Endocrine System

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Questions and Answers

What primarily drives smooth muscle contraction?

Sodium from outside the cell

Potassium from outside the cell

Calcium from outside the cell (correct)

Chloride from outside the cell

Which muscle type undergoes phasic contraction (contracts and relaxes continuously)?

Type 2B fast twitch glycolytic fatigable fibers

Type 1 slow twitch oxidative fibers

Cardiac muscle

Smooth muscle (correct)

What type of muscle has a 'Pacemaker Potential'?

Smooth muscle

Type 2A fast twitch oxidative glycolytic fatigue resistant fibers

Type 2B fast twitch glycolytic fatigable fibers

Cardiac muscle (correct)

Which muscle type has t-tubules and gap junctions?

Cardiac muscle Signup and view all the answers

What is the primary mechanism for activation of cardiac muscle?

Action potential propagation along tubule Signup and view all the answers

Which muscle type is similar to smooth muscle in being involuntary?

Cardiac muscle Signup and view all the answers

What type of muscle contraction primarily relies on calcium from outside the cell?

Smooth muscle Signup and view all the answers

Which type of muscle has the fastest contracting fibers in skeletal muscle?

Type 2B fast twitch glycolytic fatigable fibers Signup and view all the answers

Which type of chemical messengers are secreted by the nervous system?

Amines Signup and view all the answers

What is the approximate time frame for hormones to produce their effects?

Within a few seconds to several hours Signup and view all the answers

How are hormones transported to most body cells?

Through the blood stream Signup and view all the answers

What is the main categorization of hormones based on the location of their target sites?

Endocrine Signup and view all the answers

How do hormones exert targeted responses?

Cells have specific receptors Signup and view all the answers

What determines the ability of cells to respond to hormones?

Expression of specific receptors by the target cells Signup and view all the answers

Where are steroid receptors located?

Cytosolic / nuclear Signup and view all the answers

What is the role of the hypothalamus in the neuroendocrine system?

Secretion of regulatory hormones Signup and view all the answers

Which stimuli can cause hormone release?

Action potentials Signup and view all the answers

What does the anterior pituitary gland secrete in response to hypothalamic hormones?

Thyroid-stimulating hormone (TSH) Signup and view all the answers

What hormones are formed in the hypothalamus and released from the posterior pituitary?

ADH and Oxytocin Signup and view all the answers

What is the main control mechanism provided by the hypothalamus and pituitary in relation to the adrenal gland?

Sympathetic output to the adrenal medulla Signup and view all the answers

What can cause hypocalcemia?

Vitamin D deficiency Signup and view all the answers

What is the composition of human bone?

70% hydroxyapatite and 30% osteoid Signup and view all the answers

Which hormone promotes bone growth in the epiphyseal plate?

Growth hormone and sex steroids Signup and view all the answers

What is the primary function of trabecular bone?

Blood cell formation Signup and view all the answers

What is the role of osteoclasts in bone physiology?

Bone resorption Signup and view all the answers

What can lead to severe hypercalcemia?

Parathyroid tumors Signup and view all the answers

Which substance is responsible for demineralization of bone in severe hypercalcemia?

Calcium Signup and view all the answers

What is the primary function of flat bones in the human body?

Protection Signup and view all the answers

What does the epiphyseal line represent in bone structure?

A remnant of the epiphyseal plate Signup and view all the answers

What is the primary function of yellow bone marrow?

Contains fat cells Signup and view all the answers

What is the primary cause of osteoporosis?

Faster reabsorption of bone than its reformation Signup and view all the answers

Which cells replace chondrocytes and calcify the new bone matrix in bone growth?

Osteoblasts Signup and view all the answers

What is the role of thyroid hormones T3 and T4?

Regulating metabolic rate, heat production, and energy release through oxidation of food molecules Signup and view all the answers

What is the iodine requirement for thyroid hormone synthesis?

100-250 μg/day Signup and view all the answers

Which hormones are released during the stress response through the Hypothalamus-Pituitary-Adrenal (HPA) axis?

Adrenaline and cortisol Signup and view all the answers

What are the short-term biological stress responses?

Increased blood pressure, breathing rate, and metabolic rate Signup and view all the answers

How are T3 and T4 stored in the thyroid gland?

Stored in colloid and circulating bound to thyroxine binding protein Signup and view all the answers

What is the main function of T3 in cells?

Binding to high affinity T3 receptors on DNA to regulate mRNA and protein synthesis Signup and view all the answers

What are the effects of hyperthyroidism?

Increased heart rate, ventilation, and vascularization Signup and view all the answers

How do thyroid hormones maintain their effects in plasma?

T4 and T3 circulate bound to thyroxine binding protein Signup and view all the answers

Which hormone is formed from skin cholesterol and dietary vitamin D, and plays a vital role in calcium absorption and bone formation?

1,25-dihydroxyvitamin D3 Signup and view all the answers

What can lack of T3 & T4 due to dietary iodine deficiency cause in children?

Irreversible brain damage Signup and view all the answers

What did Walter Cannon coin the term for in 1915?

Fight or Flight Response Signup and view all the answers

Which hormone regulates net dietary calcium absorption, and is formed from skin cholesterol and dietary vitamin D?

1,25-dihydroxyvitamin D3 Signup and view all the answers

What is the main role of the thyroid gland?

Regulating metabolism through thyroid hormone production Signup and view all the answers

What is the role of T3 in gene expression?

Releasing corepressors from thyroid hormone receptors and assisting in gene activation Signup and view all the answers

What can low blood calcium levels, or hypocalcaemia, potentially cause?

Convulsions and numbness Signup and view all the answers

Which hormone is involved in regulating blood calcium levels and plays a role in bone formation and growth?

Calcitonin Signup and view all the answers

What is the consequence of hypothyroidism?

Decreased heart rate, ventilation, and vascularization Signup and view all the answers

What can hypercalcaemia, or high blood calcium, lead to?

Kidney stones and abnormal heart rhythms Signup and view all the answers

Which hormone is involved in regulating blood calcium levels and promotes calcium reabsorption from the kidneys and calcium release from the bones?

Parathyroid hormone (PTH) Signup and view all the answers

What is the daily calcium requirement for adults?

1g per day Signup and view all the answers

What can hypocalcaemia combined with vitamin D deficiency cause in adults?

Osteomalacia Signup and view all the answers

Which hormone is released by the thyroid gland, requires iodine for production, and increases metabolic rate?

T3 and T4 hormones Signup and view all the answers

What can lack of T3 & T4 due to dietary iodine deficiency cause in adults?

Impaired brain function Signup and view all the answers

Which hormone is involved in regulating blood calcium levels and inhibits calcium release from the bones?

Calcitonin Signup and view all the answers

What is the primary difference in the initiation of muscle contraction between smooth muscle and skeletal muscle?

Smooth muscle relies on calcium from outside the cell, while skeletal muscle uses calcium and sodium Signup and view all the answers

Which type of muscle has the 'Pacemaker Potential'?

Cardiac muscle Signup and view all the answers

What is the main mechanism for activation of cardiac muscle?

Action potential propagated along tubule, Ca influx, Ryanodine receptor activation Signup and view all the answers

What is the primary similarity between cardiac muscle and smooth muscle?

Both are involuntary Signup and view all the answers

Which type of muscle contraction primarily relies on calcium from outside the cell?

Smooth muscle Signup and view all the answers

What is the primary function of yellow bone marrow?

Fat storage and blood cell formation Signup and view all the answers

What is the approximate time frame for hormones to produce their effects?

Minutes to hours Signup and view all the answers

What does the epiphyseal line represent in bone structure?

The site of longitudinal bone growth Signup and view all the answers

Which type of receptors do lipid-soluble hormones primarily bind to?

Cytosolic/nuclear receptors Signup and view all the answers

Which of the following is a mechanism of hormone distribution to target cells?

Diffusion or via blood Signup and view all the answers

What is the primary role of the hypothalamus in the neuroendocrine system?

Secretion of regulatory hormones Signup and view all the answers

Which of the following hormones is released from the posterior pituitary gland?

ADH Signup and view all the answers

What is the primary mechanism for activation of cardiac muscle?

Action potentials Signup and view all the answers

Which of the following hormones is involved in the sympathetic output to the adrenal medulla?

Adrenalin Signup and view all the answers

What drives smooth muscle contraction?

Calcium from outside the cell Signup and view all the answers

Which type of muscle undergoes phasic contraction?

Cardiac muscle Signup and view all the answers

What is the approximate time frame for hormones to produce their effects?

Seconds to hours Signup and view all the answers

What is the consequence of hypothyroidism?

Reduced metabolic rate Signup and view all the answers

Which of the following is a category of organic chemical messengers?

Amines Signup and view all the answers

What is the primary mechanism of control provided by the hypothalamus and pituitary in relation to the adrenal gland?

Control of cortisol release Signup and view all the answers

What is the iodine requirement for thyroid hormone synthesis?

100-250 μg/day Signup and view all the answers

Where are T3 and T4 stored?

In colloid Signup and view all the answers

What is the main role of T3 in cells?

Regulating gene expression Signup and view all the answers

What is the consequence of hypothyroidism?

Decreased metabolic rate Signup and view all the answers

How do T3 and T4 circulate in the blood?

Bound to thyroxine binding protein Signup and view all the answers

What is the primary role of the thyroid gland?

Regulating metabolic rate Signup and view all the answers

What is the primary function of T4 and T3 in cells?

Regulating metabolic rate Signup and view all the answers

What are the effects of hyperthyroidism?

Increased heart rate Signup and view all the answers

What is the role of T3 in gene expression?

Regulates mRNA and protein synthesis Signup and view all the answers

What primarily drives smooth muscle contraction?

Calcium influx from outside the cell Signup and view all the answers

What is the consequence of hypothyroidism on heart rate?

Decreased heart rate Signup and view all the answers

What is the main source of iodine for thyroid hormone production?

Dietary intake Signup and view all the answers

Which hormone is primarily responsible for regulating blood calcium levels and promoting calcium reabsorption from the kidneys and calcium release from the bones?

Parathyroid hormone (PTH) Signup and view all the answers

What is the primary source of 1,25-dihydroxyvitamin D3, which plays a vital role in calcium absorption and bone formation?

Skin cholesterol and dietary vitamin D Signup and view all the answers

What can low blood calcium levels, or hypocalcaemia, potentially cause?

Convulsions and numbness Signup and view all the answers

What can hypercalcaemia, or high blood calcium, potentially lead to?

Kidney stones and abnormal heart rhythms Signup and view all the answers

What is the primary function of calcitonin in relation to blood calcium levels?

Inhibits osteoclast activity and promotes calcium deposition in bones Signup and view all the answers

What can lack of T3 & T4 due to dietary iodine deficiency cause in children?

Impaired brain development and hearing loss Signup and view all the answers

What is the approximate daily calcium requirement for adults?

1g per day Signup and view all the answers

What is the main role of the thyroid hormones T3 and T4?

Promoting bone growth and development Signup and view all the answers

What can hypocalcaemia combined with vitamin D deficiency cause in adults?

Osteomalacia Signup and view all the answers

What is the primary cause of rickets in children?

Vitamin D deficiency Signup and view all the answers

What are the potential consequences of myxoedema (postnatal hypothyroidism) in adults?

Impaired brain function Signup and view all the answers

What is the primary function of 1,25-dihydroxyvitamin D3 in the body?

Aiding calcium absorption and bone formation Signup and view all the answers

Which of the following can lead to severe hypercalcemia?

Malignancy Signup and view all the answers

What is the primary cause of hypocalcemia?

Vitamin D deficiency Signup and view all the answers

Which hormone plays a role in regulating blood calcium levels and inhibits calcium release from the bones?

Parathyroid hormone (PTH) Signup and view all the answers

What is the primary composition of bone?

70% hydroxyapatite and 30% osteoid Signup and view all the answers

What is the primary function of bone marrow?

Produce red and white blood cells Signup and view all the answers

What type of bones include vertebrae and ribs?

Irregular bones Signup and view all the answers

Which cells replace chondrocytes and calcify the new bone matrix in bone growth?

Osteoblasts Signup and view all the answers

What primarily drives smooth muscle contraction?

Calcium from outside the cell Signup and view all the answers

What is the primary function of yellow bone marrow?

Store excess fat Signup and view all the answers

Which hormone promotes bone growth in the epiphyseal plate?

Growth hormone Signup and view all the answers

What does osteoporosis involve?

Faster reabsorption of bone than its reformation Signup and view all the answers

What are the symptoms of severe hypercalcemia?

Abdominal pain, nausea, vomiting Signup and view all the answers

Study Notes

Thyroid Hormones and Calcium Regulation

Thyroid gland releases T3 and T4 hormones, requiring iodine for production, which increases metabolic rate and has various other effects on growth and development.
Lack of T3 & T4 due to dietary iodine deficiency can cause irreversible brain damage in children and impaired brain function in adults.
Myxoedema (postnatal hypothyroidism) and Grave’s disease (hyperthyroidism) are thyroid hormone disorders with distinct symptoms and causes.
Thyroid hormone deficiency can lead to impaired brain development, hearing loss, muscle rigidity, and mood changes in children.
Daily calcium requirements are about 1g per day, but net dietary calcium absorption is only about 150 mg/day, regulated by three hormones: 1,25-dIhydroxyvitamin D3, parathyroid hormone (PTH), and calcitonin.
1,25-dihydroxyvitamin D3 is formed from skin cholesterol and dietary vitamin D, and plays a vital role in calcium absorption and bone formation.
Vitamin D is mainly formed in the skin during U-V light exposure and is crucial for calcium absorption in the body.
Low blood calcium levels, or hypocalcaemia, can be caused by dietary calcium and vitamin D deficiency, low UV-light exposure, or hypoparathyroidism, resulting in potential severe effects like convulsions and numbness.
Hypocalcaemia combined with vitamin D deficiency can cause rickets in children and osteomalacia in adults.
Hypercalcaemia, or high blood calcium, can be caused by excessive absorption of dietary calcium, and can lead to symptoms like kidney stones and abnormal heart rhythms.
The regulation of blood calcium levels is crucial for many cellular functions, including neurotransmitter and hormone secretion, and muscle contraction.
Calcium plays a vital role in bone formation and growth, with its concentration in the blood being regulated by vitamin D, PTH, and calcitonin.

Human Skeletal System and Bone Structure

Hypercalcemia (calcium > 2.6 mmol/L) can be caused by parathyroid tumors, malignancy, large doses of Vitamin D, and extra-renal synthesis of 1,25-dihydroxyvitamin D3.
Severe hypercalcemia can lead to abdominal pain, nausea, vomiting, demineralization of bone, calcification of soft tissues and blood vessels, kidney stones, increased blood pressure, anxiety, confusion, weakness, and coma.
Treatment of hypercalcemia depends on its cause and involves regulating blood concentration of calcium through Vitamin D, PTH, and Calcitonin.
Hypocalcemia is usually due to Vitamin D deficiency and can lead to convulsions, arrhythmia, tetany, and numbness, and poor bone formation.
The human skeleton contains 10-12 kg of bone, 1-2 kg of calcium, and 0.5-0.75 kg of phosphorus, with 70% of bone being hydroxyapatite and 30% being osteoid.
Bone serves as mineral storage, support, protection, movement, and blood cell formation.
Different types of bones include long, short, flat, irregular, and sesamoid bones.
Bones consist of cartilage, epiphysis/metaphysis, epiphyseal line, trabecular and cortical bone, and bone marrow producing red and white blood cells.
Bone cell types include osteogenic, osteoblasts, osteocytes, and osteoclasts.
Bone growth in the epiphyseal plate is promoted by growth hormone and sex steroids, with osteoblasts replacing chondrocytes and calcifying the new bone matrix.
Osteoporosis involves faster reabsorption of bone than its reformation, leading to bone thinning and greater fracture risks, especially in trabecular bone.
Bone marrow contains stem cells, produces osteoprogenitors, and red bone marrow produces red and white blood cells, while yellow bone marrow contains fat cells.

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Description

Test your knowledge of thyroid hormones and calcium regulation with this quiz. Explore the effects of T3 and T4 hormones on growth and development, as well as their role in conditions like myxoedema and Grave’s disease. Delve into the importance of calcium in the body, its absorption regulation by hormones like 1,25-dIhydroxyvitamin D3 and PTH, and the potential consequences of calcium deficiency or excess.