Describe the membrane properties that enable the pacemaker cells to spontaneously depolarize.
What will be an ideal response?
Answer: Pacemaker cells do not have a resting potential, but rather spontaneously depolarize for three reasons. First, the potassium channels slowly close, reducing K+ outflow. Second, there is a slow inward cation leak channel that allows Na+ entry. Third, there is a calcium channel that opens, allowing Ca++ in. These trigger an action potential in which the depolarizing spike occurs due to the opening of a voltage-gated L-type calcium channel.
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The anther represents the _____ portion of the plant, while the ovules represent the ____ portion of the plant
A. Female ; male B. Male ; female C. Female ; female D. Male ; male
You analyze two daughter cells of Bacteria A immediately after binary fission. Which of the following is ACCURATE about the daughter cells?
A. They have genetic contributions from two different parent cells. B. They are members of the same colony. C. They have genetically identical chromosomes. D. They are members of the same colony and have genetically identical chromosomes. E. They are members of the same colony and they have genetic contributions from two different parent cells.
The presence of which hormone in a mother's
urine indicates that she is pregnant?
a. luteinizing hormone b. follicle-stimulating hormone c. human chorionic gonadotropin d. progesterone e. estrogen
The human population is growing exponentially largely due to
a. higher birth rates b. all of the above c. improved medical treatments and care d. available resources e. lower death rates