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The Nervous System. Functions of the Nervous System. Sensory input—gathering information To monitor changes occurring inside and outside the body Changes = stimuli Integration To process and interpret sensory input and decide if action is needed. Functions of the Nervous System.

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functions of the nervous system
Functions of the Nervous System
  • Sensory input—gathering information
    • To monitor changes occurring inside and outside the body
    • Changes = stimuli
  • Integration
    • To process and interpret sensory input and decide if action is needed
functions of the nervous system1
Functions of the Nervous System
  • Motor output
    • A response to integrated stimuli
    • The response activates muscles or glands
structural classification of the nervous system
Structural Classification of the Nervous System
  • Central nervous system (CNS)
    • Brain
    • Spinal cord
  • Peripheral nervous system (PNS)
    • Nerves outside the brain and spinal cord
      • Spinal nerves
      • Cranial nerves
functional classification of the peripheral nervous system
Functional Classification of the Peripheral Nervous System
  • Sensory (afferent) division
    • Nerve fibers that carry information to the central nervous system
  • Motor (efferent) division
    • Nerve fibers that carry impulses away from the central nervous system
functional classification of the peripheral nervous system1
Functional Classification ofthe Peripheral Nervous System
  • Motor (efferent) division (continued)
    • Two subdivisions
      • Somatic nervous system = voluntary
      • Autonomic nervous system = involuntary
nervous tissue support cells
Nervous Tissue: Support Cells
  • Support cells in the CNS are grouped together as “neuroglia”
  • Function: to support, insulate, and protect neurons
nervous tissue support cells1
Nervous Tissue: Support Cells
  • Astrocytes
    • Abundant, star-shaped cells
    • Brace neurons
    • Form barrier between capillaries and neurons
    • Control the chemical environment of the brain
nervous tissue support cells3
Nervous Tissue: Support Cells
  • Microglia
    • Spiderlike phagocytes
    • Dispose of debris
nervous tissue support cells5
Nervous Tissue: Support Cells
  • Ependymal cells
    • Line cavities of the brain and spinal cord
    • Circulate cerebrospinal fluid
nervous tissue support cells7
Nervous Tissue: Support Cells
  • Oligodendrocytes
    • Wrap around nerve fibers in the central nervous system
    • Produce myelin sheaths
nervous tissue support cells9
Nervous Tissue: Support Cells
  • Satellite cells
    • Protect neuron cell bodies
  • Schwann cells
    • Form myelin sheath in the peripheral nervous system
nervous tissue neurons
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
nervous tissue neurons1
Nervous Tissue: Neurons
  • Cell body
    • Nissl substance
      • Specialized rough endoplasmic reticulum
    • Neurofibrils
      • Intermediate cytoskeleton
      • Maintains cell shape
nervous tissue neurons3
Nervous Tissue: Neurons
  • Cell body
    • Nucleus
    • Large nucleolus
  • Processes outside the cell body
    • Dendrites—conduct impulses toward the cell body
    • Axons—conduct impulses away from the cell body
nervous tissue neurons5
Nervous Tissue: Neurons
  • 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
nervous tissue neurons6
Nervous Tissue: Neurons
  • Myelin sheath—whitish, fatty material covering axons
  • Schwann cells—produce myelin sheaths in jelly roll–like fashion
  • Nodes of Ranvier—gaps in myelin sheath along the axon
neuron cell body location
Neuron Cell Body Location
  • Most neuron cell bodies are found in the central nervous system
    • Gray matter—cell bodies and unmyelinated 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
functional classification of neurons
Functional Classification of Neurons
  • Sensory (afferent) neurons
    • Carry impulses from the sensory receptors to the CNS
      • Cutaneous sense organs
      • Proprioceptors—detect stretch or tension
  • Motor (efferent) neurons
    • Carry impulses from the central nervous system to viscera, muscles, or glands
functional classification of neurons2
Functional Classification of Neurons
  • Interneurons (association neurons)
    • Found in neural pathways in the central nervous system
    • Connect sensory and motor neurons
structural classification of neurons
Structural Classification of Neurons
  • Multipolar neurons—many extensions from the cell body

Figure 7.8a

structural classification of neurons1
Structural Classification of Neurons
  • Bipolar neurons—one axon and one dendrite

Figure 7.8b

structural classification of neurons2
Structural Classification of Neurons
  • Unipolar neurons—have a short single process leaving the cell body

Figure 7.8c

functional properties of neurons
Functional Properties of Neurons
  • Irritability
    • Ability to respond to stimuli
  • Conductivity
    • Ability to transmit an impulse
nerve impulses
Nerve Impulses
  • Resting neuron
    • The plasma membrane at rest is polarized
    • Fewer positive ions are inside the cell than outside the cell
  • Depolarization
    • A stimulus depolarizes the neuron’s membrane
    • A depolarized membrane allows sodium (Na+) to flow inside the membrane
  • The exchange of ions initiates an action potential in the neuron
nerve impulses1
Nerve Impulses

Figure 7.9a–b

nerve impulses2
Nerve Impulses
  • Action potential
    • If the action potential (nerve impulse) starts, it is propagated over the entire axon
    • Impulses travel faster when fibers have a myelin sheath
nerve impulses3
Nerve Impulses

Figure 7.9c–d

nerve impulses4
Nerve Impulses
  • Repolarization
    • Potassium ions rush out of the neuron after sodium ions rush in, which repolarizes the membrane
    • The sodium-potassium pump, using ATP, restores the original configuration
nerve impulses5
Nerve Impulses

Figure 7.9e–f

transmission of a signal at synapses
Transmission of a Signal at Synapses
  • 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
transmission of a signal at synapses1
Axonterminal

Actionpotentialarrives

Axon oftransmittingneuron

Vesicles

Synapticcleft

Receivingneuron

Synapse

Transmitting neuron

Neurotrans-mitter bindsto receptoron receivingneuron’smembrane

Vesiclefuses withplasmamembrane

Neurotrans-mitter is re-leased intosynaptic cleft

Neurotransmittermolecules

Synaptic cleft

Ion channels

Receiving neuron

Neurotransmitterbroken downand released

Neurotransmitter

Receptor

Na+

Na+

Ion channel opens

Ion channel closes

Transmission of a Signal at Synapses

Figure 7.10

transmission of a signal at synapses2
Axonterminal

Actionpotentialarrives

Axon oftransmittingneuron

Vesicles

Synapticcleft

Receivingneuron

Synapse

Transmission of a Signal at Synapses

Figure 7.10, step 1

transmission of a signal at synapses3
Axonterminal

Axon oftransmittingneuron

Actionpotentialarrives

Vesicles

Synapticcleft

Receivingneuron

Synapse

Transmitting neuron

Vesiclefuses withplasmamembrane

Synaptic cleft

Ion channels

Receiving neuron

Transmission of a Signal at Synapses

Figure 7.10, step 2

transmission of a signal at synapses4
Axonterminal

Axon oftransmittingneuron

Actionpotentialarrives

Vesicles

Synapticcleft

Receivingneuron

Synapse

Transmitting neuron

Vesiclefuses withplasmamembrane

Neurotrans-mitter is re-leased intosynaptic cleft

Neurotransmittermolecules

Synaptic cleft

Ion channels

Receiving neuron

Transmission of a Signal at Synapses

Figure 7.10, step 3

transmission of a signal at synapses5
Axonterminal

Axon oftransmittingneuron

Actionpotentialarrives

Vesicles

Synapticcleft

Receivingneuron

Synapse

Transmitting neuron

Neurotrans-mitter bindsto receptoron receivingneuron’smembrane

Vesiclefuses withplasmamembrane

Neurotrans-mitter is re-leased intosynaptic cleft

Neurotransmittermolecules

Synaptic cleft

Ion channels

Receiving neuron

Transmission of a Signal at Synapses

Figure 7.10, step 4

transmission of a signal at synapses6
Axonterminal

Axon oftransmittingneuron

Actionpotentialarrives

Vesicles

Synapticcleft

Receivingneuron

Synapse

Transmitting neuron

Neurotrans-mitter bindsto receptoron receivingneuron’smembrane

Vesiclefuses withplasmamembrane

Neurotrans-mitter is re-leased intosynaptic cleft

Neurotransmittermolecules

Synaptic cleft

Ion channels

Receiving neuron

Neurotransmitter

Receptor

Na+

Ion channel opens

Transmission of a Signal at Synapses

Figure 7.10, step 5

transmission of a signal at synapses7
Axonterminal

Axon oftransmittingneuron

Actionpotentialarrives

Vesicles

Synapticcleft

Receivingneuron

Synapse

Transmitting neuron

Neurotrans-mitter bindsto receptoron receivingneuron’smembrane

Vesiclefuses withplasmamembrane

Neurotrans-mitter is re-leased intosynaptic cleft

Neurotransmittermolecules

Synaptic cleft

Ion channels

Receiving neuron

Neurotransmitterbroken downand released

Neurotransmitter

Receptor

Na+

Na+

Ion channel opens

Ion channel closes

Transmission of a Signal at Synapses

Figure 7.10, step 6

transmission of a signal at synapses8
Axonterminal

Actionpotentialarrives

Axon oftransmittingneuron

Vesicles

Synapticcleft

Receivingneuron

Synapse

Transmitting neuron

Neurotrans-mitter bindsto receptoron receivingneuron’smembrane

Vesiclefuses withplasmamembrane

Neurotrans-mitter is re-leased intosynaptic cleft

Neurotransmittermolecules

Synaptic cleft

Ion channels

Receiving neuron

Neurotransmitterbroken downand released

Neurotransmitter

Receptor

Na+

Na+

Ion channel opens

Ion channel closes

Transmission of a Signal at Synapses

Figure 7.10, step 7

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