Chapter 2 Brain and Behavior
Neuron and Its Parts Neuron: Individual nerve cell; 100 billion in brain
Neuron’s Parts –Soma: Cell body; body of the neuron. Receives messages and sends messages down axon –Axon: Fiber that carries information away from the cell body of a neuron –Axon terminals: Branches that link the dendrites and somas of other neurons –Dendrites: Receive messages from other neurons
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Fig. 2-4, p. 51
Video: Main Parts of the Neuron
The Nerve Impulse Resting potential: Electrical charge of an inactive neuron Threshold: Trigger point for a neuron’s firing Action Potential: Nerve impulse
Fig. 2-2, p. 50
More on Nerves Ion channels: Tiny openings through the axon membrane Negative after-potential: A drop in electrical charge below the resting potential Synapse: Microscopic space between two neurons over which messages pass
Saltatory Conduction Process by which nerve impulses conducted down the axons of neurons coated with myelin jump from gap to gap in the myelin layer Myelin: A fatty layer coating some axons
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Fig. 2-3, p. 50
Video: Action Potential
Video: Synaptic Transmission
Neurotransmitters Chemicals that alter activity in neurons; brain chemicals Receptor site: Area on the surface of neurons and other cells that is sensitive to neurotransmitters or hormones
Types of Neurotransmitters –Acetylcholine: Activates muscles –Dopamine: Muscle control –Serotonin: Mood and appetite control
Neural Regulators Neuropeptides: Regulate activity of other neurons –Enkephalins: Relieve pain and stress; similar to endorphins –Endorphins: Released by pituitary gland; also help to relieve pain Placebos raise endorphin levels
Fig. 2-6, p. 52
Neuroplasticity Capacity of our brains to change in response to experience
Neural Networks Central nervous system (CNS): Brain and spinal cord Peripheral nervous system: All parts of the nervous system outside of the brain and spinal cord
Nerves and Neurons (cont) Neurilemma: Thin layer of cells wrapped around axons outside brain and spinal cord; forms a tunnel that damaged fibers follow as they repair themselves
Fig. 2-7, p. 53
Two Divisions of the Peripheral Nervous System Somatic System: Carries messages to and from skeletal muscles and sense organs; controls voluntary behavior Autonomic System: Serves internal organs and glands; controls automatic functions such as heart rate and digestion pressure
Two Divisions of the Autonomic Nervous System Sympathetic: Arouses body; emergency system Parasympathetic: Quiets body; most active after an emotional event
Fig. 2-8, p. 54
The Spinal Cord Spinal Nerves: 31 of them; carry sensory and motor messages to and from the spinal cord Cranial Nerves: 12 pairs that leave the brain directly; also work to communicate messages
The Spinal Cord and Behavior Reflex Arc: Simplest behavior; occurs when a stimulus provokes an automatic response Sensory Neuron: Nerve cell that carries messages from the senses toward the CNS Connector Neuron: Nerve cell that links two others Motor Neuron: Cell that carries commands from the CNS to muscles and glands
Fig. 2-9, p. 54
Effector Cells Cells capable of producing a response
Neurogenesis The production of new brain cells
Brain Imaging Techniques Computed Tomographic Scanning (CT): Computer-enhanced X-ray of the brain or body Magnetic Resonance Imaging (MRI): Uses a strong magnetic field, not an X-ray, to produce an image of the body’s interior
Localization of Function Research strategy of linking specific structures in the brain with specific psychological or behavioral functions
Researching the Brain Ablation: Surgical removal of parts of the brain Deep lesioning: A thin wire electrode is lowered into a specific area inside the brain; electrical current is then used to destroy a small amount of brain tissue Electrical stimulation of the brain (ESB): When an electrode is used to activate target areas in the brain
Electroencephalograph (EEG) A device that detects, amplifies, and records electrical activity in the brain
More Brain Imaging Techniques Functional MRI: MRI that makes brain activity visible Positron emission tomography (PET): Computer-generated color image of brain activity, based on glucose consumption in the brain
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Cerebral Cortex Definition: Outer layer of the brain; contains 70% of neurons in CNS Cerebrum: Two large hemispheres that cover upper part of the brain Corticalization: Increase in size and wrinkling of the cortex Cerebral hemispheres: Right and left halves of the cortex
Corpus Callosum Bundle of fibers connecting cerebral hemispheres
Neurological Soft Signs Subtle behavioral signs of brain dysfunction –Clumsiness –Awkward gait –Poor hand-eye coordination –Other perceptual and motor problems
Fig. 2-17, p. 60
Split Brains Corpus callosum is cut; done to control severe epilepsy (seizure disorder) Result: The person now has two brains in one body This operation is rare and is often used as a last resort
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Fig. 2-16, p. 60
Right Brain/Left Brain Humans use 95 percent of our left brain for language –Speaking, writing, understanding
The Left Hemisphere Left hemisphere better at math, judging time and rhythm, and coordinating order of complex movements –Processes information sequentially
The Right Hemisphere Right hemisphere good at perceptual skills, and at expressing and detecting other’s emotions –Good at recognizing patterns, faces, and melodies –Processes information simultaneously and holistically
Frontal Lobe Movement, sense of smell, higher mental functions –Contains primary motor cortex; controls motor movement Mirror neurons: Contained in motor cortex; become active when motor action is carried out and when another organism is observed carrying out the same action
Video: Frontal Lobe
p. 65
Association Cortex All areas of cerebral cortex that are not primarily sensory or motor in function
Aphasia Language disturbance resulting from brain damage
Broca’s Area Related to grammar and pronunciation –If damaged, person knows what s/he wants to say but can’t say the words
Prefrontal Cortex Front of frontal lobes; involved in sense of self, reasoning, and planning
Parietal Lobe Just above occipital; bodily sensations such as touch, pain, and temperature (somatosensory area) Primary somatosensory cortex: Receiving area for bodily sensations
Temporal Lobe Each side of the brain; auditory center and, for 95 percent of humans, language centers Primary auditory area: Auditory information is first registered here
Wernicke’s Area Related to language comprehension; in left temporal lobe –If damaged, person has problems with meanings of words, NOT pronunciation
Fig. 2-24, p. 66
Occipital Lobe Back of brain; vision center Primary visual area: Part of occipital lobe that first receives input from the eyes
Fig. 2-19, p. 61
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Fig. 2-23, p. 64
Agnosias Visual Agnosia: Inability to identify seen objects Facial Agnosia: Inability to perceive familiar faces
Fig. 2-18, p. 61
Subcortex All brain structures immediately below cerebral cortex
Hindbrain (Brainstem) Consists mainly of medulla and cerebellum Also includes pons and reticular formation
Video: Hindbrain
Medulla Controls vital life functions such as heart rate, swallowing, and breathing
Pons (Bridge) Pons (Bridge): Acts as a bridge between medulla and other structures –Influences sleep and arousal
Cerebellum Cerebellum: Located at base of brain –Regulates posture, muscle tone, and muscular coordination
Reticular Formation (RF) Inside medulla and brainstem –Associated with alertness, attention, and some reflexes (breathing, coughing, sneezing, vomiting)
Reticular Activating System (RAS) Part of RF that keeps it active and alert –RAS acts like the brain’s alarm clock –Activates and arouses cerebral cortex
Video: Brainstem
Forebrain Structures are part of the limbic system, the system within the forebrain closely linked to emotional response and motivating behavior
Video: Limbic System
Thalamus Relays sensory information on the way to the cortex; switchboard
Hypothalamus Regulates emotional behaviors and motives (e.g., sex, hunger, rage, hormone release)
Amygdala Associated with fear responses
Hippocampus Associated with storing permanent memories; helps us navigate through space
Endocrine System Glands that pour chemicals (hormones) directly into the bloodstream or lymph system
Pituitary Gland Regulates growth via growth hormone Its hormones influence other endocrine glands
Pituitary Problems Too little growth hormone means person will be smaller than average –Hypopituitary dwarfism: As adults, perfectly proportioned but tiny Treatable by using human or synthetic growth hormone; will add a few inches
Fig. 2-25, p. 68
Fig. 2-26, p. 69
Pituitary Problems (cont) Too much growth hormone leads to gigantism (excessive body growth) Acromegaly: Enlargement of arms, hands, feet, and facial bones; due to too much growth hormone secreted late in growth period –Andre the Giant Pituitary also governs functioning of other glands, especially thyroid, adrenals, and gonads
The Pineal Gland Regulates body rhythms and sleep cycles –Releases the hormone melatonin, which responds to daily variations in light
The Thyroid Gland In neck; regulates metabolism –Hyperthyroidism: Overactive thyroid; person tends to be thin, tense, excitable, nervous –Hypothyroidism: Underactive thyroid; person tends to be inactive, sleepy, slow, obese, and depressed
The Adrenal Glands Adrenals: Arouse body, regulate salt balance, adjust body to stress, regulate sexual functioning; located on top of kidneys –Releases epinephrine and norepinephrine (also known as adrenaline and noradrenaline)
Adrenal Hormones Epinephrine arouses body; is associated with fear Norepinephrine arouses body; is linked with anger
The Adrenal Glands (cont) Adrenal medulla: Inner core of adrenals; source of epinephrine and norepinephrine Adrenal cortex: Produces hormones known as corticoids –Regulate salt balance, among other functions
Adrenal Malfunctions Oversecretion of adrenal sex hormones can cause virilism: exaggerated male characteristics (bearded woman) –May also cause premature puberty if oversecretion occurs early in life
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Fig. 2-29, p. 74
Handedness Preference for right or left hand in most activities Dominant Hemisphere: Term usually applied to the side of the human brain that produces language Lateralization: Specialization in abilities of brain hemispheres