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Bundles of Axons and their sheaths which extend from the Central Nervous System |
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Collections of neuron cell bodies which are outside the Central Nervous System |
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Peripheral Nervous System |
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Spinal: Nerves which originate from spinal cord Cranial: Nerves which originate from brain |
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Afferent/motor: neurons which transmit action potentials from the sensory organs (eyes, ears, skin) to the CNS Efferent/sensory: Neurons which transmit action potentials from the CNS to the effector organs (muscles and glands) |
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Somatic: The system that transmits action potentials from the CNS to the skeletal muscles/voluntary Autonomic: System that transmits action potentials from the CNS to the smooth muscles, cardiac muscles, and glands/involuntary. |
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Sympathetic: Preps body for physical activity Parasympathetic: regulates resting and nutrition related functions like digestion, defection, and urination |
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2 kinds of cells which make up the nervous system |
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Three basic units of a neuron |
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Cell body/Soma: houses nucleus, mitochondria, golgi (secrete neurotransmitters) Axons: sends action potentials away from the cell body. AP begins on the axon hillock. Dendrites:short, bring messages in to the cell body, signals travel down dendrites towards the cell body. |
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Axons are wrapped in ______ |
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Myelin Sheath: fatty wrapping that speeds transmission of action potential down the axon. Produced by neuroglia. |
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If neuron is in the PNS, it is called a ______ ______ |
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If a neuron is in the CNS, it is called a ________________ |
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Gaps in myelin sheath is called ______________ |
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collateral axons can branch into |
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presynaptic terminals/terminal boutons |
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Mature neurons can/cannot undergo mitosis |
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_______ ____________ transmit from the sensory organs to the ________ ________ _________ which sends signals through the _______ __________ to the effector organs. |
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Afferent neurons Central nervous system Efferent neurons |
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Structural classification of neurons |
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Unipolar: one process, cell body hangs off, pseudo dendrite carries signal toward cell body, usually afferent Bipolar: Two processes, one axon and a single dendrite into many branches, specialized afferent neurons Multipolar: several dendrites and one axon, motor or association neurons |
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spinal nerves are afferent/efferent? |
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a neuron that conducts action potentials from one neuron to another within the CNS |
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Glue, many more than neurons, cause brain tumor |
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Oligodenrocyte: binds together and insulates CNS neurons Schwann: Insulates PSN Microglia: Specialized phagocytic cells Astrocytes: Form the blood-brain barrier Ependymal cells: Ciliated move cerebrospinal fluid, non-ciliated secrete cerebrospinal fluid |
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The ability to create an action potential in response to a stimulus |
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2 types of excitable cells |
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Neurons are/are not excitable cells |
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Nueroglia are/are not excitable cells |
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Action potentials are electral signals caused by _____ and their interactions with other ________. |
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The action potential is a disturbance of the __________. |
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A measure of the charge difference across the cell membrane |
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The difference in charge between the outside surface and inside surface of the cell. It is there when the axon is not carrying any signal and we remember that during the resting potential the inside of the neuron is negative. |
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An action potential at rest is ________zed. |
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a membrane is polarized because there are _________ trapped inside the cell, and they bear a _________ charge. |
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sodium (Na+) and potassium (K+) |
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out of the cell through the membrane in active transportbecause there are more Na+ ions outside than inside |
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into the cell by active trasnport because there are more K+ ions inside the axon than the outside. |
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Sodium-potassium exchange pump |
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The sodium ion exchange takes _____ Na+ ions for every ______ K+ ions it takes in. Thus it is more ______ outside than inside. K+ ions tend to ________ while Na+ ions cannot ____ _____. |
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3, 2, positive, diffuse out, leak, diffuse out |
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Sodium gates open, soidum ions rush into the cell according to diffusion. PD: 30 mV |
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positive charge outside and negative inside and thus the charges are separate |
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Sodium gates close and potassium gates open, potassium rushes out of cell according to diffusion. PD: a bit below -85 mV |
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1 Resting Potential 2. Depolarization 3. Repolarization D. Resting Potential Re-Established |
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Resting Potential (description) |
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Sodium and potassium gates are closed while sodium ions are concentrated outside the cell and potassium ions are concentrated inside the cell. PD: -85 mV |
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Resting Potential Re-Established |
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Sodium and potassium gates are closed. Sodium-potassium exchange pump brings the system back to its original state. PD: -85 mV. |
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If a stimulus is strong enough to trigger the action potential... |
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it is called a threshold stimulus |
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If a stimulus does not reach the threshold... |
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it is called a subthreshold stimulus |
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small change in the potential difference which just dies out because the stimulus was subthreshold |
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Absolute refractory period |
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a time when no matter how strong a stimulus is, no action potential can occur. |
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Relative refractory period |
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Neuron is not really ready to create an action potential, but if stimulus is strong enough, it will occur. |
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Two ways an action potential can be conducted down an axon |
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unmyelinated axon and myelinated |
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two schwann cells encompassing several axons |
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two Schwann cells encompassing one axon |
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in unmylenated axon, action potential must travel the _____ ______ |
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carries signals to the synapse wehre the neuron can connect with another cell. |
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signal jumps the synapse to the post-synaptic neuron. (axon releases neurotransmitters which travel across the synapse to start an action potential on the membrane of the next cell) |
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the axon hillock to the synapse |
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In neuromuscular junction with skeletal muscle, action potential is sent _________ |
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to the muscle membrane so that the muscle will ctonract |
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In a neuron-to-neuron synapse, the flow of information is |
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regulated from one neuron to the next. |
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synapses that stop all or some information from passing thru, Most are inhibitory |
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Excitatory chemical synapse |
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uses a neurotransmitter to carry the signal across the synaptic cleft. |
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Events of excitatory chemical response |
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action potential causes calcium channels to open once it reaches the presynaptic terminal. Once action potential is inside the cell, the calcium acts as a signal which affects the synaptic vesicles that hold neurotransmitters to release and then travel to the synaptic cleft which travels to a receptor. If it binds to a receptor it opens sodium channels which allow Na+ ions to enter the postsynaptic neuron which depolarizes the postsynaptic neuron. |
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