Neuroscience The Brain and Behavior Neuroscience: The Brain and Behavior I. How is the Nervous System Organized? II. Methods of Studying the Brain III. How Does the Brain Function? IV. What Effects Do Hormones Have on Behavior? V. How Do Genetic Factors Affect Behavior? 1
I. How is the Nervous System Organized? A. Cellular Level 1. The Neuron Building block of the nervous system Single nerve cell = neuron Bundle of neurons = nerve or tract A. Cellular Level 1. The Neuron a. Three types of neuron i. Afferent or Sensory Neurons: Carry info to the brain & spinal cord ii. Efferent or Motor Neurons: Carry info from the brain & spinal cord to other structures in the body iii. Interneurons: Connect sensory and motor neurons 1. The Neuron b. Glial cells surround, nourish, and support the neurons Smaller than neurons More prevalent than neurons Form the myelin sheath that covers some large motor neurons Speeds up transmission of neural signals Multiple sclerosis causes a loss of myelination 2
1. The Neuron Alzheimer s Disease A progressive deterioration of cognitive skills (memory loss). Reduced branching of the dendrite trees. No cure. Etiology: genetic, defective gene on the 21 st chromosome, environmental factors. 1. The Neuron d. The Synapse Small space between neurons A. Cellular Level 2. The Functioning of Neurons Communication is an electrochemical process Within neurons it is electrical Between neurons it is chemical A thin membrane around the neuron allows the process 3
2. The Function of Neurons Partially permeable cell membrane Traps charged particles inside or outside the neuron At rest, the interior carries a negative electrical charge The exterior carries a positive electrical charge This difference in charges creates a state of polarization 2. The Function of Neurons Each neuron has a threshold Level of stimulation required for activation When the threshold is reached: Gates open in cell membrane Positive ions rush into cell Neuron is depolarized Relative charge is reversed Action potential has formed 2. The Function of Neurons Action potential The spike charge is an electrical current that travels down an axon If the threshold is not reached, the neuron will not fire All-or-none Principle Either the neuron fires or it doesn t Action potential is always the same strength 4
2. The Function of Neurons Neuron must recover between firings Refractory period No action potentials can occur until resting state is re-established A. Cellular Level 3. Neurotransmitters and Behavior Communication must cross the synapse between neurons Chemical signal At the axon terminal, the action potential causes the release of neurotransmitters 5
3. Neurotransmitters After binding with an adjacent neuron, one of two processes occurs Breakdown by enzymes Reuptake re-absorption by the terminal buttons (SSRI s) Neurotransmitters have two effects Excitatory: receiving neuron fires more easily. Increase the likelihood that neuron will fire Inhibitory: receiving neuron fires less easily. Decreases the likelihood Copyright that Allyn & the Bacon 2006 neuron will fire. 3. Neurotransmitters There are at least 50 different neurotransmitters Examples: Acetylcholine (Ach) Excitatory Receptors in skeletal muscles Involved in memory and learning Alzheimer s disease involves insufficient production of acetylcholine 3. Neurotransmitters Serotonin Inhibitory Involved in sleep regulation, appetite, anxiety, and depression Antidepressants affect serotonin A monoamine neurotransmitter 6
3. Neurotransmitters Dopamine Inhibitory Involved in movement, learning and memory, emotions, pleasure Also involved in Schizophrenia, ADHD, Parkinson s Disease 3. Neurotransmitters Norephinephrine Excitatory Involved in arousal, hunger, learning, memory, & mood disorders. 3. Neurotransmitters Neuropeptides are chemicals similar to neurotransmitters Endorphins Inhibitory, Painkillers. Occur naturally in the brain & bloodstream. Similar to morphine. 7
A. The Cellular Level 4. Neurotransmitters, Drugs and Behavior Psychopharmacology Study of how drugs affect behavior Types of effects: a. Alter amount of neurotransmitter released Ecstasy causes massive release of serotonin May also block release of neurotransmitters A. The Cellular Level Types of effects: a. Increase production of neurotransmitters b. L-dopa, used to treat Parkinson s disease 4. Neurotransmitters, Drugs, and Behavior c. Change the speed at which neurotransmitters are disabled after release Prozac and Zoloft slow reuptake of serotonin d. Bind to neurotransmitter receptor sites 8
4. Neurotransmitters, Drugs, and Behavior Medications to treat Schizophrenia are often dopamine antagonists Mimic effects of dopamine Reduce symptoms of schizophrenia Divisions of the NS Nervous System Central Nervous System Peripheral Nervous System Brain Spinal Cord Somatic NS Autonomic NS Sympathetic NS Parasympathetic NS Central Nervous System a. The Brain Lower structures are involved in more basic functions Higher structures are involved in more complex functions 9
Divisions of the Nervous System b. Spinal Cord Controls spinal reflexes without input from the brain Knee-jerk reflex Relays information to and from the brain Divisions of the Nervous System 2. Peripheral Nervous System (PNS) Carries information to and from the CNS Consists of neurons and nerves found outside the CNS 1. Peripheral Nervous System a. Somatic nervous system Responds to and acts on the external stimuli Under voluntary control Both sensory and motor neurons b. Autonomic nervous system Controls automatic processes Two subdivisions 10
1. Peripheral Nervous System b. Autonomic Nervous System (ANS) i. Sympathetic nervous system Produces physiological changes, increases heart rate, blood pressure, & respiration to perceived emergencies. Activates fight-or-flight response ii. Parasympathetic nervous system Controls normal physiological operations and calms the body Central Nervous System Brain Hindbrain Midbrain Forebrain b. The Brain i. The Hindbrain: Survival functions a) Medulla Controls involuntary reflexes, heartbeat and breathing Contains the reticular formation Passes through the midbrain into the forebrain Involved in arousal, sleep, attention b) Pons Links lower brain with the rest of the brain Also involved in sleep and arousal 11
i. The Hindbrain c) Cerebellum Little brain Influences balance, coordination, and movement Only 10% of brain volume, but has >50% of neurons Alcohol disrupts the cerebellum b. The Brain ii. Midbrain Collections of cell bodies that receive signals from the spinal cord and other parts of the brain Involved in smooth movement, temperature, and some reflexes b. The Brain iii. The Forebrain a) Thalamus Relay station for sensory information b) Hypothalamus: Controls ANS & endocrine system, body temperature, motivation & emotion Regulates hormone secretion, hunger, eating, drinking, homeostasis and sexual activity 12
b. The Brain c) The Limbic System: Hunger, sex, aggression, emotion, & memory Hippocampus Memory Amygdala Emotion iii. The Forebrain iii. The Forebrain c) Limbic System Contains the pleasure center Involved in addiction d) Basal Ganglia Link the thalamus and cortex Control movement and posture Degeneration is associated with Parkinson s Disease 13
iii. The Forebrain e) Cerebrum Largest structure in the human brain Two hemispheres Connected by the corpus callosum iii. The Forebrain e) Cerebrum Covered by the cortex 2 to 3 mm thick. Wrinkled and convoluted Controls cognitive functioning, voluntary action Left Hemisphere: Primarily speech, language, analytical skills, calculation Right Hemisphere: Primarily interpretation of emotions, creativity, intuition Neither hemisphere acts in isolation of the other Cerebral Cortex Gives the ability to think, evaluate, and make complex judgments Lobes Frontal Parietal Temporal Occipital 14
iii. The Forebrain Frontal Lobe e) Cerebrum Four lobes Parietal Lobe Occipital Lobe Temporal Lobe Methods of Studying the Brain A. Phrenology B. Anatomical Studies Brain lesions: Tissue damage Electrical Stimulation of the Brain (ESB): Technique used to relate activity in particular brain regions to behavior. II. Methods of Studying the Brain C. Monitoring Neural Activity Single-unit recording Measures activity in individual neurons Electroencephalography (EEG) Measures electrical activity Computerized Axial Tomography (CAT) scans Computer-enhanced X-rays 15
A. Monitoring Neural Activity Magnetic Resonance Imaging (MRI) Uses magnetic fields to trace activity & make up of tissue Images are clearer and more detailed than CT scans Positron Emission Tomography (PET) Tracks radioactive markers that have been injected into the bloodstream III.How Does the Brain Function? Information from damaged brains Damage from strokes and accidents Learned that Broca s area and Wernicke s area are involved in language 16
III. How Does the Brain Function? B. Brain Specialization 1. Splitting the brain Cerebral hemispheres are not identical Left hemisphere more involved in language Information comes from study of splitbrain patients Individuals whose corpus callosum has been cut to treat severe epilepsy Left and Right symmetrical Halves Left hemisphere controls the right side of the body Verbal competence Processes info sequentially Right hemisphere controls the left side of the body Spatial relationships Recognition of patterns Music Emotional expression Processes info globally 1. Splitting the Brain An image in the left visual field appears in the right (nonverbal) hemisphere when looking straight ahead???? 17
1. Splitting the Brain An image in the right visual field appears in the left (verbal) hemisphere when looking straight ahead It s a silly yellow and pink polkadotted bug. B. Brain Specialization 2. Gender and the Brain There are NOT masculine and feminine sides of the brain However, there are some gender differences Women may be less lateralized than men on some tasks Individual variation is larger than gender differences IV. What Effects Do Hormones Have on Behavior? Hormones are chemicals produced by endocrine glands Secreted directly into the bloodstream Regulate activities of specific organs or cells Slower action than that of neurotransmitters 18
III. Hormones Brain Behavior Endocrine Glands Target Organs III. Hormones III. Hormones B. Endocrine Glands 1. Pituitary Gland Master gland Regulates many other endocrine glands Linked to the hypothalamus 19
B. Endocrine Glands 2. Gonads Ovaries and testes Produce androgens and estrogens 3. Adrenal Glands Located above kidneys Produce adrenaline (epinephrine) B. Endocrine Glands 4. Pancreas Produces insulin Regulates body s sugar levels Diabetes mellitus results when pancreas doesn t produce enough insulin Hypoglycemia is caused by overproduction of insulin V. How Do Genetic Factors Affect Behavior? A. The Issue of Nature versus Nurture Nature refers to biology Nurture refers to environment Which is more influential? Neither can solely account for behavior Relative importance is source of much debate 20
V. How Do Genetic Factors Affect Behavior? B. The Basics of Genetics Each human cell contains 23 pairs of chromosomes Strands of DNA Carry genes Fundamental units of heredity Genetically determined traits are controlled by pairs of genes B. The Basics of Genetics Genotype A person s genetic make-up Fixed at birth Phenotype A person s observable characteristics Will reflect recessive traits only if both members of the gene pair are recessive B. The Basics of Genetics Mutation An unexpected change in gene replication Important sources of diversity in the human gene pool Not always undesirable 21
IV. How Do Genetic Factors Affect Behavior? C. How Genes Affect Behavior Genes affect behavior indirectly Behavioral genetics The study of the influence of genes on behavior Heritability The degree to which genetics influences traits C. How Genes Affect Behavior Twin Studies Fraternal Twins Dizygotic twins Two sperm and two eggs No more genetically similar than non-twin siblings Identical Twins Monozygotic twins One sperm and one egg split Identical genes C. How Genes Affect Behavior Twin Studies Identical twins raised apart share genes, but not environment Fraternal twins raised together share environment, but not genes Allows study of effects of genes and environment Most behaviors are determined by an interaction between genes and environment 22