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Nervous System
Nervous Tissue A&P 232 Overview of Nervous System NERVOUS SYSTEM Nervous System Central Nervous System Brain Peripheral Nervous System Spinal Cord Structural Classification Cranial Nerves Sensory Neurons Motor Neurons Functional Classification Spinal Nerves Sensory Neurons Somatic Nervous System Motor Neurons Sensory Neurons general senses Motor Neurons skeletal muscle Autonomic Nervous System Sensory Neurons visceral Motor Neurons smooth muscle cardiac muscle glands Sympathetic Division Parasympathetic Division Overview of Nervous System Nervous Tissue Anatomy Neurons Neuroglia Nerve Tissue Neurons Nerve Cells transmit electochemical signals (nerve impulses) Neuroglia insulate, nourish, support, protect 1 Nervous Tissue A&P 232 Neurons Structure of Neurons Cell body (soma) Nerve Tissue Neurons Nerve Cells transmit electochemical signals (nerve impulses) Neuroglia insulate, nourish, support, protect single nucleus Organelles Cell processes = dendrites & axons Nucleus Axons or Dendrites Cell body Structure of Neurons Dendrites “Receivers” Conducts impulses towards the cell body Typically short, highly branched Surfaces specialized for contact with other neurons Structure of Neurons Axons “Transmitters” Nerve Fiber Conduct impulses away from cell body toward synapse One axon per neuron Axon terminal Swollen tips at end of axon terminals called synaptic knobs (end bulbs) contain vesicles filled with neurotransmitters 2 Nervous Tissue A&P 232 Structure of Neurons The Synapse Specialized junction between two neurons Presynaptic cell Post synaptic cell Neurotransmitter Neuron Classification Function Sensory (afferent) Interneurons (association) Motor (efferent) Chemicals released by synaptic vesicles in presynaptic cell Affect activity of postsynaptic cell Synaptic cleft Receptors for neurotransmitter on postsynaptic cell Neuroglial Cells Neuroglial Classification Nerve Tissue Nerve Tissue Neurons Nerve Cells transmit electochemical signals (nerve impulses) Neurons Nerve Cells transmit electochemical signals (nerve impulses) Neuroglia insulate, nourish, support, protect Neuroglia insulate, nourish, support, protect CNS Astrocytes neurotransmitter metabolism Oligodendrites form myelin PNS Microglia phagocytic Ependymal Cells CSF Neurolemmocytes (Schwann Cells) form myelin sheath support, protect, nourish Satellite Cells support neuron cell bodies in PNS 3 Nervous Tissue A&P 232 Neuroglial Classification CNS: Astrocytes Nerve Tissue Neurons Nerve Cells transmit electochemical signals (nerve impulses) Neuroglia insulate, nourish, support, protect CNS Astrocytes neurotransmitter metabolism Oligodendrites form myelin PNS Microglia phagocytic Ependymal Cells CSF Neurolemmocytes (Schwann Cells) form myelin sheath support, protect, nourish Satellite Cells support neuron cell bodies in PNS CNS: Oligodendrocytes Node of Ranvier Internode Form myelin Myelin sheath Nodes of Ranvier White matter 3D framework for CNS Guide neuron development Control interstitial environment Covers blood vessels Regulate exchange of materials between blood and neurons CNS: Microglia Migrate Phagocytes Clear away dead cells, debris, pathogens, waste products, etc Analogous to Schwann cells of PNS 4 Nervous Tissue CNS: Ependymal cells A&P 232 Neuroglial Classification Epithelial membrane lining brain and spinal cord Formation and circulation of cerebrospinal fluid (CSF) Nerve Tissue Neurons Nerve Cells transmit electochemical signals (nerve impulses) Neuroglia insulate, nourish, support, protect CNS Astrocytes neurotransmitter metabolism PNS: Satellite Cells Support neurons in the PNS Analogous to astrocytes Oligodendrites form myelin PNS Microglia phagocytic Ependymal Cells CSF Neurolemmocytes (Schwann Cells) form myelin sheath support, protect, nourish Satellite Cells support neuron cell bodies in PNS PNS: Schwann Cell / Neurolemmocyte Form myelin sheath Cells encircling PNS axons Analagous to oligodendrocytes in CNS 5 Nervous Tissue A&P 232 Myelin Around axon of most neurons Functions Increases speed of conduction of a nerve impulse down the axon Electrically isolates adjacent neurons May direct axon regeneration following damage In both in PNS and CNS White matter = myelinated processes Gray matter = nerve cell bodies, dendrites, axon terminals, bundles of unmyelinated axons and neuroglia Nervous Tissue Physiology Transmembrane Potential Ion Channels Nerve Impulse 6 Nervous Tissue A&P 232 Transmembrane Potential Resting Membrane Potential Polarized -70 mV -70 mV phosphate Transmembrane Potential Chemical gradients Concentrations of potassium and sodium Electrical gradients Inside cell slightly negative relative to outside cell Electrochemical gradients: the sum of the chemical and electrical forces acting on a specific ion across the cell membrane 7 Nervous Tissue A&P 232 Nerve Impulse Action Potential Series of events that trigger opening and closing of ion channels This causes a change in the transmembrane potential = depolarization Depolarization of the axon causes the axon to release neurotransmitter from synaptic vesicles into synaptic cleft Local Anesthetics Prevent opening of voltage-gated Na+ channels Nerve impulses cannot pass the anesthetized region Novocaine and lidocaine Synapses Neurotransmitter in synaptic vesicles Receptors for neurotransmitter on postsynaptic cell Try to identify numbered structures 8 Nervous Tissue A&P 232 Neurotransmitters May excite or inhibit Acetylcholine causes contraction of skeletal muscles Endorphins inhibit pain signals Central Nervous System Removal of Neurotransmitters from cleft Brain Diffusion • move down concentration gradient Enzymes break them down Uptake by neurons or neuroglia • Prozac = serotonin reuptake inhibitor Overview of Nervous System Functions of Brain NERVOUS SYSTEM Central Nervous System Brain Integration center Registers sensations Correlates sensations with one another and with stored information Makes decisions Initiates taking action Peripheral Nervous System Spinal Cord Structural Classification Cranial Nerves Sensory Neurons Motor Neurons Functional Classification Spinal Nerves Sensory Neurons Motor Neurons Somatic Nervous System Sensory Neurons general senses Motor Neurons skeletal muscle Autonomic Nervous System Sensory Neurons visceral Motor Neurons smooth muscle cardiac muscle glands Sympathetic Division Parasympathetic Division Center for intellect, emotions, behavior, memory Directs behavior towards others 9 Nervous Tissue A&P 232 The Cerebrum Conscious sensations Voluntary actions Reasoning Planning Problem solving Personality Cerebrum Diencephalon Functional Areas of Cerebral Cortex Sensory Areas Thalamus Hypothalamus Vision Hearing Cutaneous sensation Smell Motor Areas Primary motor area Broca’s area Broca’s Wernicke’s Association Areas Premotor association area Frontal eye field 10 Nervous Tissue A&P 232 Diencephalon Diencephalon Thalamus Hypothalamus Integrates sensation Suppresses “unimportant conscious sensation Part of limbic system: involves emotional response Physical responses associated with rage, pleasure, pain, sexual arousal Controls autonomic function Coordination of nervous and endocrine systems Mineral and water balance Production of emotions and behavioral drives Coordination of between voluntary and autonomic functions Regulation of body temperature Controls sleep and wakefulness Brain Stem Brain Stem Midbrain Pons Medulla oblongata Midbrain Reflex centers for movement in response to visual stimuli Moves eyes, head and body in response to sight Reflex centers for movement in response to auditory stimuli Moves eyes, head and body in response to hearing 11 Nervous Tissue A&P 232 Brain Stem Pons Respiratory centers Rate and depth of breathing The Cerebellum Adjusts postural muscles of body Coordinating and fine-tuning skeletal muscle movements Brain Stem Medulla Oblongata Vital signs Respiratory control center Cardiac control center Vasomotor control center Multiple Structure Systems Limbic System Emotional brain Facilitates memory storage and retrieval Reticular Formation Physical behaviors • Sleep, alertness, fatigue, motivation Involved with • Introversion versus extroversion • Chronic fatigue syndrome • ADHD (attention deficit hyperactive disorder) 12 Nervous Tissue A&P 232 Cerebrospinal Fluid Cushions neural structures Supports the brain Transports Nutrients Chemical messengers Waste products Hydrocephalus Overview of Nervous System NERVOUS SYSTEM Central Nervous System Central Nervous System Brain Peripheral Nervous System Spinal Cord Structural Classification Cranial Nerves Functional Classification Spinal Nerves Spinal Cord Sensory Neurons Motor Neurons Sensory Neurons Motor Neurons Somatic Nervous System Sensory Neurons general senses Motor Neurons skeletal muscle Autonomic Nervous System Sensory Neurons visceral Motor Neurons smooth muscle cardiac muscle glands Sympathetic Division Parasympathetic Division 13 Nervous Tissue A&P 232 Functions of Spinal Cord Transmits impulses to and from the brain Ascending sensory tracts carry information to the brain Descending motor tracts carry information from the brain Peripheral Nervous System Processes spinal reflexes Definitions Cranial Nerves Spinal Nerves Overview of Nervous System Neuron: nerve cells that transmit electrochemical signals (nerve impulses) NERVOUS SYSTEM Central Nervous System Nerve: a bundle of neuron fibers or axons Sensory (afferent) Motor (efferent) Mixed Nerve fiber: a long process of a neuron Pathway: the route followed by a nerve impulse Brain Peripheral Nervous System Spinal Cord Structural Classification Cranial Nerves Sensory Neurons Motor Neurons Functional Classification Spinal Nerves Sensory Neurons Motor Neurons Somatic Nervous System Sensory Neurons general senses Motor Neurons skeletal muscle Autonomic Nervous System Sensory Neurons visceral Motor Neurons smooth muscle cardiac muscle glands Sympathetic Division Parasympathetic Division 14 Nervous Tissue Cranial Nerves A&P 232 Spinal Nerves Shingles -- varicella zoster virus • Infects neuron cell body • Travels down sensory nerve fiber Peripheral Nervous System Somatic Nervous System 15 Nervous Tissue A&P 232 Overview of Nervous System Somatic Nervous System sensory neurons carry sensory information you are aware of NERVOUS SYSTEM Central Nervous System Brain Peripheral Nervous System Spinal Cord Structural Classification Cranial Nerves Sensory Neurons Motor Neurons Pain Touch Temperature Functional Classification Spinal Nerves Sensory Neurons Motor Neurons Somatic Nervous System Sensory Neurons general senses Motor Neurons skeletal muscle motor neurons innervate skeletal muscle Autonomic Nervous System Sensory Neurons visceral Voluntary control Motor Neurons smooth muscle cardiac muscle glands Sympathetic Division Parasympathetic Division Overview of Nervous System NERVOUS SYSTEM Peripheral Nervous System Central Nervous System Brain Peripheral Nervous System Spinal Cord Structural Classification Cranial Nerves Functional Classification Spinal Nerves Autonomic Nervous System Sensory Neurons Motor Neurons Sensory Neurons Motor Neurons Somatic Nervous System Sensory Neurons general senses Motor Neurons skeletal muscle Autonomic Nervous System Sensory Neurons visceral Motor Neurons smooth muscle cardiac muscle glands Sympathetic Division Parasympathetic Division 16 Nervous Tissue A&P 232 Autonomic Nervous System Includes All sensory neurons that transmit impulses from internal organs to the CNS All motor neurons that transmit impulses from the CNS to • Smooth muscle • Cardiac muscles • Glands Divisions of the ANS 2 major divisions Parasympathetic Sympathetic Dual innervation One speeds up organ One slows down organ Ex: Heart Autonomic Motor Neurons Principle divisions Sympathetic Parasympathetic Dual innervation: most internal organs are innervated by both sympathetic and parasympathetic fibers Hypothalamus regulates balance (tone) between sympathetic and parasympathetic activity levels Sympathetic Responses Physical or emotional stress Alarm reaction: flight or fight response Dilation of pupils Increase of heart rate, force of contraction & BP Decrease in blood flow to nonessential organs Increase in blood flow to skeletal & cardiac muscle Airways dilate & respiratory rate increases Blood glucose level increase Increased sweat gland activity 17 Nervous Tissue A&P 232 Parasympathetic Responses Enhance “rest-and-digest” activities Mechanisms that help conserve and restore body energy during times of rest Normally dominate over sympathetic impulses SLUDD type responses and 3 “decreases” Reflexes Salivation, lacrimation, urination, digestion, defecation Heart rate, diameter airways, diameter pupils Reflex Protective, rapid, predictable, involuntary motor response to an environmental stimulus Requires stimulation Quick Involuntary Predictable Classifications Types of nerves that mediate them Spinal reflex Cranial reflex Effector Somatic reflex Autonomic (visceral) reflex Example Withdrawal reflex 18 Nervous Tissue A&P 232 Integrating Center (gray matter of CNS) REFLEX ARC Motor Neuron Sensory neuron Effector Organ Sensory receptor 19
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