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PowerPoint® Lecture Slides prepared by Betsy C. Brantley Valencia College CHAPTER 7 The Central Nervous System © 2013 Pearson Education, Inc. Chapter 7 Learning Outcomes • Section 1: Neurons and Neuroglia • 7.1 • Sketch, label, and describe the structures of a typical neuron, and classify and describe neurons on the basis of their structure and function. • 7.2 • Identify the types of neuroglia in the CNS and describe their locations and functions. • 7.3 • Describe the locations and functions of Schwann cells and satellite cells of the PNS and classify and describe the three functional classes of neurons. © 2013 Pearson Education, Inc. Chapter 7 Learning Outcomes • 7.4 • Describe the membrane potential and summarize its role in neural activity. • 7.5 • Compare continuous propagation and saltatory propagation, and discuss the factors that affect the speed of action potential propagation. • 7.6 • Describe the general structure of a synapse and summarize the events that occur when an action potential arrives at an axon terminal. © 2013 Pearson Education, Inc. Chapter 7 Learning Outcomes • Section 2: The Functional Anatomy of the Central Nervous System • 7.7 • Name and locate the major regions of the brain, and describe their functions. • 7.8 • Describe the cranial meninges and explain how cerebrospinal fluid forms and circulates. • 7.9 • Name and locate the major superficial landmarks of the cerebrum. • 7.10 • Locate the motor, sensory, and association areas of the cerebral cortex, and discuss the functions of each. © 2013 Pearson Education, Inc. Chapter 7 Learning Outcomes • 7.11 • Explain the structure and functions of the diencephalon, brain stem, and cerebellum. • 7.12 • Describe the reticular formation and explain the functions of the reticular activating system. • 7.13 • CLINICAL MODULE Describe how brain waves are monitored, and explain the normal and clinical significance of various brain waves seen on an electroencephalogram. • 7.14 • Discuss the anatomical features of the spinal cord. © 2013 Pearson Education, Inc. Chapter 7 Learning Outcomes • 7.15 • Explain the roles of gray matter and white matter in processing and relaying sensory information and motor commands. • 7.16 • Describe the spinal meninges. © 2013 Pearson Education, Inc. Nervous System Organization (Section 1) • Central Nervous System (CNS) • Brain and spinal cord • Integrates, processes, and coordinates sensory data and motor commands • Peripheral Nervous System (PNS) • All neural tissue outside CNS • Sensory (afferent) division • Motor (efferent) division © 2013 Pearson Education, Inc. Sensory Division of the PNS (Section 1) • Brings information to CNS from receptors • Somatic sensory receptors • Provide sensation of touch, position, pressure, pain, temperature • Visceral sensory receptors • Monitor internal organs • Special sensory receptors • Provide sensations of smell, taste, vision, balance, hearing © 2013 Pearson Education, Inc. Motor Division of the PNS (Section 1) • Carries motor commands from CNS to target organs called effectors • Somatic nervous system (SNS) • Carries messages to skeletal muscle • Autonomic nervous system (ANS) • Carries messages to: • Smooth muscle • Cardiac muscle • Glands • Adipose tissue © 2013 Pearson Education, Inc. Major components and functions of the nervous system Central Nervous System 3 Information processing Peripheral Nervous System 4 Motor (efferent) division includes 2 Sensory (afferent) division Somatic sensory receptors Special sensory receptors Somatic nervous system Autonomic nervous system Skeletal muscle Visceral sensory receptors Start 1 Receptors © 2013 Pearson Education, Inc. 5 Effectors • Smooth muscle • Cardiac muscle • Glands • Adipose tissue Figure 7 Section 1 1 Structural Features of Neurons (7.1) • Dendrites • Receive stimuli from environment or other neurons • Short and highly branched • Cell body • Contains nucleus and other organelles • Cytoskeleton contains filaments that extend into dendrites and axon • Axon • Carries information away from cell body toward other cells © 2013 Pearson Education, Inc. Axon Details (7.1) • Axon hillock • Expanded section adjacent to cell body where axon begins • Axon collaterals or branches • Axon terminal • End of axon adjacent to synapse • Synapse where neuron communicates with another cell • Presynaptic cell and postsynaptic cell on either side • Transport of materials through neurotubules © 2013 Pearson Education, Inc. Structural features of neurons Axon Dendrites Axon hillock Axon collaterals Axon terminal Nissl bodies Mitochondrion Nucleus Axon terminal Presynaptic cell Nucleolus Synapse Postsynaptic cell Cell Body Cytoplasm (contains organelles) © 2013 Pearson Education, Inc. Cytoskeleton (contains filaments) Figure 7.1 11 Structural Variations among Neurons (7.1) • Bipolar neurons • Have two processes (dendritic process and axon) • Found in special sense organs between receptors and other neurons • Unipolar neurons • Fused dendrite and axon • Most sensory neurons are unipolar • Multipolar neurons • Two or more dendrites and single axon • Most common neurons in CNS and all motor neurons controlling skeletal muscles © 2013 Pearson Education, Inc. Structural variations among neurons Dendrites Dendritic process Bipolar neuron Dendrites Initial segment Axon Cell body Axon Axon Axon terminals Dendrites Multipolar neuron Axon terminals Axon Axon terminals © 2013 Pearson Education, Inc. Unipolar neuron Figure 7.1 22- 4– 4 Neural Stem Cells (7.1) • Exist in adult nervous system, but inactive except in: • Olfactory epithelium (sensory neurons for smell) • Retina of eye • Hippocampus (part of brain involved in short-term memory storage) • Most CNS neurons cannot divide or be replaced after injury or disease © 2013 Pearson Education, Inc. Module 7.1 Review a. Name the structural components of a typical neuron. b. Classify neurons according to their structure. c. Why is a CNS neuron not usually replaced after it is injured? © 2013 Pearson Education, Inc. Neuroglia of the CNS (7.2) • Cells that support and protect neurons are called neuroglia or glial cells • Account for half the volume of the nervous system • Four types in CNS 1. Astrocytes 2. Ependymal cells 3. Microglia 4. Oligodendrocytes © 2013 Pearson Education, Inc. Neuroglia of the CNS Details (7.2) • Ependymal cells • Form ependyma, epithelium lining fluid-filled passageways in spinal cord and brain • Produce, monitor, and circulate cerebrospinal fluid (CSF) • Microglia • Related to monocytes and macrophages • Mobile cells roaming through neural tissue • Remove cellular debris, waste products, and pathogens © 2013 Pearson Education, Inc. Neuroglia of the CNS Details (7.2) • Astrocytes • Maintain blood–brain barrier • Provide structural support and regulate ion, nutrient, and dissolved gas concentrations in interstitial fluid • Absorb and recycle neurotransmitters • Form scar tissue • Oligodendrocytes • Produce myelin © 2013 Pearson Education, Inc. Myelination in CNS (7.2) • Oligodendrocyte process winds around axon forming concentric layers of lipid-rich material called myelin sheath • Myelinated axons have myelin sheath • Sections of axon wrapped called internodes • Gaps between internodes called nodes • Regions in CNS with myelinated axons are white matter • Unmyelinated axons not completely covered by myelin • Regions of CNS with cell bodies and unmyelinated axons are gray matter © 2013 Pearson Education, Inc. Neuroglia of the central nervous system Astrocytes Oligodendrocytes Internode of myelinated axon Capillary Section of spinal cord Ependymal cells Nodes between internodes Unmyelinated axon Microglia Neurons Gray matter © 2013 Pearson Education, Inc. Myelinated axons Myelin (cut) Nodes White matter Figure 7.2 Module 7.2 Review a. Identify the neuroglia of the central nervous system. b. Which glial cell protects the CNS from chemicals and hormones circulating in the blood? c. Which type of neuroglia would occur in increased numbers in the brain tissue of a person with a CNS infection? © 2013 Pearson Education, Inc. Schwann Cells and Satellite Cells (7.3) • In the PNS, the myelin sheath is formed by Schwann cells • Outer surface of Schwann cell is neurilemma • Single Schwann cell forms myelin sheath around one internode of one myelinated axon • Schwann cell can enclose parts of unmyelinated axons stabilizing axon position and isolating axon from interstitial fluid • Satellite cells surround cell bodies in PNS • Clusters of cell bodies called ganglia © 2013 Pearson Education, Inc. Schwann cells and peripheral axons Nucleus Axon hillock Internode (myelinated) Satellite cells Cell body Dendrite Node Schwann cell nucleus Schwann Axon cell Neurilemma Neurilemma Schwann cell Schwann cell nucleus Neurilemma Axons Schwann cell #1 Schwann cell #2 Myelin covering internode Axon Schwann cell #3 nucleus Axons © 2013 Pearson Education, Inc. Figure 7.3 11- 3– 3 Three Functional Classes of Neurons (7.3) 1. Sensory neurons • About 10 million 2. Interneurons • About 20 billion 3. Motor neurons • About half a million © 2013 Pearson Education, Inc. Sensory Neurons (7.3) • Unipolar neurons • Cell bodies in sensory ganglia • Deliver information from receptors to CNS along afferent fibers • Somatic sensory neurons • External receptors detect changes in external environment • Proprioceptors monitor body position and movement • Visceral sensory neurons • Internal receptors monitor internal conditions © 2013 Pearson Education, Inc. Interneurons (7.3) • Receive sensory information from PNS and from other interneurons in CNS • Responsible for memory, planning, and learning © 2013 Pearson Education, Inc. Motor Neurons (7.3) • Carry information from CNS to effectors along efferent fibers • Somatic motor neurons • Innervate skeletal muscle under voluntary control • Cell bodies in CNS • Axon within peripheral nerve to somatic effectors • Visceral motor neurons • Innervate smooth muscle, glands, cardiac muscle, adipose tissue • Communicate with second visceral motor neuron in peripheral autonomic ganglia © 2013 Pearson Education, Inc. Functional classes of neurons Central Nervous System (CNS) Interneurons Visceral motor neurons Somatic motor neurons cell bodies Peripheral Nervous System (PNS) Autonomic ganglia Sensory ganglia Afferent fibers Efferent fibers Somatic effectors Skeletal muscle fibers Internal receptors Proprioceptors Start Sensory receptors © 2013 Pearson Education, Inc. External receptors KEY = Somatic (sensory & motor) = Visceral (sensory & motor) Visceral effectors Smooth muscles Glands Cardiac muscle Adipose tissue Figure 7.3 44 Module 7.3 Review a. Compare Schwann cells and satellite cells. b. Describe the neurilemma. c. Classify neurons into three categories according to their function. © 2013 Pearson Education, Inc. Membrane Potential (7.4) • Cytosol and extracellular fluid different composition • Slightly more positive ions outside cell • Slightly more negative ions inside cell • Unequal distribution of charge called membrane potential • Results from: • Different permeability of membrane to various ions • Active transport processes © 2013 Pearson Education, Inc. Membrane potential of a cell – + + – + – + + + Extracellular fluid – – + + – – + + – + + + + + + + + + + + + + + + + + + + + + Plasma membrane – – – – – – – – – – – – – – – – – – – – – – + + Cytosol – – – – – – Protein – – Protein – – + + Protein – + – – – – – + – + – © 2013 Pearson Education, Inc. Figure 7.4 11 Ion Concentrations (7.4) • Extracellular fluid (ECF) has high concentrations of: • Sodium (Na+) • Chloride (Cl–) • Cytosol has high concentrations of: • Potassium (K+) • Negatively charged proteins (Pr –) © 2013 Pearson Education, Inc. Ion Movements (7.4) • Ions can enter or leave cell only through: • Membrane channels • Some sodium and potassium channels always open • Some channels open in response to specific neurotransmitters • Some channels open or close in response to membrane potential changes • Active transport • Sodium–potassium exchange pump • Ejects 3 Na+ ions from cell; reclaims 2 K+ ions © 2013 Pearson Education, Inc. Ion channels and the membrane potential Potassium channel Sodium channel ECF Plasma membrane Sodium– potassium exchange pump Cytosol © 2013 Pearson Education, Inc. Figure 7.4 22 Neural Activity (7.4) • Changes in membrane potential may: • Trigger muscle contraction • Trigger gland secretion • Transfer information in nervous system © 2013 Pearson Education, Inc. Changes in Potential (7.4) • Resting cell membrane potential is resting potential • Stimulus produces localized change called graded potential • If graded potential large enough, triggers action potential • Action potential propagates (spreads) along axon toward terminal © 2013 Pearson Education, Inc. At the Synapse (7.4) • Synapse activity involves: • Presynaptic cell releasing neurotransmitters • Neurotransmitters binding to receptors on postsynaptic cell, changing membrane permeability • Thousands of axon terminals communicate with neuron cell body • Some neurotransmitters stimulate neuron • Some neurotransmitters inhibit neuron • Net effect determines if new action potential develops © 2013 Pearson Education, Inc. Role of the membrane potential in neural activity 1 2 4 3 3 Graded potential Resting stimulus potential produces may produce 5 Action potential triggers Information processing Presynaptic neuron © 2013 Pearson Education, Inc. Postsynaptic cell Figure 7.4 33 Module 7.4 Review a. Define membrane potential. b. What happens at the sodium–potassium exchange pump? c. List three body functions that result from changes in the membrane potential of a cell. © 2013 Pearson Education, Inc. Phases of an Action Potential (7.5) • Unequal distribution of charge across membrane called polarization • Depolarization • Neurotransmitter, like ACh, opens sodium channels • Positive sodium ion rushes into cell, making membrane potential less negative or less polarized • Repolarization • Sodium channels closed; potassium channels open • Positive potassium leaves the cell, making membrane potential more negative or more polarized © 2013 Pearson Education, Inc. Changes in membrane potential with stimuli Less polarized Repolarization Resting membrane potential (mV) Resting potential Depolarization More polarized Time © 2013 Pearson Education, Inc. Figure 7.5 11 Development of an Action Potential (7.5) • Graded potential depolarizes membrane • If depolarization reaches threshold potential, then action potential is triggered • Three steps involved 1. Neurotransmitter release on cell body opens sodium channels, causing large depolarization 2. Sodium channels then close and potassium channels open, causing repolarization 3. Sodium–potassium exchange pump resets original ion distribution © 2013 Pearson Education, Inc. Development of an action potential 2 1 Sodium channels open. © 2013 Pearson Education, Inc. 3 Sodium channels close. Potassium channels open. Sodium-potassium exchange pump ejects sodium ions and recaptures potassium ions. Figure 7.5 22 Propagation of an Action Potential (7.5) • Continuous propagation • Action potential at one location on axon triggers action potential at adjacent portion of membrane • Like closely spaced dominos falling • Saltatory propagation • Occurs in myelinated axons where membranes exposed only at nodes • Action potentials develop only at nodes • Much faster process, like dominos spaced farther apart © 2013 Pearson Education, Inc. Continuous and saltatory propagation of an action potential An action potential here at time 0 triggers an action potential here at time 1 which triggers an action potential here at time 2 which triggers an action potential here at time 3 and so on along the axon, in a series of tiny steps. Continuous propagation An action potential here at time 0 triggers an action potential here at time 1 which triggers an action potential here at time 2 which triggers an action potential here at time 3 and so on along the axon, skipping the segments in between. Saltatory propagation © 2013 Pearson Education, Inc. Figure 7.5 33- 4– 4 Speed of Action Potential Propagation (7.5) • Propagation speed fastest along: • Large-diameter axons • Myelinated axons • Urgent information carried along large-diameter, myelinated axons • Threats to survival or motor commands to prevent injury • Less urgent information carried on unmyelinated fibers © 2013 Pearson Education, Inc. Module 7.5 Review a. Describe depolarization and repolarization. b. Compare continuous and saltatory propagation. c. What is the relationship between myelin and the propagation speed of action potentials? © 2013 Pearson Education, Inc. Synapse (7.6) • Action potentials (nerve impulses) propagate along axon • Transfer of action potential from one neuron to another neuron or effector occurs at synapse • Presynaptic cell axon forms axon terminal • Contains neurotransmitters packaged in synaptic vesicles • Narrow space between presynaptic membrane and postsynaptic membrane is synaptic cleft PLAY Neurophysiology: Synapse © 2013 Pearson Education, Inc. Structures at a synapse Axon of presynaptic cell REPRESENTATIVE SYNAPSE Mitochondrion Axon terminal Presynaptic membrane Synaptic vesicles containing neurotransmitters Synaptic cleft Cytoplasm of postsynaptic cell © 2013 Pearson Education, Inc. Postsynaptic membrane Figure 7.6 11 Events at an ACh-releasing synapse Step 1 An action potential arrives and depolarizes the synaptic terminal. Presynaptic neuron Synaptic vesicles Action potential EXTRACELLULAR FLUID Axon terminal AChE POSTSYNAPTIC NEURON Step 2 Extracellular Ca2+ enters the synaptic terminal, triggering the exocytosis of ACh. ACh Synaptic cleft Chemically regulated sodium ion channels Step 3 ACh binds to receptors and depolarizes the postsynaptic membrane. Step 4 ACh is removed by AChE. © 2013 Pearson Education, Inc. Initiation of action potential if threshold is reached Propagation of action potential (if generated) Figure 7.6 33 Neurotransmitters (7.6) • Over 100 different neurotransmitters exist • All work in different ways • Acetylcholine (ACh) found at neuromuscular junctions © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Figure 7.6 22 Module 7.6 Review a. Describe the structure of a synapse. b. Describe the events that occur at a synapse when an action potential arrives at the axon terminal. c. Why is the depolarization on the postsynaptic cell temporary? © 2013 Pearson Education, Inc. Functional Anatomy of the CNS (Section 2) • Central nervous system consists of: • Spinal cord • Brain • Contains 97 percent of body's neural tissue • Weighs about 1.4 kg (3 lb) with 1200 mL volume • Male brain about 10 percent larger than female (due to differences in average body size) • No correlation between brain size and intelligence © 2013 Pearson Education, Inc. Development of Nervous System (Section 2) • Starts as neural tube • At 4 weeks development, consists of: • Hindbrain • Continuous with spinal cord • Midbrain • Expanded area next to forebrain • Forebrain • Tip of neural tube © 2013 Pearson Education, Inc. Lateral view of embryonic neural tube at four weeks The hindbrain is continuous with the spinal cord. The midbrain is an expansion next to the forebrain. The forebrain is at the tip of the neural tube. © 2013 Pearson Education, Inc. Spinal cord Figure 7 Section 2 1 1 Development of the Brain at Five Weeks (Section 2) • Forebrain divided into: • Diencephalon, major relay and processing center • Cerebrum • Midbrain • Hindbrain • Region close to midbrain will become cerebellum and pons • Region close to spinal cord will become medulla oblongata © 2013 Pearson Education, Inc. Brain development at five weeks Hindbrain Forebrain Cerebellum and pons Medulla oblongata Diencephalon Cerebrum Spinal cord © 2013 Pearson Education, Inc. Figure 7 Section 2 2 2 Regions of the Brain – Cerebrum (7.7) • Divided into two cerebral hemispheres • Superficial layer of gray matter called cerebral cortex • Functions • Conscious thought • Memory storage and processing • Sensory processing • Regulation of skeletal muscle contractions • Surface features • Fissures (deep grooves) • Gyri (folds) • Sulci (shallow depressions) © 2013 Pearson Education, Inc. Regions of the Brain (7.7) • Cerebellum • Second-largest structure in brain • Coordinates and modulates motor commands from cerebral cortex • Diencephalon • Thalamus • Relay and processing center for sensory information • Hypothalamus • Centers for emotions, autonomic functions, hormone production © 2013 Pearson Education, Inc. Regions of the Brain – Brain Stem (7.7) • Consists of three parts 1. Midbrain • Processes visual and auditory information • Helps maintain consciousness 2. Pons • Connects cerebellum to brain stem • Functions in somatic and visceral motor control 3. Medulla oblongata • Relays sensory information to brain stem and thalamus • Autonomic regulation centers for heart rate and blood pressure © 2013 Pearson Education, Inc. Major regions of the brain Cerebrum Fissures Gyri Diencephalon Thalamus Hypothalamus Brain stem Midbrain © 2013 Pearson Education, Inc. Sulci Spinal cord Cerebellum Pons Medulla oblongata Figure 7.7 11 Ventricles of the Brain (7.7) • Passageways within neural tube expand to form chambers called ventricles • Filled with cerebrospinal fluid • Lined with ependymal cells • Two large lateral ventricles in cerebrum • Interventricular foramen connects lateral ventricles to third ventricle in diencephalon • Cerebral aqueduct connects third ventricle to fourth ventricle in pons • Fourth ventricle continuous with central canal of spinal cord © 2013 Pearson Education, Inc. Ventricles of the brain Ventricles of the Brain Cerebral hemispheres Cerebral Longitudinal hemispheres fissure Lateral ventricle Interventricular foramen Third ventricle Cerebral aqueduct Fourth ventricle Pons Medulla oblongata Spinal cord Central canal Ventricular system, lateral view © 2013 Pearson Education, Inc. Central canal Cerebellum Ventricular system, anterior view Figure 7.7 22 Connections and Nuclei (7.7) • Corpus callosum • Thick tract of white matter connecting two cerebral hemispheres • Carries about 4 billion impulses per second • Nuclei • Groups of nerve cell bodies in CNS • Basal nuclei in each cerebral hemisphere • Subconscious control of muscle tone • Help direct movements like walking and running © 2013 Pearson Education, Inc. Interconnections between ventricles Corpus callosum Lateral ventricles Interventricular foramen Third ventricle Basal nuclei Cerebral aqueduct Fourth ventricle Cerebellum Central canal © 2013 Pearson Education, Inc. Figure 7.7 33 Module 7.7 Review a. Name the major regions of the brain and the distinct structures of each. b. Describe the role of the medulla oblongata. c. Which ventricles would lose communication by a blocked cerebral aqueduct? © 2013 Pearson Education, Inc. Cranial Meninges (7.8) • Dura mater • Outer and inner fibrous layers with small gap between • Dural sinuses, collecting venous blood, found in gap • Outer layer fused to periosteum (no epidural space) • Arachnoid mater • Outer epithelial layer supported by fibrous meshwork • Subarachnoid space separates outer layer from pia mater • Pia mater • Thin, delicate membrane that follows contours of brain © 2013 Pearson Education, Inc. Cranial meninges Subdural space Cranium (skull) 1 2 Arachnoid mater Dura mater Dura mater (outer layer) Dural sinus Arachnoid mater Subarachnoid space Dura mater (inner layer) 3 Pia mater Cerebral cortex © 2013 Pearson Education, Inc. Figure 7.8 11 Dural Folds (7.8) • Inner layer of dura mater extends into cranial cavity at points forming dural folds • Dural sinuses are collecting veins within dural folds • Falx cerebri • Dural fold between cerebral hemispheres • Contains inferior sagittal sinus and superior sagittal sinus • Tentorium cerebelli • Separates cerebral hemispheres from cerebellum • Falx cerebelli • Separates two cerebellar hemispheres © 2013 Pearson Education, Inc. Dural folds Superior sagittal sinus Tentorium cerebelli Falx cerebri Falx cerebelli © 2013 Pearson Education, Inc. Figure 7.8 22 Cerebrospinal Fluid (7.8) • Surrounds and bathes exposed surfaces of CNS • Produced by choroid plexus at rate of 500 mL/day • Choroid plexus is combination of specialized ependymal cells and capillaries • Flows from choroid plexus through ventricles and from fourth ventricle through lateral and median apertures into subarachnoid space and central canal • Absorbed into venous blood at arachnoid granulations • Total CSF volume 150 mL © 2013 Pearson Education, Inc. Cerebrospinal fluid production and absorption Nutrients, O2 Interstitial fluid in thalamus Capillaries Waste products, CO2 Neuron Astrocyte Choroid plexus Ependymal cells cells Remove wastes Produce CSF Superior sagittal sinus Cerebrospinal fluid in third ventricle Choroid plexus Dura mater Superior Cranium sagittal sinus Arachnoid granulation CSF movement Third ventricle Cerebral aqueduct Cerebral cortex Subdural space Arachnoid membrane Pia mater Median and lateral apertures Central canal of spinal cord Cerebrospinal fluid in central canal and subarachnoid space Dura mater Arachnoid mater Subarachnoid space Pia mater © 2013 Pearson Education, Inc. Figure 7.8 33- 4– 4 Choroid plexus details Interstitial fluid in thalamus Nutrients, O2 Capillaries Waste products, CO2 Neuron Astrocyte Choroid plexus Ependymal cells cells Remove wastes Produce CSF Choroid plexus © 2013 Pearson Education, Inc. Cerebrospinal fluid in third ventricle Figure 7.8 33 Choroid plexus details Dura mater Superior Cranium sagittal sinus Arachnoid granulation CSF movement Subdural space Cerebral cortex © 2013 Pearson Education, Inc. Arachnoid membrane Pia mater Figure 7.8 44 Module 7.8 Review a. From superficial to deep, name the three layers that make up the cranial meninges. b. Beginning at the choroid plexus, trace the flow of CSF. c. How would decreased diffusion across the arachnoid granulations affect the volume of cerebrospinal fluid in the ventricles? © 2013 Pearson Education, Inc. Lobes of the Cerebral Cortex (7.9) • Each cerebral hemisphere divided into regions called lobes • Surface lobes named after overlying bones • Frontal lobe • Parietal lobe • Temporal lobe • Occipital lobe • Fifth lobe, insula, medial to lateral sulcus © 2013 Pearson Education, Inc. Superficial Landmarks between Lobes (7.9) • Lateral sulcus • Separates frontal lobe from temporal lobe • Central sulcus • Separates frontal lobe from parietal lobe • Precentral gyrus is anterior to central sulcus • Contains primary motor cortex • Postcentral gyrus is posterior to central sulcus • Contains primary sensory cortex • Parieto-occipital sulcus • Separates parietal lobe from occipital lobe © 2013 Pearson Education, Inc. Superficial landmarks of the cerebral cortex Central sulcus Precentral gyrus Frontal lobe Postcentral gyrus Parietal lobe Lateral sulcus Occipital lobe Temporal lobe Cerebellum Pons Medulla oblongata Insula Lateral view of brain © 2013 Pearson Education, Inc. Figure 7.9 11- 2– 2 Midsagittal view of the cerebrum with photo Precentral gyrus Central sulcus Postcentral gyrus Limbic lobe Parietal lobe Frontal lobe Corpus callosum Parieto-occipital sulcus Occipital lobe Pineal gland Thalamus Hypothalamus Optic chiasm Pituitary gland Temporal lobe Pons Cerebral aqueduct Fourth ventricle Cerebellum Medulla oblongata Midsagittal section © 2013 Pearson Education, Inc. Figure 7.9 33 Cerebral Hemisphere Facts (7.9) • Crossing over • Sensory information from one side of body ends up on opposite side of brain • Motor commands from one side of brain go to opposite side of body • Occurs in brain stem and spinal cord • Similar functions, but also important differences between hemispheres © 2013 Pearson Education, Inc. Module 7.9 Review a. Identify the lobes of the cerebrum and indicate the basis for their names. b. Describe the insula. c. What effect would damage to the left postcentral gyrus produce? © 2013 Pearson Education, Inc. Cerebral Regions with Specific Functions (7.10) • Primary areas and association areas • Association areas interpret incoming data or coordinate motor response • Primary motor cortex • Sends voluntary commands to skeletal muscle • Neurons here called pyramidal cells (look like pyramids) • Somatic motor association area • Coordinates learned movements © 2013 Pearson Education, Inc. Sensory Cortex (7.10) • Primary sensory cortex • Receives general somatic sensory information • Processes sense of touch, pressure, pain, vibration, taste, and temperature • Somatic sensory association area • Monitors primary sensory cortex activity • Allows recognition of light touch © 2013 Pearson Education, Inc. Special Senses Cortex (7.10) • Primary visual cortex • Receives visual information from thalamus • Visual association area monitors visual cortex and interprets data • Gustatory cortex • Receives information from taste receptors • Olfactory cortex • Receives information from smell receptors • Primary auditory cortex • Receives sound information • Auditory association area monitors auditory cortex and recognizes sounds © 2013 Pearson Education, Inc. Regions of the cerebral lobes with specific functions Motor Cortex Sensory Cortex Primary motor cortex Primary sensory cortex Central sulcus Somatic motor association area PARIETAL LOBE Gustatory cortex OCCIPITAL LOBE FRONTAL LOBE Visual Cortex Olfactory cortex Auditory Cortex Primary auditory cortex Somatic sensory association area Primary visual cortex Lateral sulcus Visual association area TEMPORAL LOBE Auditory association area © 2013 Pearson Education, Inc. Figure 7.10 11 Integrative Centers (7.10) • Perform complex processes and are restricted to either left or right cerebral hemisphere • Speech center or Broca area or motor speech area • Regulates pattern of breathing and vocalization for speech • Prefrontal cortex • Used in abstract intellectual functions (predicting consequences of an action) • Frontal eye field • Controls learned eye movements like scanning text • General interpretive area • Usually in left hemisphere • Integrates sensory information and coordinates visual and auditory memories © 2013 Pearson Education, Inc. Integrative centers of the cerebrum Frontal eye field Speech center (Broca area or motor speech area) Prefrontal cortex © 2013 Pearson Education, Inc. General interpretive area Figure 7.10 22 Hemispheric Lateralization (7.10) • Left cerebral hemisphere • General interpretative and speech centers • Responsible for language-based skills • Important for analytical tasks like mathematics and logic • Right cerebral hemisphere • Analyzes and interprets sensory information • Enables identification by touch, smell, sight, taste • Allows recognition of faces and 3-D relationships • Important for analyzing emotional content of conversation © 2013 Pearson Education, Inc. Hemispheric lateralization of the cerebrum Right Cerebral Hemisphere Left Cerebral Hemisphere RIGHT HAND LEFT HAND Prefrontal cortex Prefrontal cortex Speech center Writing Auditory cortex (right ear) General interpretive center (language and mathematical calculation) Visual cortex (right visual field) © 2013 Pearson Education, Inc. C O R P U S C A L L O S U M Anterior commissure Analysis by touch Auditory cortex (left ear) Spatial visualization and analysis Visual cortex (left visual field) Figure 7.10 33 Handedness (7.10) • Premotor cortex controls hand movements • Larger in left hemisphere for right-handed people • About 9 percent of human population left-handed • High percentage artists and musicians left-handed • Primary motor cortex and association areas on right hemisphere near association areas for spatial visualization and emotions © 2013 Pearson Education, Inc. Module 7.10 Review a. Where is the primary motor cortex located? b. Which senses are affected by damage to the temporal lobes? c. A stroke patient is unable to speak. Which part of the brain has been affected? © 2013 Pearson Education, Inc. Diencephalon (7.11) • Surrounds third ventricle • Roof formed by portion of thalamus • Choroid plexus in anterior portion • Posterior portion contains pineal gland • Produces melatonin, helps regulate day–night cycles • Consists of: • Thalamus • Hypothalamus © 2013 Pearson Education, Inc. Thalamus (7.11) • Composed of two halves separated by third ventricle • Relay point and filter for sensory information • Sends some information to primary sensory cortex and rest to subconscious centers in the brain • Plays role in coordinating voluntary and involuntary motor commands © 2013 Pearson Education, Inc. Hypothalamus (7.11) • Contains centers associated with: 1. Subconscious centers involved with rage, pleasure, pain, sexual arousal as part of limbic system 2. Adjusting autonomic centers in pons and medulla oblongata 3. Coordinating nervous and endocrine system activities 4. Secretion of hormones (ADH, oxytocin) 5. Sensations of hunger and thirst 6. Coordinating voluntary and autonomic functions 7. Regulating normal body temperature 8. Coordinating daily activity cycles © 2013 Pearson Education, Inc. The diencephalon Diencephalon Thalamus Pineal gland Hypothalamus Midbrain © 2013 Pearson Education, Inc. Figure 7.11 1 Midbrain (7.11) • • Contains two pairs of sensory nuclei called colliculi • Superior colliculi control reflexes in response to visual stimuli • Inferior colliculi control reflexes in response to auditory stimuli Also contains: 1. Motor nuclei for oculomotor and trochlear cranial nerves 2. Reticular formation headquarters 3. Nuclei involved in maintaining muscle tone and posture 4. Nucleus that regulates motor output of basal ganglia called substantia nigra • Cerebral peduncles • Bundles of nerve fibers linking cerebrum to cerebellum and brain stem © 2013 Pearson Education, Inc. The diencephalon and midbrain Diencephalon Thalamus Pineal gland Hypothalamus Midbrain Substantia nigra Superior colliculi Inferior colliculi Cerebral peducles © 2013 Pearson Education, Inc. Figure 7.11 11- 2– 2 Brain Stem (7.11) 1. Midbrain • Processes visual and auditory data • Generates automatic motor responses (reflexes) 2. Pons • Relays sensory information to cerebellum and thalamus with cerebellar peduncles • Contains subconscious somatic and visceral motor centers including involuntary control of breathing • Includes sensory and motor nuclei for cranial nerves V–VIII 3. Medulla oblongata © 2013 Pearson Education, Inc. Medulla Oblongata (7.11) • Connects brain with spinal cord, relaying sensory information to thalamus and other parts of brain stem • Includes: 1. Sensory and motor nuclei associated with cranial nerves VIII–XII 2. Cardiovascular centers adjusting heart rate and strength of contraction 3. Respiratory rhythmicity centers, which set basic pace for breathing © 2013 Pearson Education, Inc. The brain stem Brain Stem: Diencephalon Thalamus Midbrain Pons Cerebellar peduncles Medulla oblongata © 2013 Pearson Education, Inc. Figure 7.11 3 Cerebellum (7.11) • Automatic processing center • Coordinates complex somatic motor patterns 1. Adjusts postural muscles to maintain balance 2. Programs and fine-tunes movements • Composed of white matter covered by neural cortex called cerebellar cortex © 2013 Pearson Education, Inc. The cerebellum Cerebellum © 2013 Pearson Education, Inc. Figure 7.11 5 Module 7.11 Review a. Name two major regions of the diencephalon. b. What are the three regions of the brain stem? c. What are two functions of the cerebellum? © 2013 Pearson Education, Inc. Reticular Activating System (7.12) • Reticular formation in brain stem regulates involuntary functions • Contains the reticular activating system (RAS) • Input from various sensory pathways carried through reticular formation to RAS • RAS then stimulates large areas of cerebral cortex • Stimulation of RAS increases alertness • Damage to RAS produces unconsciousness © 2013 Pearson Education, Inc. Reticular activating system Reticular activating system Special sensory input © 2013 Pearson Education, Inc. General cranial or spinal nerve input Nuclei and centers of the reticular formation Figure 7.12 Module 7.12 Review a. Describe the reticular formation. b. Describe the reticular activating system (RAS). c. You are sleeping and your RAS is suddenly activated. What will happen? © 2013 Pearson Education, Inc. Electroencephalogram (7.13) • Billions of neurons in brain producing electrical impulses • Can measure brain activity using electrodes on scalp • Printed report of this activity showing brain waves called electroencephalogram (EEG) • EEG shows abnormal brain activity such as seizures (temporary cerebral disorder) or seizure disorders like epilepsies © 2013 Pearson Education, Inc. Brain Waves (7.13) • Alpha waves indicate: • Healthy, awake adults, resting with eyes closed • Beta waves indicate: • Concentrating on task, under stress, psychological tension • Theta waves are seen in: • Mostly children, short time during sleep in normal adults, intense frustration in adults • If seen in other circumstances, may indicate brain disorder • Delta waves seen in: • Deep sleep at all ages • Infant brains and awake adults with damage to brain © 2013 Pearson Education, Inc. Brain waves on an electroencephalogram (EEG) Alpha waves Beta waves Theta waves Delta waves © 2013 Pearson Education, Inc. Figure 7.13 1 Module 7.13 Review a. Define electroencephalogram (EEG) and describe the four wave types associated with it. b. You are reading this textbook. If you had an EEG right now, which brain wave(s) would you expect to see? c. Differentiate between a seizure and epilepsy. © 2013 Pearson Education, Inc. Spinal Cord Structure (7.14) • Measures about 45 cm long in adults • Outer layer of white matter (myelinated axons); inner layer of gray matter (cell bodies, unmyelinated axons) around central canal • Cervical enlargement supplies nerves to shoulder and upper limb • Lumbar enlargement supplies nerves to pelvis and lower limbs • Conus medullaris is tapered, pointed part inferior to lumbar enlargement • Spinal cord ends at L1–L2 but spinal roots continue in flared formation called cauda equina (horse's tail) © 2013 Pearson Education, Inc. Superficial anatomy of the adult spinal cord Cervical spinal nerves Thoracic spinal nerves C1 C2 C3 C4 C5 C6 C7 C8 T1 T2 T3 T4 T5 T6 T7 T8 Cervical enlargement Posterior median sulcus T9 T10 T11 T12 L1 Lumbar enlargement Conus medullaris L2 Lumbar spinal nerves L3 L4 Inferior tip of spinal cord Cauda equina L5 Sacral spinal nerves S1 S2 S3 S4 S5 Coccygeal nerve (Co1) © 2013 Pearson Education, Inc. Figure 7.14 1 Spinal Cord Segments (7.14) • Spinal cord divided into 31 segments named according to associated vertebra • Posterior median sulcus is shallow, longitudinal groove on dorsal surface • Anterior median fissure is deep groove on ventral surface • Spinal nerve contains axons of sensory and motor neurons • Dorsal root contains axons of sensory neurons • Dorsal root ganglion contains cell bodies of sensory neurons • Ventral root contains axons of motor neurons © 2013 Pearson Education, Inc. Cross sections through segments of the spinal cord Posterior median sulcus Dorsal root Dorsal root ganglion White matter Gray matter Segment C3 Anterior median fissure Spinal nerve Ventral root White matter Gray matter Segment T3 Central canal Segment L1 © 2013 Pearson Education, Inc. Segment S2 Figure 7.14 2 Module 7.14 Review a. A typical spinal cord has how many pairs of spinal nerves, and where does the spinal cord end? b. Describe the composition of the gray matter of the spinal cord. c. Describe the gross anatomical features of a cross section of spinal cord. © 2013 Pearson Education, Inc. Gray Matter Organization in the Spinal Cord (7.15) • Gray matter in spinal cord forms letter H or butterfly shape • Projections toward outer surface are called horns • Posterior gray horn contains somatic and visceral sensory nuclei • Lateral gray horn found only in thoracic and lumbar segments contains visceral motor nuclei • Anterior gray horn contains somatic motor nuclei • Cell bodies of neurons in groups called nuclei • Sensory nuclei receive and relay sensory information from PNS • Motor nuclei issue motor commands to PNS © 2013 Pearson Education, Inc. Cross section of spinal cord Anterior view of spinal cord Posterior median sulcus Structural Organization of Gray Matter Dorsal root Central canal Dura mater Posterior gray horn Arachnoid mater (broken) Pia mater Dorsal root ganglion Lateral gray horn Anterior gray horn © 2013 Pearson Education, Inc. Anterior median fissure Ventral root Figure 7.15 1 White Matter Organization in the Spinal Cord (7.15) • Divided into regions called columns • Posterior white column • Lateral white column • Anterior white column • Columns contain tracts or bundles of axons in CNS • Ascending tracts carry sensory information • Descending tracts carry motor commands © 2013 Pearson Education, Inc. Diagrammatic view of the spinal cord Structural and Functional Organization of White Matter Posterior white column Functional Organization of Gray Matter Dorsal root Lateral white column Somatic Visceral Visceral Somatic Dorsal root ganglion Anterior white column Sensory nuclei Ventral root Motor nuclei © 2013 Pearson Education, Inc. Figure 7.15 2 Module 7.15 Review a. Name the three horns of the spinal cord gray matter. b. Differentiate between sensory and motor nuclei. c. What are the three columns in the white matter? © 2013 Pearson Education, Inc. Spinal Meninges (7.16) • Protect neural tissue from shocks • Continuous with cranial meninges • Three layers 1. Dura mater is tough, fibrous covering • Epidural space between dura mater and vertebral canal contains blood vessels and adipose tissue 2. Arachnoid mater includes epithelial layer and subarachnoid space 3. Pia mater is meshwork of elastic and collagen fibers attached to surface of spinal cord © 2013 Pearson Education, Inc. Spinal meninges Gray matter White matter Ventral root Spinal meninges Pia mater Spinal nerve Dorsal root Arachnoid mater Dura mater Epidural space © 2013 Pearson Education, Inc. Figure 7.16 1 Spinal Tap (7.16) • Sample of cerebrospinal fluid (CSF) collected by process called spinal tap or lumbar puncture • Spinal cord extends to L1 or L2 • Needle inserted between L2 and sacrum where spinal meninges enclose cauda equina and CSF • Performed to administer spinal anesthesia or to sample CSF to test for infection © 2013 Pearson Education, Inc. Location for a spinal tap or lumbar puncture Epidural space Lumbar puncture needle Cauda equina in subarachnoid space © 2013 Pearson Education, Inc. Figure 7.16 2 Module 7.16 Review a. What are the three layers of the spinal meninges? b. Where is the epidural space located and what does it contain? c. Why is a spinal tap done below the level of the L2 vertebra? © 2013 Pearson Education, Inc.