Tetrodotoxin (TTX) is generally associated with pufferfish, which in fact gain it from symbiotic bacteria residing in them. Interestingly, the pufferfish themselves aren't affected by this neurotoxin. The most plausible explanation for the fish's insensitivity to TTX is
a. the fish lack neurons.
b. the fish have neurons, but with very short axons that enable them to rely entirely on electrical conduction based on local passive current flow.
c. the fish lack voltage-gated sodium channels .
d. the fish have voltage-gated sodium channels, but they have a slightly different sequence from voltage-gated sodium channels found in other organisms, and this difference affects TTX's ability to bind the channel.
D
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Mucosal associated lymphatic tissues (MALT) are
A. clusters of splenocytes located in the lamina propria of mucous membranes. B. aggregates of macrophages located in the intestines. C. clumps of mucous lining the lumen of the gastrointestinal tract. D. aggregates of lymphatic tissue scattered throughout the lamina propria of mucous membranes.
The zona reticularis of the adrenal cortex produces
A) androgens. B) glucocorticoids. C) mineralocorticoids. D) epinephrine. E) norepinephrine.
After an injection of prostaglandin, a cow will usually enter heat within ________________________________________ to ________________________________________ days
Fill in the blank(s) with correct word
Areas of densely packed lymphocytes in the linings of the digestive, respiratory, urinary, and reproductive tracts are called
A) thymic corpuscles. B) nodules. C) lymph nodes. D) tonsils. E) All of the answers are correct.