Bio22 Human Physiology - Nervous System Homework 1. Graded potentials are short lived and travel only short distances. Action potentials are long lasting and travel long distances. Where do graded potentials occur? Where do action potentials occur? What is the difference in membrane channels in these two locations and how does this relate to the differences between graded potentials and action potentials? 2. If the resting membrane potential of a neuron is -70mV, give an example of the membrane potential for a depolarized cell and explain what is happening. If the resting membrane potential of a neuron is -70mV, give an example of the membrane potential for a hyperpolarized cell and explain what is happening. 3. Once AP has begun, second AP can't trigger for about 2 msec, Why? 4. What are the two factors that affect the speed of action potentials? 5. Describe the difference between continuous conduction vs saltatory conduction down the length of a neuron and how this affects the speed of action potentials. 6. What is the cause of multiple sclerosis? What is the effect of MS? How does MS lead to such a wide range of symptoms? 7. Describe three ways that neurotransmitters are terminated. What happens if neurotransmitter termination is blocked? 8. What effect does an EPSP have on the membrane potential? What effect does an IPSP have on the membrane potential? What happens to the membrane potential when both an EPSP and an IPSP stimulate a neuron?
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Graded potentials occur in the dendrites and cell body of a neuron. Action potentials occur in the axon of a neuron. The difference in membrane channels between these two locations is that graded potentials are generated by the opening and closing of ligand-gated Show more…
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1.) ____ of the neuron experience(s) resting membrane potential because of the presence of ____ that are the dominant contributors to the process. A. Dendrites, pumps B. Soma, ligand-gated channels C. Axon, voltage-gated channels D. Terminals, receptors E. All regions, leak channels 2.) Glia provide supportive nervous system functions such that: A. Ependymal cells provide immune responses B. Microglia circulate CSF C. Oligodendrocytes regulate substances entering the brain from capillaries D. Schwann cells myelinated axons in the spinal cord E. Astrocytes perform signal cessation by absorbing neurotransmitter 3.) Resting membrane potential: A. Sits close to potassium equilibrium potential because potassium voltage-gated channels are more numerous than sodium non-gated channels B. Utilizes high levels of energy because it is mainly established by the Na/K ATPase C. Is a result of high intracellular sodium and large anionic proteins D. Produces an electrochemical gradient that favors sodium efflux through voltage-gated channels because of its large driving force E. No option is correct 4.) Flow of potassium across a typical neuron embrace leads to ____ events that move the neuron ____ threshold, while ____ has the opposite response. A. EPSP... toward... sodium B. IPSP... away from... calcium C. Negative feedback... directly to... protein D. Positive feedback... closer to... chloride E. No option is correct 5.) Positive feedback occurs when a factor ____. An example happens during ____, which involves the ion ____ and an off-switch called ____. A. Continually decreases... resting repolarization phase... potassium... channel inactivation B. Reverses itself... action potential depolarization phase... potassium... channel closing C. Continually increases... action potential depolarization phase... sodium... channel inactivation D. Moves toward homeostasis... synaptic transmission depolarization phase... calcium... channel activation E. No option is correct 6.) Match the letter with the statement, some may require more than one. A. Rest B. Depolarization C. Repolarization D. Hyperpolarization ____ 1. Mediated by voltage-gated channels ____ 2. Requires sodium influx ____ 3. Phase of action potential ____ 4. Occurs when potassium channels close ____ 5. Involves a positive feedback loop
Adi S.
The value of the action potential -- how much greater the electric potential is inside the axon as compared to outside the axon -- is around 30 mV for the average neuron in humans. If the length constant of an axon is about 2 mm, at what distance x (to the nearest tenth of a mm) from the end of the axon where this action potential is applied would the potential difference across the membrane become less than 4.3 mV (which is a very weak signal)? (And this fast decay of the potential difference is why the action potential must be regenerated with further depolarization along the axon. With additional depolarization down the length of the axon, the action potential is thus maintained as a strong voltage pulse -- again, with a maximum value of around 30 mV -- that can travel along the entire length of axons, which can be over a meter long!) Again, we can use the equation that relates the potential difference across a membrane as a function of how far from the end of the axon this potential difference is measured, i.e., ΔVm = Voe^-x/λ.
Cyra Jelle C.
1) What causes the membrane potential to return to the normal negative value during the repolarization phase of an action potential? Select one: a. Closing of voltage-gated K+ channels b. Opening of ligand-gated Na+ channels c. Closing of voltage-gated K+ channels d. Opening of voltage-gated Na+ channels e. Opening of voltage-gated K+ channels 2) Neuronal cells on your taste buds initiate an action potential when they detect specific flavor molecules. Cell surface proteins that detect flavor molecules and initiate an action potential could be: Select one: a. Extracellularly ligand-gated sodium channels b. Intracellularly ligand-gated sodium channels c. Aquaporin channels d. Mechanically gated channels e. Potassium leak channels 3) Translocation of most proteins into the ER requires all of the following EXCEPT a(n): Select one: a. Signal recognition particle b. Signal sequence c. SRP receptor d. Importin receptor e. Ribosome 4) Which of the following describes a transporter that requires ATP hydrolysis to move solute A and solute B out of the cell? Select one: a. A passive symport b. An active uniport c. An active antiport d. A passive antiport e. An active symport 5) A vesicle traveling down an axon on a microtubule towards a synapse is being pulled by which type of motor? Select one: a. Dynein b. Kinesin c. Myosin d. Filamin e. Actin 6) Which of the following proteins is likely to require vesicular transport to reach its functional destination in the cell? Select one: a. The Na/K pump b. Signal peptidase c. RNA polymerase d. Aconitase (catalyzes the first step in the citric acid cycle) 7) Based on their location in the cell, we can conclude that the tubulin protein monomers that form microtubules must be synthesized... Select one: a. In the nucleus b. On rough ER c. By free ribosomes in the cytosol d. By tubulin synthase e. On smooth ER
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