Endocrine System Overview

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Questions and Answers

What hormone is secreted by β - cells?

Insulin (correct)

Glucagon

Testosterone

Estrogen

Which condition is caused by insufficient secretion of insulin?

Diabetes mellitus (correct)

Hypoglycemia

Hyperthyroidism

Goitre

What hormone is primarily secreted by Leydig cells?

Insulin

Testosterone (correct)

Estrogen

Progesterone

Which hormone is secreted by the pineal gland?

Melatonin (A) Signup and view all the answers

What role does thyrocalcitonin play in the body?

Lowers calcium levels in blood plasma (A) Signup and view all the answers

Which gland secretes both T3 and T4 hormones?

Thyroid gland (D) Signup and view all the answers

What characterizes hypothyroidism?

Goitre development (A), Low levels of iodine (B) Signup and view all the answers

What is the primary function of hormones in the body?

To regulate physiological processes (C) Signup and view all the answers

What is the primary function of releasing hormones from the hypothalamus?

Stimulate the release of hormones from the pituitary gland (B) Signup and view all the answers

Which statement correctly contrasts hormonal control with nervous control?

Hormonal control is not affected by previous experiences. (C) Signup and view all the answers

Which types of glands discharge their secretions directly into the blood?

Endocrine glands (C) Signup and view all the answers

What disease can result from hyposecretion of the adrenal cortex?

Addison's Disease (D) Signup and view all the answers

What role does aldosterone play in the body?

Maintains sodium and potassium levels in blood (A) Signup and view all the answers

Which type of cells in the pancreas are responsible for secreting glucagon?

Alpha cells (D) Signup and view all the answers

Which gland secretes catecholamines, including adrenaline?

Adrenal medulla (B) Signup and view all the answers

What characterizes the effects of hormones compared to nervous impulses?

Hormones can have long-lasting effects. (A) Signup and view all the answers

What condition is associated with low secretion of growth hormone?

Dwarfism (C) Signup and view all the answers

Which hormone is responsible for milk formation and the growth of the mammary glands?

Prolactin (B) Signup and view all the answers

The hormone responsible for the reabsorption of water from the kidneys is called?

Vasopressin (B) Signup and view all the answers

Which hormone induces ovulation from Graafian follicles?

Luteinizing hormone (A) Signup and view all the answers

What is the primary function of thymosins produced by the thymus gland?

Producing T-lymphocytes (A) Signup and view all the answers

Which of the following glands is involved in the secretion of hormones that regulate metabolism?

Thyroid gland (A) Signup and view all the answers

Hormones generally have which characteristic regarding their action?

They generally have a slower onset but longer-lasting effects. (D) Signup and view all the answers

What role does a feedback mechanism play in hormone regulation?

It regulates the action and levels of hormones. (C) Signup and view all the answers

Study Notes

Hormones

Hormones are chemical messengers that regulate physiological processes in living organisms.
Hormones act on specific target cells, tissues, and organs.

Endocrine Glands

Endocrine glands secrete hormones directly into the bloodstream.
Exocrine glands secrete substances into ducts.
- Examples of exocrine glands include salivary glands, sebaceous glands.
Major endocrine glands include pituitary, pineal, thyroid, adrenal, pancreas, parathyroid, thymus, and gonads.
Other organs, including the GI tract, liver, kidneys, and heart, also produce hormones.

Differences Between Hormonal and Nervous Control

Feature	Hormonal Control	Nervous Control
Transmission	Chemically through blood	Electro-chemically through nerve fibres
Speed	Slow	Rapid
Target	Different organs	Specific organs
Effects of previous experience	Not affected	Affected
Duration	Long-lasting and short-lasting	Short-lasting

Adrenal Glands

Divided into adrenal medulla and adrenal cortex.
Adrenal medulla secretes adrenaline (epinephrine) and noradrenaline (norepinephrine), which are called catecholamines (emergency hormones).
Adrenal cortex secretes corticoids, which include glucocorticoids (regulate carbohydrate metabolism, e.g., cortisol) and mineralocorticoids (regulate sodium and potassium levels, e.g., aldosterone).

Hyposecretion and Hypersecretion

Hyposecretion: Less secretion from an endocrine gland (e.g., Addison's Disease, insufficient insulin secretion leads to Diabetes Mellitus).
Hypersecretion: Increased secretion (e.g., Cushing's syndrome, over-secretion of insulin leads to hypoglycemia).

Pancreas

Islets of Langerhans contain alpha (α) and beta (β) cells.
Alpha cells secrete glucagon.
Beta cells secrete insulin.

Testis

Leydig cells secrete androgens (mainly testosterone).
Testosterone is involved in spermatogenesis and male secondary sexual characteristics.

Ovary

Secretes estrogen and progesterone.
Estrogen develops female secondary sexual characteristics.
Progesterone affects mammary glands and milk secretion.

Hypothalamus

Contains neurosecretory cells that produce releasing and inhibiting hormones.
These hormones regulate the synthesis and secretion of pituitary hormones.

Pineal Gland

Secretes melatonin which regulates the body's rhythm.

Thyroid Gland

Secretes tetraiodothyronine (thyroxine, T4) and triiodothyronine (T3).
Iodine deficiency can lead to hypothyroidism (goiter, cretinism, myxedema).
High iodine levels can lead to hyperthyroidism (increased metabolic rate).

Parathyroid Gland

Regulates calcium levels in the blood (increases reabsorption in renal tubules and digested food).

Pituitary Gland

Divided into adenohypophysis (anterior pituitary) and neurohypophysis (posterior pituitary).
Anterior pituitary: produces growth hormone, prolactin, thyroid stimulating hormone, adrenocorticotrophic hormone, gonadotrophic hormones (luteinizing hormone and follicle stimulating hormone), and melanocyte-stimulating hormone (MSH)
Posterior pituitary: produces oxytocin and vasopressin (antidiuretic hormone).

Other Hormones

Prolactin: Involved in mammary gland growth and milk production.
Thyroid-stimulating hormone: Stimulates thyroxine secretion.
Adrenocorticotropic hormone: Stimulates glucocorticoid secretion.
Gonadotrophic hormones: Regulate gonadal function.
Melanocyte-stimulating hormone assists in skin pigmentation.
Oxytocin helps in uterine contraction and milk ejection
Vasopressin or antidiuretic hormone helps reabsorb water by tubules
Hyperglycaemia: Increased blood glucose; involves glucagon and diabetes mellitus
Hypoglycemia: Reduced blood glucose; involves insulin

Characteristics of Hormones

Act as chemical messengers.
Secreted by living cells, tissues, or organs (glands).
Secreted in small quantities.
Act on specific target sites.
Generally slow but long-lasting effects.
Either accelerate or inhibit a reaction.

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Description

Explore the vital role of hormones in the endocrine system with this quiz. Learn about the differences between hormonal and nervous control, the functions of major endocrine glands, and the processes regulated by these chemical messengers. Perfect for students studying biology or healthcare.