1. Why might a muscle fiber need an ample amount of Na + , K + -ATPase on its su
ID: 50020 • Letter: 1
Question
1.Why might a muscle fiber need an ample amount of Na+, K+-ATPase on its surface?
a. as evident by the value of the cell’s membrane potential, muscle fibers are leaky to Na+
b. to counter the effect of numerous action potentials per second
2. The word organ denotes a distinct set of tissues performing one or more specific functions. Therefore, this term can be used to refer to large visceral organs, e.g. the liver, or much smaller structures such as otolith organs. In regard to the otolith organs, what causes the cilia of their vestibular cells to bend?
a, shear force b. inertia of endolymph
3. Recall that the vestibulo-ocular reflex enables the eyes to remain fixed on target and that extrinsic eye muscles are innervated by brainstem -motor neurons. What role does the medial longitudinal fasciculus play in the vestibulo-ocular reflex?
a. central integration b. links the vestibular nuclei with brainstem motor nuclei
4. Descending projections from the vestibular nuclei enable postural adjustments of the head and body. Any stereotypical change in head position that promotes balance is mediated by the vestibulo-cervical reflex. This name stems from the fact that most of the -motor neurons that control the position of the head are located in the motor nuclei of the
a. brainstem b. cervical cord
5. Any stereotypical change in body position that promotes balance is mediated by the vestibulo-spinal reflex. Does this reflex implement the -loop?
a. yes b. no
Explanation / Answer
1. Answer is b. to counter the effect of numerous action potentials per second
Na+K+ATPase is an carrier enzyme that transport the Na+ and k+ ions caross the membrane. Usually there is high conc. of Na+ and low conc of K+. ATPase move 2 K+ ions for every 3 Na+ ions. It maintains the resting potential and regulate the cellular volume.
2. Answer is b. interia of endolymph
Vestibular apparatus consist of membranous labyrinth and bony labyrinth. Both are filled with fluid called endolymph. During linear acceleration of head, the otolish membrane have more specific gravity that lags behind due to interia. This causes the cilia of hair cell embedded in otolish membrane to bend and causes excitation of vestibular afferent supplying these cells.
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