Concept explainers
(a)
To calculate:
The conduction time from A to B in a single axon if its conduction velocity is 60 m/sec.
Introduction:
Synapse can be defined as a junction present between the two neurons. It comprises of a tiny gap through which the impulses pass by the diffusion of a neurotransmitter. The electrical or chemical signal is passed from one neuron to another neuron or the target.
(b)
To calculate:
The conduction velocities of the three neurons if the total conduction time is 1/60 sec.
Introduction:
Synapse can be defined as a junction present between the two neurons. It comprises of a tiny gap through which the impulses pass by the diffusion of a neurotransmitter. The electrical or chemical signal is passed from one neuron to another neuron or the target.
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Human Physiology: From Cells to Systems (MindTap Course List)
- Answer the following questions regarding conduction of action potentials using the velocities given on p. 100: a. How long would it take for an action potential to travel 0.6 m along the axon of an unmyelinated neuron of the digestive tract? b. How long would it take for an action potential to travel the same distance along the axon of a large myelinated neuron innervating a skeletal muscle? c. Suppose there were two synapses in a 0.6 m nerve tract and the delay at each synapse is 1 msec. How long would it take an action potential and chemical signal to travel the 0.6 m now, for both the myelinated and unmyelinated neurons? d. What if there were five synapses?arrow_forwardAssume presynaptic excitatory neuron A terminates on a postsynaptic cell near the axon hillock and presynaptic excitatory neuron B terminates on the same postsynaptic cell on a dendrite located on the side of the cell body opposite the axon hillock. Explain why rapid firing of presynaptic neuron A could bring the postsynaptic neuron to threshold through temporal summation, thus initiating an action potential, whereas firing of presynaptic neuron B at the same frequency and the same magnitude of EPSPs may not bring the postsynaptic neuron to threshold.arrow_forward1) A 100-um diameter nerve axon has the following properties: rm = 2.5 x 104 ohm x cm, ri = 1 x 105 ohm/cm, r0 = 0, cm = 3 x 10-8 F/cm. The permeability to Cl- is very high and Cl- ions are at resting potential Vm. A steady inward current is injected into the axon resulting in a Vm of -110 mV at the site of current injection. If the Vm 3 mm from the site of injection is -94.5 mV, what is the resting Vm?arrow_forward
- Give typed explanationarrow_forwardChanges in ion permeability or ion concentration can alter the resting membrane potential of a neuron. For each of the following, select whether each condition would cause hyperpolarization (H), depolarization (D), or very little change (LC) in the resting membrane potential. A. Increase in [K*]out [Select] B. Increase in [Na]out [Select] C. Increase in Na+ permeability [Select] D. Adding TTX [Select] E. Adding dinitrophenol (a metabolic poison) [ Select]arrow_forwardSequence the following list of events of a neuronal action potential by placing 1 next to the first event, 2 next to the second event, and so on. a. _____ The activation gates of voltage-gated Na+ channels open, Na+ flood the cytoplasm, and depolarization occurs. b. _____ K+ continue to flow out of the axon until the membrane is hyperpolarized. c. _____ Local potentials cause the membrane to depolarize to threshold. d. _____ The inactivation gates of voltage-gated Na+ channels close as voltage-gated K+ channels open, K+ begin to exit the axon, and repolarization begins. e. _____ Repolarization continues and Na+ channels return to restingarrow_forward
- Given the steps shown below, which of the following is the correct sequence for transmission at a chemical synapse? 1. neurotransmitter binds with receptor 2. sodium ions rush into neuron's cytoplasm 3. action potential depolarizes the presynaptic membrane 4. ion channel opens to allow particular ion to enter cell 5. synaptic vesicles release neurotransmitter into the synaptic cleft O 1, 2, 3, 4, 5 O 5, 1, 2, 4, 3 O 2, 3, 5, 4, 1 O4, 3, 1, 2, 5 O 3, 2, 5, 1, 4arrow_forwardA neuron with a resting membrane potential of -75 mV receives multiple inputs giving rise to the following post-synaptic potentials: -15 mV, 20 mV, -5 mV, 7 mV, and 22 mV. The threshold is -50 mV. What will be the outcome? An action potential (AP) will be generated because there are more positive than negative inputs а. b. No action potential because the presence of a single IPSP is sufficient to prevent an AP О с. An action potential (AP) will be generated because the sum exceeds the threshold O d. An action potential (AP) will be generated because the sum of inputs is a positive value Ое. No action potential (AP) will be generated because the sum of inputs is below the thresholdarrow_forwardPlease explain what is going on in the picture below.arrow_forward
- In Japan, the consumption of “Fugu” (a kind of sashimi sushi) is considered to be a “manly” act. The danger associated with consuming Fugu is due to the presence of tetrodotoxin, a potent neurotoxin found in various organs of the pufferfish. a. If the Fugu toxin on a neuron “driving” toward Ex of most permeable ion, is an action potential more or less likely under these conditions? b.Which (flaccid or tonic) is the result in this case? What would be the associated physical symptoms of this condition?arrow_forwardYou are examining a postsynaptic neuron that has a resting membrane potential of -70 mV and a threshold of -55 mV. If an inhibitory presynaptic neuron creates an IPSP of -5 mV and two excitatory presynaptic neurons have EPSPS of 10 and 12 mV, will the postsynaptic neuron fire an action potential if all three pre- synaptic neurons fire at the same time? In your answer describe EPSPS, IPSPs, temporal or spatial summation as appropriate.arrow_forwardName and describe the roles of key molecules and membrane structures in maintaining axon membrane resting potential of-70 mV Name and describe the roles of key molecules and membrane structures in propagation of axon membrane action potentials during depolarization at +35 mV Explain why they myelin sheath of white matter neurons allows faster action potential transmission than that of neurons found in gray matter.arrow_forward
- Human Physiology: From Cells to Systems (MindTap ...BiologyISBN:9781285866932Author:Lauralee SherwoodPublisher:Cengage Learning