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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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

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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

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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

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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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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