The iris of the eye contains
A. multiunit smooth muscle.
B. single-unit smooth muscle.
C. skeletal muscle.
D. cardiac muscle.
Answer: A
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An investigator places an isolated neuron in a calcium-free medium. They give the neuron a suprathreshold stimulus and then perform an assay to test whether neurotransmitter is released into the medium. Which of the following outcomes would you predict?
a. No neurotransmitter is detected since influx of calcium into the synaptic knob is required for neurotransmitter release. b. No neurotransmitter is detected since influx of calcium is required in order for the neuron to conduct an action potential. c. Neurotransmitter is detected since calcium is not required for action potential conduction and the initial stimulus was suprathreshold. d. We cannot predict the outcome without knowing whether the neuron was myelinated. e. None of these.
Researchers have found that on the island of Mangaia:
A. experiencing three orgasms per night is typical across the lifespan. B. older women and men instruct young boys in sexual matters. C. older men instruct young girls in sexual matters. D. older men do not have sex.
The thymus contains lymphatic cells as well as secretory _________ tissue
A. muscle B. neural C. epithelial D. osseous E. areolar
Bicarbonate enters and leaves the vertebrate red blood cell by
A) Diffusion. B) Bicarbonate pump. C) Bicarbonate channel. D) Chloride-bicarbonate exchanger.