Answer the multiple choice problems. describe the reason.

1. The most common adhesive glycoprotein in humans is:
a. integrin c. fibronectin
b. collagen d. hyaluronin

2. Action potentials are transmitted along axons without a loss of
a. amplitude
b. K+
c. Na+
d. all of the above

3. Voltage-gated Na+ and K+ channels are refractory because of movement of a(n)
a. channel inactivating segment
b. gate segment
c. inner vestibule segment
d. outer vestibule segment

4. Neurotransmitters released into the synaptic cleft are
a. in some cases degraded
b. generally retrieved by a symport in the synaptic membrane of the presynaptic cell
c. both a and b
d. retrieved by the post-synaptic cell

5. At the axon terminal neurotransmitters are released when:
a. Na+ enters the terminal through voltage gated Na+ channels
b. K+ enters the terminal through voltage gated K+ channels
c. Ca2+ enters the terminal through voltage gated Ca2+ channels
d. none of the above