IB Biology Past Paper Notes PDF

IB Version Mr. Dunlop [email protected]  Learning Outcomes This unit will focus on: – Discuss the use of brain imaging technologies in investigating the relationship between biological factors and behavior. – Explain localization of function in the bra...

IB Version Mr. Dunlop [email protected]  Learning Outcomes This unit will focus on: – Discuss the use of brain imaging technologies in investigating the relationship between biological factors and behavior. – Explain localization of function in the brain with reference to relevant research. – Using one or more examples, explain effects of neurotransmission on behavior. – Using one or more examples, explain functions of two hormones on behavior. – Discuss neuroplasticity and its effect on behavior.  Neuropsychology While evolution and heritability influence our actions, they are far from the only physiological influences that have an impact. Neuropsychology focuses on the role of the brain and nervous system on behavior.  Neurons  Messages to and from the brain travel through long, thin cells of nerve tissue called neurons , or nerve cells.  Neurons are held in place by glia, or glue cells, which make up 90% of our brain.  Neurons communicate through electrical signals called action potentials.  Neural communication is governed by the all-or-none principle.  Parts of the Neuron  Cell body – contains the nucleus and supplies the energy needed for the reaction to occur  Dendrites – branches that receive messages from other neurons  Axon – long fiber that transmits messages through the neuron  Most axons are insulated with a fatty glaze known as myelin. The myelin contains gaps called nodes of ranvier.  Axon Terminals – send info to other neurons Parts of the Neuron  Neurotransmission  There is a gap between the axon terminals that connect two separate neurons, called the synaptic cleft.  When the action potential reaches the terminal button, neurotransmitters are released from the tiny bubbles they are stored in (called synaptic vesicles).  These neurotransmitters bind to the receptor site of the receiving dendrite.  Action Potentials  Neurotransmitters that are unused in the reaction are either broken down or reabsorbed by the terminal buttons, a process called reuptake.  The message sent by the neuron may be excitatory (causing the receiving neuron to fire) or inhibitory (depress firing). Synaptic Activity  Neurotransmitters  Dopamine – related to learning, movement, emotion, and pleasure  High levels of dopamine are associated with euphoria and energy but also aggression and impulsive actions.  Drugs overload the brain’s dopamine pathway, causing physical changes.  Like drugs, romantic love can also be “addictive” due to its association with dopamine. This occurs in the ventral tegmental area (VTA).  Fisher et al (2003) found major differences in brain activation when people viewed pictures of the person they were in love with.  Neurotransmitters  Serotonin – regulates mood, sleep, arousal, and appetite  Unlike dopamine, serotonin has an indirect effect on depression because it is involved in the balance of other chemicals.  Serotonin is also an inhibitory neurotransmitter, it suppresses neural signals instead of enhancing them.  Exposure to sunlight or foods high in tryptophan can naturally boost serotonin levels.  Agonists vs. Antagonists  Psychoactive drugs are those that alter brain chemistry. There are two types:  Agonists – increase the level of neurotransmitter in the brain  Antagonists – decrease the level  One of the most common agonists is SSRI drugs – selective serotonin reuptake inhibitors.  Crockett et al. (2010) found that SSRIs can increase prosocial behavior.  Hormones  Chemical messages, called hormones, are sent through the body by the endocrine system.  One hormone that affects behavior is testosterone, which is correlated with aggression.  Testosterone is produced in the gonads and is an androgen (masculinizing hormone).  Men produce far more testosterone than women (270 – 1,070 ng vs. 15-70).  McDermott et al. (2007) found a correlation between testosterone levels and aggressive behavior in a game situation.  Hormones Circadian rhythms are controlled by a tiny part of the hypothalamus called the suprachiasmatic nucleus or SCN. – The SCN regulates levels of hormones and neurotransmitters that fluctuate throughout the day. Melatonin is a hormone that helps keep our biological clocks synchronized to the light-dark cycle. Its levels rise when we are in a darkened environment. – High melatonin levels are one of the leading explanations for SAD.  Hormones Often people show similar symptoms to major depression, but only in the winter time. This is called seasonal affective disorder, or SAD. SAD is often tied to the fact that periods of daylight are shorter in wintertime. It is often treated through light therapy. Avery et al. (2001) found dawn simulation to be a more effective treatment option for SAD than bright- light therapy.  Localization  Psychologists have found that different parts of the brain are responsible for specific tasks, though there is a large amount of overlap. This concept is called localization of function.  Strict localization asserts that each brain part has its own specific role.  Relative (weak) localization instead says that multiple brain areas overlap to contribute to a behavior.  The Frontal Lobe  The frontal lobe is the area of the brain that governs decision making, planning, judgement, and the control of emotions.  The frontal lobe is not fully mature in human beings until the approximate age of 25.  The frontal lobe communicates with the limbic system to coordinate emotions. The limbic system creates an immediate response while the frontal lobe regulates it.  Harlow (1848) was one of the first to discover this through his case study of Phineas Gage.  Broca’s Area  Broca’s Area is located in the left frontal lobe. It controls speech.  Issues with language are known as aphasia. Broca’s aphasia involves loss of speech.  This area usually works in concert with other language centers such as Wernicke’s area, which controls language comprehension.  Broca (1861) was a case study that followed a man named Tan and used autopsy to pinpoint the area of his brain damage.  The Hippocampus  The hippocampus is the memory processing area of the brain.  The hippocampus does not store memories, however it is responsible for the transfer of STM to LTM.  Different areas of the hippocampus have different roles. For instance, the posterior hippocampus controls the encoding of spatial layouts.  Milner & Scoville (1958) conducted a case study on a man named HM. His hippocampus was removed in an experimental surgery to cure his debilitating seizures. Parts of the Brain The Lobes of the Brain  Lateralization  Lateralization – the idea that each side of the brain has its own unique functions.  The left side of the brain controls the right side of the body and vice versa.  The hemispheres are also specialized; the left hemisphere controls much of our verbal and mathematical skills, while the right controls spatial and creative abilities.  These differences have been exaggerated however.  Lateralization  The hemispheres, or halves, of the brain are connected by the corpus callosum  Split-brain surgery, an operation that removes the corpus callosum, remains a treatment for severe seizures though it has odd side effects.  Sperry and Gazzaniga (1968) conducted the most famous study on split brain surgery, looking at the abilities of 11 participants.  Myers and Sperry (1953) found that cats with split brain surgery could learn a maze with one eye blindfolded, but when the blindfold was reversed they were unable to repeat the behavior.  Neuroplasticity  Plasticity refers to the brain’s ability to rearrange neural connections  The brain is often able to shift functioning to a different area, especially after brain damage, such as an accident or stroke.  Neural networks refer to the systems of connections created by plasticity – often through learning.  Neural pruning is when the brain removes unneeded connections.  Neuroplasticity  There are two major types of plasticity: synaptic plasticity and cortical remapping.  The process of forming new connections is called dendritic branching. Humans form new dendritic connections as a result of environmental experiences.  Rosenzweig and Bennett (1972) showed that rats who grew up in an enriched environment had far more cerebral neural connections than those who were deprived.  Draganski et al. (2004) found that learning to juggle was associated with structural changes in the brain.  Brain Imaging  Imaging techniques are among the most often used to learn about the brain.  CAT scans use x-ray beams to view the brain’s structure.  PET scans involve an injection of a slightly radioactive substance to look for function.  An MRI uses radio frequencies and magnets to see structure.  fMRI, uses natural blood oxygen level (BOLD signals) rather than radio frequencies and can produce high quality images of brain changes. PET CAT fMRI  Evaluation of Brain Scans  Brain scans differ in terms of resolution:  Spatial resolution refers to how detailed the picture taken is (measured in voxels).  Temporal resolution refers to how precise we can see the changes over time (i.e. frames per second).  Brain scans can also have limits on who can use them:  CAT and PET scans may have issues with exposure to radiation.  MRI and fMRI scans use giant magnets and are not suitable for those with metal in their body.  Research on Brain Imaging  Harris and Fiske (2006) used fMRI to find that activity in the medial prefrontal cortex was reduced when participants looked at extreme outgroups.  This is similar to the brain mechanisms that underlie disgust.  Ashtari et al. (2009) used MRI to find the negative effects in brain development correlated with teenage marijuana use.  Abnormalities were found in the frontal, parietal, and temporal lobes as well as a decrease in myelin.  Biology and Mental Disorders  Major depression involves a minimum two week period of uncontrollable sadness and negative emotions.  Depression is a moderately biological disorder as it is only 37% heritable.  Biological causes of depression usually stem from low levels of serotonin and norepinephrine.  Caspi et al. (2003) found a genetic link between depression and low levels of serotonin (5-HTT gene).  Biology and Mental Disorders  Antisocial Personality Disorder (ASPD) is a personality disorder that involves lack of empathy towards others.  ASPD is quite heritable for a personality disorder with estimates around 41%.  ASPD is often tied to specific brain abnormalities. These typically involve underactivity in areas involved in emotion.  Raine et al. (1997) used PET scans to find that murderers pleading not guilty by reason of insanity had less activation in the frontal lobe and amygdala than a healthy control.