Endocrine I

Flashcard 1

• Front: What is homeostasis?

• Back: Homeostasis is the conceptual framework for the study & understanding of physiology. It describes the relative stability of the internal environment. Our internal environment remains remarkably constant despite changes in the external milieu, providing stable conditions for cells in the body.

Flashcard 2

• Front: Who coined the term "homeostasis"?

• Back: Walter Cannon coined the term "homeostasis".

Flashcard 3

• Front: What are the key components of homeostatic control systems?

• Back: The key components of homeostatic control systems include a sensor that constantly monitors, an integrating centre that coordinates, and a response system that changes.

Flashcard 4

• Front: What is a negative feedback loop in the context of homeostasis?

• Back: Most homeostatic systems operate in a negative feedback manner to return a physiological variable to its normal range after a shift outside of that range.

Flashcard 5

• Front: Name some major regulatory systems in the body.

• Back: Major regulatory systems include the skin, cardiovascular, renal, digestive, respiratory, and musculo-skeletal systems.

Flashcard 6

• Front: What are some regulated factors in the body that are maintained through homeostasis?

• Back: Regulated factors include water, electrolytes/pH, nitrogenous compounds, oxygen, carbon dioxide, temperature, and toxicants.

Flashcard 7

• Front: How is homeostasis largely maintained?

• Back: Homeostasis is maintained largely in part by the endocrine system.

Flashcard 8

• Front: What are some examples of endocrine dysfunctions?

• Back: Examples of endocrine dysfunctions include hyper-function (too much hormone), hypo-function (too little hormone), and resistance (too little effect).

Flashcard 9

• Front: Define the endocrine system.

• Back: The endocrine system is involved in the study of hormones & the actions of hormones and how endocrine glands regulate the physiology & behaviour of animals.

Flashcard 10

• Front: What is an endocrine gland?

• Back: An endocrine gland is a tissue which releases (secretes) a substance into the blood stream; this substance then travels via the blood to influence a target cell.

Flashcard 11

• Front: Briefly describe the classic Minkowski experiment.

• Back: The classic Minkowski experiment (1889) involved surgically removing the pancreas in a dog, which caused the dog to develop symptoms of diabetes. Implanting pieces of the pancreas under the skin prevented these symptoms.

Flashcard 12

• Front: Briefly describe the Banting & Best experiment.

• Back: Banting & Best (1921) identified an antidiabetic substance in pancreatic extracts. Injecting these extracts prevented symptoms of diabetes, such as elevated blood glucose.

Flashcard 13

• Front: What is insulin and where is it produced?

• Back: Insulin is a peptide hormone produced by beta cells of the pancreas.

Flashcard 14

• Front: What is the main function of insulin?

• Back: Insulin promotes absorption of glucose from blood to skeletal muscle & fat tissue.

Flashcard 15

• Front: What are the main chemical categories of hormones mentioned in the source?

• Back: The main chemical categories of hormones mentioned are proteins & polypeptides, steroids (cholesterol derivatives), glycoproteins, and amines (catecholamines or thyroid).

Flashcard 16

• Front: What are the three levels of hormone effect?

• Back: The three levels of hormone effect are autocrine, paracrine, and endocrine.

Flashcard 17

• Front: Describe the mode of secretion for peptide hormones.

• Back: Peptide hormones are synthesized in advance, stored in secretory vesicles, and released from the cell via exocytosis. They are dissolved in plasma for transport in the blood and have a short half-life. Insulin is an example.

Flashcard 18

• Front: Describe the mode of secretion for steroid hormones.

• Back: Steroid hormones are synthesized on demand, have no storage in vesicles, and are released from the cell via diffusion. They are bound to carrier proteins for transport in blood and have a long half-life. Estrogen/androgen are examples.

Flashcard 19

• Front: Describe the mode of secretion for thyroid hormones.

• Back: Thyroid hormones (amine category) are synthesized in advance, stored in secretory vesicles, and released from the cell via exocytosis. They are bound to carrier proteins for transport in blood and have a long half-life. Thyroxine (T4) is an example.

Flashcard 20

• Front: Describe the mode of secretion for catecholamines.

• Back: Catecholamines (amine category) are synthesized in advance, stored in secretory vesicles, and released from the cell via exocytosis. They are dissolved in plasma for transport in blood and have a short half-life. Epinephrine/norepinephrine are examples.

Flashcard 21

• Front: What is a key characteristic of hormone binding to receptors?

• Back: Hormone binding to receptors in target cells shows very high specificity for a particular hormone. There is also a continuous turn-over of the receptor-hormone complex.

Flashcard 22

• Front: Where are receptors for most hormones located?

• Back: Receptors for most hormones are found in the plasma membrane of target cells.

Flashcard 23

• Front: Where are receptors for steroid and thyroid hormones located?

• Back: Receptors for steroid & thyroid hormones are inside the target cells.

Flashcard 24

• Front: Describe the general mechanism of transmembrane receptors for peptide hormones.

• Back: When a peptide hormone binds to the extracellular domain of a transmembrane receptor, it activates one or more cytoplasmic signalling pathways, often involving phosphorylation & enzyme activation. Some pathways lead to DNA/mRNA/protein responses, while others have local effects.

Flashcard 25

• Front: Briefly outline the adenylate cyclase pathway.

• Back: 1. Hormone + receptor, G-proteins dissociate. 2. α-subunit activates AC. 3. AC catalyzes the production of cAMP. 4. cAMP removes the regulatory unit from PKA. 5. PKA activates other molecules, leading to a hormonal response.

Flashcard 26

• Front: Give an example of a hormone that uses the adenylate cyclase pathway.

• Back: Epinephrine binding to the β–adrenergic receptor on a liver cell is an example that uses the adenylate cyclase pathway.

Flashcard 27

• Front: What is the role of G protein-coupled receptors?

• Back: G protein-coupled receptors are proteins that reach through cell walls and are crucial for unravelling the complex network of signalling between cells, allowing cells to sense their environments.

Flashcard 28

• Front: Briefly outline the phospholipase C-Ca2+ pathway.

• Back: 1. Hormone + receptor, G-proteins dissociate. 2. Activates PLC. 3. PLC causes breakdown of a membrane phospholipid to IP3. 4. IP3 binds to the endoplasmic reticulum. 5. Release of stored Ca2+ into the cytoplasm. 6. Ca2+ activates other molecules, leading to a hormonal response.

Flashcard 29

• Front: How do alpha-adrenergic receptors and beta-adrenergic receptors differ in their signaling pathways?

• Back: Alpha-adrenergic receptors activate phospholipase C (via Gq), while beta-adrenergic receptors activate adenylate cyclase (via Gs).

Flashcard 30

• Front: Describe the mechanism of action for steroid hormone receptors.

• Back: 1. Steroid hormone (bound to a plasma carrier protein) moves across the plasma membrane and binds to a receptor in the cell cytoplasm. 2. The hormone-receptor complex translocates to the nucleus and binds to DNA, acting as a transcription factor. 3. This stimulates gene transcription, leading to protein production and a response.

Flashcard 31

• Front: Describe the mechanism of action for thyroid hormone receptors.

• Back: 1. Thyroxine (T4) binds to a carrier protein. 2. T4 is converted to T3 (triiodothyronine). 3. T3 uses binding proteins to enter the nucleus. 4. The hormone-receptor complex binds to DNA. 5. This leads to new mRNA, protein synthesis, and a response.