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ANS 100 Study Guide for Midterm -2 With Complete Solutions Latest upload
- Course
- ANS 100
- Institution
- University Of California - Davis
ANS 100 Study Guide for Midterm -2 With Complete Solutions Latest upload
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lOMoARcPSD|22014731ANS 100 Study Guide for Midterm #2 What are a few reasons why we need a nervous system? - correct answers It conveys information rapidly over short or long distances to help the body cellular integrate (work together). The nervous system controls predominantly the fine rapid movements of discrete muscles.
Neurons have resting membrane potential like other cells. What sets up this resting membrane potential? How is this resting membrane maintained? - correct answers Resting membrane potential is maintained by Na/K ATPase; they regulate the movement of Na/K. It's maintained by opening or closing ion channels
Neurons are excitable. What do I mean by this statement? How is this achieved? - correct answers It means that neurons can rapidly change their membrane potential. The changes in membrane potential act as electrical signals. Where neurons are promoted to favor action potentials.
Provide me with a diagram that illustrates depolarization, hyperpolarization and repolarization. How do these three differ (or define these three)? - correct answers Depolarization: membrane potential becomes less negative and closer to each other
Hyperpolarization: Membrane potential become further apart and more negative
Repolarization: After Hyper or depolarization going back to resting membrane potential (-70 mV of neuron)
What is equilibrium potential? How does equilibrium potential affect the degree to which membrane potential can change? - correct answers Equilibrium potential: the membrane potential where the flow of ions in and out of the membrane is the same therefor there's no change in membrane potential or a net flow of 0.
What equation (just the name) calculates an ion's equilibrium potential? What equation (just the name) calculates the equilibrium potential of all ions? - correct answers Nerst equation calculates an ion's equilibrium potential (individually)
Goldman Equation calculates the equilibrium potential of all ions (K+, Na+, Cl-)
Sketch and label a typical motor neuron. Label and explain briefly the four functional zones of a neuron (like what we did in Friday's Discussion). - correct answers Four functional zones 1. Signal reception
- Dendrites and the cell body (soma)
- Incoming signal received and converted to change in membrane potential
2. Signal integration
- Axon hillock
- Strong signal is converted to an action potential (AP)
3. Signal conduction
- Axon (some wrapped in myelin sheath)
- AP travels down axon
4. Signal transmission
- Axon terminals
- Release of neurotransmitter
*Image on lecture 19, slide 15*
Distinguish between a graded and an action potential with respect to how they are initiated, the type of change in membrane potential and where they are initiated. - correct answers Graded potential: initiated by opening or closing ion channels in the cell body or dendrites and the change in membrane potential is proportional to the current applied (how many channels are open; more open=larger graded potential)(GP travels short distances) can be hyperpolarized (K+ and Cl- channels open) or depolarized (Na+ or Ca2+ channels open) for changes in membrane potential
Action Potential: initiated when the net graded potential at the axon hillock reaches the threshold potential (occurs in the axon), all-or-none response elicited when the threshold is reached; massive depolarization of membrane potential occurs. lOMoARcPSD|22014731
Always same size, shape, duration, does not decay with distance
With the help of a diagram, demonstrate how a threshold potential needs to be reached before an action potential is generated. What specific ion channels are important in defining the shape of the action potential and how exactly is this achieved? What is the role of Na/K- ATPase? - correct answers lecture 17 slide 13,17; ‐‐
Na+ channels have two gates--> activation which will open at a certain voltage and inactivation gate which is time dependent and allows for an absolute refractory period in which another AP cannot be fired. Inflow of Na+ causes depolarization and when the inactivation gate closes shutting out Na+, membrane potential becomes hyperpolarized
(lecture 17 slide 18) Na+ channels open first = depolarization (peak in AP diagram), K+ channels open more slowly = repolarization (downslope of diagram), membrane potential becomes more negative again; moves towards its resting potential), Na+ channels close due to inactivation gate, K+ channels close slowly (relative refractory period caused by open K+ channels)
Need Na+/K+ ATPase to pump sodium out of the cell (against the gradient) and to pump potassium in (against gradient) in order to put ions back where they were pre-action potential ) bring cell's membrane potential back to normal essentially
Differentiate between temporal and spatial summation. Where are these features important and why? - correct answers Temporal summation: graded potentials that occur at slightly different times can influence the net change. Spatial summation: graded potentials from different sites can influence the net change. Important because signals will be sent at different times (temporal) and different places (spatial). Summing up everything that is happening is essential. It influences the net change, and action potential can only occur when membrane potential at axon hillock reaches threshold. I think that it's also important because you can sum up these signals to create a larger graded potential which increases the AP frequency, → higher Ca concentration in the axon terminal (presynaptic cell?) → more neurotransmitters released → greater signal (???)
Differentiate between and discuss the characteristics underlying absolute and relative refractory period. - correct answers Absolute refractory period: The period from the initiation of the action potential to immediately after the peak. This is the time during which another stimulus given to the neuron (no matter how strong) will not lead to a second action potential. Thus, because Na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials. Inactivation gate is time dependent and once closed, no APs EVER
Relative refractory period: The period during which a stronger than normal stimulus is needed in order to elicit an action potential. Continued K+ flow out of the cell would tend to oppose any depolarization caused by opening of Na+ channels that have recovered from inactivation.
Explain the statements that action potentials are "self- propagating" and "unidirectional". - correct answers Problem set ‐‐
Q:
They are self-propagating because the spread of the current opens channels down the line so there is a constant shift of voltage happening and once the voltage reaches the threshold potential, AP continues to fire. Action potentials are unidirectional because they start at the axon hillock, traveling down the axon towards the axon terminal and there are activation/inactivation gates that prevent flow in the opposite direction. Absolute refractory period prevents backflow because its inactivation gate is controlled by time, not by voltage. The relatively refractory period requires a strong stimulus in order to fire another AP, thus keeping it moving in one direction.
Vertebrate neurons can be myelinated. What is myelin and what is its function? - correct answers Myelination is like plastic wrapping the neuron
Myelin is an insulating layer of lipid-rich Schwann cells wrapped around the axon. They reduce leakage of charge across membranes. The Schwann cells are a type of Glial cell - cells other than neurons that support neuronal function. They are also used to speed up conduction. Also provides support.
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