| Term | Definition |
|---|
| parts of a neuron? | cell body with a nucleus and organelles, dendrites, axon, axon terminal |
| role of nucleus and organelles? | direct cellular activity |
| role of dendrites? | receive incoming signals |
| role of axon? | transmit electrical signals from the cell body to the axon terminal |
| what happens at the axon terminal? | neurotransmitters are released |
| what are interneurons? | neurons that lie entirely within the CNS |
| what is a synapse? | the region where an axon terminal meets its target cell |
| what is the target cell called? | postsynaptic cell |
| what is the presynaptic cell? | the neuron that releases the chemical signal |
| what is the region between the presynaptic cell and the postsynaptic cell? | synaptic cleft |
| what is the axonal transport? | the way by which material (proteins and organelles) is transported between the cell body and the axon terminal |
| what is the function of glial cells? | provide physical support and direct growth of neurons during repair and development |
| what are Schwann and satellite cells? | glial cells associated with the peripheral nervous system |
| what are the glial cells found in the CNS? | microglia, oligodendrites, astrocytes and ependymal cells |
| what are microglia? | modified immune cells that act as scavengers |
| what do Schwann cells and oligodendrites form? | insulating myelin sheaths around neurons |
| what are the nodes of Ranvier? | sections of uninsulated membrane occurring at intervals along the length of an axon |
| where are neural stem cells found? | in the ependymal layer |
| what influences membrane potential? | the concentration gradients of ions across the membrane and by the permeability of the membrane to those ions |
| what does the Goldman-Hodgkin-Katz (GHK) equation predict? | membrane potential based on ion concentration gradients and membrane permeability |
| what changes the permeability of a cell to ions? | when ion channels in the membrane open and close |
| how many ions must move to significantly change the membrane potential? | only a few |
| what causes gated ion channels in neurons to open or close? | chemical or mechanical signals or depolarization of the cell membrane |
| what are graded potentials? | depolarizations or hyperpolarization whose strength is directly proportional to the strength of the triggering event |
| what happens to graded potentials as they move through the cell? | they lose strength |
| what is local current flow? | the wave of depolarization that moves through the cell with a graded potential |
| what are action potentials? | rapid electrical signals that travel undiminished in amplitude from the cell body to the axon terminals |
| where/when do action potentials begin? | in the trigger zone if either a single graded potential or the sum of multiple graded potentials exceeds a minimum depolarization |
| what is a threshold? | the minimum depolarization that will initiate an action potential in the trigger zone |
| what do depolarizating graded potentials do to a neuron? | make a neuron more likely to fire an action potential |
| what do hyperpolarizing graded potentials do to a neuron? | make a neuron less likely to fire an action potential |
| what is the all-or-none principal? | states that stimuli great enough to bring the membrane to threshold will produce action potentials of identical magnitude |
| what is the rising phase of the action potential due to? | increased Na+ flow into the cell |
| what is the falling phase of the action potential due to? | K+ flow out of the cell |
| what is overshoot? | the point during an action potential when the inside of the cell has become more positive than the outside |
| what do the voltage-gated Na+ channels of the axon have? | a fast activation gate and a slower inactivation gate |
| what is absolute refractory period? | the brief period of time, after an action potential has begun, during which a second action potential cannot be triggered, no matter how large the stimulus |
| what happens during the relative refractory period? | a higher-than-normal graded potential is required to trigger an action potential |
| when does excitatory postsynaptic potential (EPSP) occur? | when sodium channels are opened and depolarizes neuron, making it easier to fire |
| what results in local hyperpolarizations? | inhibitory postsynaptic potential (IPSP) |
| what converys information about the strength and duration of a stimulus? | the frequency of action potential propagation |
| when do few ions cross the membrane? | during an action potential |
| what restores Na+ and K+ to their original compartments? | NA+ -K+ -ATPase |
| what is conduction? | the movement of an action potential through the axon |
| what speeds up action potential conduction and how? | larger axon diameter and increased membrane resistance; by increasing membrane resistance and decreasing current leakage |
| what is saltatory conduction? | the apparent jumping of action potentials from node to node |
| what does change in blood K+ concentration affect? | resting membrane potential and the conduction of action potentials |
| what is hyperkalemia? | too much potassium in the blood |
| steps of electrical signals | 1. Graded potential enters trigger zone; 2. voltage-gated Na+ channels open and Na+ enters axon; 3. positive charge spreads along adjacent sections of axon by local current flow; 4. local current flow causes new section of the membrane to depolarize; 5. the rafractory period prevents backward conduction; loss of K+ repolarizes the membrane |
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