Essentials of Human Anatomy & Physiology - Chapter 7: The Nervous System PDF

Essentials of Human Anatomy & Physiology Seventh Edition Elaine N. Marieb Chapter 7 The Nervous System Slides 7.1 – 7.102 Lecture Slides in PowerPoint by Jerry L. Coo...

Essentials of Human Anatomy & Physiology Seventh Edition Elaine N. Marieb Chapter 7 The Nervous System Slides 7.1 – 7.102 Lecture Slides in PowerPoint by Jerry L. Cook Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Functions of the Nervous System  Sensory input – gathering information  To monitor changes occurring inside and outside the body  Changes = stimuli  Integration  To process and interpret sensory input and decide if action is needed  Motor output  A response to integrated stimuli  The response activates muscles or glands Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.2  Structural Classification of the Nervous System  Central nervous system (CNS)  Brain and Spinal cord  Acts as integrating and command center – interpret incoming sensory information and issue instructions based on past experiences and current conditions  Peripheral nervous system (PNS)  Nerves outside the brain and spinal cord  Link all parts of the body by carrying impulses to the CNS and back Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.3  Functional Classification of the Peripheral Nervous System  Sensory (afferent) division  Nerve fibers that carry information to the central nervous system Figure 7.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.4  Functional Classification of the Peripheral Nervous System  Motor (efferent) division  Nerve fibers that carry impulses away from the central nervous system Figure 7.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.5  Functional Classification of the Peripheral Nervous System  Motor (efferent) division  Two subdivisions  Somatic nervous system = voluntary nervous system  Skeletal muscle reflexes such as stretch reflex are initiated involuntarily by same fibers  Autonomic nervous system = involuntary nervous system  Sympathetic and parasympathetic divisions Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.6  Organization of the Nervous System Figure 7.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.7  Nervous Tissue: Support Cells (Neuroglia) - glia  Astrocytes  Abundant, star-shaped cells  Brace neurons  Form barrier between capillaries and neurons and make exchanges between Figure 7.3a the two  Control the chemical environment of the brain by capturing ions and neurotransmitters Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.8  Nervous Tissue: Support Cells  Microglia  Spider-like phagocytes  Dispose of debris – dead cells and bacteria  Ependymal cells  Line cavities of the brain and spinal cord  Circulate cerebrospinal fluid with cilia Figure 7.3b, c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.9  Nervous Tissue: Support Cells  Oligodendrocytes  Wrap their flat extensions tightly around the nerve fibers  Produce myelin sheath around nerve fibers in the central Figure 7.3d nervous system Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.10  Nervous Tissue: Support Cells  Satellite cells  Protect neuron cell bodies  Schwann cells  Form myelin sheath in the peripheral nervous system  Neuroglia are not able to transmit nerve impulses but do not lose their ability to divide, unlike neurons Figure 7.3e Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.11  Nervous Tissue: Neurons  Neurons = nerve cells  Cells specialized to transmit messages  Major regions of neurons  Cell body – nucleus and metabolic center of the cell  Processes – fibers that extend from the cell body Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.12  Neuron Anatomy  Cell body  Nissl substance – specialized rough endoplasmic reticulum  Neurofibrils – intermediate cytoskeleton that maintains cell shape Figure 7.4a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.13  Neuron Anatomy  Cell body  Nucleus  Large nucleolus Figure 7.4a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.14  Neuron Anatomy  Extensions outside the cell body  Dendrites – conduct impulses toward the cell body  Axons – conduct impulses away from the cell body Figure 7.4a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.15  Axons and Nerve Impulses  Axons end in axonal terminals  Axonal terminals contain vesicles with neurotransmitters  Axonal terminals are separated from the next neuron by a gap  Synaptic cleft – gap between adjacent neurons  Synapse – junction between nerves Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.16  Nerve Fiber Coverings  Schwann cells – produce myelin sheaths in jelly-roll like fashion  Nodes of Ranvier – gaps in myelin sheath along the axon Figure 7.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.17  Neuron Cell Body Location  Most are found in the central nervous system in clusters called nuclei  Bundles of nerve fibers in CNS = tracts  Gray matter – cell bodies and unmyelinated fibers  White matter – myelinated fibers  Bundles of nerve fibers in PNS = nerves  Ganglia – collections of cell bodies outside the central nervous system Slide 7.18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Functional Classification of Neurons  Sensory (afferent) neurons  Cell bodies in a ganglion outside the CNS  Carry impulses from the sensory receptors to CNS  Cutaneous (skin) sense organs  Proprioceptors – detect stretch or tension in muscles, tendons, joints  Motor (efferent) neurons  Cell bodies found in the CNS  Carry impulses from the central nervous system Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.19  Functional Classification of Neurons  Interneurons (association neurons)  Found in neural pathways in the central nervous system  Cell bodies in the CNS  Connect sensory and motor neurons Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.20  Neuron Classification Figure 7.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.21  Structural Classification of Neurons  Multipolar neurons – many extensions from the cell body Figure 7.8a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.22  Structural Classification of Neurons  Bipolar neurons – one axon and one dendrite  Rare in adults – in eye and ear only Figure 7.8b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.23  Structural Classification of Neurons  Unipolar neurons – have a short, single process leaving the cell body  Axon conducts nerve impulses both to and from the cell body Figure 7.8c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.24  Functional Properties of Neurons  Two main functions  Irritability – ability to respond to stimuli  Conductivity – ability to transmit an impulse  The plasma membrane at rest is polarized  Fewer positive ions (usually K+) are inside the cell than outside the cell (usually Na+) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.25  Starting a Nerve Impulse  Depolarization – a stimulus depolarizes the neuron’s membrane  A deploarized membrane allows sodium (Na+) to flow inside the membrane  The exchange of ions initiates an action potential (nerve impulse) in the neuron Figure 7.9a–c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.26  The Action Potential  If the action potential (nerve impulse) starts, it is propagated over the entire axon – all-or-none response  Potassium ions rush out of the neuron after sodium ions rush in, which repolarizes the membrane  The sodium-potassium pump restores the original configuration  This action requires ATP  Until repolarization occurs, a neuron cannot conduct another impulse Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.27  Nerve Impulse Propagation  The impulse continues to move toward the cell body  Impulses travel faster when fibers have a myelin sheath  Nerve impulse literally jumps from node to node because it cannot cross myelin insulation Figure 7.9c–e Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.28  Continuation of the Nerve Impulse between Neurons  Impulses are unable to cross the synapse to another nerve  Neurotransmitter is released from a nerve’s axon terminal  The dendrite of the next neuron has receptors that are stimulated by the neurotransmitter  An action potential is started in the dendrites of the next neuron  Transmission of an impulse is an electrochemical event Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.29  How Neurons Communicate at Synapses Figure 7.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.30  The Reflex Arc  Reflex – rapid, predictable, and involuntary responses to stimuli  Reflex arc – direct route from a sensory neuron, to an interneuron, to an effector Figure 7.11a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.31  Simple Reflex Arc Figure 7.11b, c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.32  Types of Reflexes and Regulation  Autonomic reflexes  Smooth muscle regulation  Size of eye pupils  Heart and blood pressure regulation  Regulation of glands and sweating  Digestive system and elimination regulation  Somatic reflexes  Activation of skeletal muscles Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.33  Types of Reflexes and Regulation  Reflex arcs have a minimum five elements  A sensory receptor – reacts to stimuli  An effector receptor – muscle or gland stimulated  Afferent and efferent neurons connecting the two  The CNS integration center Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.34  Central Nervous System (CNS)  CNS develops from the embryonic neural tube – a simple tube  The neural tube becomes the brain and spinal cord  The opening of the neural tube becomes the ventricles  Four chambers within the brain  Filled with cerebrospinal fluid Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.35  Regions of the Brain  Cerebral hemispheres  Diencephalon  Brain stem  Cerebellum Figure 7.12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.36  Cerebral Hemispheres (Cerebrum)  Paired (left and right) superior parts of the brain  Include more than half of the brain mass Figure 7.13a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.37  Cerebral Hemispheres (Cerebrum)  The surface is made of elevated ridges (gyri) and shallow grooves (sulci) Figure 7.13a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.38  Lobes of the Cerebrum  Fissures (deep grooves) divide the cerebrum into lobes  Surface lobes of the cerebrum – named for cranial bone over them  Frontal lobe  Parietal lobe  Occipital lobe  Temporal lobe Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.39  Lobes of the Cerebrum Figure 7.15a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.40  Specialized Areas of the Cerebrum  Somatic sensory area in parietal lobe – receives impulses from the body’s sensory receptors (except special senses)  Occipital lobe – vision and temporal lobe – auditory  Primary motor area – sends impulses to skeletal muscles – frontal lobe  Broca’s area – involved in our ability to speak – base of the precentral gyrus Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.41  Sensory and Motor Areas of the Cerebral Cortex Figure 7.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.42  Specialized Area of the Cerebrum  Cerebral areas involved in special senses  Gustatory area (taste)  Visual area  Auditory area  Olfactory area Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.43  Specialized Area of the Cerebrum  Interpretation areas of the cerebrum  Speech/language region  Language comprehension region  General interpretation area Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.44  Specialized Area of the Cerebrum Figure 7.13c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.45  Layers of the Cerebrum  Gray matter  Outermost layer  Composed mostly of neuron cell bodies  Cerebral cortex Figure 7.13a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.46  Layers of the Cerebrum  White matter  Fiber tracts inside the gray matter  Example: corpus callosum connects hemispheres Figure 7.13a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.47  Layers of the Cerebrum  Basal nuclei – internal islands of gray matter  Helps regulate voluntary motor activities by modifying instructions sent to the skeletal muscles Figure 7.13a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.48  Diencephalon - interbrain  Sits on top of the brain stem  Enclosed by the cerebral hemispheres  Made of three parts  Thalamus  Hypothalamus  Epithalamus Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.49  Diencephalon Figure 7.15 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.50  Thalamus  Surrounds the third ventricle of the brain  The relay station for sensory impulses passing upward to the sensory cortex  Transfers impulses to the correct part of the cortex for localization and interpretation Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.51  Hypothalamus  Under the thalamus  Important autonomic nervous system center  Helps regulate body temperature  Controls water balance  Regulates metabolism Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.52  Hypothalamus  An important part of the limbic system (emotions) – emotional-visceral brain  The pituitary gland is attached to and regulated by the hypothalamus Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.53  Epithalamus  Forms the roof of the third ventricle  Houses the pineal body (an endocrine gland)  Includes the choroid plexus – forms cerebrospinal fluid Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.54  Brain Stem  Attaches to the spinal cord  Parts of the brain stem  Midbrain  Pons  Medulla oblongata Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.55  Brain Stem Figure 7.15a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.56  Midbrain  Mostly composed of tracts of nerve fibers  The cerebral aqueduct – canal that connects the 3rd ventricle of the diencephalon to the 4th ventricle  Has two bulging fiber tracts – cerebral peduncles – convey ascending and descending impulses  Has four rounded protrusions – corpora quadrigemina – Reflex centers for vision and hearing Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.57  Pons  The bulging center part of the brain stem  Mostly composed of fiber tracts  Includes nuclei involved in the control of breathing Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.58  Medulla Oblongata  The lowest part of the brain stem  Merges into the spinal cord  Includes important fiber tracts  Contains important control centers  Heart rate control  Blood pressure regulation  Breathing  Swallowing  Vomiting Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.59  Reticular Formation  Diffuse mass of gray matter along the brain stem  Involved in motor control of visceral organs  Reticular activating system plays a role in awake/sleep cycles and consciousness  Damage here results in a permanent coma Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.60  Reticular Formation Figure 7.15b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.61  Cerebellum  Two hemispheres with convoluted surfaces  Provides involuntary coordination of body movements – of skeletal muscles, balance and equilibrium  Automatic pilot – continually comparing brain’s intentions with actual body performance Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.62  Cerebellum Figure 7.15a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.63  Protection of the Central Nervous System  Scalp and skin  Cerebrospinal fluid  Skull and vertebral  Blood brain barrier column  Meninges Figure 7.16a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.64  Meninges  Dura mater  Double-layered external covering the brain  Periosteum – attached to surface of the skull  Meningeal layer – outer covering of the brain and continues as the dura matter of the spinal cord Folds inward in several areas that attaches the brain to cranial cavity Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.65  Meninges  Arachnoid layer  Middle layer that is web-like  Pia mater  Internal layer that clings to the surface of the brain following every fold  Subarachnoid space filled with cerebrospinal fluid  Arachnoid villi – projections of arachnoid membrane protruding through the dura matter Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.66  Cerebrospinal Fluid  Similar to blood plasma composition  Less protein, more vitamin C, different ions  Formed by the choroid plexus  Forms a watery cushion to protect the brain  Circulated in arachnoid space, ventricles, and central canal of the spinal cord Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.67  Ventricles and Location of the Cerebrospinal Fluid Figure 7.17a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.68  Ventricles and Location of the Cerebrospinal Fluid Figure 7.17b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.69  Blood Brain Barrier  Includes the least permeable capillaries of the body – only H2O, glucose, and essential amino acids get through  Excludes many potentially harmful substances  Useless against some substances  Fats and fat soluble molecules  Respiratory gases  Alcohol  Nicotine  Anesthesia Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.70  Traumatic Brain Injuries  Concussion  Slight brain injury – dizzy or lose consciousness briefly  No permanent brain damage  Contusion  Nervous tissue destruction occurs - does not regenerate  If cortex is damaged, coma for hours or life  Cerebral edema  Swelling from the inflammatory response  May compress and kill brain tissue Slide 7.71 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Cerebrovascular Accident (CVA)  Commonly called a stroke  The result of a clot or a ruptured blood vessel supplying a region of the brain  Brain tissue supplied with oxygen from that blood source dies  Loss of some functions or death may result Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.72  Alzheimer’s Disease  Progressive degenerative brain disease  Mostly seen in the elderly, but may begin in middle age  Structural changes in the brain include abnormal protein deposits and twisted fibers within neurons  Victims experience memory loss, irritability, confusion and ultimately, hallucinations and death Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.73  Spinal Cord  Extends from the medulla oblongata to the region of T12  Below T12 is the cauda equina (a collection of spinal nerves)  Enlargements occur in the cervical and lumbar regions Figure 7.18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.74  Spinal Cord Anatomy  Internal gray matter - mostly cell bodies that surround the central canal of the cord  Dorsal (posterior) horns  Anterior (ventral) horns  Contains motor neurons of the somatic nervous system, which send their axons out the ventral root  Together they fuse to form the spinal nerves  Nerves leave at the level of each vertebrae Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.75  Spinal Cord Anatomy  Cell bodies of sensory neurons, whose fibers enter the cord by the dorsal root, are found in an enlarged area called the dorsal root ganglion  Damage to this area causes sensation from the body area served to be lost Figure 7.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.76  Spinal Cord Anatomy  Exterior white mater – conduction tracts  Posterior, lateral, and anterior columns  Each contains a number of fiber tracts make up of axons with the same destination and function Figure 7.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.77  Spinal Cord Anatomy  Central canal filled with cerebrospinal fluid Figure 7.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.78  Peripheral Nervous System  Nerves and ganglia outside the central nervous system  Nerve = bundle of neuron fibers  Neuron fibers are bundled by a connective tissue sheath Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.79  Structure of a Nerve  Endoneurium surrounds each fiber  Groups of fibers are bound into fascicles by perineurium  Fascicles are bound together by epineurium Figure 7.20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.80  Classification of Nerves  Classified according to the direction in which they transmit impulses  Mixed nerves – carry both sensory and motor fibers – spinal nerves  Afferent (sensory) nerves – carry impulses toward the CNS  Efferent (motor) nerves – carry impulses away from the CNS Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.81  Cranial Nerves  12 pairs of nerves that mostly serve the head and neck  Numbered in order, front to back – names reveal structures they control  Most are mixed nerves, but three are sensory only  Optic, olfactory, and vestibulocochlear Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.82  Distribution of Cranial Nerves Figure 7.21 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.83  Cranial Nerves  I Olfactory nerve – sensory for smell  II Optic nerve – sensory for vision  III Oculomotor nerve – motor fibers to eye muscles  IV Trochlear – motor fiber to eye muscles Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.84  Cranial Nerves  V Trigeminal nerve – sensory for the face; motor fibers to chewing muscles  VI Abducens nerve – motor fibers to eye muscles  VII Facial nerve – sensory for taste; motor fibers to the face  VIII Vestibulocochlear nerve – sensory for balance and hearing Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.85  Cranial Nerves  IX Glossopharyngeal nerve – sensory for taste; motor fibers to the pharynx  X Vagus nerves – sensory and motor fibers for pharynx, larynx, and viscera  XI Accessory nerve – motor fibers to neck and upper back  XII Hypoglossal nerve – motor fibers to tongue Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.86  Spinal Nerves  There is a pair of spinal nerves at the level of each vertebrae for a total of 31 pairs  Spinal nerves are formed by the combination of the ventral and dorsal roots of the spinal cord  Spinal nerves are named for the region from which they arise Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.87  Spinal Nerves Figure 7.22a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.88  Anatomy of Spinal Nerves  Spinal nerves divide soon after leaving the spinal cord  Dorsal rami – serve the skin and muscles of the posterior trunk  Ventral rami – forms a complex of networks (plexus) for the anterior, which serve the motor and sensory needs of the limbs Figure 7.22b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.89  Examples of Nerve Distribution Figure 7.23 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.90  Autonomic Nervous System  The involuntary branch of the nervous system  Consists of only motor nerves  Divided into two divisions  Sympathetic division – mobilizes the body  Parasympathetic division – allows body to unwind Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.91  Differences Between Somatic and Autonomic Nervous Systems  Nerves  Somatic – one motor neuron – axons extend all the way to the skeletal muscle they serve  Autonomic – preganglionic and postganglionic nerves  Effector organs  Somatic – skeletal muscle  Autonomic – smooth muscle, cardiac muscle, and glands Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.92  Differences Between Somatic and Autonomic Nervous Systems  Nerurotransmitters  Somatic – always use acetylcholine  Autominic – use acetylcholine, epinephrine, or norepinephrine Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.93  Comparison of Somatic and Autonomic Nervous Systems Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.24 Slide 7.94  Anatomy of the Parasympathetic Division  Originates from the brain stem and S2 – S4  Neurons in the cranial region send axons out in cranial nerves to the head and neck organs  They synapse with the second motor neuron in a terminal ganglion  Terminal ganglia are at the effector organs  Always uses acetylcholine as a neurotransmitter Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.95  Anatomy of the Sympathetic Division – thoracolumbar division  Originates from T1 through L2  Preganglionic axons leave the cord in the ventral root, enter the spinal nerve, then pass through a ramus communications, to enter a sympathetic chain ganglion at the sympathetic chain (trunk) (near the spinal cord)  Short pre-ganglionic neuron and long postganglionic neuron transmit impulse from CNS to the effector  Norepinephrine and epinephrine are neurotransmitters to the effector organs Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.96  Sympathetic Pathways Figure 7.26 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.97  Anatomy of the Autonomic Nervous System Figure 7.25 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.98  Autonomic Functioning  Sympathetic – “fight-or-flight”  Response to unusual stimulus  Takes over to increase activities  Remember as the “E” division = exercise, excitement, emergency, and embarrassment Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.99  Autonomic Functioning  Parasympathetic – housekeeping activites  Conserves energy  Maintains daily necessary body functions  Remember as the “D” division - digestion, defecation, and diuresis Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.100  Development Aspects of the Nervous System  The nervous system is formed during the first month of embryonic development  Any maternal infection can have extremely harmful effects  The hypothalamus is one of the last areas of the brain to develop – contains centers for regulating body temperature Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.101  Development Aspects of the Nervous System  No more neurons are formed after birth, but growth and maturation continues for several years largely due to myelination  The brain reaches maximum weight as a young adult Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.102