Transcript Part 1
CHAPTER 3 OUTLINE BIOLOGICAL PROCESSES Part 1 I. Communicating Internally: Connecting World and Brain A. Main components of the nervous system 1. Sensory neurons – Neurons which make contact with the environment and carry signals toward the brain 2. Interneurons – The most plentiful neurons in the nervous system. They convey information from one internal processing site to another. 3. Motor neurons –Neurons which carry messages and commands away from the central nervous system to the muscles and glands. 4. Glial cells – These cells are not directly involved in communicating signals, but help to maintain neurons. Glial cells comprise the myelin sheath, which insulates neurons and speeds neural communication 5. Reflexes – Automatic reactions that are controlled by the spinal cord pathways. Reflexes require no initial input from the brain. Reflex path: sensory neurons interneurons motor neurons B. Anatomy of neurons 1. Dendrites – Branch-like fibers that receive chemical information from other neurons 2. Soma – The main body of the neuron cell that processes chemical information received from the dendrites. The soma also stores the cell’s genetic material (DNA) 3. Axon – The long tail-like part of a neuron that transmits electrochemical signals from the soma a. action potential – The electrochemical message that fires from the axon hillock through the axon to the terminal buttons b. terminal buttons – Tiny swellings at the end of the axon which contain neurotransmitters to be released into the synaptic gap 4. Synapse – the tiny fluid filled gap between neurons C. Neural Transmission: The Electrochemical Message 1. Flow of the electrochemical message – the electrochemical message is picked up by the dendrites, organized in the soma, released through the axon and exits through the terminal buttons 2. Resting potential – the tiny electrical charge in place between the inside and the outside of resting neurons a. sodium & potassium ions – contain a positive charge b. chloride ions – contain a negative charge c. sodium-potassium pump – maintains a slight negative charge inside the neuron (- 70 mv) 3. Generating an action potential – if the charge inside the neuron becomes less negative (moving toward “0”) an all or none firing of an action potential occurs a. excitatory messages – (depolarization) ion channels open, the charge moves toward “0” (becomes less negative) and an action potential fires through the axon b. inhibitory messages – (hyperpolarization) the charge inside the neuron becomes more negative (moving toward resting potential) and the action potential does not fire c. characteristics of the action potential – it fires in an “all or none” fashion through the axon like a gun with consistent intensity 4. Neurotransmitters: The Chemical Messengers – neurotransmitters are molecules which interact chemically with the post synaptic membrane of other neurons a. acetylcholine – a neurotransmitter which acts as a major messenger in the central and peripheral nervous system. Alzheimer's disease is related to a lack of acetylcholine production in the brain b. dopamine – a neurotransmitter which produces mostly inhibitory effects that stabilize neural communication (1.) schizophrenia – a disease which results from excessive dopamine levels in the brain. Drugs that decrease dopamine levels; reduce schizophrenic symptoms such as hallucinations and delusions (2.) Parkinson’s disease – the drug Levadopa (L-Dopa) is used to increase dopamine levels in Parkinson’s patients; reducing tremors and other movement problems c. serotonin – a neurotransmitter that affects sleep, dreaming and general arousal (awareness). Depression and OCD are related to an imbalance in serotonin levels in the brain d. GABA – (gamma amino-butyric acid) a neurotransmitter which is involved in regulation of anxiety. Tranquilizers such as Valium are used to regulate GABA in the brains of people with anxiety disorders 5. Drugs and the Brain a. agonists – mimic the action of neurotransmitters example; Nicotine mimics the action of acetylcholine b. antagonists – block the effects of neurotransmitters example; Blow darts tipped with curare block acetylcholine and cause paralysis c. endorphins – Morphine-like chemicals in the brain that are released to kill pain example; Runner’s high occurs when a rush of endorphins is released by the brain D. The Communication Network – Involves the operation of thousands of neurons in concert to produce thoughts, feelings, and actions. 1. pattern of activation – groups of neurons operating at the same time to produce conscious experience 2. firing rate – the number of action potentials that a neuron can produce per unit of time 3. refractory period – the unit of time it takes for a neuron to regenerate another action potential E. Neural Networks – computer simulation models of neural communication networks in the brain to represent brain activity CHAPTER 3 OUTLINE BIOLOGICAL PROCESSES Part 2 II. Initiating and Coordinating Behavior: A Division of Labor A. The Central and Peripheral Nervous System 1. The central nervous system – includes the brain and spinal cord which act as the central executive of the body (a.) nerves – bundles of axons that communicate messages throughout the body 2. The peripheral nervous system – all the nerves outside the brain and spinal cord (a.) afferent nerve pathways – (sensory pathways) neural information travels toward the brain and spinal cord (b.) efferent nerve pathways – (motor pathways) carry messages away from the brain and spinal cord (c.) somatic nervous system – carries sensory nerve information toward the brain and controls mostly voluntary muscle movement (d.) autonomic nervous system – controls automatic body functions such as heart rate, blood pressure, respiration, and digestion * sympathetic division – part of the autonomic system that prepares the body for emergencies by increasing heart rate, respiration etc. (fight or flight response) * parasympathetic division – part of the autonomic system that calms the body down, returns it to normal after an emergency B. Determining Brain Function 1. Brain Damage and Lesion (a.) Observation of characteristics – to learn about how the brain functions normally, researchers study brain damaged individuals (b.) Broca’s Aphasia - an individual with brain damage to Broca’s area – understands spoken language but cannot accurately produce spoken language (c.) Wernicke’s Aphasia – an individual with damage to Wernicke’s area – cannot accurately understand spoken language (d.) Lesioning – researchers may selectively damage areas of an animal’s brain to see how it affects behavior 2. Devices to Study the Brain (a.) EEG – (Electroencephalograph) device which records gross (general) electrical activity in regions of the brain (b.) CT Scan – (Computerized Tomography) device which provides pictures of brain structures using X-rays (c.) PET scan – (Positron Emission Tomography) device which looks at the active brain as it operates using a radioactive substance (dye) (d.) MRI – (Magnetic Resonance Imaging) device which isolates the structures and functions of the brain in 3-D images using magnetism without radioactive dye C. Brain Structures and Their Function 1. Hindbrain – provides basic life support for the body, considered the most primitive region of the brain (Reptilian Brain) (a.) Medulla and Pons – these areas in the hindbrain maintain basic life support functions such as heart rate, blood pressure, respiration, and certain reflexes (b.) Reticular Formation – a network of nerves in the hindbrain that controls general arousal (sensory awareness) (c.) Cerebellum – (little brain) the structure in the hindbrain that is involved in planning and coordination of complex motor skills 2. Midbrain – the midbrain structures serve as neural relay stations (a.) Tectum colliculus (superior and inferior) – midbrain structure which relays auditory and visual information and coordinates sensory input (b.) Substantia nigra – midbrain structure which releases dopamine and acts as a center for motor control (area likely damaged by Parkinson’s disease) 3. Forebrain – area of the brain involved in higher order mental processes (a.) Cerebral cortex – forebrain area that forms the entire outer layer of the brain and makes up 80% of the brain’s overall volume (Mammalian Brain) (b.) Thalamus – egg-shaped structure in both hemispheres of the forebrain that gathers and relays all sensory input (except smell) (c.) Hypothalamus – tiny forebrain structure beneath the thalamus that regulates motivational activities such as eating, drinking, body temperature, and sexual arousal (d.) Limbic system – part of the forebrain involved in emotional, defensive, and motivational responses * amygdala – limbic structure that controls aggressive and defensive behaviors * hippocampus – limbic structure that is important in the formation and retrieval of memories 4. Cerebral cortex – the outermost layer of the cerebrum that is the seat of higher order mental functions, divided into the left and right hemispheres (a.) Corpus callosum – the thick bundle of nerves that serves as the neural communication bridge between the left and right hemispheres ( b.) The hemispheres – The left cerebral hemisphere controls sensory and motor functions on the right side of the body. The right hemisphere controls the left side of the body. * frontal lobes – area in the front of the brain that processes higher order thinking such as planning, decision-making, and personality. Also contains the motor cortex which controls voluntary muscle movements * parietal lobes – central area of the cerebrum which contains an area called the somatosensory cortex for sensing touch, temperature, pain etc. * temporal lobes – areas located on the left and right sides of the brain which process auditory information, speech ,and language. The left temporal lobe contains the primary speech center * occipital lobes – area located in the back of the brain which processes visual information such as color, motion, and form