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# Glandular Tissue & Lymphatic System ## Chapter 7: Glandular Tissue ### Summary This chapter details the endocrine and exocrine glands of the head and neck, their locations, secretions, functions, innervations, lymphatic drainage, and blood supply. Understanding these glands is crucial for dental professionals to identify disease processes. ### Key Information #### Gland Types - **Exocrine Gland:** Has a duct to empty secretions directly to the site of use (e.g., salivary glands). - **Endocrine Gland:** Ductless, secretes directly into the vascular system (e.g., thyroid gland). - Motor nerves regulate secretion flow; sensory nerves are also present. #### Lacrimal Glands - **Type:** Paired almond-shaped exocrine glands. - **Secretions:** Lacrimal fluid (tears) for lubricating the conjunctiva and eyeball. - **Location:** Lacrimal fossa of the frontal bone, just inside the lateral part of the supraorbital rim. - **Ducts:** Lacrimal ducts collect tears, which then pass to the lacrimal punctum, lacrimal sac, nasolacrimal duct, and finally drain into the inferior nasal meatus. - **Innervation:** Parasympathetic fibers from the greater petrosal nerve (branch of facial nerve), synapsing at the pterygopalatine ganglion. Postganglionic fibers reach the gland via maxillary branches of the trigeminal nerve and lacrimal nerve. - **Lymphatic Drainage:** Superficial parotid lymph nodes. - **Blood Supply:** Lacrimal artery (branch of ophthalmic artery); venous return via superior ophthalmic vein. - **Pathology:** Dry eye syndrome (DES) or keratoconjunctivitis sicca (KCS) due to reduced lacrimal fluid production. #### Salivary Glands - **Function:** Produce saliva to lubricate and cleanse the oral cavity, aid digestion, and contribute to immune defense. - **Control:** Autonomic nervous system. - **Types:** Major (large, encapsulated, named ducts) and Minor (smaller, more numerous, unencapsulated, shorter unnamed ducts). Both are exocrine. ##### Major Salivary Glands 1. **Parotid Salivary Gland** - **Type:** Largest encapsulated major salivary gland. - **Secretions:** Serous type only (25% of total salivary volume). - **Location:** Parotid space, posterior to mandibular ramus, anterior and inferior to each ear, overlying the masseter muscle. - **Duct:** Parotid duct (Stensen duct) opens into the oral cavity opposite the maxillary second molar. - **Innervation:** Efferent (parasympathetic) fibers from the otic ganglion of the glossopharyngeal nerve (ninth cranial nerve) via the lesser petrosal nerve. Postganglionic fibers carried by the auriculotemporal nerve (mandibular division of trigeminal nerve). Facial nerve passes through but does not innervate. - **Lymphatic Drainage:** Deep parotid lymph nodes. - **Blood Supply:** Transverse facial artery (branch of external carotid artery); venous return via retromandibular vein. - **Pathology:** Enlargement and tenderness with mumps (parotitis), most salivary gland cancers involve the parotid. 2. **Submandibular Salivary Gland** - **Type:** Second largest encapsulated major salivary gland. - **Secretions:** Mixed serous and mucous (60-65% of total salivary volume). - **Location:** Submandibular fossa in the submandibular space, inferior and posterior to the body of the mandible. - **Duct:** Submandibular duct (Wharton duct) opens at the sublingual caruncle in the floor of the mouth. - **Innervation:** Efferent (parasympathetic) fibers of the chorda tympani nerve (facial nerve) synapsing in the submandibular ganglion. Postganglionic fibers delivered by the lingual nerve (mandibular division of trigeminal nerve). - **Lymphatic Drainage:** Submandibular lymph nodes. - **Blood Supply:** Glandular branches of the facial artery; venous return mainly by the facial vein. - **Pathology:** Most common site for salivary stones (sialoliths). 3. **Sublingual Salivary Gland** - **Type:** Smallest, most diffuse, and only unencapsulated major salivary gland. - **Secretions:** Mixed, predominately mucous (10% of total salivary volume). - **Location:** Sublingual fossa in the sublingual space at the floor of the mouth, deep to the sublingual fold, anterior to the submandibular gland. - **Ducts:** Ducts of Rivinus (8-20 small ducts) open along the sublingual fold; sometimes form a larger Bartholin duct opening at the sublingual caruncle. - **Innervation:** Same as submandibular gland: efferent (parasympathetic) fibers of the chorda tympani nerve (facial nerve) and submandibular ganglion. Postganglionic fibers delivered by the lingual nerve (mandibular division of trigeminal nerve). - **Lymphatic Drainage:** Submandibular lymph nodes. - **Blood Supply:** Sublingual artery (off lingual artery); parallel venous return. ##### Minor Salivary Glands - **Type:** More numerous than major glands, unencapsulated. - **Secretions:** Mainly mucous, except von Ebner glands (serous only). - **Location:** Scattered throughout oral mucosa (buccal, labial, lingual, soft palate, posterior hard palate, floor of mouth). Von Ebner glands associated with circumvallate lingual papillae. - **Ducts:** Single, short ducts directly into the oral cavity. - **Innervation:** Preganglionic from facial nerve, postganglionic from various branches of the trigeminal nerve. - **Lymphatic Drainage & Blood Supply:** Various nodes and arteries depending on location. - **Pathology:** Mucocele (blockage of duct from trauma). #### Thyroid Gland - **Type:** Largest endocrine gland (ductless). - **Secretions:** Thyroxine (hormone) directly into the vascular system to stimulate metabolic rate. - **Location:** Anterolateral regions of the neck, inferior to the thyroid cartilage, at the junction of the larynx and trachea. - **Innervation:** Sympathetic nerves through cervical ganglia (do not control secretion; pituitary gland regulates hormone release). - **Lymphatic Drainage:** Superior deep cervical lymph nodes. - **Blood Supply:** Superior and inferior thyroid arteries (possibly thyroid ima artery); venous return via superior, middle, and inferior thyroid veins. - **Pathology:** Goiter (enlarged thyroid gland), loss of mobility indicating neoplastic growth. #### Parathyroid Glands - **Type:** Usually four small endocrine glands (ductless). - **Secretions:** Parathyroid hormone directly into the vascular system to regulate calcium and phosphorus levels. - **Location:** Adjacent to or within the thyroid gland on its posterior surface (not visible or palpable). - **Innervation:** Same as thyroid gland: sympathetic nerves through cervical ganglia. - **Lymphatic Drainage:** Superior deep cervical lymph nodes. - **Blood Supply:** Primarily inferior thyroid arteries (possibly anastomotic branch between inferior and superior thyroid arteries); venous return via superior, middle, and inferior thyroid veins. #### Thymus Gland - **Type:** Endocrine gland (ductless) and part of the immune system. - **Function:** T-cell lymphocytes mature here. Grows until puberty, then shrinks (involution). - **Location:** Thorax and anterior region of the base of the neck, inferior to the thyroid gland, superficial and lateral to the trachea, deep to the sternum. - **Innervation:** Branches of the vagus nerve (tenth cranial nerve) and cervical spinal nerves. - **Lymphatic Drainage:** Lymphatic system begins within the gland and terminates in the internal jugular vein (no afferent vessels). - **Blood Supply:** Inferior thyroid and internal thoracic arteries; venous return via veins in the posterior surface directly into brachiocephalic veins. - **Pathology:** Thymic rests (ectopic accessory thymic tissue). ## Chapter 10: Lymphatic System ### Summary This chapter covers the lymphatic system, its components (vessels, nodes, ducts, tonsils), and its role in fighting disease. It details the location, drainage patterns, and clinical significance of lymph nodes and tonsils in the head and neck. ### Key Information #### Lymphatic System Overview - **Components:** Vessels, nodes, ducts, tonsils. - **Function:** Part of the immune system, fights infection and cancer, drains tissue fluid (lymph). - **Lymphatic Vessels:** Parallel venous blood vessels, have one-way valves, drain lymph. - **Lymph Nodes:** Bean-shaped bodies in clusters, filter toxic products from lymph, contain lymphocytes (white blood cells), involved in lymphocyte production. - **Afferent vessels:** Lymph flows into the node. - **Efferent vessel:** Lymph flows out of the node at the hilus. - **Primary node (regional/master node):** First node lymph drains into from a particular region. - **Secondary node (central node):** Node that primary nodes drain into. - **Lymphatic Ducts:** Larger vessels formed by converging lymphatic vessels. - **Right lymphatic duct:** Drains right side of head and neck, right arm, and thorax into the junction of the right subclavian and right internal jugular veins. - **Thoracic duct:** Drains left side of head and neck, left arm, thorax, and entire lower half of the body into the junction of the left subclavian and left internal jugular veins. - **Tonsils:** Masses of lymphoid tissue near airway and food passages, contain lymphocytes, drain into superior deep cervical lymph nodes. #### Lymph Nodes of the Head ##### Superficial Lymph Nodes of the Head - **Occipital Lymph Nodes:** - **Location:** Posterior base of the head (occipital region). - **Drainage:** Scalp in the occipital region. - **Empties into:** Deep cervical nodes. - **Posterior Auricular, Anterior Auricular, and Superficial Parotid Lymph Nodes:** - **Posterior Auricular:** Posterior to each auricle and external acoustic meatus. - **Anterior Auricular:** Immediately anterior to each tragus. - **Superficial Parotid:** Superficial to each parotid salivary gland. - **Drainage:** External ear, lacrimal gland, adjacent scalp and face. - **Empties into:** Deep cervical nodes. - **Facial Lymph Nodes:** - **Location:** Along the facial vein. - **Subgroups:** Malar (infraorbital), Nasolabial (along nasolabial sulcus), Buccal (around labial commissure), Mandibular (superior to mandible, anterior to masseter). - **Drainage:** Skin and mucous membranes where located, drain superior to inferior. - **Empties into:** Deep cervical nodes via submandibular nodes. ##### Deep Lymph Nodes of the Head - Cannot be palpated extraorally. - **Deep Parotid Lymph Nodes:** - **Location:** Deep within the parotid salivary gland. - **Drainage:** Middle ear, auditory tube, parotid salivary gland. - **Empties into:** Deep cervical nodes. - **Retropharyngeal Lymph Nodes:** - **Location:** Near deep parotid nodes, at the level of the atlas. - **Drainage:** Posterior palate, pharynx, paranasal sinuses, nasal cavity. - **Empties into:** Deep cervical nodes. #### Cervical Lymph Nodes - Paired, unilaterally drain tissues (except submental nodes, which drain bilaterally). - Categorized into superficial and deep. - Medical community uses a 7-level classification (Node Levels I-VII). ##### Superficial Cervical Lymph Nodes - **Submental Lymph Nodes (Node Level I, Sublevel a):** - **Location:** Inferior to the chin, within the submental fascial space and submental triangle. - **Drainage:** Lower lip, chin, floor of mouth, apex of tongue, mandibular incisors with periodontium and gingiva. - **Empties into:** Submandibular nodes or directly into deep cervical nodes. - **Clinical Significance:** Risk for spread of cancers from floor of mouth, apex of tongue, mandibular anterior alveolar process, lower lip. - **Submandibular Lymph Nodes (Node Level I, Sublevel b):** - **Location:** Inferior border of the mandibular ramus, superficial to the submandibular salivary gland. - **Drainage:** Cheeks, upper lip, body of tongue, anterior hard palate, most teeth (except mandibular incisors and maxillary third molars), sublingual and submandibular salivary glands. Secondary nodes for submental and facial regions. - **Empties into:** Deep cervical nodes. - **Clinical Significance:** Risk for spread of cancers from oral cavity, anterior nasal cavity, midface structures, submandibular salivary gland. - **External Jugular Lymph Nodes (Superficial Cervical Nodes):** - **Location:** Along the external jugular vein, superficial to the SCM muscle. - **Drainage:** Secondary nodes for occipital, posterior auricular, anterior auricular, and superficial parotid nodes. - **Empties into:** Deep cervical nodes. - **Anterior Jugular Lymph Nodes (Anterior Cervical Nodes):** - **Location:** Along the anterior jugular vein, anterior to larynx, trachea, superficial to SCM muscle. - **Drainage:** Infrahyoid region of the neck. - **Empties into:** Deep cervical nodes. ##### Deep Cervical Lymph Nodes - **Location:** Along the internal jugular vein, deep to the SCM muscle, from skull base to root of neck. - Divided into superior and inferior based on omohyoid muscle crossing internal jugular vein. - **Node Level II (Superior one-third):** - **Location:** From digastric muscle superiorly to hyoid bone/carotid bifurcation inferiorly. - **Drainage:** Oral cavity, nasal cavity, nasopharynx, oropharynx, laryngopharynx, larynx, parotid salivary gland. - **Jugulodigastric lymph node (tonsillar node):** Prominent node in this group, drains palatine tonsils. - **Node Level III (Middle one-third):** - **Location:** From hyoid bone/carotid bifurcation superiorly to cricothyroid notch/cricoid cartilage/omohyoid muscle inferiorly. - **Drainage:** Oral cavity, nasopharynx, oropharynx, laryngopharynx, larynx. - **Node Level IV (Inferior one-third):** - **Location:** From omohyoid muscle superiorly to clavicle inferiorly. - **Drainage:** Laryngopharynx, esophagus, larynx. - **Node Level V (Posterior cervical triangle):** - **Location:** From skull base at posterior SCM border to clavicle. - **Drainage:** Nasopharynx, oropharynx (Sublevel a), thyroid gland (Sublevel b). - **Node Level VI (Anterior compartment):** - **Location:** Inferior to hyoid bone, between medial margins of common carotid arteries. - **Drainage:** Thyroid gland, specific parts of larynx, esophagus. - **Superior Deep Cervical Lymph Nodes:** - **Location:** Deep to SCM muscle, superior to omohyoid muscle crossing internal jugular vein. - **Drainage:** Posterior nasal cavity, posterior hard palate, soft palate, base of tongue (bilateral drainage), maxillary third molars, TMJ, esophagus, trachea, thyroid gland. Secondary nodes for most other head and neck nodes. - **Empties into:** Inferior deep cervical nodes or directly into jugular trunk. - **Inferior Deep Cervical Lymph Nodes:** - **Location:** Deep to SCM muscle, inferior to omohyoid muscle crossing internal jugular vein, extending into supraclavicular fossa. - **Drainage:** Posterior scalp and neck, superficial pectoral region, part of arm. Secondary nodes for superficial head nodes and superior deep cervical nodes. - **Jugulo-omohyoid lymph node:** Drains tongue and submental triangle; enlarged node can indicate tongue carcinoma. - **Empties into:** Jugular trunk (right) or thoracic duct (left). - **Clinical Significance:** Communicates with axillary lymph nodes, high risk for spread of breast cancer. - **Accessory Lymph Nodes:** - **Location:** Along the eleventh cranial (accessory) nerve. - **Drainage:** Scalp and neck regions. - **Empties into:** Supraclavicular nodes. - **Supraclavicular Lymph Nodes:** - **Location:** Superiorly along the clavicle. - **Drainage:** Lateral cervical triangles. - **Empties into:** Jugular trunks or directly into right lymphatic duct/thoracic duct. - **Clinical Significance:** Final endpoint of lymphatic drainage from entire body, high risk for spread of cancers from lungs, esophagus, stomach. #### Tonsils - **Palatine Tonsils:** - **Location:** Oral cavity, between anterior and posterior faucial pillars. - **Lingual Tonsil:** - **Location:** Dorsal surface of the base of the tongue. - **Pharyngeal Tonsil (Adenoids):** - **Location:** Midline of the posterior wall/roof of the nasopharynx. - **Tubal Tonsil:** - **Location:** Nasopharynx, posterior to openings of the auditory tube. - **Drainage:** All tonsils drain into the superior deep cervical lymph nodes, particularly affecting the jugulodigastric lymph node if infected. #### Clinical Considerations with Lymphatic System Pathology - **Lymphadenopathy:** Dramatic increase in size and change in consistency of lymphoid tissue due to infection or cancer. - **Infection:** Nodes are slightly firmer, extremely mobile, and tender. - **Cancer:** Nodes can become bony hard, fixed to surrounding tissue, usually not tender initially (pain is a late finding). - **Lymphadenitis:** Inflammation of a lymph node, common with microbial infections. - **Metastasis:** Spread of cancer from a primary site to a secondary site via lymph. - Involvement of primary nodes offers a better prognosis than secondary nodes or lymphatic ducts. - Head and neck cancers frequently spread to cervical lymph nodes (80% of cases). - Node metastasis is a significant prognostic factor for squamous cell carcinoma survival. ### Learning Objectives Tasks: - Define and pronounce key and anatomic terms. - Locate and identify glands and associated structures on diagrams, skulls, and patients. - Discuss glandular pathology. - Integrate understanding into clinical dental practice. - List and discuss lymphatic system components. - Locate and identify lymph nodes and tonsils on diagrams and patients. - Identify lymphatic drainage patterns for the head and neck. - Describe and discuss pathology of lymphoid tissue. - Compare the relationship of the lymphatic system to the overall function of the immune system.

Exam Review Chapters 1, 2, & 3. Chapter 1 The Science of Psychology Behavior: Everything, we do that can be directly observed. Behavioral approach: an approach to psychology emphasizing the scientific study of observable behavioral responses and their environmental determinants. Biological approach: an approach to psychology focusing on the body, especially the brain and nervous system. Case study or case history: an in-depth look at a single individual. Cognitive approach: an approach to psychology emphasizing the mental processes involved in knowing: how we direct our attention, perceive, remember, think, and solve problems. Control group: The participants in an experiment who are as much like the experimental group as possible and who are treated in every way like the experimental group except for a manipulated factor, the independent variable. Correlational research: research that examines the relationships between variables, whose purpose is to examine whether and how two variables change together. Critical thinking: The process of thinking deeply and actively, asking questions, and evaluating the evidence. Dependent variable: The outcome; the factor that can change in an experiment in response to changes in the independent variable. Double-blind experiment: An experimental design in which neither the experimenter nor the participants are aware of which participants are in the experimental group and which are in the control group until the results are calculated. Evolutionary approach: An approach to psychology centered on evolutionary ideas such as adaptation, reproduction, and natural selection as the basis for explaining specific human behaviors. Experiment: A carefully regulated procedure in which the researcher manipulates one or more variables that are believed to influence some other variable. Experimental group: The participants in an experiment who receive the drug or other treatment under study—that is, those who are exposed to the change that the independent variable represents. Functionalism: James’s approach to mental processes, emphasizing the functions and purposes of the mind and behavior in the individual’s adaptation to the environment. Humanistic approach: An approach to psychology emphasizing a person’s positive qualities, the capacity for positive growth, and the freedom to choose any destiny. Hypothesis: A testable prediction that derives logically from a theory. Independent variable: A manipulated experimental factor; the variable that the experimenter changes to see what its effects are. Longitudinal design: A special kind of systematic observation, used by correlational researchers, that involves obtaining measures of the variables of interest in multiple waves over time. Mental processes: The thoughts, feelings, and motives that people experience privately but that cannot be observed directly. Natural selection: Darwin’s principle of an evolutionary process in which organisms that are best adapted to their environment will survive and produce offspring. Naturalistic observation: The observation of behavior in a real-world setting. Placebo: In a drug study, a harmless substance that has no physiological effect, given to participants in a control group so that they are treated identically to the experimental group except for the active agent. Placebo effect: The situation where participants’ expectations, rather than the experimental treatment, produce an experimental outcome. Population: The entire group about which the researcher wants to draw conclusions. Psychoanalysis: techniques involves an analyst unlocking a person's unconscious conflicts by talking with the individual about his or her childhood memories, dreams, thoughts, and feelings. Psychodynamic approach: an approach to psychology emphasizing unconscious thought, the conflict between biological drives (such as the drive for sex) and society’s demands, and early childhood family experiences. Psychology: The scientific study of behavior and mental processes. Sample: The subset of the population chosen by the investigator for study. Sociocultural approach: an approach to psychology that examines the ways in which social and cultural environments influence behavior. Structuralism: Wundt’s approach to discovering the basic elements, or structures, of mental processes. Theory: A broad idea or set of closely related ideas that attempts to explain observations and to make predictions about future observations. Validity: The soundness of the conclusions that a researcher draws from an experiment. In the realm of testing, the extent to which a test measures what it is intended to measure. Variable: Anything that can change. Wilhelm Wundt is most often regarded the "founding father" of modern psychology. He was also the founder of structuralism. William James was the founder of functionalism. J. B. Watson and B. F. Skinner believed that psychology should focus on an organism's visible interactions with the environment—that is, behaviors. Ethical Guidelines developed by the American Psychological Association include: • informed consent. • confidentiality. • deception. • debriefing. Chapter 2 The Brain and Behavior Action potential: The brief wave of positive electrical charge that sweeps down the axon. Adrenal glands: glands at the top of each kidney that are responsible for regulating moods, energy level, and the ability to cope with stress. Amygdala: An almond-shaped structure within the base of the temporal lobe that is involved in the discrimination of objects that are necessary for the organism’s survival, such as appropriate food, mates, and social rivals. Association cortex: Sometimes called association areas, the region of the cerebral cortex that is the site of the highest intellectual functions, such as thinking and problem solving. Autonomic nervous system: The body system that takes messages to and from the body’s internal organs, monitoring such processes as breathing, heart rate, and digestion. Axon The part of the neuron that carries information away from the cell body toward other cells. Basal ganglia Large neuron clusters located above the thalamus and under the cerebral cortex that work with the cerebellum and the cerebral cortex to control and coordinate voluntary movements. Brain stem The stem like brain area that includes much of the hindbrain (excluding the cerebellum) and the midbrain; connects with the spinal cord at its lower end and then extends upward to encase the reticular formation in the midbrain. Cell body The part of the neuron that contains the nucleus, which directs the manufacture of substances that the neuron needs for growth and maintenance. Central nervous system (CNS): The brain and spinal cord. Cerebral cortex: Part of the forebrain, the outer layer of the brain, responsible for the most complex mental functions, such as thinking and planning. Chromosomes: In the human cell, threadlike structures that come in 23 pairs, one member of each pair originating from each parent, and that contain DNA. Corpus callosum: The large bundle of axons that connects the brain’s two hemispheres, responsible for relaying information between the two sides. Dendrites: Treelike fibers projecting from a neuron, which receive information and orient it toward the neuron’s cell body. Deoxyribonucleic acid (DNA): A complex molecule in the cell’s chromosomes that carries genetic information. Dominant-recessive genes principle: The principle that if one gene of a pair is dominant and one is recessive, the dominant gene overrides the recessive gene. A recessive gene exerts its influence only if both genes of a pair are recessive. Endocrine system: The body system consisting of a set of glands that regulate the activities of certain organs by releasing their chemical products into the bloodstream. Forebrain: The brain’s largest division and its most forward part. Frontal lobes: The portion of the cerebral cortex behind the forehead, involved in personality, intelligence, and the control of voluntary muscles. Genes: The units of hereditary information, consisting of short segments of chromosomes composed of DNA. Genotype: An individual’s genetic heritage; his or her actual genetic material. Glands: Organs or tissues in the body that create chemicals that control many bodily functions. Glial cells: The second of two types of cells in the nervous system; glial cells (also called glia) provide support, nutritional benefits, and other functions and keep neurons running smoothly. Hindbrain: Located at the skull’s rear, the lowest portion of the brain, consisting of the medulla, cerebellum, and pons. Hippocampus: The structure in the limbic system that has a special role in the storage of memories. Hormones: Chemical messengers that are produced by the endocrine glands and carried by the bloodstream to all parts of the body. Hypothalamus: A small forebrain structure, located just below the thalamus, that monitors three pleasurable activities—eating, drinking, and sex—as well as emotion, stress, and reward. Limbic system: A set of subcortical brain structures central to emotion, memory, and reward processing. Midbrain: Located between the hindbrain and forebrain, an area in which many nerve-fiber systems ascend and descend to connect the higher and lower portions of the brain; in particular, the midbrain relays information between the brain and the eyes and ears. Motor cortex: A region in the cerebral cortex, located just behind the frontal lobes, that processes information about voluntary movement. Myelin sheath: A layer of fat cells that encases and insulates most axons. Neocortex: The outermost part of the cerebral cortex, making up 80 percent of the human brain’s cortex. Nervous system: The body’s electrochemical communication circuitry. Neural networks: Networks of nerve cells that integrate sensory input and motor output. Neurons: One of two types of cells in the nervous system; neurons are the nerve cells that handle the information-processing function. Neurotransmitters: Chemical substances that are stored in very tiny sacs within the neuron’s terminal buttons and involved in transmitting information across a synaptic gap to the next neuron. Occipital lobes: Structures located at the back of the head that respond to visual stimuli. Ovaries: Sex-related endocrine glands that produce hormones involved in women’s sexual development and reproduction. Pancreas: A dual-purpose gland under the stomach that performs both digestive and endocrine functions. Parasympathetic nervous system: The part of the autonomic nervous system that calms the body. Parietal lobes: Structures at the top and toward the rear of the head that are involved in registering spatial location, attention, and motor control. Peripheral nervous system (PNS): The network of nerves that connects the brain and spinal cord to other parts of the body. Phenotype: An individual’s observable characteristics. Pituitary gland: A pea-sized gland just beneath the hypothalamus that controls growth and regulates other glands. Plasticity: The brain’s special capacity for change. Prefrontal cortex: an important part of the frontal lobes that is involved in higher cognitive functions such as planning, reasoning, and self-control. Resting potential, The stable, negative charge of an inactive neuron. Reticular formation: A system in the midbrain comprising a diffuse collection of neurons involved in stereotyped patterns of behavior such as walking, sleeping, and turning to attend to a sudden noise. Somatic nervous system: The body system consisting of the sensory nerves, whose function is to convey information from the skin and muscles to the central nervous system about conditions such as pain and temperature, and the motor nerves, whose function is to tell muscles what to do. Somatosensory cortex: A region in the cerebral cortex that processes information about body sensations, located at the front of the parietal lobes. Stem cells: Unique primitive cells that have the capacity to develop into most types of human cells. Stress: The responses of individuals to environmental stressors. Stressors: Circumstances and events that threaten individuals and tax their coping abilities and that cause physiological changes to ready the body to handle the assault of stress. Sympathetic nervous system: The part of the autonomic nervous system that arouses the body to mobilize it for action and thus is involved in the experience of stress. Synapses: Tiny spaces between neurons; the gaps between neurons are referred to as synaptic gaps. Temporal lobes: Structures in the cerebral cortex that are located just above the ears and are involved in hearing, language processing, and memory. Testes: Sex-related endocrine glands in the scrotum that produce hormones involved in men’s sexual development and reproduction. Thalamus: The forebrain structure that sits at the top of the brain stem in the brain’s central core and serves as an important relay station. Left Hemisphere • verbal processing, speech, grammar Right Hemisphere • spatial perception • visual recognition • emotion Chapter 3 Sensation and Perception Absolute threshold: The minimum amount of stimulus energy that a person can detect. Apparent movement: The perception that a stationary object is moving. Auditory nerve: The nerve structure that receives information about sound from the hair cells of the inner ear and carries these neural impulses to the brain’s auditory areas. Binding: In the sense of vision, the bringing together and integration of what is processed by different neural pathways or cells. Binocular cues: Depth cues that depend on the combination of the images in the left and right eyes and on the way the two eyes work together. Bottom-up processing: The operation in sensation and perception in which sensory receptors register information about the external environment and send it up to the brain for interpretation. Cones: The receptor cells in the retina that allow for color perception. Convergence: A binocular cue to depth and distance in which the muscle movements in an individual’s two eyes provide information about how deep and/or far away something is. Depth perception: The ability to perceive objects three-dimensionally. Difference threshold: The degree of difference that must exist between two stimuli before the difference is detected. Feature detectors: Neurons in the brain’s visual system that respond to particular features of a stimulus. Figure-ground relationship: The principle by which we organize the perceptual field into stimuli that stand out (figure) and those that are left over (ground). Frequency theory: Theory on how the inner ear registers the frequency of sound, stating that the perception of a sound’s frequency depends on how often the auditory nerve fires. Gestalt psychology A school of thought interested in how people naturally organize their perceptions according to certain patterns. Inner ear: The part of the ear that includes the oval window, cochlea, and basilar membrane and whose function is to convert sound waves into neural impulses and send them to the brain. Kinesthetic senses: Senses that provide information about movement, posture, and orientation. Middle ear: The part of the ear that channels and amplifies sound through the eardrum, hammer, anvil, and stirrup to the inner ear. Monocular cues: Powerful depth cues available from the image in one eye, either the right or the left. Noise: Irrelevant and competing stimuli—not only sounds but also any distracting stimuli for the senses. Olfactory epithelium: The lining of the roof of the nasal cavity, containing a sheet of receptor cells for smell. Opponent-process theory: Theory stating that cells in the visual system respond to complementary pairs of red-green and blue-yellow colors; a given cell might be excited by red and inhibited by green, whereas another cell might be excited by yellow and inhibited by blue. Optic nerve: The structure at the back of the eye, made up of axons of the ganglion cells, that carries visual information to the brain for further processing. Outer ear: The outermost part of the ear, consisting of the pinna and the external auditory canal. Pain: The sensation that warns an individual of damage to the body. Papillae: Rounded bumps above the tongue’s surface that contain the taste buds, the receptors for taste. parallel processing: The simultaneous distribution of information across different neural pathways. Perception: The process of organizing and interpreting sensory information so that it makes sense. perceptual constancy: The recognition that objects are constant and unchanging even though sensory input about them is changing. perceptual set A predisposition or readiness to perceive something in a particular way. place theory: Theory on how the inner ear registers the frequency of sound, stating that each frequency produces vibrations at a particular spot on the basilar membrane. retina The multilayered light-sensitive surface in the eye that records electromagnetic energy and converts it to neural impulses for processing in the brain. Rods: The receptor cells in the retina that are sensitive to light but not very useful for color vision. selective attention: The act of focusing on a specific aspect of experience while ignoring others. semicircular canals: Three fluid-filled circular tubes in the inner ear containing the sensory receptors that detect head motion caused when an individual tilts or moves the head and/or the body. Sensation: The process of receiving stimulus energies from the external environment and transforming those energies into neural energy. sensory adaptation: A change in the responsiveness of the sensory system based on the average level of surrounding stimulation. sensory receptors: Specialized cells that detect stimulus information and transmit it to sensory (afferent) nerves and the brain. signal detection theory: An approach to perception that focuses on decision making about stimuli in the presence of uncertainty. subliminal perception The detection of information below the level of conscious awareness. Thermoreceptors: Sensory nerve endings under the skin that respond to changes in temperature at or near the skin and provide input to keep the body’s temperature at 98.6 degrees Fahrenheit. top-down processing The operation in sensation and perception, launched by cognitive processing at the brain’s higher levels, that allows the organism to sense what is happening and to apply that framework to information from the world. trichromatic theory: Theory stating that color perception is produced by three types of cone receptors in the retina that are particularly sensitive to different, but overlapping, ranges of wavelengths. vestibular sense: Sense that provides information about balance and movement. visual cortex: Located in the occipital lobe, the part of the cerebral cortex involved in vision. volley principle: Principle addressing limitations of the frequency theory of hearing, stating that a cluster of nerve cells can fire neural impulses in rapid succession, producing a volley of impulses. Weber’s law: The principle that two stimuli must differ by a constant minimum percentage (rather than a constant amount) to be perceived as different.