Textbook Question
In what ways can a hormone modify the activities of its target cells?
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Ch. 18 The Endocrine System
Martini, Nath, Bartholomew12th EditionFundamentals of Anatomy and PhysiologyISBN: 9780137854011
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Table of contents
- Ch. 1 An Introduction to Anatomy and Physiology25
- Ch. 2 The Chemical Level of Organization34
- Ch. 3 The Cellular Level of Organization29
- Ch. 4 The Tissue Level of Organization24
- Ch. 5 The Integumentary System17
- Ch. 6 Bones and Bone Structure33
- Ch. 7 The Axial Skeleton11
- Ch. 8 The Appendicular Skeleton17
- Ch. 9 Joints13
- Ch. 10 Muscle Tissue12
- Ch. 11 The Muscular System28
- Ch. 12 Nervous Tissue18
- Ch. 13 The Spinal Cord, Spinal Nerves, and Spinal Reflexes22
- Ch. 14 The Brain and Cranial Nerves20
- Ch. 15 Sensory Pathways and the Somatic Nervous System17
- Ch. 16 The Autonomic Nervous System and Higher-Order Functions30
- Ch. 17 The Special Senses15
- Ch. 18 The Endocrine System21
- Ch. 19 Blood31
- Ch. 20 The Heart31
- Ch. 21 Blood Vessels and Circulation26
- Ch. 22 The Lymphatic System and Immunity25
- Ch. 23 The Respiratory System4
- Ch. 24 The Digestive System18
- Ch. 26 The Urinary System31
- Ch. 27 Fluids & Electrolytes30
- Ch. 28 The Reproductive System12
- Ch. 29 Development and Inheritance17
Martini, Nath, Bartholomew12th EditionFundamentals of Anatomy and PhysiologyISBN: 9780137854011Not the one you use?Change textbook
Chapter 18, Problem 23
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
Verified step by step guidance1
Step 1: Understand the role of blood calcium levels in the body. Calcium is crucial for many physiological processes, including bone metabolism, nerve function, and muscle contraction. The body tightly regulates blood calcium levels through hormones and cellular activity.
Step 2: Recall the hormones involved in calcium regulation: Parathyroid hormone (PTH) and calcitonin. PTH is secreted when blood calcium levels are low to increase calcium levels, while calcitonin is secreted when calcium levels are high to lower them.
Step 3: Analyze the effects of decreased blood calcium. When calcium levels drop, the body responds by increasing PTH secretion to raise calcium levels. This involves increasing osteoclast activity to release calcium from bones, reducing calcium elimination by the kidneys, and increasing calcium absorption in the intestines.
Step 4: Evaluate each option in the context of decreased blood calcium: (a) Calcitonin secretion would decrease, not increase, because it lowers calcium. (b) PTH secretion would increase to raise calcium levels. (c) Calcium elimination by kidneys would decrease to conserve calcium. (d) Osteoclast activity would increase to release calcium from bones. (e) Excitability of neural membranes increases with low calcium, as calcium stabilizes neural membranes.
Step 5: Summarize the physiological responses to decreased blood calcium: increased PTH secretion, increased osteoclast activity, decreased calcium elimination by kidneys, and increased neural excitability. Calcitonin secretion decreases in this scenario.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Parathyroid Hormone (PTH) Secretion
PTH is secreted by the parathyroid glands in response to low blood calcium levels. It acts to increase calcium concentration by stimulating bone resorption, enhancing calcium reabsorption in the kidneys, and promoting activation of vitamin D to increase intestinal calcium absorption.
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Review of Major Hormones
Calcitonin Function
Calcitonin is a hormone produced by the thyroid gland that lowers blood calcium levels by inhibiting osteoclast activity and promoting calcium deposition in bones. Its secretion increases when blood calcium is high, thus it decreases when calcium levels are low.
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Osteoclast Activity and Calcium Homeostasis
Osteoclasts are bone cells that break down bone tissue, releasing calcium into the bloodstream. Increased osteoclast activity raises blood calcium levels, which is typically stimulated by PTH during hypocalcemia to restore calcium balance.
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Related Practice
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
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
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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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