Essentials of Human Anatomy & Physiology - Chapter 7: The Nervous System PDF
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2003
Elaine N. Marieb
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Summary
This document presents lecture slides on the human nervous system, including its functions, classifications, and anatomy. It is part of a larger textbook Essentials of Human Anatomy & Physiology, Seventh Edition.
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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