Biological Bases of Behavior

Biological Bases of Behavior

• Focuses on the body and its influence on behavior.

AP Exam: Biological Bases of Behavior (8–10%)

• Examines the relationship between physiological processes and behavior.
• Includes the influence of neural function, the nervous system, the brain, and genetic contributions.
• Key areas of study:
  • Basic processes and systems in the biological bases of behavior.
  • Parts of the neuron and signal transmission between neurons.
  • Influence of drugs on neurotransmitters (e.g., reuptake mechanisms, agonists, antagonists).
  • Effect of the endocrine system on behavior.
  • Nervous system and its subdivisions and functions (central and peripheral nervous systems).
  • Major brain regions, lobes, and cortical areas.
  • Brain lateralization and hemispheric specialization.
  • Role of neuroplasticity in traumatic brain injury.
  • Historic and contemporary research strategies and technologies (e.g., case studies, split-brain research, imaging techniques).
  • Interaction of heredity, environment, and evolution in shaping behavior.
  • Adaptive value of traits and behavior.
  • Key contributors (e.g., Paul Broca, Charles Darwin, Michael Gazzaniga, Roger Sperry, Carl Wernicke).

Psychology and Biology

• Everything psychological is simultaneously biological.
• The mind and body are interconnected; we are bio-psycho-social systems.
• Understanding behavior requires studying the interaction of biological, psychological, and social systems.

The Brain, The Mind and Psychology

• The human brain is a complex system.
• Weighs about 3 lbs.
• Pinkish/gray in color.
• Composed of about 100 billion nerve cells.
• Adults lose approximately 200,000 brain cells per day, but retain over 98% of their brain cells.
• Includes a diagram showing the relative size of the human brain.

Biopsychology

• Biopsychology studies the interaction of biology, behavior, and mental processes.
• It explores the mind thinking about the mind.

Innate Abilities

• Humans are born with certain innate abilities.
• Evolution is the gradual process of biological change in a species as it adapts to its environment.
• includes the example of Polydactyl Disorder.

A Wrongheaded Theory

• Early theories about the brain were inaccurate.
• Plato located the mind in the head.
• Phrenology, developed by a German physician in the early 1800s, incorrectly claimed that bumps on the skull reveal mental abilities and character traits.
• Mark Twain story referenced (likely as an example of phrenology's failings).

The Role of Evolution

• Evolution shapes psychology by favoring genetic variations that produce adaptive behavior.
• Evolution connects genetics and behavior.

Natural Selection

• Individuals best adapted to the environment are more likely to reproduce.
• Poorly adapted individuals produce fewer offspring.
• Accumulation of beneficial traits can lead to the formation of new species (Darwin, 1859).

Natural Selection: Owl Butterfly Example

• Uses the owl butterfly as an example.
• References a YouTube video: http://www.youtube.com/watch?v=dR_BFmDMRal

Misconceptions About Evolution

• Two common misconceptions:
  1. Darwin said humans come from monkeys.
     • In reality, he suggested a common ancestor millions of years ago.
  2. Behavior can alter heredity.
     • Larger brains did not develop so people could communicate; rather, people with bigger brains who could communicate had an easier time surviving.
     • Bigger brains became a dominant trait as a result.

Evolution as an Accepted Theory

• Most sciences accept evolution as a valid theory for over a century.
• Psychology has been slower to accept evolutionary psychology.
• Some psychologists argue it overemphasizes nature (biology) and neglects nurture (learning).

Genetics and Inheritance

• Genetics influence temperament, fears, and behavior patterns.
• Genetic inheritance is divided into genotype and phenotype.

Genotype and Phenotype

• Genotype: An organism’s genetic makeup or blueprint.
• Phenotype: An organism’s physical characteristics, including brain chemistry and “wiring”.
• Examples: eye color, hair color

Genes

• Genes: segments of chromosomes that encode directions for inherited physical and mental characteristics.
• They are the “words” that make up the organism’s instruction manual.

Twins

• Twins are ideal for studying genetics because identical twins come from the same zygote (monozygote).
• Bouchard Study (Minnesota Twin Study):
  • Aim: To determine the extent to which intelligence is attributable to genetics versus environment, by comparing MZAs (identical twins raised apart) to MZTs (identical twins raised together).
  • Behavior:
    • 70% attributed to genetics.
    • 30% may be attributed to environmental factors.

Dominant & Recessive Genes

• Dominant gene: actively controls the expression of a trait.
• Recessive gene: influences the expression of a trait only when paired with an identical gene.
• Video: https://www.youtube.com/watch?v=I7tZPYhIQXw

Genes also occur in pairs

• Just like chromosomes do!
• Eye Color example:
  • DOMINANT GENE (B for brown eyes)
  • RECESSIVE GENE (b for blue eyes)
  • bb = blue eyes
  • BB = brown eyes
  • Bb = brown eyes

Genetic Problems

• Diseases carried by recessive genes are inherited when a child inherits two recessive genes, one from each parent.
• Examples: cystic fibrosis, sickle-cell anemia.

Polygenic Inheritance

• A single gene contributes to more than one trait.
• Several genes interact to produce certain traits; responsible for most of our traits.
• It is rare for a single gene to control a single trait.
• Examples: weight, height, skin pigmentation.

Heredity and the Environment

• Heredity never acts alone; it always acts in partnership with the environment.
• The environment includes biological influences like nutrition, disease, and stress.

Influence of the Environment

• Genie the Wild Child example to illustrate the influence of environment.
• Video: https://www.youtube.com/watch?v=VjZolHCrC8E

Chromosomes, Genes and DNA

• Every cell carries a complete set of biological instructions.
• Humans have 23 pairs of chromosomes.
• Chromosomes are made of deoxyribonucleic acid (DNA).
• DNA holds unique genetic characteristics.
• DNA is an organic molecule arranged in a double-helix; contains the “code of life”.
• DNA is the only known molecule that can replicate or reproduce itself each time a cell divides.
• The sum of all our genes = the HUMAN GENOME, approximately 100,000 genes total.

Chromosome Numbers Vary Across Species

• Not all living things have 46 chromosomes like humans.
• Mosquitos have 6, Onions have 16, Carp have 104.

Chromosomes

• Threadlike structures consisting mostly of DNA, along which genes are organized.

Sex Chromosomes

• Two chromosomes responsible for determining a person’s biological sex: “XX” (Female) or “XY” (Male).
• Inherit an “X” from the mother; inherit either “X” or “Y” from the father.

Chromosomal Abnormalities

• Sex is determined by the 23rd pair of chromosomes (XX for women, XY for men).
• Turner’s syndrome: single X chromosome.
• Klinefelter’s syndrome: extra X chromosome (XXY).
• Down syndrome: extra chromosome on the 21st pair.

Why You Don’t Look Exactly Like Your Siblings

• You are not exact replicas of your parents.
• Inheritance from parents is a random shuffling of genes.
• This random shuffling and variation is what Darwin viewed as the raw material for evolution.

A Debate for the Future

• Ethical considerations regarding genetic selection.
• Possibility of parents selecting traits for their child in the future.
• Raises questions about whether this is a good idea.

How Your Body Communicates

• Internally, the body has two communication systems: the nervous system (fast) and the endocrine system (slow).

The Nervous System

• Begins with an individual nerve cell called a NEURON.
• Neurons share features with other cells:
  • Nucleus
  • Cytoplasm
  • Cell membrane

3 Main Tasks of Neurons

• Bundles of neurons are called nerves.
• Neurons perform 3 tasks:
  1. Receive information from other neurons.
  2. Carry information down its length.
  3. Pass the information on to the next neuron.

How Neurons Work

• The dendrite, or “receiver,” accepts incoming messages.
  • Consists of finely branched fibers.
  • Selectively permeable

How Neurons Work

• Dendrites pass the message to the soma/cell body (life support machinery).
• The soma assesses all messages and passes on appropriate information at the appropriate time.

How a Neuron Works

• When the soma decides to pass on a message, it sends it down the axon.
• The axon is a single, larger “transmitter” fiber extending from the soma.
  • This is a one way street

Axon

• The axon is the extension of the neuron through which neural impulses are sent.
• It carries information to the next cell.
• Axons vary in length (short in the brain, up to 3 feet in the leg).

Myelin Sheath

• Protects and insulates the axon and the electric signal.
• Speeds up the neural impulse.
• Made up of Schwann cells (specific type of glial cells).
• Video: http://www.youtube.com/watch?v=C4Gt322-XxI#t=173

Multiple Sclerosis (MS)

• The myelin sheath is destroyed.
• Leads to diminished or complete loss of neural functioning, particularly in muscle control and movement.
• Symptoms include fatigue, changes in vision, balance problems, and numbness, tingling, or muscle weakness in the arms or legs.

Let's Make a Mad, Mad Neuron

• http://learn.genetics.utah.edu/content/neuroscience/madneuron/

3 Types of Neurons

• Neurons vary in size and shape but share similar structure and function.
• Three categories based on location and function:
  • Sensory Neurons
  • Motor Neurons
  • Interneurons

Sensory Neurons

• Sensory neurons, or afferent neurons, carry information from sense organs toward the brain.
• They communicate all sensory experiences, including vision, hearing, taste, touch, smell, pain, and balance.

Motor Neurons

• Motor neurons, or efferent neurons, transport messages away from the brain to the muscles, organs, and glands.

Interneurons

• Interneurons relay messages between sensory and motor neurons in complex pathways.
• Sensory and motor neurons do not communicate directly; they rely on a middle-man.

How does a Neuron fire?

• Resting potential
  • The axon gets its energy from charged chemicals called ions.
  • Has a slight negative charge
  • This negative balance can be easily upset
• Action potential
  • When the cell becomes excited, it triggers, which reverses the charge and causes the electrical signal to race along the axon.

Absolute Threshold

• The neuron is a mini decision maker.
• It receives information from other neurons - some excitatory (pushing the gas pedal), others inhibitory (pushing the breaks).
• If the excitatory signals minus the inhibitory signals exceed a minimum intensity (absolute threshold), then action potential is realized.

Refractory Period

• Each action potential is followed by a brief recharging period, the refractory period.
• After the refractory period, the neuron is capable of another action potential.
• Analogy: Like waiting for the flash to recharge on a disposable camera before taking another picture.

The Neural Impulse

• Absolute refractory period: period immediately after an action potential when another action potential cannot occur.
• Relative refractory period: period following absolute refractory period when a neuron will only respond to a stronger than normal impulse.

All or Nothing

• Once the action potential is released, there is no going back.
• The axon either fires or it does not (all-or-none principle).
• A strong stimulus triggers more neurons to fire more often, but not any stronger.
• Analogy: Squeezing a trigger harder won't make the bullet go faster.

Depolarization & Polarization

• Depolarization: An axon that is firing.
• Positive ions enter the axon, causing other positive ions to move into the axon, forming a neural impulse down the axon.
• Polarization: An axon that is not firing.
• Outside Axon = + ions; Inside Axon = - ions

The Neural Impulse: Graded Potentials

• A temporary shift in the electric charge in a tiny area of neuron, transmitted along the cell membrane.
• May fade away if it doesn’t reach its threshold of excitement.
• Many subthreshold depolarizations are added together to produce an action potential (summation).

Neural Communication

• Illustrates the direction of neural impulse toward axon terminals.

How Cells Connect

• Neurons do not actually touch to pass on information.
• The gap between neurons is called the synapse, synaptic space, or synaptic cleft.
• The synapse acts as an electrical insulator, preventing an electrical charge from racing to the next cell.
• Composed of the terminal button of one neuron, the synaptic space, and the dendrites or cell body of the receiving neuron.

How Cells Connect

• To pass across the synaptic gap/cleft, an electrical message undergoes a change in the terminal buttons.
• Synaptic transmission: electrical charge is turned into a chemical message that flows easily across the synaptic cleft.

How Cells Connect

• In the terminal buttons are small sacs called synaptic vesicles, which contain neurotransmitters (chemicals released by synaptic vesicles).
• Neurotransmitter molecules take $1/10,000$th of a second to cross the synaptic gap.
• When the action potential reaches the vesicles, they rupture and release the transmitters.
• Transmitters fit into the receptors like a key into a lock.
• Receptor sites: location on receptor neuron for specific neurotransmitter.

Neural Communication

• Diagram illustrating the process of neural communication, including synaptic vesicles, neurotransmitters, synaptic cleft, and receptor sites.

Clean up of the Synapse & Reuptake

• Neurotransmitters are flushed from receptor sites before next stimulation.
• Some drift away through diffusion.
• Neurotransmitters that are not absorbed by the connecting dendrite are reabsorbed by the sending neuron in a process called reuptake.
• Reuptake affects neurotransmitters like serotonin.

Some Neurotransmitters and Their Functions

• Acetylcholine (ACh):
  • Function: Enables muscle action, learning, and memory.
  • Malfunction: Alzheimer’s disease (ACh-producing neurons deteriorate).
• Dopamine:
  • Function: Influences movement, learning, attention, and emotion.
  • Malfunction: Excess dopamine receptor activity linked to schizophrenia; lack of dopamine leads to tremors and decreased mobility of Parkinson’s disease.
• Serotonin:
  • Function: Affects mood, hunger, sleep, and arousal.
  • Malfunction: Undersupply linked to depression. Prozac and some other antidepressants raise serotonin levels.
• Norepinephrine:
  • Function: Helps control alertness and arousal.
  • Malfunction: Undersupply can depress mood.
• GABA (gamma-aminobutyric acid):
  • Function: A major inhibitory neurotransmitter.
  • Malfunction: Undersupply linked to seizures, tremors, and insomnia.
• Glutamate:
  • Function: A major excitatory neurotransmitter; involved in memory.
  • Malfunction: Oversupply can overstimulate the brain, producing migraines or seizures.
• Neurotransmitters can function differently based on their location in the nervous system.

Endorphins

• Feel-good chemicals.
• Many addictive drugs relate to endorphins.
• Released during exercise.
• Endorphins are classified as neuro-modulatory (modify the action of neurotransmitters through effects associated with pain or pleasure).

How Does It Work? Neural Communication: Drugs Can Be…

• Agonists (excite): make a neuron fire by amplifying or mimicking the sensation.
  • Example: Opiates mimic the high produced naturally.
• Antagonists (inhibit): stop neural firing by blocking the absorption of neurotransmitters.
  • Example: botulin blocks ACh (enables muscle action).
• Reuptake Inhibitors: block reuptake.

Neural Communication

• Agonist mimics neurotransmitter.
• Antagonist blocks neurotransmitter.

Psychopharmacology

• Most psychoactive drugs (and toxins) work by blocking or enhancing synaptic transmission.

• Botulism:

  • Blocks release of ACh at the neuromuscular junction, causing paralysis.
  • “Botox” is botulism toxin used to prevent facial muscles from making wrinkles.

Psychopharmacology

• Curare:
  • Can stun or kill prey quickly.
  • Blocks ACh receptors causing paralysis.
• Antipsychotic medications:
  • Block dopamine receptors.
  • Reduces schizophrenic hallucinations.
• Caffeine:
  • Increases the release of excitatory neurotransmitters by blocking the inhibitory neurotransmitter adenosine.

Psychopharmacology

• Cocaine:
  • Prevents reabsorption of dopamine.
  • Leads to heightened arousal of entire nervous system.

Neural Plasticity

• The brain can be changed, both structurally and chemically, by experience.
• The brain’s ability to form new connections after neurons are damaged.
• Younger brains are more plastic.
• “Enriched” environments lead to larger neurons with more connections (rat studies).
• Neurogenesis, or the production of new brain cells, occurs in human brains.

Cognitive Neural Prosthetics (CNP)

• A method for assisting paralyzed patients and patients with amputations.
• Allows patients to control prosthetics by simply thinking about doing something.

The Nervous System

• An overview of the nervous system's organization:
  • Central Nervous System:
    • Brain
    • Spinal Cord
  • Peripheral Nervous System:
    • Somatic Nervous System
    • Autonomic Nervous System
      • Sympathetic Nervous System
      • Parasympathetic Nervous System

Central Nervous System

• The brain and spinal cord.

The Spinal Cord

• Complex cable of nerves connecting the brain to the rest of the body.
• Acts as a communications superhighway.
• Carries motor impulses from the brain to internal organs and muscles.
• Carries sensory information from extremities and internal organs to the brain.

Peripheral Nervous System

• All nerves that are not encased in bone.
• Everything but the brain and spinal cord.
• Divided into two categories: somatic and autonomic.

Somatic Nervous System

• Controls voluntary muscle movement.
• Uses motor (efferent) neurons.

Autonomic Nervous System

• Controls the automatic functions of the body.
• Divided into two categories: the sympathetic and parasympathetic systems.

Sympathetic Nervous System

• Allows one to deal with a range of extreme emotions and stressful events – Fight or Flight Response.
• Adrenal glands are stimulated to release stress-related hormones, accelerating heart rate, dilating pupils, and increasing breathing rate.
• Slows down digestion.

Parasympathetic Nervous System

• Automatically slows the body down after a stressful event.
• Heart rate and breathing slow down, pupils constrict, and digestion speeds up.

Parasympathetic and Sympathetic Nervous System

• Comparison of the effects of the parasympathetic and sympathetic nervous systems on various bodily functions.

Reflexes

• Normally, sensory (afferent) neurons take information up through the spine to the brain.
• Some reactions occur when sensory neurons reach just the spinal cord.
• Considered a survival adaptation.

The Brain

• Made up of neurons and glial cells.
• Glial cells support neural cells.
  *Structures of the brain listed
  *Divisions of the brain listed

Glial Cells

• Cells that insulate and support neurons.
• Create the myelin sheath.
• Remove waste products.
• Provide nourishment.
• Prevent harmful substances from entering the brain.

Ways to Study the Brain!!!

• Accidents: Phineas Gage