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The Nervous System. The master controlling and communication system of The master controlling and communication system of the body.

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Presentation on theme: "The Nervous System. The master controlling and communication system of The master controlling and communication system of the body."— Presentation transcript:

1 The Nervous System

2 The master controlling and communication system of The master controlling and communication system of the body

3 Three Overlapping Functions Sensory Input Sensory Input Monitors internal and external stimuli (Changes) Monitors internal and external stimuli (Changes) Afferent pathway to the brain Afferent pathway to the brain receptors receptors Integration Integration Processes and interprets information Processes and interprets information Decides the appropriate response Decides the appropriate response Motor Output Motor Output Efferent pathway to effector organs (muscles or glands), effects a response Efferent pathway to effector organs (muscles or glands), effects a response

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5 Organization of the Nervous System Central Nervous System (CNS) Central Nervous System (CNS) Brain and spinal cord Brain and spinal cord Dorsal body cavity Dorsal body cavity Integrating command center Integrating command center Peripheral Nervous System (PNS) Peripheral Nervous System (PNS) Nerves to and from brain and spinal cord Nerves to and from brain and spinal cord Communication links to the CNS Communication links to the CNS Spinal nerves and cranial nerves Spinal nerves and cranial nerves

6 Peripheral Nervous System Sensory Afferent Division Sensory Afferent Division Impulses to the brain and spinal cord (CNS) Impulses to the brain and spinal cord (CNS) Monitors internal and external changes Monitors internal and external changes Somatic afferent Somatic afferent Skin, skeletal muscle, joints Skin, skeletal muscle, joints Visceral afferent Visceral afferent Organs within ventral body cavity Organs within ventral body cavity

7 Peripheral Nervous System Motor Efferent Division Motor Efferent Division From CNS to effector muscle, organs, and glands From CNS to effector muscle, organs, and glands Somatic efferent nervous system Somatic efferent nervous system Voluntary nervous system Voluntary nervous system Autonomic nervous system Autonomic nervous system Involuntary Involuntary Visceral motor nerve fibers (to smooth and cardiac muscle and glands) Visceral motor nerve fibers (to smooth and cardiac muscle and glands) Sympathetic (emergency situations) Sympathetic (emergency situations) Parasympathetic (conserves energy, nonemergency functions) Parasympathetic (conserves energy, nonemergency functions)

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9 Classification P. 224 P. 224

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11 Nervous System THE CELLS OF THE NERVOUS SYSTEM

12 Nervous Tissue-Types of Cells Two Principal Cell Types- Neurons: excitable nerve cells Neurons: excitable nerve cells Supporting cells : Neuroglia Nerve Glue Supporting cells : Neuroglia Nerve Glue Support, insulate, and protect neurons by surrounding and wrapping neurons. Support, insulate, and protect neurons by surrounding and wrapping neurons. Central nervous system supporting cells Central nervous system supporting cells Astrocytes Astrocytes Microglia Microglia Ependymal cells Ependymal cells Oligodendrocytes Oligodendrocytes Peripheral nervous system supporting cells Peripheral nervous system supporting cells Satellite cells Satellite cells Schwann cells Schwann cells

13 Neuroglia-Supporting Cells of CNS

14 Astrocytes Most abundant*Star-shaped Most abundant*Star-shaped Radiating processes cover neurons and anchor them to adjacent blood vessels Radiating processes cover neurons and anchor them to adjacent blood vessels Controls exchange between blood vessels and neurons Controls exchange between blood vessels and neurons Determines capillary permeability Determines capillary permeability

15 Astrocytes (Cont) Controls chemical environment around neurons Controls chemical environment around neurons Cleans up leaked potassium and recycling released neurotransmitter Cleans up leaked potassium and recycling released neurotransmitter Guide migration of young neurons Guide migration of young neurons

16 Microglia Small, ovoid cells, with thorny processes (spider-like) Small, ovoid cells, with thorny processes (spider-like) Branches monitor health of neurons Branches monitor health of neurons Migrate toward injured neuron Migrate toward injured neuron Transform into a macrophage when invading microorganisms or dead neurons are present and dispose of debris Transform into a macrophage when invading microorganisms or dead neurons are present and dispose of debris Protective role because cells of immune system are denied access to CNS Protective role because cells of immune system are denied access to CNS

17 Ependymal cells Simple squamous to columnar in shape Simple squamous to columnar in shape Line the cavities of the brain and spinal cord Line the cavities of the brain and spinal cord Beating of their cilia circulates cerebrospinal fluid that cushions brain and spinal cord Beating of their cilia circulates cerebrospinal fluid that cushions brain and spinal cord

18 Oligodendrocytes Wrap cytoplasmic extensions around neurons and form myelin sheaths in CNS Wrap cytoplasmic extensions around neurons and form myelin sheaths in CNS Insulates and protects Insulates and protects

19 Supporting Cells of the PNS Satellite cells Satellite cells Surround neuron cell bodies within ganglia Surround neuron cell bodies within ganglia Protective and cushioning cells Protective and cushioning cells Schwann cells Schwann cells Surround and form myelin sheaths around larger nerve fibers Surround and form myelin sheaths around larger nerve fibers Functionally similar to oligodendrocytes Functionally similar to oligodendrocytes

20 Neurons Highly specialized to transmit nerve impulses

21 Neurons Nerve cells Nerve cells Structural units of the nervous system Structural units of the nervous system Special characteristics of neurons: Special characteristics of neurons: 1. Conduct nerve impulses 2. Extreme longevity 3. Amiotic (exceptions: olfactory and hippocampus) (become injured and do not regenerate) 4. High metabolic rate: requires abundant oxygen and glucose All Neurons have cell bodies and processes, plus three functional components: receptive or input region, conducting component, and secretory or output component. All Neurons have cell bodies and processes, plus three functional components: receptive or input region, conducting component, and secretory or output component.

22 Cell Body Metabolic center Metabolic center No centrioles No centrioles Ribosomes and rough ER (Nissl Substance)most active of any cell in the body Ribosomes and rough ER (Nissl Substance)most active of any cell in the body Plasma membrane acts as part of the receptive surface Plasma membrane acts as part of the receptive surface Most located within the CNS (called nuclei) Most located within the CNS (called nuclei) Cell body collections in the PNS are called ganglia Cell body collections in the PNS are called ganglia

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24 Cell Processes Brain and spinal cord (CNS) contain both cell bodies and their processes Brain and spinal cord (CNS) contain both cell bodies and their processes The PNS consists chiefly of neuron processes The PNS consists chiefly of neuron processes Bundles of neuron processes are called tracts (CNS) and nerves (PNS). Bundles of neuron processes are called tracts (CNS) and nerves (PNS). Dendrites Dendrites Short, tapering, hundreds/cell Short, tapering, hundreds/cell Receptive (input) region; convey incoming messages(electrical signals) toward the cell body Receptive (input) region; convey incoming messages(electrical signals) toward the cell body Large surface area Large surface area

25 Cell Processes Axon (conducting component) One Axon (Single process) per neuron One Axon (Single process) per neuron Axon arises from axon hillock of cell body Axon arises from axon hillock of cell body Generates nerve impulses and transmits them away from the cell body Generates nerve impulses and transmits them away from the cell body Long axons called nerve fibers Long axons called nerve fibers Axon terminals –created where the axon branches at the terminal end terminal branches per axon terminal branches per axon Axon terminals are the secretory portionsecretes neurotransmitters Axon terminals are the secretory portionsecretes neurotransmitters

26 Myelin Sheath (neurilemma) Myelin: whitish, fatty material covering long nerve fibers; has waxy appearance Myelin: whitish, fatty material covering long nerve fibers; has waxy appearance Protects and provides an electrical insulation covering for large and long nerve fibers Protects and provides an electrical insulation covering for large and long nerve fibers Increases speed of transmission of nerve impulses Increases speed of transmission of nerve impulses Unmyelinated fibers conduct impulses slowly Unmyelinated fibers conduct impulses slowly Associated only with axons; Dendrites always unmyelinated Associated only with axons; Dendrites always unmyelinated Formed by Schwann cells in PNSmade of concentric layers of cell membranes (no channel or carrier proteins) called the neurilemma Formed by Schwann cells in PNSmade of concentric layers of cell membranes (no channel or carrier proteins) called the neurilemma

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28 Myelin (Cont) Nodes of Ranvier are the gaps between Schwann cells regularly spaced Nodes of Ranvier are the gaps between Schwann cells regularly spaced Oligodendrocytes form CNS myelin sheathscoils around 60 fibers at the same timeno neurilemma because of the absence of coiling of cells Oligodendrocytes form CNS myelin sheathscoils around 60 fibers at the same timeno neurilemma because of the absence of coiling of cells Regions of the brain and spinal cord with myelinated fibers called white matter. Regions of the brain and spinal cord with myelinated fibers called white matter. Gray matter contains mostly cell bodies and unmyelinated fibers Gray matter contains mostly cell bodies and unmyelinated fibers

29 Classification of Neurons Structural Classification Structural Classification Multipolar neurons Multipolar neurons Bipolar neurons Bipolar neurons Unipolar Neurons Unipolar Neurons Functional Classification Functional Classification Sensory (afferent) neurons Sensory (afferent) neurons Motor (efferent) neurons Motor (efferent) neurons Association (interneurons) neurons Association (interneurons) neurons

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33 Nervous Tissue Structures p. 227 p. 227 CELL BODY DENDRITE

34 Nervous Tissue Structures AXON AXON TERMINAL

35 Nervous Tissue Structures SCHWANN CELLS NODES OF RANVIER


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