The Brain and Behavior

Chapter Preview

· This chapter will cover the following domains:

· The nervous system

· Neurons

· Structures of the brain and their functions

· Brain damage, plasticity, and repair

· Genetics and behavior

· As with chapter 1, this presentation will serve as a study guide, highlighting the most important concepts which you should study for your midterm by reading your textbook in depth

Nervous System: Characteristics

· The nervous system is a massive electrochemical communications system. This system is notable for its:

· Complexity – there are billions of neurons and trillions of connections between them

· Integration – the different systems of the brain work together seamlessly

· Adaptability – the brain can adapt to certain amounts of damage in certain areas. How well it handles this depends on many factors, from the system affected to the age of the person (children are more adaptive than adults). The concept of plasticity reflects the brain’s ability to rewire or re-route around damage.

Nervous System: Characteristics

· This chapter has a lot of terminology – names for parts and systems of the nervous systems of the brain. This study guide will not repeat all of these definitions. However, any such terms listed in this study guide may be on your exam, and so you should be sure to focus on those listed here are you study.

Nervous System: Pathways

· Afferent Nerves

· Also called sensory nerves, they carry information about the environment to brain and spinal cord

· Efferent Nerves

· Also called motor nerves, they carry information from the brain and spinal cord to the rest of the body

· Neural Networks

· Networks of cells that integrate sensory input and motor output

Nervous System: Primary Divisions

· Central Nervous System (CNS)

· Brain and spinal Cord

· Peripheral Nervous System (PNS)

· Network of nerves connecting CNS to body

· Two subdivisions:

· Somatic nervous system

· Autonomic nervous system

Nervous System: PNS Divisions

· Somatic nervous system

· Carries sensory information from skin and muscles to CNS

· Autonomic nervous system

· Communicates to and from internal organs

· Two subdivisions:

· Sympathetic nervous system arousing

· Parasympathetic nervous system calming

Nervous System: Cells

· Neurons

· Nerve cells

· Information processing

· Glial cells

· Cells that support functionality of neurons

· Nutritional benefits

Neurons: Structure

· Cell body

· Contains nucleus

· Dendrites

· Fibers projecting from neuron

· Axon

· Carries information from cell body toward other cells

The Neuron

Neural Impulse

· Neurons communicate by sending electrochemical impulses (signals) from an axon to the dendrite of the next neuron

· Normally, an axon exists in a stable, negative electrical state. This is called the resting potential

· However, when the neuron is stimulated, positive ions flow into the axon, creating a change in electrical charge

· Once this impulse reaches a certain level of intensity, called a threshold, it triggers an action potential, in which the electrical charge moves down the axon to the terminal buttons at the end of the axon.

Synapses and Neurotransmitters

· The terminal buttons exist at the synapses, which are sites where axons meet dendrites from other neurons. These do not touch; rather they meet at a synaptic gap

· Once the action potential is reached, the terminal button will release neurotransmitters across this gap

· These are chemicals which transmit information across the synaptic gap

Synapses and Neurotransmitters

Neurotransmitters

· Neurotransmitters are excitatory (stimulating neurons to fire), inhibitory (telling the next neuron not to fire), or both

· Different neurotransmitters are tied to different functions. Please review the list on the next slide, and study the general functions of each neurotransmitter as described in your book

Neurotransmitters

· Acetylcholine

· GABA

· Norepinephrine

· Dopamine

· Serotonin

· Endorphins

· Oxytocin

Studying the Brain

· We now work our way up from the level of cells to the level of the brain

· It used to be the case that researchers had very limited means via which to study the brain, mostly focused on doing autopsies of people who suffered from some sort of mental illness or disability, in the hope of finding something distinctive in their brain

· Today, researchers can study such damage using brain imaging techniques. They also can study and record brain electrical activity, and they can surgically alter brain structure through the process of lesioning

Types of Brain Imaging

· X-ray two-dimensional images

· CT (or CAT) scan three-dimensional images

· PET scan metabolic changes

· MRI brain structure

· f MRI brain function

Organization of the Brain

· Hindbrain

· Adjacent to top part of spinal cord

· Midbrain

· Rises above hindbrain

· Forebrain

· Uppermost region of brain

· We’ll walk through various parts of the brain. While we’ll look at general levels of specialized functionality, it is important to understand that many functions are spread across many parts of the brain at any given time. Certain parts may be more involved, but they are seldom exclusively involved.

Structure and Regions in the Human Brain

Hindbrain

· Medulla

· Controls vital functions

· Breathing and heart rate

· Regulates reflexes

· Cerebellum

· Motor coordination

Hindbrain

· Pons

· Sleep and arousal

· Brain stem

· Includes much of hindbrain (but not cerebellum) and midbrain

· Determines alertness

· Regulates basic survival functions

Midbrain

· Reticular formation

· Involved in stereotyped patterns of behavior, such as walking, reacting to sudden noises, and sleeping

Forebrain

· Limbic system

· Hypothalamus

· Cerebral cortex

Forebrain: Limbic System

· Important in both memory and emotion

· Two principal structures

· Amygdala

· Discrimination of objects necessary for survival

· Strongly tied to emotional response

· Hippocampus

· Has special role in storage of memories

Forebrain: Hypothalamus

· Monitors a number of survival functions:

· Eating, drinking, and sex

· Emotion, stress, and reward

· Helps direct endocrine system

· Regulator of body’s internal state

· Involved in pleasurable feelings

Forebrain: Cerebral Cortex

· Largest, most highly evolved, most uniquely human part of the brain

· Divided into to halves, called hemispheres, each of which are divided into four regions, called lobes

The Cerebral Cortex’s Lobes and Association Areas

Forebrain: Cerebral Cortex

· Frontal lobes

· Personality, intelligence, control of voluntary muscles

· Motor cortex – located just behind frontal lobes

· Processes information about voluntary movement

· Parietal lobes

· Registering spatial location, attention, motor control

· Somatosensory cortex – located at front of parietal lobes, adjacent to motor cortex

· Processes information about body sensations

Forebrain: Cerebral Cortex

· Occipital lobes

· Responding to visual stimuli

· Temporal lobes

· Hearing, language processing, memory

· Association cortex

· Makes up 75% of cerebral cortex

· Integrates information

Cerebral Hemispheres

· Corpus callosum

· Large bundle of axons connecting brain’s two hemispheres

· Relays information between two sides

· Left Hemisphere

· Receives information from right side of body

· Language processing, such as speech and grammar

· Right Hemisphere

· Receives information from left side of body

· Processing nonverbal information, such as spatial perception, visual recognition, and emotion

Genetics and Behavior

· Our understanding of the connection between genetics and behavior is somewhat general, and far from complete

· While some aspects of genetics create clearly defined outcomes (e.g. four limbs, blue eyes), within psychology genetics more often leads to predispositions, which must be interpreted with caution

· A predisposition means that you are more likely than someone else to demonstrate a characteristic, all other things being equal

· However, all other things are never equal. This predisposition interacts with your environment, your other personality traits, your biology, and with countless other aspects of your life

· We can identify these predispositions across larger populations, but these predispositions are seldom usefully predictive at the level of the individual

Genetics – General Terms

· Chromosomes

· Threadlike structures containing DNA

· DNA (deoxyribonucleic acid)

· Complex molecule that carries genetic information

· Genes

· Units of hereditary information

· Genome

· Complete set of genetic instructions for making an organism

· Human genome project

· International research program mapping human genome

Genes and the Environment

· Genotype

· Genetic heritage; your actual genetic material

· Phenotype

· How your genotype is manifested in terms of observable characteristics

· Influenced by both genotype and environmental factors

· Genetic expression: activity of genes is affected by their environment

The Study of Genetics

· Dominant-recessive genes principle

· Genes come in pairs, from mother and father

· Some genes are dominant; if a dominant gene is present, it will override the other and will be manifested as the phenotype. These characteristics will be more prevalent in the population

· Some genes are recessive; they can be overridden by a dominant gene if present, but can be part of the phenotype in absence of the dominant gene

· Polygenic inheritance

· Any given behavior is influenced by multiple genes

The Study of Genetics

· Behavior genetics

· Study of degree and nature of heredity’s influence on behavior

· Twin Studies

· These compare the similarity and differences between identical vs. fraternal twins

· Identical twins have identical DNA, fraternal twins have only 50% overlap in DNA. By comparing the differences between these populations (and comparing them against other populations, like siblings, parent-child, cousins, adoptive children) we can try to figure out the relative importance of DNA vs. environment in human behavior

The Study of Genetics

· Molecular genetics

· Manipulation of genes using technology to determine their effect on behavior

· Selective breeding

· Genetic method used to demonstrate importance of genetic influence on behavior, via breeding of an organism to optimize or minimize the genetic presence of a particular trait