Bio110exam1PMKey - NAME Student ID BIO SCI 110 B - Midterm...

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NAME……………………………… Student ID……………… BIO SCI 110 B - Midterm Exam – 4:00-4:50, April 23, 2007 AFTERNOON Section - VERSION A KEY
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Short-answer Questions Write your answer in the spaces provided below. For questions requiring two answers, you must get both correct to score a point (no partial credit). 1. The sodium current recorded from a voltage-clamped squid giant axon is zero at potentials of both about -50 mV and +50 mV. Why? At -50 mV Na channels are not open : at +50 mV channels are open, but there is no Na+ current because this is the equilibrium potential for sodium. (Variants on this are OK; e.g. at +50 mV the chemical driving force for Na entry is exactly counterbalanced by the electrical force opposing their entry) 2. The refractory period following an action potential results primarily because Na channels are inactivated and require some time to recover 3. An outward membrane current could result from the efflux of positive (OR Na+, OR K+, OR Ca2+) ions from a nerve cell, or the influx of negative (OR Cl-) ions. 4. Provide a brief definition of an antidromic action potential. An action potential traveling along an axon in the opposite direction to that which it would normally go in the body 5. Over what range of voltages does the opening of voltage-gated sodium channels in an axon increase progressively? From -50 mV to 0 mV (any answer approximating this voltage range, such as - 40 mV to +10 mV, would be accepted) 6. What is the key feature of the voltage clamp apparatus that allowed Hodgkin and Huxley to elucidate the mechanism of the action potential? It allows the membrane potential of a squid axon to be clamped at any desired voltage, irrespective of what currents flow across the axon membrane
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7. Where are sodium channels located in a myelinated axon? At the nodes of Ranvier. 8. Among different types of synapse, the neurotransmitters that get released during synaptic transmission may arise from different sources. Give one example of the source of a neurotransmitter. Examples include: Synthesis of peptide neurotransmitters in the neuron soma Synthesis of neurotransmitter in the nerve terminal from recycled degradation product (e.g. acetylcholine) Direct re-uptake of neurotransmitter from the synaptic cleft (e.g. glutamate) 9. GABA is the most important inhibitory neurotransmitter in the brain and opens postsynaptic channels permeable to Cl- ions. 10. In electrical terms, a capacitor is something that stores electricity (electrical charge) 11. Which of the major ions involved in neuronal functioning has the greatest difference in its concentration between the extracellular fluid and the cytosol? Ca2+ 12. A neurotransmitter receptor that exerts its action indirectly through a second messenger pathway is known as a(n) metabotropic receptor. 13.
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This note was uploaded on 04/14/2010 for the course BIO SCI BIO N110 taught by Professor Leon,chance&parker during the Spring '09 term at UC Irvine.

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Bio110exam1PMKey - NAME Student ID BIO SCI 110 B - Midterm...

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