Which of the following statements is FALSE?
A. Synaptic input onto skeletal muscle cells is always excitatory, whereas inputs to smooth muscle cells may be either excitatory or inhibitory.
B. A single smooth muscle cell may be innervated by both a sympathetic neuron and a parasympathetic neuron.
C. Contractile activity of smooth muscle cells does not normally require Ca2+.
D. In the absence of any neural input, skeletal muscle cannot generate tension.
E. Ca2+ that activates contraction of smooth muscles can come from either the ECF or from the sarcoplasmic reticulum.
C
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The membrane proteins that are sensitive to extracellular materials are called
A) receptor proteins. B) channel proteins. C) carrier proteins. D) anchor proteins. E) identifier proteins.
The circulatory system helps to maintain normal body temperature.
Answer the following statement true (T) or false (F)
Why do things look blurry underwater without dive goggles or a mask?
A) The water magnifies the image because it is denser than the lens of the eye. B) Light moves more slowly through the water, causing images to appear larger and closer. C) Rather than air, light is moving from water into the cornea and is thus refracted too little for a sharp focus. D) The cornea does not function in water, causing the image to appear larger and closer. E) Light waves are scattered by the water before reaching the eye, causing the image to appear blurry and unclear.
Actions that automatically change the position of the head in response to a sudden loud noise are the ________.
Fill in the blank(s) with the appropriate word(s).