The Nervous System - Lecture Presentation PDF

Chapter 7 The Nervous System Lecture Presentation by Patty Bostwick-Taylor...

Chapter 7 The Nervous System Lecture Presentation by Patty Bostwick-Taylor Florence-Darlington Technical College © 2018 Pearson Education, Ltd.  Functions of the Nervous System 1. Sensory input—gathering information Sensory receptors monitor changes, called stimuli, occurring inside and outside the body 2. Integration Nervous system processes and interprets sensory input and decides whether action is needed 3. Motor output A response, or effect, activates muscles or glands © 2018 Pearson Education, Ltd. Figure 7.1 The nervous system’s functions. Sensory input Integration Sensory receptor Motor output Brain and spinal cord Effector © 2018 Pearson Education, Ltd. © 2018 Pearson Education, Ltd.  Organization of the Nervous System Nervous system classifications are based on: Structures (structural classification) Activities (functional classification) © 2018 Pearson Education, Ltd. Figure 7.2 Organization of the nervous system. Central Nervous System (brain and spinal cord) Peripheral Nervous System (cranial and spinal nerves) Sensory Motor (afferent) (efferent) Sense Somatic Autonomic organs (voluntary) (involuntary) Skeletal Cardiac and muscles smooth muscle, glands Parasympathetic Sympathetic © 2018 Pearson Education, Ltd.  Structural Classification Central nervous system (CNS) Organs Brain Spinal cord Function Integration; command center Interprets incoming sensory information Issues outgoing instructions © 2018 Pearson Education, Ltd.  Structural Classification Peripheral nervous system (PNS) Nerves extending from the brain and spinal cord Spinal nerves—carry impulses to and from the spinal cord Cranial nerves—carry impulses to and from the brain Functions Serve as communication lines among sensory organs, the brain and spinal cord, and glands or muscles © 2018 Pearson Education, Ltd.  Functional Classification Sensory (afferent) division Nerve fibers that carry information to the central nervous system Somatic sensory (afferent) fibers carry information from the skin, skeletal muscles, and joints Visceral sensory (afferent) fibers carry information from visceral organs Motor (efferent) division Nerve fibers that carry impulses away from the central nervous system organs to effector organs (muscles and glands) © 2018 Pearson Education, Ltd.  Functional Classification Motor (efferent) division (continued) Two subdivisions Somatic nervous system = voluntary Consciously (voluntarily) controls skeletal muscles Autonomic nervous system = involuntary Automatically controls smooth and cardiac muscles and glands Further divided into the sympathetic and parasympathetic nervous systems © 2018 Pearson Education, Ltd.  Nervous Tissue: Support Cells Support cells in the CNS are grouped together as neuroglia General functions Support Insulate Protect neurons © 2018 Pearson Education, Ltd.  Nervous Tissue: Structure and Function Nervous tissue is made up of two principal cell types Supporting cells (called neuroglia, or glial cells, or glia) Resemble neurons Unable to conduct nerve impulses Never lose the ability to divide Neurons © 2018 Pearson Education, Ltd.  Nervous Tissue: Supporting Cells CNS glial cells: astrocytes Abundant, star-shaped cells Brace and anchor neurons to blood capillaries Determine permeability and exchanges between blood capillaries and neurons Protect neurons from harmful substances in blood Control the chemical environment of the brain © 2018 Pearson Education, Ltd. Figure 7.3a Supporting cells (neuroglia) of nervous tissue. Capillary Neuron Astrocyte (a) Astrocytes are the most abundant and versatile neuroglia. © 2018 Pearson Education, Ltd.  Nervous Tissue: Supporting Cells CNS glial cells: microglia Spiderlike phagocytes Monitor health of nearby neurons Dispose of debris © 2018 Pearson Education, Ltd. Figure 7.3b Supporting cells (neuroglia) of nervous tissue. Neuron Microglial cell (b) Microglial cells are phagocytes that defend CNS cells. © 2018 Pearson Education, Ltd.  Nervous Tissue: Supporting Cells CNS glial cells: ependymal cells Line cavities of the brain and spinal cord Cilia assist with circulation of cerebrospinal fluid © 2018 Pearson Education, Ltd. Figure 7.3c Supporting cells (neuroglia) of nervous tissue. Fluid-filled cavity Ependymal cells Brain or spinal cord tissue (c) Ependymal cells line cerebrospinal fluid–filled cavities. © 2018 Pearson Education, Ltd.  Nervous Tissue: Supporting Cells CNS glial cells: oligodendrocytes Wrap around nerve fibers in the central nervous system Produce myelin sheaths © 2018 Pearson Education, Ltd. Figure 7.3d Supporting cells (neuroglia) of nervous tissue. Myelin sheath Process of oligodendrocyte Nerve fibers (d) Oligodendrocytes have processes that form myelin sheaths around CNS nerve fibers. © 2018 Pearson Education, Ltd.  Nervous Tissue: Supporting Cells PNS glial cells Schwann cells Form myelin sheath around nerve fibers in the PNS Satellite cells Protect and cushion neuron cell bodies © 2018 Pearson Education, Ltd. Figure 7.3e Supporting cells (neuroglia) of nervous tissue. Satellite Cell body of neuron cells Schwann cells (forming myelin sheath) Nerve fiber (e) Satellite cells and Schwann cells (which form myelin) surround neurons in the PNS. © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Neurons = nerve cells Cells specialized to transmit messages (nerve impulses) Major regions of all neurons Cell body—nucleus and metabolic center of the cell Processes—fibers that extend from the cell body © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Cell body is the metabolic center of the neuron Nucleus with large nucleolus Nissl bodies Rough endoplasmic reticulum Neurofibrils Intermediate filaments that maintain cell shape © 2018 Pearson Education, Ltd. Figure 7.4a Structure of a typical motor neuron. Dendrite Cell Mitochondrion body Nissl substance Axon hillock Axon Neurofibrils Collateral Nucleus branch Nucleolus One Schwann cell Node of Axon Ranvier terminal Schwann cells, forming the myelin sheath on axon (a) © 2018 Pearson Education, Ltd. Figure 7.4b Structure of a typical motor neuron. Neuron cell body Dendrite (b) © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Processes (fibers) Dendrites—conduct impulses toward the cell body Neurons may have hundreds of dendrites Axons—conduct impulses away from the cell body Neurons have only one axon arising from the cell body at the axon hillock End in axon terminals, which contain vesicles with neurotransmitters Axon terminals are separated from the next neuron by a gap © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Processes (fibers) (continued) Synaptic cleft—gap between axon terminals and the next neuron Synapse—functional junction between nerves where a nerve impulse is transmitted © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Myelin White, fatty material covering axons Protects and insulates fibers Speeds nerve impulse transmission © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Myelin sheaths Schwann cells—wrap axons in a jelly roll–like fashion (PNS) to form the myelin sheath Neurilemma—part of the Schwann cell external to the myelin sheath Nodes of Ranvier—gaps in myelin sheath along the axon Oligodendrocytes—produce myelin sheaths around axons of the CNS Lack a neurilemma © 2018 Pearson Education, Ltd. Figure 7.5 Relationship of Schwann cells to axons in the peripheral nervous system. Schwann cell cytoplasm Schwann cell Axon plasma membrane Schwann cell nucleus (a) (b) Neurilemma Myelin sheath (c) © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Terminology Nuclei—clusters of cell bodies in the CNS Ganglia—collections of cell bodies outside the CNS in the PNS Tracts—bundles of nerve fibers in the CNS Nerves—bundles of nerve fibers in the PNS White matter—collections of myelinated fibers (tracts) Gray matter—mostly unmyelinated fibers and cell bodies © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Functional classification Sensory (afferent) neurons Carry impulses from the sensory receptors to the CNS Receptors include: Cutaneous sense organs in skin Proprioceptors in muscles and tendons © 2018 Pearson Education, Ltd. Figure 7.6 Neurons classified by function. Central process (axon) Sensory neuron Spinal cord Cell (central nervous system) body Ganglion Dendrites Peripheral process (axon) Afferent transmission Interneuron (association neuron) Receptors Peripheral nervous system Efferent transmission Motor neuron To effectors (muscles and glands) © 2018 Pearson Education, Ltd. Figure 7.7a Types of sensory receptors. (a) Free nerve endings (pain and temperature receptors) © 2018 Pearson Education, Ltd. Figure 7.7b Types of sensory receptors. (b) Meissner’s corpuscle (touch receptor) © 2018 Pearson Education, Ltd. Figure 7.7c Types of sensory receptors. (c) Lamellar corpuscle (deep pressure receptor) © 2018 Pearson Education, Ltd. Figure 7.7d Types of sensory receptors. (d) Golgi tendon organ (proprioceptor) © 2018 Pearson Education, Ltd. Figure 7.7e Types of sensory receptors. (e) Muscle spindle (proprioceptor) © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Functional classification (continued) Motor (efferent) neurons Carry impulses from the central nervous system to viscera and/or muscles and glands Interneurons (association neurons) Cell bodies located in the CNS Connect sensory and motor neurons © 2018 Pearson Education, Ltd. Figure 7.6 Neurons classified by function. Central process (axon) Sensory neuron Spinal cord Cell (central nervous system) body Ganglion Dendrites Peripheral process (axon) Afferent transmission Interneuron (association neuron) Receptors Peripheral nervous system Efferent transmission Motor neuron To effectors (muscles and glands) © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Structural classification Based on number of processes extending from the cell body Multipolar neurons—many extensions from the cell body All motor and interneurons are multipolar Most common structural type © 2018 Pearson Education, Ltd. Figure 7.8a Classification of neurons on the basis of structure. Cell body Axon Dendrites (a) Multipolar neuron © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Structural classification (continued) Bipolar neurons—one axon and one dendrite Located in special sense organs, such as nose and eye Rare in adults © 2018 Pearson Education, Ltd. Figure 7.8b Classification of neurons on the basis of structure. Cell body Dendrite Axon (b) Bipolar neuron © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Structural classification (continued) Unipolar neurons—have a short single process leaving the cell body Sensory neurons found in PNS ganglia Conduct impulses both toward and away from the cell body © 2018 Pearson Education, Ltd. Figure 7.8c Classification of neurons on the basis of structure. Dendrites Cell body Short single process Axon Peripheral Central process process (c) Unipolar neuron © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Functional properties of neurons Irritability Ability to respond to a stimulus and convert it to a nerve impulse Conductivity Ability to transmit the impulse to other neurons, muscles, or glands © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Electrical conditions of a resting neuron’s membrane The plasma membrane at rest is inactive (polarized) Fewer positive ions are inside the neuron’s plasma membrane than outside K+ is the major positive ion inside the cell Na+ is the major positive ion outside the cell As long as the inside of the membrane is more negative (fewer positive ions) than the outside, the cell remains inactive © 2018 Pearson Education, Ltd. Figure 7.9 The nerve impulse. Slide 2 [Na+ ] 1 Resting membrane is polarized. In the resting state, the [K+] external face of the membrane is slightly positive; its internal face is slightly negative. The chief extracellular ion is sodium (Na+), whereas the chief intracellular ion is potassium (K+). The membrane is relatively impermeable to both ions. © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Action potential initiation and generation A stimulus changes the permeability of the neuron’s membrane to sodium ions Sodium channels now open, and sodium (Na+) diffuses into the neuron The inward rush of sodium ions changes the polarity at that site and is called depolarization © 2018 Pearson Education, Ltd. Figure 7.9 The nerve impulse. Slide 3 Na+ 2 Stimulus initiates local depolarization. A stimulus Na+ changes the permeability of a local “patch” of the membrane, and sodium ions diffuse rapidly into the cell. This changes the polarity of the membrane (the inside becomes more positive; the outside becomes more negative) at that site. © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Action potential initiation and generation (continued) A graded potential (localized depolarization) exists where the inside of the membrane is more positive and the outside is less positive If the stimulus is strong enough and sodium influx great enough, local depolarization activates the neuron to conduct an action potential (nerve impulse) © 2018 Pearson Education, Ltd. Figure 7.9 The nerve impulse. Slide 4 Na+ 3 Depolarization and generation of an action potential. If the stimulus is strong enough, depolarization causes Na+ membrane polarity to be completely reversed, and an action potential is initiated. © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Propagation of the action potential If enough sodium enters the cell, the action potential (nerve impulse) starts and is propagated over the entire axon All-or-none response means the nerve impulse either is propagated or is not Fibers with myelin sheaths conduct nerve impulses more quickly © 2018 Pearson Education, Ltd. Figure 7.9 The nerve impulse. Slide 5 4 Propagation of the action potential. Depolarization of the first membrane patch causes permeability changes in the adjacent membrane, and the events described in step 2 are repeated. Thus, the action potential propagates rapidly along the entire length of the membrane. © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Repolarization Membrane permeability changes again—becoming impermeable to sodium ions and permeable to potassium ions Potassium ions rapidly diffuse out of the neuron, repolarizing the membrane Repolarization involves restoring the inside of the membrane to a negative charge and the outer surface to a positive charge © 2018 Pearson Education, Ltd. Figure 7.9 The nerve impulse. Slide 6 K+ 5 Repolarization. Potassium ions diffuse out of the cell as K+ the membrane permeability changes again, restoring the negative charge on the inside of the membrane and the positive charge on the outside surface. Repolarization occurs in the same direction as depolarization. © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Repolarization (continued) Initial conditions of sodium and potassium ions are restored using the sodium-potassium pump This pump, using ATP, restores the original configuration Three sodium ions are ejected from the cell while two potassium ions are returned to the cell Until repolarization is complete, a neuron cannot conduct another nerve impulse © 2018 Pearson Education, Ltd. Figure 7.9 The nerve impulse. Slide 7 Cell Na+ – K+ exterior pump 6 Initial ionic conditions restored. The ionic conditions Na+ Diffusion K+ Diffusion of the resting state are restored later by the activity of the Plasma membrane sodium-potassium pump. Three sodium ions are ejected for every two potassium ions carried back into the cell. Cell interior © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Transmission of the signal at synapses Step 1: When the action potential reaches the axon terminal, the electrical charge opens calcium channels © 2018 Pearson Education, Ltd. Figure 7.10 How neurons communicate at chemical synapses. Slide 2 Axon of transmitting neuron Receiving neuron 1 Action Dendrite potential arrives. Vesicle Axon terminal sSynaptic cleft © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Transmission of the signal at synapses (continued) Step 2: Calcium, in turn, causes the tiny vesicles containing the neurotransmitter chemical to fuse with the axonal membrane © 2018 Pearson Education, Ltd. Figure 7.10 How neurons communicate at chemical synapses. Slide 3 2 Vesicle Transmitting neuron fuses with plasma membrane. Synaptic cleft Ion Neurotransmitter channels molecules Receiving neuron Receiving neuron © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Transmission of the signal at synapses (continued) Step 3: The entry of calcium into the axon terminal causes porelike openings to form, releasing the neurotransmitter into the synaptic cleft © 2018 Pearson Education, Ltd. Figure 7.10 How neurons communicate at chemical synapses. Slide 4 2 Vesicle Transmitting neuron fuses with plasma 3 Neurotrans- membrane. mitter is released into synaptic cleft. Synaptic cleft Ion Neurotransmitter channels molecules Receiving neuron Receiving neuron © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Transmission of the signal at synapses (continued) Step 4: The neurotransmitter molecules diffuse across the synaptic cleft and bind to receptors on the membrane of the next neuron © 2018 Pearson Education, Ltd. Figure 7.10 How neurons communicate at chemical synapses. Slide 5 2 Vesicle Transmitting neuron fuses with 4 Neurotrans- plasma 3 Neurotrans- mitter binds membrane. mitter is to receptor released into on receiving synaptic cleft. neuron’s membrane. Synaptic cleft Ion Neurotransmitter channels molecules Receiving neuron Receiving neuron © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Transmission of the signal at synapses (continued) Step 5: If enough neurotransmitter is released, a graded potential will be generated Eventually an action potential (nerve impulse) will occur in the neuron beyond the synapse © 2018 Pearson Education, Ltd. Figure 7.10 How neurons communicate at chemical synapses. Slide 6 5 Ion channel opens. Neurotransmitter Receptor Na+ Receiving neuron © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Transmission of the signal at synapses (continued) Step 6: The electrical changes prompted by neurotransmitter binding are brief The neurotransmitter is quickly removed from the synapse either by reuptake or by enzymatic activity Transmission of an impulse is electrochemical Transmission down neuron is electrical Transmission to next neuron is chemical © 2018 Pearson Education, Ltd. Figure 7.10 How neurons communicate at chemical synapses. Slide 7 6 Ion channel closes. Neurotransmitter is broken down and released. Na+ Receiving neuron © 2018 Pearson Education, Ltd.  BioFlix: How Synapses Work © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Reflexes are rapid, predictable, and involuntary responses to stimuli Reflexes occur over neural pathways called reflex arcs Two types of reflexes Somatic reflexes Autonomic reflexes © 2018 Pearson Education, Ltd. Figure 7.11a Simple reflex arcs. Stimulus at distal Skin Spinal cord end of neuron (in cross section) 2 Sensory neuron 3Integration 1 Receptor center 4 Motor neuron 5 Effector Interneuron (a) Five basic elements of reflex arc © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Somatic reflexes Reflexes that stimulate the skeletal muscles Involuntary, although skeletal muscle is normally under voluntary control Example: pulling your hand away from a hot object Autonomic reflexes Regulate the activity of smooth muscles, the heart, and glands Example: regulation of smooth muscles, heart and blood pressure, glands, digestive system © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Five elements of a reflex arc 1. Sensory receptor—reacts to a stimulus 2. Sensory neuron—carries message to the integration center 3. Integration center (CNS)—processes information and directs motor output 4. Motor neuron—carries message to an effector 5. Effector organ—is the muscle or gland to be stimulated © 2018 Pearson Education, Ltd. Figure 7.11a Simple reflex arcs. Slide 2 Stimulus at distal Skin end of neuron 1 Receptor (a) Five basic elements of reflex arc © 2018 Pearson Education, Ltd. Figure 7.11a Simple reflex arcs. Slide 3 Stimulus at distal Skin Spinal cord end of neuron (in cross section) 2 Sensory neuron 1 Receptor Interneuron (a) Five basic elements of reflex arc © 2018 Pearson Education, Ltd. Figure 7.11a Simple reflex arcs. Slide 4 Stimulus at distal Skin Spinal cord end of neuron (in cross section) 2 Sensory neuron 3 Integration 1 Receptor center Interneuron (a) Five basic elements of reflex arc © 2018 Pearson Education, Ltd. Figure 7.11a Simple reflex arcs. Slide 5 Stimulus at distal Skin Spinal cord end of neuron (in cross section) 2 Sensory neuron 3 Integration 1 Receptor center 4 Motor neuron Interneuron (a) Five basic elements of reflex arc © 2018 Pearson Education, Ltd. Figure 7.11a Simple reflex arcs. Slide 6 Stimulus at distal Skin Spinal cord end of neuron (in cross section) 2 Sensory neuron 3 Integration 1 Receptor center 4 Motor neuron 5 Effector Interneuron (a) Five basic elements of reflex arc © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Two-neuron reflex arcs Simplest type Example: patellar (knee-jerk) reflex © 2018 Pearson Education, Ltd. Figure 7.11b Simple reflex arcs. Slide 1 1 Sensory (stretch) receptor 2 Sensory (afferent) neuron 3 4 Motor (efferent) neuron 5 Effector organ (b) Two-neuron reflex arc © 2018 Pearson Education, Ltd. Figure 7.11b Simple reflex arcs. Slide 2 1 Sensory (stretch) receptor (b) Two-neuron reflex arc © 2018 Pearson Education, Ltd. Figure 7.11b Simple reflex arcs. Slide 3 1 Sensory (stretch) receptor 2 Sensory (afferent) neuron (b) Two-neuron reflex arc © 2018 Pearson Education, Ltd. Figure 7.11b Simple reflex arcs. Slide 4 1 Sensory (stretch) receptor 2 Sensory (afferent) neuron 3 (b) Two-neuron reflex arc © 2018 Pearson Education, Ltd. Figure 7.11b Simple reflex arcs. Slide 5 1 Sensory (stretch) receptor 2 Sensory (afferent) neuron 3 4 Motor (efferent) neuron (b) Two-neuron reflex arc © 2018 Pearson Education, Ltd. Figure 7.11b Simple reflex arcs. Slide 6 1 Sensory (stretch) receptor 2 Sensory (afferent) neuron 3 4 Motor (efferent) neuron 5 Effector organ (b) Two-neuron reflex arc © 2018 Pearson Education, Ltd.  Nervous Tissue: Neurons Three-neuron reflex arcs Consists of five elements: receptor, sensory neuron, interneuron, motor neuron, and effector Example: flexor (withdrawal) reflex © 2018 Pearson Education, Ltd. Figure 7.11c Simple reflex arcs. Slide 1 1 Sensory receptor 2 Sensory (afferent) neuron 3 Interneuron 4 Motor (efferent) neuron 5 Effector organ (c) Three-neuron reflex arc © 2018 Pearson Education, Ltd. Figure 7.11c Simple reflex arcs. Slide 2 1 Sensory receptor (c) Three-neuron reflex arc © 2018 Pearson Education, Ltd. Figure 7.11c Simple reflex arcs. Slide 3 1 Sensory receptor 2 Sensory (afferent) neuron (c) Three-neuron reflex arc © 2018 Pearson Education, Ltd. Figure 7.11c Simple reflex arcs. Slide 4 1 Sensory receptor 2 Sensory (afferent) neuron 3 Interneuron (c) Three-neuron reflex arc © 2018 Pearson Education, Ltd. Figure 7.11c Simple reflex arcs. Slide 5 1 Sensory receptor 2 Sensory (afferent) neuron 3 Interneuron 4 Motor (efferent) neuron (c) Three-neuron reflex arc © 2018 Pearson Education, Ltd. Figure 7.11c Simple reflex arcs. Slide 6 1 Sensory receptor 2 Sensory (afferent) neuron 3 Interneuron 4 Motor (efferent) neuron 5 Effector organ (c) Three-neuron reflex arc © 2018 Pearson Education, Ltd.  Central Nervous System (CNS) Functional anatomy of the brain Brain regions Cerebral hemispheres Diencephalon Brain stem Cerebellum © 2018 Pearson Education, Ltd.  Functional Anatomy of the Brain Cerebral hemispheres are paired (left and right) superior parts of the brain Include more than half of the brain mass The surface is made of ridges (gyri) and grooves (sulci) Fissures are deeper grooves Lobes are named for the cranial bones that lie over them © 2018 Pearson Education, Ltd.  Functional Anatomy of the Brain Three main regions of cerebral hemisphere 1. Cortex is superficial gray matter 2. White matter 3. Basal nuclei are deep pockets of gray matter © 2018 Pearson Education, Ltd. Figure 7.12a Development and regions of the human brain. Cerebral hemisphere Outline of diencephalon Midbrain Cerebellum Brain stem (a) 13 weeks © 2018 Pearson Education, Ltd. Figure 7.12b Development and regions of the human brain. Cerebral hemisphere Diencephalon Cerebellum Brain stem (b) Adult brain © 2018 Pearson Education, Ltd. Figure 7.13ab Left lateral view of the brain. Precentral gyrus Central sulcus Parietal lobe Postcentral gyrus Frontal lobe Parietal lobe Left cerebral Parieto-occipital hemisphere sulcus (deep) Lateral sulcus Frontal Occipital lobe lobe Occipital Temporal lobe Temporal lobe Cerebellum lobe Pons Superior Cerebral cortex Medulla Brain Cerebellum Inferior (gray matter) oblongata stem Spinal (b) Gyrus cord Sulcus Cerebral Fissure white (a deep sulcus) matter (a) © 2018 Pearson Education, Ltd. Table 7.1 Functions of Major Brain Regions (1 of 2) © 2018 Pearson Education, Ltd. Table 7.1 Functions of Major Brain Regions (2 of 2) © 2018 Pearson Education, Ltd.  Functional Anatomy of the Brain Cerebral cortex Primary somatic sensory area Located in parietal lobe posterior to central sulcus Receives impulses from the body’s sensory receptors Pain, temperature, light touch (except for special senses) Sensory homunculus is a spatial map Left side of the primary somatic sensory area receives impulses from right side (and vice versa) © 2018 Pearson Education, Ltd. Figure 7.13c Left lateral view of the brain. Central sulcus Primary motor area Primary somatic sensory Premotor area area Anterior Gustatory area (taste) association area Working memory Speech/language and judgment (outlined by dashes) Problem Posterior association solving area Language comprehension Visual area Broca’s area (motor speech) Olfactory Auditory area area (c) © 2018 Pearson Education, Ltd. Figure 7.14 Sensory and motor areas of the cerebral cortex. Posterior Motor Sensory Motor map in Anterior Sensory map in Shoul precentral gyrus postcentral gyrus Head Ha earm kNeck Trun Trun k Elb rm ow Hip L eg d er Knee Elb t Arm Wri Hip Ha s A r nd er Fi Fo n ow s ng ng d er Fi Knee Th s b um um Foot b Th Nec e Ey Bro k se w o N Eye Toe ce Fa s s F ace Genitals L ip Lips T eet s m h uw G Ja Jaw Tongu e Tongu Primary motor Primary somatic Pharynx e cortex sensory cortex Intra- Swallowing (precentral gyrus) (postcentral gyrus) abdominal © 2018 Pearson Education, Ltd.  Functional Anatomy of the Brain Cerebral areas involved in special senses Visual area (occipital lobe) Auditory area (temporal lobe) Olfactory area (temporal lobe) © 2018 Pearson Education, Ltd.  Functional Anatomy of the Brain Cerebral cortex (continued) Primary motor area Located anterior to the central sulcus in the frontal lobe Allows us to consciously move skeletal muscles Motor neurons form pyramidal (corticospinal) tract, which descends to spinal cord Motor homunculus is a spatial map © 2018 Pearson Education, Ltd. Figure 7.13a Left lateral view of the brain. Precentral gyrus Central sulcus Postcentral gyrus Frontal lobe Parietal lobe Parieto-occipital sulcus (deep) Lateral sulcus Occipital lobe Temporal lobe Cerebellum Pons Cerebral cortex Medulla (gray matter) oblongata Gyrus Spinal cord Sulcus Cerebral Fissure white (a deep sulcus) matter (a) © 2018 Pearson Education, Ltd. Figure 7.14 Sensory and motor areas of the cerebral cortex. Posterior Motor Sensory Motor map in Anterior Sensory map in Shoul precentral gyrus postcentral gyrus Head Ha earm kNeck Trun Trun k Elb rm ow Hip L eg d er Knee Elb t Arm Wri Hip Ha s A r nd er Fi Fo n ow s ng ng d er Fi Knee Th s b um um Foot b Th Nec e Ey Bro k se w o N Eye Toe ce Fa s s F ace Genitals L ip Lips T eet s m h uw G Ja Jaw Tongu e Tongu Primary motor Primary somatic Pharynx e cortex sensory cortex Intra- Swallowing (precentral gyrus) (postcentral gyrus) abdominal © 2018 Pearson Education, Ltd.  Functional Anatomy of the Brain Cerebral cortex (continued) Broca’s area (motor speech area) Involved in our ability to speak Usually in left hemisphere Other specialized areas Anterior association area (frontal lobe) Posterior association area (posterior cortex) Speech area (for sounding out words) © 2018 Pearson Education, Ltd. Figure 7.13c Left lateral view of the brain. Central sulcus Primary motor area Primary somatic sensory Premotor area area Anterior Gustatory area (taste) association area Working memory Speech/language and judgment (outlined by dashes) Problem Posterior association solving area Language comprehension Visual area Broca’s area (motor speech) Olfactory Auditory area area (c) © 2018 Pearson Education, Ltd.  Functional Anatomy of the Brain Cerebral white matter Composed of fiber tracts deep to the gray matter Corpus callosum connects hemispheres Tracts, such as the corpus callosum, are known as commissures Association fiber tracts connect areas within a hemisphere Projection fiber tracts connect the cerebrum with lower CNS centers © 2018 Pearson Education, Ltd. Figure 7.13a Left lateral view of the brain. Precentral gyrus Central sulcus Postcentral gyrus Frontal lobe Parietal lobe Parieto-occipital sulcus (deep) Lateral sulcus Occipital lobe Temporal lobe Cerebellum Pons Cerebral cortex Medulla (gray matter) oblongata Gyrus Spinal cord Sulcus Cerebral Fissure white (a deep sulcus) matter (a) © 2018 Pearson Education, Ltd. Figure 7.15 Frontal section (facing posteriorly) of the brain showing commissural, association, and projection fibers running through the cerebrum and the lower CNS. Longitudinal fissure Association fibers Superior Lateral Commissural fibers ventricle (corpus callosum) Corona Basal nuclei radiata Fornix Internal Thalamus capsule Third ventricle Pons Projection fibers Medulla oblongata © 2018 Pearson Education, Ltd.  Functional Anatomy of the Brain Basal nuclei “Islands” of gray matter buried deep within the white matter of the cerebrum Regulate voluntary motor activities by modifying instructions sent to skeletal muscles by the primary motor cortex © 2018 Pearson Education, Ltd.  Functional Anatomy of the Brain Diencephalon Sits on top of the brain stem Enclosed by the cerebral hemispheres Made of three structures 1. Thalamus 2. Hypothalamus 3. Epithalamus © 2018 Pearson Education, Ltd. Figure 7.12b Development and regions of the human brain. Cerebral hemisphere Diencephalon Cerebellum Brain stem (b) Adult brain © 2018 Pearson Education, Ltd. Figure 7.16a Diencephalon and brain stem structures. Cerebral hemisphere Corpus callosum Third ventricle Choroid plexus of third ventricle Occipital lobe of cerebral hemisphere Thalamus Anterior (encloses third ventricle) commissure Pineal gland (part of epithalamus) Hypothalamus Corpora quadrigemina Optic chiasma Cerebral Midbrain aqueduct Pituitary gland Cerebral peduncle Mammillary body Fourth ventricle Pon s Choroid plexus Medulla oblongata (part of epithalamus) Spinal cord Cerebellum (a) © 2018 Pearson Education, Ltd. Figure 7.16b Diencephalon and brain stem structures. Radiations to cerebral cortex Auditory Visual impulses impulses Reticular formation Descending motor projections Ascending general sensory to spinal cord tracts (touch, pain, temperature) (b) © 2018 Pearson Education, Ltd.  Functional Anatomy of the Brain Diencephalon: thalamus Encloses the third ventricle Relay station for sensory impulses passing upward to the cerebral cortex Transfers impulses to the correct part of the cortex for localization and interpretation © 2018 Pearson Education, Ltd.  Functional Anatomy of the Brain Diencephalon: hypothalamus Makes up the floor of the diencephalon Important autonomic nervous system center Regulates body temperature Regulates water balance Regulates metabolism Houses the limbic center for emotions Regulates the nearby pituitary gland Houses mammillary bodies for olfaction (smell) © 2018 Pearson Education, Ltd.  Functional Anatomy of the Brain Diencephalon: epithalamus Forms the roof of the third ventricle Houses the pineal body (an endocrine gland) Includes the choroid plexus—forms cerebrospinal fluid © 2018 Pearson Education, Ltd.  Functional Anatomy of the Brain Brain stem Attaches to the spinal cord Parts of the brain stem 1. Midbrain 2. Pons 3. Medulla oblongata © 2018 Pearson Education, Ltd. Figure 7.16a Diencephalon and brain stem structures. Cerebral hemisphere Corpus callosum Third ventricle Choroid plexus of third ventricle Occipital lobe of cerebral hemisphere Thalamus Anterior (encloses third ventricle) commissure Pineal gland (part of epithalamus) Hypothalamus Corpora quadrigemina Optic chiasma Cerebral Midbrain aqueduct Pituitary gland Cerebral peduncle Mammillary body Fourth ventricle Pon s Choroid plexus Medulla oblongata (part of epithalamus) Spinal cord Cerebellum (a) © 2018 Pearson Education, Ltd.  Functional Anatomy of the Brain Brain stem: midbrain Extends from the mammillary bodies to the pons inferiorly Cerebral aqueduct (tiny canal) connects the third and fourth ventricles Two bulging fiber tracts, cerebral peduncles, convey ascending and descending impulses Four rounded protrusions, corpora quadrigemina, are visual and auditory reflex centers © 2018 Pearson Education, Ltd.  Functional Anatomy of the Brain Brain stem: pons The rounded structure protruding just below the midbrain Mostly composed of fiber tracts Includes nuclei involved in the control of breathing © 2018 Pearson Education, Ltd.  Functional Anatomy of the Brain Brain stem: medulla oblongata The most inferior part of the brain stem that merges into the spinal cord Includes important fiber tracts Contains important centers that control: Heart rate Blood pressure Breathing Swallowing Vomiting Fourth ventricle lies posterior to pons and medulla © 2018 Pearson Education, Ltd.  Functional Anatomy of the Brain Brain stem: reticular formation Diffuse mass of gray matter along the brain stem Involved in motor control of visceral organs Reticular activating system (RAS) Plays a role in awake/sleep cycles and consciousness Filter for incoming sensory information © 2018 Pearson Education, Ltd. Figure 7.16b Diencephalon and brain stem structures. Radiations to cerebral cortex Auditory Visual impulses impulses Reticular formation Descending motor projections Ascending general sensory to spinal cord tracts (touch, pain, temperature) (b) © 2018 Pearson Education, Ltd.  Functional Anatomy of the Brain Cerebrum Two hemispheres with convoluted surfaces Outer cortex of gray matter and inner region of white matter Controls balance Provides precise timing for skeletal muscle activity and coordination of body movements © 2018 Pearson Education, Ltd. Figure 7.16a Diencephalon and brain stem structures. Cerebral hemisphere Corpus callosum Third ventricle Choroid plexus of third ventricle Occipital lobe of cerebral hemisphere Thalamus Anterior (encloses third ventricle) commissure Pineal gland (part of epithalamus) Hypothalamus Corpora quadrigemina Optic chiasma Cerebral Midbrain aqueduct Pituitary gland Cerebral peduncle Mammillary body Fourth ventricle Pon s Choroid plexus Medulla oblongata (part of epithalamus) Spinal cord Cerebellum (a) © 2018 Pearson Education, Ltd.  Protection of the Central Nervous System Meninges Cerebrospinal fluid (CSF) Blood-brain barrier © 2018 Pearson Education, Ltd.  Protection of the Central Nervous System Meninges (continued) Dura mater Outermost leathery layer Double-layered external covering Periosteum—attached to inner surface of the skull Meningeal layer—outer covering of the brain Folds inward in several areas Falx cerebri Tentorium cerebelli © 2018 Pearson Education, Ltd.  Protection of the Central Nervous System Meninges (continued) Arachnoid layer Middle layer Weblike extensions span the subarachnoid space to attach it to the pia mater Subarachnoid space is filled with cerebrospinal fluid Arachnoid granulations protrude through the dura mater and absorb cerebrospinal fluid into venous blood Pia mater Internal layer Clings to the surface of the brain and spinal cord © 2018 Pearson Education, Ltd. Figure 7.17a Meninges of the brain. Skin of scalp Periosteum Bone of skull Periosteal Dura Meningeal mater Superior sagittal sinus Arachnoid mater Subdural Pia mater space Arachnoid granulation Subarachnoid Blood space vessel Falx cerebri (in longitudinal (a) fissure only) © 2018 Pearson Education, Ltd. Figure 7.17b Meninges of the brain. Skull Scalp Superior sagittal sinus Occipital lobe Dura mater Tentoriu m Transvers Cerebellum cerebelli e Tempora sinus Arachnoid mater l over medulla oblongata bone (b) © 2018 Pearson Education, Ltd.  Protection of the Central Nervous System Cerebrospinal fluid Similar to blood plasma in composition Formed continually by the choroid plexuses Choroid plexuses—capillaries in the ventricles of the brain CSF forms a watery cushion to protect the brain and spinal cord Circulated in the arachnoid space, ventricles, and central canal of the spinal cord © 2018 Pearson Education, Ltd.  Protection of the Central Nervous System Cerebrospinal fluid circulation 1. CSF is produced by the choroid plexus of each ventricle 2. CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. Some CSF flows through the central canal of the spinal cord 3. CSF flows through the subarachnoid space 4. CSF is absorbed into the dural venous sinuses via the arachnoid villi © 2018 Pearson Education, Ltd. Figure 7.18a Ventricles and location of the cerebrospinal fluid. Lateral ventricle Anterior horn Septum pellucidum Interventricular foramen Inferior horn Third ventricle Lateral Cerebral aqueduct aperture Fourth ventricle Central canal (a) Anterior view © 2018 Pearson Education, Ltd. Figure 7.18b Ventricles and location of the cerebrospinal fluid. Lateral ventricle Anterior horn Posterior Interventricular horn foramen Third ventricle Inferior horn Cerebral aqueduct Median aperture Fourth ventricle Lateral Central canal aperture (b) Left lateral view © 2018 Pearson Education, Ltd. Figure 7.18c Ventricles and location of the cerebrospinal fluid. 4 Superior sagittal sinus Arachnoid granulation Choroid plexuses Subarachnoid space of lateral and Arachnoid mater third ventricles Meningeal dura mater Corpus callosum Periosteal dura mater 1 Interventricular Right lateral ventricle foramen (deep to cut) Third ventricle 3 Choroid plexus of fourth ventricle Cerebral aqueduct Lateral aperture 1 CSF is produced by the Fourth ventricle 2 choroid plexus of each Median aperture ventricle. 2 CSF flows through the ventricles and into the subarachnoid space via Central canal the median and lateral apertures. of spinal cord Some CSF flows through the central canal of the spinal cord. 3 CSF flows through the subarachnoid space. 4 CSF is absorbed into the dural venous sinuses via the arachnoid granulations. (c) CSF circulation © 2018 Pearson Education, Ltd.  Protection of the Central Nervous System Blood-brain barrier Includes the least permeable capillaries of the body Allows water, glucose, and amino acids to pass through the capillary walls Excludes many potentially harmful substances from entering the brain, such as wastes Useless as a barrier against some substances © 2018 Pearson Education, Ltd.  Brain Dysfunctions Traumatic brain injuries Concussion Slight brain injury Typically little permanent brain damage occurs Contusion Marked nervous tissue destruction occurs Coma may occur Death may occur after head blows due to: Intracranial hemorrhage Cerebral edema © 2018 Pearson Education, Ltd.  Brain Dysfunctions Cerebrovascular accident (CVA), or stroke Results when blood circulation to a brain area is blocked and brain tissue dies Loss of some functions or death may result Hemiplegia—one-sided paralysis Aphasia—damage to speech center in left hemisphere Transient ischemic attack (TIA) Temporary brain ischemia (restriction of blood flow) Numbness, temporary paralysis, impaired speech © 2018 Pearson Education, Ltd.  Spinal Cord Extends from the foramen magnum of the skull to the first or second lumbar vertebra Cauda equina is a collection of spinal nerves at the inferior end Provides a two-way conduction pathway to and from the brain 31 pairs of spinal nerves arise from the spinal cord © 2018 Pearson Education, Ltd. Figure 7.19 Anatomy of the spinal cord, posterior view. Cervical Cervical spinal nerves enlargement C8 Dura and Thoracic arachnoid mater spinal nerves Lumbar enlargement T12 End of spinal cord Lumbar Cauda spinal nerves equina L5 End of S1 Sacral meningeal spinal nerves coverings S5 © 2018 Pearson Education, Ltd.  Spinal Cord Gray matter of the spinal cord and spinal roots Internal gray matter is mostly cell bodies Dorsal (posterior) horns house interneurons Receive information from sensory neurons in the dorsal root; cell bodies housed in dorsal root ganglion Anterior (ventral) horns house motor neurons of the somatic (voluntary) nervous system Send information out ventral root Gray matter surrounds the central canal, which is filled with cerebrospinal fluid © 2018 Pearson Education, Ltd.  Spinal Cord White matter of the spinal cord Composed of myelinated fiber tracts Three regions: dorsal, lateral, ventral columns Sensory (afferent) tracts conduct impulses toward brain Motor (efferent) tracts carry impulses from brain to skeletal muscles © 2018 Pearson Education, Ltd. Figure 7.20 Spinal cord with meninges (three-dimensional, anterior view). White matter Dorsal (posterior) Dorsal root Central canal horn of gray matter ganglion Lateral horn of gray matter Spinal nerve Ventral (anterior) Dorsal root of horn of gray matter spinal nerve Ventral root Pia mater of spinal nerve Arachnoid mater Dura mater © 2018 Pearson Education, Ltd. Figure 7.21 Schematic of ascending (sensory) and descending (motor) pathways between the brain and the spinal cord. Interneuron carrying sensory information to cerebral cortex Integration (processing and interpretation of sensory input) Cerebral cortex occurs (gray matter) Interneuron carrying White matter response to Thalamus motor neurons Cerebrum Interneuron carrying response Brain stem to motor neuron Cell body of sensory neuron in sensory ganglion Interneuron carrying Nerve sensory information to Skin cerebral cortex Sensory receptors Cervical spinal cord Muscle White matter Motor output Gray matter Interneuron Motor neuron cell body © 2018 Pearson Education, Ltd.  Peripheral Nervous System (PNS)