Essentials of Human Anatomy & Physiology PDF

Essentials of Human Anatomy & Physiology Seventh Edition Elaine N. Marieb Chapter 7 The Nervous System Adapted by: Charles Jason Dango Copyright © 20...

Essentials of Human Anatomy & Physiology Seventh Edition Elaine N. Marieb Chapter 7 The Nervous System Adapted by: Charles Jason Dango Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Objectives To determine the functions of the nervous system To compare the cells in the Nervous System To differentiate the parts of the Nervous System  Functions of the Nervous System 1. Sensory input – gathering information To monitor changes occurring inside and outside the body (changes = stimuli) 2. Integration – to process and interpret sensory input and decide if action is needed. 3. Motor output A response to integrated stimuli The response activates muscles or glands Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.1a  Structural Classification of the Nervous System Central nervous system (CNS) Brain Spinal cord Peripheral nervous system (PNS) Nerve outside the brain and spinal cord Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.2  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 7.3a  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 7.3b  Functional Classification of the Peripheral Nervous System Motor (efferent) division Two subdivisions Somatic nervous system = voluntary Autonomic nervous system = involuntary Figure 7.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.3c  Organization of the Nervous System Figure 7.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.4  Nervous Tissue: Support Cells (Neuroglia or Glia) Astrocytes Abundant, star-shaped cells Brace neurons Form barrier between capillaries and neurons Control the chemical environment of the brain (CNS) Figure 7.3a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.5  Nervous Tissue: Support Cells Microglia (CNS) Spider-like phagocytes Dispose of debris Ependymal cells (CNS) Line cavities of the brain and spinal cord Circulate cerebrospinal fluid Figure 7.3b, c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.6  Nervous Tissue: Support Cells Oligodendrocytes (CNS) Produce myelin sheath around nerve fibers in the central nervous system Figure 7.3d Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.7a  Neuroglia vs. Neurons Neuroglia divide. Neurons do not. Most brain tumors are “gliomas.” Most brain tumors involve the neuroglia cells, not the neurons. Consider the role of cell division in cancer!  Support Cells of the PNS Satellite cells Protect neuron cell bodies Schwann cells Form myelin sheath in the peripheral nervous system Figure 7.3e Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.7b  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 (dendrites and axons) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.8  Neuron Anatomy Cell body Nucleus Large nucleolus Figure 7.4a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.9b  Neuron Anatomy Extensions outside the cell body Dendrites – conduct impulses toward the cell body Axons – conduct impulses away from the cell body (only 1!) Figure 7.4a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.10  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 7.11  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 7.12  Application In Multiple Scleroses the myelin sheath is destroyed. The myelin sheath hardens to a tissue called the scleroses. This is considered an autoimmune disease. Why does MS appear to affect the muscles?  Neuron Cell Body Location Most are found in the central nervous system Gray matter – cell bodies and unmylenated fibers Nuclei – clusters of cell bodies within the white matter of the central nervous system Ganglia – collections of cell bodies outside the central nervous system Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.13  Functional Classification of Neurons Sensory (afferent) neurons Carry impulses from the sensory receptors Cutaneous sense organs Proprioceptors – detect stretch or tension Motor (efferent) neurons Carry impulses from the central nervous system Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Functional Classification of Neurons Interneurons (association neurons) Found in neural pathways in the central nervous system Connect sensory and motor neurons Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Neuron Classification Figure 7.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.15  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  Structural Classification of Neurons Bipolar neurons – one axon and one dendrite Figure 7.8b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Structural Classification of Neurons Unipolar neurons – have a short single process leaving the cell body Figure 7.8c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  How Neurons Function (Physiology) Irritability – ability to respond to stimuli Conductivity – ability to transmit an impulse The plasma membrane at rest is polarized Fewer positive ions are inside the cell than outside the cell Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.17  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 in the neuron Figure 7.9a–c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.18  The Action Potential If the action potential (nerve impulse) starts, it is propagated over the entire axon 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 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.19  Nerve Impulse Propagation The impulse continues to move toward the cell body Impulses travel faster when fibers have a myelin sheath Figure 7.9c–e Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.20  Continuation of the Nerve Impulse between Neurons Impulses are able 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 dendrite Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.21  How Neurons Communicate at Synapses Figure 7.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.22  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 7.23  Regions of the Brain Cerebral hemispheres Diencephalon Brain stem Cerebellum Figure 7.12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.27  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  Cerebral Hemispheres (Cerebrum) The surface is made of ridges (gyri) and grooves (sulci) Figure 7.13a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Lobes of the Cerebrum Fissures (deep grooves) divide the cerebrum into lobes Surface lobes of the cerebrum Frontal lobe Parietal lobe Occipital lobe Temporal lobe Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Lobes of the Cerebrum Figure 7.15a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Specialized Areas of the Cerebrum Somatic sensory area – receives impulses from the body’s sensory receptors Primary motor area – sends impulses to skeletal muscles Broca’s area – involved in our ability to speak Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.30  Sensory and Motor Areas of the Cerebral Cortex Figure 7.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.31  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  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  Specialized Area of the Cerebrum Figure 7.13c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Layers of the Cerebrum Gray matter Outer layer Composed mostly of neuron cell bodies Figure 7.13a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  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  Layers of the Cerebrum Basal nuclei – internal islands of gray matter Regulates voluntary motor activities by modifying info sent to the motor cortex Problems = ie unable to control muscles, spastic, jerky Involved in Huntington’s and Parkinson’s Disease Figure 7.13a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Diencephalon Sits on top of the brain stem Enclosed by the cerebral heispheres Made of three parts Thalamus Hypothalamus Epithalamus Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Diencephalon Figure 7.15 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Thalamus Surrounds the third ventricle The relay station for sensory impulses Transfers impulses to the correct part of the cortex for localization and interpretation Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.35  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  Hypothalamus An important part of the limbic system (emotions) The pituitary gland is attached to the hypothalamus Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  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 7.37  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  Brain Stem Figure 7.15a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Midbrain Mostly composed of tracts of nerve fibers Reflex centers for vision and hearing Cerebral aquaduct – 3rd-4th ventricles Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.39  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 7.40  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 7.41  Cerebellum Two hemispheres with convoluted surfaces Provides involuntary coordination of body movements Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Cerebellum Figure 7.15a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Protection of the Central Nervous System Scalp and skin Skull and vertebral column Meninges Figure 7.16a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Protection of the Central Nervous System Cerebrospinal fluid Blood brain barrier Figure 7.16a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Meninges Dura mater Double-layered external covering Periosteum – attached to surface of the skull Meningeal layer – outer covering of the brain Folds inward in several areas Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Meninges Arachnoid layer Middle layer Web-like Pia mater Internal layer Clings to the surface of the brain Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Cerebrospinal Fluid Similar to blood plasma composition 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 7.46  Ventricles and Location of the Cerebrospinal Fluid Figure 7.17a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Ventricles and Location of the Cerebrospinal Fluid Figure 7.17b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Blood Brain Barrier Includes the least permeable capillaries of the body 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 7.48  Cerebrovascular Accident (CVA) Commonly called a stroke The result of 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 7.50  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 7.52  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 7.51  Spinal Cord Anatomy Exterior white mater – conduction tracts Figure 7.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Spinal Cord Anatomy Internal gray matter - mostly cell bodies Dorsal (posterior) horns Anterior (ventral) horns Figure 7.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Spinal Cord Anatomy Central canal filled with cerebrospinal fluid Figure 7.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  Spinal Cord Anatomy Meninges cover the spinal cord Nerves leave at the level of each vertebrae Dorsal root Associated with the dorsal root ganglia – collections of cell bodies outside the central nervous system Ventral root Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.54  Peripheral Nervous System Nerves and ganglia outside the central nervous system Nerve = bundle of neuron fibers Neuron fibers are bundled by connective tissue Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.55  Classification of Nerves Mixed nerves – both sensory and motor fibers 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 7.57  Spinal Nerves There is a pair of spinal nerves at the level of each vertebrae for a total of 31 pairs Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.63  Spinal Nerves Figure 7.22a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.64  Autonomic Nervous System The involuntary branch of the nervous system Consists of only motor nerves Divided into two divisions Sympathetic division Parasympathetic division Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.67  Anatomy of the Autonomic Nervous System Figure 7.25 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.73  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  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