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40 Cards in this Set
- Front
- Back
What member of the animal phyla does not have nerve cells?
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sponges
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The CNS (Central Nervous System) includes what? What is the difference between a neuron and glial cell?
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includes brain and spinal cord; 90% GLIAL CELLS (support) and 10% NEURON (excitable cells that communicate via electrical and chemical messages)
Only 2% of brain is neurons |
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What is included in the PNS (Peripheral Nervous System)? What is the difference between the somatic and autonomic nervous system?
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everything outside of CNS; includes the SOMATIC nervous system ( voluntary; controls skeletal muscle) and
AUTOMATIC nervous system (involuntary; regulates activity in smooth muscle, cardiac muscle, and glands of the body ) |
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What produces the nerve impulses?
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plasma membrane of neuron
produces electrical signals (electrical difference across a neuronal membrane measured as millivolts) that are nerve impulses |
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What is the difference in AFFERENT and EFFERENT neurons?
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EFFERENT -transmit information from CNS to periphery effectors (muscles and glands)
Exiting (CNS): Efferent AFFERENT-transmit information from periphery to CNS; sensory neurons Approaching (CNS) :Afferent |
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Interneurons are found where?
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association neurons; found only in CNS as complex interconnections between one neuron and another; complex reflexes, learning, and memory
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What are parts of a basic neuron? What is the functions of these parts? Where is the action potential generated?
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functional unit of nervous system; can produce electrical signals and action potentials where inside of cell becomes positively charged relative to outside of cell; made up of
DENDRITE (cytoplasmic portion that RECEIVES incoming information), SOMA (cell body that CONTNAINS nucleus and most organelles), AXON (long cellular extension which TRANSMITS action potentials/nerve impulses; AXON HILLOCK is closest to the cell body and is responsible for GATHERING action potential) |
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electrical signal travels from sensory neuron to interneuron in the CNS to motor neuron (no direct brain activity)
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reflex arc
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The "electrochemical gradient" that determines how a charged ion will move through a permeable membrane depends on the _______of electrical forces and ______across the membrane.
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The "electrochemical gradient" that determines how a charged ion will move through a permeable membrane depends on the COMBINED EFFECTS of electrical forces and CONCENTRATION DIFFERENCES across the membrane.
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only neurons and muscle cells are ____
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excitable
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Which glial cells produce myelinated axons and where?
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neuroglial cells
support cells...make up 90% of nervous system cells; include oligodendrocyte (produce myelin in CNS), and Schwann cells (produce myelin in PNS) and others (include astrocytes (metabolic support; stem cells), microglia (phagocytic removal cellular debris) |
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What is the difference in white and gray matter?
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WHITE MATTER- myelinated axons in CNS
GRAY MATTER- dendrites/cell bodies in CNS |
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What are nerves?
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bundled myelinated axons in the PNS
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What is myelin?
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layers of plasma membrane from oligodendrocytes (CNS) and Schwann cells (PNS) that FORM INSULATION around the axons of neurons thereby reducing a membrane's ion permeability and increasing the speed of action potential generation; in an unmyelinated axon, conduction velocity is primarily determined by diameter of the axon
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What is saltatory conduction and why is it fast?
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action potential conduction that occurs in myelinated axons where the action potentials jump from Node of Ranvier ( gap of exposed axon in the myelin sheath) to Node
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What is the resting membrane potential? What are the factors that influence this? On each cycle of the sodium/potassium pump, how many of each ion are pumped and in what direction? What is the average value of the resting membrane potential?
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- a potential difference (electrical in nature measured in millivolts) exists across cell's plasma membrane even if the nerve cells are not producing electrical responses;
- factors that influence this are concentration of INTRACELLULAR anions (e.g., proteins), sodium (Na+) and potassium (K+) and presence of sodium and potassium gated channels, potassium (K+) leakage channels, and sodium/potassium pump (2 K+ into cell and 3 Na+ out of cell); - ELECTROCHEMICAL FORCES are acting for sodium ions to move into the cell and potassium ions to move out of the cell (resting membrane is more permeable to POTASSIUM than to sodium, so it moves OUT of cell due to electrochemical gradient); - when neuron is not being stimulated, inside of the cell is more negative than the outside of the cell primarily because of passive leakage of K+ ions across the membrane and it AVG. as -70mV (millivolts) |
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3 factors contributing to resting potential:
Na+/K+ -ATPase (sodium-potassium pump -- Transports 3 Na+ out for every 2 K+ moved in Ion specific channels allow passive movement of ions --K+ channels open more frequently at resting potential --Membrane more permeable to K+ Negatively charged molecules such as proteins more abundant inside cell |
resting membrane potential
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determines how a charged ion will move through a permeable membrane depends on the combined effects of electrical forces and concentration differences across the membrane
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electrochemical gradient
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How do ions flow and in what order during an actions potential? How is an action potential like the falling of dominoes?
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The rapid INWARD diffusion of Na+ followed by the OUTWARD diffusion of K+ producing a rapid change in the membrane potential towards the positive direction and exceeding threshold; action potentials are regenerated along an axon as one action potential serves as the depolarization stimulus for the next action potential
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What is the role of threshold in the all-or-none principle?
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in an excitable cell, the critical value (between -70mV and -55mV) of the membrane potential to which the cell (axon hillock) must depolarized in order to trigger an action potential; this follows the "all-or-none" law
Consider: Positive feedback occurs as the neuron is being depolarized and passes the threshold potential. |
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cell membrane less polarized, less negative relative to surrounding solution, due to increasing the flow of Na+ ions into a neuron at rest
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depolarization
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Both opening of the K+ channel gate and closing of the Na+ channel inactivation gate stops the rapid depolarization that occurs as the "upsweep" of membrane potential peaks during the action potential.
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repolarization/hyperpolarization
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WHICH channel activation gate responds slightly more slowly to depolarization?
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The K+ channel activation gate responds slightly more slowly to depolarization than the Na+ channel activation gate to prevent canceling out each other's effects on membrane potential changes.
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The refractory period is what?
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period following an action potential during which a neuron CANNOT be stimulated to generate another action potential; ensures action potential does not move backward
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NAME 2 gated ion channels
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VOLTAGE gated - open close in response to voltage changes
LIGAND-gated - open and close in response to ligands or chemicals |
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A graded potential is what and in which neurons does it have an important role?
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a neuron undergoes a change in membrane potential that is proportional to (i.e., varies depending on) the strength of the stimulus given to that neuron; important for CONVEYING STIMULUS intensity in SENSORY NEURON.
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Varies based on AXON diameter and/or myelination
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conduction speed
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What is the synapse?
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functional association (junction) of a neuron with another neuron or effector organ ( muscle or gland)...can be electrical or chemical; synaptic cleft is small gap between two successive neurons or between a neuron and an effector
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What is the difference in an electrical and a chemical synapse?
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ELECTRICAL-message (ions) travel between cells via GAP JUNCTION proteins; communication is bi-directional; synapses can be gated; DONOT utilize neurotransmitters
CHEMICAL-makes up most synapses in nervous system; communication is SLOWER than electrical; utilizes NEUROTRANSMITTERS; boundaries are the presynaptic neuron that releases neurotransmitters (chemicals stored in synaptic vesicles which when released via exocytosis must diffuse across the synaptic cleft and by binding to postsynaptic receptors (chemically regulated gates and ligand regulated gates), regenerate the action potential) and the postsynaptic neuron, which contains receptors; most neurotransmitters are synthesized in cytosol |
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synaptic cleft
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junction where nerve terminal meets a neuron, muscle cell, or gland and into which NEUROTRANSMITTER ARE RELEASED
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What is the role of calcium in neurotransmitter release? What happens to the neurotransmitter after it is released?
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triggered by voltage-gated Calcium channels (these channels open in response to arrival of action potential at the axon terminal, allowing influx of calcium ions that cause FUSION OF NEUROTRANSMITTERS containing vesicles to membrane and exocytosis of neurotransmitter); voltage gated channels allow axon and axon terminal function; neurotransmitter diffuses across cleft to interact with receptors on ligand gated channels, triggering DEPOLARIZATION OF POST SYNAPTIC membrane
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postsynaptic cell membrane potential changes due to neurotransmitter binding
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Excitatory postsynaptic potential (EPSP) Brings membrane closer to threshold potential
Inhibitory postsynaptic potential (IPSP) Takes membrane farther from threshold potential (hyperpolarization) |
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synaptic integration
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Refers to the summing of excitatory (EPSP) or inhibitory (IPSP) influences in a postsynaptic neuron
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vertebrate neuromuscular junction activity
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Action potentials are generated in the neuron, STIMULATION of the entry of Ca2+ into the neuron, release of ACETYLCHOLINE into the synapse, and muscle fiber membrane is DEPOLARIZED
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What happens to the neurotransmitter after the message has been delivered?
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neurotransmitter REMOVAL diffusion out of cleft, DEGRAGATION by enzymes (such as ACETYLCHOLINESTERASE), active REUPTAKE across the presynaptic membrane (after which they can be reused), and binding to the receptor (concentration of neurotransmitter primarily determines binding)
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Acetylcholine is found where and where is most abundant? What degrades it?
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released by cholinergic synapse in somatic motor neurons; found in PNS & CNS; most abundant neurotransmitter in PNS and is always an excitatory neurotransmitter; excess degraded by acetylcholinesterase into acetate and choline (which is transported back into the axon terminal to be resynthesized into active neurotransmitter)
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cocaine effects
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by blocking DOPAMINE REUPTAKE from synapses causing disruption of neural signaling and producing profound changes in MOOD AND BEHAVIOR
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Saltatory conduction is a term applied to conduction of action potentials
A. across electrical synapses. B. along the postsynaptic membrane from dendrite to axon hillock. C. in two directions at the same time. D. from one neuron to another. E. along myelinated axons. |
E. along myelinated axons.
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Which of the following are NOT important in chemical synapses?
A. gap junctions B. neurotransmitters C. specific neurotransmitter receptors D. secretory vesicles E. voltage-gated Ca2+ channels |
A. gap junctions
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Synaptic vesicles discharge their contents by exocytosis at the
A. dendrite. B. axon hillock. C. nodes of Ranvier. D. postsynaptic membrane. E. presynaptic membrane. |
E. presynaptic membrane.
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