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Nervous System
one of the smallest systems, but most complex
it depends on electrical activity
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Nervous and Endocrine Systems
Control and adjust activities of other systems.
Use Chemical communication
Nervous System - rapid but brief responses
Endocrine - slower but often lasts much longer
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Functions:
Sensory Input - mnitoring stimuli occuring inside and outside the body
Integration - interpetation of sensory input
Motor output - response to stimuli by activating effector organs
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An overview of the Nervous System
2 anatomoical subdivision
- CNS Central nervous System
- *Brain and Spinal Cord
- *Integrating, processing and coordinating
- *Intelligence, memory, learning and emotion
- PNS Peripheral Nervous System
- *Provides sensory information to the CNS
- *Carries motor commands to peripheral tissues
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Subdivision of the PNS
The PNS is divided into 2 subdivisons
The Afferent division of the PNS brings sensory information to the CNS
The Efferent division carries motor commands to the muscles and glands
- *The efferent division is divided into 2 subdivisions:
- **Somatic Nervous Sysgtem (SNS) Skeletal Muscle
- **Autonomic Nervous System (ANS) Cardiac, Smooth, Glandular
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Subdivisions - Continued
The efferent division begins inside the CNS and ends at the Effector
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The Autonomic Nervous System is further divided into the
- Sympathetic - Fight Fight Fight
- *Activated during exercise, excitement, and emergencies
- Parasympathetic rest and digest
- *Concerned with conserving energy
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Cellular Organization in Neural Tissue
Neural tissue contains two distinct cell types
Neurons: responsible for the transfer and the processing of information in the nervous system
Neueoglia: Support Cells
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Neuroglia
- Neuroglia have many functions including:
- *providing the framework for the neural tissue
- *maintaining the intercellular environment of the neuron
- *Act as phagocytes (protection)
- 100 billion neuroglia or glial cells
- *roughly 5 tines the number of neurons
- Types
- *CNS
- **Astrocytes
- Microglia
- Ependeymal Cells
- Oligodendrocytes
- PNS
- *Satellite Cells
- *Schwan Cells
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Astrocytes
Are the largest and the most numerous glial cells.
- Have a variety of functions:
- Maintaining the blood brain barrier
- Creating a three dimensional framework for the CNS
- Performing repairs in damaged neural tissue
- Guiding neuron development
- Controlling the intersitial enviorinment
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Microglia and Ependymal
Produce the CSF
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Oligodendrocytes
- Produce a myelin sheath in the axons (insulating sheath)
- Creates a faster impulse conduction along the axon
Nodes of Ravier is the jumping action called saltatory from node to node
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Neuroglia of the PNS
Satellite Cells - are found in assoc. of the cell body of the neurons
Regulates nutrients for the body
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Neuroglia of the PNS
Schwann Cells
Counterpart to the oligodendrocytes
Peripherial Cells
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CNS Spinal Cord
White Matter = myelinated axons (lighter in appearance)
Grey Matter = non myelinated axons, cell bodies, and dendrites (Darker in Appearance)
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Pseudounipolar Neuron
the cellbody is more in the center of the extension away from the tree portion.
Brings in Sensory information
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Neuron Calssification Functional:
3 types
- *Sensory Neuron
- **Send Nerve impulses from a sense organ (receptor) to the CNS
- *Interneuron
- **Contained within the CNS
- **Receives Impulses form the Sensory Neurons and/or Interneurons
- *Motor Neuron
- **Sends nerve impulses away from the CNS to an Effector
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Nervous Tissue
Bundles of Axons in the PNS = Nerves
Bundles of Axons in the CNS = Tracts
Collection of the cell bodies in PNS = Ganglia
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Transmission of a Nerve Impulse
What Exactly is an "Impulse"
Na+ ion movement across a membrane
polarity change of membrane surface (transmembrane potential)
Travels along the membrane surface like a "Domino Effect"
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Saltatory Conduction
Current passes through a myelinated axon only at the nodes of Ranvier
Voltage gated Na+ channels are concentrated at these nodes
Action potentials are triggered only at the nodes and jump from one node to the next
much faster than conduction along unmyelinated axons
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