front 1 What causes an axon potential to occur at the axon hillock? | back 1 Depolarization to threshold |
front 2 What happens at threshold? | back 2 Sodium channels open |
front 3 What happens if there is a weak stimulus at the axon hillock and threshold is not reached? | back 3 The signal just decays |
front 4 Do action potentials always have the same amplitude and the same duration? | back 4 Yes |
front 5 What happens to sodium voltage-gated channels at threshold? | back 5 They open |
front 6 Explain how the positive feedback loop maintains the rising phase of the action potential. | back 6 Depolarization causes some sodium channels to open which results in more depolarization which opens more sodium channels , etc |
front 7 The rising phase of the action potential ends when the positive feedback loop is interrupted. What two processes break the loop? | back 7 Sodium channels inactivate , potassium channels open |
front 8 Describe the two gates on the voltage-gated sodium channels? | back 8 1. Voltage gate opens when threshold is reached 2. Inactivation gate which closes at +30 mV |
front 9 When does the voltage-sensitive gate open | back 9 IN response to depolarization |
front 10 What is the function of the time-sensitive inactivation gate? | back 10 To stop the depolarization phase and to determine the duration of the absolute refractory period |
front 11 What happens to the voltage gated sodium channels at the peak of the action potential? | back 11 They inactivate |
front 12 When do the voltage-gated potassium channels open | back 12 They begin to open as soon as the membrane reaches threshold, but they are slow to open and do not fully open until the peak of the depolarization phase |
front 13 What happens when the voltage-gated potassium channels open and the potassium moves out of the cell? | back 13 The membrane repolarizes |
front 14 What is hyperpolarization? | back 14 Membrane potential greater than ( more negative than ) -70 |
front 15 During the action potential, when does sodium permeability increase rapidly? | back 15 during the rising phase of the action potential |
front 16 Why does hyperpolarization occur? | back 16 The potassium channels are slow to close and they remain open allowing potassium to approach its equilibrium potential of -90 mV |
front 17 During the action potential, when does sodium permeability decrease rapidly? | back 17 during repolarization |
front 18 During the action potential, when does potassium permeability decrease slowly? | back 18 during hyperpolarization |
front 19 The rapid increase in sodium permeability is responsible for _____. | back 19 the rising phase of the action potential |
front 20 The rapid decrease in sodium permeability and simultaneous increase in potassium permeability is responsible for _____. | back 20 the repolarization of the cell |
front 21 The slow decline in potassium permeability is responsible for _____. | back 21 the hyperpolarization |
front 22 What is the absolute refractory period? | back 22 Time when another action potential cannot be initiated regardless of the intensity of stimuli |
front 23 Why can't a neuron generate another action potential during the absolute refractory period? | back 23 The sodium channels are inactive |
front 24 What is the relative refractory period? | back 24 Time when another action potential can only be initiated if the initiating stimulus is suprathreshold ( ie larger than normal ) |
front 25 What two factors does conduction velocity depend on? | back 25 Axon diameter and myelination |
front 26 What is the effect of axon diameter on conduction velocity? | back 26 Direct, as diameter increases , so does conduction velocity |
front 27 What is the effect of myelin on conduction velocity? | back 27 Direct, as the degree of myelination increases , so does conduction velocity |
front 28 Why do myelinated axons conduct action potentials faster than non myelinated axons? | back 28 The action potential is reinitiated less frequently |
front 29 If potassium channels were suddenly opened , in which direction would potassium ions move ? | back 29 Into the cell |
front 30 What prevents the “peak” of the action potential from reaching ENa? | back 30 Sodium channel inactivation |
front 31 Curare binds to and blocks the acetylcholine receptor at the neuromuscular junction. An isolated nerve muscle preparation treated with a less-than-saturating dose of curare would be associated with a decrease in the: | back 31 amplitude of EPSPS. |
front 32 Jim observes a cell that has wrapped itself around the axons of several neurons. | back 32 Oligodendrocyte (CNS) |
front 33 Jim observes a cell that has wrapped itself around the axon of a single neuron. He remembers reading a paper that suggests that some axons can regrow in the presence of this glial cell. | back 33 Schwann cell (PNS) |
front 34 Jim observes a cell that is close to a synaptic cleft. He observes the same cell type at a blood-brain barrier. | back 34 Astrocyte |
front 35 Jim observes a cell that is engulfing debris. | back 35 Microglia |
front 36 Jim observes many of these cells surrounding the central canal of the spinal cord. | back 36 Ependymal cell |