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Chapter 21 Brain Structure and Function Attention Deficit Disorder Copyright © 2010 Pearson Education, Inc. 21.1 The Nervous System The nervous system Neurons carry electrical and chemical messages to and from the brain Neurons receive, process, and respond to stimuli. Three general categories of neurons 1. Sensory neurons 2. Interneurons 3. Motor neurons Copyright © 2010 Pearson Education, Inc. 21.1 The Nervous System Interneurons (within brain or spinal cord) Motor neurons (from brain) Sensory neurons (to brain) See and smell cookies Smile and salivate Copyright © 2010 Pearson Education, Inc. Figure 21.2 21.1 The Nervous System Sensory detectors can be either: 1. Sensory neurons 2. Specialized cells that communicate with neurons General Senses •Temperature •Pain •Pressure •Touch •Proprioception Copyright © 2010 Pearson Education, Inc. Table 21.1 21.1 The Nervous System Special Senses •Smell •Taste •Vision •Hearing •Equilibrium Copyright © 2010 Pearson Education, Inc. Table 21.1 21.1 The Nervous System Special Senses •Smell •Taste •Vision •Hearing •Equilibrium Copyright © 2010 Pearson Education, Inc. Table 21.1 21.1 The Nervous System The nervous system is divided into two parts: 1. Central nervous system brain and spinal cord 2. Peripheral nervous system nerves extending from vertebrae out to body Interneuron relays signal Sensory neuron senses heat Motor neuron withdraws hand from heat Hot stimulus Reflex arc sensory neuron that synapses to an interneuron and then motor neuron action without higher processing (e.g., knee jerk reflex) Copyright © 2010 Pearson Education, Inc. Figure 21.4 21.1 The Nervous System Focus on Evolution Muscle & Nervous tissue is unique to the animal kingdom Enables animals to sense environment & move in search of food All animal nervous systems have similar properties. Copyright © 2010 Pearson Education, Inc. Brain Spinal cord Sense organs Nerves Figure 21.1 21.1 The Nervous System - Focus on Evolution Primitive Animal Nervous System Nerve Nets • Found in hydras, sea anemones & jellyfish •Limited travel through environment •No brain Copyright © 2010 Pearson Education, Inc. Figure E21.2 21.1 The Nervous System - Focus on Evolution Nerve Cords •Found in insects •Processing of information centralized in CNS •Simple brain plus many enlarged ‘ganglia’ Copyright © 2010 Pearson Education, Inc. Figure E21.2 21.1 The Nervous System - Focus on Evolution Vertebrate Nervous Systems • Greater degree of centralization •Single large brain •Regions of brain become specialized for specific tasks Copyright © 2010 Pearson Education, Inc. Figure E21.3 21.2 The Brain Human Brain The brain rests in the skull in cerebrospinal fluid, which bathes and cushions it. Two major cell types in the brain 1. Neurons transmit nervous impulses Brain has 100-200 billion neurons 2. Glial cells support neurons by providing protection & nutrients Almost 10 times as many glial cells as neurons Copyright © 2010 Pearson Education, Inc. Figure 21.6 21.2 The Brain The brain is divided into 5 regions 1. Cerebrum 2. Cerebellum 3. Thalamus 4. Hypothalamus 5. Brain stem Copyright © 2010 Pearson Education, Inc. 21.2 The Brain - Cerebrum Lobes of the Cerebrum 1. Frontal lobe 2. Temporal lobe 3. Parietal lobe 4. Occipital lobe Copyright © 2010 Pearson Education, Inc. Other Important Structures •Right & Left Hemispheres •Central fissure •Corpus callosum •Caudate nuclei Figure 21.7 21.2 The Brain - Cerebrum Brain Hemispheres •Many nerves cross over, so left brain controls right side of body, and visa versa •Left Hemispheres •Controls speech, reading, & solving math •Right Hemispheres •Interprets spatial relationships, music & art Copyright © 2010 Pearson Education, Inc. Figure 21.7 21.2 The Brain - Thalamus and Hypothalamus Thalamus and hypothalamus lie deep in the brain between the hemispheres and act as control center. Thalamus relays information from spinal cord to brain. Thalamus suppresses some information and enhances other. Hypothalamus is the control center for sex drive, pleasure, pain, hunger, and other basic drives. Copyright © 2010 Pearson Education, Inc. 21.2 The Brain - Cerebellum Cerebellum Control of balance Coordination of muscular movement Damage to the cerebellum results in jerky, awkward movements Copyright © 2010 Pearson Education, Inc. 21.2 The Brain - Brainstem Brainstem Controls involuntary activity. The brainstem is composed of the midbrain, pons, and medulla oblongata Copyright © 2010 Pearson Education, Inc. Figure 21.8 21.2 The Brain ADD and Brain Structure and Function Some researchers suggest there are differences between brains of people with ADD and people without. Corpus callosum smaller in individuals with ADD Decreased folding on cerebrum in ADD individuals Differences could be a result of genetics, or development and life experiences Copyright © 2010 Pearson Education, Inc. 21.3 Neurons Neurons Neurons are highly specialized cells Parts of Neuron Dendrites Cell Body Axon Terminal Boutons Copyright © 2010 Pearson Education, Inc. Figure 21.9 21.3 Neurons - Neuron Structure Myelin speeds up nervous impulses Many neurons have their axons covered by a myelin sheath made by Schwann cells the unmyelinated patches are the nodes of Ranvier. Copyright © 2010 Pearson Education, Inc. Figure 21.10 21.3 Neurons - Neuron Function Neuron Function Cell accumulates K+ ions inside and Na+ ions outside (a) Resting nerve cell Outside cell Inside cell All channels are closed. The inside of the cell has a more negative charge than the outside of the cell. Nodes of Ranvier K+ channel Na+ channel Nerve cell Copyright © 2010 Pearson Education, Inc. Figure 21.11a 21.3 Neurons - Neuron Function Nervous Impulse = Action Potential Stimulation of a neuron causes ion gates to open, and Na+ rushes in, changing polarity (depolarization) Action potential (nervous Impulse) – a brief change in polarity of the surface membrane, which moves down the length of an axon Copyright © 2010 Pearson Education, Inc. Figure 21.11b 21.3 Neurons - Neuron Function PLAY Animation—Communication Within Neurons: The Axon Copyright © 2010 Pearson Education, Inc. 21.3 Neurons - Neuron Function How Neurons Work Copyright © 2010 Pearson Education, Inc. 21.3 Neurons - Neuron Function Synapse = junction between neurons Terminal boutons, space, & dendrites or cell body Synaptic transmission = Transmission of impulses between neurons neurons use neurotransmitters to communicate chemically across the synapse Copyright © 2010 Pearson Education, Inc. 21.3 Neurons - Neuron Function Synaptic Transmission 1. 2. 3. 4. 5. Action potential reaches terminal bouton of presynaptic cell Calcium gates open, allowing Ca2+ to rush in Ca2+ causes synaptic vesicles to release neurotransmitters Neurotransmitter binds to receptors on postsynaptic cell Opening or ion channels triggers action potential in postsynpatic cell Copyright © 2010 Pearson Education, Inc. Figure 21.12 21.3 Neurons - Neuron Function Two ways to stop synaptic transmission 1. Neurotransmitter is digested by enzymes 2. Reuptake of neurotransmitters by presynatpic cell Copyright © 2010 Pearson Education, Inc. Figure 21.12 21.3 Neurons - Neuron Function PLAY Animation—Communication Within Neurons: The Synapse Copyright © 2010 Pearson Education, Inc. 21.3 Neurons Alzheimer’s, Depression, Parkinson’s, and ADD Many mental diseases are linked to problems with neurotransmitters. Alzheimer’s and Parkinson’s diseases seem to be related to impaired neurotransmitter production. Depression appears to be related to an imbalance in several neurotransmitters, but its unclear if this is a cause or a result of depression. ADD may be result of lower levels of neurotransmitter dopamine. Copyright © 2010 Pearson Education, Inc. 21.3 Neurons - ADD Perscription Drug Action Ritalin •Blocks reuptake receptors on presynaptic cells •Increases dopamine in synapse Adderall & Dexedrine •Both are amphetamines •Increase levels of dopamine in synapse Copyright © 2010 Pearson Education, Inc. Figure 21.13