Use the above diagram and table to answer the following questions. Inside Artificial Cell Outside Artificial Cell 5 % glucose 10% glucose 5 % NaCl 5% NaCl a. Assume the membrane is permeable to both solutes, will NaCl move across the membrane? Explain your answer. No, Na+ and Cl- ions will not diffuse through the membrane because the concentrations of NACl inside and outside the artificial cell are equal. Ions diffuse through a permeable membrane down the concentration gradient (Saladin, 2009).
That is, from a region of high solute concentration to a region of low solute concentration. In this case, the concentration of solute inside the artificial cell is equal to the solute concentration outside; hence, there is no movement of Na+ and Cl- ions across the membrane. b. Assume the membrane is permeable to both solutes; does the concentration of NaCl affect the movement of glucose through the membrane? Explain your answer. No, the concentration of NaCl will not affect the diffusion of glucose across the membrane.
Solutes diffuse through the permeable membrane due to the difference in concentration per kind of solute (Saladin, 2009). That is, Na+ and Cl- ions will move across the membrane if there is difference between the NaCl concentration inside and outside the artificial cell. In the same manner, glucose molecules will move across the permeable membrane due to concentration difference of glucose inside and outside the artificial cell. Since Na+ and Cl- ions are different from glucose molecules, the NaCl concentration will not affect the diffusion of glucose across the membrane. c. Assume the membrane is permeable to both solutes, will we detect osmotic pressure in the cell after 1 hour?
Explain your answer. Yes, an osmotic pressure will likely be detected due to the different concentration of glucose inside and outside the artificial cell. Glucose molecules will move across the permeable membrane down the concentration gradient: from outside, glucose molecules will diffuse into the artificial cell. d. Assume the membrane is impermeable to both solutes. Is the extracellular fluid hypertonic, hypotonic, or isotonic to the cell? The extracellular fluid is hypertonic with respect to the concentration of glucose.
The concentration of glucose outside the artificial cell is greater that the glucose concentration inside the cell. Thus, the cell’s environment is hypertonic. 2. When a meal is ingested, glucose travels from the intestine into the blood stream, causing a spike in blood-glucose concentrations. This spike triggers the release of insulin. Insulin sends a message to liver cells to absorb glucose from the blood stream, bringing glucose levels in the blood back down. This is an example of a. Negative feedback b.
Positive feedback c. Homeostasis d. Both A and C e. Both B and C 3. In one or two sentences, briefly describe the functional relationship between negative feedback mechanisms and homeostasis. Imbalances in the body’s homeostasis require the carefully monitored adjustments by the integrating centers. Feedback is the relationship between the imbalance and the response of the integrating center with regard to the imbalance. The negative feedback results from the response of the body as it reverses the imbalance (Saladin, 2009).
For instance, a decrease in blood sugar level results in negative feedback, instigating the homeostatic mechanisms to raise the blood sugar level, whereas if the sugar level has increased, the mechanisms will trigger a decrease in blood sugar levels. 4. The period after an initial stimulus when a neuron is not sensitive to another stimulus is the ________. a. resting period b. repolarization c. depolarization d. absolute refractory period e. relative refractory period 5. An inhibitory postsynaptic potential (IPSP) is associated with ________. a. a change in sodium ion permeability b.
hyperpolarization c. depolarization d. lowering the threshold for an action potential to occur 6. The ability to see color is the due to a. rods b. cones c. rhodopsin – is a photoreceptor protein d. Both A and C e. Both B and C Rods and cones are the two types of light-sensitive cells in the retina. Rods are extremely sensitive to dim light but can hardly distinguish wavelengths; hence, we only see tones of gray in a dimly lit room. In brighter places, the cones begin to respond, while the rods refrain from functioning.
The retina of a normal person has three types of cones: one type responds strongly to short wavelength light (blue); another type responds to middle wavelength light (green); and the third type responds strongly to long wavelength light (red). 7. The autonomic nervous system does not control ________. a. airway diameter b. contraction of skeletal muscle c. heart rate d. pupil dilation e. stomach activity 8. How do myelin sheaths increase the speed with which action potentials are propagated along an axon? a. They increase the permeability of Na+ ions in the plasma membrane. b. They amplify the action potential by increasing sodium influx along the entire distance of the neuron. c. They cause action potentials to "jump" down the axon rather than travel in a continuous path along every site on the axon. d. All of the above answers apply. 9. The afferent pathway of a neuron is a.
the dendrites b. the cell body c. the axon d. the synapse 10. How do action potentials relay different intensities of information? a. by changing in amplitude relative to the strength of the stimulus b. by changing in frequency relative to the strength of the stimulus c. by changing in speed of travel relative to the strength of the stimulus d. by changing in duration relative to the strength of the stimulus e. by changing in shape relative to the strength of the stimulus 11. If twice as many inhibitory postsynaptic potentials (IPSPs) as excitatory postsynaptic potentials (EPSPs) arrive at a postsynaptic neuron in close proximity, is the integration of signals by the postsynaptic neuron likely to produce an action potential? a. yes b. no 12. If voltage-gated calcium channels in neurons were defective, what effects would this have on the organism?
Voltage-gated calcium channels are ion channels within the cell membrane, mediated by voltage, that enable the influx of calcium ions into the cell. Voltage-gated calcium channels are important in transforming electrical signals received by an action potential to another form, particularly telling the need to raise the intracellular calcium. In addition, they depolarize the cell membrane as each Ca2+ ion enters the cell. The functioning of theses channels are crucial in the neuronal excitability, neurotransmitter release, gene expression, and contraction of muscle.
Voltage-gated calcium channels are very critical for the physiological function of excitable cells in the endocrine glands, brain, cardiac and smooth muscle, skeletal, and other tissues. Defects in these channels have been implicated in the etiology of a diverse group of nerve and muscle disease. Calcium channelopathies in the nervous system have been associated with dominantly-inherited human diseases, ranging from visual disorders to seizures, ataxia, and migraines (Zamponi, 2005, pg. 240).
On the other hand, muscular calcium channelopathies have been linked to a number of human skeletal muscle disorders like hypokalemic periodic paralysis, central core disease, and malignant hyperthermia (Zamponi, 2005, pg. 250). References Saladin, S.K. (2009). Anatomy and Physiology: The Unity of Form and Function, 5th ed. New York: McGraw-Hill Science Engineering. Zamponi, G. W. (2005). Voltage-gated calcium channels. Georgetown, Tex: Landes Bioscience/Eurekah.com.
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