Chapter 3

CHAPTER THREE: BIOLOGICAL FOUNDATIONS OF BEHAVIOR

Learning Objectives

LO 3.1: Describe the parts and functions of the nervous system.

LO 3.2:Explain what neurons are and how they process information.

LO 3.3:Identify the brain’s levels, structures, and functions.

LO 3.4:State what the endocrine system is and how it affects behavior.

LO 3.5:Describe the brain’s capacity for recovery and repair.

LO 3.6:Explain how genetics increases out understanding of behavior.

LO 3.7:Describe the role of the biological foundations of human psychology in the body’s stress response.

  1. Chapter Overview
  2. Chapter Features
  3. Connections
  4. Teaching the Chapter
  5. Lecture Outlines by Section
  6. Suggested Activities
  7. Critical Thinking Questions
  8. Polling Questions
  9. Apply Your Knowledge
  10. Suggested Readings and Media
  11. Activity Handouts
  12. Answer Key to Activity Handouts

I.Chapter Overview

Experiencing Psychology: Changing the brain, changing the person

  • The chapter begins depicting two stories related to individuals who suffered from traumatic brain injuries which left themselves and loved ones a new set of challenges and experiences to overcome.
  • These examples illustrate the brain’s role in human experience as well as its mysterious nature. The brain, in this case, is not just the object we are studying, but also the reason we are able to study it.
  1. The Nervous System
  • The nervous system is the body’s electrochemical communication system.
  • Neuroscience is the field of study of the nervous system. The researchers that conduct research on the nervous system are called neuroscientists.
  1. Characteristics of the Nervous System
  1. Complexity
  1. The brain is composed of billions of nerve cells, and the orchestration of these nerve cells allows a person to carry out a variety of activities.
  2. The human brain and nervous system are incredibly complex and awe inspiring.
  1. Integration
  1. The brain integrates information from the environment so that people can function in the world.
  2. Each nerve cell in the brain communicates with 10,000 other nerve cells, which allows your nervous system to process a multitude of experiences at various levels simultaneously.
  1. Adaptability
  1. As the world is constantly changing, the brain and nervous system allow persons to adapt to those changes.
  2. Plasticity refers to the brain’s special physical capacity for change.
  3. Because the brain has plasticity, it can change in response to experience.
  1. Electrochemical Transmission
  1. Electrical impulses and chemical messenger systems allow the brain and nervous system to work as an information-processing system.
  2. For a person with epilepsy, the electrochemical system is shortcircuited, the information being passed is disrupted, and the person is not able to engage in mental processing and behavior.
  1. Pathways in the Nervous System
  1. As a person interacts with and adapts to the world around them, the brain and nervous system receive and transmit incoming sensory information. They integrate this information and direct the body’s motor activities.
  2. Afferent nerves carry information to the brain and are considered sensory nerves. These nerves communicate information about the external environment and internal conditions from the sensory receptors to the brain and spinal cord.
  3. Efferent nerves carry information from the brain to the body and are considered motor nerves which facilitate communication from the brain and spinal cord to other areas of the body.
  1. Divisions of the Nervous System
  1. The central nervous system (CNS) is comprised of the brain and spinal cord.
  1. The peripheral nervous system (PNS) is comprised of the nerves that connect the brain and spinal cord to other parts of the body. The function of the peripheral nervous system is to bring information to and from the brain and spinal cord. It also carries out the commands of the CNS.
  1. The peripheral nervous system is comprised of the somatic nervous system and the autonomic nervous system. The function of the somatic nervous system is to convey information from the skin and muscles to the CNS. It regulates information about pain and temperature. The autonomic nervous system’s function is to take messages to and from the body’s internal organs and so it regulates breathing, heart rate, and digestion.
  2. The autonomic nervous system is comprised of both the sympathetic nervous system and the parasympathetic nervous system. The sympathetic nervous system prepares a person for a stressful situation and the parasympathetic nervous system calms the body down after the stressful situation.
  3. The sympathetic nervous system is associated with the “fight or flight” response while the parasympathetic nervous system may be thought of as the system that “rests and digests.”
  1. Neurons
  2. Neurons are the nerve cells that control the information-processing function.
  3. Mirror neurons are specialized cells that appear to respond to both sensory and motor information.
  4. These specialized cells, mirror neurons, are activated when we perform an action or when we watch someone perform the same action. The role of these cells has sparked predictions about the function of neurons in imitating, social cognition, empathy, and understanding behavior.
  5. Glial cells provide the support and nutrition in the nervous system.
  6. New research suggests that glial cells may play a more active role in memory, Alzheimer disease, pain, some psychological disorders, and the development of neural stem cells.
  1. Specialized Cell Structures
  1. Not all neurons are alike, but they all do have a cell body, dendrites, and an axon.
  2. The cell body contains the nucleus, which manufactures what the neuron needs for growth and maintenance.
  3. Dendrites receive information and send that information on to the cell body.
  4. The axon carries information away from the cell body and to other cells.
  5. A myelin sheath covers the axon and is semipermeable, meaning that only certain substances can pass into and out of the axon. It is responsible for the insulation of axons and the speed of transmission of nerve impulses.
  6. Multiple sclerosis is a nerve disorder that occurs when there is a breakdown of the myelin sheath.
  1. The Neural Impulse
  1. In order for a neuron to send information to another neuron, the source neuron sends an electrical charge.
  2. Positive and negative ions are floating inside and outside of the axon. The positive ions are sodium and potassium. The negative ions are chlorine.
  3. Inside the membrane of the axon are gated channels known as ion channels. The ion channels open and close allowing the positive and negative ions to cross into and out of the axon. When the neuron is at rest and not transmitting information, the ion channels are closed and there is a negative charge on the inside of the axon and a positive charge on the outside of the axon.
  4. When a neuron is inactive, it is said to be at resting potential.
  5. When an electrical impulse flows down the axon it becomes depolarized. The channels open and the positive ions move into the axon and negative ions move outside the axon. The potassium channels open and the positive ions move back out and return the axon to its normal charge.
  6. An action potential is the term given to the electrical impulses flowing down the axon.
  7. The all-or-none principle refers to the process during which when an electrical impulse reaches a certain level of intensity it fires and moves all the way down the axon without losing any of its intensity. It can be compared to a firecracker.Once the fuse is lit, the spark will travel to the end with the same intensity with which it started.
  1. Synapses and Neurotransmitters
  1. Synaptic Transmission
  1. Synapses are the junctions between neurons: the space between one neuron and the dendrites of another neuron is called the synaptic gap.
  2. At the end of the axon there are fibers that end in what are called terminal buttons. Neurotransmitters are stored in the terminal buttons. The neurotransmitters carry the electrical information across the synaptic gap.
  3. After the neurotransmitter crosses over the synaptic gap, it gets picked up by a receiving neuron. Most neurons pick up and secrete only one type of neurotransmitter.
  4. Neurotransmitters are like puzzle pieces; they fit into a specific receptor site in order to continue sending the message.
  5. After the neurotransmitter has delivered it message, some of the chemical is reabsorbed. This is known as reuptake.
  1. Neurochemical Messengers
  1. There are a variety of neurotransmitters. Each plays a different role and function. Some neurotransmitters excite the neuron and cause it to fire, while other neurotransmitters inhibit the neuron.
  2. Scientists are not sure exactly how many neurotransmitters exist; over 100 have been identified in the brain alone.
  1. Acetylcholine (ACh)
  • Acetylcholine sets the firing of neurons into motion and is involved in muscle action, learning, and memory.
  • Botox works by deactivating ACh from moving facial muscles; as a result, wrinkles are less likely to form.
  • Individuals with Alzheimer disease have a deficiency in ACh.
  1. GABA
  • GABA keeps many neurons from firing. Low levels of GABA are involved in anxiety.
  1. Glutamate
  • Glutamate has a role in exciting neurons to fire and is particularly involved in learning and memory.
  • Too much glutamate can overstimulate the brain and trigger headaches and seizures.
  • Recently, researchers have proposed glutamate as a factor in anxiety, depression, schizophrenia, Alzheimer’s disease, and Parkinson’s disease.
  1. Norepinephrine
  • Norepinephrine inhibits neuron firing in the CNS, but it excites the heart muscles, intestines, and urogenital tract.
  • Stress releases norepinephrine.
  • Norepinephrine also helps control alertness; too little is associated with depression.
  1. Dopamine
  • Dopamine is an inhibitory neurotransmitter and helps control voluntary movements.
  • Dopamine also affects sleep, mood, attention, and learning.
  • Low levels of dopamine are associated with Parkinson’s disease.
  • Dopamine is related to the personality trait of extroversion.
  1. Serotonin
  • Serotonin is mostly an inhibitory neurotransmitter.
  • Serotonin is involved in sleep regulation, mood, attention, and learning.
  • Low levels of serotonin are associated with depression.
  1. Endorphins
  • Endorphins stimulate neuron firing.
  • Endorphins alleviate pain and elevate feelings of pleasure and are considered natural opiates.
  1. Oxytocin
  • Oxytocin is a hormone and neurotransmitter that plays an important role in the experience of love and social bonding.
  • Recent studies found that high levels of oxytocin were found in new lovers and that these levels were still elevated six months later.
  • Research as linked oxytocin to the ways that some individuals respond to stress, namely, women. This may help explain why, when stressed, women seek out relationships and bonds.
  1. Drugs and Neurotransmitters
  1. Drugs can have a variety of effects on the functioning of neurotransmitters.
  2. Some drugs interfere with the work of a neurotransmitterwhile other drugs mimic or increase the effect of a neurotransmitter.
  1. Neural Networks
  2. Neural networks are interconnected pathways of nerve cells that integrate sensory input and motor output.
  3. Neural networks can be altered through changes in synaptic connections.
  4. The strength of connected neurons determines how well a person remembers information.
  1. Structures of the Brain and Their Functions
  • Neuron networks are not visible to the human eye; however, technology has helped neuroscientists form pictures of the structures of the neurons and the brain.
  1. How Researchers Study the Brain and Nervous System
  • Much of the brain imaging available today came from studies on patients with brain damage or injury from disease.
  1. Brain Lesioning
  1. Brain lesions can be a result of injury or disease.
  2. Neuroscientists also make lesions in the brains of animals to see the effect on the animal’s behavior.
  3. Brain lesions can be made by removing brain tissue, destroying tissue with a laser, or eliminating tissue by injection with a drug.
  1. Electrical Recording
  1. The electroencephalograph (EEG) records the electrical activity in the brain. When electrodes are placed on a person’s scalp they detect brain-wave activity, and this is recorded on a chart.
  2. The EEG is used to assess brain damage, epilepsy, and other problems.
  3. A study using EEG activity suggests that positive emotion provoking experiences tended to activate the left prefrontal area, while fear-provoking experiences tended to activate the right prefrontal area, suggesting that brain activity in the left prefrontal area was related to higher measures of well-being, self-acceptance, positive relations with others, purpose in life, and life satisfaction.
  4. Single-unit recording is used when a probe is inserted in or near an individual neuron. The probe transmits the electrical activity to an amplifier so researchers can see the activity.
  1. Brain Imaging
  1. A computerized axial tomography or CAT scan(also called CT scan) produces a three-dimensional image that is obtained through x-rays of the head.
  2. A positron-emission tomography or PET scan measures the amount of glucose in various areas of the brain and then it sends this information to a computer where it is analyzed.
  3. A magnetic resonance image (MRI) creates a magnetic field around a person’s body and uses radio waves to construct images of the person’s tissue and biochemical activities.
  4. Afunctional magnetic resonance image (fMRI) allows researchers to see what is happening in the brain while it is working and tells us about the brain activity associated with the mental experience.
  5. Transcranial Magnetic Stimulation (TMS) allows for causal inferences between brain activity and behavior.
  6. Scientists induce brief electrical pulses in the brain, which triggers action potentials followed by an immediate deactivation of action potential, causing a virtual lesion.
  7. If a particular area of the brain is associated with a behavior, then the temporary disruption of processing in that area should disrupt the behavior as well.
  1. How the Brain Is Organized
  • The nervous system starts out as a long, hollow tube and then three weeks after conception, cells making up the tube start to differentiate into neurons. These neurons begin to develop into the three major parts of the brain: the hindbrain, the midbrain, and the forebrain.
  1. Hindbrain
  1. The hindbrain is the lowest portion of the brain.
  2. The medulla helps in controlling breathing and regulates reflexes.
  3. The cerebellum controls leg and arm movements.
  1. The pons is involved in sleep and arousal.
  2. The brain stemhouses the medulla, pons, and much of the hindbrain and gets its name largely due its natural stem-like shape. The brain stem regulates survival-type functions such as breathing, heartbeat, and blood pressure.
  1. Midbrain
  1. The midbrain is located between the hindbrain and the forebrain.
  2. The midbrain communicates information between the brain and the eyes and ears.
  3. The reticular formation is involved in walking, sleeping, or turning to attend to a noise.
  1. Forebrain
  2. The forebrain is the highest level of the brain.
  1. Limbic System
  1. The limbic system is important in both memory and emotion.
  2. The amygdala is kind of like an awareness center. It fires selectively at the sight of appropriate foods, mates, and social rivals. The amygdala is also involved in emotional awareness and expression.
  3. The hippocampus is involved in the formation and storage of memories. People who have hippocampus damage cannot retain any new memories after the damage.
  1. Thalamus
  1. An important function of the thalamus is to sort through information and send it to the appropriate place in the forebrain.
  1. Basal Ganglia
  2. The basal ganglia works with the cerebellum and the cerebral cortex in coordinating voluntary movements.
  3. Hypothalamus
  4. The hypothalamus monitors eating, drinking, sexual behavior, emotion, stress, and reward.
  1. The Cerebral Cortex
  2. The cerebral cortex controls some of the highest mental functions such as thinking and planning.
  3. The outermost part of the cerebral cortex is known as the neocortex and makes up to 80 percent of the cortex.
  1. Lobes
  1. The lobes are divided into two hemispheres and each hemisphere is divided into four lobes: the frontal lobe, the parietal lobe, the temporal lobe, and the occipital lobe.
  1. The occipital lobe involves visual stimuli.
  2. The temporal lobe involves hearing, language processing, and memory.
  3. The frontal lobe is involved in the control of voluntary muscles, intelligence, and personality. Phineas Gage was a railroad worker who during an accident had an iron rod go through his face up into his brain. The iron rod went through his frontal lobe. After the accident, Phineas’ personality changed dramatically. He was obstinate, moody, irresponsible, selfish, and incapable of taking part in planned activities.
  4. The prefrontal cortex (a part of the frontal lobe) which is at the front of the motor cortex is involved in higher cognitive functions such as planning, reasoning, and self-control.
  5. The parietal lobe involves registering spatial location, attention, and motor control.
  1. Somatosensory Cortex and Motor Cortex
  1. The somatosensory cortex processes information about bodysensations and is located in front of the parietal lobes.
  2. The motor cortex processes information about voluntary movements.
  3. The somatosensory and motor areas are associated with different parts of the body. Wilder Penfield conducted research on the somatosensory and motor areas and found that when he stimulated a part of one of the areas, a certain part of the body would move.
  1. The Association Cortex
  1. The association cortex processes information about sensory input and motor output.
  2. There are association areas throughout the brain and each sensory system has its own association area in the cerebral cortex.
  3. The association cortex is involved in thinking and problem solving.
  1. The Cerebral Hemispheres and Split-Brain Research
  1. Expressive aphasiais a language disorder that involves the inability toproduce language and is related to brain injury.
  1. Damage to Broca’s area will cause a person to have difficulty in speaking, or speech production.
  2. Damage to Wernicke’s area will cause a person to have difficulty understanding spoken language, or language comprehension.
  3. The corpus callosum is a bundle of axons that connects the left and right hemispheres.