2.1 Structure of the Neuron: The Nervous System’s Building Block

• Nervous System: an extensive network of specialized cells that carries information to and from all parts of the body

• Neuroscience: a branch of life science that deals with the structure and function of neurons, nerves, and nervous tissue

• Neuron: is the specialized cell in the nervous system that receives and sends messages within that system

• Dendrites: branchlike structures of a neuron that receive messages from other neurons

• Soma: the cell body of the neuron responsible for maintaining the life of the sell

• Axon: Tube-like structure of neuron that carries the neural message from the cell body to the axon terminals, for communication with other cells

• Axon Terminals: Enlarged ends of axonal branches of the neuron, specialized for communication between cells

• Glial Cells: Cells that provide support for the neurons to grow on and around, deliver nutrients to neurons, produce myelin to coat axons, clean up waste products and dead neurons, influence information processing, and during prenatal development, influence the generation of new neurons

• Myelin: fatty substances produced by certain glial cells that coat the axons of neurons to insulate, protect, and speed up the neural impulse

• Nerves: bundles of axons coated in myelin that travel together through the body

2.2 Generating the Message within the Neuron: The Neural Impulse

• Synaptic vesicles at the end of the axon terminal release neurotransmitter chemicals into the synapse, or gap, between one cell and the next. The neurotransmitter molecules fit into receptor sites on the next cell, stimulating or inhibiting that cell’s firing neurotransmitters may be either excitatory or inhibitory

• Diffusion: the process of molecules moving from areas of high concentration to areas of low concentration.

• Resting Potential: the state of the neuron when not firing a neural impulse

• Action Potential: the release of the neural impulse, consisting of a reversal of electrical charge within the axon

• All-or-none: referring to the fact that a neuron either fires completely or does not dire at all

2.3 Neurotransmission

• Synaptic Vesicles: saclike structures found inside the synaptic know containing chemicals

• Neurotransmitters: a chemical found in the synaptic vesicles that, when released, has an effect on the next cell

  • Acetylcholine (ACh) - Excitatory or inhibitory; involved in arousal, attention, memory, and controls muscle contractions

  • Norepinephrine(NE) - Mainly excitatory; involved in arousal and mood

  • Dopamine(DA) - Excitatory or inhibitory; involved in the control of movement and sensations of pleasure

  • Serotonin (5-HT) - Excitatory or inhibitory; involved in sleep, mood, anxiety, and appetite

  • Gamma-aminobutyric acid (GABA) - Major inhibitory neurotransmitter; involved in sleep and inhibits movement

  • Glutamate - Major inhibitory neurotransmitter; involved in sleep and inhibits movement

  • Endorphins - Inhibitory neural regulators; involved in pain relief

• Synapse (synaptic gap): microscopic fluid-filled space between the axon terminal of one cell and the dendrites or soma of the next cell

• Receptor sites: 3D proteins on the surface of the dendrites or certain cells of the muscles and glands, which are shaped to fit only certain neurotransmitters

• Excitatory Synapse: synapse at which a neurotransmitter causes the receiving cell to fire

• Inhibitory Synapse: synapse at which a neurotransmitter causes the receiving cell to stop firing

• Antagonists: chemical substances that block or reduce a cell’s response to the action of other chemicals or neurotransmitters

• Agonists: chemical substances that mimic or enhance the effects of a neurotransmitter on the receptor sites of the next cell, increasing or decreasing the activity of that cell

• Reuptake: Process by which neurotransmitters are taken back into the synaptic vesicles

• Enzymatic Degradation: Process by which the structure of a neurotransmitter is altered so it can no longer act on a receptor

2.4 The Central Nervous System: The “Central Processing Unit”

• Central Nervous System(CNS): part of the nervous system consisting of the brain and spinal cord

• Spinal Cord: A long bundle of neurons that carries messages between the body and the brain and is responsible for very fast, lifesaving reflexes

• Afferent (sensory) neuron: a neuron carries information from the senses to the central nervous system

• Efferent (motor) neuron: a neuron that carries messages from the CNS to the muscles of the body

• Interneuron: a neuron found in the center of the spinal cord that receives information from the afferent neurons and sends commands to the muscles through the efferent neurons. Interneurons also make up the bulk of the neurons in the brain.

• Reflex: an involuntary response, one that is not under personal control or choice

• Neuroplasticity: the ability within the brain to constantly change both the structure and function of many cells in response to experience or trauma

• Neurogenesis: the formation of new neurons; occurs primarily in prenatal development but may also occur at lesser levels in some brain areas during adulthood

• Stem cells: Special cells found in all tissues of the body that are capable of becoming other cell types when those cells need to be replaced due to damage or wear and tear

• Epigenetics: the interaction between genes and environmental factors that influence gene activity; environmental factors include diet, life experiences, and physical surroundings

2.5 The Peripheral Nervous System: Nerves on the Edge

• Peripheral Nervous System(PNS): all nerves and neurons that are not contained in the brain and spinal cord but that run through the body itself

• Somatic Nervous System: division of the PNS consisting of nerves that carry info from the senses to CNS and from the CNS to the voluntary muscles of the body

• Autonomic Nervous System(ANS): division of the PNS consisting of nerves that control all of the involuntary muscles, organs, and glands

• Sensory Pathway: nerves coming from the sensory organs to the CNS consisting of afferent neurons

• Motor Pathway: nerves coming from CNS to the voluntary muscles, consisting of efferent neurons

• Sympathetic Division: part of ANS that is responsible for reacting to stressful events and bodily arousal; “fight-flight system”

• Parasympathetic Divisions: part of ANS that restores the body to normal functioning after arousal and is responsible for the day-to-day functioning of the organs and glands; “eat-drink-and-rest system”

2.6 The Pituitary: Master of the Hormonal Universe

• Pituitary Gland: gland located in the brain that secretes human growth hormone and influences all other hormone-secreting glands (aka the master gland)

• Oxytocin: hormone released by the posterior pituitary gland that is involved in reproductive and parental behaviors

2.7 Other Endocrine Glands

• Pineal Gland: endocrine gland located near the base of the cerebrum; secretes melatonin

• Thyroid Gland: endocrine gland found in the neck; regulates metabolism

• Pancreas: endocrine gland; controls the levels of sugar in the blood

• Gonads: sex glands; secretes hormones that regulate sexual development and behavior as well as reproduction

• Ovaries: the female gonads or sex glands

• Testes: the male gonads or sex gonads

• Adrenal Glands: endocrine glands located on top of each kidney that secrete over 30 different hormones to seal with stress, regulate salt intake, and provide a secondary source of sex hormones affecting the sexual changes that occur during adolescence

2.8 Methods for Studying Specific Regions of the Brain

• Lesioning: insertion of a thin, insulated electrode into the brain through which an electrical current is sent, destroying the brain cells at the tip of the wire

• We can study the brain by using lesioning techniques to destroy certain areas of the brain in laboratory animals or by electrically stimulating those areas (ESB).

• We can use case studies of human brain damage to learn about the brain’s functions but cannot easily generalize from one case to another

• rTMS and tDCS are noninvasive methods for stimulating the brain

2.9 Neuroimaging Techniques

• Computed Tomography (CT) Scan: brain-imaging method using computer-controlled X-rays of the brain

• Magnetic Resonance Imaging (MRI): brain-imaging method using radio waves and magnetic fields of the body to produce detailed images of the brain

• Electroencephalogram (EEG): a recording of the electrical activity of large groups of cortical neurons just below the skull, most often using scalp electrodes

• Positron Emission Tomography: brain-imaging method in which a radioactive sugar is injected into the subject and a computer compiles a color-coded image of the activity of the brain

• Functional Magnetic Resonance Imaging (fMRI): MRI-based brain-imaging method that allows for the functional examination of brain areas through changes in brain oxygenation

2.10 The Structures of the Brain

• Medulla: the first large swelling at the top of the spinal cord, forming the lowest part of the brain, which is responsible for life-sustaining functions such as breathing, swallowing, and heart rate

• Pons: the larger swelling above the medulla that relays information from the cortex to the cerebellum, and that plays a part in sleep, dreaming left-right body coordination, and arousal

• Reticular Formation (RF): An area of neurons running through the middle of the medulla and the pons and slightly beyond that is responsible for general attention, alertness, and arousal

• Cerebellum: part of the lower brain located behind the pons that controls and coordinates involuntary, rapid, fine motor movement, and may have some cognitive functions

2.11 Structures Under the Cortex: The Limbic System

• Limbic System: a group of several brain structures located primarily under the cortex and involved in learning, emotion, memory, and motivation

• Thalamus: part of the limbic system located in the center of the brain, this structure relays sensory information from the lower part of the brain to the proper areas of the cortex and processes some sensory information before sending it to its proper area

• Olfactory bulbs: two bulb-like projections of the brain located just above the sinus cavity and just below the frontal lobes that receive information from the olfactory receptor cells

• Hypothalamus: small structure in the brain located below the thalamus and directly above the pituitary gland, responsible for motivational behavior such as sleep, hunger, thirst, and sex

• Hippocampus: curved structure located within each temporal lobe, responsible for the formation of long-term declarative memories

• Amygdala: brain structure located near the hippocampus, responsible for fear responses and memory of fear

2.12 The Cortex

• Cortex: outermost covering of the brain consisting of densely packed neurons, responsible for higher thought processes and interpretation of sensory input

• Cerebral Hemisphere: the two sections of the cortex on the left and right sides of the brain

• Corpus Callosum: a thick band of neurons that connects the right and left cerebral hemispheres

• Occipital Lobe: section of the brain located at the rear and bottom of each cerebral hemisphere containing the primary visual carters of the brain

• Parietal Lobes: sections of the brain located at the top and back of each cerebral hemisphere containing the centers for touch, temperature, and body position

• Somatosensory Cortex: area of cortex at the front of the parietal lobes responsible for processing information from the skin and internal body receptors for touch, temperature, and body position

• Temporal Lobes: areas of the cortex located along the side of the brain, starting just behind the temples, containing the neurons responsible for the sense of hearing and meaningful speech

• Frontal Lobes: areas of the brain located in the front and top, responsible for higher mental processes and decision making as well as the production of fluent speech

• Motor Cortex: rear section of the frontal lobe, responsible for sending motor commands to the muscles of the somatic nervous system

• Mirror Neurons: neurons that fire when an animal or person performs an action and also when an animal or person observes that same action being performed by another

2.13 The Association Areas of the Cortex

• Association Areas: areas within each lobe of the cortex responsible for the coordination and interpretation of information, as well as higher mental processing

• Broca’s Aphasia: a condition resulting from damage to Broca’s area, causing the affected person to be unable to speak fluently, to mispronounce words, and to speak haltingly

• Wernicke’s Aphasia: a condition resulting from damage to Wernicke’s area, causing the affected person to be unable to understand or produce meaningful language

2.14 The Cerebral Hemispheres: Are you in your Right Mind?

• Spatial Neglect: condition produced most often by damage to the parietal lobe association areas of the right hemisphere, resulting in an inability to recognize objects or body parts in the left visual field

• Cerebrum: the upper part of the brain consisting of the two hemispheres and the structures that connect them