Hormonal communication Flashcards
How endocrine glands work, examples
Secrete chemicals directly into the blood stream e.g. adrenal glands, pancreas
How exocrine glands work, examples
Secrete chemicals through ducts into organs or the surface of the body e.g. salivary glands
Features of steroid hormones
- lipid soluble (pass through membrane)
- bind to steroid hormone receptors to form hormone receptor complex, which acts as a transcription factor
Features of non-steroid hormones
- hydrophilic (can’t pass through membrane)
- bind to receptors on cell surface membrane, triggering a cascade reaction mediated by second messengers
Where is the adrenal cortex and medulla in the kidneys
- Cortex= outer
- Medulla= inner
Main hormones released by the adrenal cortex
- Glucocorticoids (e.g. cortisol)
- Mineralocorticoids (e.g. aldosterone)
- Androgens (e.g. oestrogen, testosterone)
Main hormones released by adrenal medulla
- adrenaline
- noradrenaline
Role of the Pancreas as an exocrine gland
Produces digestive enzymes e.g. amylase, protease, lipase, which are secreted into ducts and then released into the small intestine
What are islets of langerhans
- small regions on endocrine tissue within the exocrine tissue in the pancreas
Role of the pancreas as an endocrine gland
Produces insulin and glucagon, and releases them directly into the blood stream
Where in the pancreas are insulin and glucagon produced and secreted
- in the islets of Langerhans
- Alpha cells= Glucagon
- Beta cells= Insulin
Ways to increase blood glucose concentration
- diet
- glycogenolysis
- gluconeogenesis
What is glycogenolysis
- glycogen stored in the liver and muscle cells is broken into glucose which is released into the blood stream
What is gluconeogenesis
- production of glucose from non-carb sources (e.g. lipids and amino acids) which is then released into the blood stream
Ways to decrease blood glucose concentration
- respiration
- glycogenesis
What is glycogenesis
- production of glycogen
- excess glucose is converted to glycogen which is stored in the liver
How insulin affects cells
- binds to receptors, causing a change in the tertiary structure of glucose transport protein channels
- channels open, allowing glucose to enter the cell
Ways that insulin lowers blood glucose concentration
- Increases the rate of absorption of glucose by cells
- increases cell respiratory rate
- increases rate of glycogenesis
- increase rate of glucose => fat conversion
- inhibits release of glucagon from alpha cells
How is insulin secretion negative feedback
- as glucose concentration returns to normal, Beta cells detect the change and reduce insulin scretion
How glucagon affects low glucose concentrations
- liver and fat cells have glucagon receptors, only cells that respond to glucagon
- causes them to release glucose
Ways glucagon raises blood glucose concentration
- increased glycogenolysis
- reduce amount if glucose absorbed by liver cells
- increased gluconeogenesis
How is glucagon system an example of negative feedback
- as the glucose concentration returns to normal, alpha cells detect and reduce secretion of glucagon
What is the interaction between insulin and glucagon
- antagonistic hormones
- self- regulating system
How insulin is secreted
- When blood glucose concentration rises, glucose enters cells by a glucose transporter
- Glucose is metabolised inside the mitochondria, results in production of ATP
- ATP binds to potassium channels, causes them to close
- Potassium ions can no longer diffuse out the cell, the potential difference of the cell reduces to -30mV, depolarisation occurs
- depolarisation causes voltage-gated calcium channels to open
- calcium ions enter through the channels into the cell, causing secretory vessels to release insulin by exocytosis
Type 1 diabetes
- B cells in IOL don’t produce sufficient/any insulin
- usually begins in childhood
Type 2 diabetes
- B cells don’t produce enough insulin, or the body doesn’t respond to insulin properly, often as glycoprotein insulin receptor doesn’t work properly
- often result of excessive body weight, lack of activity, overeating of carbs
Treatment of type 1 diabetes
- insulin injections
Treatment of type 2 diabetes
- Regulate carb intake
- drugs that e.g. stimulate insulin production, slow the rate the body absorbs glucose
- sometimes insulin injections
Medically produced insulin
- originally obtained from cows/pigs- risk of allergens, expensive, unethical
- now made by genetically modified bacteria= mass production, cheaper, overcome ethics, less risk of rejection
How stem cells can be used to treat diabetes
- totipotent cells can differentiate into B cells to restore insulin production
- stem cells likely to be taken from embryos
Strengths and weaknesses of stem cells for diabtetes
Strengths:
- unlimited source
- less risk of rejection
- no longer have to inject/take treatment
Weaknesses:
- potential risk of induced tumours
- ethics with embryonic stem cells
