5.1.4 - Hormonal Communication Flashcards
What is an endocrine gland?
A group of cells that are specialised to secrete hormones
What does the pineal gland produce?
Melatonin, which affects reproductive development and daily cycles
What does the pituitary gland produce?
Growth hormone, ADH, and gonadotrophins, which control development of ovaries and testes
What does the thymus release?
Thymosin, which promotes production and maturation of white blood cells
What does the thyroid gland produce?
Thyroxine, which controls the rate of metabolism and the rate that glucose is used up in respiration, and promotes growth
What does the adrenal gland produce?
Adrenaline, cortisol, etc
What does the pancreas produce?
Insulin and glucagon
What do the testes produce?
Testosterone, which controls sperm production and secondary sexual characteristics
What does the ovary produce?
Oestrogen, which controls ovulation and sexual characteristics, and progesterone
How do steroid hormones act?
They pass through the lipid component of the plasma membrane and bind to steroid hormone receptors. The complex formed acts as a transcription factor which facilitates or inhibits transcription of a gene
How do non-steroid hormones act?
They bind to specific receptors on the plasma membrane of the target cell. This triggers a cascade reaction mediated by secondary messengers, like cAMP
What is the adrenal cortex?
Outer region of the adrenal gland that produces hormones that are vital to life, e.g. cortisol and aldosterone
What is the adrenal medulla?
Inner region of the adrenal gland which produces non-essential hormones, e.g. adrenaline
What are the three main types of hormones produced by the adrenal cortex?
Glucocorticoids, mineralocorticoids, and androgens
What are glucocorticoids?
Hormones that regulate metabolism by controlling how the body converts fats, proteins, and carbs to energy. They also regulate blood pressure and cardiovascular function. An example is cortisol
What are mineralocorticoids?
Hormones that help control blood pressure by maintaining the balance between salt and water concentrations in the blood and body fluids. An example is aldosterone
What are androgens?
Male and female sex hormones
What are secreted by the adrenal medulla?
Adrenaline and noradrenaline
What is adrenaline?
A hormone that increases the heart rate sending blood quickly to the muscles and brain. It also raises blood glucose concentration levels by converting glycogen into glucose in the liver
What is noradrenaline?
A hormone that works with adrenaline in response to stress, producing effects such as an increased heart rate, widening of pupils, widening of air passages in the lungs, and the narrowing of blood vessels in non-essential organs
What are the two main functions of the pancreas?
An exocrine gland and an endocrine gland
Describe the function of the pancreas as an exocrine gland
Most of the pancreas is made up exocrine glandular tissue (acinar cells). The pancreas produces amylases, proteases, and lipases
Describe the function of the pancreas as an endocrine gland
Islets of Langerhans produce insulin and glucagon. Alpha cells produce glucagon while beta cells produce insulin
What can increase the blood glucose concentration?
Diet, glycogenolysis, gluconeogenesis
What is glycogenolysis?
When glycogen stored in the liver and muscle cells is broken down into glucose
What is gluconeogenesis?
When glucose is produced from non-carbohydrate sources, e.g. glycerol and amino acids
What can decrease blood glucose concentration?
Respiration and glycogenesis
What is glycogenesis?
When glycogen is produced from glucose
How does insulin lower blood glucose concentration?
- Increases rate of absorption of glucose by cells
- Increases respiratory rate of cells
- Increases rate of glycogenesis
- Increases the rate of glucose to fat conversion
- Inhibits the release of glucagon
How does glucagon raise blood glucose concentration?
- Glycogenolysis
- Reduces the amount of glucose absorbed by liver cells
- Increases gluconeogenesis
Where does insulin act and why?
All over the body because all body cells (bar RBCs) have insulin receptors
Where does glucagon act and why?
Liver and fat cells, as these are the only cells with the glucagon receptors
Describe the mechanism of insulin release by the beta cells
Glucose conc rises, so glucose enters the cell via a glucose transporter. Glucose metabolised, forming ATP. ATP binds to ATP-sensitive potassium channels, which close. Membrane potential increases to -30mV, so Ca+2 ions enter via voltage gated channels. Entrance of Ca+2 causes secretory vesicles to undergo exocytosis, releasing insulin
What are the two main types of diabetes mellitus?
Type 1 and Type 2
Describe Type 1 Diabetes mellitus
Patients are unable to produce insulin. Disease cannot be prevented or cured. Autoimmune disease
Describe type 2 diabetes mellitus
Patients cannot effectively use insulin. Either due to the beta cells not producing enough insulin or the body cells not responding to insulin
What treatment is available for type 1 diabetes?
Controlled by regular injections of insulin and is said to be insulin-dependent.
What treatment is available for type 2 diabetes?
The main form of treatment is improving diet and exercise, but there are drugs that exist that stimulate insulin production, and insulin injections can be taken
How was insulin originally obtained?
From the pancreas of cows and pigs, but this was difficult and expensive, and insulin was sometimes rejected. Also ethical and religious concerns exist
How is insulin made now?
Using genetically modified bacteria
What are the advantages of using stem cells to give patients beta cells?
Donor availability is not an issue, likelihood of rejection is reduced, and people no longer have to inject themselves with insulin.
