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PowerPoint® Lecture Slide Presentation by Patty Bostwick-Taylor, Florence-Darlington Technical College The Nervous System 7 PART A Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous System Medical Terms Ax – axle Peri – around Dendr – tree Plex – interweaving Gangli – swelling Sens – feeling Mening – membrane Soma - body Moto – moving Syn - together Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Nervous System allows the body to: Think Feel Remember Move Be aware of the world Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous tissue is composed of neurons. Neurons transmit information in the form of electrochemical changes called nerve impulses from cell to cell. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of a Neuron Neurons = nerve cells Cell body Processes—fibers that extend from the cell body Dendrites—receive messages Axons—send messages Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Neurons Figure 7.4 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nerves are bundles of axons Neuroglial cells support nerves like connective tissues Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous System Organs are in two groups Central nervous system (CNS) Brain Spinal cord Peripheral nervous system (PNS) Nerves outside the brain and spinal cord Cranial nerves Spinal nerves Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Three major functions of the Nervous System Sensory Function - using receptors at the ends of peripheral neurons Detect changes inside and outside the body Convert environmental information into nerve impulses Send information to CNS – signals are “integrated” Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Three major functions of the Nervous System Integrated Function – allows us to make conscious and unconscious decisions, use motor function to act on them Signals are brought together Create sensations Added to memory Produce perceptions Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Three major functions of the Nervous System Motor Function – uses peripheral neurons to carry impulses to effectors Effectors are muscles or glands Muscles contract Glands secrete Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Functions of the Nervous System Figure 7.1 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Motor Functions are divided into two categories. Somatic nervous system = voluntary Consciously controlled Skeletal Muscles Autonomic nervous system = involuntary Unconsciously controlled Heart, smooth muscle contractions and glands Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings More about nerves Mature neurons do not divide. Some nervous stem cells do. Myelin – protein covering around axons “Myelin Sheath” Gray Matter = myelinated axons White Matter = Unmyelinated axons Peripheral nerves regenerate axons when damaged CNS neurons do not regenerate. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Relative Size of a Neuron If the cell body was the size of a tennis ball, The dendrites would fill a large bedroom, And the axon would be 1 mile long and ½ inch thick!!! Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Impulses – “threshold potential” Na+ and K+ ions flow into and out of the cell as the Na+/K+ pump tries to maintain normal concentrations The flow of ions transmits the signals down the axons All-or-None response – if there is a response, it is complete Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Impulses Figure 7.9a–b Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Impulses Figure 7.9c–d Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Impulses Figure 7.9e–f Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Synapse Nerve impulses travel along nerve pathways Neurons do not touch Synapse—junction between nerves Synaptic cleft—gap between adjacent neurons Synaptic transmission – the process of crossing a synapse Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of a Signal at Synapses Axon of transmitting neuron Axon terminal Action potential arrives Vesicles Synaptic cleft Receiving neuron Synapse Figure 7.10, step 1 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Sensory Dendrite Cell Body Axon Synapse Dendrite Receptor Figure 7.6 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of a Signal at Synapses When the impulse reaches the synapse, vesicles in the “knob” release a neurotransmitter, which binds to specific receptors on the next neuron. Neurotransmitters Excitatory Inhibitory Thousands of presynaptic neurons may communicate with one postsynaptic neuron Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Neurotransmitters 50+ have been identified Acetylcholine – Ach – Skeletal muscles “excitatory” Epinephrine, dopamine, serotonin – inhibitory Neurotransmitters bind and allow Ca+2 to flow sending the message Caffeine lowers thresholds – neurons more easily excited Antidepressants – keep serotonin in synapses longer Prozac, Paxil, Zoloft Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Fibers – aka “axons” Nerve – bundle of fibers Sensory fibers – brain and spinal cord Motor fibers – muscles or glands Mixed nerves – carry both Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Anatomy Fibers are bundled into bundles surrounded by endoneurium Bundles are covered in perineurium and form fascicles Fascicles are surrounded by epineurium Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of a Nerve Figure 7.23 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Reflexes Reflex—rapid, predictable, and involuntary response to a stimulus Knee-jerk, heart rate, digestion Reflex arc—direct route from a sensory neuron, to an interneuron, to an effector Swallowing, sneezing, coughing, vomiting Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Simple Reflex Arc Sensory receptors (stretch receptors in the quadriceps muscle) Sensory (afferent) neuron Spinal cord Sensory receptors (pain receptors in the skin) Sensory (afferent) neuron Synapse in ventral horn gray matter Interneuron Motor (efferent) neuron Motor (efferent) neuron (b) Effector (quadriceps muscle of thigh) Effector (biceps brachii muscle) (c) Figure 7.11b–c Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Protection of the Central Nervous System Scalp and skin Skull and vertebral column Meninges Cerebrospinal fluid (CSF) Blood-brain barrier Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Protection of the Central Nervous System Figure 7.17a Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Meninges Figure 7.17b Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Meninges Membranes between bones and nerves for protection Three layers Dura mater Arachnoid mater Pia mater Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Meninges Made of connective tissue Contain blood vessels and nerves Separated from the bones by an “epidural space” Loose connective and adipose tissues Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Spinal Cord Anatomy Figure 7.21 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Spinal Cord Slender nerve column from brain into vertebral canal ends at L1 31 pairs of spinal nerves arise from the spinal cord Thickens at the cervical and lumbar regions for service to the arms and legs Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Spinal Cord Anatomy Figure 7.20 (1 of 2) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Spinal Cord Anatomy Figure 7.20 (2 of 2) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cross Section of the Spinal Cord Gray Matter – Interneurons White matter—Cell bodies – axons extend out Central canal - filled with cerebrospinal fluid Spinal nerves – extend to effectors Vertebrae – bone covering Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Two functions of the Spinal Cord 1. To conduct nerve impulses 2. Serve as a center for spinal reflexes Axons can extend from the spinal cord to your toe. Stubbing your toe sends a sensory message in 1/100 second. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Pathways Between Brain and Spinal Cord Figure 7.22 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Brain 100 billion neurons Cerebrum – sensory and motor function, memory and reasoning Cerebellum – voluntary muscle movements Brain stem – organ activities, connection to body Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Regions of the Brain: Cerebrum Figure 7.12b Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cerebrum Paired Left and Right halves of the brain Bridge – Corpus Callosum Four lobes - Frontal, Parietal, Temporal, Occipital Covered by cerebral cortex – gray mater Contains 75% of all neurons White mater contains myelinated axons that connect the cortex to other brain regions or the body Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Regions of the Brain: Cerebrum Figure 7.13b Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Regions of the Brain: Cerebrum Figure 7.15 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Regions of the Brain: Cerebrum Figure 7.13c Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Regions of the Brain: Cerebrum Figure 7.14 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Regions of the Brain: Diencephalon Figure 7.16 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Functions of the Cerebrum Higher brain functioning Interprets sensory Impulses, initiates voluntary muscular movements Stores information for memory and uses it to reason Intelligence and personality 90% of people are left hemisphere dominant for writing, speech and reading Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Ventricles contain Cerebrospinal Fluid (CSF) Allows organs to float in fluid Absorbs forces Spinal tap – measures pressure in fluid; can detect infection, tumor or blood clot Brain blood barrier – tightly packed epithelials and neuroglia only allow certain molecules from blood to brain Keeps toxins out and prevents large biochemical fluctuations Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Ventricles and Location of the Cerebrospinal Fluid Figure 7.18a–b Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Hydrocephalus in a Newborn Hydrocephalus CSF accumulates and exerts pressure on the brain if not allowed to drain Figure 7.19 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Blood-Brain Barrier Useless as a barrier against some substances Fats and fat soluble molecules Respiratory gases Alcohol Nicotine Anesthesia Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Diencephalon – surrounds the midbrain Contains Thalmus – channels sensory impulses to the brain Hypothalmus – homeostasis, regulates organs with hormones Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Brain Stem – attaches to the spinal cord Midbrain – links movement to eyesight or sound Pons - breathing Medulla oblongata – heart, vasomotor, respiratory Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Regions of the Brain: Brain Stem Figure 7.16a Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cerebellum Provides involuntary coordination of body movements Posture Reports on positions of the limbs Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Regions of the Brain: Cerebellum Figure 7.16a Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings PNS: Cranial Nerves I Olfactory nerve—smell II Optic nerve—vision III Oculomotor nerve—extrinsic eye muscles IV Trochlear—oblique eye muscles Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings PNS: Cranial Nerves V Trigeminal nerve—sensory for the face; motor fibers to chewing muscles VI Abducens nerve—lateral rectus eye muscles VII Facial nerve—sensory for taste; motor fibers to the face VIII Vestibulocochlear nerve—sensory for balance and hearing Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings PNS: 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 © 2009 Pearson Education, Inc., publishing as Benjamin Cummings PNS: Distribution of Cranial Nerves Figure 7.24 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings PNS: The Cranial Nerves Table 7.1 (1 of 4) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings PNS: The Cranial Nerves Table 7.1 (2 of 4) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings PNS: The Cranial Nerves Table 7.1 (3 of 4) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings PNS: The Cranial Nerves Table 7.1 (4 of 4) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings PNS: Spinal Nerves Figure 7.25a Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings PNS: Distribution of Major Peripheral Nerves of the Upper and Lower Limbs Figure 7.26a Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings PNS: Distribution of Major Peripheral Nerves of the Upper and Lower Limbs Figure 7.26b Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings PNS: Distribution of Major Peripheral Nerves of the Upper and Lower Limbs Figure 7.26c Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings