

• b. May be due to prenatal stresses and premature births

• D. Hemispheric specialization– 1. Left Brain specialization (analytic)

• a. Language– Wernicke’s Area = left temporal lobe = normal speech

without structure– Broca’s Area = Left frontal lobe = expressive area =

trouble putting speech into words

• b. Mathematical

– 2. Right Hemisphere specialization (creative)• a. Spatial functions

– Pattern recognition such as faces– Color discrimination (fine differences)

• b. Musical– Variation in intonation – Memory of musical patterns in right side

VIII. Genetics and Environment

• A. Our Biological Blueprint– 1. Chromosomes = Thread like structures made

of DNA molecules that contain the genes– 2. DNA = a complex molecule containing the

genetic information that makes up the chromosomes

– 3. Genes = The biochemical units of heredity that make up the chromosomes

– 4. Genome = The complete instructions for making an organism, consisting of all the genetic material in its chromosomes.

• B. Evolutionary Psychology– 1. The case of the

tame fox• a. Researchers in

Russia selectively bred foxes to create a tame fox that was completely domesticated

• b. Some 45,000 foxes and 40 years later, they have created a fox that can be a pet, replicating what may have happened between our ancestors and wolves that later became man’s best friend.

• c. This shows that certain traits can be inherited and selected for survival

– 2. Natural Selection• a. The principle that among the range of inherited

trait variations, those that lead to increased reproduction and survival will most likely be passed on to succeeding generations

• b. Mutation = a random error in gene replication that leads to change in the sequence of nucleotides – the source of all genetic diversity.

– 3. Evolutionary Psychology = the study of the evolution of behavior and the mind, using principles of natural selection.

• a. Natural selection has favored genes that designed both behavioral tendencies and information processing systems that solved adaptive problems faced by our ancestors.

• b. Thus contributing to the survival and spread of their genes.

– 4. Evolution and sexuality• a. Gender = in psychology the characteristics

whether biologically or socially influenced by which people define males and females.

• b. Sexuality especially attitudes towards sex is one of the greatest differences between the genders

• c. Evolutionary psychologist would say that the fact that women nurtured the child, caused this difference– Women mated wisely,

while men mated widely.

– Men are attracted to youthful women whose waist is three times as small as her hips – suggesting child rearing.

– Women were attracted to healthy looking men, but especially those who seem mature, dominant bold and affluent.

– 5. Critique of the Evolutionary Perspective• a. Starts with a behavior and works backwards so it

could be tainted by hindsight bias

• b. Others say it will lead to a type of determinism and loss of free will.

• C. Behavior Genetics– 1. Behavior Genetics = the study of the relative

power and limits of genetic and environmental influences on behavior.

– 2. Environment = every nongenetic influence from prenatal nutrition to the people and things around us.

• 3. Twin Studies– a. Identical twins =

twins who develop from a single fertilized egg that splits in two creating two genetically identical organisms

• b. Fraternal twins = twins who develop from separate eggs. They are genetically no closer than brothers and sisters, but the share fetal development

• c. Twin and Adoption Studies– Many cases of twins who have been separated at birth and

raised independently have been study to reveal the relative importance of both genetics and environment.

– The findings although criticized by some show many startling similarities.

– With adoption studies we look at siblings who were separated at birth and raised independently.

– The findings point to the importance of genetics over environment.

– 4. Heritability = the proportion of variation among individuals that we can attribute to genes. The heritability of a trait may vary, depending on the range of populations and environments studied.

– 5. Molecular Genetics = the subfield of biology that studies the molecular structure and function of genes

• D. Genetics and Human Disorders– 1. The X Chromosome – in humans females most often

have two x-chromosomes, while men only have one

– 2. The Y Chromosome – in humans males have on Y-chromosome whereas women have none

– 3. Genetic Disorders• a. Down Syndrome –

usually with 3 copies of chromosome 21 in their cells, individuals are typically mentally retarded, have a round head, flat nasal bridge, protruding tongue, small round ears, a fold in the eyelid and poor muscle tone and coordination

• b. Albinism = a recessive trait that produces lack of pigment and involves quivering eyes and inability to perceive depth with both eyes

• c. Hunnington’s Disease – a dominant gene defect that involves degeneration of the nervous system characterized by tremors, jerky motions, blindness and death

• d. Klinefelter’s syndrome – males with XXY chromosomes – often results in taller, leaner men with less bone density and muscle strength

• e. PKU – phenylketonuria is a recessive trait that results in severe, irreversible brain damage unless the baby is fed a special diet low in phenylalanine

• f. Tay-Sachs syndrome – Recessive trait that produces progressive loss of nervous function and death in a baby.

• g. Turner’s Syndrome – females with only one X chromosome. They are usually short, often sterile and have difficulty with calculations.

IX. Environmental Influence and Genetics

• A. Culture– 1. Culture is the enduring behaviors, ideas,

attitudes and traditions shared by a large group of people and transmitted from one generation to the next.

– 2. Norm = a norm is an understood rule for accepted and expected behavior. Norms prescribe “proper” behavior

– 3. Personal Space = the buffer zone we like to maintain around our bodies

– 4. Memes – Self replicating ideas, fashion and innovations passed from person to person.

• B. The Nature and Nurture of Gender– 1. Role = A set of expectations about a social

position.

• 2. Gender Role = a set of expected behaviors for males and females.

• 3. Gender Identity – one’s sense of being either male or female

• 4. Gender Typing – the acquisition of traditional masculine or feminine roles

– 5. Social Learning Theory = the theory that we learn social behavior by observing and imitating and being rewarded or punished.

– 6. Gender Schema Theory = the theory that children learn from their cultures a concept of what it means to be a male and female and that they adjust their behavior accordingly.

Prompt 7:

• Draw a brain and label the structures of the cerebral cortex.

Essay Question 1

• Describe the structure and function of the various parts of a neuron. Explain the process involved when a neuron goes from a state of rest to communicating with another neuron.

Bell-ringer 10

• Get a text book out of the closet and then label the two brain worksheets.

Links

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