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How does the endocrine system maintain homeostasis, and how does it differ from the nervous system?
The endocrine system maintains homeostasis by releasing hormones that have prolonged effects. Unlike the nervous system, which works faster but has short-lived effects, the endocrine system has slower but longer-lasting effects.
What is the primary function of hormones, and how do they target specific structures?
Hormones are chemical messages produced by glands that target specific structures such as muscles, glands, and cells to regulate body functions.
Describe the difference between exocrine and endocrine glands.
Exocrine glands secrete products into ducts or outside the body (e.g., sweat glands), while endocrine glands are ductless and release hormones directly into the bloodstream.
What are non-target and target hormones? Provide examples.
Non-target hormones affect many cells or tissues (e.g., insulin). Target hormones act on specific sites (e.g., oxytocin).
Explain the difference between tropic and non-tropic hormones, with examples.
Tropic hormones stimulate other endocrine glands (e.g., TSH), while non-tropic hormones act directly on target tissues (e.g., insulin).
What are antagonistic hormones, and can you provide an example?
Antagonistic hormones work in opposition to each other. Example: Insulin lowers blood glucose, while glucagon raises it.
What is the role of positive feedback in hormone regulation? Provide an example.
Positive feedback amplifies a process, reinforcing the production of more of the hormone. Example: Oxytocin during childbirth causes more uterine contractions, which in turn cause more oxytocin release.
How does negative feedback help regulate hormone levels? Provide an example.
Negative feedback inhibits further production of a hormone to maintain stability. Example: High thyroxine levels reduce TRH production from the hypothalamus, lowering TSH and thyroxine levels.
What is the function of the hypothalamus in the endocrine system?
The hypothalamus connects the nervous and endocrine systems, controlling functions like temperature, hunger, and sleep. It produces oxytocin and ADH, which are stored in the pituitary gland, and stimulates the pituitary via releasing hormones.
What are the six hormones produced by the anterior pituitary, and what are their functions?
1. FSH: Stimulates ovarian follicle growth and estrogen secretion.
2. LH: Triggers ovulation and testosterone production.
3. ACTH: Stimulates adrenal cortex to release cortisol.
4. TSH: Stimulates thyroid hormone production.
5. Prolactin: Stimulates milk production.
6. GH: Promotes bone and tissue growth.
What two hormones are released by the posterior pituitary, and what do they regulate?
1. Oxytocin: Initiates uterine contractions during childbirth.
2. ADH: Increases water reabsorption in the kidneys.
What are common disorders of the pituitary gland related to growth hormone (GH)?
1. Dwarfism: Caused by GH deficiency during childhood.
2. Gigantism: Caused by excess GH during childhood.
3. Acromegaly: Caused by excess GH in adulthood, affecting the hands, feet, and face.
What hormones are produced by the thyroid gland, and what are their functions?
1. Thyroxine (T4): Regulates metabolism, growth, and development.
2. Calcitonin: Lowers blood calcium by promoting calcium deposition in bones.
What are the consequences of thyroid disorders such as hypothyroidism and hyperthyroidism?
1. Hypothyroidism: Insufficient thyroxine production, leading to conditions like cretinism (in children) and myxedema (in adults).
2. Hyperthyroidism: Excessive thyroxine production, causing symptoms like anxiety and weight loss.
3. Goiter: Enlargement of the thyroid due to iodine deficiency or thyroid dysfunction.
What is the role of the parathyroid glands, and what disorders are related to PTH?
The parathyroid glands produce parathyroid hormone (PTH), which raises blood calcium by stimulating calcium release from bones and absorption from the intestines. Disorders include:
• Tetany: Low calcium due to insufficient PTH.
• Hyperparathyroidism: Excess PTH, leading to brittle bones.
How does the pancreas function as both an endocrine and exocrine gland?
The pancreas functions as an exocrine gland by secreting digestive enzymes into the small intestine and as an endocrine gland by producing insulin and glucagon to regulate blood glucose.
What are the roles of insulin and glucagon, and what disorders result from their dysregulation?
• Insulin (from beta cells) lowers blood glucose by increasing glucose uptake by cells.
• Glucagon (from alpha cells) raises blood glucose by breaking down glycogen in the liver.
Disorders:
• Diabetes Mellitus Type 1: Insulin deficiency.
• Diabetes Mellitus Type 2: Insulin resistance.
What are the functions of the adrenal medulla and cortex, and what disorders are associated with the adrenal glands?
• Adrenal Medulla: Produces epinephrine and norepinephrine, triggering the “fight or flight” response.
• Adrenal Cortex: Produces cortisol (raises blood glucose) and aldosterone (regulates sodium and water balance).
Disorders:
• Addison’s Disease: Low cortisol and aldosterone levels, leading to fatigue, low blood pressure, and weight loss.
What is the role of the thymus gland?
The thymus gland produces thymosin, which aids in the development of T-cells, an essential part of the immune system.
Describe an example of a positive feedback loop in the endocrine system.
During childbirth, oxytocin causes uterine contractions, which stimulate more oxytocin release, intensifying contractions.
