2 Problem set 2

2 Problem set 2 - BILD 2, Multicellular Life ­...

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Unformatted text preview: BILD 2, Multicellular Life ­ ­Problem set #2 Page 1 1. Some ectotherms and most metabolic endotherms are able to regulate their body temperature, even when the temperature in the environment changes. a. What is an ectotherm? What is an endotherm? b. How can an ectotherm hold its body temperature at a higher level than in its environment? c. How can an endotherm hold its body temperature at a higher level than in its environment? 2. What is a counter ­current exchange system? This kind of system has been observed in the legs and feet of arctic foxes, and it helps to support their survival in this difficult environment. How would that work? 3. a. What is the basal metabolic rate? b. Would a very active animal have a higher basal metabolic rate than a very inactive one? Why or why not? c. Look at figure 40.19. What relationship do you see between a mammal's body mass and its basal metabolic rate? 4. a. If the extracellular concentration of Na+ (which is written [Na+]out) is 140 mM and the inner concentration in a spinal neuron (written [Na+]in) is 10 mM, what is the equilibrium potential for Na+ in this cell? b. Can you tell for the transmembrane potential of this neuron the most inside ­positive value an action potential could reach? 5. Describe the role (or roles) that each of the following things plays in the transmission of information by propagation of an action potential traveling along an axon: a. Na+ b. Ca2+ c. Diffusion d. Membrane proteins e. K+ BILD 2, Multicellular Life ­ ­Problem set #2 Page 2 6. Describe the role (or roles) that each of the following things plays in the transmission of information across a chemical synaptic cleft: a. Na+ b. Ca2+ c. Diffusion d. Membrane proteins e. Synaptic vesicles 7. a. What is the presynaptic cell? What kind(s) of cells can be a presynaptic cell? b. What is a postsynaptic cell? What kind(s) of cells can be postsynaptic cells? c. What is a postsynaptic potential, and what causes postsynaptic potentials? d. What is an excitatory postsynaptic potential (i.e., an EPSP)? e. What is an inhibitory postsynaptic potential (i.e., an IPSP)? 8. Consider the diagram showing the patellar ­tendon reflex. (Figure 49 ­3). It shows four neurons that are connected with one another in some way. Using what you now know about action potentials and synaptic transmission, follow a signal through this reflex arc from the site of stimulation to the site of action, describing ALL of the mechanisms that transmit the signal through this chain of neurons. ...
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This note was uploaded on 02/18/2012 for the course BILD 2 taught by Professor Schroeder during the Spring '08 term at UCSD.

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