Regulation of blood sugar Flashcards
What is the main issue in diabetes mellitus?
In diabetes mellitus, insulin activity is deficient or absent, leading to high blood glucose levels. However, glucose cannot enter most cells, causing the body to be unable to utilize glucose for energy, resulting in a “starving in the land of plenty” scenario.
How does the body respond to the absence of insulin in diabetes mellitus?
The body mobilizes fats for energy.
What happens to free fatty acids (FFAs) in the absence of insulin?
FFAs cannot make glucose or enter the Krebs cycle due to a lack of oxaloacetate, leading to ketone body buildup and ketoacidosis, which can disrupt CNS activity, heart function, and oxygen transport, potentially causing coma and death.
What are the three key signs of diabetes mellitus?
The three key signs are:
1. Polyuria: Excess glucose in urine inhibits water resorption, causing dehydration and electrolyte imbalance.
2. Polydipsia: Dehydration stimulates thirst centers in the hypothalamus.
3. Polyphagia: Excessive hunger due to the body’s inability to use ingested carbohydrates for energy.
What is Type 1 Diabetes (Juvenile Diabetes)?
Type 1 Diabetes is less common and is caused by the loss of beta cells, resulting in no insulin production. It may be due to an autoimmune reaction or viral-induced destruction of beta cells. Insulin is required for survival, and it can lead to vascular and neurological complications.
What is Type 2 Diabetes (Adult-Onset Diabetes)?
Type 2 Diabetes is more common and involves a reduction in insulin secretion and/or decreased sensitivity of target cells. It is linked to age, lifestyle, and genetics. Insulin is often produced, but target cells may have receptor defects. It can be managed by diet, weight loss, and exercise but may eventually require insulin.
What is the risk of ketoacidosis in Type 2 Diabetes?
Ketoacidosis is typically not a major concern in Type 2 Diabetes, but individuals are at risk for complications like heart disease and impaired circulation, similar to Type 1.
What are the primary metabolic functions of the liver?
The liver conducts over 500 metabolic functions, including regulating plasma cholesterol levels and processing nearly every class of nutrient.
What is the liver’s role in carbohydrate metabolism?
The liver is involved in isomerizing monosaccharides to glucose, storing glucose as glycogen and fat, and performing glycogenolysis and gluconeogenesis to release or create glucose when needed.
How does the liver contribute to fat metabolism?
The liver is the primary site for beta-oxidation, generating ketone bodies from Acetyl-CoA. It also synthesizes lipoproteins for triglyceride transport and metabolizes cholesterol and bile salts.
What is the liver’s role in protein metabolism?
The liver is the principal site for amino acid deamination, forms urea to remove ammonia, generates most plasma proteins, and produces non-essential amino acids via transamination.
What does the liver store?
The liver stores vitamins (A, D, and B12), iron (as ferritin), and has a reserve supply for up to 1-2 years for some vitamins and months for iron.
What is biotransformation in the liver?
Biotransformation in the liver involves inactivating compounds like ethanol and drugs, activating certain drugs, processing bilirubin from heme, and catabolizing hormones for excretion.
Why can’t triglycerides and cholesterol circulate freely in the blood?
Triglycerides and cholesterol are insoluble in water and are transported as lipoproteins in the bloodstream.
What are the components of lipoproteins?
Lipoproteins are composed of varying proportions of triglycerides, phospholipids, cholesterol, and proteins, which help regulate entry into specific target cells.
What are chylomicrons and their role?
Chylomicrons are the lowest-density lipoproteins and transport newly absorbed lipids from the GI tract to other parts of the body.
What is the role of VLDL (Very Low-Density Lipoprotein)?
VLDL is primarily made in the liver and transports triglycerides to peripheral tissues, especially adipose tissue. VLDLs become LDL after triglyceride unloading at target cells.
What is the function of HDL (High-Density Lipoprotein)?
HDL’s primary function is to transport excess cholesterol from peripheral tissues to the liver for degradation, or to tissues like ovaries and adrenals for steroid hormone synthesis.
What is the primary role of LDL (Low-Density Lipoprotein)?
LDL’s primary role is to deliver cholesterol to peripheral tissues, where cholesterol is essential for functions like steroid hormone synthesis, bile salts, and cell membranes.
Why are HDL considered “good” and LDL “bad”?
HDL is considered “good” because it helps remove excess cholesterol, while LDL is considered “bad” because excessive LDL can deposit cholesterol in blood vessel walls, increasing the risk of atherosclerosis.
What are the two main thyroid hormones and their functions?
- Thyroxine (T4) – The primary secretory product, containing 4 iodine molecules.
- Triiodothyronine (T3) – More active than T4, derived from T4 at target cells, influencing metabolism more strongly.
Where is the thyroid gland located and what is its function?
The thyroid is a butterfly-shaped gland located on the trachea, just below the larynx. It produces thyroid hormones that regulate metabolism, growth, and development.
How do saturated and unsaturated fatty acids influence cholesterol levels?
Saturated fatty acids stimulate liver cholesterol synthesis and inhibit excretion, while unsaturated fatty acids promote cholesterol catabolism and excretion. Trans fats increase LDL and decrease HDL.
How is thyroid hormone transported and activated in target cells?
T4 and T3 are transported in the blood bound to thyroxine-binding globulin (TBG). At target cells, T4 is converted to the more active T3, which binds to thyroid hormone receptors in the nucleus, increasing gene expression.
What functions does thyroid hormone (TH) regulate in the body?
TH regulates basal metabolic rate, body heat production, blood pressure, and tissue growth and development, particularly in the nervous and skeletal systems.
What regulates the secretion of thyroid hormones?
Falling thyroid hormone levels trigger the release of TSH from the anterior pituitary, which stimulates the thyroid gland to release stored thyroid hormones. This process is regulated by negative feedback, where high thyroid hormone levels inhibit TSH and TRH secretion.
What is hypothyroidism and what are its symptoms?
Hypothyroidism is a condition caused by low thyroid hormone levels, leading to symptoms like lethargy, low metabolic rate, cold sensitivity, dry skin, and edema. In severe cases, it can cause myxedema and goiter.
What is hyperthyroidism and its common cause?
Hyperthyroidism is characterized by an overactive thyroid, often caused by Grave’s disease, an autoimmune disorder where antibodies stimulate the thyroid to overproduce hormones. Symptoms include elevated BMR, sweating, rapid heartbeat, and exophthalmos.
What is congenital hypothyroidism and its effects?
Congenital hypothyroidism occurs in infants due to insufficient thyroid hormone for CNS development, leading to mental retardation, thick tongue/neck, and disproportionate body size. Early diagnosis and treatment can prevent irreversible damage.
What is calcitonin and its function?
Calcitonin is a hormone produced by parafollicular cells of the thyroid that lowers blood calcium by inhibiting bone resorption and stimulating calcium uptake into bones. It is most important during childhood for skeletal growth.
