5.1.4 Hormonal communication Flashcards
What are the main differences between neuronal and hormonal communication?
- Hormonal transmission is relatively slower than nervous transmission
- Hormones travel to all parts of body (only target cells respond), nerve impulses travel to specific parts
- Response to hormones is widespread, response to nerve impulse is localised
- Hormonal effect is long-lasting, nerve impulse is short-lived
- Hormonal effect may be permanent, nervous effect is temporary and reversible
State the hormone(s), and their functions, produced by the pituitary gland
- Growth Hormone - controls muscle and bone growth
- ADH - increases water re-absorption
- Gonadotrophins - controls development of ovaries and testes
State the hormone(s), and their functions, produced by the thyroid gland
Thyroxine - controls metabolic rate and promotes growth
State the hormone(s), and their functions, produced by the pineal gland
Melatonin - helps establish circadian rhythms
State the hormone(s), and their functions, produced by the thymus
Thymosin - promotes production and maturation of WBCs
State the hormone(s), and their functions, produced by the pancreas
Insulin - glucose to glycogen
Glucagon - glycogen to glucose
State the hormone(s), and their functions, produced by the ovaries
Oestrogen - controls ovulation and sexual characteristics
Progesterone - prepares uterus lining for embryo
State the hormone(s), and their functions, produced by the testes
Testosterone - controls sperm production and sexual characteristics
What are steroid hormones?
Lipid-soluble hormones that pass through the membrane and bind to receptor in cytoplasm. Hormone-receptor complex acts as transcription factor - binds to receptor on DNA
e.g. sex hormones and hormones secreted from adrenal cortex
What are non-steroid hormones?
Hydrophilic hormones that can’t pass through so bind to receptors on cell membrane. Uses second messenger model to trigger response
e.g. adrenaline
Describe the position and function of the adrenal cortex
Outer region of adrenal glands
Produces vital hormones
Describe the position and function of the adrenal medulla
Inner region of adrenal glands
Produces non-essential hormones
State which hormones are produced by the adrenal cortex. What is their function?
- Glucocorticoids e.g. cortisol - regulate metabolism, blood pressure and cardiovascular function. Corticosterone - regulates immune response
- Mineralocorticoids e.g. aldosterone - maintains salt water conc
- Androgens (male sex hormones) - small impact
State which hormones are produced by the adrenal medulla. What is their function?
- Adrenaline - causes physical response to stress - e.g. increase heart rate and blood glucose conc
- Noradrenaline - works alongside adrenaline
What mechanism controls the production of hormones at the adrenal cortex?
Pituitary gland, which is stimulated by the hypothalamus
What mechanism controls the production of hormones at the adrenal medulla?
Sympathetic NS, which is stimulated by the hypothalamus
Define glycogenolysis
Breakdown of glycogen to glucose
Define gluconeogenesis
Production of glucose from sources other than carbohydrates e.g. fats and amino acids
Define glycogenesis
Production of glycogen from glucose - method of decreasing glucose other than respiration
Describe the process if blood glucose levels rise
- Beta cells of pancreas detect change
- Insulin secreted
- Receptors of liver and muscle cells (in particular) uptake insulin
- Glycogenesis occurs, Glucose to fat, increased respiration, cells absorb glucose
- Returns to normal
Describe the process if blood glucose levels fall
- Alpha cells of pancreas detect change
- Glucagon secreted
- Liver cells uptake glucagon
- Glycogenolysis occurs, amino acids to glucose, glucose into blood from intestines
- Returns to normal
How does insulin trigger the uptake of glucose?
All cells have insulin receptors, except RBCs.
Triggers opening of more glucose co-transporter proteins (changes tertiary)
How does glucagon trigger glycogenolysis?
Only liver and fat cells have glucagon receptors - activates enzyme
How is the negative feedback mechanism controlled?
Alpha and beta cells reduce the secretion of their hormones once the glucose conc returns to normal
Describe the secretion of insulin by beta cells
- Higher influx of glucose through co-transporter protein (GLUT-2)
- Rapid breakdown of glucose produces ATP
- ATP binds to Katp channels - close
- Depolarisation - K+ can’t exit
- Voltage-gated Ca2+ channels open
- Vesicles fuse with cell membranes - insulin secreted
What is the difference in the cause of Type 1 and Type 2 diabetes?
Type 1 - insulin dependent- pancreas doesn’t produce any insulin
Type 2 insulin resistant - cells non-responsive to insulin or beta cells don’t produce enough insulin
What are some symptoms of diabetes?
- Excessive urination
- High blood glucose conc
- Weight loss
- Blurred vision
- Excessive hunger/thirst
- Glucose in urine
What are the differences in treating Type 1 and Type 2 diabetes?
Type 1 - Insulin injections and regular blood tests
Type 2 - Regulate diet and exercise, drugs to stimulate insulin production/slow glucose absorption if necessary
What is hypoglycaemia?
Low blood glucose concentration
What is hyperglycaemia?
High blood glucose concentration
How was insulin previously produced? What were the issues?
From the pancreas cells of pigs and cows. Issues of ‘allergic reactions’ and difficulty of access
How is insulin presently produced? What are the benefits?
Genetically modified bacteria - less likely to cause ‘allergic reactions’, high quantity production, cheaper costs, no ethical issues
What are the issues with having a pancreas transplant?
- Demand outweighs availability
2. Health risk - immunosuppressant drugs
What are the issues with having beta cells transplanted?
- Fewer than 8% have been successful
2. Immunosuppressant drugs increase metabolic demand of insulin - exhausts natural stock
What are the potential uses of stem cells for type 1 diabetes?
Results due to loss of a single cell type ( beta cells) - totipotent cells can differentiate into any cell type. Best stem cells are embryonic (wasted anyway - small number can treat many patients. Alternative would be from an umbilical cord
What are the advantages of stem cell treatment?
- Donor availability isn’t an issue - unlimited source
- No more injections
- Reduced likelihood of rejection
What is a disadvantage of stem cell treatment?
Implanting stem cells may promote growth of tumour - more research to be done on controlling growth and differentiation
Describe the difference of the results of a glucose tolerance test for a diabetic and non-diabetic person
Diabetic - Higher starting blood glucose conc, and slower return to normal level - no insulin response
Non-diabetic - Increases less than diabetic - Fast return to normal level - insulin response
