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Ch. 18 The Endocrine System
Martini - Fundamentals of Anatomy & Physiology 11th Edition
Martini, Nath, Bartholomew11th EditionFundamentals of Anatomy & PhysiologyISBN: 9780136874089Not the one you use?Change textbook
Chapter 18, Problem 24

In Type 2 diabetes, insulin levels are frequently normal, yet the target cells are less sensitive to the effects of insulin. This suggests that the target cells:
(a) Are impermeable to insulin
(b) May lack enough insulin receptors
(c) Cannot convert insulin to an active form
(d) Have adequate internal supplies of glucose
(e) Both b and c

Verified step by step guidance
1
Step 1: Understand the role of insulin in the body. Insulin is a hormone that facilitates the uptake of glucose by target cells, primarily muscle and fat cells, by binding to insulin receptors on their surface.
Step 2: Recognize that in Type 2 diabetes, insulin levels can be normal or even elevated, but the cells do not respond properly to insulin. This condition is known as insulin resistance.
Step 3: Analyze the options given: (a) impermeability to insulin is unlikely because insulin acts by binding to receptors, not by entering the cell; (b) lacking enough insulin receptors would reduce the cell's ability to respond to insulin; (c) inability to convert insulin to an active form is not typical because insulin acts extracellularly by receptor binding; (d) having adequate internal glucose supplies does not explain reduced sensitivity to insulin.
Step 4: Since insulin resistance often involves a reduced number or function of insulin receptors, option (b) is plausible. Option (c) is less likely because insulin does not need to be converted inside the cell to be active.
Step 5: Conclude that the best explanation is that target cells may lack enough insulin receptors, making option (b) the most accurate choice.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Insulin Resistance

Insulin resistance occurs when target cells, such as muscle or fat cells, respond poorly to insulin despite normal or high insulin levels. This reduces glucose uptake, leading to elevated blood sugar. It is a hallmark of Type 2 diabetes and involves impaired insulin signaling pathways.
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Altering Resistance in Blood Vessels

Insulin Receptors and Their Role

Insulin receptors are proteins on the surface of target cells that bind insulin and trigger glucose uptake. A reduced number or malfunction of these receptors can decrease cell sensitivity to insulin, contributing to insulin resistance seen in Type 2 diabetes.
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Sensory Receptors

Mechanism of Insulin Action

Insulin acts by binding to its receptor, initiating a cascade that allows glucose transporters to move to the cell membrane and facilitate glucose entry. Insulin itself is active and does not require conversion inside the cell, so inability to convert insulin is not a typical cause of insulin resistance.
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Action Potential
Related Practice
Textbook Question

Decreased blood calcium level would result in increased:

(a) Secretion of calcitonin

(b) Secretion of PTH

(c) Elimination of calcium by the kidneys

(d) Osteoclast activity

(e) Excitability of neural membranes

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Textbook Question

Pamela and her teammates are considering taking anabolic steroids (synthetic hormones derived from testosterone) to enhance their competitive skills. What natural effects of testosterone are they hoping to gain? What additional side effects might these women expect should they begin an anabolic steroid regime?

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Textbook Question

A researcher observes that stimulation by a particular hormone induces a marked increase in the activity of G proteins in the target plasma membrane. The hormone being studied is probably:

(a) A steroid

(b) A peptide

(c) Testosterone

(d) Estrogen

(e) Aldosterone

Textbook Question

Julie is pregnant but is not receiving prenatal care. She has a poor diet consisting mostly of fast food. She drinks no milk, preferring colas instead. How would this situation affect Julie's parathyroid hormone level?

Textbook Question

How would blocking the activity of phosphodiesterase (PDE) affect a cell that responds to hormonal stimulation by the cAMP second messenger system?

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Textbook Question

Roger has been extremely thirsty. He drinks numerous glasses of water every day and urinates a great deal. Name two disorders that could produce these signs and symptoms. What test could a clinician perform to determine which disorder Roger has?

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