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Describe the nervous System?
- The master control and communication center of the body
- and controls cells of the body using nerve cells called neurons and chemical and electrical signals
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What are the functions of the Nervous System?
- Sensory Input
- Intergration
- Motor Output
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Sensory input
Monitoring changes in the chemical environment ( iNside and outside of the body)
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Intergration
Processing and interpreting the information and making a decision about how to respond
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Motor Output
The response usually involving control of muscles and glands
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Central Nervous System
CNS- the integration and command center to include the brain and spinal cord
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Peripheral Nervous System
PNS-The sensory (afferent) and motor (efferent) nerves that receive/relay information to organs and glands communication lines
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Afferent
(sensory)- carry toward
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Efferent
(motor)- carry away
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Somatic Nervous System
Voluntary movement or control using skeletal muscles
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Autonomic Nervous System
(ANS)- involuntary actions including digestion, heart rhythm, breathing and other subconscious commands
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Sympathetic Nervous sysem
- The accelerator system for flight or fight
- Hype up
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Parasympathic Nervous System
- The brake system for fight or flight
- Calms down
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What is the nervous tissue made up of?
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Neurons
- The active cells that transmit electrical and chemical signals
- extreme longevity if given nutrition
- Amitotic (dont divide or replace)
- High Metabolic rates (require continuous supplies of oxygen and glucose
- Conduct impulses from one part of body to another
- The structural unit of nervous system
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Neurogila
(Glial Cells) The cells that support and maintain neurons
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What are some of the Neurogila in the CNS?
- Astrocytes
- Microgila
- Ependymal cells
- Oligodendrocytes
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Astrocytes
- most abundant
- attaches to capillaries and to neurons and their synaptic endings
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What are Astrocytes function?
- determines capillary permeability
- the migration of young neurons and in synapse formation
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Microgila
- Deects neuron injury and differentiates into macrophages which engolf dead cells, pathogens and debris
- Defensive cells
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Ependymal Cells
the cavities of the brain and spinal cord and when ciliated, aids in the movement of the cerebrospinal fluid (produced by this cell)
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Oligodendrocytes
- Covers the axons of the nerves in the CNS and formsan insulating covering called the Myelin sheath.
- Helps speed up
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What are the Neuroglia in the PNS?
- Satellite Cells
- Schwann Cells
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Satellite Cells
- Surrounds cell bodies of the nerves and aids in gathering nutrients for the Neurons
- (Simillar to the Astrocytes in CNS)
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Schwann Cells
- Surround the axons of neurons and forms the myelin sheath and aids in the regeneration of damaged peripheral nerve fibers
- (Similiar to the Oligodendrocytes in the CNS)
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Soma
- The Cell Body or Prokaryon
- contains the nucleous and the majority of the cytoplasm and organelles
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The rough ER of a neuron is called
Nissl Bodies
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Neurofibrils
- Maintain the cell shape and integrity
- Bundles of intermediate filaments within the cell body
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What are clusters of cell bodies within the CNS called?
Nuclei
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What are clusters of cell bodies within the PNS called?
Ganglia
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What are processes?
- They extend from the cell bodies of all neurons
- Dendrites
- Axon
- Myelin Sheath
- Neurileema
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What are the bundles of Neuron processes within the CNS called?
Tracts
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What are the bundles of Neuron processes within the PNS called?
Nerves
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Dendrites
- Short branching extensions that act as a receptor for incoming inforation and convey info toward cell body
- May contain spiky dendritic spines which are points synapse with other neurons
- uses graded potential to relay info to cell body
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Axon
A long single process that directs information away from the cell body toward the synaptic terminal (other end of the axon)
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A long axon is called
Nerve fiber
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Axon Collaterals
a branched axon contains terminal branches (telodendria) with axon terminals
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The ___1___ generates nerve impulses at the _____2______ along the _____3______ to the _______4_____ where neurotransmitters are secreted into the __________5_________ to excite or inhibit another neuron or some organ or gland.
- 1. Axon
- 2.Axon hillock (next to cell body)
- 3. Axolemma (plasma Membraine)
- 4. Axon terminal
- 5. Synaptic cleft (extracelluar space)
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What does the Axon lack?
- Nissl Bodies and the Golgi apparatus
- and proteins must be made and transported from the cell body through the length of the axon and items for degredation and recycling must be transported back to the cell body
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Myelin Sheath
A whitish fatty segmented covering that protects nerve fibers (axons) and electrically insulates the fiber to speed up nerve impulses
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Regions of the brain and spinal cord that contain dense collections of myelinated fibers are referred to as
White Matter
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Regions of unmyelinated fibers are referred to as
Grey Matter
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Which propagate impulses faster Myelinated or Unmyelinated fibers?
Myelinated Fibers
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The sheath cells wrap around the axon the exposed portion is called the............
Neurilemma
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Nodes of Ranvier
- One sheath cell does not connect to its neighbor forming gaps along the axon that are not covered.
- This is where axon callaterals can emerge and the signal is propagated in leaps rather than small steps
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What are the Structural Classifications of Neurons?
- Mutipolar Neurons
- Bipolar Neurons
- Unipolar Neurons
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Multipolar Neurons
- Contains 3 or more processes with only one axon.
- 99% of all neurons
- are the major neuron type of the CNS
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Bipolar Neurons
- Contains an axon and a dendrite that extend from opposite sides of the cell body
- Located in the optic and olfactory areas
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Unipolar Neurons
- A single process that divides into a distal and proximal branch where the distal branch is normally associated with a sensory receptor (peripheral process) and the central process entering the CNS
- should be considered as a single long axon that propagates info to the CNS
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What are the Functional Classifications of Neurons?
- Sensory
- Interneurons
- Motor
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Sensory
- (Afferent) receives sensory stimuli and propagates that info to the CNS
- unipolar with sensory ganglia outside the CNS
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Interneurons
- (Association Neurons) Receives info from sensory Neurons, Processes that info, Makes a decision which it propagates to motor neurons.
- Multipolar Neurons residing within the CNS
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Motor
- (Efferent) receives info on the decision and responds (usually by inhibiting or exciting a musccle group)
- Multipolar with cell bodies located within the CNS
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A Nerve Impulse
Or Action Potential is an electrical impulse that is generated in and conducted through the length of the axon
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Potential energy
energy that is stored, that has the potential to do work
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Electrial potential
for cells- the charge difference across the cell membraine
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Potential Difference
- is the difference in charges separated by some device (semipermeable membrane)
- The greater the potential difference the higher the Voltage
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Kinetic Energy
- when work is done and the potential is relieved, the charge difference is increased or decreased
- (in motion)
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Voltage
Is the energy generated by a separation of charges
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Current
Is the flow of electrical charge (electrons or ions) from one point to another for the purpose of doing work
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Resistance
Is the opposition to flow of electrons or ions from one point to another that decreases the current and is determined by the material for which current passes through
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Insulator
- is a poor electrical conductor
- rubber, plastic, plasma membrane
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Conductor
- Is a good electrical conductor
- Metal, water, Open ion channels
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Ohm's Law
Current=Voltage/resistance
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Ion Channels
Proteins, Nucleic acids and potassium within the cell to give the inside of the cell a net negative charge in respect to the more positive, sodium- dominated extracellular fluid
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Ion Channels can _________1_________a potentialdifference across the________2________.
- 1. Increase or decrease
- 2. Membrane
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What are the ion channels?
- Leakage
- Ligand-gated
- Voltage-gated
- Mechanically-gated
- These channels within the membrane are selective for a particular ion to pass and may allow these ions to pass only under certain circumstances.
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Leakage Channels
are always open (not gated or closeable)
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Ligand-Gated Channels
open when a chemical stimulus binds to the channel, otherwise it remains closed
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Voltage-Gated Channels
Open and close in respones to changes in the Membrane Potential
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Mechanically-Gated channels
Open in respone to physical deformation of the receptor
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Ion Channels allow substances to cross the membrane when open to follow their _______________________________ and prevent transport of those ions when closed.
Electrochemical Gradient
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Electrical Gradient
is the desire of positive and negative to attract one to one another
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Chemical Gradient
is the desire of an equilibrium of chemicals such that a high concentration of a substance moves to an area of lower solute concentration following its own Kinetic energy
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