Hormonal Communication Flashcards
What is the pathway of hormonal communication?
Stimulus -> Receptors -> hormone -> effectors -> response
What is an endocrine gland?
It is a group of specialised cells that secrete hormones DIRECTLY into the bloodstream
Eg. Adrenal gland, pituitary gland
What is an exocrine gland?
It has a duct through which chemicals are released
Eg. Bile duct, sweat glands, pancreas
Effects of steroid hormones on the cell:
Pass through lipid component of the cell as they are hydrophobic
They then bind to steroid hormone receptors to form a hormone-receptor complex which attaches to DNA and acts as a T.F
These receptors can be found in the cytoplasm or the nucleus
Effect of non-steroid hormones on the cell:
Can’t pass through cell membrane as they’re hydrophilic
Binds to specific receptors in the surface of the target cell’s membrane
They activate an enzyme which causes the release of a second messenger (cAMP).
This triggers a cascade of enzyme-controlled chemical reactions
What is the method of transmission in the endocrine system?
Through the bloodstream
What is the speed of transmission in the endocrine system?
Slow
What is the length of effect in the endocrine system?
Long - until hormone is broken down
What are the 2 major roles of the pancreas?
Synthesise digestive enzymes
Controls blood glucose levels
What are the 3 most important digestive enzymes produced by the pancreas?
Amylases
Proteases
Lipases
What is the exocrine tissue in the pancreas?
The acini.
Each acini has a central duct into which digestive enzymes are secreted. The ducts join up the main pancreatic duct which is released into the small intestine.
What is the endocrine tissue in the pancreas?
The Islet of Langerhans.
Each Islet of Langerhans is the supported with a capillary network. Hormones are secreted directly into the blood via these capillaries.
Alpha and beta cells are found here
Which two cells are found in the islet of langerhans and what does each type of cell produce?
Alpha cells - produce glucagon
Beta cells - produce insulin
What concentration is glucose normally maintained at in the blood?
90mg per 100cm3
What is glycogenolysis?
Glycogen is split into glucose
Blood glucose conc. increases as a result
What is gluconeogenesis?
New glucose molecules are made from non-carbohydrate sources
Eg. Glycerol and amino acids
What is glycogenesis?
Glucose is converted to glycogen
Glucose conc. falls
In which ways is blood glucose conc. maintained?
Respiration
Exercise
Glycogenesis
What type of hormones are insulin and glucagon?
They are Antagonistic hormones which means they work against each other
What type of feedback is used to regulate blood glucose conc. ?
Negative feedback
What makes up the adrenal glands?
The medulla (inner part) and the cortex (outer part)
What two types of stimuli trigger hormone secretion?
The arrival of an electrical impulse
Changes in concentration
What are the 3 types of hormones produced in the adrenal cortex?
Glucocorticoids
Mineralocorticoids
Androgens
What do glucocorticoids do and name and example?
Eg. Cortisol
They help the metabolism of carbohydrates and fats in the liver, stimulating the breakdown of proteins and fats into glucose.
Cortisol is released in response to stress as a result of low blood glucose
What are the functions of mineralocorticoids and name an example?
Eg. Aldosterone
Maintains blood pressure by controlling sodium & potassium concentrations in the blood by acting on cells in the distal convoluted tubule and collecting duct.
Causes increased reabsorption of Na,
Decreased reabsorption of K and increases water retention
What are the functions of androgens?
They regulate secondary sexual characteristics (steroid-based)
Important in females after menopause
What two hormones does the adrenal medulla release?
Adrenaline and noradrenaline
What are the effects of adrenaline?
(Non-steroid)
Increases heart rate, quickly sending blood to brain and muscles. Rapidly increases glucose conc. by converting glycogen to glucose in the liver
What is the role of noradrenaline?
Works with adrenaline in response to stress
widens airways, widens pupils and vasoconstriction of blood vessels to non-essential organs
Why may blood glucose conc. increase?
Diet - eating carbohydrate rich foods
Glycogenolysis - glycogen is split into glucose
Gluconeogenesis - new glucose molecules are made from non-carbohydrate sources eg. Glycerol
How may blood glucose conc. decrease?
Respiration - some glucose is used
Exercise - more glucose is needed to release energy for muscle contraction
Glycogenesis - glucogen —> glycogen
What type of hormones are insulin and glucagon?
They are antagonistic hormones meaning the work against each other
What type of feedback is used to regulate blood glucose conc. ?
Negative feedback
How is insulin secretion controlled when blood glucose conc. is low?
When blood glucose conc. is low then potassium ion channels remain open and calcium channels are closed
Potassium ions leave the cell whilst calcium ions are unable to enter
Cell has a potential difference of -70mV
What cells detect when blood glucose conc. is too high?
Beta cells in the islet of Langerhans of the pancreas produce insulin and release it into the bloodstream
What happens when blood glucose conc. is too high?
1) Glucose molecules move into the beta cell via a glucose transporter in the cell membrane
2) glucose is metabolised in the mitochondria, producing ATP
3) this excess ATP causes potassium ion channels to close (they are phosphorylated).
4) this causes a change in p.d across the membrane -70mV to -30mV causing depolarisation
5) this depolarisation causes calcium ion channels to open and calcium ions begin to diffusing into the cell
6) this increase in calcium ions stimulate (secretory) vesicles containing insulin to fuse with the cell membrane
7) insulin is then released by exocytosis into the bloodstream
What is the action of insulin?
1) insulin binds to receptor molecules on the surface of body cells. This increases the rate of glucose absorption - especially in liver and muscle cells
2) insulin stimulates an increase in glycogenesis (glucose —> glycogen) and glucose conversion to fat.
3) the effects of insulin cause blood glucose conc. to fall
What is diabetes?
An inability to control blood glucose concentration
What are some symptoms of diabetes?
Excessive thirst, blurred vision, high blood sugar
What is type 1 diabetes?
Genetic
Patients unable to produce insulin due to faulty beta cells.
Autoimmune response that normally develops in childhood
What is type 2 diabetes?
Caused by Lifestyle
Patients can produce insulin but may not properly respond to it or are unable to produce enough.
Often malfunctions on insulin receptors.
Symptoms are similar to type 1 but develop slower and are less severe. Risk increases with age
What are the consequences of an insufficient quantity of insulin?
Excess glucose isn’t removed quickly
No glycogen store
Hypoglycaemia as glucose conc. in cells are low
What are the risk factors for type 2 diabetes?
Obesity
High sugar diet
Sedentary lifestyle
Family history
Asian or Afro-Caribbean heritage
Where are adult stem cells usually sourced from?
Bone marrow and placenta
Why is insulin produced by genetically engineered bacteria and not from pigs?
Less chance of rejection
Lower chance of infection
Cheaper to manufacture than extract
Less ethical/moral objections
What is negative feedback?
Negative feedback is when any deviation from the normal values are restored back to their original, optimal level
