Essentials of Anatomy Physiology 4 th Edition Martini

Essentials of Anatomy & Physiology, 4 th Edition Martini / Bartholomew 8 The Nervous System Power. Point® Lecture Outlines prepared by Alan Magid, Duke University Slides 1 to 145 Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Nervous System Two Organ Systems Control All the Other Organ Systems • Nervous system characteristics • Rapid response • Brief duration • Endocrine system characteristics • Slower response • Long duration Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Nervous System Two Anatomical Divisions • Central nervous system (CNS) • • • Brain Spinal cord Peripheral nervous system (PNS) • • • All the neural tissue outside CNS Afferent division (sensory input) Efferent division (motor output) • Somatic nervous system • Autonomic nervous system Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

CENTRAL NERVOUS SYSTEM Information Processing PERIPHERAL Sensory information NERVOUS within SYSTEM afferent division Motor commands within efferent division includes Somatic nervous system Autonomic nervous system Parasympathetic division Receptors Somatic sensory receptors (monitor the outside world and our position in it) Sympathetic division Effectors Visceral sensory receptors (monitor internal conditions and the status of other organ systems) Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Skeletal muscle Smooth muscle Cardiac muscle Glands Adipose tissue Figure 8 -1 1 of 7

PERIPHERAL NERVOUS SYSTEM Receptors Somatic sensory receptors (monitor the outside world and our position in it) Visceral sensory receptors (monitor internal conditions and the status of other organ systems) Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 8 -1 2 of 7

PERIPHERAL Sensory information NERVOUS within SYSTEM afferent division Receptors Somatic sensory receptors (monitor the outside world and our position in it) Visceral sensory receptors (monitor internal conditions and the status of other organ systems) Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 8 -1 3 of 7

CENTRAL NERVOUS SYSTEM Information Processing PERIPHERAL Sensory information NERVOUS within SYSTEM afferent division Receptors Somatic sensory receptors (monitor the outside world and our position in it) Visceral sensory receptors (monitor internal conditions and the status of other organ systems) Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 8 -1 4 of 7

CENTRAL NERVOUS SYSTEM Information Processing PERIPHERAL Sensory information NERVOUS within SYSTEM afferent division Motor commands within efferent division Receptors Somatic sensory receptors (monitor the outside world and our position in it) Visceral sensory receptors (monitor internal conditions and the status of other organ systems) Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 8 -1 5 of 7

CENTRAL NERVOUS SYSTEM Information Processing PERIPHERAL Sensory information NERVOUS within SYSTEM afferent division Motor commands within efferent division includes Somatic nervous system Receptors Somatic sensory receptors (monitor the outside world and our position in it) Effectors Visceral sensory receptors (monitor internal conditions and the status of other organ systems) Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Skeletal muscle Figure 8 -1 6 of 7

CENTRAL NERVOUS SYSTEM Information Processing PERIPHERAL Sensory information NERVOUS within SYSTEM afferent division Motor commands within efferent division includes Somatic nervous system Autonomic nervous system Parasympathetic division Receptors Somatic sensory receptors (monitor the outside world and our position in it) Sympathetic division Effectors Visceral sensory receptors (monitor internal conditions and the status of other organ systems) Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Skeletal muscle Smooth muscle Cardiac muscle Glands Adipose tissue Figure 8 -1 7 of 7

Neural Tissue Organization Two Classes of Neural (Nerve) Cells • Neurons • For information transfer, processing, and storage • Neuroglia • Supporting framework for neurons • Phagocytes Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Neural Tissue Organization Three Classes of Neurons • Sensory neurons • Deliver information to CNS • Motor neurons • Stimulate or inhibit peripheral tissues • Interneurons (association neurons) • Located between sensory and motor neurons • Analyze inputs, coordinate outputs Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Neural Tissue Organization Neuron Anatomy • Cell body • Nucleus • Mitochondria, RER, other organelles • Dendrites • Several branches • Signal reception (inward) • Axon • Signal propagation (outward) Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Neural Tissue Organization The Anatomy of a Representative Neuron Figure 8 -2

Neural Tissue Organization Structural Classes of Neurons • Unipolar • Dendrite, axon continuous • Afferent neurons • Multipolar • Many dendrites, one axon • Most common class of neuron • Bipolar • One dendrite, one axon • Very rare Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Neuron Function A Structural Classification of Neurons Figure 8 -3

Neural Tissue Organization Types of Neuroglia (glia) • Astrocytes • Part of blood-brain barrier • Oligodendrocytes • Responsible for myelination • Microglia • Phagocytic defense cells • Ependymal cells • Lining of brain, spinal cord cavities • Source of cerebrospinal fluid Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Neural Tissue Organization Neuroglia in the CNS Figure 8 -4

Neural Tissue Organization Two Types of Neuroglia in the PNS • Satellite cells • Surround cell bodies • Schwann cells • Surround all peripheral axons • Form myelin sheath on myelinated axons Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Neural Tissue Organization Schwann Cells and Peripheral Axons Figure 8 -5

Neural Tissue Organization Key Note Neurons perform all of the communication, information processing, and control functions of the nervous system. Neuroglia outnumber neurons and have functions essential to preserving the physical and biochemical structure of neural tissue and the survival of neurons. Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Neural Tissue Organization Anatomic Organization of CNS Neurons • Center—Collection of neurons with a shared function • Nucleus—A center with a discrete anatomical boundary • Neural cortex—Gray matter covering of brain portions • White matter—Bundles of axons (tracts) that share origins, destinations, and functions Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Neural Tissue Organization Anatomic Organization of PNS Neurons • Ganglia—Groupings of neuron cell bodies • Nerve—Bundle of axons supported by connective tissue • Spinal nerves • To/from spinal cord • Cranial nerves • To/from brain Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Neural Tissue Organization The Anatomical Organization of the Nervous System Figure 8 -6

Neural Tissue Organization Pathways in the CNS • Ascending pathways Carry information from sensory receptors to processing centers in the brain • Descending pathways Carry commands from specialized CNS centers to skeletal muscles Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Neuron Function The Membrane Potential • Resting potential • Excess negative charge inside the neuron • Created and maintained by Na-K ion pump • Negative voltage (potential) inside • -70 m. V (0. 07 Volts) Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Neuron Function The Cell Membrane at the Resting Potential Figure 8 -7

Neuron Function Changes in Membrane Potential • • Result from changes in ion movement Ions move in transmembrane channels Membrane channels can open or close If Na+ channels open positive charges enter cell membrane potential moves positive (depolarization) • If K+ channels open positive charges leave cell membrane potential moves negative (hyperpolarization) Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Neuron Function Key Note A membrane potential exists across the cell membrane because (1) the cytosol and the extracellular fluid differ in their ionic composition, and (2) the cell membrane is selectively permeable to these ions. The membrane potential can quickly change, as the ionic permeability of the cell membrane changes, in response to chemical or physical stimuli. Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Neuron Function Generation of Action Potential • • • Depolarization of membrane to threshold Rapid opening of voltage-gated Na+ channels Na+ entry causes rapid depolarization Voltage-gated K+ channels open K+ exit causes rapid repolarization Refractory period ends as membrane recovers the resting state Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Depolarization to threshold Activation of voltageregulated sodium channels and rapid depolarization Sodium ions Local current Potassium ions Inactivation of sodium channels and activation of voltage-regulated potassium channels Transmembrane potential (m. V) +30 DEPOLARIZATION 3 REPOLARIZATION 0 2 _ 60 _ 70 The return to normal permeability and resting state Threshold 1 4 Resting potential REFRACTORY PERIOD 0 1 2 Time (msec) 3 Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 8 -8 1 of 5

Depolarization to threshold Sodium ions Local current Transmembrane potential (m. V) +30 DEPOLARIZATION 0 _ 60 _ 70 Threshold 1 Resting potential 0 1 2 Time (msec) 3 Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 8 -8 2 of 5

Depolarization to threshold Activation of voltageregulated sodium channels and rapid depolarization Sodium ions Local current Potassium ions Transmembrane potential (m. V) +30 DEPOLARIZATION 0 2 _ 60 _ 70 Threshold 1 Resting potential 0 1 2 Time (msec) 3 Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 8 -8 3 of 5

Depolarization to threshold Activation of voltageregulated sodium channels and rapid depolarization Sodium ions Local current Potassium ions Inactivation of sodium channels and activation of voltage-regulated potassium channels Transmembrane potential (m. V) +30 DEPOLARIZATION 3 REPOLARIZATION 0 2 _ 60 _ 70 Threshold 1 Resting potential 0 1 2 Time (msec) 3 Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 8 -8 4 of 5

Depolarization to threshold Activation of voltageregulated sodium channels and rapid depolarization Sodium ions Local current Potassium ions Inactivation of sodium channels and activation of voltage-regulated potassium channels Transmembrane potential (m. V) +30 DEPOLARIZATION 3 REPOLARIZATION 0 2 _ 60 _ 70 The return to normal permeability and resting state Threshold 1 4 Resting potential REFRACTORY PERIOD 0 1 2 Time (msec) 3 Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 8 -8 5 of 5

Neuron Function Propagation of an Action Potential • Continuous propagation • Involves entire membrane surface • Proceeds in series of small steps (slower) • Occurs in unmyelinated axons • Saltatory propagation • Involves patches of membrane exposed at nodes • Proceeds in series of large steps (faster) • Occurs in myelinated axons Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Neuron Function The Propagation of Action Potentials over Unmyelinated and Myelinated Axons Figure 8 -9(a)

Neuron Function The Propagation of Action Potentials over Unmyelinated and Myelinated Axons Figure 8 -9(b)

Neuron Function Action Potential Propagation PLAY Neurophysiology: Continuous Saltatory Propagation Neurophysiology: Action Potential Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Neuron Function Key Note “Information” travels within the nervous system primarily in the form of propagated electrical signals known as action potentials. The most important information (e. g. , vision, balance, movement), is carried by myelinated axons. Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Neural Communication Synapse Basics • Intercellular communication • Axon terminal • Input to next cell • Chemical signaling • Neurotransmitter release Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Neural Communication Structure of a Synapse • Presynaptic components • Axon terminal • Synaptic knob • Synaptic vesicles • Synaptic cleft • Postsynaptic components • Neurotransmitter receptors Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Neural Communication The Structure of a Typical Synapse Figure 8 -10

Neural Communication Synaptic Function and Neurotransmitters • Cholinergic synapses • Release neurotransmitter acetylcholine • Enzyme in synaptic cleft (acetylcholinesterase) breaks it down • Adrenergic synapses • Release neurotransmitter norepinephrine • Dopaminergic synapses • Release neurotransmitter dopamine PLAY Neurophysiology: Synapse Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

An action potential arrives and depolarizes the synaptic knob PRESYNAPTIC NEURON Synaptic vesicles ER Extracellular Ca 2+ enters the synaptic cleft triggering the exocytosis of ACh Action potential EXTRACELLULAR FLUID ACh Synaptic knob Ca 2+ Synaptic cleft Ca 2+ ACh. E CYTOSOL Chemically regulated sodium channels POSTSYNAPTIC NEURON ACh is removed by ACh. E (acetylcholinesterase) ACh binds to receptors and depolarizes the postsynaptic membrane Initiation of action potential if threshold is reached Propagation of action potential (if generated) Na 2+ Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Na 2+ Receptor Figure 8 -11 1 of 5

An action potential arrives and depolarizes the synaptic knob PRESYNAPTIC NEURON Synaptic vesicles ER Action potential EXTRACELLULAR FLUID Synaptic knob ACh. E CYTOSOL POSTSYNAPTIC NEURON Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 8 -11 2 of 5

An action potential arrives and depolarizes the synaptic knob PRESYNAPTIC NEURON Synaptic vesicles ER Extracellular Ca 2+ enters the synaptic cleft triggering the exocytosis of ACh Action potential EXTRACELLULAR FLUID ACh Synaptic knob Ca 2+ Synaptic cleft Ca 2+ ACh. E CYTOSOL POSTSYNAPTIC NEURON Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Chemically regulated sodium channels Figure 8 -11 3 of 5

An action potential arrives and depolarizes the synaptic knob PRESYNAPTIC NEURON Synaptic vesicles ER Extracellular Ca 2+ enters the synaptic cleft triggering the exocytosis of ACh Action potential EXTRACELLULAR FLUID ACh Synaptic knob Ca 2+ Synaptic cleft Ca 2+ ACh. E CYTOSOL Chemically regulated sodium channels POSTSYNAPTIC NEURON ACh binds to receptors and depolarizes the postsynaptic membrane Initiation of action potential if threshold is reached Na 2+ Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Na 2+ Receptor Figure 8 -11 4 of 5

An action potential arrives and depolarizes the synaptic knob PRESYNAPTIC NEURON Synaptic vesicles ER Extracellular Ca 2+ enters the synaptic cleft triggering the exocytosis of ACh Action potential EXTRACELLULAR FLUID ACh Synaptic knob Ca 2+ Synaptic cleft Ca 2+ ACh. E CYTOSOL Chemically regulated sodium channels POSTSYNAPTIC NEURON ACh is removed by ACh. E (acetylcholinesterase) ACh binds to receptors and depolarizes the postsynaptic membrane Initiation of action potential if threshold is reached Propagation of action potential (if generated) Na 2+ Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Na 2+ Receptor Figure 8 -11 5 of 5

Neural Communication • Neuronal pools Groups of interconnected interneurons with specific functions • Divergence Spread of information from one neuron to several others • Convergence Several neurons send information to one other Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Neural Communication Two Common Types of Neuronal Pools Figure 8 -12

Neural Communication Key Note A synaptic terminal releases a neurotransmitter that binds to the postsynaptic cell membrane. The result is a brief, local change in the permeability of the postsynaptic cell. Many drugs affect the nervous system by stimulating neurotransmitter receptors and thus produce complex effects on perception, motor control, and emotions. Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Central Nervous System Meninges—Layers that surround and protect the brain and spinal cord (CNS) • Dura mater (“tough mother”) • Tough, fibrous outer layer • Epidural space above dura of spinal cord • Arachnoid (“spidery”) • Subarchnoid space • Cerebrospinal fluid • Pia mater (“delicate mother”) • Thin inner layer Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Central Nervous System The Meninges Figure 8 -13(a)

The Central Nervous System The Meninges Figure 8 -13(b)

The Central Nervous System Spinal Cord Basics • Relays information to/from brain • Processes some information on its own • Divided into 31 segments • Each segment has a pair of: • Dorsal root ganglia • Dorsal roots • Ventral roots • Gray matter appears as horns • White matter organized into columns Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Central Nervous System Gross Anatomy of the Spinal Cord Figure 8 -14(a)

The Central Nervous System Gross Anatomy of the Spinal Cord Figure 8 -14(b)

The Central Nervous System Sectional Anatomy of the Spinal Cord Figure 8 -15(a)

The Central Nervous System Sectional Anatomy of the Spinal Cord Figure 8 -15(b)

The Central Nervous System Key Note The sensory and motor nuclei (gray matter) of the spinal cord surround the central canal. Sensory nuclei are dorsal, motor nuclei are ventral. A thick layer of white matter consisting of ascending and descending axons covers the gray matter. These axons are organized into columns of axon bundles with specific functions. This highly organized structure often enables predicting the impact of particular injuries. Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Central Nervous System Brain Regions • • • Cerebrum Diencephalon Midbrain Pons Medulla oblongata Cerebellum Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Central Nervous System The Brain Figure 8 -16(a)

The Central Nervous System The Brain Figure 8 -16(b)

The Central Nervous System The Brain Figure 8 -16(c)

The Central Nervous System Brain—The four hollow chambers in the center of the brain filled with cerebrospinal fluid (CSF) • CSF produced by choroid plexus • CSF circulates • From ventricles and central canal • To subarachoid space • Accessible by lumbar puncture • To blood stream Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Central Nervous System The Ventricles of the Brain Figure 8 -17

The Central Nervous System The Formation and Circulation of Cerebrospinal Fluid Figure 8 -18(a)

The Central Nervous System The Formation and Circulation of Cerebrospinal Fluid Figure 8 -18(b)

The Central Nervous System Functions of the Cerebrum • • Conscious thought Intellectual activity Memory Origin of complex patterns of movement Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Central Nervous System Anatomy of Cerebral Cortex • Highly folded surface • Elevated ridges (gyri) • Shallow depressions (sulci) • Cerebral Hemispheres • Longitudinal fissure • Central sulcus • Boundary between frontal and parietal lobes • Other lobes (temporal, occipital) Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Central Nervous System Functions of the Cerebral Cortex • Hemispheres serve opposite body sides • Primary motor cortex (precentral gyrus) • Directs voluntary movement • Primary sensory cortex (postcentral gyrus) • Receives somatic sensation (touch, pain, pressure, temperature) • Association areas • Interpret sensation • Coordinate movement Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Central Nervous System The Surface of the Cerebral Hemispheres Figure 8 -19

The Central Nervous System Hemispheric Lateralization • Categorical hemisphere (usually left) • General interpretative and speech centers • Language-based skills • Representational Hemisphere (usually right) • Spatial relationships • Logical analysis Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Central Nervous System Hemispheric Lateralization Figure 8 -20

The Central Nervous System Brain Waves (Electroencephalogram) Figure 8 -21

The Central Nervous System The Basal Nuclei • Lie deep within central white matter of the brain • Responsible for muscle tone • Coordinate learned movements • Coordinate rhythmic movements (e. g. , walking) Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Central Nervous System The Basal Nuclei Figure 8 -22(a)

The Central Nervous System The Basal Nuclei Figure 8 -22(b)

The Central Nervous System Functions of the Limbic System • Establish emotions and related drives (i. e. rage, fear, sexual arousal) • Link conscious, intellectual functions of cerebral cortex to brain stem’s autonomic functions • Store and retrieve long-term memories • Functional grouping of structures rather than an anatomical one Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Central Nervous System The Limbic System Figure 8 -23

The Central Nervous System The Diencephalon • Switching and relay center • Integration of conscious and unconscious motor and sensory pathways • Components include: • Epithalamus • Choroid plexus • Pineal body • Thalamus • Hypothalamus Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Central Nervous System The Diencephalon and Brain Stem Figure 8 -24(a)

The Central Nervous System The Diencephalon and Brain Stem Figure 8 -24(b)

The Central Nervous System Functions of the Epithalamus • Anterior portion contains choroid complex • Posterior portion contains pineal gland

The Central Nervous System Functions of the Thalamus • Relay and filter all ascending (sensory) information • Relay a small proportion to cerebral cortex (conscious perception) • Relay most to basal nuclei and brain stem centers • Coordinate voluntary and involuntary motor behavior Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Central Nervous System Functions of the Hypothalamus • Produce emotions and behavioral drives • Coordinate nervous and endocrine systems • Secrete hormones • Coordinate voluntary and autonomic functions • Regulate body temperature Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Central Nervous System Anatomy and Function of the Brain Stem • Midbrain • Process visual, auditory information • Generate involuntary movements • Pons • Links to cerebellum • Involved in control of movement • Medulla oblongata • Relay sensory information • Regulate autonomic function Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Central Nervous System Anatomy and Function of the Cerebellum • Oversees postural muscles & stores patterns of movement • Fine tunes most movements controlled at conscious and subconscious levels • Links to brain stem, cerebrum, spinal cord • Communicates over cerebellar peduncles Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Central Nervous System Functions of the Medulla Oblongata • Links brain and spinal cord • Relays ascending information to cerebral cortex • Controls crucial organ systems by reflex • Cardiovascular centers • Respiratory rhythmicity centers Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Central Nervous System Key Note The brain, a large mass of neural tissue, contains internal passageways and chambers filled with CSF. The six major regions of the brain have specific functions. As you ascend from the medulla oblongata to the cerebrum, those functions become more complex and variable. Conscious thought and intelligence are provided by the cerebral cortex. Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Peripheral Nervous System PNS Basics • Links the CNS with the body • Carries all sensory information and motor commands • Axons bundled in nerves • Cell bodies grouped into ganglia • Includes cranial and spinal nerves Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Central Nervous System Gross Anatomy of the Spinal Cord Figure 8 -14(b)

The Peripheral Nervous System The Cranial Nerves • 12 Pairs • Connect to brain not the cord • Olfactory (I) • Sense of smell • Optic (II) • Sense of vision • Oculomotor (III) • Eye movement Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Peripheral Nervous System The Cranial Nerves (continued) • Trochlear (IV) • Eye movement • Trigeminal (V) • Eye, jaws sensation/movement • Abducens (VI) • Eye movement • Facial (VII) • Face, scalp, tongue sensation/movement • Vestibulocochlear (VIII) • Hearing, balance Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Peripheral Nervous System The Cranial Nerves (continued) • Glossopharyngeal (IX) • Taste, swallowing • Vagus (X) • Autonomic control of visceral organs • Accessory (XI) • Swallowing, pectoral girdle movement • Hypoglossal (XII) • Tongue movement Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Peripheral Nervous System The Cranial Nerves Figure 8 -25(a)

The Peripheral Nervous System The Cranial Nerves Figure 8 -25(b)

The Peripheral Nervous System Key Note The 12 pairs of cranial nerves are responsible for the special senses of smell, sight, and hearing/balance, and control movement of the eye, jaw, face, tongue, and muscles of the neck, back, and shoulders. They also provide sensation from the face, neck, and upper chest and autonomic innervation to thoracic and abdominopelvic organs. Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Peripheral Nervous System The Spinal Nerves • 31 Pairs • 8 Cervical • 12 Thoracic • 5 Lumbar • 5 Sacral • Dermatome—Region of the body surface monitored by a pair of spinal nerves Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Peripheral Nervous System Nerve Plexus—A complex, interwoven network of nerves • Four Large Plexuses • Cervical plexus • Brachial plexus • Lumbar plexus • Sacral plexus * The lumbar and sacral plexuxes are sometimes referred to as lumbosacral plexus. Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Peripheral Nervous System Peripheral Nerves and Nerve Plexuses Figure 8 -26

The Peripheral Nervous System Dermatomes Figure 8 -27

The Peripheral Nervous System Reflex—An automatic involuntary motor response to a specific stimulus • The 5 steps in a reflex arc • Arrival of stimulus and activation of receptor • Activation of sensory neuron • CNS processing of information • Activation of motor neuron • Response by effector (muscle or gland) Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Arrival of stimulus and activation of receptor Activation of a sensory neuron Receptor Sensation relayed to the brain by collateral Dorsal root REFLEX ARC Stimulus Effector Response by effector Ventral root Activation of a motor neuron Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Information processing in CNS KEY Sensory neuron (stimulated) Excitatory interneuron Motor neuron (stimulated) Figure 8 -27 1 of 6

Arrival of stimulus and activation of receptor Stimulus Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 8 -27 2 of 6

Arrival of stimulus and activation of receptor Activation of a sensory neuron Dorsal root Receptor Stimulus KEY Sensory neuron (stimulated) Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 8 -27 3 of 6

Arrival of stimulus and activation of receptor Activation of a sensory neuron Sensation relayed to the brain by collateral Dorsal root Receptor Stimulus Information processing in CNS KEY Sensory neuron (stimulated) Excitatory interneuron Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 8 -27 4 of 6

Arrival of stimulus and activation of receptor Activation of a sensory neuron Receptor Sensation relayed to the brain by collateral Dorsal root REFLEX ARC Stimulus Ventral root Activation of a motor neuron Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Information processing in CNS KEY Sensory neuron (stimulated) Excitatory interneuron Motor neuron (stimulated) Figure 8 -27 5 of 6

Arrival of stimulus and activation of receptor Activation of a sensory neuron Receptor Sensation relayed to the brain by collateral Dorsal root REFLEX ARC Stimulus Effector Response by effector Ventral root Activation of a motor neuron Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Information processing in CNS KEY Sensory neuron (stimulated) Excitatory interneuron Motor neuron (stimulated) Figure 8 -27 6 of 6

The Peripheral Nervous System Examples of Reflexes • Monosynaptic reflex—Simplest reflex arc; sensory neuron synapses directly on motor neuron • Stretch reflex—Monosynaptic reflex to regulate muscle length and tension (example: patellar reflex) • Muscle spindle—Sensory receptor in a muscle that stimulates the stretch reflex Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Stretching of muscle tendon stimulates muscle spindles Stretch Muscle spindle (stretch receptor) Spinal cord REFLEX ARC Contraction Activation of motor neuron produces reflex muscle contraction Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 8 -29 1 of 3

Stretching of muscle tendon stimulates muscle spindles Stretch Muscle spindle (stretch receptor) Spinal cord Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 8 -29 2 of 3

Stretching of muscle tendon stimulates muscle spindles Stretch Muscle spindle (stretch receptor) Spinal cord REFLEX ARC Contraction Activation of motor neuron produces reflex muscle contraction Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 8 -29 3 of 3

The Peripheral Nervous System Polysynaptic reflex—A reflex arc with at least one interneuron between the sensory afferent and motor efferent • Has a longer delay than a monosynaptic reflex (more synapses) • Can produce more complex response • Example: flexor reflex, a withdrawal reflex • Brain can modify spinal reflexes Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Peripheral Nervous System The Flexor Reflex, a Type of Withdrawal Reflex Figure 8 -30

The Peripheral Nervous System Key Note Reflexes are rapid, automatic responses to stimuli that “buy time” for the planning and execution of more complex responses that are often consciously directed. Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Autonomic Nervous System Branch of nervous system that coordinates cardiovascular, digestive, excretory, and reproductive functions Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Autonomic Nervous System Anatomy of ANS • Preganglionic neuron • Cell body resides in CNS • Axon synapses in PNS in autonomic ganglion • Postganglionic axons (postganglionic fibers) synapse on peripheral effectors • Cardiac muscle • Smooth muscle • Glands • Adipose tissues Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Autonomic Nervous System Divisions of the ANS • Sympathetic division • Preganglionic neurons in the thoracic and lumbar segments of the spinal cord • “Fight or flight” system • Parasympathetic division • Preganglionic neurons in the brain and sacral segments • “Rest and repose” system Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Autonomic Nervous System Key Note The two divisions of the ANS operate largely without our awareness. The sympathetic division increases alertness, metabolic rate, and muscular abilities; the parasympathetic division reduces metabolic rate and promotes visceral activities such as digestion. Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Autonomic Nervous System Effects of Parasympathetic Activation • • Relaxation Food processing Energy absorption Brief effects at specific sites Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

The Autonomic Nervous System Relationship between the Two Divisions • Sympathetic division reaches visceral and somatic structures throughout the body • Parasympathetic division reaches only visceral structures via cranial nerves or in the abdominopelvic cavity • Many organs receive dual innervation • In general, the two divisions produce opposite effects on their target organs Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings

Aging and the Nervous System Age-Related Changes • • Reduction in brain size and weight Loss of neurons Decreased brain blood flow Changes in synaptic organization of the brain • Intracellular and extracellular changes in CNS neurons Copyright © 2007 Pearson Education, Inc. , publishing as Benjamin Cummings