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178 Cards in this Set
- Front
- Back
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Nervous system
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The master controlling and communicating system of the body
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Sensory input
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Monitoring stimuli occurring inside and outside the body
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Integration
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interpretation of sensory input
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Motor Output
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Response to stimuli by activating effector organs
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Central Nervous System (CNS)
Where is it located? |
-Integration and command center
-Brain and spinal cord |
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Peripheral Nervous System (PNS)
Where is it located? |
-Carries messages to and from the spinal cord and brain
-Paired spinal and cranial nerves |
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(PNS): Sensory Afferent Division
-Sensory Afferent Fibers -Visceral Afferent Fibers |
-Carry impulses from skin, skeletal muscles, and joints to the brain
-Transmit impulses from visceral organs to the brain |
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(PNS) Motor Efferent Division
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-Transmits impulses from the CNS to effector organs
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Somatic Nervous System
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-Conscious control of skeletal muscles
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Autonomic Nervous System (ANS)
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-Regulates smooth muscles, cardiac muscles, and glands
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A) Sensory input
B) Integration C) Motor Output |
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A) Capillary
B) Neuron C) Astrocyte |
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Microglia
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Small, ovoid cells with spiny process
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Function of Microglia
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Phagocytes that monitor the health of neurons
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Ependymal Cells
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Range in shape from squamous to columnar
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Function of Enendymal Cells
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They line the central cavities of the brain and spinal column
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A) Neuron
B) Microglial cell C) Enendymal Cell D) Brain or spinal cord tissue |
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Oligodendrocytes
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Branches cells that wrap CNS nerve fibers
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Schwann Cells (neurolemmocytes)
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Surround fibers of the PNS
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Satellite Cells
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Surround neuron cell bodies with ganglia
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A) Schwann Cells
B) Satellite Cells C) Sensory neuron with schwann cells and satellite cells D) Oligodendrocytes |
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A) Schwann Cells
B) Satelite Cells C) Cell body (soma) of sensory neuron |
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Neurons
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Structural units of the nervous system
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What are neurons composed of
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Body, axon and dendrites
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What nerve cell is long lived, amitotic, and have a high metabolic rate
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Neurons
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Name the two functions of the plasma membrane in neurons
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-Electrical Signaling
-Cell to cell signaling during development |
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Perikaryon or Soma ( Nerve Cell Body)
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Is the major biosynthetic Center
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What does the Perikaryon contain
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-The nucleus and a nucleolus
-Has no centrioles though |
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What is an important feature of the Perikaryon cell
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Has well developed Nissl Bodies (Rough ER)
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Processes
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Armlike extensions from the soma
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What are the two types of processes
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Axons and dendrites
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Dendrites of Motor Neurons
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-Are the receptive, or input regions of the neurons
-Elecrical signals are conveyed as graded potentials |
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What are the features of Dendrites
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-Short, tapering, and diffusely branched processes
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Axons: Structure
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-Slender processes of uniform diameter arising from the hillock
-Usually only one unbranced axon per neuron |
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Axon Terminal
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Branched terminus of an axon
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Axon Function
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-Generate and transmit action potentials
-Secrete neurotransmitters from the axonal terminals |
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Anterograde
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Toward axonal terminal
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Retrograde
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Away from axonal terminal
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Myelin Sheath
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Increase the speed of nerve impulse transmission
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Mylein Sheath physical description
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Whitish, fatte (protien-lipoid), segmented sheath around most long axons
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The mylein sheath is formed by?
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-Schwann Cells in the PNS
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What are two things a schwann cell does for an axon cell
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-Envelopes an axon in a trough
-Encloses the axon with its plasma membrane |
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Neurilemma
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Remaning nucleus and cytoplasm of a schwann cell
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A) Schwann Cell Cytoplasm
B) Axon C) Schwann cell plasma membrane D) Schwann cell nucleus E) Neurilemma F) Mylein Sheath |
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Nodes of Ranvier
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Gaps in the myelin sheath between adjacent schwann cells
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A) Oligodendroglial Cells
B) Axon C) Myelin Sheath D) Node of Ranvier |
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Axons of the CNS
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-Both myelinated and unmyelinated fibers are present
-Nodes of Ranvier are widely spaced |
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White Matter
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Dense collections of myelinated fibers
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Dark Matter
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Mostly soma and unmyelinated fibers
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Multipolar
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Three or more processes
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Bipolar
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Two processes (axon and dendrite)
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Unipolar
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Single, short process
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Sensory (Afferent)
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Transmit impulses toward CNS
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Motor (Efferent)
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Carry impulses away from the CNS
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Interneurons (Associated neurons)
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Shuttle signals through CNS pathways
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Action potentials, or nerve impulses are
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always the same regardless of stimulus
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Voltage
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Meausre of potential energy generated by seperated charge
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Potential difference
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Voltage measured between two points
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Current
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The flow of electrical charge between two points
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Resistance
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Hindrance to change flow
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Insulator
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Substance with high electrical resistance
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Conductor
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Substance with low electrical resistance
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Electrical current and the body
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reflects the flow of ions rather than electrons
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What are the two potentials on either side of the membrane
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-The number of ions is different across the membrane
-The membrane provides a resistance to ion flow |
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Passive or leakage channels
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Always open
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Chemically gated channels
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open with binding of a specific neurotransmitter
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Voltage-gated channels
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open and close in response to membrane potential
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Mechanically gated channels
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open and close in response to physical deformation of receptors
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A gated channel is open when
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a neurotransmiter is attached to the receptor
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A gated channel is closed when
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a neurotransmitter is not bound to the extracellular receptor
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A) Receptor
B) Neurotransmitter chemical attached to receptor C) Chemically gated ion channel closed D) Chemically gated ion channel opens |
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When is a voltage gated channel close
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When the intracellular enviroment is negative
-Na cannot enter the cell |
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When is a voltage gated channel open
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When the intracellular enviroment is positive
-Na can enter the cell |
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A) Voltage-gated ion channel (Closed)
B) Membrane voltage changes C) Voltage-gated ion channel opens |
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When gated channels are open
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movement is along their electrochemical gradients
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When gated channels are open where does voltage change
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across the membrane
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When do ions move across their chemical gradient
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When they move from an area of high concentration to an area of low concentration
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When does ions move along their electrical gradient
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When they move toward an area of opposite charge
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Electrochemical Gradient
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The electrical and chemical gradients taken together
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What causes a change in resting membrane potential
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-different concentrations of Na, K, Cl, and protien anions (A-)
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Ionic differences are the consequence of
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Operation of the sodium-potassium pump
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Know
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Membrane Potentials: Signals
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Used to integrate, send, and recieve information
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Membrane potential changes are produced by (2)
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-Changes in membrane permeability to ions
-Alterations of ion concentration across the membrane |
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Two types of membrane potential signals
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-Graded potentials
-Action potential |
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A) Myelinated axons
B) Soma of oligodendrocyte C) Microtubule D) Node of Ranvier E) Mitochondrion in axoplasm F) Node of Ranvier |
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Depolarization
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the inside of the membrane becomes less negative
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Repolarization
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the membrane returns to its resting membrane potential
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Hyperpolarization
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the inside of the membrane becomes more negative than the resting potential
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A) Depolarizing Stimulus
B) Hyperpolarizing Stimulus C) Depolarization D) Resting Potential E) Resting Poteltial F) Hyperpolarization |
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Graded potentials
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Short-lives, local changes in membrane potential
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Sufficiently strong graded potentials can initiate
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Action Potentials
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A) Depolarized region
B) Stimulus C) Depolarization D) Spread of Depolarization |
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Graded potentials can only travel over
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short distances
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Action potentials are only generated by
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muscles cells and neurons
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These do not decrease in strength over distance
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Action Potentials
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Nerve Impulse
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An action potential in the axon of a neuron
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Action Potential: Resting State
Activation gates: |
Closes in the resting state
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Action Potential: Resting State
Inactivation gates: |
Open in the resting state
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A) Resting State: All gated Na and K channels closed (Na+ activation gates closes; inactivation gates open)
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What happens to Na+ in the depolarization phase
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Permeability increases; membrane potential reverses
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What happens to Na+ and K+ gates in the depolarization phase
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Na+ gates are opened
K+ gates are closes |
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Threshold
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a critical level of depolarization
(-55 to -50 mV) |
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At threshold depolarization
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becomes self-generating
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A) Depolarizing phase: Na+ channels open
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Action Potential: Repolarization
Sodium inactivation gates |
Close
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In repolarization (AP) as sodium gates _______, voltage-sensitive K+ gates ________
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Close, Open
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A) Repolarization phase: Na+ channels closing and K+ channels open
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Action Potential: Hyperpolarization
What happens to potassium gates |
They remain open, causing an excessive efflux of K+
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A) Hyperpolarization: K+ channels remain open; Na+ channels closed
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Role of the sodium-potassium pump in repolarization
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Restores the resting electrical conditions of the neuron.
Does not restore the resting ionic conditions |
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What is restored by the sodium potassium pump in repolarization
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Ionic resdribution back to resting conditions is restored
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What are the 4 phases of action potentials
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1) Resting State
2) Depolarization Phase 3) Repolarization Phase 4) Hyperpolarization |
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Propagation of an Action Potential
(Time=0ms) |
-Na influx causes a patch of the axonal membrane to depolarize
-Positive ions in the axoplasm move toward the polarized (negative) portion of the membrane |
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Propagation of an Action Potential (Time=1ms)
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-Ions of the extracellular fluid (Na+) move toward the area of greatest negative charge
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Propagation of an Action Potential
(Time=2ms) |
-The action potential moves away from the stimulus
-Where sodium gates are closing, potassium gates are open and create a current flow |
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Threshold
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-Membrane is depolarized by 15 to 20 mV
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Weak (Subthreshold) stimuli
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are not relayed into action potentials
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Strong (Threshold) stimuli
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are relayed into action potentials
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All-or-none phenomenon
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Action potentials either happen completely, or not at all (off-on)
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How does the central nervous system determine stimulus intensity
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By the frequency of impulse transmission (FM)
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Coding for Stimulus Intensity
-Upward Arrow -Downward Arrow |
-Stimulus applied
-Stimulus stopped |
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AM vs. FM
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-Amplitude Modulation
-Frequency Modulation |
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Coding for Stimulus Intensity
Length of Arrows: Action Potentials: |
-Strength of stimulus
-Vertical Lines |
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Absolute Refractory Period
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Time from the opening of the Na+ activation gates until the closing of inactivation gates
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What are the characteristics of the absolute refractory period
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-Prevents the neuron from generating an action potential
-Ensures that each action potential is seperate -Enforces one-way transmission of nerve impulses |
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A) Absolute refractory period
B) Relative refractory period C) Threshold D) Resting membrane potential |
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A) Absolute refractory period
B) Relative refractory period C) Threshold D) Resting membrane potential |
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Relative Refractory Period
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-Sodium gates are closed
-Potassium gates are open -Repolarization is occuring |
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Rate of impulse propagation is determined by:
-Axon diameter -Presence of a myelin sheath |
-The larger the diameter, the faster the impulses
-Myelination dramatically increases impulse speed |
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Saltatory Conduction
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Current passes through a myelinated axon only at the nodes of ranvier
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Saltatory conduction is much faster than conduction along
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unmyelinated axons
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Multiple Sclerosis (MS)
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-A autoimmune disease that mainly affects young adults
-Nerve fibers are severed and myelin sheaths in the CNS become nonfunctional scleroses |
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Nerve fibers are classified according to
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-Diameter
-Degree of myelination -Speed of Conduction |
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Synapses
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A Junction that mediates information transfer from one neuron
-To another neuron -To an effector cell |
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Presynaptic Neuron
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Conducts inmpulses toward the synapse
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Postsynaptic Neuron
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Transmits impulses away from the synapse
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A) Axosomatic Synapses
B) Axodendritic Aynapses C) Axoaxonic Synapses D) Axosomatic Synapses E) Soma of postsynaptic neuron |
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Electrical Synapses
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-Correspond to gap junctions found in other cell types
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Electrical synapses are important in the CNS in
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-Arousal from sleep
-Mental attention -Emotions and memory -Ion and water homeostasis |
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Chemical Synapses
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Specialized for the release and reception of neurotransmitters
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Chemical Synapses are typically composed of two parts
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-Axonal terminal of the presynaptic neuron, which contains synaptic vesicles
-Receptor region on the dendrites or soma of the postsynaptic neuron |
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Synaptic Cleft
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Fluid-filled space seperating the presynaptic and postsynaptic neurons
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Transmission across the synaptic cleft
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-Is a chemical event
-Ensures unidirectional communication between neurons |
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In synaptic cleft nerve impulses reach the axonal terminal of the
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presynaptic neuron and open Ca channels
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______ is released into the synaptic cleft via exocytosis in response to ______
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-Neurotransmitter
-Synaptotagmin |
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Know
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Neurotransmitter bound to a postsynaptic neuron (2)
(TQ) |
-Produces a continous postsynaptic effect
-Must be removed from its receptor |
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Name the three ways that neurotransmitters are removed
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-When they are degraded by enzymes
-Are reabsorbed by astrocytes -Diffuse from the sunaptic cleft |
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Synaptic Delay
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The rate-limiting step of the neural transmission
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Name the two ways that neurotransmitter receptors mediate changes in membrane potential
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-The amount of neurotransmitter released
-The amount of time the neurotransmitter is bound to receptors |
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What are the two types of postsynaptic potentials
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-EPSP and IPSP
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Excitatory Postsynaptic Potentials
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ESPS are graded potentials that can initate and action potential in an axon
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EPSP only use _____ _______ channels
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-Chemically Gated
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______ ______ do not generate action potentials
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Postsynaptic membranes
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Nerotransmitter binding to a receptor at inhibitory synapses reduces the
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postsynaptic neurons ability to produce an action potential
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ESPS must summate ________ or ______ to induce an action potential
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-temporally or spatially
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Temporal summation
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presynaptic neurons transmit impulses in rapid-fire order
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Spatial Summation
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postsynaptic neuron is stimulated by a large number of terminals at the same time
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IPSP can also summate with _______, canceling each other out
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EPSP
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How many different neurotransmitters have been identified
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50
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What are three chemical neurotransmitters
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-Acetylcholine
-Biogenic Amines -Amino Acids |
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Acetylcholine
What is it degraded by |
-Released at the neuromuscular junction
-Degraded by the enzyme acetylcholinesterase |
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Acetylcholine is released by (2) (TQ)
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-All neurons that stimulate skeletal muscle
-Some neurons in the autonomic nervous system |
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Biogenic Amines include
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-Catecholamines, indolamines
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Catecholamines
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-dopamine, norepinephrine, and epinephrine
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Indolamines
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-serotonin and histamine
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A) presynaptic axon terminal
B) Synapse C) Postsynaptic dendrite D) Synaptic cleft E) Synaptic vesicles |
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Neurotransmitters: Amino Acids include
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-GABA
-Found only in the central nervous system |
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Which neurotransmitter acts as natural opiates, reducing our preception of pain
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Peptides
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Peptides bind to the same receptors as _______ and ______
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-Opiates and morphine
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What are the two classifications of neurotransmitters
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-Excitatory and inhibitory
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Excitatory neurotransmitters cause
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depolarization
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which neurotransmitters cause hyperpolarization
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inhibitory
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Excitatory neurotrasmitters
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neuromuscular junctions with skeletal muscle
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Inhibitory neurotransmitters
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neuromuscualr junction with cardiac muscle
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Direct receptor mechanisms
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-neurotransmitters that open ion channels
-Promote rapid responses |
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Indirect receptor mechanisms
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-neurotransmitters that act through second messengers
-Promote long lasting effects |
