Nervous System PDF

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. Mot...

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?  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  How Neurons Communicate at Synapses Figure 7.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.22  Ganglion Nucleus A group of neurons A group of neurons outside the CNS within the CNS Nerve Tract A group of nerve A group of nerve fibers fibers (axons) (axons) within the CNS outside the CNS  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  Simple Reflex Arc Figure 7.11b, c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.24  Types of Reflexes and Regulation · Autonomic reflexes · Smooth muscle regulation · Heart and blood pressure regulation · Regulation of glands · Digestive system regulation · Somatic reflexes · Activation of skeletal muscles Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.25  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  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 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 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  Meninges Surrounding both the spinal cord and the brain are the meninges, a three layered covering of connective tissue. The dura mater is the tough outer layer. Beneath the dura is the arachnoid which is like a spider web in consistency. The arachnoid has abundant space within and beneath it (the subarachnoid space) which contains cerebrospinal fluid, as does the space beneath the dura mater (subdural space). This cerebrospinal fluid supplies buoyancy for the spinal cord and brain to help provide shock absorption. The pia mater is a very thin layer which adheres tightly to the surface of the brain and spinal cord. It follows all contours and fissures (sulci) of the brain and cord. 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 Cranial Nerves Spinal nerves join together in plexuses. A plexus is an interconnection of fibers which form new combinations as the "named" or peripheral nerves. There are four voluntary plexuses (there are also some autonomic plexuses): 1. The cervical plexus 2. The brachial plexus 3. The lumbar plexus 4. The sacral plexus. Each plexus gives rise to new combinations of fibers as the peripheral nerves.  Spinal Nerves At 31 places along the spinal cord the dorsal and ventral roots come together to form spinal nerves. Spinal nerves contain both sensory and motor fibers, as do most nerves. Spinal nerves are given numbers which indicate the portion of the vertebral column in which they arise. There are 8 cervical (C1-C8), 12 thoracic (T1-T12), 5 lumbar (L1-L5), 5 sacral (S1-S5), and 1 coccygeal nerve. Nerve C1 arises between the cranium and atlas (1st cervical vertebra) and C8 arises between the 7th cervical and 1st thoracic vertebra. All the others arise below the respective vertebra or former vertebra in the case of the sacrum. Since the actual cord ends at the second lumbar vertebra, the later roots arise close together on the cord and travel downward to exit at the appropriate point. These nerve roots are called the cauda equina because of their resemblance to a horses tail. Anatomy of the Spinal Cord