Midterm Two PDF - Nervous System

11.1 Overview of the Nervous System Nervous System Controls our perception and experience of the world Directs voluntary movement Consciousness, personality, learning, and memory Works with other systems to maintain homeostasis, including regulating respiratory rate, blood pressure, body...

11.1 Overview of the Nervous System Nervous System Controls our perception and experience of the world Directs voluntary movement Consciousness, personality, learning, and memory Works with other systems to maintain homeostasis, including regulating respiratory rate, blood pressure, body temperature, the sleep/wake cycle, and blood pH Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.1 Structural Divisions of the Nervous System (1 of 3) Central Nervous System Figure 11.1 Structure of the (CNS) nervous system. – Brain – Spinal cord Peripheral Nervous System (PNS) – Cranial nerves – Spinal nerves and their branches Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.1 Structural Divisions of the Nervous System (2 of 3) Central Nervous System Brain—Composed of about 100 billion cells called neurons or nerves cells that regulate all body functions Spinal Cord—Contains about 100 million neurons – Merges with the brain at the foramen magnum and passes through the vertebral foramen of the first cervical vertebra; continues to the first or second lumbar vertebra – Enables the brain to communicate with the body below the head and neck; carries out some functions on its own Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.1 Structural Divisions of the Nervous System (3 of 3) Peripheral Nervous System Nerves—Consist of bundles of long neuron axons or “arms” packed with blood vessels and surrounded by connective tissue sheaths. Carry signals to and from the CNS; – Cranial Nerves—Originating from or traveling to the brain; 12 pairs – Spinal Nerves— Originating from or traveling to the spinal cord; 31 pairs Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.1 Functional Divisions of the Nervous System Sensory Input Functions—Involve Done by the sensory division gathering information about the internal and external (afferent) Division of the PNS environments of the body Integrative Functions— Analyze and interpret the detected sensory stimuli Done by the CNS (mostly by the brain) and determine an appropriate response Motor Output Functions— Done by the motor division (efferent) Actions performed in Division of the PNS; remember the response to integrations Motor Efferent division moves ME Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.1 Functional Divisions of the Nervous System Figure 11.2 Functions of the nervous system. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.1 Functional Divisions of the Nervous System Figure 11.3 Summary of the structural and functional divisions of the nervous system. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.1 Functional Divisions of the Nervous System PNS Sensory Division Sensory stimuli detected by Sensory Receptors; – Somatic Sensory Division (related to the body/ voluntary)—Neurons carry signals from skeletal muscles, bones, joints, and skin; includes sensory neurons from the organs for vision, hearing, taste, smell, and balance – Visceral Sensory Division (related to internal organs/involuntary)—Neurons carry signals from viscera (organs) such as the heart, lungs, stomach, intestines, kidneys, and urinary bladder Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.1 Functional Divisions of the Nervous System CNS Neurons of the CNS integrate many types of sensory input to form a complete picture After integration, the CNS disregards about 99% of data that is considered unimportant However, if the CNS does respond, it generally leads to a motor response Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.1 Functional Divisions of the Nervous System PNS Motor Division Neurons carry out motor functions such as muscle contractions and secretion from glands; organs that carry out the effects are Effectors – Somatic Motor Division—Neurons transmit signals to skeletal muscles (voluntary) – Visceral Motor Division (Autonomic Nervous System)—Neurons carry signals to thoracic and abdominal viscera; regulates secretion from some glands, controls smooth muscle and cardiac muscle in the heart (involuntary) Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved  11.2 Nervous Tissue Figure 11.4 Neuron Nervous Tissue—About 80% of nervous tissue volume is cells with about 20% extracellular matrix Neurons—Excitable cell type Neuroglial cells (glial cells)—Smaller and more prevalent cells which generally do not transmit signals but serve a variety of supportive functions (support, nutrient supply, immune response, insulation, etc.) – Outnumber neurons by 10:1 Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.2 Neurons Neurons—Send and receive signals in the form of action potential; responsible for sensory, integrative, and motor functions of the nervous system Long-lived cells; however, they are generally amitotic; lose the ability to divide at a certain point in development Most neurons have a central body (soma), where most of the cell’s organelles are housed, one or more dendrites, which carry electrical signals to the cell body, and one axon that generally carries electrical signals away from the cell body Figure 11.5 Neuron structure. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.2 Neurons Cell Body (Soma) most metabolically active part of the neuron; maintains a large cytoplasmic volume and manufactures proteins Free Ribosomes and Rough Endoplasmic Reticulum, Golgi Apparatus and one or more prominent Nucleoli are present. Mitochondria are found in large numbers Neuronal Cytoskeleton is composed of many intermediate filaments bundled into neurofibrils that extend into the dendrites and axon and microtubules that support the cell and allow transport of chemicals Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.2 Neurons Processes: Dendrites and Axons—Allow the neuron to communicate with other cells Dendrites—Typically short, highly forked processes resembling branches of a tree limb – Receive input from other neurons and transmit it in the form of electrical impulses toward the cell body – Possess most of the same organelles as the cell body – Dendrites can grow and are “pruned” as a person matures and the demands on the nervous system change Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved  11.2 Neurons Processes: Dendrites and Axons (continued) Axons (Nerve Fiber)—Processes that can generate and conduct action potentials – Axon Hillock—Area of the cell body where the axon arises – Axon Collaterals—Branches of the axon – Telodendria—Fine branches of axon and its collaterals – Axon Terminals (Synaptic Knobs)— Ends of telodendria that communicate with target cells; Neurons typically have 1,000 or more – Axolemma—Plasma membrane of the axon – Axoplasm—Cytoplasm of the axon; Axonal Transport (Flow)—Substances travel through the axoplasm toward or away from the cell body Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.2 Neurons Functional Regions of Neurons—Each neuron has three main functional regions Receptive Region—Dendrites and cell body receive signals Conducting Region—Axon continues the signal Secretory Region—Secrete chemicals for target cells Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.2 Neurons Structural Classification of Neurons Multipolar Neurons—Over 99% of neurons; single axon with multiple highly branched dendrites; wide variety of shapes and sizes Bipolar Neurons—One axon and one dendrite; most are sensory; found in the retina of the eye and olfactory epithelium Pseudounipolar Neurons—Single axon with one half that brings sensory stimuli to the cell body (peripheral process or axon) and the other half that carries stimuli to the spinal cord (central process or axon); found in your sensory receptors (detect touch, pressure, and pain) Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.2 Neurons Functional Classification of Neurons Sensory (Afferent) Neurons—Carry signals toward the CNS and facilitate motor coordination – pseudounipolar or bipolar Interneurons (Association Neurons)—Relay messages within the CNS; vast majority of neurons – multipolar Motor (Efferent) Neurons—Carry signals away from the CNS to muscles and glands; – multipolar Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.2 Neurons Table 11.1 Neuron Classification Structural Multipolar Neurons Bipolar Neurons Pseudounipolar Neurons Class Structural One axon with two or more dendrites; One axon and one Single short process that Features typically have highly branched dendrite splits into two axons (no dendritic tree A schematic illustration depicts the structure of a special sensory neuron as a bipolar neuron. A bipolar neuron is composed of a cell body, a vertically upward extending dendrite, and a vertically downward extending axon. dendrites) A schematic illustration depicts the structural features of the following multipolar neurons: Spinal motor neuron, Pyramidal cell, and Purkinje cell. A schematic illustration depicts the structure of a general sensory neuron as a pseudounipolar neuron. Long description 1 is available in notes, press F6. Long description 2 is available in notes, press F6. Typical Motor (efferent) neurons, interneurons Sensory (afferent) Sensory (afferent) neurons Functional neurons Class Location Most neurons in the CNS, motor Special sense organs in Sensory neurons in the PNS neurons in the PNS the PNS, such as the associated with touch, pain, retina and olfactory and vibration sensations epithelium Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.2 Neuroglia Neuroglia (Neuroglial Cells/Glial cells) Hold neurons together Maintain the environment around neurons Protect neurons and assist in their functions Can undergo mitosis and will fill in gaps when neurons die Six different types of neuroglia are found in the nervous system; – Astrocytes, Oligodendrocytes, Microglia, Ependymal cells in the PNS – Schwann cells, Satellite cells in the CNS Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.2 Neuroglia Neuroglia in the CNS—Ten times more abundant in the CNS than neurons; about half the mass of the brain 1. Astrocytes.—Numerous star-shaped cells; Most abundant; have several functions: – Anchoring neurons and blood vessels in place ▪ Facilitate transport of nutrients and gases from the blood vessels to neurons – Regulate the extracellular environment of the brain ▪ Remove excess extracellular potassium ions and neurotransmitters – Assisting in the formation of the blood brain barrier ▪ separates blood from the extracellular fluid, ensuring selective transport of substances between the fluids – Repairing damaged brain tissue ▪ Divide rapidly, but may impede regrowth of neurons, leading to more damage Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.2 Gliomas and Astrocytomas Primary Brain Tumors—Originate within the brain Gliomas—Most common type; caused by an abnormally high rate of cellular division in neuroglial cells Exposure to ionizing radiation and certain diseases such as Neurofibromatosis, a genetic condition, predispose patients to gliomas, although the cause is often unknown Astrocytomas—Most common type of glioma Range in severity from mild tumors with a good prognosis to highly aggressive tumors with a very poor prognosis Surgical removal followed by chemotherapeutic drugs and perhaps radiation are common treatments Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.2 Neuroglia Neuroglia in the CNS (continued) 2. Oligodendrocytes—Have radiating processes with flattened ends that wrap around part of the axons of certain neurons; form concentric layers of plasma membrane collectively called Myelin; repeating segments of myelin form the Myelin Sheath, which increases the speed of nerve impulse conduction 3. Microglia—Tiny, branching cells that are activated by brain injury; become wandering phagocytes that ingest disease-causing organisms, dead neurons, and cell debris, and stimulate inflammation 4. Ependymal Cells—Ciliated cells with many functions; one main function is circulating cerebrospinal fluid, which is the fluid in the cavities of the brain and spinal cord; some ependymal cells form the fluid, others monitor its composition Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.2 Neuroglia Figure 11.6 Neuroglial cells of the CNS. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.2 Neuroglia Neuroglia in the PNS 1. Neurolemmocytes (Schwann cells)—Encase axons of neurons in the PNS; cover some of those axons in a myelin sheath; play a role in the repair of damaged axons 2. Satellite Cells—Enclose and support the cell bodies and link with other parts of the neuron, other satellite cells, and neighboring neurolemmocytes; regulate the extracellular environment around the cell body Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.2 The Myelin Sheath Myelin Sheath—Formed by Neurolemmocytes (Schwann Cells) and Oligodendrocytes that wrap themselves around the axons of some neurons; repeating layers of plasma membrane Myelin is composed of glycolipids, lipids, protein and cholesterol unique to the cells that produce it Coats the cells and prevents the movement of ions, which makes it an excellent insulator, similar to the rubber tubing around a copper wire Myelinated axons conduct action potentials about 15–150 times faster than unmyelinated axons Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.2 The Myelin Sheath Myelination—The process of sheath formation; segments of an axon covered by myelin are Internodes; Spaces between internodes are Myelin Sheath Gaps or Nodes of Ranvier In the PNS, a Neurolemmocyte wraps itself outward, away from the axon in successively tighter bands; up to 100 layers thick – Cytoplasm and organelles are on the outer surface of a myelinated axon, called a Neurolemma – Encircle a portion of a single axon only – Myelination begins during the early fetal period In the CNS, the arms of an Oligodendrocyte wrap inward, toward the axon – Nucleus and cytoplasm are in a central location – May send out multiple processes to envelop parts of several axons – Myelination begins much later, particularly in the brain; in fact, newborns have very little myelin in the brain Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.2 The Myelin Sheath Figure 11.8a The myelin sheath in the PNS and CNS. Short axons are almost always unmyelinated Myelin appears lighter (called White Matter) than unmyelinated areas (called Gray Matter) in the CNS Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.2 Regeneration of Nervous Tissue (1 of 3) Regeneration—Replacement of damaged tissue; limited in humans regarding nervous tissue CNS—Dendrites and axons almost never regenerate – Oligodendrocytes inhibit neuronal growth; growth factors are absent; astrocytes create scar tissue PNS—Neural tissue is capable of regeneration if the cell body remains intact and the conditions are ideal; repair occurs through the following sequence of events: Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.2 Regeneration of Nervous Tissue (2 of 3) Regeneration PNS 1) The axon and myelin sheath distal to the injury degenerate ▪ Phagocytes digest the debris 2) Growth processes form from the proximal end of the axon 3) Neurolemmocytes and the basal lamina form a regeneration tube 4) A single growth process grows into the regeneration tube ▪ Neurolemmocytes secrete growth factors 5) The axon is reconnected with the target cell Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.2 Regeneration of Nervous Tissue (3 of 3) Figure 11.10 Repair of axon damage in the PNS. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.3 Propagation of Action Potentials Conduction Speed—The rate at which propagation occurs; determines how rapidly signaling can occur within the nervous system; influenced by 1) Diameter of the Axon—Larger axons have lower resistance to conduction, allowing current to flow through them more easily 2) Presence or Absence of a Myelin Sheath If there is no myelin sheath, unmyelinated Conduction occurs (slower) If the myelin sheath is present, myelinated Conduction occurs (faster) Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.3 Propagation of Action Potentials Figure 11.16 Comparison of saltatory and continuous conduction. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.3 Propagation of Action Potentials Conduction Speed (continued) Continuous Conduction—Each section of the axolemma must be depolarized to threshold for the action potentials to move down the length of the axon Saltatory Conduction—The myelin sheath gaps are the only segments that must be depolarized to threshold – Gaps with voltage-gated sodium ion channels are depolarized to threshold and the action potential current flows through the internode to the next gap – Another action potential is generated and the cycle repeats by “jumping” from one gap to the next Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.3 Concept Boost: How Does Myelin Insulate an Axon and Increase Its Speed of Propagation? (1 of 2) Myelin “insulates” an axon to enable saltatory conduction Consider the basic principles of electricity Electric current will flow down a bare copper wire to illuminate the light bulb (left), but if you touch the wire with a metal probe, the current might flow down the probe (right) causing a short circuit Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 11.3 Concept Boost: How Does Myelin Insulate an Axon and Increase Its Speed of Propagation? (2 of 2) If the wire is encased in a non-conducting material, the current is unable to move away from the copper wire Unmyelinated axons are similar to uninsulated wires; the axolemma is leaky and current flows to the ECF so the current has to be continuously regenerated The signal in a myelinated axon propagates without having to be regenerated Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved Human Anatomy and Physiology BIOL3306 Fall 2024 Week 5: The Central Nervous System Professor: Nour Nissan Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.1 Overview of CNS Functions Functions of the Nervous System: 1) Sensory Input Functions—Detection of sensations within and outside the body 2) Integrative Functions—“Decision-Making” processes 3) Motor Output Functions—Stimulation of muscle cell contractions or gland secretions Sensory and motor functions are performed by the peripheral nervous system (PNS) Integrative functions are carried out exclusively by the central nervous system (CNS) Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.1 Basic Structure of the Brain and Spinal Cord Brain—Soft, whitish-gray organ that resides in the cranial cavity; Consists of four divisions Composed of nervous tissue with some connective and modified epithelial tissue Internal cavities called ventricles; filled with protective cerebrospinal fluid (CSF) Weighs between 1,250–1,450 g; slightly larger in males; Ratio of brain weight to body weight of females is equal to that of males During rest, about 20% of total blood flow in the body goes to the brain Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.1 Basic Structure of the Brain and Spinal Cord Brain (continued) Cerebrum—Enlarged, superior portion; composed of the right and left hemisphere – Responsible for higher mental functions, including learning, memory, personality, cognition (thinking), language, and conscience; major role in sensation and movement Diencephalon—Central core; composed of four parts – Responsible for processing, integrating, and relaying information; maintaining homeostasis of physiological variables, regulation of movement, biological rhythms Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.1 Basic Structure of the Brain and Spinal Cord Brain (continued) Cerebellum—Posterior, inferior portion; composed of right and left hemispheres – Important in planning and coordination of movement, particularly for complex activities such as sports or playing an instrument Brainstem—Connects the brain and spinal cord – Controls basic involuntary processes such as rate and depth of breathing, mediates certain reflexes, monitors movement; integrates and relays information to other parts of the nervous system Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.1 Basic Structure of the Brain and Spinal Cord Spinal Cord—Long, tubular organ encased within the vertebral cavity Begins at the foramen magnum, where it blends with the brainstem, ends approximately between the first and second lumbar vertebrae Central canal is filled with CSF and is continuous with the ventricles of the brain Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.1 Basic Structure of the Brain and Spinal Cord Figure 12.1 Divisions of the brain (lateral view). Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved  12.1 Basic Structure of the Brain and Spinal Cord White Matter—Contains myelinated axons Gray Matter—Contains unmyelinated axons Brain—Gray matter makes up the outer few millimeters and is scattered throughout in deeper portions; Spinal Cord—Gray matter is internal and tracts of white matter are superficial Figure 12.2 White and gray matter in the CNS. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved  12.2 The Cerebrum Figure 12.4 Structure of the cerebrum. The cerebral cortex: outer layer of the cerebrum, composed of grey matter. About 2-4mm thick. Lobes of the Cerebral Hemispheres Frontal Lobes Parietal Lobes Temporal Lobes Occipital Lobes Insulas—Visible when you pry the frontal, parietal, and temporal lobes apart (mnemonic is “the insula is insulated by the other lobes”) Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved  12.2 The Cerebrum Figure 12.6 Structure of the basal nuclei (anterolateral Gray Matter: Basal Nuclei view). Basal Nuclei—Clusters of cells bodies buried in the cerebral hemispheres; Basal nuclei inhibit involuntary movement and initiate voluntary movement; – globus pallidus: prevents upper motor neurons from causing spontaneous, inappropriate muscle contractions; – caudate nucleus and putamen: inhibit the globus pallidus to begin movement Also, disorders of the basal nuclei cause problems with behavior, cognition, and perception Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.2 The Cerebrum Cerebral White Matter Commissural Fibers—Connect right and left cerebral hemispheres; largest of the four groups of fibers makes up the corpus callosum Projection Fibers—Connect cerebral cortex of one hemisphere with other areas of the hemisphere and other areas of the brain and spinal cord; form a radiating pattern called the Corona Radiata; condense to form V-shaped bands known as internal capsule Association Figure 12.7 Fibers—Restricted Structure of to a single cerebral white matter. hemisphere and connect gray matter of cortical gyri (area) with one another Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved  12.2 The Cerebrum Figure 12.9 Structures of the limbic system (anterolateral view). Hippocampus—Greek word for Limbic System—Includes the “seahorse”; connected to a C-shaped ring Limbic Lobe, the Hippocampus, of white matter called the Fornix. Mainly Amygdala, and diencephalon involved in memory, spatial navigation and Found only in mammals; learning. participates in memory, learning, Amygdala—Greek word for “almond”; emotion, and behavior; called the anterior to the hippocampus; functions in “visceral brain” behavioral expression of emotion, particularly fear Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved  12.2 The Diencephalon Figure 12.10 Structure of the diencephalon. Diencephalon—Found at the center of the brain; structurally and functionally has four components: Large, central Thalamus Posterior and superior Epithalamus Inferior Hypothalamus Subthalamus Thalamus—Consists of two large, egg- shaped masses of gray matter; Makes up about 80% of the diencephalon; Receive afferent fibers from cerebral cortex, cerebellum, basal nuclei, other structures of the limbic system, sensory system; Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved  12.2 The Diencephalon Hypothalamus—Anterior and inferior to the thalamus; weighs about 4 g; makes up less than 1% of brain mass Nuclei perform several functions vital to survival Receives sensory input from outside and within the body, such as level of light, blood pressure, body temperature, concentration of body fluids, blood glucose concentration Regulates sleep/wake cycle, causes thirst and hunger, adjusts body temperature Figure 12.13 Nuclei of the hypothalamus. “Boss” of the autonomic nervous system (ANS) Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved  12.2 The Cerebellum Figure 12.14 Structure of the cerebellum. Cerebellum—Posterior and inferior portion of the brain; composed of two Cerebellar Hemispheres connected by the vermis Functions with cerebral cortex, basal nuclei, brainstem, and spinal cord to reduce motor errors Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved  12.2 The Brainstem Figure 12.15 External anatomy of the brainstem. Brainstem—Control basic functions including maintenance of heart rate and breathing rhythm Mediates Reflexes, which are programmed, automatic responses to stimuli, and functions in movement, sensation, and maintaining alertness Includes a superior superior midbrain, a middle pons, and an inferior medulla oblongota Also houses a large group of connected nuclei called the Reticular Formation Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.2 Putting It All Together: The Big Picture of Major Brain Structures and Their Functions Figure 12.18 The Big Picture of Brain Anatomy Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.2 Putting It All Together: The Big Picture of Major Brain Structures and Their Functions Figure 12.19 The Big Picture of Major Brain Structures and Their Functions Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.2 Putting It All Together: The Big Picture of Major Brain Structures and Their Functions Figure 12.19 The Big Picture of Major Brain Structures and Their Functions (continued) Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.3 Sleep and Wakefulness Circadian Rhythms and the “Biological Clock” Circadian Rhythm—Spend a period of the 24-hour cycle awake and another period of the cycle asleep Controlled by the hypothalamic Suprachiasmatic Nucleus (SCN) or “biological clock” – Food intake, movement, hormones, and most importantly, the level of light influence the rate of firing – Process of sleep induction involves decreasing activity in brain areas that promote wakefulness Being awake is mediated by the Lateral Hypothalamic Area or “on switch”; secrete orexin, which helps maintain wakefulness during the day; orexin deficiency may be the cause of Narcolepsy Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.3 Sleep and Wakefulness Figure 12.20 The process of falling asleep. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.4 Cognition and Language Cerebral Lateralization—Cognitive functions are unequally represented in the right and left hemispheres; represents a division of labor, but is not absolute: Emotional Functions—Left frontal cortex responsible for “positive” emotions, such as happiness; right frontal cortex responsible for “negative” emotions, such as anger Attention—Right parietal cortex Facial Recognition—Right temporal cortex Language-Related Recognition—Includes ability to identify an object with its proper name; lateralized to the left temporal cortex Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.4 Cognition and Language Language—Ability to comprehend and produce words through speaking, writing, and/or signing, and to assign and recognize the symbolic meaning of a work correctly Involves syntax (arrangement of words and phrases to create sentences), grammar, and context Correct understanding also relies on cues such as tone, volume, and the speaker’s body language Broca area - In the frontal lobe; responsible for the production of language, including the planning and ordering of words with proper grammar and syntax Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.4 Cognition and Language Language (continued) Wernicke's area —In the temporal lobe; responsible for understanding language and linking a word with its correct symbolic meaning Damage to either area results in a language deficit called aphasia Most language functions reside in the left hemisphere in about 97% of people; damage to the language areas of the right hemisphere results in loss of emotional and tonal components of language Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved  Bruce Willis Aphasia In 2022, Actor Bruce Willis was diagnosed with frontotemporal dementia. Currently, there are no treatments and life expectancy averages seven to 13 years after the onset of symptoms Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved Dr. Jill Bolte Taylor My stroke of insight – Dr. Jill Bolte Taylor Dr. Jill Bolte Taylor is a Harvard-trained and published neuroscientist. In 1996 she experienced a severe hemorrhage (AVM) in the left hemisphere of her brain causing her to lose the ability to walk, talk, read, write, or recall any of her life. 06:20- https://www.ted.com/talks/jill_bolte_taylor_my_stroke_of_insight Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.4 Learning and Memory Learn—Acquiring new information that is observable as some sort of behavioral change Memory—Information is encoded and stored in neural circuitry and is retrievable at will Declarative (Fact) Memory—Memory of things that are readily available to consciousness that could in principle be expressed aloud; such as a phone number or quote Nondeclarative (Skills) Memory—Includes skills and associations that are largely unconscious; such as how to enter a phone number on a phone Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.4 Learning and Memory Memory (continued) Immediate Memory—Stored for a few seconds; important in conversation, reading, and daily tasks Short-Term (Working) Memory—Stored for several minutes Long-Term Memory—More permanent form of storage for days, weeks, or even a lifetime Some information is transferred into long-term memory by Consolidation, but much is forgotten and the process is often flawed, resulting in incorrect memories Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.4 Learning and Memory Figure 12.23 Pathways for consolidation of memories. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.5 Protection of the Brain Brain is soft, and its neurons can be damaged by slight pressure; housed within the cranial cavity, which protects it from trauma, movement, and temperature changes Inside the skull, three features add protection: – Meninges —Set of three protective membranes that surround the brain – CSF - Protective fluid that bathes the brain and fills its cavities – BBB —Prevents many substances in the blood from gaining access to brain cells Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved  12.5 Cranial Meninges Figure 12.24 Structure of the cranial meninges and dural sinuses. Cranial Meninges— Made primarily of dense irregular connective tissue Dura Mater—Or simply Dura; Outermost layer; thickest and toughest Arachnoid Mater— Or simply Arachnoid; middle layer Pia Mater—Or simply Pia; innermost layer Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved Infectious Meningitis Infectious Meningitis—Potentially life-threatening infection that leads to inflammation of the meninges Classic signs include headache, lethargy, stiff neck, and fever Diagnosed by examining a sample of CSF for infectious agents and white blood cells Viral Meningitis—Generally mild and resolves in 1–2 weeks Bacterial Meningitis—Can rapidly progress to brain involvement and death without aggressive antibiotic treatment; many forms are preventable with vaccines Fungal Meningitis—Often occurs in immunocompromised individuals, can be severe, and requires long-term antifungal treatment; not typically contagious and can be challenging to treat. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.5 The Blood Brain Barrier (1 of 2) Blood Brain Barrier (BBB)—Consists of simple squamous epithelial (endothelial) cells of the blood capillaries in the brain, their basal laminae, and foot processes of astrocytes; cells are unique: They have more tight junctions than cells of most capillaries—Tight junctions are cell-cell junctions that prevent water and other substances from passing through the spaces between cells They limit endocytosis and exocytosis—Endothelial cells of the blood brain barrier have a very limited ability to perform these processes compared to other capillary cells Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.5 The Blood Brain Barrier (2 of 2) Blood Brain Barrier (continued) Plasma membrane is generally freely permeable to certain substances, such as water, oxygen, carbon dioxide, and nonpolar, lipid-based compounds Substances with channels or carriers, such as glucose, amino acids, and ions, also cross easily Large, polar molecules are effectively prevented from crossing in significant amounts; does prevent many toxins and organisms from crossing, but also prevents many therapeutic drugs, such as most antibiotics, from entering the brain Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.5 Concept Boost: Where Exactly Is the Blood Brain Barrier? (1 of 2) Blood brain barrier isn’t around the brain; it’s within the brain and not in one distinct location, but is found throughout the entire brain Capillaries are the tiniest blood vessels in the body; they deliver oxygen and nutrients to the body’s cells and remove any wastes produced by the cells Capillaries in most organs and tissues are somewhat leaky and allow many substances to move from the blood to the ECF (and vice versa) Brain capillaries are specialized to only allow selected substances to enter the ECF, so they act as a “barrier” Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.5 Concept Boost: Where Exactly Is the Blood Brain Barrier? (2 of 2) Blood brain barrier is actually a property of the capillaries found throughout the brain rather than a distinct physical barrier Figure 12.27 The blood brain barrier. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.6 The Spinal Cord Spinal Cord—Composed of nervous tissue; two roles: Relay Station—Only means by which the brain can communicate with most of the body below the head and neck; receives outgoing stimuli from the brain and sends them to the rest of the body; receives incoming stimuli from the body and sends them to the brain Processing Station—Does some integration and processing functions; certain activities called Spinal Reflexes, can be carried out by the spinal cord alone, without influence from the brain Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.6 Protection of the Spinal Cord Spinal Meninges—Include the Dura, Arachnoid, and Pia Mater; similar to those of the brain Three Actual or Potential Spaces: Epidural Space—Between the meningeal dura and the walls of the vertebrae; filled with veins and adipose tissue that cushions and protects the spinal cord Subdural Space—Potential space; normally the dura and arachnoid adhere to each other Subarachnoid Space—Between the arachnoid and pia; filled with a very thin layer of CSF; area inferior to the base of the spinal cord contains a larger volume of CSF; useful for CSF sampling if needed Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.6 Protection of the Spinal Cord Figure 12.28 Structure of the spinal meninges. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 12.6 Epidural Anesthesia and Lumbar Punctures Epidural or Spinal Anesthesia—A local anesthetic medication is injected into the epidural space through an inserted needle Causes “numbing” of the nerves extending off the spinal cord below the level of the injection, meaning they are unable to transmit motor or sensory impulses Commonly given to women during childbirth and to both sexes during certain surgical procedures Lumbar Puncture (Spinal Tap)—Needle is inserted into the subarachnoid space and CSF is withdrawn for analysis Inserted between the fourth and fifth vertebrae to avoid injury to the spinal cord Performed to assess for conditions including meningitis, encephalitis, and multiple sclerosis Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved Human Anatomy and Physiology BIOL3306 Fall 2024 Week 8: The Peripheral Nervous System Professor: Nour Nissan Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.1 Overview of the Peripheral Nervous System Peripheral Nervous System (PNS)—Links the CNS with the body and the external environment PNS detects sensory stimuli and delivers them to the CNS as sensory input CNS processes the input and transmits the impulses through the PNS to effectors (muscle cells and glands) for motor output – Spinal Nerves and Cranial Nerves belong to the PNS even though they attach to the spinal cord and brain directly Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.1 Divisions of the PNS (1 of 4) Peripheral Nervous System (PNS) Sensory (Afferent) Division – Somatic Sensory Division (refers to “body”) – Visceral Sensory Division (refers to “internal organs”) Motor (Efferent) Division – Somatic Motor Division – Visceral Motor Division (The Autonomic Nervous System (ANS) is more commonly used) ▪ Sympathetic Nervous System: ▪ Parasympathetic Nervous System: Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.1 Divisions of the PNS (3 of 4) Motor Division Visceral Motor Division (Autonomic Nervous System)— Motor neurons carry signals to the cardiac and smooth muscles and glands – Sympathetic Nervous System—Described as the flight or fight – Parasympathetic Nervous System—Described as the rest and digest Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.1 Divisions of the PNS (4 of 4) Figure 13.1 The organization of the peripheral nervous system. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.1 Functional Overview of the PNS 1. Sensory neurons detect stimuli at sensory receptors 2. Stimuli are transmitted through sensory neurons via spinal or cranial nerves to sensory neurons of the CNS 3. CNS transmits impulses to the cerebral cortex for interpretation and integration 4. Appropriate motor response is initiated by motor areas of the brain to upper motor neurons (found in the brain) 5. Impulses travel to the spinal cord through local interneurons (relay messages in the CNS) then lower motor neurons (which attach to muscles) of the PNS 6. Impulses go to appropriate tissue to trigger a response Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.1 Overview of Peripheral Nerves and Associated Ganglia (1 of 3) Peripheral Nerves (or just Nerves)—Axons of many neurons bound together by a common connective tissue sheath Innervate most of the structures of the body Most are Mixed Nerves and contain sensory and motor axons Some are Sensory and only have sensory axons – Ex. Optic nerve Some are Motor and have mostly motor axons with a few sensory axons that monitor muscle stretch and tension – Ex. Hypoglossal nerve (M) , Vagus (B) Cranial Nerves—Attach to the brain; Innervate structures of the head and neck Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.1 Overview of Peripheral Nerves and Associated Ganglia (2 of 3) Spinal Nerves—Thirty-one pairs of mixed nerves branch from the spinal cord; Innervate structures inferior to the neck Anterior Root—Axons of motor (efferent) neurons Posterior Root—Axons of sensory (afferent) neurons Figure 13.2a The structure of roots and spinal nerves. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.2 The Cranial Nerves (1 of 20) Study Boost: Remembering the Cranial Nerves Sequentially: Oh (I, Olfactory) Very (VIII, Vestibulocochlear) Once (II, Optic) Good (IX, Glossopharyngeal) One (III, Oculomotor) Vacations (X, Vagus) Takes (IV, Trochlear) Are (XI, Accessory) The (V, Trigeminal) Happening (XII, Hypoglossal) Anatomy (VI, Abducens) Final (VII, Facial) Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.2 The Cranial Nerves (2 of 20) Study Boost: Remembering the Cranial Nerves By Functions: S=Sensory, M=Motor, B=Both (Mixed) Some (I, Olfactory-S) Says (VIII, Vestibulocochlear-S) Say (II, Optic-S) Big (IX, Glossopharyngeal-B) Marry (III, Oculomotor-M) Brains (X, Vagus-B) Money (IV, Trochlear-M) Matter (XI, Accessory-M) But (V, Trigeminal-B) More (XII, Hypoglossal-M) My (VI, Abducens-M) Brother (VII, Facial-B) Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.2 The Cranial Nerves (3 of 20) Figure 13.3 Overview of cranial nerves. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.2 The Cranial Nerves (4 of 20) Sensory Only (3): Motor (5): Olfactory (I) Oculomotor (III) Optic (II) Trochlear (IV) Vestibulocochlear (VIII) Abducens (VI) Accessory (XI) Mixed/both (4): Hypoglossal (XII) Trigeminal (V) Facial (VII) Glossopharyngeal (IX) Vagus (X) Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.2 The Cranial Nerves (5 of 20) Table 13.1 The Sensory Cranial Nerves Nerve Origin, Course, Function and Destination Olfactory nerve (I) Open brace Roman numeral one close brace Origin: Originates from the The nerve for (ohl-FAK-toh-ree) unmyelinated axons of neurons olfaction whose cell bodies are located in the (olfact- = “smell”), olfactory epithelium in the roof of the or the sense of A schematic illustration shows a lateral view of the nasal cavity and frontal regions of the brain demonstrating the origin of the olfactory nerves Roman numeral 1. Long description is available in notes, press F6. nasal cavity. smell. Its nerve Course: The axons form bundles that endings contain penetrate the holes in the cribriform chemoreceptors plate of the ethmoid bone, and end in that depolarize in the bulbous olfactory bulb (shown to response to the left) on the inferior surface of the chemicals in the brain’s frontal lobe. The olfactory bulb air we breathe. continues posteriorly as the olfactory These stimuli are tract. interpreted in the brain by the Destination: The olfactory tract primary olfactory terminates in the medial temporal cortex. lobe and structures of the limbic system, including the limbic cortex, the hippocampus, and the amygdala. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.2 The Cranial Nerves (6 of 20) Table 13.1 The Sensory Cranial Nerves Nerve Origin, Course, Function and Destination Optic nerve (II) Open brace Roman numeral two close brace Origin: Originates from myelinated The nerve for axons of neurons in the posterior vision (opt- = eyeball. “vision”). It A schematic illustration shows an inferior view of the brain demonstrating the origin of the optic nerves (Roman numeral 2). Long description is available in notes, press F6. Course: As shown to the left, the two transmits visual optic nerves meet and form an “X” stimuli in the form called the optic chiasma (ky-AZ- of action muh), where some of the axons potentials decussate (switch sides). triggered when light hits the eye’s Destination: Axons from the optic photoreceptors. chiasma are destined for structures These stimuli are such as the lateral geniculate nucleus processed in the of the thalamus, the midbrain, and brain by the ultimately the primary visual cortex in primary visual the occipital lobe. cortex. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.2 The Cranial Nerves (7 of 20) Table 13.1 The Sensory Cranial Nerves Nerve Origin, Course, Function and Destination Vestibulocochlear nerve (VIII) Open brace Roman numeral Eight close brace Origin: Actually two separate Vestibular nerve: Its (ves-tib′-yoo-loh-KOHK-lee-ur) nerves, the vestibular and neurons depolarize in cochlear, which originate in the response to body inner ear and share a common position. This allows A schematic illustration shows a lateral view of the inner ear demonstrating the origin of the vestibulocochlear nerve (Roman numeral 8). Long description is available in notes, press F6. epineurium. them to assist with the Courses: Fibers from the maintenance of balance vestibular and cochlear nerves and equilibrium. fuse shortly after they leave the Cochlear nerve: Its temporal bone to become the neurons depolarize in vestibulocochlear nerve. response to sound Destination of vestibular nerve: waves and are Axons terminate in the responsible for audition cerebellum and in nuclei in the (aw-DIH-shun; aud- = medulla oblongata. “hear” ), or the sense of Destination of cochlear nerve: hearing. Axons travel to the medulla oblongata and terminate in auditory cochlear areas. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.2 The Cranial Nerves (8 of 20) Table 13.2 The Motor Cranial Nerves Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.2 The Cranial Nerves (9 of 20) Table 13.2 The Motor Cranial Nerves Nerve Origin and Function Destination Oculomotor Origin: Contains axons of both somatic motor neurons and visceral motor nerve (III) Open brace Roman numeral three closed brace Arises from neurons of the parasympathetic nervous system, and has the following (awk′-yoo- the superior four primary functions: loh-MOH- and lateral Moving the eyeball. As shown above, the somatic motor axons ter) portion of innervate four of the six extrinsic eye muscles that move the eyeball: the the medial rectus, superior rectus, inferior rectus, and inferior oblique midbrain. muscles. These muscles move our eyes medially, superiorly, inferiorly, Destination: and superolaterally, respectively. Extrinsic Opening the eye. Other somatic motor axons innervate the levator eye muscles palpebrae superioris muscle, which opens the eyelid. and smooth Constricting the pupil. The parasympathetic axons innervate a muscles of muscle surrounding the pupil called the sphincter pupillae muscle. These the eye axons stimulate this muscle to contract, which constricts the pupil and (oculo- = limits the light entering the eye. (Pupil dilation is mediated by a different “eye”). nerve.) Changing the lens shape. The thickness of the lens (which focuses light on the photoreceptors in the posterior eyeball) is controlled by the ciliary muscle. This muscle is innervated by parasympathetic axons, which stimulate the ciliary muscle to contract, making the lens rounder for near vision. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.2 The Cranial Nerves (10 of 20) Table 13.2 The Motor Cranial Nerves Nerve Origin and Destination Function Trochlear Origin: Originates from the inferior portion of the As shown above, the somatic motor nerve (IV) Open brace Roman numeral four close brace midbrain. It’s named for the cartilaginous trochlea neurons innervate the superior (TROHK- through which the tendon of the superior oblique oblique muscle (a common lee-ur) muscle passes. mnemonic is “ SO4 , ” as it is cranial SO sub 4 Destination: Superior oblique muscle of the eye. nerve IV ), which moves the eye Roman numeral four medially and inferiorly. Abducens Origin: The cell bodies of the abducens nerve are The somatic motor neurons nerve (VI) Open brace Roman numeral six close brace located in the pons. innervate the lateral rectus muscle. (ab-DOO- Destination: Lateral rectus muscle of the eye. Its name comes from the fact that senz) this muscle abducts the gaze when it turns the eye laterally. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.2 The Cranial Nerves (11 of 20) Table 13.2 The Motor Cranial Nerves Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.2 The Cranial Nerves (12 of 20) Table 13.2 The Motor Cranial Nerves Nerve Origin and Destination Function Accessory Origin: Unique in that its origin has both a cranial The cranial component of nerve (XI) Open brace Roman numeral eleven close brace component from the medulla and a spinal component from the accessory nerve the cervical spinal cord. The somatic motor neurons of the innervates certain spinal component travel superiorly and enter the cranial muscles of speech, cavity through the foramen magnum, after which they whereas the spinal merge with the somatic motor neurons of the cranial component innervates component. As shown above, the two travel together for muscles that move the only a short distance, after which they diverge. head and shoulder. Cranial Destination: The cranial component accompanies the vagus nerve (covered in Table 13.3) and innervates some muscles of the larynx. Spinal Destination: The spinal component turns inferiorly and exits the cranial cavity to innervate the trapezius and sternocleidomastoid muscles of the neck and shoulders. Hypoglossal Origin: Arises from the inferiormost part of the medulla This motor nerve nerve (XII) Open brace Roman numeral Twelve close brace (see above). innervates the muscles of Destination: As its name suggests (hypo- = “below,” the tongue—it plays no glosso- = “tongue”), its destination is inferior to the tongue. role in taste sensation. It innervates most of the intrinsic and extrinsic tongue muscles. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.2 The Cranial Nerves (13 of 20) Table 13.3 The Mixed Cranial Nerves Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.2 The Cranial Nerves (14 of 20) Table 13.3 The Mixed Cranial Nerves Nerve Origin, Course, Sensory Function Function and Destination Trigeminal (V) Open brace Roman numeral five close brace Origin: The motor portion The sensory root detects facial sensation, Ophthalmic (try JEM-ih-nul) originates at the midbrain and including stimuli from the oral and nasal nerve: No motor pons junction, and the sensory cavities. function. portion from sensory receptors Ophthalmic nerve: Its somatic sensory Maxillary nerve: around the face. axons supply the area shaded blue in the No motor Course: A short distance from illustration above, which includes the skin function. its origin is the large, bulbous over much of the scalp, the forehead, Mandibular trigeminal ganglion, which around the eyes, and over the anterior nose; nerve: Shown houses the cell bodies of its they also supply the nasal mucosa and above, its motor sensory neurons. Anterior to this structures of the eye. axons supply the ganglion, it splits into three masseter and Maxillary nerve: As shown above, its branches (tri- = “three”): the temporalis somatic sensory axons supply the area ophthalmic (awf-THAL-mik), muscles, which shaded orange, which includes the skin over maxillary, and mandibular elevate the the middle of the face. nerves. mandible (close Mandibular nerve: The sensory axons of the jaw) during Destinations: All three branches the inferior mandibular nerve supply the mastication have sensory fibers that area shaded green above, which includes (chewing) and terminate in the primary the skin of the chin and the lateral part of swallowing. somatosensory cortex. The the face. mandibular nerve has motor fibers that terminate at the Facial sensation + 2/3 of the tongue muscles of mastication. What you feel on your face: pain or touch Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.2 The Cranial Nerves (15 of 20) Table 13.3 The Mixed Cranial Nerves Nerve Origin, Course, Sensory Function Function and Destination Facial nerve Open brace Roman numeral seven close brace Origin: As shown in the The sensory root provides The somatic motor (VII) illustrations on the next the following: neurons of the five page, the motor portion (or taste sensation from branches of the motor root motor root ) originates in chemoreceptors in supply the muscles of nuclei in the pons and specialized receptor cells facial expression and other medulla, and the sensory in the anterior two-thirds facial muscles. portion (or sensory root ) of the tongue; and from the tongue, external somatic sensation from ear, palate, and nasal cavity. the external ear, palate, Course: Several ganglia and nasal cavity. house cell bodies of the facial nerve’s sensory root; the largest is called the geniculate ganglion (jen-IK yoo-lit; geni- = “knee” ). Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.2 The Cranial Nerves (16 of 20) Table 13.3 The Mixed Cranial Nerves Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.2 The Cranial Nerves (18 of 20) Table 13.3 The Mixed Cranial Nerves Nerve Origin, Course, Sensory Function Function and Destination Glossopharyngeal Origin: The motor The sensory portion of this nerve The motor branches of nerve (IX) Open brace Roman numeral nine close brace neurons originate in detects sensation as follows: this nerve supply a (gloss′-oh-fah-RINjee-ul) nuclei in the medulla; the The chemoreceptors of the muscle around the sensory neurons posterior one-third of the tongue are pharynx that is originate in the tongue, associated with special sensory responsible for pharynx, around the ear, axons of this nerve. The cell bodies swallowing movements. and in blood vessels of of these neurons are in the inferior Also, parasympathetic the neck. ganglion. neurons trigger Course: The cell bodies A small branch of this nerve salivation from a salivary of its sensory neurons contains somatic sensory neurons gland called the parotid are located in two that innervate the external ear gland. You can feel this ganglia: the superior alongside the facial nerve. It also stimulation and ganglion and the inferior contains visceral sensory neurons subsequent salivation in ganglion. that provide sensation for the your cheeks when you Destination: Its location posterior pharynx and surrounding eat very salty or acidic and the structures it structures. In addition, some visceral foods such as pickles or innervates are reflected neurons detect changes in blood lemons. in its name—recall that pressure via receptors in the carotid glosso- means “tongue” artery of the neck. and pharynx means “throat.” Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.2 The Cranial Nerves (19 of 20) Table 13.3 The Mixed Cranial Nerves Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.2 The Cranial Nerves (20 of 20) Table 13.3 The Mixed Cranial Nerves Nerve Origin, Course, Sensory Function Function and Destination Vagus nerve (X) Open brace Roman numeral ten close brace Origin: The motor neurons The somatic sensory The somatic motor fibers (VAY-guss) originate from the brain at the neurons serve the skin supply the muscles medulla. The sensory neurons around the ear. The special surrounding the pharynx originate around the tongue, sensory neurons convey and larynx (the “voice pharynx, skin of the ear, and taste sensation from the box”) that contract during certain blood vessels of the neck. pharynx, and the visceral speaking and swallowing. Course: As shown above, cell sensory neurons detect We continue our bodies of its sensory neurons are sensation in the mucous discussion of the visceral housed in the superior ganglion membranes of the pharynx. innervation of this nerve in and the inferior ganglion. This nerve also contains the ANS chapter (see visceral sensory neurons Chapter 14). Destination: It’s the main whose chemoreceptors parasympathetic nerve, and the detect the blood CO2 most widely distributed nerve in concentration. the body (see above). It innervates both the throat and anterior neck, and nearly all the thoracic and abdominal viscera. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved https://youtu.be/FtJtYMRVw7A?si=ezZlr9O3Z1LUFHQm Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.3 Structure of Spinal Nerves and Spinal Nerve Plexuses (1 of 4) Anterior root (Ventral root) - carries Efferent information away from the spinal cord. Only contains axons of motor (efferent) neurons Posterior root (Dorsal root) – taking afferent information to the spinal cord. Only contains axons of sensory (afferent) neurons The roots are separate Spinal nerve trunk is what joins the roots and the rami Spinal nerves leave the vertebral cavity and split into 2 nerves (rami). Contain both sensory and motor neurons: Posterior (Dorsal) Ramus—Travels to posterior (back) side of the body (deep back muscles) Anterior (Ventral) Ramus—Travels to anterior(front) side of the body and/or the limbs Figure 13.4a Structure and function of roots, spinal nerves, and rami. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.3 Structure of Spinal Nerves and Spinal Nerve Plexuses (2 of 4) Ramus Communicans Figure 13.4b Structure and function of roots, spinal nerves, and rami. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved  13.3 Structure of Spinal Nerves and Spinal Nerve Plexuses (3 of 4) There are 31 pairs of Spinal Nerves: –.. pairs of Cervical nerves (C1-C8 ) –.... pairs of Thoracic nerves (T1-T12 ) –.. pairs of Lumbar nerves (L1-L5 ) –.. pairs of Sacral nerves (S1-S5 ) –.. pair of Coccygeal nerves (Co1 ) Nerves that shoot out and away merge to form complicated networks of nerves called Nerve Plexuses before they branch out again; Muscles are served by 2 or more different spinal nerves Figure 13.5 Overview of spinal nerves Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.3 Cervical Plexuses (1 of 2) Right and left.................................. Consist mostly of anterior rami of (C1-C4 ) with some contributions from (C5 ) and the Hypoglossal nerve Supply sensory branches to the skin of the neck, portions of the head, chest, and shoulders Major motor branch is the................. Nerve, with axons from (C3 -C5 ), which supplies the diaphragm muscle that drives ventilation (C3, C4, C5 keep us alive) Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.3 Cervical Plexuses (2 of 2) Figure 13.6 The cervical plexus Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.3 Brachial Plexuses (1 of 6) Right and left Brachial Plexuses—Originate from anterior of spinal nerves C5 -T1 Provide sensory and motor innervation to the arm Major Nerves of the Brachial Plexuses Radial Nerve—Continuation of posterior cord; Innervates posterior arm and forearm, posterior thumb, posterior 2nd, 3rd, and lateral half of 4th digits; Median Nerve—From fusion of lateral and medial cords; Innervates anterior thumb and anterior 2nd, 3rd, and lateral side of 4th digits Ulnar Nerve—Continuation of medial cord; Innervates 5th digit and medial half of 4th digit Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.3 Brachial Plexuses (6 of 6) Figure 13.7b The brachial plexus. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.3 Lumbar Plexuses (1 of 3) Right and left................. Plexuses—Lie anterior to vertebrae, Supply structures of the pelvis and lower extremity Arise from anterior rami of L1 -L4 Posterior Division—Largest nerve is..................... Nerve – Hip flexion and knee extension Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.3 Lumbar Plexuses (3 of 3) Figure 13.8b The lumbar plexus. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.3 Sacral Plexuses (1 of 4) Right and left Sacral Plexuses—Inferior to the lumbar plexuses against the posterior pelvic wall; Supply structures of the pelvis and gluteal region and much of the lower extremity Arise from anterior rami of L4 -S4 Largest nerve in the body is................ Nerve. – Innervates gluteus maximus , back of thigh, and lower leg and foot. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.3 Sacral Plexuses (4 of 4) Figure 13.9b The sacral plexus. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 13.3 A Hiccups Cure That Really Works Hiccups are caused by spasms of the diaphragm muscle that cause a forceful inhalation of air Using your fingers, apply and hold firm pressure to the muscles of the neck that overlie the Phrenic nerve (1 centimeter lateral to the vertebrae on both sides of the middle of the neck) (as illustrated on right) Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved Human Anatomy and Physiology BIOL3306 Fall 2024 Week 8: The Autonomic Nervous System Professor: Nour Nissan Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 14.1 Functions of the Autonomic Nervous System and Reflex Arcs (1 of 2) Autonomic Nervous System (ANS)—Oversees vital functions such as heart rate, blood pressure, and digestive and urinary functions, without conscious control, through Visceral Reflex Arcs 1) Sensory signals from viscera and skin are sent by afferent sensory neurons to the brain or spinal cord 2) Stimuli are integrated by the CNS 3) Motor impulses from the CNS are sent via efferent motor neurons in cranial and spinal nerves to autonomic ganglia 4) Autonomic ganglia send impulses via other efferent motor neurons to target organs, where they trigger a motor response in the target cells Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 14.1 Functions of the Autonomic Nervous System and Reflex Arcs (2 of 2) Figure 14.1 Visceral reflex arcs. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 14.1 Comparison of Somatic and Autonomic Nervous Systems (1 of 2) PNS Motor Division Somatic Motor Division—Somatic motor neurons directly innervate skeletal muscle fibers; voluntary control; acetylcholine (ACh); excitatory Visceral Motor Division (ANS) —Autonomic motor neurons innervate smooth and cardiac muscle cells, and glands; involuntary control; two neurons involved – Preganglionic Neuron—Cell body in the CNS; synapses on the cell body of postganglionic neuron – Postganglionic Neuron—Cell body in the PNS autonomic ganglion; axon synapses on the target cell; often ACh and norepinephrine; excitatory and inhibitory Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 14.1 Comparison of Somatic and Autonomic Nervous Systems (2 of 2) Figure 14.2 Comparison of the somatic and autonomic nervous systems. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 14.1 Divisions of the ANS (1 of 4) Autonomic Nervous System Divisions Sympathetic Nervous System—Preganglionic axons are often................. and postganglionic axons are.................. Parasympathetic Nervous System—Opposite is true Figure 14.3 Overview of the structure of ANS divisions. Copyright © 2025, 2019, 2016 Pearson Education, Inc. All Rights Reserved 14.1 Divisions of the ANS (2 of 4) Sympathetic Nervous System—“Fight or Flight” Cell bodies of preganglionic neurons originate in thoracic and upper lumber spinal cord (............................ Division) Sympathetic ganglia are generally near the....................... Parasympathetic Nervous System—“Rest and Digest” Cell bodies of preganglionic neurons are located within nuclei of