80 Questions
What happens to glucose in muscle cells after it is transported inside?
It is immediately phosphorylated and becomes a substrate for carbohydrate metabolic functions.
What is the primary source of energy for muscle tissue during most of the day?
Fatty acids
What is the effect of insulin on the cell membrane of muscle cells?
It increases the permeability of the cell membrane to glucose and other substances.
What is the main purpose of this chapter?
To discuss the physiological roles of insulin and glucagon
What happens to the vesicles that carry glucose transport proteins when insulin is no longer available?
They separate from the cell membrane and move back to the cell interior to be used again.
What is the effect of insulin on the uptake of amino acids and ions in muscle cells?
It increases the uptake of amino acids and ions.
What is the approximate diameter of an islet of Langerhans?
0.3 millimeter
What is the primary function of the acini in the pancreas?
To secrete digestive juices into the duodenum
Why is insulin necessary for glucose uptake in muscle cells?
Because muscle cells are only slightly permeable to glucose without insulin.
What is the result of prolonged, untreated diabetes on protein metabolism?
Decreased synthesis of proteins
What is the effect of insulin on intracellular metabolic enzymes?
It increases the activity of metabolic enzymes.
What is the approximate number of islets of Langerhans in the human pancreas?
1 to 2 million
What happens to glucose uptake in muscle cells during two specific conditions?
It increases during exercise and high-glucose meals.
What is the primary function of insulin in the body?
To regulate all of the above
What is the name of the cells that secrete insulin and glucagon in the pancreas?
All of the above
What is the term for the condition caused by abnormalities of fat metabolism in patients with diabetes mellitus?
Acidosis
What is the primary function of glucagon in the body?
To increase blood glucose concentration
What is the first step in the cascade of events triggered by glucagon in the liver?
Activation of adenylyl cyclase
What is the byproduct of glycogen degradation triggered by glucagon?
Glucose-1-phosphate
What is the effect of increased blood glucose concentration on glucagon secretion?
It decreases glucagon secretion
What is the opposite effect of glucose on insulin and glucagon secretion?
Glucose increases insulin secretion and decreases glucagon secretion
What is the approximate blood glucose level at which glucagon secretion is stimulated?
60 mg/100 ml of blood
What is the end result of the cascade of events triggered by glucagon in the liver?
Release of glucose from liver cells
What is the primary factor controlling glucagon secretion?
Blood glucose concentration
What is the consequence of severe and prolonged insulin resistance?
Pancreatic beta cell exhaustion
What happens to the pancreas in some obese people with marked insulin resistance?
It produces enough insulin to prevent severe abnormalities of glucose metabolism
What is the primary goal of lifestyle modifications in treating type 2 diabetes?
Increasing physical activity and caloric restriction
What is the role of thiazolidinediones in treating type 2 diabetes?
Increasing insulin sensitivity
What is the consequence of moderate hyperglycemia in the early stages of type 2 diabetes?
No significant abnormalities of glucose metabolism
What is the treatment approach in the later stages of type 2 diabetes?
Combination of lifestyle modifications and insulin administration
What is the effect of insulin resistance on glucose metabolism?
Impaired glucose regulation
What is the role of sulfonylureas in treating type 2 diabetes?
Causing additional release of insulin by the pancreas
What is the approximate percentage decrease in blood calcium concentration that can lead to tetany?
35%
What is the effect of hypocalcemia on the heart in laboratory animals?
Marked dilation of the heart
What is the effect of hypercalcemia on the nervous system?
Depression of nervous system activity
What is the approximate blood calcium level above which calcium phosphate crystals are likely to precipitate throughout the body?
17 mg/dl
What is the normal rate of calcium intake in the diet?
1000 mg/day
What percentage of ingested calcium is usually absorbed from the intestines?
35%
What is the effect of hypercalcemia on the gastrointestinal tract?
Decreased contractility of the muscle walls
What is the term for the muscle spasms that occur in the hands and feet due to hypocalcemia?
Carpopedal spasm
What is the primary effect of insulin on glucose uptake in liver cells?
Increase the activity of glucokinase
What happens to glycogen in the liver when blood glucose levels fall between meals?
It is broken down into glucose phosphate
What is the role of glucose phosphatase in the liver?
To remove the phosphate group from glucose phosphate
What is the net effect of insulin on glycogen synthesis in the liver?
It increases glycogen synthesis
What is the result of decreased insulin secretion by the pancreas?
Increased glucose release from the liver
What is the maximum percentage of liver mass that can be composed of glycogen?
5-6%
What is the enzyme responsible for phosphorylating glucose in the liver?
Glucokinase
What is the primary function of the liver in regulating blood glucose levels?
All of the above
What happens to the storage of fatty acids in the liver when insulin is not available?
It is almost blocked
What is the primary energy substrate used by essentially all tissues of the body in the absence of insulin, except the brain?
Free fatty acids
What is the effect of insulin deficiency on the enzyme hormone-sensitive lipase in fat cells?
It is strongly activated
What is the consequence of insulin deficiency on the plasma concentration of free fatty acids?
It increases rapidly
What is the effect of insulin deficiency on the use of fat for energy?
It is enhanced
What happens to the availability of precursors required for gluconeogenesis in the absence of insulin?
It decreases significantly
What is the effect of insulin deficiency on the concentration of acetoacetic acid in the blood?
It increases rapidly
What is the consequence of removing the pancreas on the concentration of blood glucose and free fatty acids?
Blood glucose and free fatty acids both increase
What is the effect of prolonged secretion of glucagon, growth hormone, cortisol, and progesterone?
Exhaustion of the beta cells of the islets of Langerhans
What is the role of parasympathetic nerves in the pancreas?
Increase insulin secretion during hyperglycemic conditions
What is the primary signal that controls the switching mechanism between carbohydrate and lipid metabolism?
Blood glucose concentration
What is the effect of insulin on lipid metabolism?
Increase glucose utilization and depress lipid metabolism
What is the effect of lack of insulin on glucose utilization?
Fat utilization mainly to the exclusion of glucose utilization
What is the role of glucagon in the body?
Increases glucose concentration in the blood
What is the effect of sympathetic nerve stimulation on the pancreas?
Decrease insulin secretion and increase glucagon secretion
What is the role of specialized neurons in the hypothalamus and brain stem?
Detect glucose concentration in the blood
What is the primary mechanism by which excessive glucose in the urine causes dehydration?
Osmotic diuresis
What is the critical pH level below which acidotic coma and death can occur within hours?
7.0
What is the consequence of excess fat utilization in the liver over a long time?
Severe arteriosclerosis and vascular lesions
What is the effect of untreated diabetes mellitus on protein metabolism?
Increased protein utilization
What is the primary cause of polyuria in diabetes?
Osmotic diuresis
What is the effect of severe diabetic acidosis on blood electrolytes?
Variable changes in blood electrolytes
What is the consequence of polyphagia in a person with severe untreated diabetes mellitus?
Rapid weight loss
What is the effect of dehydration on intracellular and extracellular fluids?
Both intracellular and extracellular dehydration
What is the primary function of the HbA1c test?
To assess average blood glucose concentrations for the previous three months
What is the normal range of blood glucose levels in a healthy individual after ingesting 1 gram of glucose per kilogram of body weight?
120-140 mg/100 ml
What is the significance of the glucose tolerance curve in diabetes?
It shows a slow rise and fall of blood glucose levels
What is the purpose of measuring hemoglobin A1c (HbA1c)?
To monitor glycemic control in people with diabetes
What happens to the glucose level in a person with diabetes after ingesting glucose?
It rises slowly and remains elevated for 4-6 hours
What is the significance of the lifespan of red blood cells in relation to HbA1c?
It indicates the duration of hyperglycemia
What is the difference between the glucose tolerance curve in a normal person and a person with diabetes?
The curve is slower in a person with diabetes
What is the role of the HbA1c test in diagnosing diabetes mellitus?
It is used in conjunction with other tests
This chapter discusses the physiological roles of insulin and glucagon, and the pathophysiology of diseases, especially diabetes. Learn about the pancreas' secretions and their impact on glucose, lipid, and protein metabolism.
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