<span>The best source of stem cells which also minimizes the risk associated with stem cell transplantation</span> are stem cells preserved from the umbilical cord of the person. <span>Stem cell transplant is the process in which diseased cells are replaced by the stem cells collected at the time of birth from umbilical cord blood or bone marrow.</span>
Loss of islet beta cells is the pathologic abnormality most likely to be present in her pancreas at the time of her collapse.
<h3>What are islet beta cells?</h3>
The islets of Langerhans, which are cellular islands dispersed throughout the endocrine pancreas in most animals, include four main kinds of cells, the -cell being one of them. The beta-cell primarily produces and secretes the hormone insulin in reaction to glucose, while it can also do so in response to other foods, hormones, and nervous system stimulation. Adult rats have a sluggish mitotic rate in their -cells. Recent research offers fresh perspectives on the -cell's functioning. An major role for insulin/IGF-1 signaling in the control of -cell activity is suggested by the existence of functioning insulin, insulin receptors, and IGF-1 signaling pathway components. Glucokinase (GK) and ATP-dependent potassium channels have also recently been found on insulin secretory granules.
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Calcium levels in the body are maintained by hormones. If the blood calcium level rises above a set point, calcitonin is secreted by the thyroid gland and sets into motion responses to lower the blood calcium back to the set point. If the blood calcium level falls below a set point, the parathyroid gland secretes parathyroid hormone that sets into motion responses to raise the blood calcium. These homeostatic responses are examples of:
a. positive feedback
b. effectors
c. sensors
d. negative feedback
Answer:
d. negative feedback
Explanation:
Negative feedback responses are the ones that counteract the change. Any alterations in the internal body conditions such as blood calcium levels are sensed by receptors. The information is sent to the brain which in turn commands the effectors such as endocrine glands to secrete the required hormones to restore the normal conditions. Here, changes in the calcium levels are counteracted by the secretion of calcitonin and parathyroid hormones and the calcium is maintained within a narrow range. This represents negative feedback.
It takes almost 9 years for the light of Sirius to hit earth